Systems for CMOS-compatible three-dimensional image sensing using quantum efficiency modulation
First Claim
1. A system to determine distance z between at least one photodetector, and a target, the system comprising:
- a source of optical energy that emits a modulated periodic waveform having high frequency component S1(ω
·
t);
a plurality of photodetectors, disposed to detect a fraction of said optical energy reflected from said target; and
means for modulating quantum efficiency of said photodetector to process photodetector detected signals to yield data proportional to said distance z.
3 Assignments
0 Petitions
Accused Products
Abstract
A preferably CMOS-implementable system measures distance and/or brightness by illuminating a target with emitted optical energy having a modulated periodic waveform whose high frequency component may be idealized as S1=cos(ω·t). A fraction of the emitted optical energy is reflected by a target and detected with at least one in a plurality of semiconductor photodetectors. Photodetector quantum efficiency is modulated to process detected signals to yield data proportional to the distance z separating the target and photodetector. Detection includes measuring phase change between the emitted optical energy and the reflected fraction thereof. Quantum efficiency can be modulated with fixed or variable phase methods and may be enhanced using enhanced photocharge collection, differential modulation, and spatial and temporal multiplexing. System power requirements may be reduced with inductors that resonate with photodetector capacitance at the operating frequency. The system includes on-chip photodetectors, associated electronics, and processing.
-
Citations
37 Claims
-
1. A system to determine distance z between at least one photodetector, and a target, the system comprising:
-
a source of optical energy that emits a modulated periodic waveform having high frequency component S1(ω
·
t);
a plurality of photodetectors, disposed to detect a fraction of said optical energy reflected from said target; and
means for modulating quantum efficiency of said photodetector to process photodetector detected signals to yield data proportional to said distance z. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18)
circuitry to measure a change in phase between optical energy emitted by said source of optical energy, and a signal detected by said photodetectors;
banks of said photodetectors;
wherein said means for modulating modulates said banks of said photodetectors with different phases.
-
-
11. The system of claim 1, wherein said photodetectors are formed on a semiconductor substrate;
- and
further including means for creating an electrical current in said substrate to promote collection of photocharges released within said substrate by reflected said optical energy;
wherein quantum efficiency modulation is enhanced.
- and
-
12. The system of claim 1, wherein:
said photodetectors are formed on a semiconductor substrate including an epitaxial region, said epitaxial region of said substrate has at least one characteristic selected from (i) said epitaxial region comprises a plurality of layers each having a different doping concentration, wherein an uppermost one of said layers is less highly doped than a lower one of said layers, (ii) said epitaxial region defines a layer in which there is a dopant gradient such that doping concentration is greater at a lower portion of said region than at an upper portion thereof.
-
13. The system of claim 1, further including:
-
an inductor coupled so as to detune at least a fraction of capacitance coupled to a voltage node of said photodetectors controlling quantum efficiency modulation thereof;
wherein power dissipation of said capacitance is reduced.
-
-
14. The system of claim 1, further including:
-
a first bank of said photodetectors;
a second bank of said photodetectors;
said means for modulating being quantum efficiency modulating said first bank and said second bank with a constant phase;
at least one pixel comprising a photodetector from said first bank and a photodetector from said second bank;
wherein said circuit processes an output from one said photodetector for use by more than one said pixel.
-
-
15. The system of claim 1, wherein:
-
said system determines distance z over multiple time frames; and
on a per frame basis, said means for modulating quantum efficiency modulates said photodetector with at least a first phase shift, and acquires information from said photodetector during said first phase shift; and
information acquired from said photodetector during said first phase shift is used in at least two said time frames.
-
-
16. The system of claim 1, further including means for digitizing an analog output from each said photodetector.
-
17. The system of claim 1, wherein said frequency ω
- is at least 100 MHz.
-
18. The system of claim 1, wherein emitted said optical energy has a wavelength of about 850 nm.
-
19. A CMOS-implementable integrated circuit to measure distance z between a source of optical energy controlled by said system and a target, said integrated circuit comprising:
-
a generator, coupleable to a source of said optical energy that emits a modulated periodic waveform having high frequency component S1(ω
·
t);
a plurality of photodetectors, disposed to detect a fraction of said optical energy reflected from said target; and
means for modulating quantum efficiency of said photodetector to process photodetector detected signals to yield data proportional to said distance z. - View Dependent Claims (20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37)
circuitry to measure a change in phase between optical energy emitted by said source of optical energy, and a signal detected by said photodetectors;
banks of said photodetectors;
wherein said means for modulating modulates said banks of said photodetectors with different phases.
-
-
28. The integrated circuit of claim 19, further including:
-
means for creating an electrical current in said substrate to promote collection of photocharges released within said substrate by reflected said optical energy;
wherein quantum efficiency modulation is enhanced.
-
-
29. The integrated circuit of claim 19, further including:
-
a bias circuit to create an electrical current in said substrate to promote collection of photocharges released within said substrate by reflected said optical energy;
wherein quantum efficiency modulation is enhanced.
-
-
30. The integrated circuit of claim 19, wherein said photodetectors are formed on a semiconductor substrate including an epitaxial region, said epitaxial region of said substrate has at least one characteristic selected from (i) said epitaxial region comprises a plurality of layers each having a different doping concentration, wherein an uppermost one of said layers is less highly doped than a lower one of said layers, (ii) said epitaxial region defines a layer in which there is a dopant gradient such that doping concentration is greater at a lower portion of said region than at an upper portion thereof.
-
31. The integrated circuit of claim 19, further including:
-
an inductor coupled so as to detune at least a fraction of capacitance coupled to a voltage node of said photodetectors controlling quantum efficiency modulation thereof;
wherein power dissipation of said capacitance is reduced.
-
-
32. The integrated circuit of claim 19, further including:
-
a first bank of said photodetectors;
a second bank of said photodetectors;
said means for modulating being quantum efficiency modulating said first bank and said second bank with a constant phase;
at least one pixel comprising a photodetector from said first bank and a photodetector from said second bank;
wherein said circuit processes an output from one said photodetector for use by more than one said pixel.
-
-
33. The integrated circuit of claim 19, wherein:
-
said system determines distance z over multiple time frames; and
on a per frame basis, said means for modulating quantum efficiency modulates said photodetector with at least a first phase shift, and acquires information from said photodetector during said first phase shift; and
information acquired from said photodetector during said first phase shift is used in at least two said time frames.
-
-
34. The integrated circuit of claim 19, further including a microprocessor controlling operation of at least said means for modulating.
-
35. The integrated circuit of claim 19, further including means for digitizing an analog output from each said photodetector.
-
36. The integrated circuit of claim 19, wherein said frequency ω
- is at least 100 MHz.
-
37. The integrated circuit of claim 19, wherein emitted said optical energy has a wavelength of about 850 nm.
Specification