JP3038586B2 - Video recording device with video pre-recording confirmation function - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a video recording apparatus adapted to an electronic still video or the like and having a function of confirming a video to be recorded before recording.

[Prior art] In electronic still video, high S / N ratio of video data,
It is necessary to digitally process video data and record it in a semiconductor memory such as an IC card in order to reduce the size of the device.However, at present, the price of the memory is high, so video data must be input as it is. If it is stored in memory, the cost of recording one screen is high.

Further, the degree of integration of the memory is not sufficient, and the number of screens that can be recorded by one card is limited. Therefore, it has been considered to compress the data and record it in the memory, but it was not clear how the compressed image quality deteriorated unless it was reproduced.

Note that, for example, as disclosed in Japanese Patent Application Laid-Open No. 1-165267, there is known an apparatus in which whether or not photographed video information is intended by a photographer is selected before recording by checking. However, this is to see the video information itself, not to see the video after compression,
Therefore, it is not possible to see the degree of image degradation due to compression.

[Problems to be Solved by the Invention] The present invention solves the above-mentioned problem. Before compressing and recording the video information, the video information is displayed so that the deterioration of the image quality can be visually confirmed. An object of the present invention is to provide a video recording device capable of performing video recording at a certain compression ratio.

Means for Solving the Problems In order to achieve the above object, the present invention provides a video recording apparatus having a function of compressing a video signal and recording the video signal on a recording medium. Signal processing means for processing a video signal so as to form a video having an excellent image quality, and display means for displaying an image based on the video signal processed by the signal processing means. .

In the above, setting means for setting a compression rate of the video signal may be provided, and the signal processing means may perform processing according to the set compression rate on the video signal.

Further, the present invention provides a video recording apparatus having a function of compressing a video signal and recording the video signal on a recording medium, a signal processing unit for re-expanding the signal after the image quality has been degraded by the compression, and And a display unit for displaying an image based on the video signal expanded by the signal processing unit before recording the signal on the recording medium.

The present invention also provides a video recording apparatus having a function of compressing a video signal obtained by capturing an image of a subject and recording the compressed video signal on a recording medium, wherein the subject has an image quality substantially equivalent to a video based on the compressed signal. An optical system for optically creating an image is provided.

In the above, the optical system may include a finder optical system for forming a subject image and an optical element having a filter function installed in an optical path of the finder optical system. Still further, in the above, the optical system may include an electronic viewfinder optical system for forming a subject image, and an optical element having a filter function installed in an optical path of the viewfinder optical system. it can.

[Operation] With this configuration, before compressing and recording the video data, it is possible to display the video at the compression rate, and to check the degree of deterioration of the image quality by looking at the video.

Hereinafter, an outline of a still video system according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration example of a still video camera using a solid-state memory. In FIG. 1, the imaging system includes an imaging lens 1, a mechanical shutter 2, an imaging device 3, and an aperture 4. When the shutter 2 is opened, a light beam passing through the imaging lens 1 forms an image on the imaging device 3. Image. At normal times other than the time of imaging, the light beam that has passed through the imaging lens 1 is guided to the finder optical system 6 by the mirror 5, and through this finder optical system 6, the photographer can check the subject and its framing.

The recording system includes an amplifier 7 for amplifying the video signal from the imaging element 3 and an A / D for converting the video signal from analog to digital.
A converter 8, a buffer memory 9 for temporarily recording a signal after A / D conversion, an image memory 10 as a recording medium, a digital operation circuit 11 for performing compression processing when recording a video signal, and a system controller 12 for overall control It is composed of

Further, a photometric element 13 for measuring subject brightness for exposure control is provided, and photometric data from the element 13 is A / D-converted by an A / D converter 14 so that the system controller 12
Is input to Based thereon, the system controller 12 controls the aperture 4. The system controller 12 includes a release switch SW1, a compression mode selection switch SW2 for appropriately selecting a mode from at least one or more compression modes (including a non-compression mode), and a function upgrade card 1
5 and are connected.

To explain the basic operation of the above configuration, when the photographer presses the release switch SW1, the system controller 12 performs A / D conversion of the light amount obtained by the photometric element 13 by the A / D converter 14, and the system controller 12 Based on the calculation, the exposure value is determined, the value of the aperture 4 is determined, the mirror 5 is raised, the opening time of the shutter 2 is determined, and the shutter 2 is opened and closed. After the shutter 2 is closed, the image signal photoelectrically converted and stored in the image sensor 3 is transferred by a clock provided by a timing generator (not shown), and is amplified by an amplifier 7.
The data is converted into a digital value by the A / D converter 8 and stored in the buffer memory 9. The stored video signal is
The digital operation circuit 11 performs color separation processing, γ processing, white balance processing, and matrix processing, and performs Y, R−Y, B−
After conversion to the Y signal form, compression processing is performed. The compressed signal is then written through a buffer memory 9 to an image memory 10 as a storage medium. As the image memory 10, for example, a memory card or the like may be used.

In the above photographing operation, the photographer selects one mode from at least one or more compression ratios or compression methods by using the compression mode selection switch SW2. The system controller 12 determines the compression ratio or compression method of the signal to be recorded based on the information of the switch SW2.
Before the compressed signal is written from the buffer memory 9 to the image memory 10 as described above, an image corresponding to the selected compression mode can be viewed on the finder optical system 6 (the configuration for this purpose). Will be described in detail in FIG. 4 and thereafter.) The photographer confirms the deterioration due to the compression with the finder optical system 6, selects the compression mode or the non-compression most suitable for the purpose of photographing, and records a video image having a satisfactory image quality in the image memory 10.

It is convenient that the compression mode is set to a predetermined mode in an initial state. In particular, the optimal compression mode is set according to the capacity of the card and the function-up card (the card is selected by the photographer according to the photographing intention, and the shutter speed and aperture that are most suitable for the photographing intention are determined by the card information). It should just be.

A method of compressing a video signal will be described with reference to FIGS. As a compression method, each of the Y, RY, and BY signals is divided into, for example, a block of 16 × 16 pixels, and two-dimensional cosine transform coding (DCT) is performed in the block. Cosine transform coding is a method of compressing data using a transform called cosine transform. The cosine transform is one of orthogonal transforms represented by the Fourier transform and the Hadamard transform, and is said to be a transform method capable of performing encoding with the highest compression efficiency when using it. Original image f
Assuming that (i, j), the coefficient obtained by the transformation is F (u, v), and the number of pixels of the image is N × N, the two-dimensional cosine transformation and the inverse transformation are represented by the following equations.

By the cosine transform, as shown in FIG. 2, the density information f (i, j) of the image is developed into an amplitude value F (u, v) represented by a function of the spatial frequency u, v. By performing the cosine transform, the properties of the data are converted into a more easily compressible form. It is known that the transform coefficient obtained by the cosine transform has the following properties.

(A) The conversion coefficients are one DC component F (0,0) and 255 (when N = 16) AC components F (u, v) (where u + v
≠ 0. ), As shown in FIG. 3A, among the AC components, the AC component closer to the DC component tends to have a larger coefficient value. That is, information necessary for constructing an image is relatively concentrated on the low frequency side.

(B) As shown in FIG. 3 (b), the distribution of the conversion system numerical values of all the AC components of all the blocks is a Laplace distribution having a peak at zero.

(C) The distribution of the conversion system numerical value of the AC component of each block can be approximated to a Laplace distribution having a peak at zero. The spread of the distribution varies from block to block. As the density of each pixel in the block changes more steeply, the spread of the distribution of the conversion coefficients increases, the average amplitude value of the coefficients increases, and the conversion coefficients of the high-frequency components also take larger values.

(D) The distribution of conversion system numerical values of AC components having the same frequency in all blocks is a Laplace distribution having a peak at zero,
The spread of the distribution is greater for lower frequency components. As described above, the property of data having various density distributions for each image is led to a certain property that is not image-dependent (in this case, a property of a Laplace distribution having a peak at zero), thereby providing a statistical property. Compression using the technique becomes possible.

First, the image data is divided into block images f (i, j) (i, j = 0, 1, 2,..., 15) each including 16 × 16 pixels. Then 16x1
A 6-dimensional block image f (i, j) is subjected to a two-dimensional DCT, and a transform coefficient matrix F (u, v) (u, v = 0,1,2,
…, 15). The conversion coefficient takes a real value. The way of quantization is changed according to the compression ratio selected by the compression mode selection switch SW2. That is, if all 8 bits are given to F (u, v), no compression is achieved, but if the number of high-frequency bits is reduced according to the above-mentioned Laplace distribution, compression is achieved. The amount to be reduced is written in the ROM in advance, and data is read from the ROM in accordance with the setting of the compression mode selection switch SW2. By performing this quantization, the image data is compressed. As described above, in the compression method according to the present embodiment, high-frequency components are mainly compressed, so that the compression reduces the high-frequency components.

FIG. 4 shows a detailed view of the imaging system of FIG. A method for confirming the deterioration of the compressed video in this embodiment will be described with reference to FIG.

As shown in the drawing, at least one spatial low-pass filter or light scattering filter is freely inserted as an optical member 22 in the optical path of the finder optical system 6, and the actuator 21 is driven by the system controller 12 at the time of compression. By inserting a spatial low-pass filter or a light scattering filter, an image with a reduced high-frequency component or an image with a deteriorated S / N ratio is displayed on the finder optical system 6. The photographer can confirm the deterioration of the compressed image by looking at this display. As the spatial low-pass filter, a filter using birefringence such as quartz, or a filter utilizing diffraction such as a phase-type low-pass filter can be adopted.

In order to select a compression ratio from a plurality of values, a plurality of spatial low-pass filters or light scattering filters may be freely inserted. For example, if the compression ratio is 3
If the compression rate is variable, three low-pass filters can be freely inserted, and a low-pass filter having a lower cutoff frequency may be inserted as the compression rate increases. If the cutoff frequency is low and the high cutoff frequency is B, the compression rate may be inserted in the order of A + B, A, B in descending order.

In the present embodiment, the spatial low-pass filter or the light scattering filter is inserted into the finder optical system, but may be inserted into the imaging lens 1. Further, in the above embodiment, the optical viewfinder has been described as an example. However, when an electronic viewfinder (for example, a liquid crystal TV system) has a sufficient resolution, a spatial low-pass filter or a light scattering filter is provided in the optical system of the electronic viewfinder. May be inserted.

Next, another embodiment will be described. As the optical member 22 in FIG. 4, an element having an electro-optical effect in which birefringence is varied by an electric field, for example, PLZT as shown in FIG. 5 is used. The function of the spatial low-pass filter is obtained by the action of the birefringence. In this case, the optical member 22
May be fixed.

In this embodiment, the voltage applied to the optical member 22 is changed according to the compression ratio and the compression method (that is, the electric field is changed).
Thereby, the birefringence can be changed, and thus the action of the spatial low-pass filter can be changed.

Also, instead of the element having the electro-optic effect, an ultrasonic light polarization element using a change in the refractive index generated in the medium by the acousto-optic effect as the phase (diffraction) may be used. A function as a spatial low-pass filter is obtained by the action of this diffraction. By changing the frequency of the high-frequency sine wave signal applied to the ultrasonic light polarizing element, the angle of the diffracted light can be changed. Examples of such an element include fused quartz and As ₂ S ₂ .

In this embodiment, by changing the frequency of the high-frequency signal applied to the optical member 22 according to the compression ratio and the compression method, the diffraction angle can be changed, and thus the action of the spatial low-pass filter can be changed.

Further, an element having an electro-optical light scattering effect is used instead of the ultrasonic light polarizing element, and the scattering degree is changed by changing the applied voltage, whereby the element can be used as a spatial low-pass filter or an S / N deterioration filter. Examples of such an element include PLZT. By changing the voltage applied to the element according to the compression ratio and the compression method to change the degree of scattering, it is possible to reduce the high-frequency component and to form an image with a deteriorated S / N ratio.

Further, as another embodiment, a plurality of images are created by moving some elements of the imaging optical system or the viewfinder optical system (for example, shaking at a cycle of 50 Hz or more), and a state equivalent to inserting a spatial low-pass filter is obtained. May be obtained. For example, a parallel flat plate made of transparent glass, plastic material, or the like is used as the optical member 22 in FIG. 4, and the parallel flat plate is configured to be able to swing a small angle in the θ1 and θ2 directions as shown in FIG. The seventh
As shown in the figure, the light beam is also shaken by swinging the same plate by a small angle (in the drawing, the shake in the horizontal direction is shown).
Thereby, a double image can be formed.

FIG. 8 shows a pattern of movement of an image when the parallel plane plate is shaken, and FIG. 9 shows a driving sequence of the parallel plane plate. In this example, the plane-parallel plate is driven so that the image moves between the positions "1" and "2" every 1/120 second. As a result, a function equivalent to a spatial low-pass filter without flicker can be obtained by using the afterimage of the human eye. In order to prevent flickering, the time in the state of “1” or “2” in the above driving must be shorter than 1/50 second. In addition, the characteristics of the spatial low-pass filter function can be changed by changing the amount of movement of the image. Therefore, the compression ratio,
By changing the movement amount according to the compression method, an image similar to the compressed image can be created.

Also, in FIG. 8, the spatial low-pass filter is provided only in one direction. However, as shown in FIG. 10, by driving the same plate so that the image moves in the horizontal and vertical directions, horizontal and vertical It can function as a spatial low-pass filter in the direction. FIG. 11 shows a driving sequence of the parallel flat plate at that time. The horizontal and vertical drive sources may be independent.

In this example, first, the plane-parallel plate is swung in the θ1 direction (FIG. 6), whereby the image moves between the horizontal directions “1-2” in FIG. At this time, since the image does not move in the θ2 direction (FIG. 6), the image exists at the center “c” in the vertical direction. next,
By shaking in the θ2 direction, the image moves between “3-4” in the vertical direction. At this time, since the image does not swing in the θ1 direction, the image is at the center “c” in the horizontal direction.

In addition to the horizontal and vertical directions as described above, by shaking the plate so that the image moves in an oblique direction as shown in FIG. 12, a spatial low-pass filter effect can be provided in the oblique direction.

Also, as shown in FIG. 13, a spatial low-pass filter effect can be provided by shaking the plate so that the image rotates.

In the above description, the method of moving the parallel plane plate is shown as a method of moving the image. However, an element whose refractive index changes is obliquely inserted into the imaging optical system or the viewfinder optical system, and the image is moved by changing the refractive index. You may make it do.

In FIG. 4, the same effect can be obtained by swinging the mirror 5.

FIG. 14 shows still another embodiment. In this example, a part of the imaging optical system, in particular, a part of the focusing lens 1f or part of the finder optical system 6 is moved so that a defocus state can be achieved. In this example, image quality deterioration is confirmed by changing the defocus amount according to the compression ratio and the compression method. It goes without saying that the imaging optical system is brought into a focused state during shooting. As a configuration for driving the optical member, a configuration in which a normal focusing ring is rotated, or a configuration in which the focusing lens 1f is moved to a piezoelectric element 23 which is a different unit from the normal focusing unit as shown in FIG. May be driven.

FIG. 15 is a block diagram of a still camera system according to still another embodiment. In this example, an electronic viewfinder (hereinafter abbreviated as EVF) 60 is used. Then, like a video camera, the signal from the image sensor 3 is processed through the A / D converter 8, the buffer memory 9, the D / A converter 24, and the signal processing circuit 25, and is displayed on the EVF 60. Normally, the EVF does not provide a sufficient number of pixels due to the demand for miniaturization, and therefore cannot be said to have a sufficient resolution. Therefore, even if the moving image state and the shooting screen are displayed on the EVF according to the compression, it is not clear how the image quality changes due to the compression. In view of this, in the EVF, it is common to emphasize a high-frequency component by performing outline enhancement. Therefore, an image is displayed by changing the amount of enhancement according to a compression ratio or a compression method. By looking at this display, the deterioration of the image quality can be confirmed.

FIG. 16 is a block diagram according to still another embodiment.
In this example, an image according to a compression ratio and a compression method can be displayed on an electronic viewfinder (EVF) 60. By enlarging a part of an imaging screen, deterioration of image quality can be confirmed. It was done. The subject image is exposed to the image sensor 3 by pressing the release switch SW1, and the optical signal is converted into an electric signal by the image sensor 3, A / D converted, and stored in the buffer memory 9. This signal is further processed, compressed and stored in the image memory 10.
In the present embodiment, the compressed signal is expanded, D / A converted, signal-processed, and displayed on the EVF 60. Note that a display switch SW3 may be provided and displayed only when necessary, or a compression mode selection switch SW2 may be provided and displayed by operating this switch.

The image displayed on the EVF 60 changes according to the selection of the compression mode selection switch SW2. After viewing the EVF60 image and selecting the compression mode that has reached the imaging purpose,
By pressing SW4, the system controller 12 starts writing a video to a recording medium, that is, the image memory 10. If the recording switch SW4 is not pressed, after a certain time has elapsed after the release operation or the switching operation of the compression mode selection switch SW2, recording may be performed in the selected compression mode, or conversely, cancel. May be performed. The recording switch SW4 is also used as a release button of the release switch SW1, and may be configured to be recorded on a recording medium when the release operation is performed again.

Normally, EVFs do not have enough pixels compared to the video information to be recorded, so by expanding a part of the shooting range and displaying it on the EVF, it is possible to display enough compared to the video information to be recorded By performing display according to the compressed signal, it is possible to clearly confirm the deterioration of the image quality.

Further, a digital or analog signal processing circuit may change the signal processing in accordance with the compression ratio or the compression method to change the characteristics of the electric low-pass filter or reduce the S / N ratio.

As a method for enlarging a part of the photographing range (framing) displayed by the EVF, as shown in FIGS. 17 (a), (b), and (c), a magnification can be made variable (for example, magnification I, II). ,
As shown in FIG. 18, a plurality of enlarged places (for example, A to
E) may be selected, which makes it easy to confirm image quality degradation.

Further, as shown in FIG. 19, a position in the finder where a part of the photographing range, for example, a central portion is enlarged and displayed may be selectable. In this example, the positions A to D can be selected, and the position B is enlarged in the drawing.

[Effects of the Invention] As described above, according to the present invention, it is possible to confirm the degree of image deterioration due to compression before compressing and recording video data. Therefore, is the image deterioration acceptable? You can check if it is. Therefore, it is possible to easily select a compression method and a compression ratio having the highest compression rate within the allowable range, that is, the recording method having the highest recording efficiency.

[Brief description of the drawings]

FIG. 1 is a block diagram of a still video system according to one embodiment of the present invention, FIG. 2 is a diagram for explaining a cosine transform as one method of compression, and FIGS. 3 (a) and 3 (b) are based on a cosine transform. FIG. 4 is a detailed view of an image pickup system of the above-mentioned steal video system, and FIG. 5 is a side view showing an example of an optical member used to confirm deterioration of an image due to compression. FIG. 6, FIG. 6 is a perspective view of a plane-parallel plate as another example of the optical member, FIG. 7 is a diagram showing movement of a light beam when the plate is driven, and FIG. FIG. 9, FIG. 9 is a view showing the above-described driving procedure, FIG. 10 is a view showing another example of image movement, FIG. 11 is a view showing another driving procedure, FIG. 12, and FIG. FIG. 14 is a view showing the movement of an image, FIG. 14 is a detailed view showing another example of the imaging system, and FIG.
The figure is a block diagram showing another embodiment of the still video system, FIG. 16 is a diagram showing another embodiment, and FIG. 17 (a)
(B) and (c) are views showing an electronic viewfinder in which a part of a shooting range can be enlarged and changed, FIG. 18 is a view showing an electronic viewfinder in which an enlargement position can be selected, and FIG. It is a figure which shows the electronic viewfinder which was set. 1 imaging lens, 3 imaging element, 6 finder optical system (display means), 60 electronic viewfinder (display means), 8 A / D converter, 10 image memory (recording) Medium), 11: Digital operation circuit (compression means), 12: System controller, 22: Optical element,
SW2: Compression mode selection switch.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H04N 5/222-5/247 H04N 5/91-5/956

Claims (6)

(57) [Claims] An image recording apparatus having a function of compressing an image signal and recording the image signal on a recording medium, processing the image signal so that an image having substantially the same image quality as an image based on the signal after compression is formed. A video recording apparatus having a video pre-recording confirmation function, comprising: signal processing means for performing the following; and display means for displaying an image based on the video signal processed by the signal processing means. 2. The apparatus according to claim 1, further comprising setting means for setting a compression rate of the video signal, wherein said signal processing means performs processing on the video signal in accordance with the set compression rate. A video recording device having a pre-video recording confirmation function. 3. A video recording apparatus having a function of compressing a video signal and recording it on a recording medium, a signal processing means for re-expanding a signal after the image quality has been degraded by being compressed, and a compressed signal. And a display unit for displaying an image based on the video signal expanded by the signal processing unit before recording the image on a recording medium. 4. A video recording apparatus having a function of compressing a video signal obtained by capturing an image of a subject and recording the video signal on a recording medium, the subject image having an image quality substantially equivalent to a video based on the signal after compression. A video recording device having a pre-recording confirmation function of a video, comprising an optical system for optically generating a video. 5. The optical system according to claim 4, wherein the optical system includes a finder optical system for forming a subject image, and an optical element having a filter function installed in an optical path of the finder optical system. A video recording device having a video pre-recording confirmation function according to item 1. 6. The optical system according to claim 1, wherein said optical system includes an electronic viewfinder optical system for forming a subject image, and an optical element having a filter function installed in an optical path of said viewfinder optical system. Item 5. An image recording apparatus having the function of confirming recording of an image according to Item 4.