Image Number 3 for United States Patent #6452631.
The present invention improves the contrast of the image signal before further adjustment by the principle of superposition of the optical-transferring system. There are two ways to carry out the principle of superposition one is in space domain, the other is in frequency domain. Each of them can be implemented by the system or method of the present invention. To implement the compensation in space domain, the present invention utilize the result of scanning the correction board to compensate the optical energy scattered by the optical-transferring system. A pixel in object space can be expressed in terms of the linear combination of the corresponding pixels in image space according to the principle of superposition. Thus is obtained by extracting the coefficients of the linear combination. The pixels of desired picture in image space is multiplied by the compensation vector and the image with sharp contrast is produced by the present invention in space domain. To implement the compensation in frequency domain, the present invention get the result of scanning the correction board and transform it to frequency form. Thus the compensation vector is obtained by extracting the amplitude and phase angle of the frequency form of the result of scanning the correction board. Transform the result of scanning the desired picture into frequency form, followed by dividing it by the compensation vector. The desired picture in frequency form is obtained. Taking the inverse transform of the desired picture, which is in frequency form, the result is transformed in space domain and can be processed or displayed with sharp contrast.