JPH0767032A - Image processor - Google Patents

Abstract

PURPOSE:To prevent image degradation when an image is electrically enlarged by controlling the compressibility of image information corresponding to an electronic zoom magnification. CONSTITUTION:An imaging device 12 converts an optical image provided by a photographic lens 12 into a digital signal, and an A/D converter 14 converts the output of the imaging device 12 into a digital signal. The output of the A/D converter 14 is processed by a DSP 16 and inputted to an image extracting circuit 17. At the circuit 17, the image data of a line required for electronic zoom processing are extracted from the central part of the image data, and the extracted image data are outputted to a compression circuit 18. The circuit 18 compresses the image data. The compressed image data are temporarily stored in an image memory 22. The image data stored in the memory 22 are expanded by an expansion circuit 24 corresponding to the compressibility and inputted to an electronic zoom circuit 28. The circuit 28 electrically enlarges the input image into the size of a standard image. The enlarged digital image data are converted into analog signals by a D/A converter 30 and recorded in a magnetic tape 38.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus, and more particularly to an image processing apparatus having a function of electrically enlarging an image.

[0002]

2. Description of the Related Art An image pickup device having an image pickup means for converting an optical image into an electric signal, for example, a video camera, an electronic still video camera, a television camera or the like, is provided with an image memory for temporarily storing picked-up images. ,snap,
Functions for applying image effects such as image stabilization and electronic zoom are added.

An image memory for temporarily storing photographed images usually requires a storage capacity of at least one screen (field or frame). For example, if the luminance and color difference signals for one field are both stored in 8 bits, the storage capacity of 3 Mbits is required as it is, and not only the image memory becomes large but also the image memory becomes expensive.

Therefore, a structure has been proposed in which a compression encoding circuit is provided on the input side of the image memory and an expansion decoding circuit is provided on the output side of the image memory so that the storage capacity of the image memory can be reduced. ing.

[0005]

When the electronic zoom function is incorporated in the circuit configuration for performing the compression / expansion processing before and after the storage in the image memory as described above, the following adverse effects occur.

[0006] First, the electronic zoom is performed by cutting out a part of an image, and interpolating a pixel value that is insufficient for enlarging the cut-out part to a standard angle of view by using neighboring pixel values. It will be expanded.

Therefore, the larger the electronic zoom magnification, the greater the deterioration of the image (image quality) due to the above-described interpolation processing.

Further, a compression process is performed to temporarily store the image signal in the image memory, but the image quality is considerably deteriorated by this compression process.

Therefore, in the conventional image processing apparatus, when the electronic zoom is performed, the image is deteriorated by the compression / expansion process performed for temporary storage in the image memory, and the deteriorated image is subjected to the electronic zoom process. Will deteriorate.

The above-mentioned problems also apply to an image processing apparatus for converting an analog image signal into a digital image signal and recording it on a recording medium, for example, a digital VTR.

When recording a digital image signal on a recording medium, the digital VTR compresses the image signal.
Therefore, if the image subjected to the electronic zoom process described above is recorded, the image deteriorated by the electronic zoom due to the compression process is further deteriorated.

Under the circumstances, it is an object of the present invention to provide an image processing apparatus which solves the above problems and prevents image deterioration when an image is enlarged electrically.

[0013]

Under the above-mentioned object, the present invention provides, as one invention thereof, a compression means for compressing image information,
An image processing apparatus is provided, comprising: an enlarging means for electrically enlarging image information and a control means for controlling a compression rate of the compressing means according to an enlarging rate of the enlarging means.

[0014]

According to the above invention, since the compression rate of the image information is controlled according to the electronic zoom magnification, it is possible to prevent deterioration of the electronically zoomed image and record digital image data.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A video camera according to the first embodiment of the present invention will be described below as an example.

FIG. 1 is a block diagram showing the configuration of a camera-integrated VTR according to the first embodiment of the present invention.

In FIG. 1, 10 is a taking lens, 12 is an image pickup device for converting an optical image into an electric signal, 14 is an A / D converter for converting an analog image signal from the image pickup device 12 into a digital image signal, and 16 is an image pickup device. Digital signal processing circuit (DS
P), the DSP 16 performs known camera signal processing such as γ correction and color balance adjustment, and outputs an image signal in the form of an 8-bit luminance signal and a color difference signal, respectively. Note that, in the following, a luminance signal will be described for ease of description.

Reference numeral 17 denotes an image extraction circuit for extracting only the image data required from the image data output from the DSP 16 according to the electronic zoom magnification input by the operation unit 34.

Reference numeral 18 denotes 1/2 the output data of the DSP 16,
A compression circuit that enables compression to 1/4; 22 is a compression circuit 18
This is an image memory capable of storing image data for one screen compressed by, and in the image memory 22 of the present embodiment, image data for one screen can be stored by compressing standard image data for one screen to 1/4. It is possible to

Reference numeral 24 is a decompression circuit having a decompression rate corresponding to the compression rate of the compression circuit 18, 28 is an electronic zoom circuit for electrically enlarging the signal from the decompression circuit 24, and 29 is a DS.
A changeover switch for selecting the output from P16 or the output from the electronic zoom circuit 28, 30 a D / A converter for converting a digital signal into an analog signal, and 31 a D / A converter 3
An electronic viewfinder (EVF) for electrically displaying the signal output by 0, 34 is an operation unit for inputting an instruction of the electronic zoom function (for example, electronic zoom magnification, etc.), 36
Is a system control circuit, and in response to an instruction from the operation unit 34, an image extraction circuit 17, a compression circuit 18, and a decompression circuit 2
2. The electronic zoom circuit 28 (for example, zoom magnification) and the changeover switch 29 are controlled.

Reference numeral 37 is a recording processing circuit for performing a predetermined processing (for example, modulation) for recording on the magnetic tape 39, and 38.
Is a magnetic head and 39 is a magnetic tape.

Next, FIG. 2 shows an internal block diagram of the compression circuit 18.

In FIG. 2, the data output from the image extraction circuit 17 is input to the input terminal 40.

The pre-filter 42 removes the oblique component of the luminance data input from the input terminal 40 as a pre-sampling process. The sub-sampling circuit 44 thins out the output of the pre-filter 42 to 1/2 in the horizontal direction, and further compresses it to 1/2 by the DPCM circuit 46.

Here, in the case of the luminance signal, the state of compression will be specifically described. It is assumed that a brightness 640 pixel, 240 line, 8-bit field image of about 1.23 Mbit is input to the input terminal 40 as shown in FIG. 3A.

When this is subsampled by the subsampling circuit 44, the number of pixels in the horizontal direction is halved to 320, as shown in FIG.
It becomes 61 Mbit.

When this is further compressed by the DPCM circuit 46 from 8 bits to 4 bits, the depth direction is halved as shown in FIG. 3 (c), resulting in about 0.3 Mbit.

The changeover switch 41 can change the compression ratio of the data input from the input terminal 40 to 0, 1/2, 1/4. The changeover switch 41 is controlled by the system control circuit 36.

That is, when the compression process is not performed, the switch 41 is connected to the c side and the uncompressed image data is output to the image memory 22.

When the compression rate is set to 1/2, the switch 41 is connected to the b side, and the image data has a data amount of 1 by the pre-filter 42 and the sub-sampling circuit 44.
It is compressed to / 2 and the compressed image data is output to the image memory 22.

When the compression rate is set to 1/4, the switch 41 is connected to the side a, and the image data is prefilter 42, subsampling circuit 44 and DPCM circuit 46.
As a result, the data amount is compressed to 1/4 and the compressed image data is output to the image memory 22.

Next, an internal block diagram of the expansion circuit 24 is shown in FIG.

In FIG. 4, the image data read from the image memory 22 is input to the input terminal 50.

The DPCM decoding circuit 52 has an input terminal 50.
The 4-bit data from is subjected to DPCM decoding, and 8-bit data is output.

The interpolation circuit 54 is a sub-sampling circuit 44.
Interpolate the pixels thinned by. For example, insert a zero value. Alternatively, it may be an average value of pixel values on both sides or in the neighborhood.

The output of the interpolation circuit 54 is the post filter 56.
Is smoothed by. It is supplied from the force terminal 58 to the electronic zoom circuit 28.

That is, in the expansion circuit 24, the DPCM decoding circuit 52 expands the depth direction from 4 bits to 8 bits, and the interpolation circuit 54 doubles the number of pixels in the horizontal direction. As a result, the image data has 640 × 240 × 8 bits.

Further, the expansion switches can be changed by the changeover switches 51 and 53 in accordance with the compression ratio of the compression circuit 18.

That is, when the image data input to the input terminal 50 is not compressed, the switch 53 is connected to the side b and the image data input to the input terminal 50 is directly
Output from the output terminal 58 and output to the electronic zoom circuit 28.

When the image data input to the input terminal 50 is compressed to 1/2, the switch 51 is connected to the b side and the switch 53 is connected to the a side. The input image data is processed by the interpolation circuit 54 and the post filter 56.
Is expanded by a factor of 2 and input to the electronic zoom circuit 28 '.

When the image data input to the input terminal 50 is compressed to 1/4, the switches 51 and 53
Is connected to the a side. The input image data is DPCM
Decoding circuit 52, interpolation circuit 54 and post filter 56
Then, it is expanded four times and input to the electronic zoom circuit 28 '.

In the compression circuit 18 and the decompression circuit 24, although not shown, two circuits as shown in FIGS. 2 and 4 are provided for luminance and color difference.

The image processing operation when executing the electronic zoom function of the first embodiment will be described below. In this embodiment, the changeover switch 29 is connected to the c side during normal shooting (when the electronic zoom function is not executed), and the image memory 2
No image signal is stored in 2. When an instruction to execute the electronic zoom function is input from the operation unit 34, the changeover switch 29 is connected to the d side, and the image signal is transferred to the image memory 22.
Then, the electronic zoom process is performed.

First, the operation when an instruction to execute the electronic zoom function is input through the operation unit 34 and the electronic zoom magnification is less than 2 will be described. Here, the electronic zoom magnification will be described as an example of 1.5 times.

The image sensor 12 converts an optical image from the taking lens 10 into an electric signal, and the A / D converter 14 controls the image sensor 1.
The output of 2 is converted into a digital signal.

The output of the A / D converter 14 is processed by the DSP 16 and then input to the image extraction circuit 17.

In the image extracting circuit 17, as shown in FIG. 5, the horizontal portion 523 required for the electronic zoom processing starts from the central portion of the image data (horizontal 640 pixels × vertical 240 lines) photographed.
The image data of pixels × vertical 196 lines is extracted, and the extracted image data is output to the compression circuit 18.

The compression circuit 18 compresses the input image data to 1/4 as described above. The compressed image data is temporarily stored in the image memory 22.

The compressed image data stored in the image memory 22 is read out and input to the decompression circuit 24. The decompression circuit 24 decompresses the input compressed image data according to the compression rate as described above, and inputs it to the electronic zoom circuit 28.
The electronic zoom circuit 28 electrically enlarges the input image to a standard image size (see FIG. 5).

The enlarged digital image data is converted into an analog signal by the D / A converter 30, and the recording processing circuit 37 performs predetermined processing (for example, modulation processing),
Data is recorded on the magnetic tape 39 by the magnetic head 38. It is also possible to confirm the image electrically enlarged by the EVF 31.

Next, the operation when the instruction to execute the electronic zoom function is input by the operation unit 34 and the electronic zoom magnification is 2 times or more and less than 4 times will be described. Here, a case where the zoom magnification is 2 will be described as an example.

The image pickup device 12 converts the optical image from the taking lens 10 into an electric signal, and the A / D converter 14 shows the image pickup device 1.
The output of 2 is converted into a digital signal.

The output of the A / D converter 14 is processed by the DSP 16 and then input to the image extraction circuit 17.

In the image extracting circuit 17, standard image data (horizontal 640 pixels × vertical 24) taken as shown in FIG.
Image data of horizontal 453 pixels × vertical 170 lines required for electronic zoom processing is extracted from the central portion of (0 line),
The extracted image data is output to the compression circuit 18.

The compression circuit 18 compresses the input image data into 1/2 as described above. The compressed image data is temporarily stored in the image memory 22.

The compressed image data stored in the image memory 22 is read out and input to the decompression circuit 24. The decompression circuit 24 decompresses the input compressed image data by a factor of 2 as described above in accordance with the compression rate, and inputs it to the electronic zoom circuit 28. The electronic zoom circuit 28 electrically enlarges the input image to the size of the standard image (see FIG. 6).

The enlarged digital image data is converted into an analog signal by the D / A converter 30, and the recording processing circuit 37 performs predetermined processing (for example, modulation processing),
Data is recorded on the magnetic tape 39 by the magnetic head 38. It is also possible to confirm the image electrically enlarged by the EVF 31.

Next, the operation when the instruction to execute the electronic zoom function is input through the operation unit 34 and the electronic zoom magnification is 4 or more will be described. Here, the zoom factor is 4
Double will be described as an example.

The image sensor 12 converts an optical image from the taking lens 10 into an electric signal, and the A / D converter 14 controls the image sensor 1.
The output of 2 is converted into a digital signal.

The output of the A / D converter 14 is processed by the DSP 16 and then input to the image extraction circuit 17. In the image extraction circuit 17, as shown in FIG. 7, from the center portion of the standard image data (horizontal 640 pixels × vertical 240 lines) photographed, horizontal 320 pixels × vertical 12 required for the electronic zoom process.
Image data of 0 line is extracted, and the extracted image data is input to the compression circuit 18.

The compression circuit 18 does not compress the input image data and outputs it to the image memory 22. The image memory 22 temporarily stores uncompressed image data.

The image data stored in the image memory 22 is read out and input to the decompression circuit 24. Expansion circuit 24
Is input to the electronic zoom circuit 28 without performing expansion processing on the input image data. The electronic zoom circuit 28 electrically enlarges the input image to the size of the standard image (see FIG. 7).

The enlarged digital image data is converted into an analog signal by the D / A converter 30, and the recording processing circuit 37 performs predetermined processing (for example, modulation processing),
Data is recorded on the magnetic tape 39 by the magnetic head 38. Further, it is possible to confirm the image that is electronically enlarged by the EVF 31.

The camera-integrated digital VTR of the second embodiment will be described below.

FIG. 8 is a block diagram of a camera-integrated digital VTR of the second embodiment.

In FIG. 8, 100 is a taking lens and 10 is a taking lens.
2 is an image sensor, 104 is a camera processing circuit for performing a predetermined camera process on the image signal from the image sensor 102, and 106 is A
A / D converter, a switch 108, an electronic zoom circuit 110, a D / A converter 112, an electronic viewfinder (EVF) 114, a blocking circuit 116, 118
Is a DCT (Discrete Cosine Transform) circuit, 120 is a quantization circuit, 122 is a variable length coding circuit (VLC), 1
Reference numeral 24 is a buffer memory, 126 is a multiplexing circuit, 128 is a recording processing circuit, 130 is a magnetic head, 132 is a magnetic tape, 134 is a code amount control circuit, 136 is an operation unit for instructing execution of an electronic zoom function, 138. Is a system control circuit, and the system control circuit 138 controls the changeover switch 108, the electronic zoom 110, and the code amount control circuit 134 according to the operation of the operation unit 136.

The electronic zoom circuit 110 is composed of the image extraction circuit 17, the compression circuit 18, the image memory 22, the expansion circuit 24, and the electronic zoom circuit 28 described in the first embodiment. The enlargement processing is also similar to that described in the first embodiment.

First, the recording processing operation in normal photographing (without using the electronic zoom) will be described.

The image pickup device 12 converts the optical image from the taking lens 10 into an electric signal, and the camera processing circuit 104 performs predetermined signal processing.

The image data output from the camera processing circuit 104 is converted into a digital signal by the A / D converter 106. The converted digital signal is sent to the switch 108.
It is input to the blocking circuit 116 and the D / A converter 112 via (a side connection).

In the D / A converter 112, the digital signal is converted into an analog signal and the image photographed by the EVF 114 can be displayed.

On the other hand, the blocking circuit 112 divides the block into 8 × 8 pixels. The DCT circuit 118 performs orthogonal transformation on the divided block data to transform it into frequency components. The frequency coefficient data output from the DCT circuit 118 is input to the quantization circuit 120. The quantization circuit 120 divides the set of data coefficients for each frequency component by a numerical value controlled as described below, rounds down the decimal places, and reduces the number of bits to compress the entire quantized data amount.

The quantized data is input to the VLC 122. Here, in order to convert into a one-dimensional data string, horizontal and vertical low-frequency components are zigzag-scanned into high-frequency components, the data is rearranged, and variable-length coding is performed on this data. The variable-length coded data is input to the code amount control circuit 134 and the buffer memory 124.

The code amount control circuit 134 calculates the data amount of the encoded data, and the quantization circuit 120 calculates the encoded data so that the encoded data has a predetermined data amount according to the calculation result.
Control the quantization factor of.

On the other hand, in the buffer memory 124, the coded data is transferred at a constant data rate to the multiplexing circuit 12.
Output to 6.

The accumulated amount of data stored in the buffer memory 124 is input to the code amount control circuit 134, and the quantization coefficient of the quantization circuit 120 is controlled so that the buffer memory 124 does not underflow or overflow. .

Further, the quantization amount information indicating the quantization coefficient of the quantization circuit 120 is output from the code amount control circuit 134 to the multiplexing circuit 126, and the multiplexing circuit 126 outputs the encoded data and the quantization step. The recording processing circuit 128 performs multiplexing with information and formatting for recording.
Then, a predetermined recording process (eg, modulation process) is performed, and the data is recorded on the magnetic tape 132 by the magnetic head 130.

The recording processing operation using the electronic zoom function will be described below.

Only the processing part different from the recording processing operation when the electronic zoom function is not used will be described.

When the execution of the electronic zoom function is instructed by the operation unit 136, the electronic zoom control circuit 138 connects the switch 108 to the side b.

The electronic zoom control circuit 138 is operated by the operation unit 13
The electronic zoom circuit 110 is controlled according to the zoom magnification designated by 6.

For example, if there is an instruction from the operation unit 136 that the electronic zoom magnification is 2 ×, the electronic zoom circuit 110 is set to the state shown in FIG.
Standard image data (horizontal 640 pixels × vertical 24
Image data of the central portion (horizontal 453 pixels × vertical 170 lines) is extracted from 0 line) and enlarged to a standard size by interpolation.

Further, the electronic zoom control circuit 138 outputs the electronic zoom magnification information to the code amount control circuit 134.

The code amount control circuit 134 responds to the input electronic zoom magnification information in accordance with the input electronic zoom magnification information, and quantizes the circuit 12 more than the normal photographing.
The quantized coefficient of 0 is shifted in the smaller direction.

[0085]

As described above, according to the present invention,
Since the compression / expansion rate of the image information is controlled according to the electronic zoom magnification, it is possible to prevent deterioration of the electronically zoomed image and record digital image data.

[Brief description of drawings]

FIG. 1 is a block diagram of a camera-integrated VTR according to a first embodiment of the present invention.

FIG. 2 is an internal circuit diagram of a compression circuit 18 in FIG.

FIG. 3 is a diagram illustrating a compression processing operation of a compression circuit 18.

FIG. 4 is an internal circuit diagram of a decompression circuit 24 in FIG.

FIG. 5 is a schematic explanatory diagram when an electronic zoom magnification is 1.5 times.

FIG. 6 is a schematic explanatory diagram when the electronic zoom magnification is 2 ×.

FIG. 7 is a schematic explanatory diagram when the electronic zoom magnification is 4 ×.

FIG. 8 is a block diagram of a camera-integrated digital VTR according to a second embodiment of the present invention.

[Explanation of symbols]

 17 image extraction circuit 18 compression circuit 22 image memory 24 expansion circuit 28, 110 electronic zoom circuit 36 system control circuit 116 block circuit 118 DCT circuit 120 quantization circuit 134 code amount control circuit

Claims (3)

[Claims] 1. A compression means for compressing image information, an expansion means for electrically expanding the image information, and a control means for controlling the compression means according to an expansion rate of the expansion means. Image processing device. 2. A transforming means for transforming image information into frequency component data, a quantizing means for quantizing the transformed data transformed by the transforming means, and encoding the data quantized by the quantizing means. Encoding means, instructing means for instructing to electrically enlarge the image information, enlarging means for electrically enlarging the image information according to the output of the instructing means, and depending on the output of the instructing means And a control means for controlling the quantization step of the quantization means. 3. Extraction means for partially extracting the input image information, storage means for storing the partial image information extracted by the extraction means, and electrically the image information stored in the storage means. An image processing apparatus comprising: an enlarging unit for enlarging and a control unit for controlling a size of the partial image information extracted by the extracting unit according to an enlarging magnification of the enlarging unit.