JPH05167976A - Electronic still camera - Google Patents

Abstract

(57) [Abstract] [Purpose] To develop an electronic still camera suitable for high-speed continuous shooting by increasing the read speed of the solid-state image sensor, reducing image data, and reducing memory capacity. The purpose is to In an electronic still camera having a solid-state image pickup device 12 for outputting an image signal and recording the image signal as image data on a recording medium 15, an operation means of a normal photographing mode and an operation of a continuous photographing mode are provided. Means for continuous shooting mode.
Operating means for thinning out pixels of the solid-state image sensor 12 at a constant ratio to output a reduced image signal, and the reduced image signal as reduced image data is recorded on the recording medium 15 together with a condition signal for continuous shooting. And a plurality of reduced image data recorded on the recording medium 15 is read, one reduced image data is compared with the reduced image data photographed before and after, The reproduction means is provided for reproducing the enlarged image signal by utilizing the temporal and spatial correlations of.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic still camera having a normal photographing operation function and a continuous photographing operation function, and more particularly to a continuous photographing operation function.

[0002]

2. Description of the Related Art An electronic still camera is a solid-state image sensor such as a CCD that receives the brightness of an object and outputs an image signal, an A / D conversion circuit that digitally converts the image signal output as an analog signal, and a digital image. A signal processing circuit for processing the converted image signal, performing color adjustment, etc., and outputting image data, and an image data output from this signal processing circuit.
A recording medium (magnetic floppy disk, semiconductor memory) for recording data, a controller for controlling each circuit, and the like are included.

In this type of camera, a solid-state image pickup device is driven by a drive circuit, and the electric charge accumulated in each pixel of the solid-state image pickup device is output as a still image signal of one screen, and this image data is recorded on a recording medium. Although it is recorded, about 50 shot images are recorded on the recording medium due to the memory capacity.

Further, the electronic still camera as described above is
Since the solid-state image sensor has an electronic shutter function and the image signal is recorded magnetically and electronically,
It is possible to obtain 10 continuous still images. Therefore, it is extremely convenient for continuous shooting (hereinafter referred to as continuous shooting) of a rapidly changing subject such as a golf swing or an automobile running at high speed.

Such a conventional electronic still camera is convenient for continuous shooting as described above, but
Because the memory capacity of the recording medium is about 50 shot images, the memory capacity is limited, and the reading speed of the solid-state image sensor and the writing speed to the recording medium are limited. However, there is a problem that it is difficult to continuously capture the images.

In order to solve this problem, the correlation of the continuously shot images in the time direction is used to record the differential signal of the image signals, thereby reducing the image data and reducing the memory capacity problem. A solved electronic still camera is proposed by Japanese Patent Application No. 62-194442 (Japanese Patent Laid-Open No. 64-39883).

The electronic still camera of this prior art example records the first image signal photographed in the continuous photographing mode on a recording medium, and the second image signal from the second image signal to the second image signal. Subtract the first image signal and record the difference signal,
Thereafter, similarly, a differential signal is recorded for each continuous shooting.

When reproducing the image data recorded on the recording medium, the first image signal is output as it is, and the second and subsequent image signals are combined with the differential signal to form a reproduced image. It is configured to output.

[0009]

In the case of the above-described electronic still camera of the prior art, the maximum speed of continuous shooting is limited by the read speed of the solid-state image pickup device. In other words, if the same solid-state image sensor as the current video camera is used, it takes 1/30 (seconds) to read an image of one frame.
The number of images per second is the maximum continuous shooting speed of this electronic still camera.

Although the maximum continuous shooting speed can be increased by increasing the read speed of the solid-state image sensor,
Since the D conversion circuit, the signal processing circuit, and the like operate at high speed, there are problems that the circuit configuration becomes complicated and the camera becomes expensive.

In view of the above situation, the present invention aims to develop an electronic still camera capable of high-speed continuous shooting without increasing the reading speed of the solid-state image pickup device, reducing the image data and reducing the memory capacity. To aim.

[0012]

In order to achieve the above object, in the present invention, as a first invention, a solid-state image pickup device for outputting an image signal is provided, and the image signal is recorded on a recording medium as image data. In the electronic still camera, a normal photographing mode operating means and a continuous photographing mode operating means are provided, and the continuous photographing mode operating means thins out the pixels of the solid-state image sensor at a constant ratio to reduce the size. There is proposed an electronic still camera characterized by comprising means for outputting an image signal and means for recording the reduced image signal as reduced image data on a recording medium together with a condition signal for continuous shooting.

As a second invention, in addition to the electronic still camera described above, a plurality of reduced image data recorded on a recording medium are read out, and one reduced image data is photographed before and after. Compared with the reduced image data, a reproduction means for reproducing the enlarged image signal by utilizing the temporal correlation between pixels or the spatial correlation of pixels is provided.

[0014]

In the normal photographing mode, as is well known, all pixels of the solid-state image pickup device are read out and the image signal thereof is recorded in the recording medium. In the case of shooting in the continuous shooting mode, the pixels of the solid-state image sensor are thinned out at a constant rate of 1/2, 1/4, etc., and the thinned-out pixels are output from the solid-state image sensor as a reduced image signal. This reduced image signal is digitized by an A / D conversion circuit and then signal-processed and recorded on a recording medium as image data.

As a result, if the solid-state image pickup device has a normal reading speed, for example, decimating to 1/2 will result in doubling,
When thinning out four, four times as many image data are recorded on the recording medium. That is, more images can be recorded without increasing the operating speed of the entire camera system. The reduced image data is recorded on the recording medium together with the condition signals such as the thinning method, the number of continuous shots, and the recording method.

The reduced image data recorded on the recording medium is
The reproduction means enlarges the image signal to the same level as the image signal for normal photographing. The reproducing means reads a plurality of reduced image data according to the shooting order from the recording medium and reproduces the enlarged image signal by utilizing the temporal and spatial correlation of the plurality of reduced image signals.

[0017]

An embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing the electrical principle configuration of an electronic still camera. In this figure, 11 is a photographing optical system, and 12 is a solid-state image sensor such as a CCD. The solid-state image sensor 12 photoelectrically converts the brightness of the object received through the photographing optical system 11 and outputs an image signal as an analog signal.

This image signal is amplified by the amplifier circuit 13 and then digitally converted by the A / D converter circuit 14,
The digital image signal is recorded as image data in the semiconductor memory card 15 which is a recording medium. It should be noted that the digital image signal is actually subjected to processing such as color adjustment by a signal processing circuit (not shown) and then recorded.

The system control circuit 16 includes a CPU and a RAM.
A circuit for controlling the circuit of the entire camera equipped with a micro computer including the above, so that the release signal from the release signal source 17 output by operating the shutter button is input to start photographing. To work.

Further, the drive circuit 18 includes the solid-state image pickup device 12
It is driven so that it has a shutter function. That is, it works to determine the charge accumulation time of the image pickup device 12.

Further, this electronic still camera is provided with a normal photographing mode operating means and a continuous shooting mode operating means, and a mode switching signal output by operating the mode switching button. By inputting the output signal of the source 19, the system control circuit 16 controls each circuit so as to switch the operation mode.

In the shooting mode switched to the continuous shooting mode, the drive circuit 18 controlled by the system control circuit 16 drives so that the pixels of the solid-state image pickup device 12 are thinned out and read out. That is, when switching to the continuous shooting mode, the mode switching signal source 19 sets the conditions of continuous shooting mode switching, continuous shooting number, continuous shooting time, and continuous shooting speed. By this condition setting, the system control circuit 16 judges the capacity of the unused area of the semiconductor memory card 15, and based on this judgment, decides how to thin out the pixels of the solid-state image pickup device 12, and read out the signal of the solid-state image pickup device 12. To the drive circuit 18 for controlling the.

FIG. 2 is an explanatory view exemplifying how to thin out pixels of the solid-state image pickup device 12. FIG. 2 (A) is an example of thinning out a fifth eye pattern, in which the ◯ mark indicates the nth reading, and the X mark indicates the n + 1th reading.
The second read is shown. By thinning out the pixels in this way and reading them, the image signal is reduced to 1/2.

FIG. 2B shows an example of grid-like thinning-out, in which the mark ○ indicates the nth reading, the mark × indicates the n + 1th reading, the mark Δ indicates the n + 2nd reading, and the mark □ indicates the n + 3th reading. Read out. If the pixels are thinned out and read out in this way, the image signal is reduced to 1/4.

In the electronic still camera constructed as described above, an image signal is recorded by a known operation in the normal photographing mode. That is, the system control circuit 16 operates so as to start photographing by the release signal output from the release signal source 17 by operating the shutter button. As a result, the solid-state image sensor 12 is driven by the drive circuit 18,
The brightness of the subject is received according to the shutter time and converted into an electric signal.

Then, all the pixels arranged in a matrix on the solid-state image pickup device 12 are read out and output as image signals. As described above, this image signal is amplified, converted into a digital signal and recorded in the semiconductor memory card 15.

When the mode is switched to the continuous shooting mode, the solid-state image pickup device 12 is read out according to the thinning-out method of the pixels determined by the setting conditions and the memory capacity by starting the photographing as described above. That is, FIG.
The solid-state image sensor 12 is read according to the pixel thinning method illustrated in (A) and (B), and the pixel thinning image signal (hereinafter, referred to as a reduced image signal) is output.
The reduced image signal is amplified and then digitally converted and recorded in the semiconductor memory card 15 as reduced image data.

When continuous shooting is performed in this manner, the operation speed of the entire camera system is not increased, and the pixel thinning in FIG. 2 (A) is doubled, and the pixel thinning in FIG. 2 (B) is four times. Image signals can be recorded, and an extremely large number of image signals will be recorded in the semiconductor memory card 15.

In the continuous shooting performed as described above, the condition signal relating to the continuous shooting is added from the system control circuit 16 to the reduced image signal as header information through the memory controller and recorded. This header information is used to create at least information necessary for image reproduction of a reduced image signal, that is, an image signal (hereinafter referred to as an enlarged image signal) in which an image signal of pixel thinning is interpolated and returned to a normal size. Is the information necessary for.

For example, the header information added here is as follows. 1. Index indicating the shooting order of the continuously shot images 1. Location on the memory address where each reduced image data is recorded. 3. Reduction ratio of reduced images and thinning method of pixels 4. The number of continuous shots An example of the recording format of the reduced image signal in the semiconductor memory card 15 is shown in FIG.

The reduced image signal recorded in the semiconductor memory card 15 by continuous shooting is enlarged (reproduced) to the same size as the image signal recorded in the normal photographing mode and output, and an output device such as a monitor. It can be displayed by.

Next, the reproducing means for expanding the reduced image signal in this way will be described. The enlarged image signal (reproduced image signal) is generated by interpolating the thinned pixels of the reduced image signal recorded in the semiconductor memory card 15, but the reduced image signal has a longer sampling interval during recording. This is equivalent to the above, and since the high frequency components of the image signal are missing, the resolution of the enlarged image signal thus generated is lower than that of a normal image.

In order to solve this problem, this reproducing means utilizes the fact that the correlation of pixels in the time direction is large, and interpolates the thinned pixels using a plurality of reduced image signals to enlarge the enlarged image signals. To generate.

For example, the nth and n + 1th images of the reduced image signal thinned out in FIG. 2A are respectively Gn and Gn +.
1 and Gn is imaged at time t, and the difference between the image capturing times of Gn and Gn + 1 is Δt, as shown in FIG. 4A, the pixel at the point (x, y) of Gn is Gn ( x, y, t). In addition, the ◯ mark in FIG. 4A indicates a pixel read in the n-th continuous shooting.

Assuming that the sampling intervals in the x direction and the y direction are Δx and Δy, respectively, the points (x + Δ) thinned out in the nth sheet.
The pixel of (x, y) can be expressed as Hn (x + Δx, y, t) as shown in FIG.

When the temporal correlation between the continuously shot images is high, an approximate expression such as Hn (x + Δx, y, t) ≈Gn + 1 (x + Δx, y, t + Δt) is established. Therefore, it is possible to perform interpolation using images with different shooting times. (See FIG. 4 (B), ×
The mark indicates the pixel read in the continuous shooting of the (n + 1) th sheet)

However, if there is no temporal correlation between the images, the above-described approximate expression does not hold, and at this time, interpolation is performed using the spatial correlation of the images. That is, Hn
Using the Gn pixels near (x + Δx, y, t),

[Equation 1] By interpolating an interpolation filter that satisfies the equation (3), the thinned pixels Hn (x + Δx, y, t) can be interpolated. Ai, j in the above equation is a coefficient of the interpolation filter.

As described above, a plurality of reduced image signals are used and interpolated by the temporal correlation or the spatial correlation of these images, so that the reduction of the resolution of the image is suppressed and the reduced image signal is reduced. Can be reproduced as an enlarged image signal.

FIG. 5 is a block diagram showing the electric circuit of the reproducing means for reproducing the reduced image signal according to the above theory. When the reduced image signal to be displayed is determined, the information necessary for generating the enlarged image in the header information regarding this reduced image signal is read from the semiconductor memory card 15 and sent to the system control circuit 25. For example, when enlarging the reduced image signal In, the header information Pn thereof is sent to the system control circuit 25, and from the index n of the reduced image signal of this header information Pn and the thinning method of the pixel, another reduction used for interpolation. The image signal index and interpolation method are determined.

Here, among the reduced image signals recorded in the semiconductor memory card 15, the 1/2 thinned-out signal of FIG. 2A is reproduced, and In and In + 1 are used for interpolation. .. Pixels Hn (xo, thinned out by In,
When interpolating yo), first the correlation in the time direction is examined. Therefore, the points (xo, In, In + 2)
The pixels in the neighborhood region R of (yo) are taken out and input to the correlation detection circuit 21 of the interpolation circuit 26.

In the correlation detection circuit 21,

[Equation 2]

[Equation 3] Is calculated and Ma and Mb are compared with a predetermined threshold value Mth.

When Ma and Mb are larger than Mth, it is assumed that the spatial correlation is high, and the control signal for operating the spatial interpolation circuit 22 for performing the interpolation by utilizing the spatial correlation is output. When Ma and Mb are smaller than Mth, it is determined that the temporal correlation is high, and a control signal for operating the time interpolation circuit 23 that performs interpolation using the temporal correlation is output.

When the time interpolation circuit 23 operates, Ma <M
The value of In−1 (xo, yo) when b, and the value of In + 1 (xo, yo) when Ma> Mb are output to the output buffer 24 as the interpolation pixel of Hn (xo, yo).

When the spatial interpolation circuit 22 operates, the image signal of the area S near the point (xo, yo) of the reduced image signal In is input to the spatial interpolation circuit 22 and the predetermined filter coefficient is applied to these image signals. Using Ai, j,

[Equation 4] The interpolated pixel is obtained by performing the filter processing according to the equation (4) and is output to the output buffer 24.

The output buffer 24 has a recording capacity capable of recording one or more enlarged image signals, and generates an enlarged image signal by adding the interpolated pixel signal and the reduced image signal output from the interpolation circuit. Then, the generated enlarged image signal is sent to an image display device through a D / A conversion circuit or the like for image display. As described above, the reduced image signal in which the pixels are thinned and recorded can be reproduced as an enlarged image while suppressing a decrease in resolution.

Although one embodiment of the present invention has been described above, a so-called multi-screen display in which a plurality of reduced image signals recorded in the semiconductor memory card 15 can be simultaneously output to the display device as they are is also possible. it can. Moreover, the memory capacity recorded in the semiconductor memory card 15 can be further reduced by subjecting the reduced image signal to signal compression processing such as time-direction and space-direction differential encoding and orthogonal transform encoding. In this case, an encoder is provided at the front stage of the semiconductor memory card 15 and a decryptor is provided at the rear stage thereof. Although the semiconductor memory card 15 is used as the recording medium in the above embodiment, the magnetic floppy disk is used.
A disk may be used as well.

[0047]

As described above, according to the present invention, the pixels of the solid-state image pickup device are thinned out and read out, and the image signal is
Since a continuous shooting mode operation means for performing D / D conversion and recording on a recording medium is provided, it is possible to record a large number of continuous shots in memory using a conventional recording medium, and to increase the recording capacity of continuous shooting. It becomes a fully equipped electronic still camera.

Further, the image signal in which the pixels are thinned out is interpolated by using a plurality of image signals according to the temporal correlation or the spatial correlation and is reproduced as a normal image signal. It is possible to suppress a decrease in resolution as much as possible during display.

[Brief description of drawings]

FIG. 1 is a block diagram showing an electrical principle configuration of an electronic still camera according to an embodiment of the present invention.

FIG. 2 is a diagram exemplifying how to thin out pixels of a solid-state imaging device, and FIG. 2 (A) shows thinning in a five-eye pattern.
(B) shows thinning in a grid pattern.

FIG. 3 is a diagram showing a recording mode of a reduced image signal in which pixels are thinned out in a semiconductor memory card.

FIG. 4 is a diagram for explaining an interpolation using a temporal correlation and a spatial correlation of a reduced image signal.

FIG. 5 is a block diagram showing a circuit example of a reproduction means of a reduced image signal.

[Explanation of symbols]

 11 Photographing Optical System 12 Solid-State Image Sensor 13 Amplifying Circuit 14 A / D Conversion Circuit 15 Semiconductor Memory Card 16 System Control Circuit 17 Release Signal Source 18 Drive Circuit 19 Mode Switching Signal Source 21 Correlation Detection Circuit 22 Spatial Interpolation Circuit 23 time interpolation circuit 24 output buffer 25 system control circuit 26 interpolation circuit

Claims (2)

[Claims] 1. An electronic still camera having a solid-state image pickup device for outputting an image signal, wherein the image signal is recorded as image data on a recording medium, in a normal photographing mode operating means and in a continuous photographing mode. Means for outputting the reduced image signal by thinning out the pixels of the solid-state image pickup device at a fixed ratio, and the means for operating the continuous photographing mode, and the reduced image signal as reduced image data for continuous photographing. An electronic still camera, comprising: means for recording on a recording medium together with a condition signal. 2. A plurality of reduced image data recorded on a recording medium are read out, one reduced image data is compared with the reduced image data photographed before and after, and the time between pixels is temporally changed. The electronic still camera according to claim 1, further comprising a reproducing means for reproducing the enlarged image signal by utilizing the correlation or the spatial correlation of pixels.