Device for noise reduction in digital fluoroscopy systems

Claim 2

In a system including means for converting picture elements (pixels) comprising an image to analog video signals, means for converting the analog signals to live digital video pixel signals, and the improved apparatus for reducing the effect of noise in a television display of the image, comprising: a full image memory for storing digitized video pixel signals that compose an image frame, said memory having input and output means for pixel signals, motion detector means comprising means for comparing the stored video pixel signals that are output from the memory in succession with corresponding live digital pixel signals that are destined for the memory locations from which the respective stored video signals were obtained, said means for comparing having output means for signals representative of the results of the comparison of said stored and live video signals, means for generating a controllable fraction, K, based on the result of said comparison and on the value of the live video pixel signal, means for summing said controllable fraction, K, of the stored pixel value with a corresponding controllable fraction, (I-K), of the live pixel value, and means for coupling the result of the summing to the input of the frame -memory for being stored in the location from which the aforesaid stored video pixel signal was obtained.

Claim 3

The apparatus in claim 1 wherein the noise reducing apparatus is governed by the equation: Store n = Store n-1 + K(Live n -Store n-1 ) where Store is the processed signal output from said summing means to a memory pixel location, Store n-1 is the averaged value of the pixel signal in a location, Live is the live digitized signal corresponding to the pixel location and K is given values ranging between 0 and 1 such that if motion above a predetermined threshold is detected in a pixel, K has a value of 1 and the Live signal replaces the stored signal in the memory location to which the pixel relates.

Claim 4

The apparatus defined in claim 2 wherein as K increases, the amount of noise reduction.decreases.

Claim 5

The apparatus defined in claim 1 wherein said comparison means constituting the motion detector is an arithmetic logic unit.

Claim 6

The system defined in claim 1 including digital-to-analog converter means having output means and input means coupled to the output means of said memory and being operative to convert the pixel signals in succession to corresponding analog video signals that are output from the converter for controlling a television monitor to display the image.

Claim 7

Apparatus for reducing noise in a system including means for converting an x-ray image to corresponding analog video signals, means for amplifying said video signals and any noise included therewith logarithmically to obtain video signals whose magnitudes are substantially linearly related to the pixels in the x-ray image and means for converting the logarithmic analog video signals to live video digital pixel signals each of which corresponds to a discrete pixel, and the improvement for reducing the effect of noise in a television display of the image, comprising: J a full image memory for containing digitized video pixel signals that compose an image frame, said memory having input and output means for pixel signals, motion detector means comprised of means for comparing the stored digital video pixel signals that are output from the memory in succession with corresponding live digitial pixel signals that are destined for the memory locations from which the stored signals were obtained, said means for comparing having output means for digital signals representative of the result of the comparison of stored and live signals, look-up table means having addressing means and output means and a plurality of locations storing digital signals corresponding to the respective values of the results of the comparison signals that are output from the comparison means multiplied by K, where the K's are predetermined values corresponding to the amount of noise reduction desired in relation to the brightness levels of pixels and the product of K times the difference signal is representative of brightness level and the amount of motion that has been determined by comparison and said product being output from said look-up table means, said live signals corresponding to brightness of the pixel in process and said signals resulting from comparison and corresponding to motion constituting addresses for said addressing means to select and output a value of K times the signal resulting from comparison that corresponds to both the amount of noise reduction for the brightness level and the amount of motion, summing means having output means coupled to the input of said memory and having one input for the output from said look-up table and having another input, said summing means being operative to add the stored pixel signals to the other inputs and deliver the result to the memory location from which the stored pixel signal was obtained.

Claim 8

Apparatus for reducing noise in a system including means for converting an x-ray image to corresponding analog video signals, means for amplifying said video signals and any noise included therewith logarithmically to obtain video signals whose magnitudes are substantially linearly related to the pixels in the x-ray image and means for converting the logarithmic analog video signals to live video digital pixel signals each of which corresponds to a discrete pixel, and the improvement for reducing the effect of noise in a television display of the image, comprising: J a full image memory for containing digitized video pixel signals that compose an image frame, said memory having input and output means for pixel signals, motion detector means comprised of means for comparing the stored digital video pixel signals that are output from the memory in succession with corresponding live digitial pixel signals that are destined for the memory locations from which the stored signals were obtained, said means for comparing having output means for digital signals representative of the result of the comparison of stored and live signals, look-up table means having addressing means and output means and a plurality of locations storing digital signals corresponding to the respective values of the results of the comparison signals that are output from the comparison means multiplied by K, where the K's are predetermined values corresponding to the amount of noise reduction desired in relation to the brightness levels of pixels and the product of K times the difference signal is representative of brightness level and the amount of motion that has been determined by comparison and said product being output from said look-up table means, said live signals corresponding to brightness of the pixel in process and said signals resulting from comparison and corresponding to motion constituting addresses for said addressing means to select and output a value of K times the signal resulting from comparison that corresponds to both the amount of noise reduction for the brightness level and the amount of motion, summing means having output means coupled to the input of said memory and having one input for the output from said look-up table and having another input, said summing means being operative to add the stored pixel signals to the other inputs and deliver the result to the memory location from which the stored pixel signal was obtained.

Claim 9

The apparatus in claim 6 wherein the noise reducing apparatus is governed by the equation: Store n = Storen-1 + K(Live n -Store n-1 ) where Store is the processed signal output from said summing means to a memory pixel location, Store n-1 is the .averaged value of the pixel signal in a location, Live is the live digitized signal corresponding to the pixel location and K is given values ranging between 0 and 1 such that if motion above a predetermined threshold is detected in a pixel, K has a value of 1 and the Live signal replaces the stored signal in the memory location to which the pixel relates.

Claim 10

The apparatus defined in claim 7 wherein as K increases, the amount of noise reduction decreases.

Claim 11

The apparatus defined in claim 6 wherein said comparison means constituting the motion detector is an arithmetic logic unit.

Claim 12

The system defined in claim 6 including digital-to-analog converter means having output means and input means coupled to the output means of said memory and being operative to convert the pixel signals in succession to corresponding analog video signals that are output from the converter for controlling said television monitor to display the image.