JP2662454B2 - Image signal processing device - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image signal processing apparatus, and more particularly to an image signal processing apparatus for recording a data-compressed image signal on an image signal recording medium such as a memory card and reproducing the image signal from the medium. The present invention relates to an image signal processing device that performs processing.

BACKGROUND ART As a device for performing contour correction of a video signal, for example, a patent application filed by the same applicant as that of the present invention, Japanese Patent Application No. 61-30 / 1986.
3852 discloses an apparatus that converts a non-linear video signal into a linear signal, performs contour enhancement in the state of the linear video signal, and returns the signal to the original non-linear signal. This conventional apparatus is characterized in that contour correction is performed to the same extent on both the shadow side and the highlight side of an image. This apparatus is suitable for, for example, reading an image signal recorded on an image signal recording medium and reproducing a visible image on a video monitor.

By the way, there is a digital electronic still camera in which an image signal generated by a solid-state imaging device is orthogonally transformed, encoded, quantized, and recorded in a compressed form on an image signal recording medium such as a memory card. is there.
This data compression usually degrades the high frequency components of the image signal, especially the luminance signal. Therefore, in the digital electronic still camera of such a method, even when recording an image signal,
In order to compensate for the deterioration of the high-frequency component, it is necessary to perform an outline emphasis process. For the same reason, it is necessary to perform a process of correcting the chroma for both the recording and the reproduction of the color signal.

Objective In view of such a demand, the present invention provides an image signal processing apparatus that compensates for signal deterioration due to data compression by signal compensation processing such as contour enhancement and saturation correction in both recording and reproduction of image signals. The purpose is to do.

DISCLOSURE OF THE INVENTION An image signal processing apparatus according to the present invention includes an input unit that inputs an image signal, an outline emphasis circuit that enhances an outline of a picture represented by the image signal, a saturation correction circuit that corrects the saturation of the image signal, Recording means for recording an image signal output from the contour enhancement circuit and the saturation correction circuit on an image signal recording medium; a reproduction circuit for also outputting an image signal output from the contour enhancement circuit and the saturation correction circuit to the image display device; Reading means for reading an image signal recorded on the image signal recording medium from the signal recording medium; and selecting means for selectively supplying the image signal from one of the input means and the reading means to the contour enhancement circuit and the saturation correction circuit. including.

DESCRIPTION OF THE EMBODIMENTS Next, an embodiment of an image signal processing device according to the present invention will be described in detail with reference to the accompanying drawings. The apparatus of the present embodiment receives, for example, a video signal generated from a solid-state imaging device at an input terminal 10, corrects the outline of a picture pattern represented by the image signal, corrects saturation, and finally compresses this data. Memory card
This is an image signal processing device for recording on the video monitor 12 and reproducing it as a visible image on the video monitor 14. In addition, memory card 12
Can be read out to correct the outline and again, and reproduced on the video monitor 14. This image signal processing device is advantageously applied to, for example, a digital electronic still camera. The memory card 12
This is a semiconductor memory device that accumulates image signals in a state where the image signals can be stored and held. However, the present invention is not limited to this, and can be effectively applied to other file storage devices such as a magnetic disk and an optical disk instead of the memory card 12.

The video signal of the input terminal 10 is supplied from, for example, a single-chip solid-state imaging device having an RGB segment array color filter. Input 10 is input to an analog-to-digital converter 16 where it is converted to a corresponding digital signal. Its output 18
Is input to the pre-processing circuit 20, where it undergoes pre-processing such as white balance adjustment and gradation correction. Preprocessed image signal 22
Is input to the signal processing circuit 24. The signal processing circuit 24 converts the luminance signal Y1 from the video signal corresponding to the pixel arrangement of the imaging device.
And a color difference signal C1. The luminance signal Y1 and the color difference signal C1 are input to the multiplexer 26.

Multiplexer 26 has two sets of inputs 28 and 30;
A selection circuit for selectively outputting any of them to its output 32. The output 32 of the multiplexer 26 includes a luminance signal Y and a color difference signal C. The former is input to an outline correction circuit 34, and the latter is input to a saturation correction circuit 36.

The contour correction circuit 34 is a signal correction circuit that compensates for the high-frequency component of the luminance signal Y in accordance with the input contour enhancement coefficient k, thereby enhancing the contour of the picture represented by the image signal. The contour corrected luminance signal is output to its output 38. The saturation correction circuit 36 is a signal correction circuit composed of a multiplier as shown, and correcting the color difference signal C according to the input saturation enhancement coefficient c. The chroma-corrected color difference signal is output to its output 40. In FIG. 1, in order to avoid complication of the drawing, the color difference signal C including the two color difference signals RY and BY is actually described as if it were a single signal. However, two color difference signal circuits including the saturation correction circuit 36 are actually provided for both signals. The saturation correction circuit 36 is configured so that the two color difference signals RY and BY can be independently corrected in accordance with the variation in the sensitivity of the color component RGB in the imaging device that is the signal source of the image signal. Have been.

The outputs 38 and 40 of the corrected luminance signal and color difference signal are connected to a reproduction output conversion circuit 42 and a data compression circuit 44. The reproduction output conversion circuit 42 is a circuit that synchronizes the luminance signal 38 and the color difference signal 40 and converts them into, for example, RGB signals. The converted video signal is supplied to the video monitor 14 from its output 46. The reproduction output conversion circuit 42 may output a video signal in the form of a luminance and color difference signal in the NTSC format. In any case, the circuit 42 is configured to output the video to the video monitor 14 in the form of a soft copy.

The data compression circuit 44 performs a luminance signal and a chrominance signal at its inputs 38 and 40, for example, performs an orthogonal transformation such as a discrete cosine transformation, encodes, quantizes, and outputs it to an output 48 in a data compressed form. Memory card 12
This is a functional unit that performs data compression and write control for writing data into the memory. The output 48 is detachably connected to the write input of the memory card 12 in this embodiment. In addition, memory card
Twelve address lines and control signal lines and their associated write / read control circuits of the memory card 12 are not shown in the figure to avoid complicating the figure.

The data read output 50 of the memory card 12 is detachably connected to the data decompression circuit 52. The data decompression circuit 52
A function of reading out the image signals stored in these from the memory card 12, expanding the compressed and coded data, and supplying data in the form of a luminance signal Y2 and a chrominance signal C2 to the input 30 of the multiplexer 26 and performing a read control. Department. Memory card 12, data compression circuit 44 and data decompression circuit
The interface to 52 is compatible with any type of memory card in this embodiment.

In the present embodiment, the signal processing circuit 24, the multiplexer 26,
The contour correction circuit 34 and the reproduction output conversion circuit 42 are mounted on a single semiconductor chip to form an integrated circuit 54. Among these circuits, a portion surrounded by a dotted line 56 is a portion shared for recording the image signal on the memory card 12 and reproducing it from now on. As described above, in the present embodiment, the same circuit is used for signal compensation for recording and reproduction, so that the circuit scale does not significantly increase.

Referring to FIG. 2, a specific configuration example of the contour correction circuit 34 is a bandpass filter (BP) that passes a high-frequency component of a luminance signal.
F) 80, a coring circuit 84 for coring the high-frequency output 82, a multiplier 86 for multiplying the high-frequency output 42 by the contour enhancement coefficient k, and a switch circuit 90 for switching the output of the multiplier 86. The luminance signal input Y to the output 92 of the switch circuit 90.
And an adder 94 for adding. The output of the adder 94 forms the circuit output 38 of the contour correction circuit 34.

The coring circuit 84 is a circuit having input / output characteristics as shown in FIG. 3, and its output 96 is connected to the control input of the switch circuit 90. The switch circuit 90 has a control input
When 96 is in a substantially zero state, the output 92 is cut off. The high-frequency luminance signal 82 is multiplied by a contour emphasis coefficient k by a multiplier 86. For relatively high level signal components, the output 88 of the multiplier 86 passes through the switch 90,
An adder 94 adds the signal to the original luminance signal 32. As a result, contour enhancement is performed.

As for the low-level component included in the high-frequency component 82, that is, the noise component, as shown in FIG.
Since output 96 of 84 is zero, output 88 of multiplier 86 is blocked from passing through switch 90. Therefore, contour enhancement is not performed on this portion a.

In the operating state, the image signal of input 10 is
When recording to 12, multiplexer 26 selectively connects input 28 to output 32. The image signal of the input 10 is converted into a digital signal by the analog / digital converter 16, and white balance adjustment and gradation correction are performed by the preprocessing circuit 20.
Next, the signals are converted into a luminance signal Y1 and a color difference signal C1 by a signal processing circuit 24, and are respectively passed through a multiplexer 26 to an outline correction circuit 34.
And input to the saturation correction circuit 36.

In the luminance signal Y, the contour portion of the picture is sharpened or emphasized in accordance with the contour emphasis coefficient k in the contour correction circuit 34, and the chroma in the color difference signal C is corrected in the chroma correction circuit 36 in accordance with the chroma correction coefficient c. Is done. The corrected luminance signal 38 and color difference signal 40 output from the correction circuit section 56 are input to the data compression circuit 44, where they are orthogonally exchanged, coded, quantized, and data-compressed. Memory card in form 12
Is written to.

The luminance signal 38 and the color difference signal output from the correction circuit section 56
40 or input to the playback output conversion circuit 42, where they are synchronized and output to the video monitor 1 in the form of RGB signals or NTSC format.
Supplied to 4. Thus, the visible image is displayed on the video monitor 14.

Reads image signals from the memory card 12 and monitors the image
The correction circuit section 56 is also used for reproducing the image in the step 14. In that case, the multiplexer 30 selects the input 30 and connects it to its output 32. The image signal stored in the memory card 12 is input from a readout output 50 to a data expansion circuit 52, where the data is expanded and the luminance signal is
It is input to the input 30 of the multiplexer 26 in the form of Y2 and a color difference signal C2. The read signals Y2 and C2 are input to the contour correction circuit 34 and the saturation correction circuit 36 through the multiplexer 26, respectively, and contour enhancement and saturation correction are performed in the same manner as described above. The corrected luminance signal 38 and color difference signal 40 are input to the reproduction output conversion circuit 42 and displayed as a visible image on the video monitor 14 in the same manner as described above. At that time, the data may be re-recorded on the memory card 12 through the data compression circuit 44.

As described above, in the present embodiment, the image signal data recorded on the memory card 12 is compressed. If the outline correction and the saturation correction are not performed, the high-frequency components will be recorded on the memory card 12 while being deteriorated.
However, in the present embodiment, even when an image signal is recorded, contour enhancement processing is performed to compensate for such deterioration of the high frequency component. Of course, when the image signal recorded on the memory card 12 is reproduced, the outline enhancement and the saturation correction are performed. These correction processes are performed using the same circuit portion 56 for both recording and reproduction.

Effects According to the present invention, signal degradation due to data compression can be compensated for by signal compensation processing such as contour enhancement and saturation correction in both cases of recording and reproduction of image signals. This signal compensation can avoid an increase in circuit scale if the same circuit can be used for recording and reproduction.

[Brief description of the drawings]

FIG. 1 is a functional block diagram showing an embodiment of an image signal processing apparatus according to the present invention, FIG. 2 is a functional block diagram showing a configuration example of a contour correction circuit in the embodiment shown in FIG. 1, and FIG. 3 is a graph illustrating input / output characteristics of the coring circuit shown in FIG. 2; Explanation of Signs of Main Parts 24 Signal Processing Circuit 26 Multiplexer 34 Outline Correction Circuit 36 Saturation Correction Circuit 42 Reproduction Output Conversion Circuit 44 Data Compression Circuit 52 Data Expansion Circuit

Claims (2)

(57) [Claims] 1. An input means for inputting an image signal, an outline emphasis circuit for emphasizing the outline of a picture represented by the image signal, a saturation correction circuit for correcting the saturation of the image signal, the outline emphasis circuit and the saturation Recording means for recording an image signal output from the correction circuit on an image signal recording medium; a reproduction circuit for outputting an image signal output from the contour enhancement circuit and the saturation correction circuit to an image display device; Reading means for reading an image signal recorded on the image signal recording medium; and selecting means for selectively supplying an image signal from one of the input means and the reading means to the contour enhancement circuit and the saturation correction circuit. An image signal processing device comprising: 2. The image signal processing apparatus according to claim 1, wherein said outline emphasizing circuit, saturation correcting circuit, reproducing circuit, and selecting means are mounted on a single semiconductor chip. apparatus.