Forum Übersicht - RE: Sony Zeiss Planar T* 1,4/50mm ZA SSM (SAL-50F14Z) - 4

ZITAT(aidualk @ 2013-02-26, 8:08) Wieso Äpfel mit Birnen? Das Zeiss 24/2 SSM, mit dem ich jetzt seit über 2 Jahren sehr zufrieden bin, ist für mich der Maßstab, wenn ich bereit sein sollte für ein Objektiv deutlich mehr als 1000 EUR auszugeben...[/quote]
Zwischen f1.4 und f2 ist aber schon noch ein gewisser Unterschied. Ich hab auch das Zeiss 2/24 und gehe schon mal fest davon aus, dass das 1.4 50mm SSM abgeblendet auf f2 mindestens auf dem Niveau des 2/24mm liegt, am Rand sollte es sogar deutlich besser sein. Aber warten wir es ab und trinken noch eine Runde Tee.

BG Hans

Sollte ein 50er Planar nicht "einfacher" zu rechnen/bauen sein als ein Distagon? Und sollte dadurch nicht auch noch ein wenig "rauszuholen" sein?

ZITAT(Hans-J. @ 2013-02-25, 22:42) ZITAT(aidualk @ 2013-02-25, 22:12) Das Niveau des 24/2 Zeiss scheint das neue 50er nicht zu erreichen oder gar zu übertreffen. Unter 90% bei 10lp/mm ist schon recht flau bei Offenblende. Kann ich auch mein uraltes 50er behalten, das ist bei Offenblende auch flau.[/quote]
Vergleich doch mal lieber Äpfel mit Äpfeln: http://lenses.zeiss.com/content/dam/Photog...planart1450.pdf.
[/quote]
Das ist schon richtig, allerdings können wir die MTF-Diagramme von Zeiss und Sony leider nicht direkt miteinander vergleichen.

http://www.mi-fo.de/forum/index.php?showto...st&p=272963
http://www.mi-fo.de/forum/viewtopic.php?t=22446

Bedingt vergleichbar immerhin SAL-50F14Z und SAL-50F14.

Viele Grüße,

Matthias

ZITAT(aidualk @ 2013-02-26, 8:35) Sollte ein 50er Planar nicht "einfacher" zu rechnen/bauen sein als ein Distagon? Und sollte dadurch nicht auch noch ein wenig "rauszuholen" sein?[/quote]

Jein.

Die sphärischen Aberrationen - um ein Beispiel zu geben - nehmen mit der dritten Potenz der (absoluten) Öffnung zu; der Übergang von f2 zu f1.4 fordert da schon seinen Tribut. Umgekehrt nehmen natürlich die winkelabhängigen Bildfehler mit grösserem Winkel überproportional zu.

Interessant dürfte auch sein, ob das ZA 1.4/50mm die Verzeichnung gut korrigiert - Objektive wie das Canon FD/EF 1.4/50mm und die Min MC/MD/AF 1.4/50er sind da diesbezüglich keine "Leuchten".

Interessant an den MTFs finde ich, dass das ZA 1.4/50mm bis in die extremen Bildecken relativ gut korrigiert ist (besser als zB das exorbitant teure Leica M 1.4/50mm ASPH). Dafür hat man wohl die Korrektion im Bildzentrum nicht auf äusserste Spitze getrieben. Wenn Du das ZA 2/24mm (bzw. seine MTF-Kurven) anschaust, so wird sofort deutlich, dass die äussersten Bildecken extrem schlecht kommen - genau hier hat man (sinnvollerweise) Abstriche gemacht, um das 2/24mm nicht allzu gross/schwer/teuer werden zu lassen ...

Schlussendlich sind für mich die Bildresultate und das Handling wichtig. Ich schliesse nicht aus, dass mir das alte, leichte, "schlechte" MinAF 1.4/50mm mit seiner bei f1.4 recht "weichen", aber detailreichen Auslegung genausogut (oder besser) zusagt als das neue ZA 1.4/50mm. Genau aus analogem Grund schätze ich auch das adaptierte Canon FD 2/135mm an der A900 so sehr ...

Gr Steve

Ich frage mich wie die Preise für die Zeiss-Objektive und im speziellen für das SAL50F14Z zustande kommen.

Wenn man momentan nach den "Straßenpreisen" schaut, sind zwischen dem normalen SAL50F14 und dem SAL50F14Z ca. 1100 ¤ Preisdifferenz. Wobei man sagen muss, dass das Zeiss Objektiv noch nicht lieferbar ist.
Ich habe ja keinen großen Einblick in die Objektiv-Herstellung, aber soll das Zeiss Objektiv wirklich 1100¤ mehr in der Herstellung kosten? Klar es hat SSM, eine höherwertige Optik und damit wohl auch geringere Fertigungstoleranzen. Und natürlich kostet auch das Zeiss Logo. Wie seht ihr das? Ich glaube nicht an diese Preisdifferenz in der Herstellung und Entwicklung und halte das Objektiv daher für überteuert.

Ich würde für ein gutes 50er mit SSM durchaus auch mehr bezahlen wie für das derzeitige 50 1.4, aber nicht soviel mehr.

Makros ausgenommen, hat Sony ja jetzt drei 50er im Programm.
Das günstige 1.8 DT hat ja seine Berechtigung in der Reihe der preiswerten Objektive.

Wird Sony das 50 1.4 neben dem Zeiss weiter herstellen?
Wenn sie es einstellen würde da preislich eine sehr kräftige Lücke klaffen.

Was ich bei Sony vermisse ist so eine Art Objektiv Roadmap. Haben andere Herstelle eigentlich so etwas?

Hier gibt es ein paar Handling-Fotos eines SAL-50F14Z Vorserienmodells:

http://www.thephoblographer.com/2013/02/28...4-sony-a-mount/

Der Text ist allerdings schwach und zum Teil sind die getroffenen Aussagen schlichtweg falsch...

Interessieren würden mich Beispielbilder, die mit dem SAL-50F14Z aufgenommen wurden (möglichst unbearbeitet). Hat jemand schon irgendwo welche entdeckt?

Viele Grüße,

Matthias

Dieses Video eines Vortrags des Sonys Chefobjektivdesigners Motoyuki Ohtake,
http://www.youtube.com/watch?feature=playe...p;v=okl5mwkZ_7s
das von Gary Friedman eingestellt wurde, erläutert die Konstruktion des 70-400G II und des Sony Zeiss 1,4/50. Die ersten 3 Minuten kann man überspringen.

Ich hatte am vergangenen Wochenende kurzzeitig das Sony Zeiss 1,4/50mm zum Testen. Ich habe eine Blendenreihe eines weiter entfernten Motivs aufgenommen und einen Bokehtest bei verschiedenen Blenden gemacht. Mir fehlt die Zeit, das jetzt aufzubereiten (ich habe die Bilder noch nichteinmal von der Kamera heruntergeladen), aber wenn irgendjemand dringenden Bedarf für solche Bikder haben sollte, kann er sich gern melden.

Nikon reiht sich jetzt mit dem AF-S Nikkor 1,4/58mm G auch in die Riege der Hersteller von "Hochleistungs"-Vollformatobjektiven mit Normalbrennweite ein:

http://www.photoscala.de/Artikel/AF-S-Nikkor-1458-mm-G

Konstruktion: neun Linsen in sechs Gruppen, davon zwei verkittete Gruppen, zwei asphärische Linsen (vier asphärische Oberflächen?)
Kleinste Blende: 16
Naheinstellgrenze: 58 cm
Maximaler Abbildungsmaßstab: 1:7,7
Filtergewinde: E72
Gewicht: 385 g
Listenpreis: 1720 EUR

Viele Grüße,

Matthias

Test des Sony Zeiss Planar T* 1,4/50mm ZA SSM (SAL-50F14Z) bei Kurt Munger:
http://www.mi-fo.de/forum/viewtopic.php?t=34589

ZITAT(Reisefoto @ 2014-01-07, 18:34) Test des Sony Zeiss Planar T* 1,4/50mm ZA SSM (SAL-50F14Z) bei Kurt Munger:
http://www.mi-fo.de/forum/viewtopic.php?t=34589[/quote]
Falscher Link. Der ist richtig: http://kurtmunger.com/sony_carl_zeiss_50mm_f_1_4id349.html

Ein Patent, in dem in einer Verkörperung das SAL-50F14Z beschrieben wird, ist gefunden:

http://www.google.de/patents/US20140071331?dq=20140071331
http://www.freepatentsonline.com/y2014/0071331.html

Imaging lens and imaging apparatus US 20140071331 A1
ZITATVeröffentlichungsnummer: US20140071331 A1
Publikationstyp: Anmeldung
Anmeldenummer: US 13/958,942
Veröffentlichungsdatum: 2014-03-13
Eingetragen: 2013-08-05
Prioritätsdatum: 2012-09-07
Erfinder: Kouji Katou, Yumiko Uehara, Motoyuki Otake
Ursprünglich Bevollmächtigter: Sony Corporation
Zitat exportieren BiBTeX, EndNote, RefMan
Klassifizierungen (4)
Externe Links: USPTO, USPTO-Zuordnung, Espacenet

Klassifizierungen

US-Klassifikation: 348/345, 359/794
Internationale Klassifikation: G02B9/08
Unternehmensklassifikation: G02B9/08

Summary

There is provided An imaging lens including a first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power that are configured to be arranged sequentially from an object side to an image side. Focus is achieved by fixing the first lens group in an optical axis direction and moving the second lens group from the image side to the object side when a subject distance is changed from infinity to proximity. The first lens group includes an object-side lens group having a negative refractive power and an image-side lens group having a positive refractive power that are configured to be arranged sequentially from the object side to the image side. In an air space of the first lens group, an air space between the object-side lens group and the image-side lens group is set to be maximum.

[attachment=13865:header.png]

Description

BACKGROUND

The present technology relates to a technical field of an imaging lens and an imaging apparatus, and more particularly, to a technical field of an imaging lens which is suitable for, particularly, a single-lens reflex camera or a video camera and in which a rear focus type is used and an imaging apparatus using the imaging lens.

In the past, so-called double Gauss imaging lenses have been suggested considerably as standard lenses (imaging lenses) with large apertures used in imaging apparatuses such as still cameras or video cameras.

In such double Gauss imaging lenses according to the related art, a whole extension type in which the whole lens is extended when a subject distance is changed from infinity to proximity is generally used (for example, see Japanese Unexamined Patent Application Publication No. 2007-333790).

On the other hand, in imaging apparatuses such as single-lens reflex cameras or video cameras, there is a high demand for fast autofocus, and a rear focus type is considerably used to realize fast autofocus (for example, see Japanese Unexamined Patent Application Publication No. 2009-237542).

SUMMARY

In the double Gauss imaging lens disclosed in Japanese Unexamined Patent Application Publication No. 2007-333790, however, correction of aberration at infinity, particularly comatic aberration (comatic flare), is not sufficiently performed and sufficiently high optical performance is not ensured. Further, the whole extension type is used. However, in the whole extension type, a change in performance is considerable when a subject distance is changed to proximity. In particular, a spherical aberration is considerably changed, and thus it may be difficult to realize fast autofocus.

In the imaging apparatus disclosed in Japanese Unexamined Patent Application Publication No. 2009-237542, an amount of movement of a focus lens group is set to be small by strengthening a refractive power of a focus group. However, since the refractive power of the focus group is strengthened, various aberrations at the time of the movement to proximity, particularly, a spherical aberration or field curvature, may be considerably changed, unfortunately.

It is desirable to provide an imaging lens and an imaging apparatus capable of ensuring excellent imaging performance from infinity to proximity while an amount of movement of a focus lens group is set to be small, and thus improving optical performance.

According to an embodiment of the present technology, there is provided an imaging lens including a first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power that are configured to be arranged sequentially from an object side to an image side. Focus is achieved by fixing the first lens group in an optical axis direction and moving the second lens group from the image side to the object side when a subject distance is changed from infinity to proximity. The first lens group includes an object-side lens group having a negative refractive power and an image-side lens group having a positive refractive power that are configured to be arranged sequentially from the object side to the image side. In an air space of the first lens group, an air space between the object-side lens group and the image-side lens group is set to be maximum. A following Condition Expression (1) is satisfied:

−13.0 < f1F / f2 < −4.0,  (1)

where f1F is a focal distance of the object-side lens group at an infinity focus time and f2 is a focal distance of the second lens group at the infinity focus time.

Accordingly, in the imaging lens, the refractive powers of the object-side lens group of the first lens group and the second lens group become suitable.

According to another embodiment of the present technology, it is preferable that a following Condition Expression (2) is satisfied.

As the imaging lens satisfies the foregoing Condition Expression (2), the refractive power of the first lens group becomes suitable. Thus, back focus of the lens system can sufficiently be ensured and the entire length can be shortened.

According to another embodiment of the present technology, it is preferable that the object-side lens group includes a first lens having a positive refractive power and a second lens having a negative refractive power that are configured to be arranged sequentially from the object side to the image side.

The object-side lens group includes the first lens having the positive refractive power and the second lens having the negative refractive power that are configured to be arranged sequentially from the object side to the image side. Thus, an air space between the first and second lens decreases and the degree of curve of a light beam oriented from the first lens to the second lens is suppressed.

According to another embodiment of the present technology, it is preferable that the second lens group includes two pairs of cemented lenses.

The second lens group includes two pairs of cemented lenses. Thus, a high-order spherical aberration is satisfactorily corrected.

According to another embodiment of the present technology, it is preferable that each of the first lens group and the second lens group includes at least one aspheric lens.

Each of the first and second lens groups includes at least one aspheric lens. Thus, correction of a spherical aberration, field curvature, and an off-axis comatic aberration is performed by the aspheric lens.

According to another embodiment of the present technology, it is preferable that when the subject distance is changed from infinity to proximity, the aperture stop and the second lens group are integrally configured and moved from the image side to the object side.

When the subject distance is changed from infinity to proximity, the aperture stop and the second lens group are integrally configured and moved from the image side to the object side. Thus, an amount of peripheral light increases from infinity to proximity, compared to a rear focus type in which an aperture stop is fixed and only the second lens group is moved in the optical axis direction.

According to another embodiment of the present technology, there is provided an imaging apparatus including an imaging lens, and an image sensor that converts an optical image formed by the imaging lens into an electric signal. The imaging lens includes a first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power that are configured to be arranged sequentially from an object side to an image side. Focus is achieved by fixing the first lens group in an optical axis direction and moving the second lens group from the image side to the object side when a subject distance is changed from infinity to proximity. The first lens group includes an object-side lens group having a negative refractive power and an image-side lens group having a positive refractive power that are configured to be arranged sequentially from the object side to the image side. In an air space of the first lens group, an air space between the object-side lens group and the image-side lens group is set to be maximum. A following Condition Expression (1) is satisfied:

−13.0 < f1F / f2 < −4.0,  (1)

where f1F is a focal distance of the object-side lens group at an infinity focus time and f2 is a focal distance of the second lens group at the infinity focus time.

Accordingly, in the imaging lens of the imaging apparatus, the refractive powers of the object-side lens group of the first lens group and the second lens group become suitable.

The imaging lens according to an embodiment of the present technology includes an imaging lens including a first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power that are configured to be arranged sequentially from an object side to an image side. Focus is achieved by fixing the first lens group in an optical axis direction and moving the second lens group from the image side to the object side when a subject distance is changed from infinity to proximity. The first lens group includes an object-side lens group having a negative refractive power and an image-side lens group having a positive refractive power that are configured to be arranged sequentially from the object side to the image side. In an air space of the first lens group, an air space between the object-side lens group and the image-side lens group is set to be maximum. A following Condition Expression (1) is satisfied:

−13.0 < f1F / f2 < −4.0,  (1)

where f1F is a focal distance of the object-side lens group at an infinity focus time and f2 is a focal distance of the second lens group at the infinity focus time.

Accordingly, excellent image-forming performance from infinity to proximity is ensured while an amount of movement of a focus lens group is set to be small when the subject distance is changed from infinity to proximity, and thus optical performance can be achieved.

According to a second embodiment of the present technology, a following Condition Expression (2) is satisfied,

1.8 < f1 / f < 4.5,  (2)

where f1 is a focal distance of the first lens group at the infinity focus time and f is a focal distance of an entire lens system at the infinity focus time.

Accordingly, it is possible to satisfactorily correct a distortion aberration or a spherical aberration, while sufficient back focus is ensured, and reduction in manufacturing sensitivity is achieved.

According to a third embodiment of the present technology, the object-side lens group includes a first lens having a positive refractive power and a second lens having a negative refractive power that are configured to be arranged sequentially from the object side to the image side.

Accordingly, since the air space between the first and second lenses can decrease and the degree of the curve of a light beam oriented from the first lens to the second lens can be suppressed, the sensitivity of the air space between the first and second lenses can be suppressed.

According to a fourth embodiment of the present technology, the second lens group includes two pairs of cemented lenses.

Accordingly, it is possible to satisfactorily correct a high-order spherical aberration and achieve simplicity of the configuration of a lens tube or ease of manufacturing.

According to a fifth embodiment of the present technology, each of the first lens group and the second lens group includes at least one aspheric lens.

Accordingly, it is possible to satisfactorily correct a spherical aberration or field curvature and satisfactorily correct an off-axis comatic aberration.

According to a sixth embodiment of the present technology, when the subject distance is changed from infinity to proximity, the aperture stop and the second lens group are integrally configured and moved from the image side to the object side.

Accordingly, it is possible to ensure a sufficient amount of peripheral light from infinity to proximity, compared to the rear focus type in which an aperture stop is fixed and only the second lens group is moved in the optical axis direction.

According to a seventh embodiment of the present technology, there is provided an imaging apparatus including an imaging lens, and an image sensor that converts an optical image formed by the imaging lens into an electric signal. The imaging lens includes a first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power that are configured to be arranged sequentially from an object side to an image side. Focus is achieved by fixing the first lens group in an optical axis direction and moving the second lens group from the image side to the object side when a subject distance is changed from infinity to proximity. The first lens group includes an object-side lens group having a negative refractive power and an image-side lens group having a positive refractive power that are configured to be arranged sequentially from the object side to the image side. In an air space of the first lens group, an air space between the object-side lens group and the image-side lens group is set to be maximum. A following Condition Expression (1) is satisfied:

−13.0 < f1F / f2 < −4.0,  (1)

where f1F is a focal distance of the object-side lens group at an infinity focus time and f2 is a focal distance of the second lens group at the infinity focus time.

Accordingly, excellent imaging performance from infinity to proximity is ensured while an amount of movement of a focus lens group is set to be small at the time of change in the subject distance from infinity to proximity, and thus optical performance can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS

[attachment=13866:fig_1_1.png]
FIG. 1 is a diagram illustrating an imaging lens and an imaging apparatus together with FIGS. 2 to 15 according to a preferred embodiment of the present technology and is a diagram illustrating the configuration of an imaging lens according to a first embodiment;

[attachment=13867:fig_2.png]
FIG. 2 is a diagram illustrating a spherical aberration, an astigmatism, a distortion aberration, and a lateral aberration in specific numerical values according to the first embodiment;

[attachment=13868:fig_3_2.png]
FIG. 3 is a diagram illustrating the configuration of an imaging lens according to a second embodiment;

[attachment=13869:fig_4.png]
FIG. 4 is a diagram illustrating a spherical aberration, an astigmatism, a distortion aberration, and a lateral aberration in specific numerical values according to the second embodiment;

[attachment=13870:fig_5_3.png]
FIG. 5 is a diagram illustrating the configuration of an imaging lens according to a third embodiment;

[attachment=13871:fig_6.png]
FIG. 6 is a diagram illustrating a spherical aberration, an astigmatism, a distortion aberration, and a lateral aberration in specific numerical values according to the third embodiment;

[attachment=13872:fig_7_4.png]
FIG. 7 is a diagram illustrating the configuration of an imaging lens according to a fourth embodiment;

[attachment=13873:fig_8.png]
FIG. 8 is a diagram illustrating a spherical aberration, an astigmatism, a distortion aberration, and a lateral aberration in specific numerical values according to the fourth embodiment;

[attachment=13874:fig_9_5.png]
FIG. 9 is a diagram illustrating the configuration of an imaging lens according to a fifth embodiment;

[attachment=13875:fig_10.png]
FIG. 10 is a diagram illustrating a spherical aberration, an astigmatism, a distortion aberration, and a lateral aberration in specific numerical values according to the fifth embodiment;

[attachment=13876:fig_11_6.png]
FIG. 11 is a diagram illustrating the configuration of an imaging lens according to a sixth embodiment;

[attachment=13877:fig_12.png]
FIG. 12 is a diagram illustrating a spherical aberration, an astigmatism, a distortion aberration, and a lateral aberration in specific numerical values according to the sixth embodiment;

[attachment=13878:fig_13_7.png]
FIG. 13 is a diagram illustrating the configuration of an imaging lens according to a seventh embodiment;

[attachment=13879:fig_14.png]
FIG. 14 is a diagram illustrating a spherical aberration, an astigmatism, a distortion aberration, and a lateral aberration in specific numerical values according to the seventh embodiment;

[attachment=13880:fig_15.png]
FIG. 15 is a block diagram illustrating an example of an imaging apparatus.

DETAILED DESCRIPTION OF THE EMBODIMENTS

Hereinafter, preferred embodiments of the present technology will be described in detail with reference to the appended drawings. Note that, in this specification and the appended drawings, structural elements that have substantially the same function and structure are denoted with the same reference numerals, and repeated explanation of these structural elements is omitted.

Hereinafter, an imaging lens and an imaging apparatus according to preferred embodiments of the present technology will be described.

Configuration of Imaging Lens

An imaging lens according to an embodiment of the present technology includes a first lens group having a positive refractive power, an aperture stop, and a second lens group having a positive refractive power that are configured to be arranged sequentially from an object side to an image side. Focus is achieved by fixing the first lens group in an optical axis direction and moving the second lens group from the image side to the object side when a subject distance is changed from infinity to proximity.

In the imaging lens according to the embodiment of the present technology, the first lens group includes an object-side lens group having a negative refractive power and an image-side lens group having a positive refractive power that are configured to be arranged sequentially from the object side to the image side. In an air space of the first lens group, an air space between the object-side lens group and the image-side lens group is set to be the maximum.

In the imaging lens according to the embodiment of the present technology, a rear focus type in which the first lens group is fixed in the optical axis direction and the second lens group is moved from the image side to the object side when the subject distance is changed from infinity to proximity is used. Accordingly, the focus lens group (second lens group) can be reduced in weight, and thus fast autofocus can be realized.

Further, in the imaging lens according to the embodiment of the present technology, the following Condition Expression (1) is satisfied:

−13.0 < f1F / f2 < −4.0,  (1)

where f1F is a focal distance of the object-side lens group at an infinity focus time and f2 is a focal distance of the second lens group at the infinity focus time.

The foregoing Condition Expression (1) defines a ratio of the focal distance of the object-side lens group to the focal distance of the second lens group at the infinity focus time.

When the ratio is less than the lower limit of the foregoing Condition Expression (1), the refractive power of the object-side lens group is too weak, and thus it may be difficult to ensure sufficient back focus of the lens system. At this time, to ensure the sufficient back focus, it is necessary to strengthen the refractive power of a negative lens disposed to be closer to the image side than the object-side lens group. However, when the refractive power of the negative lens disposed to be closer to the image side than the object-side lens group is strengthened, it may be difficult to correct a spherical aberration or a comatic aberration.

Conversely, when the ratio is greater than the upper limit of the foregoing Condition Expression (1), the refractive power of the second lens group is too weak, an amount of movement of the focus lens group (second lens group) may increase when the subject distance is changed from infinity to proximity, and thus the lens system may increase in size. Further, a change in the spherical aberration may increase at the time of proximity, and thus deterioration in the optical performance may be caused.

Accordingly, when the imaging lens satisfies the foregoing Condition Expression (1), excellent imaging performance from infinity to proximity is ensured while an amount of movement of a focus lens group is set to be small at the time of change in the subject distance from infinity to proximity, and thus optical performance can be achieved.

Further, the imaging lens more preferably satisfies the following Condition Expression (1)′:

−12.0 < f1F / f2 < −5.0.  (1)′

Accordingly, when the imaging lens satisfies the foregoing Condition Expression (1)′, the excellent imaging performance from infinity to proximity is ensured while an amount of movement of a focus lens group is set to be smaller at the time of change in the subject distance from infinity to proximity, and thus optical performance can be further achieved.

In the imaging lens according to the embodiment of the present technology, the following Condition Expression (2) is preferably satisfied:

1.8 < f1 / f < 4.5,  (2)

where f1 is a focal distance of the first lens group at the infinity focus time and f is a focal distance of an entire lens system at the infinity focus time.

The foregoing Condition Expression (2) defines a ratio of the focal distance of the first lens group to the focal distance of the entire lens system at the infinity focus time.

When the ratio is less than the lower limit of the foregoing Condition Expression (2), the refractive power of the first lens group is too strong, and thus it may be difficult to ensure the sufficient back focus of the lens system. Further, the correction of the distortion aberration or the spherical aberration may not be sufficiently performed.

Conversely, when the ratio is greater than the upper limit of the foregoing Condition Expression (2), the refractive power of the first lens group is too weak, and the entire length may be lengthened. At this time, to shorten the entire length, it is necessary to strengthen the refractive power of the second lens group. However, when the refractive power of the second lens group is strengthened, it may be difficult to correct the spherical aberration and the manufacturing sensitivity may increase.

Accordingly, when the imaging lens satisfies the foregoing Condition Expression (2), it is possible to satisfactorily correct the distortion aberration or the spherical aberration, while sufficient back focus is ensured, and reduction in manufacturing sensitivity can be achieved.

In the imaging lens, the following Condition Expression (2)′ is more preferably satisfied:

2.0 < f1 / f < 4.0.  (2)′

When the imaging lens satisfies the foregoing Condition Expression (2)′, it is possible to more satisfactorily correct the distortion aberration or the spherical aberration, while sufficient back focus is ensured, and more reduction in the manufacturing sensitivity can be achieved.

In the imaging lens, the following Condition Expression (2)″ is more preferably satisfied:

2.4 < f1 / f < 3.6.  (2)″

When the imaging lens satisfies the foregoing Condition Expression (2)″, it is possible to still more satisfactorily correct the distortion aberration or the spherical aberration, while sufficient back focus is ensured, and still more reduction in the manufacturing sensitivity can be achieved.

In the imaging lens according to the embodiment of the present technology, the object-side lens group includes a first lens having a positive refractive power and a second lens having a negative refractive power that are configured to be arranged sequentially from the object side to the image side.

When the object-side lens group includes the first lens having the positive refractive power and the second lens having the negative refractive power that are configured to be arranged sequentially from the object side to the image side, it is possible to reduce the air space between the first and second lenses, and thus to suppress the degree of curve of a light beam oriented from the first lens to the second lens. Accordingly, the sensitivity of the air space between the first and second lenses can be suppressed.

In the imaging lens according to the embodiment of the present technology, the second lens group preferably includes two pairs of cemented lenses.

When the second lens group includes the two pairs of cemented lenses, it is possible to satisfactorily correct a high-order spherical aberration and achieve simplicity of the configuration of a lens tube or ease of manufacturing.

In the imaging lens according to the embodiment of the present technology, each of the first lens group and the second lens group preferably includes at least one aspheric lens.

When the first lens group includes at least one aspheric lens, it is possible to satisfactorily correct the spherical aberration or field curvature. When the second lens group includes at least one aspheric lens, it is possible to satisfactorily correct off-axis comatic aberration.

In the imaging lens according to the embodiment of the present technology, when the subject distance is changed from infinity to proximity, the aperture stop and the second lens group are preferably integrally configured and moved from the image side to the object side.

When the subject distance is changed from infinity to proximity, it is possible to sufficiently ensure an amount of peripheral light from infinity to proximity by integrally configuring the aperture stop and the second lens group and moving the aperture stop and the second lens group from the image side to the object side, compared to the rear focus type in which an aperture stop is fixed and only the second lens group is moved in the optical axis direction.

Numerical Example of Imaging Lens

Hereinafter, an imaging lens according to a specific embodiment of the present technology and a numerical example in which specific numerical values are applied to the imaging lens according to the embodiment will be described with reference to the drawings and tables.

Further, the meanings of signs used in each table or description are as follows.

"Surface number” denotes a surface number of an ith surface numbered from the object side to the image side, "R” denotes a paraxial radius of curvature of an ith surface, "D” denotes an on-axis surface distance (thickness or air gap of the center of a lens) between an ith surface and an i+1th surface, "Nd” denotes a refractive index of a line d (λ=587.6 nm) of a lens or the like starting from an ith surface, and "νd” denotes an Abbe number of the line d of a lens or the like starting from an ith surface.

"ASP” denotes an aspheric surface of a corresponding surface in association with "surface number.”

"k” is a cone constant (conic constant) and "A4,” "A6,” "A8,” and "A10” denote fourth, sixth, eighth, and tenth order aspheric coefficients, respectively.

"f” denotes a focal distance, "Fno” denotes an F number, "BF” denotes a back focus, and "ω” denotes a half field angle.

In each table that shows the following aspheric coefficients, "E−n” indicates an exponential notation in which 10 is the base, that is, "10 to the negative nth power.” For example, "0.12345E-0.5” indicates "0.12345x (10 to the negative 5th power).”

In an imaging lens described in each embodiment, some of the lens surfaces are aspheric. On the assumption that "x” is a distance (sag amount) from the apex of a lens surface in an optical axis direction, "y” is a height (image height) in a direction perpendicular to the optical axis direction, "c” is a paraxial curvature (the reciprocal of a radius of curvature) in the apex of a lens, "k” is a cone constant (cone constant), and "Ai” is each degree of aspheric coefficients, the shape of an aspheric surface is defined as in Equation 1 below.

x = ((y2 · c2) / (1 + {1 - (1 + k) · y2 · c2}1/2)) + Σ (Ai · yi) Equation 1

An imaging lens 1 to an imaging lens 7 according to first to seventh embodiments to be described below each include a first lens group G1 having a positive refractive power, an aperture stop S, and a second lens group G2 having a positive refractive power that are configured to be arranged sequentially from an object side to an image side.

First Embodiment

FIG. 1 is a diagram illustrating the configuration of an imaging lens 1 according to a first embodiment of the present technology.

In the imaging lens 1, focus is achieved by fixing the first lens group G1 in an optical axis direction and moving the second lens group G2 from an image side to an object side when a subject distance is changed from infinity to proximity.

The first lens group G1 includes an object-side lens group G1F having a negative refractive power and an image-side lens group G1R having a positive refractive power that are configured to be arranged sequentially from the object side to the image side. In an air space of the first lens group G1, an air space between the object-side lens group G1F and the image-side lens group G1R is set to be the maximum.

The object-side lens group G1F includes a first lens L1 having a positive refractive power and a biconvex shape and a second lens L2 having a negative refractive power and a biconcave shape that are configured to be arranged sequentially from the object side to the image side.

The image-side lens group G1R includes a cemented lens in which a third lens L3 located to be closer to the object side, having a positive refractive power, and having a biconvex shape is cemented with a fourth lens L4 located to be closer to the image side, having a negative refractive power, and having a biconcave shape.

The second lens group G2 includes two pairs of cemented lenses, that is, a first cemented lens and a second cemented lens, that are configured to be arranged sequentially from the object side to the image side.

The first cemented lens is configured such that a fifth lens L5 located to be closer to the object side, having a negative refractive power, and having a biconcave shape is cemented with a sixth lens L6 located to be closer to the image side, having a positive refractive power, and having a biconvex shape.

The second cemented lens is configured such that a seventh lens L7 located to be closer to the object side, having a negative refractive power, and having a meniscus shape is cemented with an eighth lens L8 located to be closer to the image side, having a positive refractive power, and having a biconvex shape. The seventh lens L7 is formed in the meniscus shape of which a concave surface is oriented toward the image side.

The aperture stop S is integrally configured with the second lens group G2 and is moved from the image side to the object side when the subject distance is changed from infinity to proximity.

Table 1 shows lens data of Numerical Example 1 in which specific numerical values are applied to the imaging lens 1 according to the first embodiment.

TABLE 1

Surface
Number R D Nd νd

 1 63.162 6.056 1.834805 42.7
 2 −235.242 0.598
 3 −151.479 1.300 1.592703 35.4
 4 35.000 2.000
 5 (ASP) 28.841 7.657 1.851348 40.1
 6 −198.594 1.200 1.612930 37.0
 7 25.666 14.067
 8 infinity 6.004
 9 −22.734 1.582 1.647690 33.8
10 26.722 9.000 1.883000 40.8
11 −56.939 0.200
12 222.462 2.466 1.717360 29.5
13 34.696 6.815 1.801387 45.4
14 (ASP) −50.857 —

In the imaging lens 1, an object-side surface (fifth surface) of the third lens L3 of the first lens group G1 and an image-side surface (fourteenth surface) of the eighth lens L8 of the second lens group G2 are aspheric. The fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth order aspheric coefficient A8, and the tenth order aspheric coefficient A10 of the aspheric surfaces in Numerical Example 1 are shown together with the cone constants k in Table 2.

TABLE 2

Surface
Number κ A4 A6 A8 A10
5 0.0000 −1.02E−06 −1.40E−09 1.13E−12 −1.33E−15
14 −1.0388  6.69E−06 −1.24E−09 2.47E−11 −3.41E−15

The focal distance f, the F number Fno, the back focus BF, and the half field angle ω of the entire lens system at the infinity focus time in Numerical Example 1 are shown in Table 3.

TABLE 3

f 51.5
Fno 1.45
BF 35.998
ω 23.41

FIG. 2 illustrates a spherical aberration, an astigmatism, a distortion aberration, and a lateral aberration at an infinity focus state in Numerical Example 1.

In FIG. 2, a value of a line d (587.56 nm) in the spherical aberration is illustrated. In the astigmatism, a solid line indicates a value on a sagittal image plane of a line d and a dashed line indicates a value on a meridional image plane of the line d. In the distortion aberration, a value of a line d is illustrated. In the lateral aberration, a value of a line d is illustrated. In the lateral aberration, y denotes an image height and ω denotes a half field angle.

From the aberration diagrams, it is apparent that various aberrations are satisfactorily corrected and excellent imaging performance is realized in Numerical Example 1.

Second Embodiment

FIG. 3 is a diagram illustrating the configuration of an imaging lens 2 according to a second embodiment of the present technology.

In the imaging lens 2, focus is achieved by fixing the first lens group G1 in an optical axis direction and moving the second lens group G2 from an image side to an object side when a subject distance is changed from infinity to proximity.

The first lens group G1 includes an object-side lens group G1F having a negative refractive power and an image-side lens group G1R having a positive refractive power that are configured to be arranged sequentially from the object side to the image side. In an air space of the first lens group G1, an air space between the object-side lens group G1F and the image-side lens group G1R is set to be the maximum.

The object-side lens group G1F includes a first lens L1 having a positive refractive power and a biconvex shape and a second lens L2 having a negative refractive power and a biconcave shape that are configured to be arranged sequentially from the object side to the image side.

The image-side lens group G1R includes a cemented lens in which a third lens L3 located to be closer to the object side, having a positive refractive power, and having a biconvex shape is cemented with a fourth lens L4 located to be closer to the image side, having a negative refractive power, and having a biconcave shape.

The second lens group G2 includes two pairs of cemented lenses, that is, a first cemented lens and a second cemented lens, that are configured to be arranged sequentially from the object side to the image side.

The first cemented lens is configured such that a fifth lens L5 located to be closer to the object side, having a negative refractive power, and having a biconcave shape is cemented with a sixth lens L6 located to be closer to the image side, having a positive refractive power, and having a biconvex shape.

The second cemented lens is configured such that a seventh lens L7 located to be closer to the object side, having a negative refractive power, and having a meniscus shape is cemented with an eighth lens L8 located to be closer to the image side, having a positive refractive power, and having a biconvex shape. The seventh lens L7 is formed in the meniscus shape of which a concave surface is oriented toward the image side.

The aperture stop S is integrally configured with the second lens group G2 and is moved from the image side to the object side when the subject distance is changed from infinity to proximity.

Table 4 shows lens data of Numerical Example 2 in which specific numerical values are applied to the imaging lens 2 according to the second embodiment.

TABLE 4

Surface
Number R D Nd νd

 1 65.394 6.591 1.834805 42.7
 2 −174.403 0.741
 3 −127.563 1.300 1.592703 35.4
 4 35.000 2.000
 5 (ASP) 29.459 7.554 1.882023 37.2
 6 −260.016 1.200 1.647690 33.8
 7 26.509 14.026
 8 infinity 8.130
 9 −21.790 3.082 1.654362 33.2
10 30.624 8.260 1.883000 40.8
11 −49.935 0.200
12 146.407 2.950 1.724825 28.4
13 44.548 6.621 1.772501 49.5
14 (ASP) −50.211 —

In the imaging lens 2, an object-side surface (fifth surface) of the third lens L3 of the first lens group G1 and an image-side surface (fourteenth surface) of the eighth lens L8 of the second lens group G2 are aspheric. The fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth order aspheric coefficient A8, and the tenth order aspheric coefficient A10 of the aspheric surfaces in Numerical Example 2 are shown together with the cone constants k in Table 5.

TABLE 5

Surface
Number κ A4 A6 A8 A10
5 0.0000 −9.84E−07 −6.92E−10 −1.13E−12  3.26E−15
14 0.6967  7.28E−06 −8.16E−10  2.03E−11 −1.10E−14

The focal distance f, the F number Fno, the back focus BF, and the half field angle ω of the entire lens system at the infinity focus time in Numerical Example 2 are shown in Table 6.

TABLE 6

f 51.5
Fno 1.44
BF 36.221
ω 23.40

FIG. 4 illustrates a spherical aberration, an astigmatism, a distortion aberration, and a lateral aberration at an infinity focus state in Numerical Example 2.

In FIG. 4, a value of a line d (587.56 nm) in the spherical aberration is illustrated. In the astigmatism, a solid line indicates a value on a sagittal image plane of a line d and a dashed line indicates a value on a meridional image plane of the line d. In the distortion aberration, a value of a line d is illustrated. In the lateral aberration, a value of a line d is illustrated. In the lateral aberration, y denotes an image height and ω denotes a half field angle.

From the aberration diagrams, it is apparent that various aberrations are satisfactorily corrected and excellent imaging performance is realized in Numerical Example 2.

Third Embodiment

FIG. 5 is a diagram illustrating the configuration of an imaging lens 3 according to a third embodiment of the present technology.

In the imaging lens 3, focus is achieved by fixing the first lens group G1 in an optical axis direction and moving the second lens group G2 from an image side to an object side when a subject distance is changed from infinity to proximity.

The first lens group G1 includes an object-side lens group G1F having a negative refractive power and an image-side lens group G1R having a positive refractive power that are configured to be arranged sequentially from the object side to the image side. In an air space of the first lens group G1, an air space between the object-side lens group G1F and the image-side lens group G1R is set to be the maximum.

The object-side lens group G1F includes a first lens L1 having a positive refractive power and a biconvex shape and a second lens L2 having a negative refractive power and a biconcave shape that are configured to be arranged sequentially from the object side to the image side.

The image-side lens group G1R includes a cemented lens in which a third lens L3 located to be closer to the object side, having a positive refractive power, and having a biconvex shape is cemented with a fourth lens L4 located to be closer to the image side, having a negative refractive power, and having a biconcave shape.

The second lens group G2 includes two pairs of cemented lenses, that is, a first cemented lens and a second cemented lens, that are configured to be arranged sequentially from the object side to the image side.

The first cemented lens is configured such that a fifth lens L5 located to be closer to the object side, having a negative refractive power, and having a biconcave shape is cemented with a sixth lens L6 located to be closer to the image side, having a positive refractive power, and having a biconvex shape.

The second cemented lens is configured such that a seventh lens L7 located to be closer to the object side, having a negative refractive power, and having a meniscus shape is cemented with an eighth lens L8 located to be closer to the image side, having a positive refractive power, and having a biconvex shape. The seventh lens L7 is formed in the meniscus shape of which a concave surface is oriented toward the image side.

The aperture stop S is integrally configured with the second lens group G2 and is moved from the image side to the object side when the subject distance is changed from infinity to proximity.

Table 7 shows lens data of Numerical Example 3 in which specific numerical values are applied to the imaging lens 3 according to the third embodiment.

TABLE 7

Surface
Number R D Nd νd

 1 68.507 7.500 1.834805 42.7
 2 −151.036 0.350
 3 −121.340 1.300 1.592703 34.5
 4 35.000 2.610
 5 (ASP) 29.374 7.970 1.882023 37.2
 6 −278.736 1.200 1.647690 33.8
 7 26.881 14.214
 8 infinity 5.980
 9 −22.069 2.960 1.647689 33.8
10 30.122 7.940 1.883000 40.8
11 −50.458 0.200
12 189.508 2.630 1.717360 29.5
13 40.196 6.900 1.772501 49.5
14 (ASP) −50.203 —

In the imaging lens 3, an object-side surface (fifth surface) of the third lens L3 of the first lens group G1 and an image-side surface (fourteenth surface) of the eighth lens L8 of the second lens group G2 are aspheric. The fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth order aspheric coefficient A8, and the tenth order aspheric coefficient A10 of the aspheric surfaces in Numerical Example 3 are shown together with the cone constants k in Table 8.

TABLE 8

Surface
Number κ A4 A6 A8 A10
 5 0.0000 −1.13E−06 1.18E−10 −4.31E−12 8.06E−15
14 −1.9999  4.73E−06 6.73E−10  1.45E−11 5.36E−16

The focal distance f, the F number Fno, the back focus BF, and the half field angle ω of the entire lens system at the infinity focus time in Numerical Example 3 are shown in Table 9.

TABLE 9

f 51.5
Fno 1.45
BF 36.108
ω 23.33

FIG. 6 illustrates a spherical aberration, an astigmatism, a distortion aberration, and a lateral aberration at an infinity focus state in Numerical Example 3.

In FIG. 6, a value of a line d (587.56 nm) in the spherical aberration is illustrated. In the astigmatism, a solid line indicates a value on a sagittal image plane of a line d and a dashed line indicates a value on a meridional image plane of the line d. In the distortion aberration, a value of a line d is illustrated. In the lateral aberration, a value of a line d is illustrated. In the lateral aberration, y denotes an image height and ω denotes a half field angle.

From the aberration diagrams, it is apparent that various aberrations are satisfactorily corrected and excellent imaging performance is realized in Numerical Example 3.

Fourth Embodiment

FIG. 7 is a diagram illustrating the configuration of an imaging lens 4 according to a fourth embodiment of the present technology.

In the imaging lens 4, focus is achieved by fixing the first lens group G1 in an optical axis direction and moving the second lens group G2 from an image side to an object side when a subject distance is changed from infinity to proximity.

The first lens group G1 includes an object-side lens group G1F having a negative refractive power and an image-side lens group G1R having a positive refractive power that are configured to be arranged sequentially from the object side to the image side. In an air space of the first lens group G1, an air space between the object-side lens group G1F and the image-side lens group G1R is set to be the maximum.

The object-side lens group G1F includes a first lens L1 having a positive refractive power and a biconvex shape and a second lens L2 having a negative refractive power and a biconcave shape that are configured to be arranged sequentially from the object side to the image side.

The image-side lens group G1R includes a cemented lens in which a third lens L3 located to be closer to the object side, having a positive refractive power, and having a biconvex shape is cemented with a fourth lens L4 located to be closer to the image side, having a negative refractive power, and having a biconcave shape.

The second lens group G2 includes two pairs of cemented lenses, that is, a first cemented lens and a second cemented lens, that are configured to be arranged sequentially from the object side to the image side.

The first cemented lens is configured such that a fifth lens L5 located to be closer to the object side, having a negative refractive power, and having a biconcave shape is cemented with a sixth lens L6 located to be closer to the image side, having a positive refractive power, and having a biconvex shape.

The second cemented lens is configured such that a seventh lens L7 located to be closer to the object side, having a negative refractive power, and having a meniscus shape is cemented with an eighth lens L8 located to be closer to the image side, having a positive refractive power, and having a biconvex shape. The seventh lens L7 is formed in the meniscus shape of which a concave surface is oriented toward the image side.

The aperture stop S is integrally configured with the second lens group G2 and is moved from the image side to the object side when the subject distance is changed from infinity to proximity.

Table 10 shows lens data of Numerical Example 4 in which specific numerical values are applied to the imaging lens 4 according to the fourth embodiment.

TABLE 10

Surface
Number R D Nd νd

 1 60.388 6.040 1.834805 42.7
 2 −214.645 0.370
 3 −156.603 1.300 1.592703 35.5
 4 35.000 3.000
 5 (ASP) 28.547 7.170 1.851348 40.1
 6 −503.384 1.200 1.612930 37.0
 7 25.007 14.509
 8 infinity 6.333
 9 −21.841 2.800 1.647690 33.8
10 30.673 7.940 1.883000 40.8
11 −47.908 0.200
12 247.339 2.130 1.698950 30.1
13 38.671 7.000 1.768015 49.2
14 (ASP) −50.305 —

In the imaging lens 4, an object-side surface (fifth surface) of the third lens L3 of the first lens group G1 and an image-side surface (fourteenth surface) of the eighth lens L8 of the second lens group G2 are aspheric. The fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth order aspheric coefficient A8, and the tenth order aspheric coefficient A10 of the aspheric surfaces in Numerical Example 4 are shown together with the cone constants k in Table 11.

TABLE 11

Surface
Number κ A4 A6 A8 A10
 5 0.0000 −1.05E−06 −6.57E−10 −1.73E−12  4.21E−15
14 −1.6554  5.10E−06 −9.77E−10  2.06E−11 −8.11E−15

The focal distance f, the F number Fno, the back focus BF, and the half field angle ω of the entire lens system at the infinity focus time in Numerical Example 4 are shown in Table 12.

TABLE 12

f 51.5
Fno 1.45
BF 36.098
ω 23.39

FIG. 8 illustrates a spherical aberration, an astigmatism, a distortion aberration, and a lateral aberration at an infinity focus state in Numerical Example 4.

In FIG. 8, a value of a line d (587.56 nm) in the spherical aberration is illustrated. In the astigmatism, a solid line indicates a value on a sagittal image plane of a line d and a dashed line indicates a value on a meridional image plane of the line d. In the distortion aberration, a value of a line d is illustrated. In the lateral aberration, a value of a line d is illustrated. In the lateral aberration, y denotes an image height and ω denotes a half field angle.

From the aberration diagrams, it is apparent that various aberrations are satisfactorily corrected and excellent imaging performance is realized in Numerical Example 4.

Fifth Embodiment

FIG. 9 is a diagram illustrating the configuration of an imaging lens 5 according to a fifth embodiment of the present technology.

In the imaging lens 5, focus is achieved by fixing the first lens group G1 in an optical axis direction and moving the second lens group G2 from an image side to an object side when a subject distance is changed from infinity to proximity.

The first lens group G1 includes an object-side lens group G1F having a negative refractive power and an image-side lens group G1R having a positive refractive power that are configured to be arranged sequentially from the object side to the image side. In an air space of the first lens group G1, an air space between the object-side lens group G1F and the image-side lens group G1R is set to be the maximum.

The object-side lens group G1F includes a first lens L1 having a positive refractive power and a biconvex shape and a second lens L2 having a negative refractive power and a biconcave shape that are configured to be arranged sequentially from the object side to the image side.

The image-side lens group G1R includes a cemented lens in which a third lens L3 located to be closer to the object side, having a positive refractive power, and having a biconvex shape is cemented with a fourth lens L4 located to be closer to the image side, having a negative refractive power, and having a biconcave shape.

The second lens group G2 includes two pairs of cemented lenses, that is, a first cemented lens and a second cemented lens, that are configured to be arranged sequentially from the object side to the image side.

The first cemented lens is configured such that a fifth lens L5 located to be closer to the object side, having a negative refractive power, and having a biconcave shape is cemented with a sixth lens L6 located to be closer to the image side, having a positive refractive power, and having a biconvex shape.

The second cemented lens is configured such that a seventh lens L7 located to be closer to the object side, having a negative refractive power, and having a meniscus shape is cemented with an eighth lens L8 located to be closer to the image side, having a positive refractive power, and having a biconvex shape. The seventh lens L7 is formed in the meniscus shape of which a concave surface is oriented toward the image side.

The aperture stop S is integrally configured with the second lens group G2 and is moved from the image side to the object side when the subject distance is changed from infinity to proximity.

Table 1 shows lens data of Numerical Example 5 in which specific numerical values are applied to the imaging lens 5 according to the fifth embodiment.

TABLE 13

Surface
Number R D Nd νd

 1 63.363 6.096 1.834805 42.7
 2 −264.080 0.573
 3 −167.023 1.300 1.592703 35.5
 4 35.000 1.434
 5 (ASP) 31.048 7.598 1.851348 40.1
 6 −140.556 1.200 1.615257 36.9
 7 29.526 13.329
 8 infinity 5.990
 9 −24.660 4.732 1.639323 34.5
10 28.826 9.000 1.883000 40.8
11 −56.543 0.200
12 284.284 1.900 1.713063 29.3
13 32.786 7.000 1.804200 46.5
14 (ASP) −64.561 —

In the imaging lens 5, an object-side surface (fifth surface) of the third lens L3 of the first lens group G1 and an image-side surface (fourteenth surface) of the eighth lens L8 of the second lens group G2 are aspheric. The fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth order aspheric coefficient A8, and the tenth order aspheric coefficient A10 of the aspheric surfaces in Numerical Example 5 are shown together with the cone constants k in Table 14.

TABLE 14

Surface
Number κ A4 A6 A8 A10
 5 −0.3187 4.24E−07  1.11E−09 −3.87E−12  1.05E−14
14 1.0513 7.15E−06 −5.97E−09  5.00E−11 −6.39E−14

The focal distance f, the F number Fno, the back focus BF, and the half field angle ω of the entire lens system at the infinity focus time in Numerical Example 5 are shown in Table 15.

TABLE 15

f 51.5
Fno 1.44
BF 36.000
ω 23.41

FIG. 10 illustrates a spherical aberration, an astigmatism, a distortion aberration, and a lateral aberration at an infinity focus state in Numerical Example 5.

In FIG. 10, a value of a line d (587.56 nm) in the spherical aberration is illustrated. In the astigmatism, a solid line indicates a value on a sagittal image plane of a line d and a dashed line indicates a value on a meridional image plane of the line d. In the distortion aberration, a value of a line d is illustrated. In the lateral aberration, a value of a line d is illustrated. In the lateral aberration, y denotes an image height and ω denotes a half field angle.

From the aberration diagrams, it is apparent that various aberrations are satisfactorily corrected and excellent imaging performance is realized in Numerical Example 5.

Sixth Embodiment

FIG. 11 is a diagram illustrating the configuration of an imaging lens 6 according to a sixth embodiment of the present technology.

In the imaging lens 6, focus is achieved by fixing the first lens group G1 in an optical axis direction and moving the second lens group G2 from an image side to an object side when a subject distance is changed from infinity to proximity.

The first lens group G1 includes an object-side lens group G1F having a negative refractive power and an image-side lens group G1R having a positive refractive power that are configured to be arranged sequentially from the object side to the image side. In an air space of the first lens group G1, an air space between the object-side lens group G1F and the image-side lens group G1R is set to be the maximum.

The object-side lens group G1F includes a first lens L1 having a positive refractive power and a biconvex shape and a second lens L2 having a negative refractive power and a biconcave shape that are configured to be arranged sequentially from the object side to the image side.

The image-side lens group G1R includes a cemented lens in which a third lens L3 located to be closer to the object side, having a positive refractive power, and having a biconvex shape is cemented with a fourth lens L4 located to be closer to the image side, having a negative refractive power, and having a biconcave shape.

The second lens group G2 includes two pairs of cemented lenses, that is, a first cemented lens and a second cemented lens, that are configured to be arranged sequentially from the object side to the image side.

The first cemented lens is configured such that a fifth lens L5 located to be closer to the object side, having a negative refractive power, and having a biconcave shape is cemented with a sixth lens L6 located to be closer to the image side, having a positive refractive power, and having a biconvex shape.

The second cemented lens is configured such that a seventh lens L7 located to be closer to the object side, having a negative refractive power, and having a meniscus shape is cemented with an eighth lens L8 located to be closer to the image side, having a positive refractive power, and having a biconvex shape. The seventh lens L7 is formed in the meniscus shape of which a concave surface is oriented toward the image side.

The aperture stop S is integrally configured with the second lens group G2 and is moved from the image side to the object side when the subject distance is changed from infinity to proximity.

Table 16 shows lens data of Numerical Example 6 in which specific numerical values are applied to the imaging lens 6 according to the sixth embodiment.

TABLE 16

Surface
Number R D Nd νd

 1 67.550 6.166 1.834805 42.7
 2 −185.791 0.628
 3 −127.895 1.300 1.592703 35.5
 4 35.000 2.000
 5 (ASP) 28.466 7.888 1.851348 40.1
 6 −179.046 1.200 1.595510 39.2
 7 24.873 14.578
 8 infinity 6.001
 9 −21.283 0.800 1.672700 32.2
10 29.250 8.918 1.883000 40.8
11 −47.574 0.200
12 218.916 2.336 1.740770 27.8
13 47.742 6.494 1.801387 45.5
14 (ASP) −45.475 —

In the imaging lens 6, an object-side surface (fifth surface) of the third lens L3 of the first lens group G1 and an image-side surface (fourteenth surface) of the eighth lens L8 of the second lens group G2 are aspheric. The fourth-order aspheric coefficient A4, the sixth-order aspheric coefficient A6, the eighth order aspheric coefficient A8, and the tenth order aspheric coefficient A10 of the aspheric surfaces in Numerical Example 6 are shown together with the cone constants k in Table 17.

TABLE 17

Surface
Number κ A4 A6 A8 A10
 5 0.0000 −1.33E−06 −8.67E−10 −1.74E−12 1.84E−15
14 −1.4361  4.42E−06  3.48E−10  1.29E−11 3.29E−15

The focal distance f, the F number Fno, the back focus BF, and the half field angle ω of the entire lens system at the infinity focus time in Numerical Example 6 are shown in Table 18.

TABLE 18

f 51.5
Fno 1.45
BF 36.986
ω 23.41

FIG. 12 illustrates a spherical aberration, an astigmatism, a distortion aberration, and a lateral aberration at an infinity focus state in Numerical Example 6.

In FIG. 12, a value of a line d (587.56 nm) in the spherical aberration is illustrated. In the astigmatism, a solid line indicates a value on a sagittal image plane of a line d and a dashed line indicates a value on a meridional image plane of the line d. In the distortion aberration, a value of a line d is illustrated. In the lateral aberration, a value of a line d is illustrated. In the lateral aberration, y denotes an image height and ω denotes a half field angle.

From the aberration diagrams, it is apparent that various aberrations are satisfactorily corrected and excellent imaging performance is realized in Numerical Example 6.

Seventh Embodiment

FIG. 13 is a diagram illustrating the configuration of an imaging lens 7 according to a seventh embodiment of the present technology.

In the imaging lens 7, focus is achieved by fixing the first lens group G1 in an optical axis direction and moving the second lens group G2 from an image side to an object side when a subject distance is changed from infinity to proximity.

The first lens group G1 includes an object-side lens group G1F having a negative refractive power and an image-side lens group G1R having a positive refractive power that are configured to be arranged sequentially from the object side to the image side. In an air space of the first lens group G1, an air space between the object-side lens group G1F and the image-side lens group G1R is set to be the maximum.

The object-side lens group G1F includes a first lens L1 having a positive refractive power and a biconvex shape and a second lens L2 having a negative refractive power and a biconcave shape that are configured to be arranged sequentially from the object side to the image side.

The image-side lens group G1R includes a cemented lens in which a third lens L3 located to be closer to the object side, having a positive refractive power, and having a biconvex shape is cemented with a fourth lens L4 located to be closer to the image side, having a negative refractive power, and having a biconcave shape.

The second lens group G2 includes two pairs of cemented lenses, that is, a first cemented lens and a second cemented lens, that are configured to be arranged sequentially from the object side to the image side.

The first cemented lens is configured such that a fifth lens