JP3843877B2 - Imaging device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an imaging apparatus, and more particularly to an imaging apparatus that performs inter-channel correction using a reference signal for an output imaging signal of a solid-state imaging device having a plurality of channel (ch) outputs.
[0002]
[Prior art]
In recent years, the number of pixels in image pickup devices using solid-state image pickup devices has been increasing dramatically due to the demand for higher resolution in the market as the microfabrication technology for large-scale semiconductor integrated circuit (LSI) processes advances and develops. It is in. As the number of pixels of an imaging device increases, the number of pixels per line of the solid-state image sensor increases, but the time for outputting a video signal of one line from the solid-state image sensor is defined by the television standard. For this reason, the signal readout clock frequency generally increases in proportion to the number of pixels, and accordingly, the operating frequency of the signal processing circuit at the subsequent stage also increases, which increases circuit design constraints. In addition, it is necessary to carefully take measures against noise and radiation.
[0003]
Therefore, conventionally, as a means for avoiding these troubles, the imaging area of the solid-state imaging device is divided into two, for example, left and right as shown in FIG. 2. Description of the Related Art There is known an imaging apparatus configured to read a signal output from a solid-state imaging device at a half frequency required by an imaging apparatus that does not divide an area.
[0004]
In FIG. 5, the solid-state imaging device includes divided areas 1A and 1B in which the imaging area is divided into right and left, and an optical black level area (OB area) provided at the end in the vertical direction of the divided areas 1A and 1B. 2A, 2B, a vertical pilot injection portion 3 provided at the upper end of the divided areas 1A, 1B, and a vertical OB area 4 provided at the upper end and the lower end of the divided areas 1A, 1B, The OB area 4 at the lower end is connected to horizontal transfer paths (hereinafter referred to as horizontal CCDs) 6A and 6B composed of CCDs (charge transfer elements) via oblique shift regions 5A and 5B. The horizontal CCDs 6A and 6B are horizontal pilots. It is connected to output amplifiers 8A and 8B via injection parts 7A and 7B.
[0005]
The charges from the pixels arranged in the two-dimensional matrix constituting the imaging area 1A and the OB areas 2A and 4 are vertically transferred by a vertical CCD (not shown), transferred to the horizontal CCD 6A through the oblique shift region 5A, and further The horizontal CCD 6A is transferred from the left to the right in the figure, and output from the output amplifier 8A as a ch1 imaging signal.
[0006]
On the other hand, the charges from the pixels arranged in a two-dimensional matrix constituting the imaging area 1B and the OB areas 2B and 4 are vertically transferred by a vertical CCD (not shown) and transferred to the horizontal CCD 6B via the oblique shift region 5B. Further, the horizontal CCD 6B is transferred from the right to the left in the figure, and is output from the output amplifier 8B as the ch2 imaging signal. The OB areas 2A, 2B, and 4 are each composed of a plurality of pixels per line. However, the OB areas 2A, 2B, and 4 are configured to shield incident light, and therefore output a signal level when there is no light.
[0007]
In such a configuration in which the imaging area is divided into left and right, the signal readout clock frequency is half that of an imaging device that does not divide the imaging area. Is advantageous. However, on the other hand, in the conventional image pickup apparatus of FIG. 5 having two independent signal output channels in which the image pickup area is divided into right and left, the transfer efficiency difference between the horizontal and vertical CCDs of each channel and between the output amplifiers 8A and 8B. As shown in FIG. 6, an output level difference is generated in each line output between ch1 and ch2. Further, as shown in FIG. 6, the output of the latter stage having a larger number of transfer stages is attenuated than the initial output.
[0008]
Therefore, in the imaging apparatus shown in FIG. 5, the pilot injection unit 3 directly injects a charge as a pilot (reference) signal of a predetermined level into the imaging signals of the imaging areas 1A and 1B transferred in the vertical direction. The pilot injection units 7A and 7B directly inject electric charge as a pilot (reference) signal of a predetermined level into an imaging signal transferred in the horizontal direction to correct the output level difference between the channels. .
[0009]
In the case of injecting into the vertical CCD, for example, as shown in FIG. 5, a constant charge is injected into a so-called dummy pixel of the vertical CCD located at the subsequent stage of image output. As a result, a pilot signal having a predetermined level in units of pixels is output after the data is output. FIG. 7A shows the vertical synchronization signal of ch1, and FIG. 7B shows the image data D1 and pilot signal P1 of ch1. FIG. 7C shows the ch2 vertical synchronizing signal, and FIG. 7D shows the ch2 image data D2 and the pilot signal P2. By detecting the level difference between the pilot signals P1 and P2, which are originally at the same level, and adjusting the level so that the level difference becomes zero, the output level difference between the channels can be corrected.
[0010]
The horizontal transfer pulse for driving the horizontal CCD 6A and the horizontal transfer pulse for driving the horizontal CCD 6B are out of phase with each other, and the divided imaging area 1A is changed from the pixel near the center of the screen to the pixel on the left side of the screen. Since the divided imaging area 1B is horizontally transferred in the direction from the pixel near the center of the screen to the pixel on the right side of the screen and read from the output amplifier 8B, the divided imaging area 1B is read out from the output amplifier 8B. The number of charge transfer stages in the horizontal direction at the boundary between 1A and 1B can be made the same. Thereby, it is possible to prevent the discontinuity of the image due to the difference in the number of transfer stages in the horizontal direction of charges at the boundary portion at the center of the screen.
[0011]
[Problems to be solved by the invention]
By the way, when the above-described vertical pilot signals P1 and P2 are illustrated in the horizontal direction, waveforms having variations as shown in FIGS. 8B and 8C are obtained. FIG. 8A shows a horizontal synchronization pulse HD. Here, if the target output level (peak value) is set to 200 mV, for example, and the pilot signal output difference is P1 / P2 = 2 times, when P1 is 190 mV due to the reduction due to efficiency, the output of P2 is correct at 95 mV However, in the imaging apparatus described above, an error occurs due to variations in the barrier of each injection pixel.
[0012]
The present invention has been made in view of the above points, and an object thereof is to provide an imaging apparatus capable of improving the level correction accuracy between channels.
[0013]
Another object of the present invention is to provide an imaging apparatus capable of removing the influence of smear generation.
[0014]
[Means for Solving the Problems]
To achieve the above object, the present invention uses a solid-state imaging device in which a vertical pilot injection section is provided in each of the divided imaging areas obtained by dividing the imaging area into a plurality of parts in the horizontal direction. An image pickup apparatus for obtaining video signals of a plurality of channels obtained by picking up an image of a pilot signal charge in a signal charge vertically transferred by a vertical pilot injection portion provided corresponding to each of a plurality of divided image pickup areas. Injecting means for injecting at different potentials multiple times per unit time, and output signals of each channel consisting of video signals per unit time and a plurality of vertical pilot signals output in parallel from a plurality of divided imaging areas A pilot signal level detecting means for detecting a plurality of vertical pilot signal levels for each channel, and a pilot signal level detecting means; The difference value of the plurality of vertical pilot signal levels detected for each channel is calculated for each channel, and each of the difference values of the calculated channels are output in parallel from the plurality of divided imaging areas so that they are equal to each other. And a level control means for controlling the level of the output signal of the channel, and the video signal level-controlled by the level control means is output.
[0015]
In the present invention, since the pilot signal having no potential barrier variation is detected based on the difference value between the pilot signal levels in the plurality of vertical directions, the detection accuracy of the pilot signal can be improved.
[0016]
In order to achieve the above object, according to the present invention, a horizontal pilot injection unit for injecting a pilot signal charge is further provided for each channel in the video signal charge of each channel transferred horizontally. Further has a function of injecting a pilot signal charge into a signal that is horizontally transferred by a horizontal pilot injection unit, and the pilot signal level detecting means includes a horizontal pilot signal injected by a horizontal pilot injection unit. The level control means further detects the level of the output signal of each channel output in parallel from the plurality of divided imaging areas so that the horizontal pilot signal levels detected for each channel are equal to each other. It further has a function to control.
[0017]
In the present invention, the level of the pilot signal in the horizontal direction is detected for each channel, and the output of each channel output in parallel from a plurality of divided imaging areas is made so that the detected horizontal pilot signal level of each channel is equal to each other. Since the signal level is controlled, variations in the level of the output signal of each channel due to the gain difference between the channels can be corrected.
[0018]
In order to achieve the above object, the present invention provides a smear from an output signal of each channel comprising a video signal per unit time and a plurality of vertical pilot signals output in parallel from a plurality of divided imaging areas. The control means further includes smear detection means for detecting the component for each channel, and when the detection signal indicating smear generation is input from the smear detection means, the control means converts the pilot signal excluding the pilot signal in the smear occurrence area to the difference value. It is used for calculation. In the present invention, a vertical pilot signal on which smear components are superimposed can be prevented from being used for level control.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 shows a block diagram of a first embodiment of an imaging apparatus according to the present invention. In the figure, the solid-state imaging device 11 has the configuration shown in FIG. 5, and charges are directly injected as a pilot signal of a predetermined level into the imaging signals of the imaging areas 1 </ b> A and 1 </ b> B transferred in the vertical direction by the pilot injection unit 3. To do. Since the charge injection method itself is known (for example, JP-A-6-86181, JP-A-8-125934, etc.), detailed description thereof is omitted.
[0020]
Here, the injection of the pilot charge is performed by applying an injection pulse to a predetermined electrode of the CCD. However, the above-described variation in the potential of the pilot signal in units of pixels transfers the injected pilot charge. This is caused by a variation in potential barrier generated on the CCD substrate directly under the electrode. The variation in the potential barrier is unique to the pixel and takes a constant value with respect to the injected charge.
[0021]
Therefore, in the present embodiment, pilot charge injection is performed on the imaging signals of the imaging areas 1A and 1B transferred in the vertical direction by the pilot injection unit 3 of the solid-state imaging device 11 having the configuration shown in FIG. This is performed twice, for example, in the vertical blanking period, and the injection charge amount is changed between the first time and the second time at this time, thereby absorbing the potential barrier variation. That is, assuming that the output level of the pilot signal injected at the first time is PV1 and the output level of the pilot signal injected at the second time by changing the injected charge amount is PV2, the following expression Pch = | PV1-PV2 | (1)
Is used as a pilot signal to correct the potential barrier variation.
[0022]
A timing generator (TG) 14 shown in FIG. 1 supplies a horizontal transfer pulse, a vertical transfer pulse, a pilot signal, and the like to the solid-state imaging device 11, and for the pilot signal, for example, a pilot signal of 2.0V, A pilot signal of 3.0 V is sequentially injected in the same field, or is injected into the pilot injection unit 3 shown in FIG. 5 in the vertical blanking period in time series.
[0023]
As a result, of the two divided imaging areas of the solid-state imaging device 11, the ch1 video signal and the OB signal D1 shown in FIG. 2B are displayed together with the vertical synchronization signal shown in FIG. 2A from the ch1 divided imaging area. Then, the pilot signals P11 and P12 are extracted, and the ch2 video signal and OB signal D2 shown in FIG. 2D and the pilot signal P21 together with the vertical synchronizing signal shown in FIG. And P22 are taken out.
[0024]
The left and right two-channel video signals, OB signals, and pilot signals output in parallel from the two divided imaging areas of the solid-state imaging device 11 are respectively supplied to a correlated double sampling (CDS) circuit 12, where the OB signals are converted into OB signals. After predetermined signal processing such as known OB clamping processing and CDS processing is performed for each channel, the signal is supplied to an AD converter (ADC) 13 and converted into a digital signal separately. The two-channel signal extracted from the ADC 13 is supplied to the pilot signal level detection / smear detection unit 16 to detect the pilot signal level and the presence or absence of smear for each channel.
[0025]
Here, the pilot signal level detected by the pilot signal level detection / smear detection unit 16 is such that the pilot signals P11 and P21 at the time of the pilot signal injection of 2.0 V described above are as shown in FIG. If the pilot signal P12, P22 at the time of pilot signal injection of 3.0V is 300 mV (= PV2) as shown in FIG. 3B, for example, the control unit 15 Based on the pilot signal level detected by the level detection / smear detection unit 16, the calculation of the equation (1) is performed, and a pilot of 100 mV (= | 200 mV−300 mV |) as shown in FIG. It is determined that the signal Pch has been reproduced.
[0026]
The calculation of the pilot signal Pch by the calculation of the above equation (1) is performed for each channel. That is, the control unit 15 calculates the pilot signal Pch1 of the first channel ch1 from the pilot signals P11 (= PV1) and P12 (= PV2) of the first channel ch1 by the equation (1), and also for the second channel ch2. Similarly, the pilot signal Pch2 is calculated from the pilot signals P21 (= PV1) and P22 (= PV2) of the second channel ch2 by the equation (1).
[0027]
The control unit 15 calculates the above pilot signals Pch1 and Pch2 for the two-channel video signal, OB signal, and pilot signal supplied to the gain correction unit 17 via the pilot signal level detection / smear detection unit 16. Are corrected so that they are equal. The two-channel video signal output from the gain correction unit 17 is supplied to the YC processing unit 18, where the luminance signal Y and the color signal C are subjected to predetermined signal processing.
[0028]
Here, the pilot signal is output from the solid-state imaging device 11 following the video signal and the vertical OB signal. However, the pilot signal is added to the pilot signal so that the vertical OB signal is affected by smear (the smear component is superimposed on the OB signal). Also smear components are superimposed. Therefore, since correction between channels cannot be performed when smear occurs, the pilot signal level detection / smear detection unit 16 detects smear generation, and supplies the detection signal to the control unit 15 when smear occurs. Smear occurs when, for example, a smear component superimposed on a vertical OB signal (black reference signal) is compared with, for example, an OB average value and takes a value (level) greater than a specific value, smear occurs at that pixel. Suppose you are.
[0029]
When the smear detection signal is input, the control unit 15 excludes the pixel in which smear is generated from the gain correction by the pilot signal PV in the gain correction unit 17, or when the smear occurs, the correction calculation is data before the smear is generated. Is used. As a result, it is possible to prevent malfunction caused by the smear component being superimposed on the vertical pilot signal.
[0030]
In addition, according to the present embodiment, pilot charge is injected twice, for example, in the vertical blanking period, and the injected charge amount is changed between the first time and the second time, and the difference between the pilot signal outputs is changed. Since the two channels are made equal, it is possible to improve the level correction accuracy between channels by absorbing the variation in potential barrier and increasing the pilot detection accuracy.
[0031]
Next, a second embodiment of the present invention will be described. FIG. 4 shows a block diagram of a second embodiment of the imaging apparatus according to the present invention. In the figure, the same components as in FIG. This embodiment is characterized in that gain correction is performed by an analog circuit (AGC circuit).
[0032]
In FIG. 4, a 2-channel analog signal that has been subjected to predetermined signal processing such as known OB clamping processing and CDS processing based on the OB signal by the CDS circuit 12 is supplied to the gain correction unit 22, where the control unit 21 Are level-corrected based on a gain control signal so that the pilot signals Pch1 and Pch2 calculated based on the equation (1) are equal to each other, and then supplied to the ADC 23 to be converted into a digital signal.
[0033]
The digitized two-channel video signal, OB signal and pilot signal are supplied to the pilot signal level detection / smear detection unit 24, where the pilot signal level and smear component which are digital signals are detected, The detection result is supplied to the control unit 21. The digitized 2-channel video signal, OB signal, and pilot signal are input to the YC processing unit 18 via the pilot signal level detection / smear detection unit 24. When the smear detection signal is input, the control unit 21 excludes the pixel in which the smear is generated from the gain correction by the pilot signal in the gain correction unit 22 as in the first embodiment. Alternatively, when smear occurs, the correction calculation uses data before smear occurs.
[0034]
The present invention is not limited to the above embodiment. For example, pilot signal charge injection is performed several times or continuously for several H periods in the same field, and these injection potentials are added in units of pixels. By averaging, the influence of random noise of the injection potential may be reduced.
[0035]
In addition, when the charge is directly injected as a pilot signal of a predetermined level into the imaging signal transferred in the horizontal direction by the pilot injection units 7A and 7B shown in FIG. 5, the horizontal pilot signal is Since it is injected into the signal after the transfer of the horizontal transfer by the horizontal CCDs 6A and 6B and the vertical transfer by the vertical CCD, it is difficult to compare transfer efficiencies, but from the output amplifiers 8A and 8B of the solid-state imaging device 11 to the gain correction unit. Detection of gain differences up to 17 and 22 is possible.
[0036]
Therefore, the level difference detection accuracy between channels is further improved by using the pilot signals in both directions so that the gain difference is detected by the pilot signal in the horizontal direction and the transfer efficiency is compared by the vertical pilot signal. It is possible. In this case, the horizontal pilot signal is used for gain correction so that the pilot signal levels of the two channels are equal.
[0037]
In the above embodiment, the solid-state imaging device 11 has been described as having the same structure as that shown in FIG. 5, but the number of divisional imaging regions may be three or more. Further, the number of charge injections into the pilot injection unit 3 may be three or more, and the injection unit period may be between frames or a specific period instead of between fields.
[0038]
【The invention's effect】
As described above, according to the present invention, the detection accuracy of the pilot signal is improved by detecting the pilot signal having no variation in potential barrier based on the difference value between the pilot signal levels in the plurality of vertical directions. The level correction system between channels can be improved.
[0039]
In addition, according to the present invention, pilot signal charges are injected into signal charges that are vertically transferred at different potentials a plurality of times per unit time. Therefore, pilot signal charges are injected in time series between fields. As a result, pilot signal charge injection requires only a few H period, and the vertical transfer frequency can be prevented from being increased.
[0040]
Further, according to the present invention, the level of the pilot signal in the horizontal direction is detected for each channel, and is output in parallel from the plurality of divided imaging areas so that the detected horizontal pilot signal level of each channel is equal to each other. Since the level of the output signal of each channel is controlled, variation in the level of the output signal of each channel due to the gain difference between the channels can be corrected.
[0041]
Further, according to the present invention, by controlling the level of the output signal of each channel output in parallel from the plurality of divided imaging areas so that the detected horizontal pilot signal level of each channel is equal to each other, Variations in the level of the output signal of each channel due to the gain difference between channels can be corrected. The detection of the gain difference between channels is a horizontal pilot signal, and the transfer efficiency comparison between channels is the same for both the vertical pilot signal and the vertical pilot signal. By using the pilot signal in combination, the level difference detection accuracy between channels can be further improved.
[0042]
Further, according to the present invention, the vertical pilot signal on which the smear component is superimposed is not used for level control, or the pilot signal before the occurrence of smear is used for level control, so that malfunction due to the occurrence of smear can be prevented. Can do.
[Brief description of the drawings]
FIG. 1 is a block diagram of a first exemplary embodiment of the present invention.
FIG. 2 is a diagram showing a 2-channel output signal together with a vertical synchronizing signal in the embodiment of FIG. 1;
FIG. 3 is a diagram showing that the variation in potential barrier can be absorbed by carrying out pilot charge injection twice by changing the injected charge amount according to the embodiment of FIG. 1;
FIG. 4 is a block diagram of a second embodiment of the present invention.
FIG. 5 is a configuration diagram of an example of a solid-state imaging device with 2ch output.
FIG. 6 is a diagram showing that an output level difference occurs in the output between ch1 and ch2 due to a difference in transfer efficiency between horizontal and vertical CCDs and a gain variation in an output stage amplifier.
FIG. 7 is a diagram in which a constant charge is injected into a so-called dummy pixel of a vertical CCD located at the subsequent stage of image output, and as a result, a pilot (reference) signal (vertical) in units of pixels is output after data output.
8 is an example illustrating the vertical pilot signal of FIG. 7 in the horizontal direction.
[Explanation of symbols]
1A, 1B Division imaging area 2A, 2B, 4OB area 3 Vertical pilot injection part 5A, 5B Diagonal shift area 6A, 6B Horizontal CCD
7A, 7B Horizontal pilot injection section 8A, 8B Output amplifier 11 Solid-state imaging device 12 CDS circuit 13, 23 AD converter (ADC)
14 Timing generator (TG)
15, 21 Control unit 16, 24 Pilot signal level detection / smear detection unit 17, 22 Gain correction unit

Claims (3)

Imaging that obtains a video signal of a plurality of channels obtained by imaging a subject using a solid-state imaging device in which a vertical pilot injection unit is provided in each of the divided imaging areas obtained by dividing the imaging area into a plurality of parts in the horizontal direction. A device,
Injection means for injecting pilot signal charges into signal charges vertically transferred at different potentials per unit time by the vertical pilot injection section provided corresponding to each of the plurality of divided imaging areas. When,
The plurality of vertical pilot signal levels for each channel are output in parallel from the plurality of divided imaging areas and output from each channel including the video signal per unit time and the plurality of vertical pilot signals. Pilot signal level detection means for detecting;
A difference value between the plurality of vertical pilot signal levels detected for each channel by the pilot signal level detection unit is calculated for each channel, and the plurality of divisions are made so that the calculated difference values for each channel are equal to each other. An image pickup apparatus, comprising: level control means for controlling the level of an output signal of each channel output in parallel from the image pickup area, and outputting a video signal whose level is controlled by the level control means. A horizontal pilot injection section for injecting pilot signal charges is further provided for each channel in the horizontally transferred video signal charges of each channel, and the injection means uses the pilot signal charges by the horizontal pilot injection section. And the pilot signal level detection means further detects the level of the horizontal pilot signal injected by the horizontal pilot injection unit for each channel, and The level control means further has a function of controlling the level of the output signal of each channel output in parallel from the plurality of divided imaging areas so that the horizontal pilot signal levels detected for each channel are equal to each other. The imaging apparatus according to claim 1. Smear detecting means for detecting smear components for each channel from the output signals of each channel consisting of the video signal per unit time and the plurality of vertical pilot signals output in parallel from the plurality of divided imaging areas; And when the detection signal indicating smear occurrence is input from the smear detection means, the control means uses a pilot signal excluding the pilot signal in the smear occurrence area for the calculation of the difference value. The imaging device according to claim 1 or 2.

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