US 5,327,247 A · Compensation of losses and defects in telecine devices

Abstract

A signal produced by a telecine suffers from losses and defects caused by differences in response to incident light between different areas of the screen area scanned. These differences may arise from burning of the screen, blemishes, dirt in the system, differences in grain size of phosphor particles, missing particles, and losses in the internal optical system of the machine. The invention divides the scanning area into a correction map and devises for each area a correction factor based on the response of that area to incident illumination. When a defect is detected, video data from an adjacent area is substituted. Correction factors are held in a look-up RAM and output to a multiplier where they are multiplied with video data. The video data input to the multiplier may be suppressed and a test pattern may be loaded into the multiplier. Burn at the ends of video lines may be reduced by reducing the intensity and/or dwell time of the scanning spot on any one area of the screen in the vicinity of the line end.

Claims38

Dependent claims

A cathode ray tube (CRT) flying spot image scanning apparatus, comprising:

a scanning area for scanning with a flying spot;
means for addressing each location of the scanning area;
means for deriving a correction pixel map addressable by coordinates generated by the addressing means;
means for weighting an output video signal to compensate for defects and losses along the optical path of the apparatus, the weighting means comprising means for dividing the scanning area into a plurality of sub-areas for corresponding to a pixel of the correction pixel map;
means for determining a correction factor for each subarea of the scanning area indicative of defects and losses associated with that area;
storage means for holding derived correction factors;
means for applying the correction factors to output video data from the apparatus to produce a weighted video signal;
the addressing means including a digital scan generator and a scanning pixel map derived from the digital scan generator, the orientation of the image scanning performed by the flying spot and correction pixel map with respect to one another being variable;
and
means for applying the correction factor derived for a given pixel to a pixel of the picture scan whose centre falls within that correction map pixel.

7 more elements

A method of weighting a video signal to compensate for defects and losses in a cathode ray tube (CRT) flying spot scanning apparatus having a scanning area for being scanned with the flying spot for producing the signal, the method comprising the steps of:

dividing the scanning area scanned to produce a video signal by the flying spot of the CRT into an image scanning map and a digital correction map having a plurality of uniquely addressable pixels, the correction map being derived from a digital scanning map of the CRT and being addressable by the scan coordinates of the scanning map, the orientation of the scanning map controlling the image scanning performed by the scanning apparatus, and the orientation of the scanning map and the correction map with respect to one another being variable;
deriving for each pixel of the correction map a correction factor indicative of losses and defects associated with that pixel, the correction factor applied to a given image scanning map pixel being derived from the correction map pixel which encloses the centre of that image scanning map pixel;
and
storing in a store the derived correction factors and applying the correction factors to said video signal during operation of the scanning apparatus to produce a compensated signal.

1 more element

Dependencies are inferred from the claim text.

Compensation of losses and defects in telecine devices

Life of this patent

Compensation of losses and defects in telecine devices

Life of this patent

Abstract

Claims38