Auto-focus in low-profile folded optics multi-camera system

• US 9,374,516 B2
• Filed: 10/28/2014
• Issued: 06/21/2016
• Est. Priority Date: 04/04/2014
• Status: Active Grant

• Current Assignee: Qualcomm, Inc.
• Original Assignee: Qualcomm, Inc.
• Inventors: Osborne, Thomas Wesley
• Primary Examiner(s): CUTLER, ALBERT H
• Application Number:
  US14/526,104
• Publication Number:
  US 20150288865A1
• Time in Patent Office: 602 Days
• Field of Search: 348/337, 348/338
• US Class Current: 1/1
• CPC Class Codes: G02B 13/006 at least one element being a compound optical element, e.g. cemented elements
• CPC Class Codes: G02B 13/0065 having a beam-folding prism or mirror
• CPC Class Codes: G02B 13/0085 employing wafer level optics
• CPC Class Codes: G02B 7/09 adapted for automatic focusing or varying magnification
• CPC Class Codes: G03B 13/36 Autofocus systems
• CPC Class Codes: G03B 17/17 with reflectors arranged in beam forming the photographic image, e.g. for reducing dimensions of camera
• CPC Class Codes: G03B 3/10 Power-operated focusing
• CPC Class Codes: H04N 23/16 Optical arrangements associated therewith, e.g. for beam-splitting or for colour correction
• CPC Class Codes: H04N 23/45 for generating image signals from two or more image sensors being of different type or operating in different modes, e.g. with a CMOS sensor for moving images in combination with a charge-coupled device [CCD] for still images
• CPC Class Codes: H04N 23/55 Optical parts specially adapted for electronic image sensors; Mounting thereof
• CPC Class Codes: H04N 23/67 Focus control based on electronic image sensor signals
• CPC Class Codes: H04N 23/698 for achieving an enlarged field of view, e.g. panoramic image capture
• CPC Class Codes: H04N 25/615 involving a transfer function modelling the optical system, e.g. optical transfer function [OTF], phase transfer function [PhTF] or modulation transfer function [MTF]
• CPC Class Codes: H04N 5/2624 for obtaining an image which is composed of whole input images, e.g. splitscreen
• CPC Class Codes: Y10T 29/49826 Assembling or joining

Abstract

An image capturing system and a method of autofocusing are disclosed such that, for example, when a folded optics configuration is used, a field corrector lens can be placed on the image sensor of the system and a plurality of lenses can be placed perpendicular to the image sensor. The plurality of lenses can be movable relative to the image sensor such that acceptable MTF curve performances can be obtained when the image capturing system is focused at reference distances.

Claims

1. An image capture system comprising:

a plurality of cameras configured to capture a corresponding plurality of portions of a target image scene, a camera of the plurality of cameras comprising;

an image sensor;

a primary light folding surface configured to redirect light representing one portion of the corresponding plurality of portions of the target image scene in a first direction toward the image sensor;

an optical element having an input surface configured to receive the light from the primary light folding surface, a secondary light folding surface configured to redirect the light in a second direction toward the image sensor, and an output surface through which light redirected by the secondary light folding surface propagates in the second direction toward the image sensor;

a lens assembly comprising;

a stationary portion having a first surface connected to the output surface of the optical element and a second surface connected to the image sensor, wherein the stationary portion of the lens assembly comprises a field corrector lens, and

a movable portion positioned between the primary light folding surface and the optical element;

an actuator configured to move the movable portion of the lens assembly along the first direction;

at least one guide rail coupled to the actuator and the movable portion of the lens assembly, the at least one guide rail positioned to slidably engage another surface within the camera to constrain motion of the movable portion of the lens assembly away from an optical axis or rotating around the optical axis, the optical axis substantially parallel to the first direction; and

a processor configured to generate a final image of the target image scene based at least partly on the corresponding plurality of portions.

2. The system of claim 1, further comprising:

a cover glass coupled between the image sensor and the stationary portion of the lens assembly, wherein the cover glass comprises a first cover glass surface coupled to the second surface of the stationary portion of the lens assembly and a second cover glass surface coupled to the image sensor;

wherein the first direction, output surface of the optical element, first surface of the stationary portion of the lens assembly, first cover glass surface, second cover glass surface are generally parallel to a plane formed by the image sensor;

wherein the optical element further comprises a guide surface extending generally parallel to the plane formed by the image sensor, the guide surface comprising the another surface within the camera which the at least one guide rail is positioned to slidably engage;

wherein the input surface of the optical element is generally perpendicular to the plane formed by the image sensor; and

wherein the secondary light folding surface extends at an angle between the guide surface of the optical element and the output surface of the optical element.

3. The system of claim 2, wherein the optical element, stationary portion of the lens assembly, cover glass, and image sensor are adhered into a stack.

4. The system of claim 1, further comprising a substrate, wherein the image sensor of each of the plurality of cameras is inserted into a slot in the substrate.

5. The system of claim 1, further comprising one or more of glides, interlocking grooves, a magnetic field, oil, ball bearings, air, gas, or water positioned in contact with one or both of the movable portion of the lens assembly and the at least one guide rail in order to reduce friction.

6. The system of claim 1, wherein the actuator is configured to move the movable portion of the lens assembly in the first direction within a space formed between an output surface of a prism comprising the primary light folding surface and the input surface of the optical element comprising the secondary light folding surface.

7. The system of claim 6, wherein motion of the movable portion of the lens assembly in the first direction within the space between a near focus position and a far focus position is approximately 180 micrometers or less.

8. The system of claim 6, wherein the near focus position corresponds to a focal distance of approximately 200 mm and the far focus position corresponds to a focal length of approximately 6767 mm.

9. The system of claim 1, wherein the movable portion of the lens assembly comprises a plurality of lenses affixed to one another.

10. The system of claim 1, wherein the primary light folding surface comprises one of a mirror and a refractive prism.

11. The system of claim 1, wherein the optical element comprises one of a mirror and a refractive prism.

12. The system of claim 1, further comprising an autofocus module storing instructions for focusing the movable portion of the lens assembly.

13. The system of claim 1, wherein the optical element is positioned between the movable portion of the lens assembly and the actuator.

14. The system of claim 13, wherein the at least one guide rail is coupled to a lower surface of the actuator at a first end and is coupled to a lower surface of the movable portion of the lens assembly at a second end.

15. The system of claim 1, wherein a pixel pitch of a pixel of the image sensor is 1.1 μ

m.

16. An image capture system comprising:

a plurality of cameras configured to capture a corresponding plurality of portions of a target image scene, a camera of the plurality of cameras comprising;

an image sensor;

a primary light folding surface configured to redirect light representing one portion of the corresponding plurality of portions of the target image scene in a first direction toward the image sensor;

an optical element having an input surface configured to receive the light from the primary light folding surface, a secondary light folding surface configured to redirect the light in a second direction toward the image sensor, and an output surface through which light redirected by the secondary light folding surface propagates in the second direction toward the image sensor;

a lens assembly comprising;

a stationary portion having a first surface coupled to the output surface of the optical element and a second surface coupled to the image sensor, and

a movable portion positioned between the primary light folding surface and the optical element;

an actuator configured to move the movable portion of the lens assembly along the first direction;

at least one guide rail coupled to the actuator and the movable portion of the lens assembly, the at least one guide rail positioned to slidably engage another surface within the camera to constrain motion of the movable portion of the lens assembly away from an optical axis or rotating around the optical axis, the optical axis substantially parallel to the first direction; and

a processor configured to generate a final image of the target image scene based at least partly on the corresponding plurality of portions,

wherein the actuator is configured to move the movable portion of the lens assembly in the first direction within a space formed between an output surface of a prism comprising the primary light folding surface and the input surface of the optical element comprising the secondary light folding surface, and

wherein the optical element comprises a refractive prism and further comprises a support block affixed to the refractive prism at the secondary light folding surface, a lower prism surface of the prism and a lower block surface of the support block comprising the another surface within the camera which the at least one guide rail is positioned to slidably engage.

17. An autofocus device for a folded optic imaging system having an image sensor and a primary light folding surface, the autofocus device comprising:

an optical element having an input surface configured to receive light from a primary light folding surface, a secondary light folding surface configured to redirect the received light in a second direction toward an image sensor, and an output surface through which light redirected by the secondary light folding surface propagates in the second direction toward the image sensor;

a lens assembly comprising;

a stationary portion having a first surface connected to the output surface of the optical element and a second surface connected to the image sensor, wherein the stationary portion of the lens assembly comprises a field corrector lens, and

a movable portion positioned in an optical path between the image sensor and the primary light folding surface;

a motor configured to move the movable portion of the lens assembly along an optical axis in a direction substantially parallel to a plane formed by the image sensor; and

at least one guide rail coupled to the motor and the movable portion of the lens assembly, the at least one guide rail positioned to slidably engage another surface within the folded optic imaging system to constrain motion, of the movable portion of the lens assembly, away from the optical axis or from rotating around the optical axis.

18. The autofocus device of claim 17, wherein the guide rail slidably engaging the another surface constrains motion of the movable portion of the lens assembly in the tilt, roll, pitch, and yaw rotational directions and in the linear X, Y, and Z directions.

19. The autofocus device of claim 17, wherein the motor comprises one of a voice coil motor, piezoelectric stepper motor, micro electrical mechanical system, or a shape memory alloy.

20. The autofocus device of claim 17, further comprising a cover glass affixed over a light receiving surface of the sensor, wherein the field corrector lens is coupled to the cover glass.

21. The autofocus device of claim 17, wherein a pixel pitch of a pixel of the image sensor is 1.1 μ

m.

22. An image capture apparatus comprising:

means for capturing a plurality of portions of a target image scene comprising a means for sensing; and

an optical element having an input surface configured to receive light from a primary light folding surface and an output surface through which light redirected by the optical element propagates towards the means for sensing;

the means for capturing further comprising

a lens assembly comprising

a stationary portion having a first surface connected to the output surface of the optical element and a second surface connected to the means for sensing, wherein the stationary portion of the lens assembly comprises a field corrector lens, and

a movable portion positioned between the means for sensing and the primary light folding surface;

means for moving the movable portion of the lens assembly; and

means for controlling motion of the movable portion of the lens assembly by slidably engaging at least one surface within the image capture apparatus.

23. The apparatus of claim 22, wherein the means for capturing a plurality of portions of a target image scene comprises a plurality of folded-optic cameras configured in an array.

24. The apparatus of claim 22, wherein a pixel pitch of a pixel of the means for sensing is 1.1 μ

m.