JPH0514743A - Picture encoding device and decoding device thereof - Google Patents

Abstract

PURPOSE:To encode picture information at high speed and with high efficiency, and simultaneously, to transmit the picture information of high capacity such as the picture of high picture quality in a short time even in the case that the transmission line of small capacity is used. CONSTITUTION:When a coherent picture outputted from a picture output part 10 is Fourier-transformed by a lens 12, and is made incident upon a photoelectric conversion element 14 together with reference light, interference is caused between the two, and a Fourier transformation hologram is formed. This hologram image is photoelectric-converted by a photoelectric conversion element 14, and an electric signal after conversion is encoded by an encoder 16. Since the picture information has a feature that signal energy is concentrated to a low frequency component and visual sensitivity is duller for a higher frequency component, the picture information is encoded so that quantized bits are distributed more in the low frequency component and less in the high frequency component.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for encoding and decoding image information, and more particularly to an image encoding apparatus suitable for encoding image information with high efficiency and a decoding apparatus therefor. .

[0002]

2. Description of the Related Art As a technique for efficiently encoding image information, for example, an orthogonal transformation is performed by orthogonally transforming an image into a spatial frequency domain and allocating the number of encoding bits to this in accordance with the image and visual characteristics. Coding techniques are known (see, for example, the Television Image and Information Engineering Handbook).

In this method, the image is divided into blocks each having several pixels to several tens of pixels, and orthogonal transformation is performed for each block. There are Hadamard transform, Fourier transform, etc. as the transform method, but the discrete cosine transform (DC
T) tends to be used. This transform coefficient is encoded and transmitted.

At this time, it is used that the correlation of the image signals appears as a tendency of concentration of signal energy in low frequency components in the frequency domain. That is, a large number of coded bits are assigned to the low frequency component having a large energy component. On the other hand, a small number of coding bits is assigned to a high frequency component that has a small energy component and is visually insensitive. As a result, the number of coding bits as a whole is reduced, and coding can be performed with high efficiency.

[0005]

However, in such a method, since orthogonal transformation is performed by time-series arithmetic processing of signals, it takes a lot of time to arithmetically process image information having a large amount of information. There is. For example, even if one screen is divided into blocks of 8 × 8 pixels and conversion processing is performed for each block, 16 × 2 = 32 calculations are required even if the high-speed calculation method is applied to each block.

The present invention focuses on this point.
The purpose of is to perform coding of image information at high speed and with high efficiency. The second purpose is to transmit high-capacity image information such as high-quality images in a short time even when using a small-capacity transmission path.

[0007]

According to the present invention, in an image encoding apparatus for encoding image information, image output means for optically outputting the image information as a coherent image,
An image conversion means for optically converting the image output as a Fourier transform hologram into a spatial frequency region, a photoelectric conversion means for converting this Fourier transform hologram into an electric signal, and a spatial frequency for the converted electric signal. Encoding means for allocating the number of quantized bits according to the level of.

According to a main aspect, recording means for recording the Fourier transform hologram is provided, and the image information is divided into a plurality of blocks, and an encoding process by image conversion is performed for each block. Another invention is characterized in that the image information encoded by the image encoding device is decoded by a process reverse to the encoding.

[0009]

According to the present invention, the coherent image is optically transformed into the spatial frequency domain as a Fourier transform hologram. Then, photoelectric conversion is performed on the converted hologram image, and the quantization bit number is assigned according to the spatial frequency.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An embodiment of an image coding apparatus and its decoding apparatus according to the present invention will be described below with reference to the accompanying drawings. <Embodiment 1> First, Embodiment 1 of the present invention will be described with reference to FIGS. FIG. 1 shows the first embodiment.
The configuration of the image encoding device according to the above is shown. In the figure, a lens 12 is provided on the image output side of the image output unit 10, and a photoelectric conversion element 14 is provided on the light output side of the lens 12. An input side of the encoding device 16 is connected to a converted electric signal output side of the photoelectric conversion element 14. Further, in addition to the coherent image that is incident as indicated by arrow FA, the photoelectric conversion element 14 is also configured so that reference light that is a plane parallel wave is incident as indicated by arrow FB.

Of these, the image output section 10 outputs an image as coherent information light, and is constructed as shown in FIG. 3, for example. In the example of FIG.
The laser beam output from the laser light source 100 is expanded by the beam expander 102, and then enters the film 104 of a camera, a movie, or the like. As a result, the information of the film 104 is output as a coherent image as shown by the arrow FC.

In the example of FIG. 1B, an electric signal address type liquid crystal panel 106 is provided in place of the film 104, and the liquid crystal panel 106 is driven by a driving device 108 based on an image signal input from the outside. To be done. Then, an image is displayed on the liquid crystal panel 106, and when laser light is incident on this, a coherent image is similarly obtained.

In the example of FIG. 1C, a photo-address type spatial light modulator 110 is used instead of the film 104 and the liquid crystal panel 106. Spatial light modulator 110
Is the photoconductive layer 116, the dielectric mirror 118, the light modulation layer 1 between the transparent electrodes 114 formed on the glass substrate 112.
20 is formed by stacking each. A driving power supply 122 is connected between the transparent electrodes 114.

When writing light containing image information is incident on the spatial light modulator 110 (arrow FD), the photoconductive layer 116 becomes conductive according to the intensity distribution of the writing light. Then, correspondingly, the voltage of the driving power supply 122 changes the voltage of the optical modulation layer 1.
20 is applied. In this state, when the beam splitter 124 irradiates the light modulation layer 120 with laser light, the laser light is optically modulated according to the intensity distribution of the writing light, that is, the incident image information due to the electro-optic effect.
The coherent image obtained by this is output from the beam splitter 124.

Next, returning to FIG. 1, the lens 12 is for performing Fourier transform, and the image output section 10 and the photoelectric conversion element 14 are arranged at the position of the focal length f thereof. The photoelectric conversion element 14 is composed of, for example, a CCD image sensor or the like.

Next, the operation of the first embodiment configured as described above will be described with reference to FIG. On the one hand, the coherent image output from the image output unit 10 is Fourier-transformed by the lens 12 and enters the photoelectric conversion element 14 (arrow FA). On the other hand, the reference light enters the photoelectric conversion element 14 at an appropriate angle (arrow FB). Then, interference occurs between the two and a Fourier transform hologram is formed, and this enters the photoelectric conversion element 14. In the photoelectric conversion element 14, this Fourier transform hologram is photoelectrically converted.

By the way, in the Fourier transform hologram, as shown in FIG. 2A, position coordinates (X1, Y1, Z)
The image represented by is the spatial frequency coordinates (X2, Y2, Z)
Is converted into the spatial frequency domain by
E). Here, the Z axis of the spatial frequency coordinate, that is, the optical axis corresponds to the spatial frequency “0”. Also, from the Z axis, X1,
As the distance increases in the Y1 direction, the high frequency component of the spatial frequency corresponds. Such a Fourier transform hologram is photoelectrically converted by the photoelectric conversion element 14, and the converted electric signal is supplied to the encoding device 16.

As described above, the image information has the following tendency. (1) Signal energy is concentrated in low frequency components, and high frequency components are small. (2) For visual sense, the higher the frequency component, the less sensitive it is.

Therefore, in the encoding device 16, the quantized bits for the input photoelectric conversion signal are distributed so that the low-frequency component is large and the high-frequency component is small, and the information amount is compressed (see FIG. See B)).

As described above, according to the present embodiment, attention is paid to the parallelism, high speed, and Fourier transform action of the coherent optical system possessed by the optical operation, and the conversion of the coherent image into the spatial frequency domain results in extremely high speed. The image is orthogonally transformed. Then, when the obtained optical image is encoded, the number of quantization bits is distributed according to the spatial frequency.

Therefore, as compared with the conventional time-series processing of signals, the calculation processing time required for image information of one screen can be extremely shortened, and high-speed and highly efficient image information encoding can be performed. . Further, when applied to a large-capacity image such as a movie film, the transmission can be performed at a higher speed than a telecine or the like by using the same transmission line as the conventional one.

<Second Embodiment> Next, a second embodiment of the present invention will be described with reference to FIG. This embodiment is an example of an image decoding apparatus which decodes the image signal encoded in the above embodiment. In the figure, the output side of the drive unit 22 is connected to the signal input side of the liquid crystal panel 20, and the encoded image signal is input to this drive unit 22. In addition, the hologram reproduction light from the laser light source 24 is displayed on the liquid crystal panel 20 by the beam expander 2.
6 is input. LCD panel 2
On the output side of 0, a photoelectric conversion element 30 is provided via a lens 28 for inverse Fourier transform. A photoelectric conversion output device 32 is connected to the photoelectric conversion element 30,
The decoded image signal is now to be output.

According to this embodiment, the coded image signal is inputted to the liquid crystal panel 20 through the driving device 22. On the other hand, the liquid crystal panel 20 is irradiated with the laser light output from the laser light source 24 via the beam expander 26. Therefore, the liquid crystal panel 20 reproduces an image based on the encoded image signal. That is, the Fourier transform hologram compressed by the first embodiment is reproduced. This hologram image is inversely Fourier transformed by the lens 28. Therefore, the photoelectric conversion element 30
The original image is reproduced above, and the electric signal output from the photoelectric conversion output device 32 becomes a decoded image signal.

<Third Embodiment> Next, referring to FIG.
A third embodiment of the present invention will be described. In this embodiment, for example, the liquid crystal panel 106 of FIG. 3B is divided into a plurality of blocks. For example, in the embodiment described above, FIG.
As shown in (A), the entire liquid crystal panel 106 corresponds to the image BF of one frame, and the entire image is processed at the same time. However, in this embodiment, as shown in FIG. 7B, the image BF of one frame is composed of a plurality of blocks B1, B.
2, ..., B6, and the encoding and decoding processing according to the above-described embodiment is performed for each block. The image dividing process is performed by the driving device 108.

Therefore, in this embodiment, a spatial light modulator such as a liquid crystal panel having a small pixel capacity can be used as an output unit for a coherent image, and the accuracy of the hologram forming optical system side is relaxed.

<Embodiment 4> Next, referring to FIG.
A fourth embodiment of the present invention will be described. It should be noted that the same reference numerals are used for the constituent parts that are the same as or correspond to those in the above-described embodiments. In the first embodiment, the Fourier transform hologram is formed on the photoelectric conversion element 14, but in this embodiment, a hologram image is recorded on the recording medium 40 (see FIG. 7A). The recording medium 40 has a light modulation film 44 on the transparent electrode 42.
Is formed, and the recording heads 46 are arranged to face each other. The recording head 46 has a transparent electrode 48.
A photoconductive film 50 is formed on the top of the photoconductive film 50, and a drive power source 52 is connected between the transparent electrodes 42 and 48.

As the light modulation film 44, PLZT or a liquid crystal polymer composite film is used. As the photoconductive film 50,
a-Si (amorphous silicon) or PVK is used. The recording medium 40 and the recording head 46 may be integrally formed as shown in FIG.

The Fourier transform hologram is recorded by the recording head 46.
When formed on the photoconductive film 5, the photoconductive film 5 is formed corresponding to the intensity distribution.
0 becomes conductive. Then, an electric charge image is formed on the light modulation film 44 of the recording medium 40 by the action of the driving power supply 52, and thereby a hologram image is recorded on the recording medium 40.

Next, reading of the hologram image from the recording medium 40 is performed as shown in FIG. As shown in the figure, the recording medium 40 on which the image is recorded is irradiated with light by an appropriate light source 54, and the recorded image is read out. This image is formed on the image pickup device 58 via the optical system 56, and its photoelectric conversion is performed here. The subsequent encoding process is the same as in the first embodiment.

<Other Embodiments> The present invention is not limited to the above embodiments. For example, a silver salt film, a frost medium or the like may be used as the recording medium of the Fourier transform hologram. Further, as the spatial light modulator, a transmissive type may be used in addition to the reflective type.

[0031]

As described above, according to the present invention, a coherent image is transformed into a spatial frequency domain as a Fourier transform hologram, and at the time of encoding this hologram image, the number of quantization bits corresponding to the spatial frequency is changed. Since distribution is performed, image information can be encoded at high speed and with high efficiency, and high-capacity image information such as high-quality images can be transmitted in a short time even when using a small-capacity transmission path. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing an embodiment of an image encoding device according to the present invention.

FIG. 2 is an explanatory diagram showing the operation of the first embodiment.

FIG. 3 is an explanatory diagram illustrating a configuration example of an image output unit.

FIG. 4 is a configuration diagram showing an embodiment of an image decoding device according to the present invention.

FIG. 5 is an explanatory diagram showing another embodiment.

FIG. 6 is an explanatory diagram showing another embodiment.

[Explanation of symbols]

10 ... Image output section (image output means), 12 ... Lens (image conversion means), 28, 56 ... Lens, 14, 30 ... Photoelectric conversion element (photoelectric conversion means), 16 ... Encoding device (encoding means), 20 ... Liquid crystal panel, 22 ... Driving device, 24 ... Laser light source, 26 ... Beam expander, 32 ... Photoelectric conversion output device, 40 ... Recording medium (recording means), 46 ... Recording head, 54 ... Light source, 58 ... Imaging element (Photoelectric conversion means),
BF ... image, B1-B6 ... block, f ... focal length, F
A, FB, FC, FD, FE ... Arrows.

[Procedure amendment]

[Submission date] December 16, 1991

[Procedure Amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction content]

By the way, in the Fourier transform hologram,
As shown in FIG. 2A, position coordinates (X1, Y1, Z)
The image represented by the spatial frequency coordinates (X2, Y
2, Z) is converted to the spatial frequency domain (arrow FE in the figure). Here, the Z axis of the spatial frequency coordinate, that is, the optical axis corresponds to the spatial frequency “0”. Further, as the distance increases from the Z axis in the X1 and Y1 directions, the higher frequency component of the spatial frequency corresponds. Such a Fourier transform hologram is photoelectrically converted by the photoelectric conversion element 14, and the converted electric signal is supplied to the encoding device 16.

Claims (4)

[Claims] 1. An image encoding apparatus for encoding image information, wherein image output means for optically outputting the image information as a coherent image, and an image output thereby is optically converted as a Fourier transform hologram into a spatial frequency signal. Image conversion means for converting into a region, photoelectric conversion means for converting this Fourier transform hologram into an electric signal, and encoding means for allocating the number of quantization bits to the converted electric signal according to the level of the spatial frequency. An image coding apparatus comprising: 2. The image coding apparatus according to claim 1, further comprising a recording unit that records the Fourier transform hologram. 3. The image coding apparatus according to claim 1, wherein the image information is divided into a plurality of blocks, and coding processing is performed by image conversion for each block. . 4. An image decoding device for decoding encoded image information, wherein the image information encoded by the image encoding device according to any one of claims 1 to 3 is:
An image decoding device characterized in that decoding is performed by a process reverse to encoding.