Demonstration of a novel drift field pixel structure for the demodulation of modulated light waves with application in three-dimensional image capture

A Time-of-Flight 3-D Image Sensor With Concentric-Photogates Demodulation Pixels

“…A closer look at the previous device, however, exhibits a two-tap architecture with a single photogate, and ring-gates surrounding FDs with a 100 μm pitch; the device architecture described in [12] is more similar to that described [4] or [9]. The working principle and pixel structure of our CG pixel is entirely different in that independent implementation of the IG and DG for each pixel suppresses interpixel cross talk, while the photogate is shared by all pixels in the device reported in [12].…”

“…Through proper operation of the nodes "cb" and "clamp," pseudo-CDS from "sampsig" and "samprst" is executed. With an appropriate application of biases to V 1 , V 2 , V 3 , V 4 , and enabling reset of column source followers with "rstsf," the analog signal is differentially read at "voutpos" and "voutneg" as V pos and V neg , respectively. Finally, the signal output is obtained as…”

Improved measurement linearity and precision for AMCW time-of-flight range imaging cameras

“…Lange [1] describes the case where the illumination source is modulated with a sinusoidal waveform, while the image sensor is modulated with a square wave with 50% duty cycle, resulting in a maximum possible demodulation contrast value of sincð0:5Þ ¼ 0:64, where the term sincðxÞ is used to refer to the normalized sinc function, i.e., sincðxÞ ¼ sinðπxÞ=ðπxÞ. Similarly, a maximum demodulation contrast of 0.90 can be achieved if the image sensor is modulated with a 25% duty cycle rectangular waveform [1,10].…”

“…Time-of-flight range imaging is an emerging technology [1][2][3][4][5][6][7][8][9][10][11] that produces a "distance image" of a scene, where each pixel in the image not only contains intensity information, but also the range (or distance) from the camera to the object. A threedimensional reconstruction of the scene can be generated from the captured data, providing the opportunity to measure the location, size, and shape of objects-attributes that are highly desirable in a wide array of applications, such as machine vision, surveying, medical imaging, surface profiling, and human-machine interaction.…”

“…This improves the efficiency of the system as all the light reflected from the scene is collected by the image sensor (as opposed to the hardware used here, which discards the light during the off period). Similarly, specialized image sensors have been produced where each pixel collects and stores four samples simultaneously (known as four-tap pixels) [1,10,22], again still collecting all the reflected light from the scene, but in this instance with 25% duty cycle gain modulation. These systems can, therefore, (theoretically) produce higher demodulation contrast values up to 0.90.…”