JPH09322181A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate deterioration in the image quality due to an error between amplification factors of two amplifier circuits amplifying two outputs from full picture element read charge coupled devices(CCD). SOLUTION: Odd and even order number scanning signals obtained simultaneously at two output terminals of full picture element read CCDs 2 are amplified by amplifier circuits 5, 6 and processed by a process circuit 42, from which Y, R-Y, and B-Y signals are obtained, An Exposure detection circuit 44 detects the exposure state based on each signal and an MPU 43 decides the amplification factor of the amplifier circuits 5, 6 depending on the detected exposure and the decided amplification factor is corrected by using error data resulting from the amplification factor of the amplifier circuits 5, 6 stored in a memory 45 and the corrected amplification factor is given to the amplifier circuits 5, 6.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus suitable for use in a video camera or the like provided with a progressive scanning solid-state image pickup element in which color filters are arranged in a so-called Bayer array.

[0002]

2. Description of the Related Art In recent years, with the progress of semiconductor technology, a solid-state image pickup device (all-pixel reading solid-state image pickup device, hereinafter all-pixel image pickup device) capable of reading out signals by progressive scanning has been developed. These image pickup devices have less blurring even for a moving subject and can capture a high-resolution image as compared with a conventional interlaced scan (interlaced scan) image pickup device.

That is, in the interlaced image sensor, 1
The frame image is 2 with a time difference of 1 field period.
Since it is composed of one field, when a moving subject is imaged, jaggedness occurs due to the time difference between fields. If the image of one field is taken out without jaggedness, the vertical resolution will be halved. On the other hand, in the all-pixel image sensor,
Since all the scanning lines for the frame can be imaged, the above-mentioned problem does not occur. Utilizing such characteristics, the all-pixel image pickup device is expected to be applied to still image capturing cameras, computer input cameras, and the like.

As a signal processing circuit of a single-chip all-pixel image pickup device, for example, a configuration as shown in FIG. 9 can be considered. FIG.
In, the incident light from the subject is imaged by the imaging optical system 101 on the CCD 102 which is an all-pixel image sensor,
It is converted into an electric signal by the CCD 102. CCD10
A color filter array for color imaging is attached on the surface 2. The color filter array is, for example, an R, B, G Bayer array as shown in FIG. The converted electric signal is transferred to a vertical register and a horizontal register in accordance with a timing signal from a timing generation circuit (not shown), and signals for two scanning lines are output in parallel from two output terminals of the CCD 102. That is, the odd-numbered scanning line signal is output from one of the two output terminals of the CCD 102, and at the same time, the even-numbered scanning line signal is output from the other. By adopting such an output method, it is possible to output the signal of the sequential scanning at the same reading speed as the CCD of the interlaced scanning.

The respective signals are the noise reduction circuit 103,
After being processed by 104 and the amplification circuits 105 and 106, they are converted into digital signals by the AD conversion circuits 107 and 108 and input to the camera process circuit 130 from the input terminals 128 and 129. The input digital signal is 1
The H memories 109 and 110 perform time-axis conversion into line-sequential signals. The read clock of the 1H memories 109 and 110 is twice as fast as the write clock. The timing in this operation is shown in FIG. After that, the selector 133 and the 1H memories 111 and 112 further increase the
The signals for the lines are synchronized and each is separated by the color separation circuit 1.
13 and the contour emphasis circuit 117.

The GBR primary color signal demodulated by the color separation circuit 113 is limited to a required band by low-pass filters 114, 115 and 116, and interference components such as moire are removed. After the band-limited GBR signals are adjusted in level by the white balance circuit 118, the G signals are added by the adder 119 to the contour signal extracted by the contour emphasis circuit 117. High-pass filter 12
The high-frequency component of the contour-corrected G signal is taken out by 0, and added to the RB signal by the adders 121 and 122. After that, the γ correction circuits 123, 124 and 125
After being corrected, the matrix circuit 126 converts the luminance signal Y into the color difference signals RY and BY.

Further, when standard video output is required for monitor output and the like, the luminance signal Y and the color difference signals RY and B- are used.
Y is input to the scan conversion circuit 127. The scan conversion circuit 127 is configured, for example, as shown in FIG. 11, and operates at the timing shown in FIG. In FIG. 11, the Y input is input to the selector 204 via the 1H memory 202, and R
The -Y input and the BY input are switched by the selector 201 and then switched to the Y input by the selector 204 via the 1H memory 203, thereby converting the sequential scanning signal into the interlaced scanning signal.

Further, in FIG. 9, the exposure information detected by the exposure detection circuit 131 from the Y signal is taken into the MPU 132, and the imaging optical system 10 is adjusted so that the exposure has an appropriate value.
The aperture value of 1 and the amplification factors of the amplification circuits 105 and 106 are MP.
It is controlled by U131.

Next, the configuration of the color separation circuit 113 is shown in FIG.
FIG. 14 shows the operation. Among the signals for the three scanning lines input to the color separation circuit 113, the undelayed signal (the signal from the selector 133 in FIG. 1) is shown in FIG.
A signal (a signal from the 1H memory 111) delayed by a horizontal scanning period (hereinafter, 1H) is shown in FIG. 7B, and a signal delayed by 2H (a signal from the 1H memory 112) is shown in FIG.

Of these three signals, the signal shown in (a) and the signal shown in (c) are added by an adder 140 to generate a signal interpolated in the vertical direction. This signal is shown in FIG.
It shows in (d). When the signal of (d) and the 1H delay signal (b) are alternately selected for each dot by the selector 141, a G signal is obtained. The selection signal of the selector 141 is shown in FIG. 14 (e), and the output signal of the selector 141 is shown in FIG. 14 (f). Further, the output of the adder 140 and the signal through the flip-flop 142 are sent to the selector 144. Further, the signal of (b) and the signal through the D flip-flop 143 are sent to the selector 145. Then, the R signal is obtained by selecting the outputs of the selectors 144 and 145 by the selector 146.
The B signal is obtained by selecting the output of No. 5 with the selector 147.

[0011]

However, the above-mentioned conventional example has the following problems. Amplifier circuit 1
The signal amplification rates of 05 and 106 are controlled by the MPU 132.
6 has individual variations in operation, so MPU132
However, even if the same amplification factor is set, amplifiers 105 and 1
The actual amplification factor becomes a different value from 06, so that there may be a difference in the level of the video signal between the odd-numbered scanning line and the even-numbered scanning line.

Therefore, when color separation is performed by the method shown in FIG. 13, if a difference occurs in the signal levels of the odd-numbered scanning lines and the even-numbered scanning lines, vertical stripes with a 2-dot period are mixed in the G signal. . This significantly deteriorates the image. Further, if the band of the G signal is limited by using a low-pass filter that suppresses the frequency of the vertical stripes for the purpose of removing the vertical stripes, even necessary information is suppressed, resulting in deterioration of the resolution of the G signal. There was a problem of doing.

The present invention has been made to solve the above problems, and an object thereof is to obtain an image pickup apparatus capable of automatically calibrating the error of the amplification factors of two amplification circuits.

[0014]

According to the present invention, there are first and second output terminals, and signals of all pixels on an image pickup surface are non-additionally scanned and sequentially read out to output odd-numbered scanning line signals. Is output from one of the first and second output terminals, and at the same time, an even-numbered scanning line signal is output from the other terminal, and the first and second output terminals.
The same amplification rate is set to the first and second amplification means having variable amplification rates for amplifying the odd-numbered and even-numbered scanning line signals respectively obtained from the output terminals of the first and second amplification means. The storage means for storing the correction data indicating the actual difference between the respective amplification rates at this time and the amplification rates of the first and second amplification means are controlled, and are given to each amplification means at the time of this control. And a control unit configured to correct the amplification factor with the stored correction data to give the corrected amplification factor.

[0015]

According to the present invention, data for correcting the difference between the actual amplification rates when the two amplification means are set to have the same amplification rate is stored in advance, and the first and second correction data are used by using this correction data. By individually correcting the amplification factors to be given to the amplification units, it is possible to effectively and automatically calibrate the error in the amplification factors of the two amplification units during normal photographing without using a special subject.

[0016]

Embodiments of the present invention will be described below with reference to FIG. In FIG. 1, 1 is an imaging optical system for forming a subject image on an image sensor, and 2 is a CC as an all-pixel solid-state image sensor that reads out signals by sequential scanning.
D, 3, 4 are noise reduction circuits for reducing the noise of the output signal of the CCD 2, 5 and 6 are amplification circuits for amplifying the signals of the CCD 2 to an appropriate level, and 7 and 8 are AD for converting the signals of the CCD 2 into digital signals. It is a conversion circuit.

Reference numerals 9 and 10 denote input terminals of the process circuit 42,
Reference numerals 11, 12, 13, and 14 denote line memories for delaying a CCD signal by one scanning line time, and 15 denotes line memories 11 to 14.
A vertical contour extraction circuit for extracting a vertical contour signal from the signals of the 6 scanning lines synchronized by the line memory 11 to 16.
A color separation circuit for generating a GBR primary color signal from the signals synchronized at 14, a base clip circuit 17 for slicing a small amplitude portion of the vertical contour signal, a low pass filter 18 for limiting the band of the vertical contour signal, and 19 A horizontal contour extraction circuit for extracting a horizontal contour signal from the G signal, 20 is a base clip circuit for slicing a small amplitude portion of the horizontal contour signal,
Reference numeral 21 is a gain adjusting circuit for adjusting the gain of the horizontal contour signal, 2
2 is an adder for adding the horizontal contour signal and the vertical contour signal, 2
Reference numeral 3 is a gain adjusting circuit for adjusting the gain of the contour signal.

Reference numeral 24 is a detection circuit for detecting a frequency component which is 1/2 times the pixel sampling frequency from the G signal.
6, 27 are low-pass filters that limit the band of the signal, 2
8 is a white balance circuit for adjusting the white balance, 29 is an adder for adding the contour signal to the G signal, 30 is a high-pass filter for extracting the high frequency band of the G signal, 31, 32
Is an adder for adding the high frequency band of the G signal extracted by the high pass filter 30 to the R and B signals, 33, 34 and 35
Is a γ correction circuit.

Reference numeral 36 is a matrix circuit for generating a luminance signal Y and color difference signals RY and BY from the primary color signals, and 37 and 38.
Is a low-pass filter that limits the band of color difference signals, 39 is a scan conversion circuit, 40 and 41 are output terminals of a process circuit 42, 42 is a process circuit that processes a CCD signal, 4
Reference numeral 3 is an MPU that controls the amplification factors of the amplifier circuits 5 and 6, reference numeral 44 is an exposure detection circuit that extracts exposure information indicating the exposure state of the CCD 2 from Y, RY, and BY signals, and 45 is a memory.

Next, the operation of the above configuration will be described. The incident light from the subject is imaged by the imaging optical system 1 on the imaging surface of the CCD 2 which is an all-pixel imaging device,
2 is converted into an electric signal. A color filter array for color image pickup is attached to the image pickup surface on the CCD 2. This color filter array is, for example, an RBG Bayer array as shown in FIG.

The converted electric signal is transferred to the CCD 2
Two scanning lines are output in parallel from one output terminal. That is, the signal of the odd-numbered scanning line is output from one side, and the signal of the even-numbered scanning line is simultaneously output from the other side. The output signal from the CCD 2 is processed by the noise reduction circuits 3 and 4 and the amplification circuits 5 and 6, and then converted into a digital signal by the AD conversion circuits 7 and 8. The signals of the two scanning lines converted into digital signals are input to the input terminal 9,
10 is input to the process circuit 42, and the line memory 1
Signals for 6 scanning lines are synchronized by 1, 12, 13, and 14.

The signals of six scanning lines are vertical contour extraction circuit 15
And a vertical contour signal is extracted. The vertical contour extraction circuit 15 is composed of a vertical high-pass filter, and has a transfer characteristic as shown in FIG. 3, for example, when the number of pixels of the CCD 2 is 640 × 480. Further, the vertical contour signals for two scanning lines extracted by the vertical contour extraction circuit 15 are converted into a dot-sequential signal having a frequency twice that of the readout from the CCD 2 in order to reduce the circuit scale of the subsequent stage. That is, as shown in FIG. 4, the signals of the odd-numbered scanning lines and the even-numbered scanning lines are converted into time-division multiplexed dot-sequential signals. The vertical contour signal extracted by the vertical contour extraction circuit 15 is sliced into a small amplitude portion by the pace clip circuit 17 for noise reduction, and then an unnecessary band in the horizontal direction is removed by the low pass filter 18.

On the other hand, the signals synchronized by the line memories 11 to 14 are G in accordance with a timing signal from a timing generation circuit (not shown) in the color separation circuit 16.
Separated into BR primary color signals. These signals also have a form in which signals for two scanning lines are time-division multiplexed. Each signal is limited to an appropriate band by low pass filters 25, 26 and 27.

For example, in the case of the color filter array as shown in FIG. 2, since the G sampling points are present in each column, the horizontal band is ½ of the horizontal sampling frequency of the CCD 2. Therefore, the pass band of the low pass filter 25 is set to about 1/2 of the sampling frequency of the CCD 2. On the other hand, the sampling points for R and B are 1 in 2 columns.
Since there is only one, the band becomes 1/2 of the G signal, and the pass bands of the low pass filters 26 and 27 are set to about 1/4 of the sampling frequency of the CCD 2. An example of the transfer characteristic of the low-pass filter 25 is shown in FIG. 5A, and an example of the transfer characteristic of the low-pass filters 26 and 27 is shown in FIG. 5B.

The G signals separated at the same time are input to the horizontal contour extraction circuit 19 to extract horizontal contour signals. The extracted horizontal contour signal is processed by the base clip circuit 20 and the gain adjusting circuit 21, and then added by the adder 22 to the vertical contour signal. The added contour signal is adjusted to an appropriate level by the gain adjusting circuit 23, and then added to the G signal by the adder 29.

On the other hand, the level of the frequency component 1/2 times the sampling frequency of the G signal detected by the detection circuit 24 is input to the MPU 43 in order to detect an error in the amplification factor between the amplification circuits 5 and 6. To be done. Further, the respective signals band-limited by the low-pass filters 25, 26, 27 are changed in gain of the RB signal by the white balance circuit 28 so that the level of the white part is matched. Next, the high-pass filter 30 extracts the high band of the wide band signal, and the adders 31 and 32 add the high band to the R and B signals. The characteristics of the high-pass filter 30 are complementary to the characteristics of the low-pass filters 26 and 27, and are intended to align the bands of the G signal and the RB signal.

After that, after being .gamma.-corrected by .gamma.-correction circuits 33, 34 and 35, it is converted into a luminance signal Y and color difference signals RY and BY in a matrix circuit 36, and RY,
B-Y is band-limited to about 1/2 of the Y band by the low-pass filters 37 and 38. In addition, Y, RY, BY
3 signals are input to the exposure detection circuit 44 and the exposure information is detected. The detected exposure information is taken into the MPU 43, and the aperture value of the imaging optical system 1 and the amplification factors of the amplification circuits 5 and 6 are set to M so that the exposure becomes an appropriate value according to the illuminance of the subject.
It is controlled by the PU 43.

Finally, the Y, RY, and BY signals are input to the scan conversion circuit 39. In the scan conversion circuit 39, the input Y, RY, and BY are switched by a switching pulse generated by a timing generation circuit (not shown) to generate two systems of video signals for each scanning line. This signal is, for example, in the form of time-division in the order of Y, RY, Y, and BY by selecting RY and BY for each two pixels of Y. Y, RY, Y, B- at this time
All Y are signals on the same scanning line. The operation timing is shown in FIG. At this time, one clock of the output signal is Y
It is twice the sampling rate of the signal. When one of the two systems is taken out, this is an interlaced scanning signal, and when both are used, it becomes a progressive scanning signal. The two generated video signals are output from the output terminals 40 and 41.

FIG. 7 shows the structure of the color separation circuit 16 in detail. FIG. 8 shows the operation of the color separation circuit 16. The signals shown in FIGS. 8A to 8F are shown in FIG.
This corresponds to the signal of each part of (a) to (f). The color separation circuit 16 separates signals for one scanning line based on signals for three scanning lines. Since the G signal is obtained in a form in which the sampling phase is deviated by π for each scanning line, the signal of the central scanning line and the signal of the upper and lower scanning lines are alternately sampled to obtain the CCD signal (the output terminal of the CCD 2 ), A G signal having a period equal to the sampling frequency is obtained. 7 and 8 (a) show the signal of the central scanning line, and (b) shows the signal obtained by adding the upper and lower scanning lines. Switch these signals to switch 73
By selecting at the timing shown in (c),
The G signal shown in (d) is obtained. Although the 3H input signal in FIG. 7 has been described above, the G signal is separated by the same processing for the 4H signal.

Since the RB signal is obtained by sampling every other scanning line at a frequency half the sampling frequency of the CCD signal, the signal of the central scanning line and the signal of the upper and lower scanning lines are added together. Is sampled and held at a cycle twice as long as the sampling of the output signal of the CCD 2, and is alternately selected at a cycle twice the horizontal scanning frequency. That is, the signals shown in FIGS. 7 (e) and (f) are obtained by sampling and holding the signals of FIGS. 7 (a) and (b) with the D flip-flops 72 and 74 and the switches 75 and 76. When the center scanning line is a signal represented by 4H, the RB signal is similarly separated. After that, the signals for two scanning lines obtained as described above are time-division multiplexed at a frequency twice as high as the sampling frequency by the CCD signal switches 79, 80 and 81 to be combined into one system of signals.

On the other hand, the amplification circuits 5 and 6 are controlled by the MPU 43 so that the amplification factor is controlled so that the level of the video signal becomes appropriate.
When the amplification factor of 6 has an error, a difference occurs in the signal level between the odd-numbered scanning line and the even-numbered scanning line. If color separation is performed by the above method in this state, vertical stripe noise with a 2-dot period is mixed in the G signal as is apparent from FIG. 8D, and the image is significantly deteriorated. In order to solve this problem, error data of the amplification factor between the two amplification circuits 5 and 6 for each amplification factor is stored in the memory 45 of the MPU 43 in advance, and the MPU 43 uses the stored error data. The error may be corrected and the corrected data may be given to the amplifier circuits 5 and 6, respectively.

The error data is created at the time of initial adjustment (for example, at the time of factory shipment) and stored in the memory 45. As a method of creating the error data, for example, a method of picking up an image of a subject having a uniform screen and detecting the error of the amplification factor by the amount of the frequency component of the 2-dot cycle detected by the detection circuit 24 is used. Then, by correcting the value of the amplification factor given to the amplifier circuits 5 and 6 with this error data,
It is possible to automatically calibrate the error of the amplification factor between the two amplification circuits 5 and 6 at the time of normal photographing without using a special circuit.

[0033]

As described above, according to the present invention,
Data for correcting the difference between the actual amplification rates when the two amplification means are set to have the same amplification rate is stored in advance, and by using this correction data, it is possible to use the data for normal photography without using a special circuit. It is possible to effectively automatically calibrate the error of the amplification factor of the two amplification means.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a configuration diagram showing an example of a color filter array.

FIG. 3 is a characteristic diagram showing a transfer characteristic of a vertical contour enhancement circuit.

FIG. 4 is a timing chart showing an operation of time division multiplexing.

FIG. 5 is a characteristic diagram showing a transfer characteristic of a low-pass filter.

6 is a timing chart showing an output signal format from the process circuit in FIG.

7 is a configuration diagram of a color separation circuit 16 in FIG.

8 is a timing chart showing the operation of the color separation circuit in FIG.

FIG. 9 is a block diagram showing a conventional imaging device.

10 is a timing chart showing an operation of the 1H memory in FIG.

11 is a configuration diagram of a scan conversion circuit in FIG.

FIG. 12 is a timing chart showing the operation of the scan conversion circuit.

13 is a configuration diagram of a color separation circuit in FIG.

FIG. 14 is a timing chart showing the operation of the color separation circuit.

[Explanation of Codes] 2 CCD for All Pixels 5 and 6 Amplifier Circuits 11 to 14 1H Memory 16 Color Separation Circuit 36 Matrix Circuit 42 Process Circuit 43 MPU 44 Exposure Detection Circuit 45 Memory

Claims (6)

[Claims] 1. A first and second output terminal, wherein signals of all pixels on an image pickup surface are non-additively scanned and sequentially read out, and odd-numbered scanning line signals are output as the first and second outputs. Image pickup means configured to output from one of the terminals and simultaneously output even-numbered scanning line signals from the other terminal; and the odd-numbered one obtained from the first and second output terminals,
The difference between the actual amplification factors when the same amplification factor is set in the first and second amplification units and the amplification factor variable first and second amplification units for amplifying the even-numbered scanning line signals, respectively. Storage means for storing the correction data shown, and the amplification factors of the first and second amplification means are controlled, and in this control, the amplification factor given to each amplification means is stored by the stored correction data. And a control unit configured to correct and provide a corrected amplification factor. 2. A signal processing means for processing the output of the image pickup means, and a detection means for detecting the state of exposure to the image pickup means from the processed signal are provided, and the control means comprises:
The image pickup apparatus according to claim 1, wherein an amplification factor to be given to the first and second amplification units is determined according to the detection of the detection unit, and the determined amplification factor is corrected by the correction data. . 3. A signal processing means for processing the output of the image pickup means is provided, and the correction data is processed by the signal processing means when the image pickup means picks up a uniform subject on an image pickup surface. The image pickup apparatus according to claim 1, wherein the image pickup apparatus is created based on a signal. 4. The signal processing means is configured to output the luminance signal and the color difference signal by performing processing such as synchronization of the image pickup means, color separation, and matrix processing. Item 2. The image pickup device according to item 2 or 3. 5. The image pickup means is an all-pixel readout CCD
The imaging device according to claim 1, further comprising: 6. The image pickup apparatus according to claim 1, wherein an RGB color filter arranged in a Bayer pattern is provided on an image pickup surface of the image pickup means.