The Circuit Design of Current-Mode Image Sensor Embedded Smooth Spatial Filter With Flash A/D Converter

The paper presents a current-mode CMOS image sensor embedded smooth spatial filter algorithm with a flash analog-to-digital (A/D) converter. The sensor includes a 66×66 pixel array with an on-chip 6-bit A/D converter that can identify the output value of pixels in gray level resolution. The last row of pixel cells (1 ×66) based on the double sampling is used for reducing fixed pattern noise (FPN). Processing circuits are dedicated for the spatial filter algorithm and support reusability to increase the image processing speed and to reduce the design complexity and chip area. The sensor chip has been designed and implemented in TSMC 0.35μm 2P4M CMOS mixed-mode process. Experimental results show that each pixel occupies a area of 15.8μm×10.6μm with a fill factor of 37.2%. The power consumption is 35.15mW when the sensor operates at 175 frames/second. Key-Words: Image senser, smooth spatial filter, Flash A/D converter, pixel cell, CMOS process.