Image signal processing apparatus, imaging apparatus and image processing program for performing image and noise correction

Patent metadata

Field	Value
Publication number	US-9712724-B2
Application number	US-201313758279-A
Country	US
Kind code	B2
Filing date	Feb 4, 2013
Priority date	Feb 8, 2012
Publication date	Jul 18, 2017
Grant date	Jul 18, 2017

Abstract

An image signal processing apparatus includes an image signal input unit for inputting an image signal, a noise correcting unit for executing noise correction processing for the input image signal to output a noise-corrected image signal; an image signal correcting unit for executing signal level correction processing for the noise-corrected image signal to output a signal level-corrected image signal; an image signal correction intensity control unit for determining correction intensity of the signal level correction processing in the image signal correcting unit; a signal extension estimating unit for estimating a signal extension degree of signal extension based on the determined correction intensity; and a noise correction intensity control unit for calculating and controlling correction intensity of the noise correction processing in the noise correcting unit.

First claim

The invention claimed is:

1. An image signal processing apparatus, comprising:
an image signal input unit which inputs an image signal;
an image signal correction intensity control unit which determines a signal level correction intensity of the image signal;
a signal extension estimating unit which estimates a signal extension degree of a signal level correction processing based on the signal level correction intensity;
a noise correction intensity control unit which adjusts a value of a noise correction intensity based on the signal extension degree;
a noise correcting unit which conducts a noise correction processing for the image signal based on the noise correction intensity; and
an image signal correcting unit which conducts a signal level correction processing based on the signal level correction intensity for the image signal on which the noise correction processing has been conducted, wherein the signal level correction processing comprises:
in response to a determination that the signal level correction intensity exceeds a predetermined threshold value, increasing a magnification factor of the signal range, wherein the signal range is a difference between a maximum value and a minimum value of the luminance signal of the image signal; and
in response to a determination that the signal level correction intensity is lesser than the predetermined threshold value, decreasing the magnification factor of the signal range.

2. The image signal processing apparatus according to claim 1 , wherein the image signal correction intensity controlling unit determines the signal level correction intensity such that the signal extension degree of a luminance range of an object in the image signal is bigger as the luminance range of the object is narrower.

3. The image signal processing apparatus according to claim 1 , further comprising a signal extension estimation information storage which stores therein signal extension estimation information, wherein the signal extension estimating unit estimates the signal extension degree based on the signal extension estimation information and the signal level correction intensity.

4. The image signal processing apparatus according to claim 3 , wherein the signal extension estimation information is a ratio between an input value and an output value of the signal level in the input/output characteristic of the signal level correction processing for a reference image signal correction.

5. The image signal processing apparatus according to claim 3 , wherein the signal extension estimation information is a ratio between a differential value of input values and a differential value of output values between two signal levels in the input/output characteristic of the signal level correction processing for a reference image signal correction.

6. The image signal processing apparatus according to claim 1 , further including a statistic information acquiring unit which calculates a distribution or a statistic quantity of a signal value for each desired region of the input image signal as statistic information,
wherein the image signal correction intensity control unit determines the signal level correction intensity of each desired region based on the statistic information,
the image signal correction unit conducts the signal level correction process based on the signal level correction intensity of each desired region,
the signal extension estimating unit selects a predetermined signal extension degree among the signal extension degrees of desired regions estimated from the signal level correction intensities for the desired regions, and
the noise correction intensity control unit determines the noise correction intensity from the predetermined signal extension degree.

7. The image signal processing apparatus according to claim 6 , wherein the signal extension estimating unit selects one of an average value of the signal extension degrees, N-th biggest value, maximum value, a weighted mean value in which the values are weighted according to positions and a median, which are obtained from the signal extension degrees for desired regions, as the predetermined signal extension degree.

8. The image signal processing apparatus according to claim 1 , wherein the image signal correcting unit consists of a plurality of image signal correction parts which respectively perform signal level correction processing with input/output characteristics different for each image signal output from the noise correction unit,
the image signal correction intensity control unit determines respective signal level correction intensities for the plurality of image signal correction parts,
the signal extension estimating unit estimates respective signal extension degrees based on the respective signal level correction intensities, and
the noise correction control unit determines the noise correction intensity by combining the respective signal extension degrees.

9. The image signal processing apparatus according to claim 8 , further comprising a plurality of statistic information acquiring parts each of which calculates, as statistic information, a distribution or a statistic quantity of a signal value of the image signal inputted to each of the image signal correcting parts,
wherein the image signal correction intensity control part controls the signal level correction intensities in corresponding one of the image signal correcting parts based on the statistic information calculated by the plurality of statistic information acquiring parts.

10. The image signal processing apparatus according to claim 1 , wherein the noise correction processing in the noise correcting unit is at least either one of two-dimensional correction processing to conduct the noise correction based on a correlation of a signal level between a pixel in consideration in the image signal and a peripheral pixel in the periphery of the pixel in consideration, three-dimensional correction processing to conduct the noise correction based on a correlation of a signal level of a pixel in consideration between images successive in a time axis, and edge emphasizing processing to make edge emphasizing correction intensity smaller in edge emphasizing.

11. The image signal processing apparatus according to claim 10 , wherein when the noise correcting unit conducts, as the noise correction processing, at least two processing in the two-dimensional correction processing, the three-dimensional correction processing, and the noise emphasizing processing, the noise correction intensity control unit respectively determines the correction intensities of the noise correction processing to be conducted among the two-dimensional correction processing, the three-dimensional correction processing, and the edge emphasizing processing.

12. The image signal processing apparatus according to claim 1 , further comprising:
an imaging unit which conducts an imaging operation to create an image signal to output the image signal therefrom;
an exposure quantity detecting unit which detects an exposure quantity of the imaging unit; and
an exposure control unit which controls exposure of the imaging unit based on the exposure quantity detected by the exposure quantity detecting unit,
wherein the noise correction intensity control unit adjust the value of the noise correction intensity using the signal extension degree, and an exposure control degree in the exposure control unit.

13. The image signal processing apparatus according to claim 10 , further comprising:
an imaging unit which conducts an imaging operation to create an image signal to output the image signal therefrom;
an exposure quantity detectin

Assignees

• Hitachi Ind & Control Solutions Ltd

Inventors

• Hirooka Shinichiro
• Sai Hirotomo
• Shiokawa Junji

Classifications

• H04N23/76

  by influencing the image signals · CPC title

• H04N25/60 Primary

  Noise processing, e.g. detecting, correcting, reducing or removing noise · CPC title

• H04N5/243

  Electricity · mapped topic

• H04N5/357

  Electricity · mapped topic

• H04N5/21 Primary

  Circuitry for suppressing or minimising disturbance, e.g. moiré or halo · CPC title