JPH04189078A - Image pickup device - Google Patents

Abstract

PURPOSE:To obtain a picture with high accuracy by eliminating a high amplitude component in excess of a prescribed value of an image pickup signal and synthesizing a signal with less exposure from the image pickup signals so as to compress the high amplitude component. CONSTITUTION:When a luminous quantity to a sensor 103 is strong, a signal level of a signal S1 is saturated at a prescribed value. Then a black reference portion of the signal S1 is clamped by a clamp circuit 221 and the saturated part is clipped by a white clip WC circuit 222 and a high amplitude portion is eliminated. Moreover, a signal S2 of the sensor 103 is synthesized with the output signal of the circuit 222 via a sample-and-hold switch 216 by using a signal with less exposure than the signal S1 and the result is compressed by a KNEE circuit 231. Since the high amplitude component in excess of a prescribed value of the image pickup signal with large exposure is eliminated, noise is eliminated and a picture with high picture quality is obtained.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an imaging device, and particularly to an imaging device having a substantially wide dynamic range.

[Prior Art] Imaging devices are widely used as video camera units such as camera-integrated VTRs and still video cameras. Video cameras that use image pickup tubes or solid-state image sensors have a narrower dynamic range than traditional silver-halide photographic systems, and as a result, when backlit, etc., whites and darks are crushed (a common term for areas with extremely high or low brightness levels). ) etc. occur.

With conventional video cameras, in such cases, the aperture can be opened by about two stops either manually or by operating the backlight compensation button.
I was adjusting the light intensity.

However, when such backlight correction is appropriately performed, even if the main subject has an appropriate exposure amount, overexposure may occur in the background, resulting in a screen where only the background is white. In other words, simply adjusting the light amount so that the exposure amount of the main subject is appropriate as in conventional devices does not solve the problem of the narrow dynamic range of the imaging device.

One way to solve this problem is to expand the dynamic range by performing two exposures, for example. This method converts the saturated pixel signals of a screen imaged with a normal exposure time of 1760 seconds into a high-speed shutter operation (for example, 1/10
00 seconds). With this method, the exposure time differs by about 16 times, so the dynamic range can also be expanded by about 16 times.

As a known example of expanding the dynamic range by such multiple exposures, for example, Japanese Patent Laid-Open No. 1-1761
No. 73, Japanese Unexamined Patent Publication No. 1-204579, etc.

The former publication describes a conventional signal processing method, in which the first exposure signal is temporarily stored in a memory device, and when reading the next exposure signal, the signal of the memory device is are simultaneously read out and a signal processing circuit forms a composite signal with an expanded dynamic range.

In the latter publication, as shown in FIG. 9, two imaging signals with different exposure times are passed through respective signal processing circuits,
A composite signal is formed by adding them at a ratio of 1:1.

[Problems to be Solved by the Invention] However, with the conventional simple signal replacement processing method or addition method of two imaging signals, it is difficult to reproduce a photographed subject image with high image quality. In contrast to natural subjects with high gradations, display devices or printing paper have low gradations, and high-quality images can be obtained by performing optimal signal processing on such low gradation reproduction means.

[Means for Solving the Problems] The imaging device of the first invention of the present application is an imaging device that combines imaging signals of different numbers of exposure amounts to form one composite imaging signal. a clipping means for removing a high amplitude component exceeding a certain value; and a signal for adding a signal voltage of another imaging signal having a smaller exposure amount than the one imaging signal to the clipping voltage of the one imaging signal clipped by the clipping means. The present invention is characterized in that it has a combining means, and a knee means for compressing a high amplitude portion of the signal combined by the signal combining means.

An imaging device according to a second invention of the present application is an imaging device that combines a plurality of imaging signals having different exposure amounts to form one composite imaging signal, and in which a plurality of imaging signals having different exposure amounts are combined, the imaging device has a smaller exposure amount among the plurality of imaging signals having different exposure amounts. An amplitude control means for controlling the amplitude of an imaging signal according to a signal level of the imaging signal; an imaging signal whose amplitude is controlled by the amplitude control means; and an imaging signal having a larger exposure amount than the imaging signal having a smaller exposure amount. signal synthesis means for synthesizing the signals;
A knee means for compressing a high amplitude portion of the signal synthesized by the signal synthesizing means.

An imaging device according to a third aspect of the present invention comprises: a signal synthesizing means for synthesizing a plurality of image signals having different exposure amounts to form one composite image signal; and a high amplitude portion of the signal synthesized by the signal synthesizing means. It is characterized by comprising a knee means for compressing, and a control means for controlling knee characteristics of the knee means according to a signal level of an image signal having a smaller exposure amount among the plurality of image signals having different exposure amounts. .

The imaging device of the fourth invention of the present application clamps all the imaging signals of multiple locations having different exposure amounts or other imaging signals except for one imaging location to a predetermined potential so as to be able to continuously synthesize them. a clamping means; and a signal synthesizing means for synthesizing the plurality of imaging signals having different exposure amounts at the predetermined II level to form one composite imaging signal.

A knee means for compressing a high amplitude portion of the signal synthesized by the signal synthesizing means.

[Operation] The first invention of the present application removes noise contained in the high amplitude component of the first imaging signal (imaging signal with a large exposure amount) by removing the high amplitude component exceeding a certain value. By adding the signal voltage of another image signal with a small exposure amount to the clip voltage of the image signal from which the noise has been removed and compressing the high amplitude part of the combined signal, the high amplitude part from which the noise has been removed is This allows you to obtain high-quality images.

The second invention of the present application controls the amplitude of an imaging signal with a small exposure amount according to the signal level of the imaging signal, and combines the amplitude-controlled imaging signal with an imaging signal with a large exposure amount to increase the signal level. By compressing the amplitude part, a dynamic range corresponding to the signal level of the imaging signal with a small exposure amount is obtained.

The third invention of the present application provides that when a plurality of imaging signals having different exposure amounts are combined to form one composite imaging signal and a high amplitude portion of this composite imaging signal is compressed, the plurality of imaging signals having different exposure amounts are combined. By controlling the compression level (-characteristic) according to the signal level of the imaging signal with a small exposure amount, a composite imaging signal corresponding to the signal level of the imaging signal with a small exposure amount is obtained.

The fourth invention of the present application is to clamp all the imaging signals of a plurality of imaging signals having different exposure amounts or other imaging signals except for one imaging signal to a predetermined potential so as to be able to continuously synthesize the plurality of imaging signals, and to By combining multiple imaging signals to form one composite imaging signal and compressing the high amplitude part of the composite signal, it is possible to obtain a single composite imaging signal that is continuously synthesized in an analog manner. be.

[Example] Embodiments of the present invention will be described in detail below with reference to the drawings.

First, the imaging element used in the imaging device of the present invention will be explained.

FIG. 6 is a schematic configuration diagram of one configuration example of an image sensor used in the present invention.

In FIG. 6, IO is an image area, 2° is a storage area, 30 is a drain, and 4o and 50 are horizontal transfer CCDs.

The image area 10 includes a photodiode 11 which is a light receiving element, and a vertical transfer C for temporarily holding charges photoelectrically converted by the photodiode 11 after the photoelectric conversion is completed.
OD (vertical registers) 12 are arranged alternately in a plurality of columns. The vertical transfer CCD l-'2 is shielded from light, and the photocharges held there are transferred to the vertical transfer pulse φ.
1ml is transferred to the storage area 2o by CCD. A drain 30 provided above the image area 10 is an electrode for quickly removing unnecessary charges generated in the image area 10.

The storage area 20 is entirely shielded from light, and there is a vertical transfer C for storing photocharges from the image area 10.
It has a configuration in which CDs (vertical registers) 21 are arranged. A horizontal transfer CCD 40 is provided between the image area 1O and the storage area 20, and a horizontal transfer CCD 50 is provided below the storage area 20, and the photocharges from the vertical transfer CCDs 12 and 21 are transferred to the output amplifier at high speed. Forward.

Hereinafter, the operation of the image sensor will be explained using FIG. 7.

FIG. 7 is a drive timing chart for explaining the operation of the image sensor.

The photodiode 11 is exposed to light (photoelectric conversion) twice in one field period. That is, in FIG. 2, T is the first exposure period and T is the second exposure period. Note that the first exposure period T is longer than the second exposure period T2.

First, as shown in FIG. 7, when the exposure of the first exposure period T approaches the end, the vertical transfer CCD
D12 is a transfer pulse φ, I) in the opposite direction to the normal mold part transfer.
(Pulse A in the figure) is applied.

Next, a transfer pulse φl+n+ (pulse B in the figure) is applied to transfer the photocharge on the photodiode 11 to the vertical transfer CCD.
12, and then transfer pulse φ1lnl (in the figure,
pulse C) and transfer pulse φ,i1 (pulse C' in the figure)
) is applied to transfer the photocharges of the vertical transfer CCD 12 to the storage area 20 at high speed. Note that in the photodiode 11, when the photocharge is transferred, the second exposure period T begins.

Next, a transfer pulse φ1 (pulse D in the figure) is applied to transfer the photoelectric charges photoelectrically converted to the vertical transfer CCD 12 during the second exposure period T2.

At this point, the vertical transfer CCD 21 has accumulated signals from the first exposure (exposure during the first exposure period T).
Further, signals from the second exposure (exposure during the second exposure period T) are accumulated in the vertical transfer CCD 12.

When the vertical blanking period ends, a transfer pulse φ, is transmitted during each horizontal blanking period (T,) within the video period. (Pulse E in the figure) and transfer pulse φIlr+
1 (pulse E' in the figure) is applied, and the vertical transfer CCD
12. The photocharge of the vertical transfer CCD 21 is transferred to the horizontal transfer CCD
40, transferred to the horizontal transfer CCD 50.

Then, during the effective period of horizontal scanning, this photocharge is sent to the outside by a signal S via an output amplifier by a horizontal transfer pulse φ11.
, (signal resulting from the first exposure), and signal S, (signal resulting from the second exposure).

In the image sensor described above, it is possible to simultaneously output the signal Sl from the first exposure and eight signals from the second exposure.

Hereinafter, an imaging apparatus of the present invention using the above-described imaging device will be described.

FIG. 1 is a block diagram of the overall configuration of a video device that is a first embodiment of the imaging device of the present invention using the above-mentioned imaging device.

FIG. 2 is a timing chart of sample and hold pulses used to synthesize the signals S, , S, obtained during the first exposure and the second exposure.

FIG. 3 is a characteristic diagram showing signal levels of each circuit component of the camera signal processing system of the video apparatus.

The configuration of the video device is as shown in FIG.
0, a camera signal processing system 200, and a recording system 300.

In the optical system 100 , the amount of object light incident from the lens 101 is limited by the iris 102 and is focused on the sensor 103 . The sensor 103 is the sensor drive circuit 1
05, the iris 102 is connected to the iris drive circuit 1.
06.

The signals S, , S, from the sensor 103 are subjected to signal processing for expanding the dynamic range, general camera signal processing, etc. in a camera signal processing system 200. Here, the 5-sensor 103 is the image sensor shown in FIG. 6, the signal S1 is a signal from the first exposure (long exposure), and the signal S2 is a signal from the second exposure (short exposure).

Further, here, the exposure amount is controlled by the length of the exposure period, but in the present invention, the exposure amount can also be controlled by controlling an iris, using a flash, or the like.

Hereinafter, the camera signal processing system 20 will be explained using FIGS. 2 and 3.
The signal processing operation of 0 will be explained.

In FIG. 1, a and b are the output signals (signals S+ and Sa) of the sensor 103, respectively, and a' is the clamp circuit 221.
a'' is the output signal of the white clip circuit CW-C circuit) 222, b and b' are the output signals of the amplifier 213 (this output signal is the output signal of the sensor 103).
c, e' are the output signals of the hold capacitor C8, d, d' are the knee (KNEE) circuit 23
1 output signal. In Figure 3, a, a'.

a-, b, b', c, c', d, and d' are curves or straight lines representing the light amount-signal level characteristics of each output signal.

First, signal processing of the signal SI from the sensor 103 will be explained.

Signal S from sensor 103 (output signal a) is sensor 1
When the amount of light to 03 is strong, a certain signal level (in Figure 3, V
, , ), and the characteristic becomes as shown by curve a in FIG. 3. Signal S, (output signal a) clamps the black reference part to circuit 2.
It is clamped at 21. Vc in FIG. 3 indicates a clamp voltage.

The portion of the signal S, (output signal a') clamped to the voltage ■, whose signal level is higher than the signal level Vtn+ + Vc is clipped by the white clip circuit 222, resulting in a characteristic as shown in curve a1 in FIG. Become. White clipping is performed because when the sensor is saturated, variations due to the sensor manufacturing process become large.

Moreover, the signal S, (output signal a) from the sensor 103 is
In order to detect the presence or absence of saturation, the saturation detection level in this embodiment, which is input to the level detector 223, is set to a potential V t fi l that is smaller than the white clip level VtTl++6 by the potential VC.

The level detector 223 is connected to a control circuit 225, and the control circuit 225 outputs sample and hold pulses SH,,SH, for controlling sample and hold switches 216 and 226, which will be described later, based on the output signal of the level detector 223. The control circuit 225 also controls the level distribution of the signal Sl examined by the level detectors 223 and 224 (the detection level of the level detector 223 is at the potential ■1).
0, the detection level of the level detector 224 is the potential V th*
), and controls the iris drive circuit 106 to optimally set the iris 102.

Next, signal processing of the signal S2 from the sensor 103 will be explained.

Signal S has a signal level of approximately 1/16 compared to signal S1.

Here, if the gain of the amplifier 213 is 1, the signal S2
(Output signal b) passes through the amplifier 213 and is input as an output signal to the clamp circuit 214 with the signal level unchanged.

The clamp potential vr' at this time is set as follows.

The signal S during long exposure (curve a in FIG. 3) is judged to be saturated at a signal level of V th+ or higher by the level detector 223 described above, and white clipping is performed after clamping (in FIG. 3, curve a″), hence the signal S, (
When the signal level of the output signal a'') is equal to or higher than V th+ + V c, it is necessary to replace it with the signal S2 at the time of short exposure.

The signal S corresponding to the signal levels ■, □ of the signal Sl (output signal a), and the signal levels ■1, 1 of the (output signal b) are as follows.

Here, it is necessary to add a signal of signal S, (line b in Figure 3), which is higher than V LSI, to the part of signal S, (curve a- in Figure 3), which has a signal level of V th+ + V c or higher. There is. Therefore, the clamp potential ■ of the clamp circuit 214. ′
From the clamp potential of the clamp circuit 221, V tr
The signal that has passed through the clamp circuit 214 is input to the sample-and-hold switch 216, which only needs to be increased by +1 ""' V Lll+.

The sample-and-hold switch 216 performs a sample-and-hold operation when the signal S1 is saturated due to the sample-and-hold switch 5) (1) of the control circuit 225.

Therefore, when the signal S1 is not saturated, the hold capacitors C and I sample and hold the signal s, the output of the cw-c circuit 222, and the curve a'-) in FIG.
1 is saturated, the signal S2 (output of the clamp circuit 214) is sampled and held, and the two image signals are synthesized (curve C in FIG. 3). The high signal level of this signal is suppressed by a knee (NEE) circuit 231.

In this embodiment, the signal level is suppressed 174 times at a high signal level. The signal d that has been subjected to knee processing is subjected to γ processing, etc. in the subsequent camera processing circuit 232.
Normal camera signal processing is performed.

The output signal of the camera process circuit 232 is transmitted to the recording device 301.
and recorded on videotape or floppy disk.

Next, level detectors 210, 211. The control circuit 212, amplifier 213, and clamp potential control circuit 215 will be explained.

A case will be described in which the incident light on the sensor 103 is not very strong and the dynamic range does not need to be expanded by 16 times as in the previously described embodiment, but may be expanded by, for example, 8 times.

In the level detector 210, the signal level Vtll'
(→Vth, /16) to check the signal distribution of the signal S2, and the level detector 211 detects the signal levels v, h, '
(=■.2/16) to check the signal distribution.

When the detection frequency of the level detector 210 is large, the exposure time T2 is made small, that is, even smaller than 1/1000 second. If the detection frequency of the level detector 210 is small, the dynamic range may be slightly narrowed, so the control circuit 212 sets the gain of the amplifier 2I3 to twice.

The twice amplified signal b' is input to the clamp circuit 214, and the clamp potential vC' is set to
The clamp output becomes signal C'. When this signal C' is passed through the knee circuit 231, a signal d' can be obtained.

Therefore, the knee characteristics are optimally suppressed according to the intensity of the incident light,
The signal input to the camera process circuit 232 can be optimally set.

FIG. 4 is a partial block diagram showing the configuration of a second embodiment of the imaging device of the present invention.

In this embodiment, the signal level to the camera process circuit 232 is adjusted by the knee circuit 231 instead of the amplifier 213.

The knee characteristic of the knee circuit 231 is set to 174 by the control circuit 212.
It is controlled to be 1x or 172x.

FIG. 5 is a partial block diagram showing the configuration of a third embodiment of the imaging apparatus of the present invention.

In this embodiment, after the sensor signal S is clamped by a clamp circuit 221, a white clip circuit (W-C circuit) 22
White clip with 2, knee (KNEE) circuit 222
′ compresses high amplitude components. Thereafter, it is combined with the sensor signal S2 which has undergone signal processing in the same manner as in the first embodiment to obtain a composite signal.

[Effect of the invention] As explained in detail above, according to the first invention of the present application,
By removing the high amplitude component exceeding a certain value of the first imaging signal (the imaging signal with a large amount of n light), the noise contained in the high amplitude component of the first imaging signal is removed, and the other imaging signal with a small amount of n light is removed. By adding the signal voltage of the signal to the clipping voltage of the image pickup signal from which noise has been removed and compressing the high amplitude portion of the combined signal, a high-quality image from which noise has been removed can be obtained.

According to the second invention of the present application, the amplitude of an imaging signal with a small exposure amount is controlled according to the signal level of the imaging signal (for example, the signal with an exposure time of 1/1000 seconds is doubled), and the amplitude is controlled. By combining the imaging signal and the imaging signal with a large exposure amount (for example, exposure time 1/60 seconds) and compressing the high amplitude part of the signal, a dynamic range corresponding to the signal level of the imaging signal with a small exposure amount is obtained. I can do things.

According to the third invention of the present application, when a plurality of imaging signals with different exposure amounts are combined to form one composite imaging signal and a high amplitude portion of this composite imaging signal is compressed, multiple imaging signals with different exposure amounts are Among the signals, by controlling the compression level (characteristic) according to the signal level of the imaging signal with a small exposure amount, it is possible to obtain a composite imaging signal corresponding to the signal level of the imaging signal with a small exposure amount (for example, The knee characteristics can be controlled from 174 times to 172 times).

Further, according to the second and third inventions of the present application, even if images are captured by changing the short exposure time with respect to the long chain light time, the imaging signal level during the short exposure is optimally set, and the imaging during the long exposure is performed. Since it can be combined with the signal, the dynamic range expansion effect can be maximized.

According to the fourth invention of the present application, the exposure amount is different? ! All the imaging signals of the number of imaging signals or the other imaging signals excluding the imaging signal of - are clamped to a predetermined potential so that they can be continuously synthesized, and a plurality of imaging signals with different exposure amounts are synthesized to form a single image signal. By forming two composite image signals and compressing the high amplitude portions of the combined signals, it is possible to obtain one composite image signal that is continuously synthesized in an analog manner.

[Brief explanation of the drawing]

FIG. 1 is a block diagram of the overall configuration of a video device that is a first embodiment of the imaging device of the present invention. FIG. 2 is a timing chart of sample and hold pulses used to synthesize the signals S, S2 obtained during the first exposure and the second exposure. FIG. 3 is a characteristic diagram showing signal levels of each circuit component of the camera signal processing system of the video apparatus. FIG. 4 is a partial block diagram showing the configuration of a second embodiment of the imaging device of the present invention. FIG. 5 is a partial block diagram showing the configuration of a third embodiment of the imaging apparatus of the present invention. FIG. 6 is a schematic configuration diagram of one configuration example of an image sensor used in the present invention. FIG. 7 is a drive timing chart for explaining the operation of the image sensor. FIGS. 8 and 9 are explanatory diagrams of a signal processing method of a conventional imaging device. 10: Image area, 1 photodiode, 12:
Vertical transfer CCD (vertical register), 20: Storage area, 21: Vertical transfer C0D (vertical register), 30 Nidrain, 40.50 + horizontal transfer CCD, 100: Optical system, 101: Lens, 102: Firis, 103: Sensor, 105; sensor drive circuit, 106:
iris drive circuit, 200: camera signal processing system, 210, 211 two-level detector, 212: control circuit, 213: amplifier, 214: clamp circuit, 215: clamp potential control circuit, 216:
Sample hold switch, 221: Clamp circuit, 222: White clip circuit CW-C circuit), 223, 224 Two-level detector, 22
5: control circuit, 226: sample hold switch, 222': knee (KNEE) circuit 231: knee (KNEE) circuit, 232: camera process circuit, 300: recording system, 30 is recording device, CH two hold capacitor, SH, , SH,: Sample hold pulse. Agent Patent Attorney Seki Taira Yamashita Figure 2, Figure 3, Figure 7, Figure 5, Figure 6, Figure 8, Figure 9

Claims (5)

[Claims] (1) In an imaging device that combines a plurality of imaging signals with different exposure amounts to form one composite imaging signal, a clipping means for removing a high amplitude component exceeding a certain value of one imaging signal; a signal synthesizing means for adding a signal voltage of another imaging signal having a smaller exposure amount than the imaging signal to the clip voltage of the one imaging signal clipped by the clipping means; and a high amplitude portion of the signal synthesized by the signal synthesizing means. An imaging device comprising: knee means for compressing; (2) In an imaging device that combines multiple imaging signals with different exposure amounts to form one composite imaging signal, the amplitude of the imaging signal with a smaller exposure amount among the multiple imaging signals with different exposure amounts is An amplitude control means for controlling the image signal according to the signal level of the image signal; and a signal synthesis means for synthesizing the image signal whose amplitude is controlled by the amplitude control means and the image signal having a larger exposure amount than the image signal having a smaller exposure amount. and knee means for compressing a high amplitude portion of the signal synthesized by the signal synthesis means. (3) a signal synthesizing means for synthesizing a plurality of imaging signals having different exposure amounts to form one composite imaging signal; and a knee means for compressing a high amplitude portion of the signal synthesized by the signal synthesizing means; An imaging apparatus comprising: a control means for controlling a knee characteristic of the knee means according to a signal level of an imaging signal having a smaller exposure amount among a plurality of imaging signals having different exposure amounts. (4) Clamping means for clamping all the imaging signals of a plurality of imaging signals having different exposure amounts or other imaging signals except for one imaging signal to a predetermined potential so as to be able to continuously synthesize them; A signal synthesizing means for synthesizing a plurality of imaging signals at the predetermined potential to form one composite imaging signal; and a knee means for compressing a high amplitude portion of the signal synthesized by the signal synthesizing means. An imaging device characterized by: (5) In the imaging device according to claim 1, the output signal of the clipping means is inputted to the signal synthesizing means through the knee circuit;
An imaging device characterized in that a signal of another imaging signal having a smaller exposure amount than the first imaging signal is added to the signal whose high amplitude portion is compressed by the knee circuit.