CMOS Time-of-Flight Range Image Sensors

Transcript

1 CMOS Time-of-Flight Range Image Sensors Shoji KAWAHITO This article describes CMOS time-of-flight TOF range image sensors and their pixel devices, so-called lock-in pixels. The CMOS-TOF range image sensors are categorized into two types; direct and indirect TOF measurement types. The direct TOF measurement uses a direct measurement of photon arrival timing using a single photon avalanche diode SPAD and a precise time-to-digital converter. In the indirect TOF measurement, the TOF is estimated by a mechanism of time-dependent photo charge modulation. Sinusoidal or pulsed light modulations are used for phase or delay measurements by demodulating it in the lock-in pixels. Lock-in pixels are realized with CCD-like devices implemented based on CMOS technologies or device structures compatible with standard CMOS image sensor technology or a little modification of it. Recent trend shows that pinned photodiodes based lock-in pixels in standard CMOS technology are becoming popular. This article discusses the principle, operation and performance of these TOF range imaging methods and devices and their performance limitations. Key words: time of flight measurement, single photon avalanche diode, charge demodulation pixel, lock-in pixel, CMOS image sensor CMOS time of flight TOF CMOS complementary metal oxide semiconductor CMOS-TOF CMOS TOF TOF TOF TOF TOF SPAD single photon avalanche diode TDC time to digital converter TOF CMOS-TOF 1. TOF TOF 100 ps TOF kawahito@idl.rie.shizuoka.ac.jp 262 2

2 1 SPAD single-photon avalanche diode a b c SPAD pn TOF SPAD single photon avaranche diodespad 1 1 SPAD V bd 1 SPAD V bd p MOSFET quenting CMOS SPAD SPAD 1 c CMOS n-well p pn p p-well TOF TDC SPAD CMOS TDC 2 SPAD TDC 1 a S TDC 2 TDC RS SPAD RS TOF TOF 1 mm 263 3

3 3 2 TDC a b TOF 6.6 ps 150 GHz CMOS 2 TDC coarse 1 fine TDC TDC 1 10 ps 10 ps TOF ps 1.8 mm 1 SPAD TOF TDC TOF 2 10 TDC 3 TDC DLL delay locked loop 2 SPAD TOF TDC TDC SPAD TOF 2. TOF TOF TOF CCD 3 2 1, 2 2 1, L t d c L 1/2 ct d 2

4 a 0, a 1, a 2, a 3 j ϕ arctan a a a a t d j /2p f m f m B TOF 5 1 CMOS 5 CCD CCD- CMOS PGM PGL PGR PGL PGR IG a 0, a 1, a 2, a mm 21 mm TOF 2.5 pw 20 MHz 2 cm 5 2-tap 0.6 mm mm 40 mm TOF 6 2-tap 5 PGR IG OUTG 1.2 m 5 mm CCD CMOS TOF CMOS 6 CMOS CMOS-TOF 7 b 3 1 n FD1, FD2 ktc 6 a TXD 265 5

5 7 6 CMOS a b X-X 7 7 TX1 TX2 PG FD1, FD2 TXD CMOS mm 15 mm CMOS-TOF 25 ns 30 frames/s 1 V 5 mm 10 3 frames/s 2 mm CMOS 2 PMD photo mixing device 2-tap a 2 2-tap p- 8 CMOS 8 CMOS a photogate b pinned photodiode

6 9 pinned photodiode b 2-tap TOF L ct d /2 cj /4p f m B A A B N s A 2N s L N b N r i 3 L ai a 0 L L 8 N s B B N N N m 5 mm i 2 B 3 A N b 2 s b r 5 CCD IG FD CDS correlated double sampling 6 8 CMOS N reset N reset 2 V V 4 V th 26 mv V s N well V s 1 V N well 200,000 N well CMOS TOF CCD 9 3. CMOS-TOF LED th s N well

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