Thin ceramic imaging screen for camera systems

• US 10,120,111 B2
• Filed: 12/14/2016
• Issued: 11/06/2018
• Est. Priority Date: 12/14/2016
• Status: Active Grant

• Current Assignee: Google LLC (Alphabet Inc.)
• Original Assignee: Google LLC (Alphabet Inc.)
• Inventors: Berger, Jill D., Swain, Steven M., Liang, Tianran, Yasumura, Kevin Y.
• Primary Examiner(s): Velez, Roberto
• Assistant Examiner(s): Segura, Cynthia
• Application Number:
  US15/379,186
• Publication Number:
  US 20180164476A1
• Time in Patent Office: 692 Days
• CPC Class Codes: C03C 17/007 containing a dispersed phase, e.g. particles, fibres or flakes, in a continuous phase
• CPC Class Codes: C03C 2217/452 Glass
• CPC Class Codes: C03C 2217/485 Pigments
• CPC Class Codes: G02B 21/0016 Technical microscopes, e.g. for inspection or measuring in industrial production processes
• CPC Class Codes: G02B 26/0833 the reflecting element being a micromechanical device, e.g. a MEMS mirror, DMD G02B26/0825 takes precedence; micromechanical devices in general B81B
• CPC Class Codes: G02B 5/021 the diffusion taking place at the element's surface, e.g. by means of surface roughening or microprismatic structures
• CPC Class Codes: G02B 5/0242 by means of dispersed particles
• CPC Class Codes: G02B 5/0268 characterized by the fabrication or manufacturing method
• CPC Class Codes: G02B 5/0278 used in transmission
• CPC Class Codes: G02B 6/3512 the optical element being reflective, e.g. mirror
• CPC Class Codes: G02B 6/3556 NxM switch, i.e. regular arrays of switches elements of matrix type constellation
• CPC Class Codes: G02B 6/356 in an optical cross-connect device, e.g. routing and switching aspects of interconnecting different paths propagating different wavelengths to (re)configure the various input and output links switching polarized beams G02B6/3594; power equalizers G02B6/356 and G02B6/3594; path selecting means H04Q11/0001
• CPC Class Codes: G02B 6/359 of the position of the moving element itself during switching, i.e. without monitoring the switched beams
• CPC Class Codes: H04N 23/51 Housings
• CPC Class Codes: H04N 25/76 Addressed sensors, e.g. MOS or CMOS sensors

Abstract

An apparatus and a camera system are provided. The apparatus includes an imaging screen configured to diffuse incoming light, and a lens system coupled to the imaging screen and configured to focus light from the imaging screen onto a CMOS image sensor. The imaging screen includes a ceramic diffuser layer fused into a surface of a glass substrate, and a thickness of the ceramic diffuser layer is within a range of about 7-10 μm.

Claims

1. An apparatus comprising:

an imaging screen configured to diffuse incoming light; and

a lens system coupled to the imaging screen and configured to focus light from the imaging screen onto a CMOS image sensor, wherein;

the imaging screen comprises a ceramic diffuser layer directly fused into a surface of a glass substrate such that no gap exists between the ceramic diffuser layer and the glass substrate, and

a thickness of the ceramic diffuser layer is within a range of about 7-10 μ

m.

2. The apparatus of claim 1, wherein the ceramic diffuser layer comprises a bismuth-based glass frit and at least one inorganic pigment, including one of silicon dioxide (SiO2), zinc oxide (ZnO), diboron trioxide (B2O3), sodium oxide (Na2O), and bismuth oxide (BiO2).

3. The apparatus of claim 1, wherein a thermal expansion coefficient (CTE) of the ceramic diffuser layer has a value within about 8% of a CTE value of the glass substrate.

4. The apparatus of claim 1, further comprising a stainless steel housing coupled to and surrounding the imaging screen using a glass layer including a soda lime float glass material.

5. The apparatus of claim 4, wherein a thermal expansion coefficient (CTE) of the ceramic diffuser layer has a value within about 10-20% of a CTE value of the stainless steel housing, and wherein a CTE value of the glass substrate is within about 6-7% of the CTE value of the stainless steel.

6. The apparatus of claim 1, wherein the imaging screen is configured to be thermally stable within a predefined operating temperature range to enable thermal stability of pixel-to-pixel separation of an image formed on the CMOS image sensor.

7. The apparatus of claim 1, further comprising a processor coupled to the CMOS image sensor, wherein the processor is configured to process an output signal of the CMOS image sensor to determine positions of respective mirrors of an array of MEMS mirrors of an optical circuit switch.

8. The apparatus of claim 1, wherein the glass substrate comprises a soda lime float glass substrate, and wherein the soda lime float glass substrate comprises a low-iron glass substrate.

9. The apparatus of claim 1, wherein surface flatness of the glass substrate is characterized by a peak-to-valley value of about λ

/4 at a wavelength (λ

) of about 633 nm.

10. A camera system for monitoring micro electro-mechanical system (MEMS) mirrors, the camera system comprising:

a diffuser comprising a ceramic diffuser layer directly fused into a first surface of a glass substrate such that no gap exists between the ceramic diffuser layer and the glass substrate;

an optical block configured to concentrate light emitted by the diffuser;

an image sensor configured to receive concentrated light from the optical block and to generate electrical signals; and

a processor coupled to the image sensor and configured to produce an image of beams reflected from the MEMS mirrors based on the electrical signals,

wherein a thermal expansion coefficient (CTE) of the ceramic diffuser layer has a value within about 8% of a CTE value of the glass substrate.

11. The camera system of claim 10, wherein a thickness of the ceramic diffuser layer is within a range of about 7-10 μ

m.

12. The camera system of claim 10, wherein the ceramic diffuser layer comprises a bismuth-based glass frit and at least one inorganic pigment, including one of silicon dioxide (SiO2), zinc oxide (ZnO), diboron trioxide (B2O3), sodium oxide (Na2O), and bismuth oxide (BiO2).

13. The camera system of claim 10, further comprising stainless steel housing coupled to and surrounding the diffuser using a glass layer including a soda lime float glass, and wherein a thermal expansion coefficient (CTE) of the ceramic diffuser layer has a value within about 10-20% of a CTE value of the stainless steel housing, and wherein a CTE value of the glass substrate is within about 6-7% of the CTE value of the stainless steel.

14. The camera system of claim 10, wherein the image sensor is coupled to the processor and comprises a CMOS image sensor with pixel size of about 6 μ

m.

15. The camera system of claim 10, wherein the processor is configured to process the electrical signals to determine positions of respective mirrors of an array of MEMS mirrors of an optical circuit switch.

16. The camera system of claim 10, wherein the diffuser is configured to be thermally stable within a predefined operating temperature range to enable thermal stability of pixel-to-pixel separation of an image of the beams reflected from the MEMS mirrors.

17. The camera system of claim 10, wherein the glass substrate comprises a low-iron soda lime float glass substrate.

18. The camera system of claim 10, wherein the optical block comprises a plurality of lenses configured to have a negative magnification and to concentrate lights from a diffuser spot with a size of about 54 μ

m into an image sensor pixel of about 6 μ

m.

19. The camera system of claim 10, wherein a thickness of the glass substrate is within a range of about 3-4 mm.

20. The camera system of claim 10, wherein the glass substrate has a surface flatness characterized by a peak-to-valley value of about λ

/4 at a wavelength (λ

) of about 633 nm.