JPS61187467A - Image sensor - Google Patents

Abstract

PURPOSE:To use a defective line image sensor in the same way as a nondefective sensor by discriminating a defective photodetector depending on the difference from output levels of adjacent photodetectors and using an output of the adjacent photodetector in place of the output of the defective photodetector to apply interpolation. CONSTITUTION:A output of a photodetector array 1 is inputted sequentially to an A/D converting circuit 2 synchronously with a reference clock, converted into an N-bit digital signal and stored in a latch circuit 3 by using a latch clock signal 32. The N-bit digital output of the latch circuit 3 is inputted to one input terminal 72 of an absolute value subtraction circuit 7, and an N-bit digital output of the photodetector array before on reference clock time stored in the latch circuit 6 is inputted to an input terminal 71. The absolute value is compared with an N-bit digital setting value of a setting device by a comparator circuit 8 and when the absolute difference is larger than the setting value, the signal inputted to the input terminal 51 is selected in the two N-bit digital signals inputted to the selection circuit 5. The selected signal is inputted to a latch circuit 6, stored by using a latch clock signal 62 and an image sensor output is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an image sensor having a sensor interpolation function for correcting defects in light receiving elements constituting a line image sensor.

Conventional technology Generally, when using a line image sensor, phenomena such as shading, variation in output between pixels, and fluctuation in peak value occur due to variations in sensitivity of each light receiving element that makes up the line sensor. Several pre-processing methods have been devised (for example, Journal of the Institute of Image Electronics Engineers, Vol. 13, No. 2).

However, if there is a defect in the light-receiving element of a line image sensor and no signal is output from the light-receiving element, the current situation is that it is not dealt with in pre-processing and is treated as a defective product in the shipping inspection process and is sorted out. be. On the other hand, the number of light-receiving elements that make up a line image sensor is increasing due to higher resolution, etc., and as a result, the defective rate of line image sensors due to defects in the light-receiving elements is high, resulting in poor yields and resulting costs. It was also high.

Problems to be Solved by the Invention As described above, in the conventional method, even a mildly defective product, such as one having a defect in one light-receiving element, was rejected. The present invention has been made in view of the above, and an object of the present invention is to provide an image sensor equipped with a sensor interpolation function that allows defective products with minor defects to be used in the same way as good products.

Means for Solving the Problems In order to solve the above problems, the present invention compares the output signal of each light-receiving element with the output signal of an adjacent light-receiving element, and detects a defective light-receiving element based on the difference in output level. As a result, if there is a defect in the light receiving element, the output signal is interpolated with the output signal of the adjacent light receiving element.

In a high-resolution line image sensor, the distance between the light-receiving elements is short, and due to the MTF characteristics of the optical system that forms an image on the line image sensor, the amount of light input between adjacent light-receiving elements changes rapidly. If the output changes rapidly, it can be determined that the light receiving element is defective. Further, the output of a defective light receiving element can be interpolated with the output of an adjacent light receiving element for the above reason. For the above reasons, the present invention identifies a defective light receiving element based on the difference in output level between adjacent light receiving elements, and performs interpolation using the output button type of the defective light receiving element using the output of the adjacent light receiving element. A line image sensor with a defect can also be used in the same way as a good product.

Embodiment FIG. 1 is a block diagram showing an embodiment of the image sensor of the present invention. In FIG. 1, reference numeral 1 denotes a light-receiving element array, which has a clock signal input terminal 11 for outputting a signal from each light-receiving element. 2 is an A/D conversion circuit, which has an input terminal 21 for analog signals from the light receiving element array;
It has an A/D conversion start signal input terminal 22. 3 is a latch circuit, and has an input terminal 31.3 for receiving an N-bit digital signal from an A/D conversion circuit. Latch clock signal input terminal 3
It has 2. A timing generation circuit 4 generates a timing signal for the image sensor circuit, and has a reference clock signal input terminal 41. Reference numeral 5 denotes a selection circuit having input terminals 51 and 52 for two N-bit digital signals, and a selection signal input terminal 63 for selecting one of the two N-bit digital signals. 6 is a latch circuit that stores the N-bit digital signal from the selection circuit 5, and has an N-bit digital signal input terminal 61. It has a latch clock signal input terminal e2. 7 is an absolute value output type subtraction circuit, which has two N-bit digital signal input terminals 71;
．． It has 72. 8 is a comparison circuit having two N-bit digital signal input terminals 81 and 82. Reference numeral 9 is a setting device which can set any N-bit digital value.

The output of each light-receiving element in the light-receiving element array is sequentially input to the A/D conversion circuit 2 in synchronization with the reference clock 7, and after being converted into an N-bit digital signal, it is stored in the latch circuit 3 by the latch clock signal 32. be done.

The N-bit digital output of the latch circuit 3 is input to one input terminal 72 of the absolute value subtraction circuit 7, while the launch circuit 6
The N-bit digital output of the light receiving element array stored one reference clock time ago is input to the input terminal 71. The absolute difference is input to the input terminal 81 of the comparator circuit 8,
It is compared with the N-bit digital setting value of the setting device 9 input to the input terminal 82, and if the absolute difference is larger than the setting value, it outputs 1, and the two N bits input to the selection circuit 5
Out of the bit digital signal, from the latch circuit 6 to the input terminal 6
Select the N-bit digital signal input to 1.

The selected N-bit digital signal is input to the latch circuit 6, stored as a latch clock signal 62, and becomes the image sensor output.

In this way, it is possible to realize an image sensor having a function of comparing the output of a light receiving element with an adjacent light receiving element and interpolating with the output of the adjacent light receiving element if there is a level difference greater than a set value.

As described in detail, according to the present invention, by providing an interpolation circuit with a simple circuit configuration, it is possible to use even a line image sensor having a defective light-receiving element, which is extremely useful in practice.

[Brief explanation of drawings]

The figure is a block diagram of an image sensor in one embodiment of the present invention. 1... Light receiving element array, 2... A/D
Conversion circuit, 3...Latch circuit, 4...
Timing generation circuit, 6... Selection circuit, 6...
... Latch circuit, 7 ... Absolute value range calculation circuit,
8... Comparison circuit, 9... Setting device.

Claims (1)

[Claims] a light-receiving element array; a means for holding a signal output from the light-receiving element array in synchronization with a reference clock; the output of each light-receiving element is compared with the output of an adjacent light-receiving element, and a difference in output level is set in advance. and means for interpolating the output signal of each of the light-receiving elements with the output signal of the adjacent light-receiving element based on the result of the determination means. .