Camera, optical system and interchangeable lens with birefringent device

Patent metadata

Field	Value
Publication number	US-2016291230-A1
Application number	US-201615075561-A
Country	US
Kind code	A1
Filing date	Mar 21, 2016
Priority date	Mar 31, 2015
Publication date	Oct 6, 2016
Grant date	—

Abstract

An optical system ( 110 ) includes a lens unit ( 112 ) with a plurality of lenses. An out-of-focus point spread function of the lens unit ( 112 ) includes an annular intensity distribution with at least one ring-shaped side peak at a radial distance to a center point. A birefringent device ( 115 ) in an optical path of the optical system ( 110 ) is adapted to selectively attenuate the ring-shaped side peak in the out-of-focus point spread function of the lens unit ( 112 ).

First claim

1 . An optical system comprising:
a lens unit comprising a plurality of lenses, wherein an out-of-focus point spread function of the lens unit includes an intensity distribution with a ring-shaped side peak at a radial distance to a center point; and a birefringent device in an optical path of the optical system, wherein the birefringent device is adapted to selectively attenuate the ring-shaped side peak in the out-of-focus point spread function of the lens unit.

2 . The optical system according to claim 1 , wherein
the pupil function of the lens unit is rotational symmetric with respect to the optical axis.

3 . The optical system according to claim 1 , wherein
the pupil function of the lens unit is circularly symmetric with respect to the optical axis.

4 . The optical system according to claim 1 , wherein
the pupil function of the optical system comprises a first pupil function assigned to a first polarization state and a second pupil function assigned to a second polarization state orthogonal to the first polarization state, and the phase portion of the first pupil function is a complex conjugate of the phase portion of the second pupil function.

5 . The optical system according to claim 1 , wherein
in the birefringent device an orientation of an ordinary axis and an orientation of an extraordinary axis change radially with respect to the optical axis of the optical system, respectively.

6 . The optical system according to claim 1 , wherein
the birefringent device comprises a circular inner zone and at least two annular zones surrounding the circular inner zone, respectively, wherein the circular inner zone and the neighboring annular zone as well as neighboring annular zones have different orientations of the ordinary and extraordinary axes of the birefringent material.

7 . The optical system according to claim 6 , wherein
a radius of the circular inner zone is at least half a radius of an effective area of the birefringent device.

8 . The optical system according to claim 6 , wherein
the birefringent device comprises at least ten annular zones.

9 . The optical system according to claim 6 , wherein
the orientation of an ordinary axis in an annular zone corresponds to the orientation of an extraordinary axis in a neighboring circular inner zone or annular zone.

10 . The optical system according to claim 1 , wherein
the birefringent device comprises a liquid crystal layer.

11 . The optical system according to claim 10 , further comprising
a control unit configured to control the liquid crystal layer in response to a user input or an internal state, wherein in a first state a phase function of the liquid crystal layer is configured to attenuate the ring-shaped side peak in the intensity distribution of the out-of-focus point spread function of the lens unit and in a second state an effect of the liquid crystal layer on the out-of-focus point spread function is reduced with respect to the first state.

12 . The optical system according to claim 1 , further comprising
the birefringent device comprises a first structure in which a refractive index effective for the first polarization state changes with increasing distance to the optical axis and a second structure in which a refractive index effective for the second polarization state changes with increasing distance to the optical axis.

13 . The optical system according to claim 1 , wherein
the birefringent device comprises a birefringent coating on an element of the lens unit.

14 . The optical system according to claim 1 , wherein
the birefringent device is adapted to attenuate the ring-shaped side peak in the out-of-focus point spread function of the lens unit by at least 25 percent.

15 . An interchangeable lens comprising:
a lens unit comprising a plurality of lenses, wherein an out-of-focus point spread function of the lens unit includes an intensity distribution with a ring-shaped side peak at a radial distance to a center point; and a birefringent device in an optical path of the interchangeable lens, wherein the birefringent device is adapted to selectively attenuate the ring-shaped side peak in the out-of-focus point spread function of the lens unit.

16 . The interchangeable lens according to claim 15 , wherein
the birefringent device is adapted to attenuate the ring-shaped side peak in the out-of-focus point spread function of the lens unit by at least 25 percent.

17 . A camera, comprising:
a lens unit comprising a plurality of lenses, wherein an out-of-focus point spread function of the lens unit includes an intensity distribution with a ring-shaped side peak at a radial distance to a center point; and a birefringent device in an optical path of the lens unit, wherein the birefringent device is adapted to selectively attenuate the ring-shaped side peak in the out-of-focus point spread function of the lens unit.

18 . The camera according to claim 17 , wherein
the birefringent device is adapted to attenuate the ring-shaped side peak in the out-of-focus point spread function of the lens unit by at least 25 percent.

19 . A method of manufacturing an optical system, the method comprising:
determining an out-of-focus point spread function of a lens unit that comprises a plurality of lenses, and determining, by using a numerical optimization method, a polarization dependent phase alteration for the pupil function, the phase alteration attenuating a ring-shaped side peak in an intensity distribution of the out-of-focus point spread function of the lens unit by at least 25 percent when combined with the phase portion of the pupil function of the lens unit, the numerical optimization method varying two complex conjugate phase alterations in combination with the pupil function of the lens unit for minimizing the ring-shaped side peaks at minimum effect on an in-focus point spread function of the lens unit.

20 . The method according to claim 19 , further comprising
manufacturing a birefringent device embodying the two complex conjugate phase alterations.

21 . The method according to claim 20 , further comprising
mounting the birefringent device in the optical path of the optical system.

Assignees

• Sony Corp

Inventors

• Weichelt Christin
• Kamm Markus

Classifications

• G02F1/1313

  specially adapted for a particular application · CPC title

• G02B27/0012

  Optical design, e.g. procedures, algorithms, optimisation routines · CPC title

• G03B11/00

  Filters or other obturators specially adapted for photographic purposes · CPC title

• G02B27/0988

  Diaphragms, spatial filters, masks for removing or filtering a part of the beam · CPC title

• G02F1/134309

  characterised by their geometrical arrangement · CPC title