Pseudo-BJT based retinal focal-plane sensing system

• US 20050018062A1
• Filed: 07/23/2003
• Published: 01/27/2005
• Est. Priority Date: 07/23/2003
• Status: Active Grant

• Current Assignee: Alfaplus Semiconductor Incorporated
• Original Assignee: Alfaplus Semiconductor Incorporated
• Inventors: Chiang, Cheng-Ta, Wu, Chung-Yu
• Granted Patent: US 7,215,370 B2
• Time in Patent Office: Days
• US Class Current: 348/294
• CPC Class Codes: H04N 25/60 Noise processing, e.g. detecting, correcting, reducing or removing noise
• CPC Class Codes: H04N 25/74 Circuitry for scanning or addressing the pixel array
• CPC Class Codes: H04N 25/77 Pixel circuitry, e.g. memories, A/D converters, pixel amplifiers, shared circuits or shared components

Abstract

A Pseudo Bipolar Junction Transistor(Pseudo-BJT) based retinal focal-plane sensing system is an instant image sensing and front-end processing system with the advantages of high dynamic range and instant image processing. In addition, the system proposes a Pseudo-BJT based retinal focal-plane sensor with adaptive current Schmitt trigger and smoothing network for applying a new Pseudo-BJT circuit structure to mimic parts of functions of the cells in the outer plexiform layer of the real retina. It is suitable to resolve the existing technical drawbacks performing major functions in optical image detecting circuits, such as image recognition, image tracing, robot vision, bar-code/character readers, etc.

Claims

1. A Pseudo-BJT based retinal focal-plane sensing system, which mimics the three cell functions of P cell, H cell and B cell in a single pixel, and performs image sensing effect, comprising:

a row decoder, used for detecting external images, randomly selecting desired pixel and generating a row address;

a column decoder, used for detecting external images, randomly selecting desired pixel and generating a column address;

a pixel array module, used for reading pixels and detecting external images;

in addition, outputting pixel voltages appointed by the row decoder and the column decoder one by one;

wherein a voltage is generated when an image signal is received by the row address and the column address;

a data buffer, used for converting the parallel data to serial data in order to reduce output pins of the chip;

a circuit for current hysteresis, used for eliminating noise disturbance and adjusted adaptively according to the value of induced photocurrent, which enhances noise immunity and eliminate noise disturbance; and

a resistance circuit, having the function of Low-Pass Filter enabling high frequency noise to be eliminated with high tunable capability.

2. The Pseudo-BJT based retinal focal-plane sensing system of claim 1, wherein the P cell is to do photo-input sensing lacking the function of eliminating noise disturbance.

3. The Pseudo-BJT based retinal focal-plane sensing system of claim 1, wherein the H cell is to smooth an image retrieved by P cell with the Low-Pass Filter function enabling partial high frequent noise to be eliminated.

4. The Pseudo-BJT based retinal focal-plane sensing system of claim 1, wherein the B cell is to balance both outputs of P cell and H cell to attain edge detection and have the function of eliminating noise disturbance.

5. The Pseudo-BJT based retinal focal-plane sensing system of claim 1, wherein the Pixel Array Module can be a 32×

32 pixel array.

6. The Pseudo-BJT based retinal focal-plane sensing system of claim 1, wherein the retinal focal-plane sensor adopts MOSFET transistors.

7. The Pseudo-BJT based retinal focal-plane sensing system of claim 1, being applied to image recognition, image tracing, robot vision, optical image detecting circuits of bar-code or character readers.

8. The Pseudo-BJT based retinal focal-plane sensing system of claim 1, wherein the circuit for current hysteresis is an adaptive current Schmitt trigger.

9. The Pseudo-BJT based retinal focal-plane sensing system of claim 1, wherein the resistance circuit is a smoothing network circuit.

10. A Pseudo-BJT retinal focal-plane circuit, comprising

a Photodiode D0, two Pseudo-BJTs, four adjustable N-channel MOS resistors of the smoothing network as Ms1-Ms4, a set of adaptive current Schmitt trigger comprising Mnf1-Mnf2 and Mpf1-Mpf2, an Inverter comprising transistors Mn and Mp, row and column controlled switch transistors, Pseudo-BJT P cells comprising Mp1 and Mp2, and Pseudo-BJT H cells comprising Mn1 and Mn2;

wherein the Photodiode DO is detected and photocurrent is then generated, incorporating Mp1 and MP2 for the P cell to process;

Mn1 and Mn2(H cell) are used for incorporating with smoothing network, Ms1-Ms4 to activate the image smoothing function;

the electric resistance of four MOS resistors is controlled by the gate voltage Vsmooth(VF) with the Low-Pass Filter function enabling partial high frequent noise to be eliminated;

Mp2 and Mn2 have the connection between thereof activating the B cell functions;

the adaptive current Schmitt trigger is composed of Mnf1-Mnf2 and Mpf1-Mpf2 for eliminating noise disturbance;

an outputted Inverter converts analogue signals into digital signals; and

the Row and Column controlled switch transistors are controlled by the Row and Column Decoders, thereby only appointed pixels are able to output signals (Retina_out).