JPH03205975A - Still picture image pickup device - Google Patents

Abstract

PURPOSE:To accurately and speedily determine exposure with a simple mechanism by measuring the amount of exposure from the size of a photoelectric current to flow into an overflow drain. CONSTITUTION:An image pickup element 3 is equipped with the overflow drain and the photoelectric current to flow into the overflow drain is outputted to a photometric amplifier 4 and measured. The output reference value of the overflow drain photometric amplifier 4 is determined in advance so as to be suitable when the estimated value of shutter time is a certain initial value at the time of image pickup, and when a photometric operation is started, based on the output reference value according to the command of a system control circuit 8, an output signal is sent to a diaphragm driving circuit 5 so that the measured value of the photometric amplifier 4 can be the output reference value. Then, automatic iris control is executed to a diaphragm mechanism 2. Thus, the accurate exposure control can be executed at high response speed by the simple mechanism.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a still image imaging device using an image sensor equipped with an overflow drain, which is applied to electronic cameras, etc. This relates to the equipment R that performs control and the like.

[Prior Art] In a still image imaging device using a conventional image sensor, when performing photometry of exposure amount, for example, a half mirror is provided on the optical path that enters the image sensor to direct the incident light to the photometer. Either the scattered light of the so-called single-lens reflex finder screen is measured with a photometric element, or a photometric optical system separate from the optical system for imaging is installed and the photometric element is used to measure the light. No matter which method is used, a dedicated photometric element and related equipment are required for photometry.

In addition, as a method that does not require a separate photometric element, there is a method that uses the image sensor itself to measure light, for example, the image sensor is driven to extract a video output signal, and the size of the signal is used to adjust the exposure of the image to be appropriate. There is a method that performs so-called auto-iris control, which provides feedback control of the aperture.

On the other hand, as a method of obtaining exposure information from sources other than video output signals using an image sensor, it is possible to use the overflow drain of the image sensor for photometry. There is an example like No.-262367.

[Problems to be Solved by the Invention] In the conventional technology as described above, for example, when a dedicated photometry element and its related devices are provided separately from the image sensor, the overall structure of the image sensor becomes complicated, and Since it is necessary to maintain a sufficient correlation between the proper exposure of the photometry element and the imaging element, a highly accurate aperture adjustment mechanism and shutter adjustment device are required, which reduces the manufacturing process and cost of the imaging device. There was a serious problem.

In addition, an auto iris mechanism based on the video output signal from the image sensor is relatively simple and inexpensive as an aperture device of the image sensor, but it drives the image sensor during photometry and adjusts the exposure. Since control is performed, there is a problem in that a large amount of driving power is required.

In addition, since the video output signal from the image sensor itself is sampling data that is integrated over time, there is a limit to the operating speed of auto iris control.For example, when the power is turned on or when exposure conditions suddenly change. There was a problem that it took a long time for the aperture to stabilize.

The present invention has been developed in view of these conventional problems.
+- 4, /7″Izu Kozai Yu Roku?Gi tφJima Kimaro White / Hiroko: Juuma also aims to obtain a device that can perform quick exposure control.

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention provides an image sensor having an overflow train, a photometer for measuring a photocurrent flowing into the overflow train, and a photometer for measuring the photocurrent flowing into the overflow train. In a still image imaging device comprising an aperture for controlling the amount of incident light and a means for instructing the start of imaging, the output value of the photometry means provides appropriate exposure when the image sensor is exposed for a predetermined shutter time. an aperture control means that performs feedback control of the aperture so that the aperture becomes a reference value for the aperture, and an aperture controlled by the aperture control means;
an aperture fixing means for fixing the aperture immediately before the image pickup device starts an image capturing operation according to an instruction from the image capturing start instruction means; and after the aperture is fixed, a video signal captured by the shutter time is taken out from the image pickup device. ▼L. -l++Konobenrena 2 control means.

Further, the aperture position detection means detects the aperture position of at least one of the apertures, and the aperture control means sets the plurality of reference values corresponding to a plurality of predetermined shutter times to the aperture position detection means. The aperture is controlled so that the photometric output signal corresponds to the selected reference value, and the output control means performs image capture with a shutter time corresponding to the selected reference value. It may also be a still image imaging device that extracts a video signal.

In addition, an image signal amount detection means for detecting the magnitude of an output signal corresponding to at least a portion of the image plane from the video signal output, and an appropriate exposure in which a detection value of the image signal amount detection means is predetermined. shutter time correction means for correcting the shutter time so that when it is within the range, the shutter time remains unchanged; when it is not within the proper exposure range, the shutter time is corrected so that it falls within the proper exposure range; It may also be a still image capturing device that extracts a video signal captured by a camera.

[Function] Since the invention described in claim (1) of the present application is configured as described above, the exposure amount is measured from the magnitude of the photocurrent flowing into the overflow drain in the photometry means.
A dedicated photometric element is not required, and problems associated with correlation with the image sensor do not occur.

When capturing a still image, the optimum exposure corresponding to the shutter time is determined, but the optimum exposure when using this image sensor is, for example, the integral value of the exposure amount per unit time over the shutter time. Therefore, from this value, a reference value (for example, a measured value per unit time or a human power current value) of a photometric signal to be photometered by the overflow train of the image sensor is given.

The photometric signal (output value) of the photometric means of the present invention is not temporally sampled as described above, but is a value that is directly photometered using an overflow drain. The optimum exposure state can be obtained by feedback controlling the aperture so that it reaches the reference value.

Here, if an auto-iris mechanism with a simple mechanism is used as the aperture control means, the auto-iris mechanism can be controlled based on the above reference value with a signal corresponding to fluctuations in the output value of the photometry means, which is inexpensive. An aperture control means with a fast response time can be obtained.

Furthermore, when capturing still images with this imaging device,
In order to prevent malfunctions and unnecessary power consumption during the transition to imaging operation and during imaging, the aperture fixing means fixes the aperture or aperture mechanism immediately before the imaging element performs imaging operation, and the aperture value remains unchanged during imaging. Make it constant.

Since the invention described in claim (2) of the present application includes the aperture position detection means, for example, if the position can be detected with the aperture closed to the minimum, it is possible to prevent the aperture from being closed due to overexposure. In cases where proper exposure is not achieved even when the shutter is closed, select another reference value that corresponds to a shorter shutter time according to the exposure condition. 4
1- 'Self C sum 1 Human's prayer I★訃吃sweet κ Control the aperture to obtain proper exposure.

On the other hand, if the exposure is insufficient and proper exposure cannot be achieved even when the aperture is opened, select another reference value that matches the exposure condition, change to a longer shutter time, and capture the image with proper exposure.
It can also be linked with a flash device, etc., if necessary.

Furthermore, by performing detection at a plurality of positions, more precise control can be performed by determining a plurality of reference values from the correlation between the exposure amount and the shutter time.

The invention according to claim (3) of the present application includes the image signal detection means and the shutter time correction means, so that the exposure state of the image taken by the image signal detection means is directly detected,
If this is not within the appropriate exposure range, the shutter time correction means changes the shutter time, and performs correction to capture an image using the changed shutter time, thereby obtaining an image with appropriate exposure.

Here, in general, in still images, the subject is often located at the center of the image, so it is necessary to use the rf + tōrenmonosotanha↓LknafudashiwaPl swinglmorow extraction means in the center of the image. is preferable, but it may be possible to perform detection at different positions depending on the purpose of imaging.

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

FIG. 1 is a block diagram showing an embodiment of the present invention applied to an electronic camera.

A lens unit 1 of an electronic camera forms an image of a subject onto an image sensor 3 through an aperture mechanism 2 having an auto-iris function.

The aperture mechanism 2 is controlled by an aperture drive circuit 5,
Aperture position fixing means 11 is provided.

The image sensor 3 is equipped with an overflow train (not shown) and can perform an electronic shutter operation under the control of the image sensor drive circuit 7.

Further, the photocurrent entering the overflow train is output to the photometric amplifier 4 and measured.

When this electronic camera is powered on, power is supplied only to the photometering amplifier 4, aperture drive circuit 5, and system control circuit 8, and photometry of light incident on the lens unit 1 is started.

Here, the output reference value of the overflow drain photometering amplifier 4 is determined in advance so as to be appropriate when the expected shutter time during imaging is at a certain initial value, and when the photometry operation starts, the system control circuit 8 Based on the commanded output reference value, an output signal is sent to the diaphragm drive circuit 5 so that the measured value by the photometer 4 becomes the output reference value, and the diaphragm mechanism 2 is auto-iris controlled.

Further, the aperture drive circuit 5 is equipped with an open position detection circuit for the aperture mechanism 2, and when the aperture mechanism 2 becomes open {QW, an open signal is sent to the system control circuit 8, and the system control circuit 8 is the photometering amplifier 4 and the aperture drive circuit 5 in order to change the expected shutter time to a long time direction.
and performs the same auto iris operation.

Further, if the expected shutter time becomes longer than a certain set value, preparations are made to cause the flash device 13 to emit light.

When the release trigger switch 9 is pressed when taking an image with this electronic camera, the aperture drive circuit 5 operates the aperture position fixing means 11 in response to a command from the system control circuit 8, and the aperture position fixing means 11 is activated immediately before the image sensor drive circuit 7 is activated. Fix mechanism 2.

Then, power is turned on to the image sensor 3, its image sensor drive circuit 7, and the processing circuit 6 for the video output signal from the image sensor 3.
The image sensor 3 is driven at the shutter time determined during the auto-iris operation described above.

In this case, as described above, the flash unit 13 is activated to create an image as necessary, and the video output signal output from the image sensor 3 is converted into a predetermined signal format by the signal processing circuit 6, and then the recording unit +
2 and save it as a single image record.

Here, if an image sensor for a television camera is used as an image sensor as in a general electronic camera, the OHARA LOW TRAIN will have an electric field divided within the image plane as in Japanese Patent Application No. 6,326,2367. ＋τYoung pier~pushi＼t?
Ikoko: Photometry with the Naber Float Train is based on the average value of all image planes.

In this case, sudden changes in exposure conditions or other factors may cause short-term exposure defects or local exposure differences within the image plane, and such sudden changes may occur when capturing temporally continuous images. The average value for all image planes can also be used, but when shooting still images, judgments are made based on a single captured image, so the above method does not necessarily provide the preferred exposure for shooting still images. I can not say.

The electronic camera according to this embodiment includes a video level detection circuit 10 that processes the image output signal output from the image sensor 3 in the video signal processing circuit 6 and determines the magnitude of the image output signal before sending it to the recording section. is provided to judge the image output, and if poor exposure has occurred, the shutter time is corrected and the image is taken again.

The judgment of image output in the video level detection circuit 10 is made by receiving an image signal from the video signal processing circuit 6.
Mountain + canbun 2: Judgment is made by comparing with Todoroki Kasinaka 10 Noh's Ryogyo 7 Words, but in a still image, the desired subject is located in the center of the image, so the image plane It is preferable to determine the output of the image signal corresponding to the central part of the image.

FIG. 2 is a circuit diagram showing a specific example of the photometric amplifier 4 and the aperture drive circuit 5 of the overflow train,
The image sensor uses a general television image sensor,
The Oh-Half Train is an example that has only one power supply output.

The photometry status of this circuit is VCC 1, VCC 2, and VE.
Only E is energized, and VCC3 is set to OV. In the photometry amplifier 4, U1 is a MOS manually operated operational amplifier (hereinafter referred to as OP amplifier), and together with a resistor R1 constitutes a voltage conversion circuit.

Here, overflow train (hereinafter referred to as OFD) or OP
The OP amplifier U1 is connected to the negative power of the amplifier Ul, where the photocurrent is converted into a current voltage, or the OP amplifier U1 is supplied with power from VCCI through the action of the diode D1.At this time, since VCC3 is OV, the bias voltage is applied to the OFD. Since the dark current is within a negligible range, photometry of incident light can be performed.

Further, in the imaging state, a voltage is applied to VCC3. Since this voltage is normally higher than the voltage of VCC2, the op amp U1 has a diode DI (D2?)
Power is supplied from C3.

Then, the OFD has a resistor R due to the function of the OP amplifier U1.
2. The voltage applied to the positive input side by VRI and R3 is applied as a bias voltage, and exhibits the blooming suppression effect inherent to the OFD of the image sensor.

On the other hand, since a voltage higher than VCC2 is applied to VCC3 in the aperture drive circuit in the imaging state, in order to prevent the high voltage output from the photometering amplifier 4 from being applied to the subsequent stage of the aperture drive circuit 5, the voltage is A limiter 14 is provided.

A level shift amplifier is composed of an OP amplifier U3 and resistors R6 to R9, etc., which are provided after the voltage limiter 14, and the DC voltage is shifted by Vrefl or Vref2 selected by the analog switch SWI, and the required amplification degree is adjusted. is amplified to. Vref 1
The selection of and Vref2 corresponds to the selection of a fixed shutter time, and in this case, two shutter times are assumed.

To select the expected shutter time, it is possible to change the cane of this OP amplifier U3, but this will change the loop gain of the entire control system, so it is better to do this by shifting the DC voltage level as described above. And so.

Of course, the expected shutter times are not limited to two, and other methods may be used to select the expected shutter times.

Switching of the fixed shutter time is performed by a switching signal b from the system control circuit. Reference numeral 17 denotes a level shifter for adjusting the level of the switching signal b and the control signal of the analog switch SWI.

The output of OP amplifier U3 is analog switch SW2,
This aperture control circuit is composed of op amps U4, U5, R14 to R20, etc. The function of the analog switch SW2 will be described later. 16 is part of the electric circuit of a general auto iris mechanism, which consists of a rotor connected to the aperture blades, its driving coil, braking coil, etc. The aperture control circuit operates to open and close the aperture. The diaphragm becomes stable when the detected signal from the changed OP amplifier U3 becomes equal to Vref3.

In addition, regardless of whether Vrefl or Vref2 is selected, diode D3 to D6 are provided as voltage limiters to prevent the human power applied to the aperture control circuit from becoming asymmetrical with respect to Vref3, resulting in unstable control characteristics. ing.

The analog switch SW2 is connected to the output side of the OP amplifier U3 when the image sensor is in the photometry state, but if the aperture fixing signal a is input manually just before the image sensor enters the imaging state due to shutter operation, the OP amplifier is connected to the output side of the OP amplifier U3. It is connected to the output side of U4, and the aperture is tightly drawn.
ノ 1 Old groan It prevents the Tatsune current from flowing. 1
5 is a level shifter similar to the level shifter 17 for the control signal of SW2.

18 is an aperture open detection circuit, and when the aperture remains open, the OP amplifier U4 output remains at a high voltage due to Vref3 (actually, the maximum drive current of the OP amplifier and the impedance of the drive coil) The open state of the aperture position is detected using this fact.

The circuit consisting of the OP amplifier U6, R21, 22, C4, 5, etc. is a low-pass filter to prevent malfunction due to the transient response of the diaphragm drive circuit. Further, in this circuit, an open detection signal (low active) is output from C, but it is also necessary to detect an open state by continuing to output it for a certain period of time.

The open detection signal detected in this manner is input to the system control circuit and used to change the expected shutter time.

FIG. 3(8)(B) shows an example of an aperture fixing means. 26 is a drive device for the aperture mechanism, which corresponds to 16 in the circuit diagram shown in FIG. 27 is a link connected to the drive device 26, and two wooden pins 27a, b (7) are provided, and the pins 27a, b are connected to the opening 20a of the member 20,
20b allows reciprocating rotation within a limited range.

Reference numerals 21 and 22 denote two aperture blades each having an aperture opening, elongated holes 29a, 29b and cutout holes 24a, 24.
pins 19a and 1 that protrude from the member 19, respectively;
9b and the shaft of the member 25a as guides, and are connected to the pins 27a and 27b to drive the drive device 2.
6, the aperture is relatively moved in the opposite direction, and the aperture is determined by changing the size of the aperture of the aperture mechanism.

In the aperture mechanism driven as described above, the aperture blades 2
A magnet 25 is provided to mechanically fix the aperture position after changing and setting the aperture position. The shaft 25a of the magnet 25 has a collar 23b, and is normally pressed against the member 19 by a compression spring 30 (in the photometry state), but when the imaging operation starts, the magnet 25 is energized and fixed to the shaft 25a. Another spit 2
3a is moved against the pressing force by the spring 30,
The aperture blades 21 and 22 are supported between the member 19 and the flange 23a to fix the aperture. Reference numeral 24 denotes a cushioning material, such as felt, for uniformly pressing the aperture blades 21 and 22.

The embodiments described above are examples in which only the aperture open position detection is used, but in such an example, the expected shutter time setting is only allowed to change from short seconds to long seconds, and 1
Once the time is set to long seconds, it cannot be changed to short seconds.

Even in such a case, there is no problem when photographing a subject whose exposure changes little over time, but there is a problem when photographing a subject whose exposure changes rapidly.

In order to solve such problems, it is necessary to know the aperture position in more detail. As such an aperture position detection means, for example, a drive Hall element of an aperture mechanism, a magnetic resistance element, etc. are known.

FIG. 4 shows an example of detecting the aperture position using a Hall element.

Here, a Hall element 31 is provided in the aperture mechanism (auto iris device 16) driven by the aperture drive circuit 5,
The Hall voltage VH is amplified by the differential sense up 32,
The level determiner 33 uses this as a detection signal for the aperture position. Note that the Hall element 31 is driven with a constant current.

FIG. 5 is a diagram showing an example of an exposure control diagram in which the shutter time and the aperture are controlled by detecting the aperture position.

Here, the aperture position is determined by setting four types of threshold values, AO and A3, including wide open, and the shutter time is determined from 11 to T.
This figure is for the case where there are three types. In this figure, the shutter time becomes shorter as you move to the right on the X-axis, and the aperture closes as you move upward on the Y-axis. point! 9 E O ~ In this exposure control, for example, if the initial value of the assumed shutter time is T2, if the aperture position is stopped down from A3 by the aperture drive device (by performing auto iris operation), the exposure control will move on the equal exposure straight line E4. The controller moves to a control state where the assumed shutter time is T3, and then controls the aperture again from the state where the aperture position is A2 and the shutter time is T3.

On the other hand, if the aperture position opens to AO, which is the open state,
The controller moves to a control state in which the assumed shutter time T1 is on the equal exposure straight line El.

Here, for example, the equal exposure straight line E after the control state has moved
4, in the control when the assumed shutter time changes from T2 to T3, the return to the control of the assumed shutter time T2 from the control of the assumed shutter time open T3 is the same exposure straight line E.
The case where the aperture position is A2 on the equal exposure straight line E3 is not the case where the aperture position is A2 on the equal exposure straight line E3.

Similarly, in the control after the transition from shutter time T2 to T1, when the aperture position reaches A2, not when the aperture position A1 is reached on the equal exposure line El, the equal exposure line E
2 to control the fixed shutter time T2.

By providing hysteresis in the control characteristics in this way, the exposure state is prevented from becoming unstable. Further, by performing exposure control in combination with such an aperture control device (so-called auto iris), accurate exposure results can be obtained even if the aperture position at which the assumed shutter time is switched is inaccurate within the hysteresis range.

FIG. 6 is a circuit diagram showing an example of a video level detector.

The video signal (VIDEO) is input to the clamp circuit 34, and the DC component is fixed to the reference voltage Vref5. and,
The window circuit 35 cuts out only a part of the screen (usually including the center part) and sends signals corresponding to other parts to V.
Set it as ref5. To cut the screen, use the window signal WIN
This is done using the analog switch SW4.

An integrating circuit 36 is reset by an analog switch SW4 by a signal delayed by a delay circuit 38 from the vertical synchronizing pulse VD, and integrates the output video signal from the window circuit 35 to obtain the magnitude of the video signal. 37
is a sample and hold circuit which samples the video signal integrated by the integrating circuit 36 using the vertical synchronizing signal VD and outputs the DC't pressure as the video level of one screen. In the case of this circuit, it is necessary to reset the integrating circuit 36 after sufficient sampling and holding is performed.

If such an image signal detection means is used, for example, if an image that is not properly exposed is captured due to a sudden change in the exposure state, the above-mentioned detection means will detect the poor exposure, and furthermore, the detection means will detect the improper exposure in that exposure state. By correcting the shutter time and taking the image again, an image with proper exposure can be obtained.

The above describes the case where an image sensor for telephotography is used, but if an image sensor that has an overflow train divided into multiple parts within the image plane is used for still image capture, an overflow metering circuit will be installed for each. By mixing these values at an appropriate mixing ratio as the photometric output and performing aperture control as described above, accurate exposure suitable for still images can be obtained. No means necessary.

Also, by changing the mixing ratio depending on the output level of each photometric circuit, it is possible to change the exposure state to the optimum depending on the subject situation, as is commonly done with still cameras. I can do it.

FIG. 7 shows an example in which such a divided overflow drain is used to select the mixing ratio.

The outputs of the photometric amplifiers 4a to 4n corresponding to the photometric signals from each divided portion are connected to a resistive mixing circuit 39.
input to a to 39n and mixed. The resistance mixing circuits 39a to 39n have different mixing ratios, and represent the conditions of various objects that have been empirically classified into several categories.

On the other hand, the outputs of the photometric amplifiers 4a to 4n are AD converted to obtain control signals SEL for selecting the outputs from the mixing circuits 39a to 39m.

The control signal SEL is input to the selection circuit 40, and one of the mixing circuits 39a to 39n is selected, for example, and outputted to the aperture drive circuit 705 as a control signal.

By performing such control, the exposure state is controlled under the exposure conditions for the still image or under the exposure conditions desired by the photographer.

[Effects of the Invention] As described above, according to the still image capturing device according to the present invention,
It has the advantage of being able to quickly and accurately determine exposure using a simple mechanism.

Further, since the video signal processing circuit does not operate until the image is actually photographed, it is possible to configure a still image imaging device with low power consumption.

Furthermore, since the exposure control device is provided with a correction means, there is an advantage that even if poor exposure occurs, a still image with proper exposure can be obtained.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention applied to an electronic camera, and FIG. 2 is a circuit diagram showing a photometric amplifier and an aperture drive (auto iris) circuit using an overflow drain according to an embodiment of the present invention. FIG. 3 is an explanatory diagram showing an aperture mechanism and an aperture fixing means according to an example of the present invention;
Figure (A) shows the front view. (B) shows the plane, respectively, the fourth
The figure is an explanatory diagram showing an aperture position detection means and an aperture drive circuit according to an embodiment of the present invention, and FIG. 5 is an exposure control diagram in which the aperture position is detected and the shutter time and aperture are controlled in an embodiment of the present invention. A line diagram showing an example; FIG. 6 is a circuit diagram showing a detection circuit of an image signal detection means according to an embodiment of the present invention;
FIG. 7 is an explanatory diagram showing a circuit for mixing and selecting photometric output signals when an image sensor having a plurality of divided over-half-low drains is used as a photometric means according to an embodiment of the present invention. [Explanation of symbols of main parts]

Claims (3)

[Claims] (1) A still image comprising an imaging device with an overflow drain, a photometer for measuring the photocurrent flowing into the overflow drain, an aperture for controlling the amount of light incident on the imaging device, and a device for instructing the start of imaging. In the imaging device, an aperture control means that performs feedback control on the aperture so that the output value of the photometry means becomes a reference value for providing proper exposure when the image sensor is exposed for a predetermined shutter time; an aperture fixing means for fixing the aperture controlled by the aperture control means immediately before the imaging device starts an imaging operation according to an instruction from the imaging start instruction means; 1. A still image imaging device, comprising: output control means for extracting and outputting a captured video signal from the image sensor. (2) The still image imaging device according to claim (1), further comprising an aperture position detection means for detecting the position of at least one of the apertures, and wherein the aperture control means is configured to operate at a plurality of predetermined shutter times. The plurality of corresponding reference values are switched and selected according to the output of the aperture position detection means, and the aperture is controlled so that the photometric output signal corresponds to the selected reference value, and the output control means A still image imaging device, wherein the still image imaging device extracts a video signal captured at a shutter time corresponding to the selected reference value. (3) In the still image imaging device according to claim (1) or (2), image signal amount detection means detects, from the video signal output, the magnitude of the output signal corresponding to at least a portion of the image plane. and a shutter that corrects the shutter time so that when the detected value of the image signal amount detection means is within a predetermined appropriate exposure range, the shutter time remains unchanged, and when it is not within the appropriate exposure range, the shutter time is within the appropriate exposure range. A still image imaging device, comprising: a time correction unit, wherein the output control unit extracts a video signal captured using the corrected shutter time.