Real-time, localized enhancement of a video image using separable two-dimensional filters

Claim 1

A video processing apparatus for enhancing presentation characteristics of a raster-scanned image signal, comprising: processing means responsive to an input signal representative of a raster-scanned image and to a statistical signal representative of a statistical value of said input signal for combining said input signal and said statistical signal to produce an output signal representing an enhancement of said raster-scanned image by increasing the contrast in the image; plural-order filter means responsive to said input signal and to a filter variable signal for producing said statistical signal during a first image raster field defined by said input signal, said statistical signal produced by two-dimensional filtration of said input signal within a horizontal filter bandwidth and a vertical filter bandwidth, at least one of said filter bandwidths being determined by said filter variable signal; and phase adjustment means coupled between said processing means and said plural-order filter means for adjusting the phase of said statistical signal to substantially equal the phase of said input signal by producing said filter variable signal based upon two-dimensional filtration of a second image raster field defined by said input signal, said second image raster field corresponding to, but preceding, said first image raster field.

Claim 3

An apparatus for providing, for a time-varying input signal producing a raster-scanned image, a multidimensionally-filtered output signal, comprising: a first higher-order filter means, responsive to said input signal, for producing a dimensionally filtered signal representative of the subjection of said input signal to at least a first filter function having a first filter bandwidth; means for providing plural value signals, each corresponding to the value of one of a set of state variables; a second higher-order filter means responsive to said value signals and to said dimensionally-filtered signal for subjecting said dimensionally-filtered signal to a second filter function having a second filter bandwidth to produce a multidimensionally-filtered output signal representative of the subjection of said input signal to said first and second filter functions; and means responsive to said first and second filter bandwidths for adjusting the phase of said multidimensionally-filtered output signal to substantially align the output signal spatial phase with the spatial phase of said input signal.

Claim 4

An apparatus for providing, for a time-varying input signal producing a raster-scanned image, a multidimensionally-filtered output signal, comprising: a first higher-order filter means, responsive to said input signal, for producing a dimensionally filtered signal representative of the subjection of said input signal to at least a first filter function having a first filter bandwidth; means for providing plural value signals, each corresponding to the value of one of a set of state variables; a second higher-order filter means responsive to said value signals and to said dimensionally-filtered signal for subjecting said dimensionally-filtered signal to a second filter function having a second filter bandwidth to produce a multidimensionally-filtered output signal representative of the subjection of said input signal to said first and second filter functions; and means responsive to said first and second filter bandwidths for adjusting the phase of said multidimensionally-filtered output signal to substantially align the output signal spatial phase with the spatial phase of said input signal.

Claim 5

An apparatus responsive to an input signal representing a raster-scanned image for providing an output signal representing said image with increased contrast characteristics, comprising: adaptive processor means responsive to said input signal and to a mean value signal indicative of the mean value of said input signal at a point contained in a localized portion of the image represented by said input signal for producing a difference signal representative of a difference between said input and mean value signals; signal processing means in said adaptive processor means responsive to said input signal, to said mean value signal, and to a variance signal representing the standard deviation of said input signal over said localized image portion for producing an output signal representing said image by increasing the contrast in said image to a selected value; and multidimensional filter means responsive to said input signal and to said difference signal for producing said mean value signal and said variance signal, said multidimensional filter means including: horizontal means responsive to said input signal for performing horizontal low pass filtration within a horizontal filtration bandwidth of a horizontal portion of said image, and vertical means, responsive to said horizontal low pass filtration for performing vertical low pass filtration within a vertical filtration bandwidth of each of a series of vertical portions of said image taken along said horizontal portion, said vertical means providing a filter signal representative of said vertical low pass filtration; adjustment means for selectively adjusting said vertical bandwidth; and field means responsive to said filter signal for producing said means value signal and for aligning the phase of said mean value signal with the phase of said input signal based upon said adjusting.

Claim 6

An apparatus responsive to an input signal representing a raster-scanned image for providing an output signal representing said image with increased contrast characteristics, comprising: adaptive processor means responsive to said input signal and to a mean value signal indicative of the mean value of said input signal at a point contained in a localized portion of the image represented by said input signal for producing a difference signal representative of a difference between said input and mean value signals; signal processing means in said adaptive processor means responsive to said input signal, to said mean value signal, and to a variance signal representing the standard deviation of said input signal over said localized image portion for producing an output signal representing said image by increasing the contrast in said image to a selected value; and multidimensional filter means responsive to said input signal and to said difference signal for producing said mean value signal and said variance signal, said multidimensional filter means including: horizontal means responsive to said input signal for performing horizontal low pass filtration within a horizontal filtration bandwidth of a horizontal portion of said image, and vertical means, responsive to said horizontal low pass filtration for performing vertical low pass filtration within a vertical filtration bandwidth of each of a series of vertical portions of said image taken along said horizontal portion, said vertical means providing a filter signal representative of said vertical low pass filtration; adjustment means for selectively adjusting said vertical bandwidth; and field means responsive to said filter signal for producing said means value signal and for aligning the phase of said mean value signal with the phase of said input signal based upon said adjusting.