Imaging optical system for 3D image acquisition apparatus, and 3D image acquisition apparatus including the imaging optical system

• US 9,402,067 B2
• Filed: 10/22/2013
• Issued: 07/26/2016
• Est. Priority Date: 10/22/2012
• Status: Active Grant

• Current Assignee: Samsung Electronics Co. Ltd.
• Original Assignee: Samsung Electronics Co. Ltd.
• Inventors: Park, Yong-hwa, Gorelov, Alexander, You, Jang-woo, Shirankov, Alexander, Lee, Seung-wan
• Primary Examiner(s): Ho, Tuan
• Application Number:
  US14/059,825
• Publication Number:
  US 20140111620A1
• Time in Patent Office: 1,008 Days
• US Class Current: 1/1
• CPC Class Codes: G02B 27/1006 for splitting or combining different wavelengths G02B27/1086, G02B27/141 take precedence
• CPC Class Codes: G02B 3/08 with discontinuous faces, e.g. Fresnel lens diffractive Fresnel lenses G02B5/1876
• CPC Class Codes: H04N 13/239 using two 2D image sensors having a relative position equal to or related to the interocular distance H04N13/243 takes precedence
• CPC Class Codes: H04N 13/271 wherein the generated image signals comprise depth maps or disparity maps

Abstract

An imaging optical system and a three-dimensional (3D) image acquisition apparatus which includes the imaging optical system are provided. The imaging optical system includes an object lens configured to transmit light; first and second image sensors having different sizes from each other; a beamsplitter on which the light transmitted by the object lens is incident, the beamsplitter being configured to split the light incident thereon into light of a first wavelength band and light of a second wavelength band, and to direct the light of the first wavelength band to the first image sensor and the light of the second wavelength band to the second image sensor; and at least one optical element, disposed between the beamsplitter and the second image sensor, configured to reduce an image that is incident on the second image sensor, the optical element including at least one of a Fresnel lens and a diffractive optical element.

Claims

1. An imaging optical system comprising:

an object lens configured to focus light;

first and second image sensors, wherein a size of the second image sensor is different from a size of the first image sensor;

a beamsplitter on which the light focused by the object lens is incident, wherein the beamsplitter is configured to split the light incident thereon into light of a first wavelength band and light of a second wavelength band, direct the light of the first wavelength band to the first image sensor, and direct the light of the second wavelength band to the second image sensor; and

at least one optical element disposed between the beamsplitter and the second image sensor, wherein the at least one optical element is configured to reduce an image that is incident on the second image sensor,

wherein the at least one optical element comprises at least one of a Fresnel lens and a diffractive optical element (DOE).

2. The imaging optical system of claim 1, wherein the at least one optical element comprises at least two of the Fresnel lenses that are sequentially disposed along an optical path between the beamsplitter and the second image sensor.

3. The imaging optical system of claim 1, wherein the at least one optical element comprises the Fresnel lens and the DOE that are sequentially disposed along an optical path between the beamsplitter and the second image sensor, and

wherein the Fresnel lens is a collimating element that converts light reflected from the beamsplitter into parallel light, and the DOE reduces an image by converging the parallel light onto the second image sensor.

4. The imaging optical system of claim 1, further comprising an optical shutter that is disposed between the at least one optical element and the second image sensor and is configured to modulate the light of the first wavelength band and provide the modulated light to the second image sensor.

5. The imaging optical system of claim 1, wherein the size of the second image sensor is smaller than the size of the first image sensor, and the light of the first wavelength band comprises visible light and the light of the second wavelength band comprises infrared light.

6. The imaging optical system of claim 1, wherein the beamsplitter is configured to transmit the light of the first wavelength band and reflect the light of the second wavelength band.

7. The imaging optical system of claim 1,

wherein the beamsplitter is inclined by more than about 45 degrees with respect to an optical axis of the object lens.

8. The imaging optical system of claim 7, wherein the beamsplitter comprises:

a plurality of first slopes that are formed on a light-incident surface of the beamsplitter and are each inclined by about 45 degrees with respect to the optical axis of the object lens; and

a plurality of second slopes that are formed on a light-exit surface of the beamsplitter and have complementary shapes with respect to the plurality of first slopes,

wherein the plurality of first slopes and the plurality of second slopes are parallel to each other.

9. The imaging optical system of claim 8, wherein the beamsplitter further comprises a wavelength separation filter configured to transmit the light of the first wavelength band and reflect the light of the second wavelength band, and the wavelength separation filter is coated on the plurality of first slopes.

10. The imaging optical system of claim 7, wherein the beamsplitter comprises:

reflective first diffraction patterns that are formed on a light-incident surface of the beamsplitter, wherein the reflective first diffraction patterns are configured to transmit the light of the first wavelength band and reflect the light of the second wavelength band, and are positioned so that a reflection angle of the reflected light of the second wavelength band is about 45 degrees with respect to the optical axis of the object lens; and

second diffraction patterns that are formed on a light-exit surface of the beamsplitter and have complementary shapes with respect to the reflective first diffraction patterns.

11. The imaging optical system of claim 1,

wherein the beamsplitter has a concave reflective surface coated with a wavelength separation filter which is configured to transmit the light of the first wavelength band and reflect the light of the second wavelength band.

12. The imaging optical system of claim 11, further comprising a convex minor configured to reflect the light of the second wavelength band light reflected by the beamsplitter, and a flat minor configured to reflect, toward the second image sensor, the light of the second wavelength band light reflected by the convex minor.

13. The imaging optical system of claim 11, further comprising a flat mirror configured to reflect the light of the second wavelength band reflected by the beamsplitter, and a convex minor configured to reflect, toward the second image sensor, the light of the second wavelength band reflected by the flat minor.

14. The imaging optical system of claim 1,

wherein the beamsplitter comprises a first dichroic minor and a second dichroic minor which are disposed in an upper region and a lower region, respectively, with respect to an optical axis of the object lens,

the first dichroic minor and the second dichroic minor partially contact each other along the optical axis, and a reflective surface of the first dichroic mirror forms a predetermined angle with respect to a reflective surface of the second dichroic minor,

the first dichroic minor is configured to transmit the light of the first wavelength band and reflect the light of the second wavelength band toward the upper region, and

the second dichroic minor is configured to transmit the light of the first wavelength band and reflect the light of the second wavelength band toward the lower region.

15. The imaging optical system of claim 14, further comprising:

a first mirror that is disposed to face the first dichroic mirror and is configured to reflect, toward the second image sensor, the light of the first wavelength band reflected by the first dichroic minor; and

a second mirror that is disposed to face the second dichroic mirror and is configured to reflect, toward the second image sensor, the light of the first wavelength band reflected by the second dichroic minor.

16. The imaging optical system of claim 15, wherein reflective diffraction patterns having an image reduction function are formed on a reflective surface of the first mirror and a reflective surface of the second minor.

17. The imaging optical system of claim 1, further comprising:

a fiber optic taper disposed between the beamsplitter and the second image sensor, wherein an area of a light-incident surface of the fiber optic taper is greater than an area of a light-exit surface of the fiber optic taper.

18. The imaging optical system of claim 17, wherein the at least one optical element comprises the Fresnel lens which is configured to convert light from the beamsplitter into parallel light, and wherein the fiber optic taper is configured to reduce an image by converging the parallel light onto the second image sensor.

19. The imaging optical system of claim 17, wherein the at least one optical element comprises the Fresnel lens which is configured to convert light from the beamsplitter into parallel light, and the DOE which is configured to reduce an image by converging the parallel light, and wherein the fiber optic taper is configured to additionally reduce the image which is reduced by the DOE.

20. A three-dimensional (3D) image acquisition apparatus comprising:

an imaging optical system comprising;

an object lens configured to transmit light;

first and second image sensors, wherein a size of the second image sensor is different from a size of the first image sensor;

a beamsplitter on which the light transmitted by the object lens is incident, wherein the beamsplitter is configured to split the light incident thereon into light of a first wavelength band and light of a second wavelength band, direct the light of the first wavelength band to the first image sensor, and direct the light of the second wavelength band to the second image sensor; and

at least one optical element disposed between the beamsplitter and the second image sensor, wherein the at least one optical element is configured to reduce an image which is incident on the second image sensor,

wherein the at least one optical element comprises at least one of a Fresnel lens and a diffractive optical element (DOE);

a light source configured to generate light of the second wavelength band light and irradiate the light of the second wavelength band onto a target object;

an image signal processor (ISP) configured to generate a 3D image by using an image output from the first image sensor and an image output from the second image sensor; and

a control unit configured to control operations of the light source and the ISP.