Contour enhancement processing circuit, contour enhancement processing method, and television camera

Abstract

A contour enhancement processing circuit includes a crisp circuit for removing a noise component from a contour component signal using a crisp signal for removing a noise component in the contour component signal and outputting a contour signal, a crisp gain control circuit for obtaining a gain for controlling amplification of a signal becoming the basis of the crisp signal according to a video level and outputting the gain as a crisp gain, a multiplier for multiplying the crisp gain and the signal becoming the basis of the crisp signal and outputting a crisp signal to the crisp circuit, a gain circuit for amplifying the contour signal from which a noise component is removed in the crisp circuit, and an adder for adding the video signal transmitted from a delay circuit and the amplified contour signal transmitted from the gain circuit and outputting a contour-enhanced video signal.

Claims

1. A contour enhancement processing circuit used in a video signal processing unit of a television camera, comprising: a first delay circuit configured to delay an inputted video signal; a contour extraction circuit configured to extract a contour component signal from the video signal; a second delay circuit configured to delay the contour component signal; a video level detection circuit configured to detect a video level of the video signal and output the video level; a crisp circuit configured to remove a noise component from the contour component signal transmitted from the second delay circuit using a crisp signal for removing the noise component in the contour component signal and output a contour signal; a crisp gain control circuit configured to obtain a gain for controlling amplification of a crisp original signal for generating the crisp signal according to the video level and output the gain as a crisp gain; a multiplier configured to multiply the crisp gain and the crisp original signal to generate the crisp signal and output the crisp signal to the crisp circuit; a gain circuit configured to amplify the contour signal from which the noise component is removed in the crisp circuit; and an adder configured to add the video signal transmitted from the first delay circuit and the amplified contour signal transmitted from the gain circuit and output a contour-enhanced video signal.

2. The contour enhancement processing circuit of claim 1, wherein the crisp gain control circuit sets a video level of 100% as a normalized reference level, sets a gain at the normalized reference level as 1, and outputs a crisp gain according to the video level from the video level detection circuit with respect to the normalized reference level.

3. The contour enhancement processing circuit of claim 2, wherein the crisp gain control circuit outputs a crisp gain according to a video level on a line connecting a first point where the video level is zero and the crisp gain is zero and a second point where the video level is 100% and the crisp gain is 1, when the video level is indicated on a horizontal axis and the crisp gain is indicated on a vertical axis.

4. The contour enhancement processing circuit of claim 3, wherein the crisp gain control circuit shifts the first point in a horizontal axis direction or a vertical axis direction according to a tilt signal from the outside for changing a slope of the line connecting the first point and the second point.

5. A contour enhancement processing method used in a video signal processing unit of a television camera, comprising: a first delay means for delaying an inputted video signal; a contour extraction means for extracting a contour component signal from the video signal; a second delay means for delaying the contour component signal; a video level detection means for detecting a video level of the video signal and outputting the video level; a crisp means for removing a noise component from the contour component signal transmitted from the second delay circuit using a crisp means for removing a noise component from the contour component signal transmitted from the second delay means and outputting a contour signal; a crisp gain control means for obtaining a gain for controlling amplification of a crisp original signal for generating the crisp signal according to the video level and outputting the gain as a crisp gain; a multiplication means for multiplying the crisp gain and the crisp original signal to generate the crisp signal and outputting the crisp signal to the crisp means; a gain means for amplifying the contour signal from which the noise component is removed in the crisp means; and an addition means for adding the video signal transmitted from the first delay means and the amplified contour signal transmitted from the gain means and outputting a contour-enhanced video signal, wherein the crisp gain control means sets a video level of 100% as a normalized reference level, sets a gain at the normalized reference level as 1, and outputs a crisp gain according to the video level from the video level detection means with respect to the normalized reference level, the crisp gain control means outputs a crisp gain according to a video level on a line connecting a first point where the video level is zero and the crisp gain is zero and a second point where the video level is 100% and the crisp gain is 1, when the video level is indicated on a horizontal axis and the crisp gain is indicated on a vertical axis, and the crisp gain control means shifts the first point in a horizontal axis direction or a vertical axis direction according to a tilt signal from the outside for changing a slope of the line connecting the first point and the second point.

6. A television camera including a prism configured to take a video image inputted from a lens, an imaging element, a CDS (Correlated Double Sampling) circuit, a VGA (Variable Gain Amplification) circuit, an A/D converter, a video signal processing unit, a video signal output unit and a timing generation unit, wherein: the video signal processing unit comprises: a first delay means for delaying an inputted video signal; a contour extraction means for extracting a contour component signal from the video signal; a second delay means for delaying the contour component signal; a video level detection means for detecting a video level of the video signal and outputting the video level; a crisp means for removing a noise component from the contour component signal transmitted from the second delay circuit using a crisp means for removing a noise component from the contour component signal transmitted from the second delay means and outputting a contour signal; a crisp gain control means for obtaining a gain for controlling amplification of a crisp original signal for generating the crisp signal according to the video level and outputting the gain as a crisp gain; a multiplication means for multiplying the crisp gain and the crisp original signal to generate the crisp signal and outputting the crisp signal to the crisp means; a gain means for amplifying the contour signal from which the noise component is removed in the crisp means; and an addition means for adding the video signal transmitted from the first delay means and the amplified contour signal transmitted from the gain means and outputting a contour-enhanced video signal, wherein the crisp gain control means sets a video level of 100% as a normalized reference level, sets a gain at the normalized reference level as 1, and outputs a crisp gain according to the video level from the video level detection means with respect to the normalized reference level, the crisp gain control means outputs a crisp gain according to a video level on a line connecting a first point where the video level is zero and the crisp gain is zero and a second point where the video level is 100% and the crisp gain is 1, when the video level is indicated on a horizontal axis and the crisp gain is indicated on a vertical axis, and the crisp gain control means shifts the first point in a horizontal axis direction or a vertical axis direction according to a tilt signal from the outside for changing a slope of the line connecting the first point and the second point.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is a configuration block diagram of a contour enhancement processing circuit according to an embodiment of the present invention.

(2) FIG. 2 is a configuration block diagram of a contour extraction circuit.

(3) FIG. 3 is a diagram showing a time chart for the generation of a contour-enhanced video signal.

(4) FIG. 4 is a diagram showing the relationship between a video level and a crisp gain.

(5) FIGS. 5A to 5E are signal waveform diagrams showing a contour enhancement process.

(6) FIG. 6 is a diagram showing the control of a slope of a crisp gain with respect to a video level.

(7) FIG. 7 is a configuration block diagram of a television camera.

(8) FIG. 8 is a configuration block diagram of a conventional first contour enhancement processing circuit.

(9) FIG. 9A is a diagram showing an original video example (a video example before contour enhancement), and FIG. 9B is a diagram showing a video example after contour enhancement.

(10) FIGS. 10A to 10D are signal waveform diagrams showing an ideal contour enhancement process.

(11) FIGS. 11A to 11D are signal waveform diagrams in a case where a noise is contained in a video signal.

(12) FIG. 12 is a configuration block diagram of a second conventional contour enhancement processing circuit.

(13) FIG. 13 is a signal waveform diagram showing a crisp function.

(14) FIGS. 14A to 14E are signal waveform diagrams showing a conventional second contour enhancement process.

(15) FIG. 15 is a contour signal waveform diagram for explaining a problem of prior art.

DETAILED DESCRIPTION OF THE EMBODIMENTS

(16) Embodiments of the present invention will be described with reference to the drawings.

Outline of Embodiment

(17) In a contour enhancement processing circuit according to an embodiment of the present invention, a contour enhancement processing circuit in which a first delay circuit delays an inputted video signal, a contour extraction circuit extracts a contour component signal from the video signal, a second delay circuit delays the contour component signal, a video level detection circuit detects a video level of the video signal and outputs the video level, a crisp circuit removes a noise component from the contour component signal using a crisp signal for removing a noise component in the contour component signal transmitted from the second delay circuit and outputs a contour signal, a crisp gain control circuit controls a gain of the crisp signal according to the video level and outputs the gain of the crisp signal, a multiplier multiplies the gain the crisp signal and the signal becoming the basis of the crisp signal and outputs a crisp signal to the crisp circuit, a gain circuit amplifies the contour signal from which a noise component is removed in the crisp circuit, and an adder adds the video signal transmitted from the first delay circuit and the amplified contour signal transmitted from the gain circuit and outputs a contour-enhanced video signal. Therefore, the noise can be removed by performing an appropriate crisp process according to the video level, and a clear contour-enhanced video signal with little noise from the dark portion to the bright portion can be obtained.

(18) (The Present Contour Enhancement Processing Circuit: FIG. 1)

(19) A contour enhancement processing circuit according to an embodiment of the present invention (the present contour enhancement processing circuit) will be described with reference to FIG. 1. FIG. 1 is a configuration block diagram of the contour enhancement processing circuit according to an embodiment of the present invention.

(20) As shown in FIG. 1, the present contour enhancement processing circuit includes a first delay circuit 12, an adder 13, a contour extraction circuit 14, a gain circuit 15, a crisp circuit 16, a video level detection circuit 17, a crisp gain control circuit 18, a multiplier 19, and a second delay circuit 20.

(21) In a video signal processing unit of a television camera, the respective circuits mentioned above are sometimes referred to as a first delay means, an addition means, a contour extraction means, a gain means, a crisp means, a video level detection means, a crisp gain control means, a multiplication means, and a second delay means.

(22) A video signal is inputted to the first delay circuit 12, the contour extraction circuit 14 and the video level detection circuit 17.

(23) An output signal 12c from the first delay circuit 12 is inputted to the adder 13.

(24) An output signal 14a from the contour extraction circuit 14 is inputted to the second delay circuit 20, an output signal 20a from the second delay circuit 20 is inputted to the crisp circuit 16, an output signal 16b from the crisp circuit 16 is inputted to the gain circuit 15, and an output signal 15c from the gain circuit 15 is inputted to the adder 13.

(25) Furthermore, an output signal 17a from the video level detection circuit 17 is inputted to the crisp gain control circuit 18, an output signal 18a from the crisp gain control circuit 18 is inputted to the multiplier 19, and an output signal 19a from the multiplier 19 is inputted to the crisp circuit 16.

(26) (Respective Parts of the Present Contour Enhancement Processing Circuit)

(27) Next, the respective parts of the present contour enhancement processing circuit will be specifically described.

(28) The first delay circuit 12 delays the inputted video signal by the processing time in the contour extraction circuit 14, the second delay circuit 20, the crisp circuit 16 and the gain circuit 15, and outputs a delayed video signal 12c to the adder 13.

(29) The contour extraction circuit 14 extracts a signal of a contour component of the inputted video signal and outputs a contour signal 14a to the second delay circuit 20. Various methods for extracting a contour are known and any contour extraction method may be used.

(30) A specific configuration of the contour extraction circuit 14 and a method of extracting a contour will be described later.

(31) The video level detection circuit 17 detects a video level of the inputted video signal and outputs a video level signal (video level) 17a to the crisp gain control circuit 18.

(32) The crisp gain control circuit 18 outputs, to the multiplier 19, a crisp gain signal (crisp gain) 18a for controlling the amplification of a signal (crisp original signal: crisp) becoming the basis of the crisp signal according to the video level 17a transmitted from the video level detection circuit 17.

(33) Specifically, the crisp gain control circuit 18 receives a normalized reference level from the CPU 11 of the television camera. The normalized reference level is a signal when the video level is 100%. The normalized reference level is set so that the crisp gain is 1.0 at the normalized reference level.

(34) Accordingly, the crisp gain control circuit 18 obtains a ratio of the video level 17a inputted from the video level detection circuit 17 to the video level of 100%, obtains a crisp gain according to the ratio, and outputs the crisp gain to the multiplier 19. Since the crisp gain is 1.0 at the video level of 100%, the crisp gain for the video level 17a inputted from the video level detection circuit 17 is in the range of 0 to 1.0.

(35) The control of the crisp gain in the crisp gain control circuit 18 will be described later.

(36) The multiplier 19 multiplies the crisp gain signal 18a and the signal (crisp original signal) becoming the basis of the crisp signal indicating a noise removal amount inputted from the CPU 11, and outputs a crisp signal (noise reduction amount) 19a to the crisp circuit 16.

(37) That is, the crisp signal 19a is controlled to be variable according to the detected video level.

(38) The second delay circuit 20 delays the inputted contour signal 14a such that the phase of the noise reduction amount 19a calculated by the video level detection circuit 17, the crisp gain control circuit 18 and the multiplier 19 matches the phase of the contour signal 14a.

(39) The crisp circuit 16 removes a noise component from the contour signal 14a using the crisp signal 19a for removing a noise component in the contour signal 14a transmitted from the second delay circuit 20, and outputs a contour signal 16b.

(40) The gain circuit 15 amplifies the contour signal 16b, from which the noise component is removed by the crisp circuit 16, by the amplification amount (gain) inputted from the CPU 11, and outputs an amplified contour signal 15c to the adder 13.

(41) The adder 13 adds the video signal 12c transmitted from the first delay circuit 12 and the amplified contour signal 15c transmitted from the gain circuit 15, and outputs a contour-enhanced video signal in which the contour is enhanced.

(42) (Contour Extraction Circuit: FIG. 2)

(43) Next, the contour extraction circuit in the present contour enhancement processing circuit will be described with reference to FIG. 2. FIG. 2 is a configuration block diagram of the contour extraction circuit.

(44) As shown in FIG. 2, the contour extraction circuit 14 includes delay circuits (D) 141 and 142, an adder 143, a divider () 144, a subtractor 145, and an adder 146.

(45) A video signal d1 is inputted to the delay circuit 141 and the adder 143, a video signal d2 delayed by the delay circuit 141 is inputted to the delay circuit 142, the subtractor 145 and the adder 146, and a video signal d3 delayed by the delay circuit 142 is inputted to the adder 143.

(46) The video signal d1 and the video signal d3 transmitted from the delay circuit are added in the adder 143. The added video signal becomes a half () signal level by the divider 144 and is then outputted to the subtractor 145.

(47) The subtractor 145 subtracts the signal of the divider 144 from the video signal d2 and outputs the subtracted signal to the adder 146 as a contour signal. Then, in the adder 146, the contour signal is added to the video signal d2, and a contour-enhanced video signal is outputted.

(48) (Generation of Contour-Enhanced Video Signal: FIG. 3)

(49) Next, the generation of a contour-enhanced video signal will be described with reference to FIG. 3. FIG. 3 is a diagram showing a time chart for the generation of a contour-enhanced video signal.

(50) As shown in FIG. 3, in order to generate a contour-enhanced video signal, the video signals d2 and d3 are delayed with respect to the video signal d1, a video signal of d1+d3 is generated by the adder 143, and a video signal of (d1+d3)/2 is generated by the divider 144.

(51) Then, the subtractor 145 performs a subtraction process to generate a video signal of d2(d1+d3)/2 and to outputs the video signal of d2(d1+d3)/2 as a contour signal.

(52) Further, the adder 146 performs an addition process to generate a video signal of d2+contour signal and to output a contour-enhanced video signal.

(53) (Relationship Between Video Level and Crisp Gain: FIG. 4)

(54) Next, the relationship between a video level and a crisp gain will be described with reference to FIG. 4. FIG. 4 is a diagram showing the relationship between a video level and a crisp gain.

(55) As shown in FIG. 4, the crisp gain of the inputted video level 17a is specified by using a straight line connecting a point (a second point in the claims) where the crisp gain is 1.0 times with respect to the video level of 100% and a zero point (a first point in the claims) where the crisp gain is 0 times with respect to the video level of 0%.

(56) In this regard, the normalized reference level inputted to the crisp gain control circuit 18 is a reference level at which the video level in FIG. 4 is 100%. In other words, the crisp gain control circuit 18 determines what percentage of the reference level the video level 17a inputted from the video level detection circuit 17 is with the normalized reference level as the reference level of the video level 100%. The crisp gain is obtained by using a slope line of FIG. 4.

(57) Incidentally, the conventional crisp gain is constant as 1.0 times.

(58) (Signal Waveform Showing the Present Contour Enhancement Process: FIGS. 5A to 5E)

(59) Next, a signal waveform showing the present contour enhancement process will be described with reference to FIGS. 5A to 5E. FIGS. 5A to 5E are signal waveform diagrams showing the present contour enhancement process.

(60) In FIG. 5A, there is shown a video signal waveform containing a noise. The noise has a characteristic that the noise increases in proportion to the video level.

(61) In FIG. 5B, there is shown a contour signal waveform in which a contour component is extracted from the video signal by the contour extraction circuit 14. Since a noise component is also extracted, the noise is also contained in the contour signal waveform.

(62) In FIG. 5C, there is shown a contour signal waveform in which a noise is removed from the video signal by the crisp circuit 16 using the crisp signal adjusted by the video level detection circuit 17, the crisp gain control circuit 18 and the multiplier 19. Unlike the conventional crisp process, noise removal is performed according to the noise amount over the entire portion from a low video level portion to a high video level portion. Thus, there is no possibility that the contour signal becomes unnecessarily small or the contour signal disappears.

(63) In FIG. 5D, there is shown a contour signal waveform obtained by amplifying the contour signal from the crisp circuit 16 using the gain circuit 15. Since the noise is removed in the crisp process, only the contour is amplified.

(64) In FIG. 5E, the adder 13 obtains a contour-enhanced video signal by adding (synthesizing) the contour signal transmitted from the gain circuit 15 to the video signal transmitted from the first delay circuit 12. The contour-enhanced video signal is a video image in which the sharpness of the contour is increased and only the noise of the video signal is contained without the noise of the contour signal.

(65) In this manner, it is possible to generate a contour signal capable of completely eliminating the noise component in the contour signal extracted from the video signal and sufficiently enhancing the contour portion.

(66) (Slope Control of Crisp Gain with Respect to Video Level: FIG. 6)

(67) Next, the slope control of the crisp gain with respect to the video level will be described with reference to FIG. 6. FIG. 6 is a diagram showing the slope control of the crisp gain with respect to the video level.

(68) As shown in FIG. 6, the slope of an oblique line can be arbitrarily changed about a point where the crisp gain is 1.0 times at the video level of 100%. The slope of the crisp gain with respect to the video level can be controlled by the slope signal (slope) inputted to the crisp gain control circuit 18.

(69) In FIG. 6, when the oblique line is changed to the lower side with respect to the central reference oblique line, the crisp gain is 0 times at the video level of about 20%. The crisp function does not work in the dark image with the video level of 20% or less. Thus, the noise removal cannot be performed.

(70) Furthermore, if the oblique line is changed to the upper side with respect to the reference oblique line, the crisp gain is about 0.25 times even at the video level of 0%. Even in the dark image with the video level of 0%, the crisp function works a little bit to eliminate a noise.

(71) That is, the degree of effectiveness of the crisp function is adjusted by the slope signal according to the situation of the video signal.

Effect of Embodiment

(72) According to the present contour enhancement processing circuit, the degree of operation of the crisp function in the crisp circuit 16 is controlled according to the video level of the video signal. Therefore, it is possible to completely eliminate the noise generated in the contour signal and to obtain a contour-enhanced video signal with less noise without reducing the contour portion of the contour signal.

(73) Further, according to the present contour enhancement processing circuit, it is possible to control the slope of the reference oblique line indicating the relationship between the video level and the crisp gain. Therefore, the slope of the oblique line can be controlled according to the situation of the video image, and the noise removal can be realized by performing an appropriate crisp process according to the video image.

INDUSTRIAL APPLICABILITY

(74) The present invention is suitable for a contour enhancement processing circuit, a contour enhancement processing method and a television camera, which are capable of making sure that the amount of noise to be removed in a crisp circuit can be made variable according to a video signal level and capable of realizing a clear contour enhancement process with little noise from a dark portion to a bright portion. This application claims the benefit of priority based on Japanese Patent Application No. 2015-222457 filed on Nov. 12, 2015, the disclosure of which is incorporated herein by reference in its entirety.

(75) TABLE-US-00001 Description of Reference Numerals 1: television camera 2: lens 3: prism 4: imaging element 5: CDS (Correlated Double Sampling) circuit 6: VGA (Variable Gain Amplification) circuit 7: A/D converter, 8: video signal processing unit 9: video signal output unit 10: TG (timing generation unit) 11: CPU (Control Unit) 12: first delay circuit (delay circuit) 13: adder 14: contour extraction circuit 15: gain circuit 16: crisp circuit 17: video level detection circuit 18: crisp gain control circuit 19: multiplier 20: second delay circuit 141, 142: delay circuit (D) 143: adder 144: divider (1/2) 145: subtractor 146: adder