Method of reading image signal from image senser

Abstract

The method first selects up the scan line in turn frmo image, the selected scan line scans each pixel at column scan frequency; the low pass filter whose cut-off frequency is Wn is made for each column pixel; the A/D conversion is made for the signal filtered with low pass filter. By using the invention, the cut-off frequency-Wn is much lower than column scan frequency, the frequency of A/D conversion also much lower than column scan frequency, so that the circuit can implement a high speed image acquisition with a low speed A/D conversion.

Description

technical field [0001] The invention relates to a method for reading out image signals of an image sensor and a circuit thereof, and belongs to the technical field of complementary metal oxide semiconductor (hereinafter referred to as CMOS) image sensors. Background technique [0002] The CMOS image sensor obtains a complete image by scanning and reading out the brightness information of each pixel. In the existing CMOS image sensor, the image signal is obtained by scanning the pixels in rows and columns, and then performing analog-to-digital conversion on the scanned pixel signal. With the improvement of the resolution and image acquisition speed of CMOS image sensors, the traditional readout method requires high-frequency analog-to-digital conversion, that is, an analog-to-digital converter with a high sampling frequency is required for circuit implementation. In order to reduce the frequency of A / D conversion, there are many methods to simultaneously perform A / D conversi...

AI Technical Summary

Problems solved by technology

The method of multi-analog-to-digital conversion requires many analog-to-digital converters when the circuit is implemented, which not only increases the power consumption and area of ​​the circuit, but also increases the cost

At the same time, due to the increase of other areas of the circuit, the light-receiving area of ​​each pixel will inevitably be reduced, which will greatly reduce the sensitivity of the CMOS image sensor and affect the quality of image acquisition.

Obviously, the shortcomings of this method are not suitable for the development of modern CMOS large-scale and VLSI towards high-speed and low-power consumption, especially for various mobile electronic devices, such as visual communication mobile phones, various cameras, etc.

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