JPH08307882A - Image pickup device - Google Patents

Abstract

PURPOSE: To prevent coloring due to a difference between channels and to simplify the automatic exposure adjustment by automatically adjusting a gain of a white balance amplifier and a gain of an AGC amplifier at all times with independent color channels. CONSTITUTION: The device is provided with a timing generating section 6 generating a gain detection pulse for a vertical blanking period of a video signal and an adder means 14 adding the gain detection pulse to each channel video signal. An output signal of a solid-state image pickup element 5 provided to each of three primary colors is converted into a digital signal via a correlation dual sampling circuit 7, an adder means 14, a white balance (W/B) amplifier 8, an AGC amplifier 9, a clamp circuit 10 and an A/D converter 11. A digital signal processing circuit DSP12 detects the amplitude of the video signal to which a gain detection pulse is added to adjust each gain of the W/B amplifier 8 and the AGC amplifier 9 via a controller 13. Thus, even when the AGC gain is increased, deviation in carrier balance and a black shading deviation are corrected. Moreover, even when a part of an optical system is not connected, automatic exposure is easily adjusted.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a camera-integrated V
The present invention relates to a three-plate type image pickup device having a solid-state image pickup device such as a CCD for each of the three primary colors of R, G and B, such as TR.

[0002]

2. Description of the Related Art A conventional image pickup apparatus of this type is shown in FIG.
13 to 13 will be described below. Here, FIG. 9 is a block diagram showing a conventional image pickup apparatus, FIG. 10 is a flowchart showing a case where A / E adjustment is performed in the conventional image pickup apparatus, and FIG. 11 is W / B adjustment in the conventional image pickup apparatus. FIG. 12 is a flow chart showing a case of performing the operation, FIG. 12 is an explanatory view showing a relationship between an AGC gain and a carrier balance deviation amount in the conventional imaging apparatus, and FIG. 13 is a relationship between an AGC gain and a black shading deviation amount in the conventional imaging apparatus. It is an explanatory view shown.

In FIG. 9, 1 is a lens, 2 is an iris, 3 is an optical low-pass filter, and 4 is incident light.
Prism that splits into channels (R, G, B3 primary colors),
5 is a CCD solid-state image sensor (hereinafter referred to as CCD) that photoelectrically converts an optical image into a video signal, 6 is a timing generator (hereinafter referred to as TG) that generates a drive pulse for the CCD 5, and 7 is a sampled video signal component only. Correlation 2
A heavy sampling circuit (hereinafter, referred to as CDS circuit), 8 is a white balance amplifier (hereinafter, referred to as W / B amplifier) that performs white balance, and 9 is an auto gain control amplifier (that amplifies video signals of 3 channels with the same gain ( Hereinafter referred to as an AGC amplifier).

Reference numeral 10 denotes an A / D converter 11 for the video signal.
Clamp circuit for DC clamping to the reference level of
Reference numeral 12 denotes a digital signal processing circuit (hereinafter referred to as a DSP circuit) which performs various signal processing on the digital video signal obtained by the A / D converter 11, and 13 denotes a W / B amplifier 8 and A.
This is a control circuit for controlling the GC amplifier 9 with a DC voltage.

In the above structure, the DSP circuit 12
Is the camera signal processing (eg γ correction, matrix etc.)
Luminance signal Y and dot-sequential color difference signal RY / B
-Y, a CORE section 12a for outputting to a subsequent encoder or a digital VTR section (not shown), and an A / E
(Automatic exposure), A / W (automatic white balance) and A /
A D_AUTO circuit 12b that constantly detects a luminance signal value, a color difference signal value, etc. as data for performing F (automatic focus),
A synchronization signal generator (hereinafter referred to as SSG) that generates various timing pulses inside the DSP 12 while synchronizing with the TG 6.
12c).

In the image pickup device constructed as described above, the light incident from the lens 1 passes through the iris 2, the optical low-pass filter 3 and the prism 4, and then R, G,
After being split into B, it is photoelectrically converted by the CCD 5 to obtain a video signal. The obtained 3-channel video signals are independently sampled in the CDS circuit 7 for only the signal components, and after white-balanced by the W / B amplifier 8, the same gain is applied to all 3 channels by the AGC amplifier 9. The signal is amplified, DC clamped by the clamp circuit 10 to the reference level of the A / D converter 11, and converted into a digital signal by the A / D converter 11.

The digital video signal is C of the DSP circuit 12.
After the camera signal processing such as γ correction and matrix is performed in the ORE unit 12a, the luminance signal Y and the dot-sequential color difference signal R are obtained.
-Y / B-Y is output to the encoder or digital VTR unit (not shown) in the subsequent stage.

Also, in D_AUTO12b, A / E
(Automatic exposure), A / W (automatic white balance) and A /
Data such as a luminance signal value and a color difference signal value for performing F (auto focus) is detected, and the obtained data is output to the control circuit 13.

That is, when the A / E adjustment is performed, as shown in FIG.
As shown in 0, first, A / in the D_AUTO 12b
The E detection unit integrates the divided brightness signals of each block to detect the brightness level and outputs the brightness level to the control circuit 13.
The control circuit 13 gives weights and the like according to various scenes to the integrated value data from each block, and holds the iris 2 and the AGC amplifier 9 so as to maintain the appropriate A / E level (reference value) of the entire screen. A control voltage is applied to.
Since the control system is closed, the correct A /
It is held at E level, but cannot be adjusted without an input video signal.

When adjusting the W / B, as shown in FIG. 11, first, as shown in FIG. 11, the A / E detection section in the D_AUTO 12b outputs I for the color difference signal for each divided block.
The Q-converted one is integrated to detect the W / B level and output to the control circuit 13. In the control circuit 13, weighting etc. according to various scenes is given to the integrated value data from each block, and a control voltage is given to the W / B amplifier 8 so that the W / B of the entire screen can be properly obtained. . In the case of full auto W / B, since the control system is closed, it always converges to the state where W / B is always taken, but the time constant of W / B is increased in relation to A / E. It needs to be taken and it takes time to converge.

[0011]

In the case of the above-mentioned conventional image pickup device, the control circuit 13 controls the W / B amplifier 8 and the AGC amplifier 9 by the DC voltage. Since the loop processing such as AGC does not converge, there is a problem that the adjustment cannot be performed unless the so-called optical system portion from the lens 1 to the CDS circuit 7 is connected for the adjustment of the AGC system.

Since W / B inputs control signals independent of three channels, if an A / W loop is applied, W / B
There is no particular problem in the variation of the B amplifier 8, but the AGC is 3
Since the same control signal is used for both channels, when variations occur such as when the gain increases,
A coloring phenomenon occurs, which is a disadvantage of the three-plate type. this is,
This is because it is generally necessary to set the W / B time constant longer than the time constant of the AGC system.

That is, when a still image is picked up under a uniform light source, the W / B absorbs variations, so that coloring is not noticeable, but in general indoor shooting, the AGC amplifier 9 gain is high. Therefore, there is a problem that a coloring phenomenon occurs when capturing a moving image with a large variation in AGC gain.

Further, as the gain of the AGC amplifier 9 increases, the error due to the subtle offset of the circuit also increases, so that the difference in the gains of the W / B amplifier 8 of the three channels and the AGC of the AGC amplifier are increased.
There is a problem that the black level also varies due to the variation between the channels of the amplifier 9 itself, and so-called carrier balance shift occurs.

In order to prevent this, generally, in a single-chip CCD camera system with a complementary color filter, as shown in FIG. 12, the deviation of the AGC gain and the carrier balance is plotted in advance, and two points are set in the control circuit. A linear approximation is performed from the characteristics of the amplifier gain at about 3 points to perform the operation to absorb the offset deviation.
Is located in front of the AGC amplifier 9, the W / B amplifier 8
Since the gain changes more and more depending on the color temperature of the subject, the total gain of the W / B amplifier 8 and the AGC amplifier 9 must be managed for 3 channels. Therefore, a simple linear approximation method such as the single plate method gives satisfactory results. Is not obtained,
Not only the residual error but also the variation between each channel exists.

Further, when the AGC gain becomes high,
Due to the difference in gain of the W / B amplifier 8 of 3 channels and the variation between channels of the AGC amplifier 9 itself, the CCD 5,
Since slight black shading due to circuits such as the W / B amplifier 8 and the AGC amplifier 9 also varies, this also causes a coloring phenomenon. Again, as shown in FIG. 13, satisfactory results cannot be obtained by a simple linear approximation method such as the single plate method as described above, and there are not only residual errors but also variations among channels.

The present invention has been made in view of the above point, and simplifies the adjustment of A / E by always obtaining the gains of the W / B amplifier and the AGC amplifier independently for each channel. At the same time, it is an object of the present invention to provide an imaging device capable of preventing a coloring phenomenon due to a difference between channels when a gain is large.

[0018]

The image pickup apparatus according to the present invention has three components.
A solid-state image sensor provided for each primary color, a white balance amplifier and an auto gain control amplifier, a timing generating means for generating a gain detection pulse during a vertical blanking period of a video signal, and a stage before the white balance amplifier. Adding means for adding the gain detection pulse to the video signal of each channel, an A / D converter for converting the video signal passing through the auto gain control amplifier into a digital signal, and the gain detection pulse by the adding means. Detecting means for detecting the amplitude of the added video signal, and control means for obtaining the total gain of the white balance amplifier and the automatic gain control amplifier by constantly monitoring the amplitude value detected by the detecting means. It is equipped with and.

[0019]

In the image pickup apparatus of the present invention, the adjustment value of the A / E (automatic exposure control) system including the gain adjustment of the iris, the white balance amplifier and the AGC amplifier is added to the detected value of the amplitude of the gain detection pulse. By controlling, it is possible to perform only by the circuit system without connecting the optical system.

Further, by independently detecting the gain of each channel, it is possible to minimize the deterioration of the performance due to the variation between the channels of the AGC amplifier and the peripheral circuit system, which is the disadvantage of the three-plate system.

Further, the carrier balance and the black shading shift which are likely to occur when the AGC gain increases can be corrected according to the gain of each channel because the gain of each channel is always observed.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the image pickup apparatus of the present invention will be described below with reference to FIG.
5 to FIG. 5, the same parts as those in the above-mentioned conventional example are designated by the same reference numerals, and the description thereof will be omitted.

Here, FIG. 1 is a block diagram showing the image pickup apparatus of the present embodiment, FIG. 2 is a timing chart of gain detection pulses showing the image pickup apparatus of the present embodiment, and FIG. 3 is addition in the image pickup apparatus of the present embodiment. FIG. 4 is a circuit diagram showing a circuit, and FIG. 4 is a block diagram showing a gain detection unit in the image pickup apparatus of this embodiment.

FIG. 5 is a flow chart showing a case where the initial adjustment of W / B and A / E in the image pickup apparatus of this embodiment is carried out, and FIG. 6 is a normal adjustment of A / E in the image pickup apparatus of this embodiment. FIG. 7 is a flowchart showing a case, FIG. 7 is a flow chart showing a shift amount table relating to carrier balance and black shading in the image pickup apparatus of the present embodiment, and FIG. 8 is an adjustment to gain relating to carrier balance and black shading in the image pickup apparatus of the present embodiment. It is a flowchart which shows a case.

As shown in FIG. 1, the image pickup apparatus of this embodiment has a DSP 12 in the conventional example described above with reference to FIG.
An adder circuit 14 is provided which generates a gain detection pulse from the internal SSG 12c and adds the gain detection pulse to the video signal output from the CDS circuit 7 at a predetermined mixing ratio. Also, the D inside the DSP 12
The _AUTO 12b is provided with a gain detection unit capable of detecting the gain independent of three channels by detecting the average value of the level of the gain detection pulse for each channel.

In FIG. 2, GDP1 and GDP2 are gain detection pulses, which are mixed with the video signal in the adder circuit 14. Also, while GDP3 is at the H level, GDP1 and GDP
A video signal in which a portion corresponding to the L level of DP2 is mixed is detected.

In the adder circuit 14, as shown in FIG. 3, the video signal is added through the resistor R1, the gain detecting pulse GDP1 is passed through the resistor R2, and the gain detecting pulse GDP3 is passed through the resistor R3. It is buffered by the transistor Q1 and the resistor R4 and output to the W / B amplifier 8 in the next stage.

The resistance value ratio at this time is selected so that the gain detection pulse GDP1 is smaller than the gain detection pulse GDP2. For example, when R2 = 10 × R3, the gain detection pulse GD is used when the gain is small.
By detecting the period in which P2 is mixed and detecting the period in which the gain detection pulse GDP1 is mixed when the gain is large, it is advantageous in terms of S / N and effective in the dynamic range. You can

The ratio to R1 is the amplitude of the video signal,
A ratio is selected in consideration of the amplitudes of the gain detection pulses GDP1 and GDP2 before mixing. For example, when the amplitude of the video signal is 200 mV, the amplitude of the gain detection pulses GDP1 and GDP2 before mixing is 5 V, and the amplitude after mixing is 20 mV and 200 mV, roughly, R
2 = (200 mV / 5V) × R1. R1 to 100
If Ω, R2 is 2.5 kΩ and R3 is 25 kΩ.

Needless to say, the above-mentioned numerical values are examples, and the ratio for mixing the gain detection pulses GDP1 and GDP2 and the kind of the pulse of the gain detection pulse GDP are not limited.

The gain detector in the D_AUTO 12b is
As shown in FIG. 4, the gain detection pulses GDP1 to GD
An integrating circuit 21 that simply integrates the timing level corresponding to P3, and a latch circuit 22 that holds the obtained data.
And a selector circuit 23 that selects detection data by a control signal such as address data from the control circuit 13 and has a circuit configuration independent of R, G, and B channels.

In the control circuit 13, the obtained gain data, to be precise, the gain detection pulses GDP1, GDP2,
By constantly observing the data of the level integration value at the timing corresponding to GDP3, the W / B amplifier 8 and the AGC are
The total gain of the amplifier 9 can be detected. At this time, data corresponding to GDP3 can be obtained in addition to the gain detection pulses GDP1 and GDP2. Therefore, by using the difference from this data, it is possible to eliminate the influence of offset deviation that tends to occur when the gain becomes large. You can

In the above-described embodiment of the image pickup apparatus of the present invention, when performing the initial adjustment of W / B and A / E, FIG.
As shown in FIG. 6, since the gain detection pulse can be used as the input signal even if the so-called optical system part is not connected, the W / B amplifier 8 and the AGC amplifier 9 are set so that the gain detection pulse becomes the reference level. The initial settings can be made. The normal A / E operation with the optical system connected after the initial setting is almost the same as that of the conventional example described above, as shown in FIG.

Further, by detecting the gain of each channel, it is possible to monitor the relative gain and control so that the gain of each channel is always the same.
In this control, if the control voltage of the AGC amplifier 9 is independent for each channel, each may be controlled. However, when the control voltage of the AGC amplifier 9 is common, W / B
The gain of the amplifier 8 may be used for fine adjustment.

The normal operation of W / B is the same as that of the above-mentioned conventional example, but the variation of the gain of the AGC amplifier 9 is suppressed, so that a moving image with a large variation of the AGC gain is taken. However, stable W / B operation can be performed.

Further, in this embodiment, since the total gain of the W / B amplifier 8 and the AGC amplifier 9 can be independently obtained for three channels, as shown in FIGS. 7 and 8, carrier balance and black shading are also First, it is possible to absorb an error due to variation between channels. Next, it is possible to plot the relationship between the gains at a plurality of points and the shift amounts of the carrier balance and the black shading independently for the three channels, and it is possible to have a table with very few errors. By these, the occurrence of the coloring phenomenon can be significantly suppressed.

[0037]

According to the image pickup device of the first aspect,
By detecting and managing the amplitude value of the gain detection pulse, the A / E system adjustment consisting of each gain adjustment of the iris, W / B amplifier, and AGC amplifier can be performed only by the circuit system without connecting the optical system. It can be performed.

Further, by independently detecting the gain of each channel, it is possible to minimize the deterioration of the performance due to the variation between the channels of the AGC amplifier and the peripheral circuit system, which is a disadvantage of the three-plate type image pickup device.

Further, regarding the carrier balance and the black shading shift which are likely to occur when the AGC gain is increased, the gain for each channel is always observed, so that the correction can be performed according to the gain.

In the image pickup device according to the second aspect, the ratio of the amplitudes of the gain detection pulses to be added is varied, and when the total gain is large, the control means outputs the data of the gain detection pulses added with a small amplitude. When the total gain is relatively small, the data of the gain detection pulse added at other amplitude ratios is used, so that reliable detection with a small error can always be performed.

In the image pickup device according to the third aspect, the data of the signal portion to which the gain detecting pulse is not added is also detected, and the data of the signal portion to which the gain detecting pulse is added and the gain detecting pulse are detected. The gain can be detected more accurately by calculating the data of the signal portion that has not been added.

[Brief description of drawings]

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

FIG. 2 is a timing chart of gain detection pulses showing an embodiment of the image pickup apparatus of the present invention.

FIG. 3 is a circuit diagram showing an adder circuit in an embodiment of the image pickup apparatus of the present invention.

FIG. 4 is a block diagram showing a gain detection unit in an embodiment of the image pickup apparatus of the present invention.

FIG. 5 is a flowchart showing a case where initial adjustment of W / B and A / E is performed in an embodiment of the image pickup apparatus of the present invention.

FIG. 6 is a flow chart showing a case where normal adjustment is performed in an embodiment A / E of the image pickup apparatus of the present invention.

FIG. 7 is a flowchart showing creation of a shift amount table regarding carrier balance and black shading in an embodiment of the image pickup apparatus of the present invention.

FIG. 8 is a flow chart showing a case where a gain relating to carrier balance and black shading is adjusted in an embodiment of the image pickup apparatus of the present invention.

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

FIG. 10 is a flowchart showing a case where A / E is adjusted in a conventional image pickup apparatus.

FIG. 11 is a flowchart showing a case where W / B adjustment is performed in a conventional image pickup apparatus.

FIG. 12 is an explanatory diagram showing a relationship between an AGC gain and a carrier balance deviation amount in a conventional image pickup apparatus.

FIG. 13 is an explanatory diagram showing a relationship between an AGC gain and a black shading shift amount in a conventional image pickup apparatus.

[Explanation of symbols]

 1 Lens 2 Iris 3 Optical Low-pass Filter 4 Prism 5 CCD Solid-state Image Sensor 6 Timing Generator 7 Correlation Double Sampling Circuit 8 White Balance Amplifier 9 Auto Gain Control Amplifier 10 Clamp Circuit 11 A / D Converter 12 Digital Signal Processing Circuit 13 Control Circuit 14 Adder circuit

Claims (3)

[Claims] 1. A solid-state image sensor provided for each of the three primary colors, a white balance amplifier and an auto gain control amplifier, timing generation means for generating a gain detection pulse during a vertical blanking period of a video signal, and the white color. An adding means for adding the gain detection pulse to the video signal of each channel in the preceding stage of the balance amplifier, an A / D converter for converting the video signal passing through the auto gain control amplifier into a digital signal, and the adding means. Detecting means for detecting the amplitude of the video signal to which the gain detecting pulse is added, and the total gain of the white balance amplifier and the auto gain control amplifier by constantly monitoring the amplitude value detected by the detecting circuit. And a control means for obtaining . 2. The image pickup apparatus according to claim 1, wherein at least two types of gain detection pulses are generated by the timing generation means, and the amplitude of each gain detection pulse added to the video signal by the addition means Equipped with an amplitude varying means for varying the ratio, the control means uses the data of the gain detection pulse added with a small amplitude when the total gain is large, and adds it with other amplitude ratios when the total gain is relatively small. An image pickup apparatus, wherein data of a pulse for gain detection is used. 3. The image pickup device according to claim 1 or 2, wherein the detection means also detects data of a signal portion to which the gain detection pulse is not added, and the control means adds the gain detection pulse. An image pickup apparatus, wherein the gain can be accurately detected by calculating the data of the signal portion and the data of the signal portion to which the gain detection pulse is not added.