JPS63122392A - Electronic still camera - Google Patents

Abstract

PURPOSE:To attain a high picture quality, high reliability and to reduce the deterioration in the picture quality at the time of editing and duplicating by constituting the titled camera of the image pickup part of high picture quality having little generation of a false signal and a recording part for recording a picture signal obtained by compressing information by a highly efficient picture encoder in a compact memory pack as a digital signal. CONSTITUTION:The picture signal read from the image pickup element 4 having little generation of the false signal at the time of compressing the information by using the correlation of respective picture elements and capable of outputting a good picture quality is coverted into the digital signal by an A/D converter and written in a buffer memory 8. At an arbitrary time after the writing of the signals of all screens is completed, this signal is read to the picture encoder 7, the quantity of the information is compressed and recorded in the memory pack 11. The picture encoder 7 can use a system or the like for using the correlation of the signals between the adjacent picture elements and as the correlation between the picture elements is stronger, it is difficult to generate the deterioration in the picture quality due to the compression of the information.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to an electronic still camera that captures and records still images.

2. Description of the Related Art In place of conventional optical cameras, electronic still cameras are being developed that use an image sensor to convert a subject image into an electrical image signal and record this image signal on a storage medium. A first example of this conventional configuration is shown in FIG. 6, and a color filter arrangement of the solid-state image sensor 103 used in the same figure is shown in FIG.

In FIG. 5, a subject image (not shown) is a lens 101.
, the image sensor 10 is displayed only at a certain moment through the shutter 102.
3 and converted into a charge image.

This charge is then read out by the image sensor drive circuit 116 in synchronization with a synchronization signal generated by the synchronization signal generator 116. Since this charge image is read out by interlaced scanning in accordance with the television system, in the first vertical scanning (odd field), as shown by the solid line arrow in Fig. 6...・(N-2)
Every other line is read out in the order of the 1st line, the Nth line, and the (N+2)th line, and in the second vertical scan (even field), the data is read out in the first vertical scan as shown by the dotted arrow in Figure 6. Remaining......(N-1)th line, (N+1)
The charge images are read every other row in the same order as the row 1 and the (N+3) row, completing the reading of the charge image of the entire screen.

The electric signal read out in this way is amplified by an amplifier 104, and then guided to a low-pass filter (LPF) 105 and a bandpass filter (BPF) 106, where it is divided into a luminance component, which is a low frequency component, and a high frequency component. It is separated into a color signal component which is a modulation component. For example, during the first vertical scan, the output signal components of the LPF 105 are (G+B) and (R+G) components, respectively, in accordance with the (N-2)th, Nth, and (N+2)th rows.

Since the (G+B) component and the negative-like image are captured in the vertical direction, the (R+G) component and the (B+G) component become different signals for each horizontal scanning period, so the first one-horizontal period delay circuit 1
07 and an adder 109 average the signals of two horizontal scanning periods, and a signal of the (R+2G+B) component is constantly outputted as a luminance (Y) signal. In addition, the component detected by the detection circuit 108 of the output of the BPF 106 is detected every horizontal scanning period (B
-G) cannot be obtained, the second one horizontal scanning period delay circuit 110 and the first one which alternately switches the two input terminals every -horizontal scanning period. Second changeover switch 111.112
By using the signal one horizontal scanning period ago, (R-
G) signal and (B-G) signal are obtained simultaneously. The Y signal, (R-G) signal, and (B-G) signal are converted into signals suitable for recording by the recording signal processing circuit 113, and then sent to the electronic still camera main body 119 (encircled by a dotted line in the figure). (parts) and is recorded on the removable recording medium 120, and the -th still image is completed. The above signal relationship is exactly the same during the second vertical scan because the color filter array in Figure 6 is exactly the same in the rows scanned during the first and second vertical scan periods. It is clear from Further, the above series of operations is controlled by the system control circuit 117, and the shirt,
J-102 and the recording medium 120 are each connected to a shutter drive circuit 114. Driven by a drive circuit 118.

Next, a second conventional example will be explained.

FIGS. 7 and 8 are diagrams respectively showing examples of conventional configurations of electronic still cameras having other types of imaging units and the arrangement of color filters of the solid-state imaging device 121 used therein. The scanning method and order are the same as the example in Figure 6 and Figure 6, using the interlaced scanning method, and as shown by the solid line and dotted line arrows in Figure 8, charges are applied every other line in the first vertical scan (odd field). is read out, and the rows left after the second@th (even field) vertical scan are similarly read out every other row. Therefore 1
The signal obtained by horizontal scanning is first
The output signal Y of No. 5 is T(C
y+Mg+Ye+G) and -5(Cy1G+Ye+M(
J), and the same signal of R+B1iG is obtained, which is taken as a luminance signal. On the other hand, the output of the detection circuit 108 has H((Cy+Mq)-(Ye+G))=,
(B − G/2 ) signal and 2 ((Cy+G) −
("10Mq) ) =-(R-G/2) signal is obtained (because cy-B+G, Mg-R+B, Y+e-R
+G).

Therefore, the two types of color difference signals obtained during this -horizontal scanning period are transferred to the -horizontal scanning period delay circuit 1109 first . Second
Synchronization processing is performed by the changeover switches 111 and 112, and Y, RG/2, and BG/2 signals are obtained.

And the above-mentioned Y signal as in the first conventional example.

The (R-G/2) signal and (B-G/2) signal are converted into signals suitable for recording by the recording signal processing circuit 113, and are converted into signals suitable for recording by the electronic still camera body 119 (the parts surrounded by dotted lines in the figure). )
is recorded on the removable recording medium 120, and -th still image is completed. Note that the above signal relationship is exactly the same in the second @th vertical scan as in the first conventional example.
This is clear from the fact that the color filter arrangement in the figure is exactly the same in the rows scanned during the first and second vertical scanning periods.

Further, the series of operations described above is controlled by the system controller A-stage circuit 117, and the shutter 102 and the recording medium 120 are driven by the shutter drive circuit 114 and the drive circuit 118, respectively, by control signals from this circuit. This is the same as the first conventional example.

Problems to be Solved by the Invention However, the conventional example of the above configuration has the following problems in terms of image quality of the imaging section.

In other words, in the conventional example described above, both the luminance signal and the color signal are obtained by using the correlation in one horizontal scanning period, so the image changes in the vertical direction and the correlation between the signals is obtained in one period. There is a fundamental problem in that a false signal occurs when there is no such signal, and furthermore, in the above example, the temporal correlation of one horizontal scanning period is used, but the signal is read out by interlaced scanning of the television method. Since the correlation between two rows every other row is used instead of the correlation between two spatially adjacent rows, there is a high probability that the correlation will disappear and a false signal will occur, and the false signal will be large. As a result, satisfactory image quality cannot be obtained.

Furthermore, the recording medium of the above-mentioned conventional electronic still camera and the recording method for which recording signal processing is the main component involve performing analog signal processing on the analog electric signal output from the image sensor. There are two types of examples: one in which the data is recorded magnetically on a magnetic disk, etc., and the other in which the analog video signal from the image sensor is A-D converted and the digital signal obtained is directly recorded in pre-tal memory. However, these two recording methods also have the following problems.

First of all, in the former example, because the video signal is subjected to analog processing and magnetic recording is performed, signal deterioration is likely to occur. The disadvantage is that the image quality deteriorates significantly when recorded, and one of the advantages of electronic still cameras, which is that they are easy to edit and replace images, cannot actually be utilized. Furthermore, in order to perform magnetic recording, relative movement between the magnetic head and the magnetic recording medium is required, which inevitably requires mechanical moving parts, which also has the disadvantage of lacking reliability.

Next, in the latter example, since the analog video signal from the image sensor is A-D converted and recorded directly in the digital memory, there is a drawback that the digital memory has a large capacity. Halftone image signals such as television signals used by electronic still cameras contain a huge amount of information.For example, NTS, which is currently in use in Japan,
If you try to convert G-TV video signals directly into digital memory and record them directly into digital memory, approximately 3 Mbit of storage capacity will be required to store one screen (one frame).
It has become impossible to configure a memory unit of a practical size and price, and therefore, a practical electronic still camera with such a configuration will not be possible in the near future. The purpose of the present invention is to provide an electronic still camera with high image quality, high reliability, and less deterioration in image quality during editing and duplication.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a color image sensor that photoelectrically converts an image for one frame, and a one-frame image sensor that temporarily stores image signals read out from the color image sensor. The camera is equipped with a buffer memory for 10 minutes, and a high-efficiency image encoder that compresses the image information in the buffer memory, and converts the image signal information compressed by the high-efficiency image encoder into a digital signal to the camera body. It is an electronic still camera that stores data in a removable memory bag.

Effect of the Invention According to the above-described configuration, the present invention firstly arranges the color filters of the image sensor in such a manner that each color is arranged at least every other pixel in both the horizontal and vertical directions, or in horizontal rows with the same pigment arrangement in the horizontal direction. are arranged every other row in the vertical direction, and when information is compressed using the correlation between each pixel, there is less generation of false signals, and good image quality can be output. 1. The digital recording method has no moving parts, so it is highly reliable and does not cause image quality deterioration.1. Overall, it is possible to provide an electronic still camera that is highly reliable and has good image quality.

Embodiment FIG. 1 shows the basic configuration of an embodiment of the present invention. In the figure, the subject image (not shown) is the lens 2. The light is guided through the shutter 3 to the image sensor 4 for a certain moment and converted into a charge image.

This charge image is then read out pixel by pixel as an analog signal by the image sensor driving circuit 8. This analog image signal for each pixel is converted into a digital signal by an A/D converter and written into the back 7 memory θ. Then, at an arbitrary time after the writing of the signal for the entire screen is completed, this signal is read out by the image encoder 7, the amount of information is compressed, and the signal is recorded in the memory back 11. This memory pack 1
The writing of image signals to the camera body 1 is controlled by a drive circuit 1o, and the series of sequences described above is further controlled by a system control circuit 9 within the camera body 1. The part surrounded by a dotted line in the figure shows the camera body 1, and the memory pack 11 is configured to be detachable from the camera body 1 through a connector or the like. The image encoder 7 described above utilizes the correlation between signals between adjacent pixels (but, in the case of an image sensor with a color filter placed in front, between pixels of the same color) to encode the amount of information. It is possible to use a method to compress the image, and image quality deterioration due to compression of seed information with strong correlation between pixels is less likely to occur.

The memory pack 11 also includes a connector section 12, for example, as shown in FIG. Even when the I10 circuit section 13 for interfacing with the camera body or playback device, the memory section 14 equipped with a plurality of semiconductor memories, and the memory pack 11 are removed from the camera body or playback device, recorded data can be saved. Backup battery section 16 for holding
An example of this is a magnetic card with a size of about 85 rrs x 55
It is possible to use something like a memory card with a size of about 100 ms. Also, as a semiconductor memory, 0MO8-RAM
For example, 16Mbit 0M in 1 chip.
If an O8-RAMIC is realized, it will be possible to mount about four IC chips on this memory card, so the storage capacity of one memory card will be 64 Mbit. Then, if the information content of the original image signal (approximately 3 Mbit of information) is compressed to % using an image encoder, 64 still images can be recorded on one memory card.
A practically sufficient electronic still camera can be constructed.

As a color filter for the image sensor used in the electronic still camera having the above-mentioned configuration, the color arrangement shown in FIGS. 3 and 4 has a strong signal correlation between pixels.
This method is suitable because there is little deterioration in image quality when information is compressed by an image encoder, and a high-quality electronic still camera can be obtained.

In other words, by writing the signals of each pixel of the image sensor independently into the buffer memory and reading out and using the signals as in the configuration described above, this signal reading can be performed non-destructively. Since the signal of a single pixel can be used any number of times, unlike conventional color filters, the color arrangement is not restricted by the scanning method of the image sensor, and the spatial sampling gap for each color is minimized. This is because such an arrangement becomes possible.

For example, the color filter shown in FIG.
(red), G (green), and B (blue), but G, which is included in a large proportion of the luminance signal, is arranged every other pixel horizontally, and the R and B signals are arranged vertically, Since the pixels are arranged every other pixel in both the horizontal direction, the number of pixels arranged for each color is the same compared to the conventional example shown in FIG. 6, but the uniformity of the distribution is excellent. Therefore, false signals are reduced when image information is compressed using the correlation between each pixel, and image quality is improved. This can be explained by using the color filter shown in FIG.
...(N-2) row, (N-1) row.

......(N+2) rows, (N+s) rows...
. . . and each horizontal row is read out using a sequential scanning method that sequentially scans each horizontal row according to the order of their spatial arrangement, and after accumulating this signal in a buffer memory, it is read out non-destructively in the following order: This will be demonstrated by comparing the image obtained when an interlaced frame image conforming to the standard television system is obtained with a conventional example.

To read signals from the buffer memory, first, in the first field, during the (n-'t+)H horizontal scanning period, the (N-2) and (N-2) rows in the color filter array in FIG.
-1) Signals corresponding to rows are read simultaneously and independently.

The signals of the two rows are first added together and then processed by the luminance signal processing circuit, resulting in a luminance signal (-R+2
0+B) is obtained. On the other hand, one of the two rows of signals is sent to the second color signal processing circuit, and the remaining signal is sent to the first color signal processing circuit.
The processing is performed in the color signal processing circuit of R-G, respectively.
signal, BG signal. Similarly, during the nH horizontal scanning period, the signals corresponding to the N rows and (N+1) rows are
1) During the H horizontal scanning period, signals corresponding to the (N+2) and (N+3) rows are simultaneously read out from the pack memory 6 and similar processing is performed. Next, in the second field, during the (n-1)'H horizontal scanning period,
Signals corresponding to N rows and (N-1) rows are read out independently and simultaneously, and during the n'H horizontal scanning period, (N+2)
) and (N+1) rows are (n-)-1)
'H horizontal scanning period, (N+4) rows and (N+3)
The signals corresponding to the rows are read out simultaneously and independently, and signal processing is performed in the same manner as in the first field to output a luminance signal, an RG signal, and a BG signal.

Note that among the signal readouts described above, at least the first field readout is performed non-destructively, and the second field readout is performed non-destructively.
It is necessary to read out the same signal in the second field in a pair of two lines shifted by one line from the first field. When reading the second field, either destructive reading or non-destructive reading may be used.

The signals output as described above will now be considered. First, the signal relationship between the first and second fields is such that the pairs of two adjacent rows that are correlated are vertically shifted by one row in each field, which means that the center of scanning is shifted. Therefore, there is an interlace relationship, and an image with good vertical resolution can be obtained. Also, since the two horizontal rows that are correlated are always the spatially closest adjacent rows, the correlation is better than the conventional example where the two horizontal rows are spaced one row apart.
The probability of a false signal occurring is small compared to the correlation between two rows, and the false signal that occurs with a small probability has a small vertical spread and is conspicuous<<
, resulting in a hump that provides good image quality.

Alternatively, if the high frequency components of the vertical spatial frequency components of the optical image incident on the image sensor are removed by a spatial low-pass F-wave filter so that there is always a correlation between two adjacent rows, This false signal can be completely removed, and the spatial frequency component to be removed for this purpose only needs to be a frequency component higher than the frequency corresponding to one pitch of vertical pixel repetition. The resolution degradation is also small, and this method is also sufficient for practical use. As such a spatial low-frequency F-wave device, one that utilizes the birefringence of a crystal such as quartz is well known. A quartz crystal plate having the desired thickness may be placed in front of the image sensor.

As explained above, compared to the corresponding conventional filter shown in FIG. 6, the color filter shown in FIG.
It is clear that this method can output signals with fewer false signals, and as a color filter, theoretically generates fewer false signals, and that there is a strong correlation between each pixel for all colors.

Next, a similar explanation will be given for the WJ4 diagram. First, regarding the undulations of the color filters, there is no difference in the horizontal direction between the conventional example shown in FIG. 8 and the arrangement of the present invention shown in FIG. 4, but in the vertical direction, the former has two horizontal rows as a set. There are two sets in which a specific color exists and a set in which it does not exist, and there is density in the vertical direction, whereas in the latter arrangement of the present invention, a specific color filter exists at every other pixel in the vertical direction. However, the uniformity of the distribution is reduced, and the signal required to obtain the standard TV system signal is obtained by using the correlation between each pixel, and false signals are generated when image information is compressed. It is expected that the image quality will improve as the image quality decreases.

As in the case of Fig. 3, the signal is read out from the image sensor by sequential scanning, and after accumulating this signal in the buffer memory, it is read out non-destructively in the order shown below, and the resulting standard television format is The matching interlaced frame images will be compared with the conventional example.

To read signals from the buffer 7 memory, first in the first field, during the (n-1)H horizontal scanning period, the signals are read from the (N-2) row and (N-2) row in the color filter array in FIG.
1) Signals corresponding to rows are read simultaneously and independently.

Then, the signal corresponding to the (N-2) row is processed by the luminance signal processing circuit, and the luminance signal (=R+B+s/
2G). The signals corresponding to the (N-2) rows are processed by the second color signal processing circuit, while the signals corresponding to the (N-1) rows are processed by the first signal processing circuit. -G/2) and (BG/2) signals. Similarly, during the nH horizontal scanning period, the Nth row, (N+
1) During the (n+1)H horizontal scanning period, the signals corresponding to the (N+2)th and (N+3)th rows are simultaneously and independently read out, and the signals corresponding to the (n+1)H horizontal scanning are read out simultaneously and independently. A signal similar to period is obtained.

Next, in the second field, during the (n-1)'H horizontal scanning period, the signals corresponding to the (N-1)th and Nth rows are read independently and simultaneously, and 1) The signal corresponding to the row is processed by the luminance signal processing circuit (R+B
+3/2G), and the signal corresponding to the (N-1)th row and the signal corresponding to the Nth row are respectively processed by separate color signal processing circuits to produce (B-G/2G). )
, (RG/2) signal. (N'H horizontal scanning period and (n+1)'H horizontal scanning period, respectively)
+1) line.

The signal corresponding to the (N+2)th line and the signal corresponding to the (N+3)th line, (
Corresponding to the N+4)th line is read out and becomes (n-1)'H
A signal similar to that during the horizontal scanning period is obtained.

Note that whether the above signal reading is destructive or non-destructive is the same as in the case of FIG.

The signals output in this way will be explained. First, regarding the luminance signal, the signals of the first field and the second field are vertically shifted by one line, are completely different signals, and have a perfect interlaced relationship.

In addition, regarding the color signal, the two adjacent horizontal bars that are correlated in the first and second fields are shifted by one line in the vertical direction, which means that the center of scanning is shifted in each field. Therefore, this also has an interlace relationship, and an image with good vertical resolution can be obtained. In addition, the two horizontal lines that are correlated in color signals are always the spatially closest adjacent lines, so the correlation is strong and the probability of false signals occurring is small, and the false signals that occur with a small probability are also As in the case of FIG. 3, the vertical spread is small and unnoticeable, and good image quality can be obtained. Also,
As in the case of FIG. 3, by installing a spatial low-frequency F wave filter, this false signal can be removed with a slight deterioration of vertical resolution.

As explained above, the color filter shown in FIG. 4 can output signals with fewer false signals than the corresponding conventional filter shown in FIG. It is clear that this method generates fewer false signals and has strong correlation between each pixel for all colors.

Note that the present invention is not limited to the color filter arrays of the embodiments described above, and it is clear that various color filter arrays are possible.

Effects of the Invention As described above, according to the present invention, an image signal compressed by a high-quality image pickup unit with less generation of false signals and a high-efficiency image encoder is converted into a digital signal, and a compact memory back An electronic still camera is constituted by a recording section for recording information, and it is possible to realize an electronic still camera that has high image quality, high reliability, and has little deterioration in image quality when editing or duplicating.

[Brief explanation of the drawing]

Fig. 1 is a basic configuration diagram of an embodiment of an electronic still camera of the present invention, Fig. 2 is an explanatory diagram of an example of the configuration of a memory back used in the embodiment, and Figs. 3 and 4 are the same embodiment. is the first color filter array of the solid-state image sensor used in the same example. Second
FIG. 6 is a configuration diagram of the first conventional example, FIG. 6 is a color filter arrangement diagram of the solid-state image sensor used in the conventional example, and FIG. 7 is a diagram of the second conventional example. The configuration diagram and FIG. 8 are color filter arrangement diagrams of the solid-state image sensor used in the conventional example. 2...Lens, 3...Shutter, 4
...imaging device, 5...A/D converter, 6...buffer memory, 7...high efficiency image encoder, 8... ...Image sensor drive circuit,
9...System control circuit, 10...Drive circuit, 11...Memory back. Name of agent: Patent attorney Toshio Nakao and 1 other list 2
Figure 3 Scanning order Figure 4 Scanning cycle Cy: B++19 Ye:p+(i M): Shaku+B 'H → 71H --, n'H → (7t+ 1) H --->(n+1)'H Fig. 8 Cy: 80 Q Ye: R + Hill M Cy: R mid-day scanning tilt

Claims (2)

[Claims] (1) A color image sensor that photoelectrically converts an image for one frame, a buffer memory for one frame that temporarily stores the image signal read out from this color image sensor, and a computer that calculates the image information in this buffer memory. a high-efficiency image encoder that performs information compression, and converts the image signal information-compressed by the high-efficiency image encoder into a digital signal;
An electronic still camera that stores data in a memory pack that is detachable from the camera body. (2) An electronic still according to claim 1, wherein the color filter of the image sensor is arranged such that horizontal rows having the same horizontal dye arrangement are arranged every other row in the vertical direction. camera.