JP2003101871A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup device capable of performing photographing with more appropriate exposure while maintaining a cost low. SOLUTION: Since pixels 50b and 50c of a second group are arranged in a plurality of areas (photographing image center and periphery) and output signals from the pixels 50b and 50c of the second group are obtained for each area and used as data for photometry by performing prescribed weighting, by performing the photometry for each of a plurality of the areas on a photographing image, the more appropriate exposure is performed even for an object whose luminance distribution is extremely biased. Also, since the output signals from the pixels 50b and 50c of the second group are weighted for each area, the exposure of a center area where the possibility of presence of a main object is high is appropriately performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photographing device, and more particularly, to photographing a still image of an electronic still camera or the like in which an exposure amount can be controlled by utilizing an electronic shutter function and a light detection function of a solid-state image pickup device. Regarding the device.

[0002]

2. Description of the Related Art With the development of electronic technology in recent years, electronic still cameras such as a digital still camera capable of converting an optical image into image data and storing the image data have been developed and put on the market. By the way, in a general electronic still camera, when the release switch is half-pressed, photometry is started using the image sensor, and when fully pressed, shooting is performed at a shutter speed and an aperture diameter based on the photometry result. There is.

[0003]

However, in a scene in which the subject brightness changes, the field brightness when the release switch is half-pressed and the field brightness when the release switch is fully pressed. They can be different, resulting in improper exposure.

On the other hand, if a separate photometric element is provided, the photometric operation can be performed during the photoelectric conversion by the image pickup element at the time of release, so that the shutter speed can be adjusted according to the change in the field brightness. It can be speeded up or slowed down so that proper exposure can be achieved. However, if the photometric element is separately provided, the cost of the electronic still camera increases and the size of the electronic still camera increases.

In response to this problem, the CMOS type image pickup device having a structure different from that of the CCD has a characteristic that it is possible to take out only the electric charge accumulated in a specific pixel. For example, there is an attempt to extract the electric charge accumulated in the central pixel of the pixels arranged two-dimensionally and use it as photometric data. However, for example, if photometry is performed using only the central pixel, there is a problem that proper exposure cannot be obtained when photographing a subject having an extreme luminance distribution.

The present invention has been made in view of the above problems of the prior art, and an object of the present invention is to provide a photographing apparatus capable of photographing with a more appropriate exposure while keeping the cost low. To do.

[0007]

An image pickup apparatus according to a first aspect of the present invention has an image pickup device in which a plurality of pixels are arranged two-dimensionally,
In a photographing device for photographing a subject, the image pickup device includes a first group of pixels used for converting the subject into image data and a second group of pixels used for performing photometry. The second group of pixels is arranged in each of a plurality of regions, and has a control unit that controls the exposure time based on the output signal of each region from the second group of pixels. By performing photometry for each of the plurality of regions above, even a subject whose brightness distribution is extremely biased can perform more appropriate exposure than when performing photometry for a single region.

According to a second aspect of the present invention, there is provided an image pickup device for photographing a subject, wherein the image pickup device has a plurality of pixels arranged two-dimensionally. The image pickup device converts the subject into image data. A first group of pixels used to
And a second group of pixels used for performing photometry, the second group of pixels being arranged in each of a plurality of regions, and the output from the second group of pixels in each region. An output amplifier that amplifies the signal is provided for each area,
Since the photometric data is obtained based on the output signals from the pixels of the second group, by performing photometry for each of a plurality of areas on the photographic screen, it is possible to obtain a more appropriate value even for a subject whose brightness distribution is extremely biased. Can be exposed. Further, since the output signals from the pixels of the second group are amplified for each region by the output amplifier, for example, the output signals can be processed for each region, so that more advanced exposure control can be performed.

According to a third aspect of the present invention, there is provided an image pickup device in which a plurality of pixels are two-dimensionally arranged, and the image pickup device is for taking an image of a subject. The image pickup device converts the subject into image data. A first group of pixels used to
A second group of pixels used for performing photometry, the second group of pixels are arranged in each of a plurality of regions, and the output signals from the second group of pixels are Since it is used as data for photometry by performing a predetermined weighting for each area, by performing photometry for each of multiple areas on the shooting screen, even for subjects whose brightness distribution is extremely biased,
More appropriate exposure can be performed. Further, since the output signals from the pixels of the second group are weighted for each area, it is possible to properly expose the area where the main subject is likely to exist.

It is preferable that the plurality of areas include a central area corresponding to the center of the photographing screen and a peripheral area corresponding to the periphery thereof. This is because the main subject is often located in the center of the shooting screen.

Further, the second portion corresponding to the central region
The output signals of the pixels in the group are preferably weighted more than the output signals corresponding to the peripheral region. This is to properly expose the main subject.

If the image data corresponding to the position of the pixel of the second group is obtained based on the image data of the pixel of the first group located around the pixel of the second group, it is obtained by photographing. Image quality can be maintained high.

Further, if the pixels of the second group are a part of the pixels of the first group, that is, the image data can be obtained from the pixels of the second group, a higher quality image can be formed. You can

Further, if the image pickup device has a judging section for judging whether the charge accumulated in the pixels of the second group exceeds the threshold value, the image pickup device can be constructed by one chip.
The degree of freedom in design is improved. The threshold value at this time is preferably settable from the outside.

Further, it is preferable that the image pickup device has an output terminal for outputting the electric charge accumulated in the pixels of the second group to the outside.

Further, the pixels of the second group are 3 in one area.
If there are two or more, the value of the charge accumulated in one pixel is the average of the charges accumulated in other pixels,
When the value is higher than a predetermined value, the charge of the pixel having a high charge value is excluded, and when compared with the threshold value, the high-brightness data of a light-emitting subject such as a light is excluded,
Since the exposure control can be performed, more accurate exposure control can be performed.

Further, it is preferable that the charges accumulated in the pixels of the second group are discharged at the same time because the exposure control can be performed quickly and the control can be simplified.

Further, when the charges accumulated in the pixels of the second group are discharged in response to the clock, the number of wirings for discharging can be reduced and the cost can be reduced.

Further, it is preferable that the amount of electric charge accumulated in the pixels of the second group can be detected without being discharged, because the subject brightness can be detected in real time.

Further, by sequentially applying a trigger signal to the pixels of the second group, and discharging the accumulated charges in the order in which the trigger signal is applied, the charges can be discharged in an arbitrary order.

The second group of pixels preferably has at least two charge storage portions.

Further, when the charges accumulated in the pixels of the second group are sequentially discharged from the pixels on the center side corresponding to the photographing screen, with respect to the main subject often located at the center,
Exposure control can be performed quickly.

In the image pickup device according to the present invention, the pixels of the second group are turned on at the same time when the output signals (charges accumulated) are being discharged, that is, when the pixel image width is the number of pixels.
It is conceivable that the output is taken out by keeping (discharged state) or by accessing at high speed periodically. When there are a plurality of pixels in the second group, it is advisable to switch the pixels at high speed while scanning.

In addition to using a part of the pixels arranged two-dimensionally, it is conceivable to provide a second group of pixels dedicated to acquisition of exposure control data in the image pickup section. For example, if a light receiving element is provided between pixels, it will have less effect on the image quality,
There is a problem that the wiring area increases. It is also conceivable to arrange pixels or light-receiving elements around the image pickup section. Further, it is conceivable to provide light-receiving elements arranged in a line in place of a single pixel. The charges accumulated in the pixels of the second group are
It may be considered to separate the exposure control data and the image data. At this time, the output of the pixel is smaller than the output of the pixel for extracting the image data, but amplification of this has an advantage that deterioration of the image quality is smaller than that obtained by interpolating from surrounding pixels.

Further, a pixel having a device structure capable of nondestructive read (that is, a pixel capable of obtaining the accumulated charge amount without discharging the charge) is provided for obtaining the exposure control data. The signals of the pixels of the second group can also be used as image data. In this case, for example, it is preferable to compare the data read before the flash emission with the data read after the flash emission and terminate the exposure when the preset photometric level is exceeded.

Further, when a part of the pixels of the first group is used as the pixels of the second group, when a specific pixel of the first group is fixedly used, and when an arbitrary pixel of the first group is selected. Therefore, it may be adaptively used as a pixel of the second group. When fixing to a specific first group of pixels or when providing a second group of pixels exclusively, it is possible to mount no color filter or mount a filter suitable for a strobe light source or the like. Regarding the color filters, if the pixels adopt the RGB filter, the spectral sensitivity characteristics as the light receiving element can be secured by selecting the light receiving elements so that the RGB filters have a certain fixed ratio. For example, there is a method of using four adjacent pixels as a light receiving element. At this time, the spectral sensitivity characteristic of the light receiving element can be changed by changing the ratio of the RGB pixels.

[0027]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Before describing the present embodiment with reference to the drawings, an outline of a CMOS type image pickup device will be described below. FIG. 1 is an equivalent circuit diagram of a CMOS image sensor. Although only a single pixel 50 is shown in FIG. 1, the pixel 50 is arranged two-dimensionally. The timing generator 5 is provided outside the pixel 50.
1, vertical shift register 52, horizontal shift register 5
3, circuits such as the output amplifier 54 are configured. The vertical shift register 52 is a register for selecting a scanning line, and the horizontal shift register 53 is a register for pixels 5 in the same scanning line.
This is a register for selecting 0. The timing generator 51 controls the entire sensor including these. In addition to the above configuration, it is possible to incorporate a CDS circuit, an AD converter, a signal processing circuit, and the like.

The internal setting of the timing generator 51 can be performed externally by serial communication. In FIG. 1, only command input is viewed from the arrow, but 2-wire or 3-wire serial communication is assumed. By this serial communication, it is possible to set and change the registers inside the timing generator 51. As an exposure control signal, a dedicated terminal (T
Since RG1 and TRG2) are provided, they are transmitted via this terminal.

There are several conceivable methods for controlling the image pickup device, but in this embodiment, the trigger signal T
The exposure is started at the rising edge of the pulse of RG1 and is ended at the falling edge of the pulse. And
When the trigger signal TRG2 rises after the pulse of the trigger signal TRG1 rises and before the pulse falls and the pulse amount of the trigger signal TRG1 rises, the exposure is finished at that point.

More specifically, the operation of each part will be described. In FIG. 1, the light-receiving operation for the sweeping operation in the pixel 50 is performed by the power source Vrst1 via the MOS transistor Q2.
Is performed by the photosensor section (that is, the photodiode) D1 connected to the. When sweeping out the charges of the photodiode D1, the output signal RG1 of the timing generator 51 is controlled to turn on the transistor Q2 so that the charges are swept out to the power supply Vrst1. By turning on the MOS transistors Q2 of all pixels, the charges of all the photodiodes are swept out, and the transistors Q2
Exposure is started from the point when is turned off. This part corresponds to the charge discharging part.

A photodiode D is further provided for charge transfer.
1 is a capacitor C1 via a MOS transistor Q1
It is connected to the. This part corresponds to the charge storage part.
The output signal SG of the timing generator 51 is controlled,
By turning on the MOS transistors Q1 of all pixels, the charges of the photodiode D1 are transferred to the capacitor C1. Further, the exposure is completed by turning off the transistor Q1.

Next, the reading of charges will be described.
The electric charge accumulated in the capacitor C1 of each pixel is turned on by turning on the MOS transistor Q5.
Is read out one pixel (or one line) to the outside via the. Pixels are selected by the vertical shift register 52 and the horizontal shift register 53 (transistor Q6 is turned on here).
By specifying the address. That is,
The charge can be read out only from the addressed pixel. At this time, it is possible to read out the electric charges as they are, but since they are easily affected by noise, in the present embodiment, they are once converted into a voltage and output.

After that, the charge storage section is reset. More specifically, by turning on the MOS transistor Q3 at the same time after the reading is completed and before the next photographing is started, the charge of the capacitor C1 is swept out to the power source Vrst2 (cleared, that is, the power source Vr).
reset to st2). At this time, it is desirable to perform all pixels at the same time because the dark current noise amount between the pixels can be equalized. However, if the noise amount is sufficiently small, it may be performed pixel by pixel after reading. This charge is current-amplified and output by the amplifier 55 of the output section.

The reset function of the photodiode D1 can be omitted. In that case, the transistor Q2 is omitted. In this case, by transferring the charge to the capacitor C1, the photodiode D1 can be cleared and the exposure can be started from there. The charges transferred to the capacitor C1 are read out and discarded during the exposure period.

As a modified example, a case where a non-volatile memory (charge storage section) is provided will be described. In an image pickup device including a non-volatile charge storage unit and a non-volatile charge storage unit, first, charges are transferred from the photosensor unit to the non-volatile charge storage unit at the same time for all pixels, and then one pixel at a time. It is preferable to transfer the charges to the charge storage section. This is because a flash memory or the like generally has a low writing speed and takes a long time to write, so that the writing timing is adjusted.

FIG. 2 is a schematic configuration diagram of an image sensor circuit 20 including the image sensor of FIG. Each pixel 50 (FIG. 1) of the imaging unit 54 in which the pixels 50 shown in FIG. 1 are two-dimensionally arranged.
As described above, the vertical shift register 52 and the horizontal shift register 53, which are controlled by the image sensor control circuit 23 (including a timing generator) that receives a control signal from the MPU 27 as the control unit for controlling the exposure time, respectively, It is controlled and works.

In the present embodiment, a part of the pixel 50 is a pixel (second group of pixels) for performing photometry for detecting light from the subject for exposure control, and the remaining pixels (second group). One group of pixels) has a function of converting a subject image into image data. Therefore, the output signal from the pixel of the first group is amplified by the output amplifier 55 via the output terminal 55a and is output to the outside of the image sensor circuit 20, and the output signal from the pixel of the second group is output terminal. The signal amplified by the output amplifiers 56A and 56B via 56Aa and 56Ba and weighted by the weighting circuit 57 is input to the comparator 7 and compared with a predetermined reference value Vref (threshold value), and the result is obtained. It is designed to be output to 23. As shown in FIG. 2, the image pickup unit 54, the vertical shift register 52, the horizontal shift register 53, the image pickup device control circuit 23, the output amplifiers 55, 56A and 56B,
Also, the comparator 7, which is the determination unit, is integrated into one chip. Although not shown, the one-chip circuit also has a built-in register and a DA converter for setting the reference value Vref corresponding to the photometric level or the exposure level, and further rewriting this register from the outside. It also has a communication function for changing Vref.

However, as in the modified example shown in FIG. 3, after converting the digital signal as the comparison reference from the image sensor control circuit 23 into an analog signal through the D / A conversion circuit 58, Vref is used as the reference value. Alternatively, the weighted signals may be compared by inputting them to the comparator 7.

FIG. 4 is a schematic configuration diagram showing an array of pixels in the image pickup section 54. The pixels 50b, 50 of the second group are arranged at a predetermined interval in the pixels 50a of the first group which are two-dimensionally arranged.
c (shown by hatching) is arranged. In the present embodiment, in a general-purpose CMOS image sensor, a part of pixels for obtaining image data is used as pixels for exposure control, so that a low cost structure can be obtained.
According to this configuration, a part of the image data is used as the exposure control data, so that a state equivalent to a pixel defect (so-called black defect) occurs at the position of the pixel of the second group. However, it is considered that such a pixel defect does not cause a big problem because it can be corrected from the image data of the surrounding pixels, like a black defect that may occur normally. The number of pixels 50b and 50c in the second group is preferably about 30 to 100, assuming that the pixels 50a in the first group are 1M pixels. The pixels 50b and 50c of the second group are specified by the address and are preferably in a state of always outputting. In such a case, the outputs of a plurality of pixels can be combined to form one output. In the present embodiment, the second group of pixels 5
0c is arranged in a region corresponding to the center of the photographing screen (that is, the center of the light receiving portion of the image sensor), and the second group of pixels 50b is
It is arranged in a region corresponding to the periphery of the photographing screen (that is, in the periphery of the light receiving portion of the image sensor).

FIG. 5 is a wiring diagram for signal extraction when the image pickup section of FIG. 4 is used. As shown in FIG. 5, the first group of pixels 50a and the second group of pixels 50b, 50
c is connected to the output amplifiers 55, 56A, 56B by independent wirings W2, W1, W3.

Since a main subject such as a person is often present in the center of the photographing screen, the weighting circuit 57 performs a weighting process so that the subject is more appropriately exposed. More specifically, the central pixel 50
When the output signal value from c is Vc and the output signal values from the peripheral pixels 50b are Vb1 to Vb8, the weighted signal value V is given by the following equation. V = (3 × Vc + Vb1 + Vb2 + Vb3 + Vb4 + Vb5 + Vb6 + Vb7 + Vb8) / 11 (1) The weighting mode may be other than this.

FIG. 6 is a diagram showing the pixel arrangement and connection in the image pickup section 54 according to the modification of the present embodiment.
The second group of pixels 50b, 50c, and 50d (shown by hatching) are arranged between the first group of pixels 50a that are two-dimensionally arranged. In the present embodiment, two pixels 50c are arranged in the area corresponding to the center of the shooting screen,
Four pixels 50b are arranged in a region corresponding to the upper part of the photographing screen, and six pixels 50d are arranged on both sides and a lower side of the pixel 50c.

There are many scenes in which the upper part of the photographing screen is the sky and the lower part is the ground. Therefore, to make the exposure more appropriate,
The lower part of the shooting screen is preferable. Therefore, the weighting circuit 5
The weighting process in 7 is performed as follows. The output signal values from the central pixel 50c are Vc1 and Vc2, the output signal values from the upper pixel 50b are Vb1 to Vb4,
When the output signal value from the lower pixel 50d is Vd1 to Vd6, the weighting signal value V is given by the following equation. V = (5 × (Vc1 + Vc2) + 3 × (Vd1 + Vd2 + Vd3 + Vd4 + Vd5 + Vd6) + Vb1 + Vb2 + Vb3 + Vb4) / 32 (2) The weighting mode may be other than this. The number of pixels 50c in the central region may be three or more. Further, when three or more pixels 50c are arranged in one region, the output signal value of a pixel far from the average value thereof may be excluded as an abnormal value.

There are the following methods for reading out signals from the second group of pixels. 1) A method of simultaneously accessing all the light receiving elements, reading signals at the same time, adding them, and taking them out. In this case, the signals are read by designating the XY addresses so that the output transistors of all the light receiving elements are turned on. 2) A method of reading at high speed by switching pixel by pixel. In this case, it is necessary to consider the case of using a strobe and read out the signal at a time interval sufficiently short with respect to the emission time of the strobe light. The signals read out pixel by pixel are added externally. 3) A method combining the above. This is a method in which the light receiving elements are divided into several groups and read out for each group.

In the method 1), since signals are added and detected at once, it is possible to perform photometry with a fast response speed, and it is possible to perform photometry without using a complicated circuit or a complicated photometry algorithm. . The method 2) depends on the number of light receiving elements because the flash light emission time is about several hundred μs, but if the number of pixels of the second group is about 100, then
An access speed of 0 ns or less, preferably about 10 ns or less is required, but fine metering control as described later can be performed. The method of 3) is in the middle,
It has both advantages and disadvantages. For example, the signal of the light receiving element for one column is read out simultaneously, and the signal is sequentially read over all the columns and read out.

When individually reading, signals can be used adaptively. In the case of a CMOS type image pickup device, a signal can be read out for each pixel, so that, for example, during stroboscopic photography, the signal can be used by paying attention to a pixel that changes largely after strobe light emission. Initially, signals are read from all the pixels of the second group, but if there is a pixel having a large change after stroboscopic light emission, some or all of them are selected and only the signal from that pixel is read. That is, for example, when a person is photographed, the portion where the amount of reflected light such as the face or body is desired to be measured is focused and the light is measured. Further, in this case, the number of pixels of the second group to be used is reduced, so that the read cycle is shortened and the resolution in the time axis direction is increased,
More accurate photometry becomes possible. Further, when the dedicated second group of pixels is provided, the readout circuit can also be provided exclusively. Although the output circuit can be provided exclusively, it can be shared with the output of the image signal.

FIG. 7 is a diagram showing a schematic structure of an electronic still camera which is an example of the image pickup apparatus according to the present embodiment. In FIG. 7, 27 is an MPU that determines the aperture and shutter speed, and outputs control signals to various circuits.
Reference numeral 20 denotes a light emitting circuit that receives a trigger signal (light emission start signal) from the MPU 27 and causes the strobe 2, which is a light emitting device, to emit light, 21 denotes a photographing lens that collects reflected light from the subject 3, and 22 denotes FIG. It is a CMOS image sensor shown in FIG. An image sensor control circuit 23 controls the exposure amount of the image sensor 22 in response to a stop signal from the comparator 7 which is a determination unit. The operation of the electronic still camera configured as described above is as follows.

The operation of the present embodiment will be described with reference to the strobe emission characteristic diagram shown in FIG. A curve f shown in FIG. 8 is a strobe emission curve when the strobe 2 is fully emitted. In the present embodiment, the longest light emission time T2 of the strobe 2 from the time ts when the shutter is closed is set on the basis of the preset shutter speed (for example, 1/60 second corresponds to t1 to ts) in the strobe mode. (Usually 5
Strobe 2 at time tx, which is only 0 μs to 500 μs)
Light is emitted (the light emission amount is not controlled, and full light emission is sufficient). However, in the present embodiment, first, in the case of the normal AE mode, the brightness of the object is measured by the light incident on the pixels 50b and 50c (FIG. 4) of the second group of the image sensor 22 through the taking lens 21. The aperture and shutter time are determined by the MPU 27, and the strobe mode is automatically set when the shutter time is 1/60 seconds or more. Now, at time t1, the image sensor control circuit 23 gives a signal TRG1 to the timing generator 51, thereby sweeping out the charges in the photosensor section (photodiode D1 of FIG. 1) to start the exposure.

Next, after a lapse of a predetermined time, at time tx, M
When the PU 27 triggers, the light emitting circuit 120 causes the strobe 2 to emit light. The subject 3 is illuminated by strobe light emission. The reflected light from the subject 3 enters the image sensor 22 via the taking lens 21. During this time, the flash emission amount increases rapidly as shown in FIG. At time tx, the integration start signal enters the integration circuit (not shown) at the same time as the strobe light emission signal from the MPU 27. This allows
Integration of strobe light starts.

The integrator circuit includes a second group of pixels 50b and 50c.
The output of is integrated and its output increases with time. Then, at time ts' when the output reaches a predetermined standard photometric level, the comparator 7 operates and outputs a stop signal. Stop signal from comparator 7 to MPU
It may be output through 27.

Upon receiving this stop signal, the image pickup device control circuit 23 outputs the signal TRG2 to the timing generator 51 (FIG. 1), thereby ending the exposure operation of the image pickup device 22. As a result, the image information of the subject 3 in the optimal exposure state is stored in the charge storage section in each pixel. At this time, the integration time of the image sensor 22 is t1 to t
becomes s', and from the first setting (t1 to ts), (ts-t
s'), but this quantity is very short, (ts-
Since t1 >>ts-ts'), there is no problem, and the shutter speed (for example, 1/6) in the flash mode is originally set.
0 seconds t1 to ts) is not a particularly meaningful number, so there is no problem.

On the other hand, the strobe 2 continues to emit light even after the time ts' has elapsed, and is extinguished at the time ts (the time during which the strobe 2 emits light is T2). A region A is an exposure amount for an image integrated by the image sensor 22, and a region B is an exposure amount for not contributing to image formation. As described above, according to the present embodiment, it is possible to store the charge charge amount at the time when the optimum exposure amount is reached in the storage unit without stopping the stroboscopic light emission in which precise control of the light emission amount is difficult. . As a result, the exposure amount can be controlled with high accuracy with a simple configuration when the flash fires.

The above-mentioned concept of exposure control can be applied to daytime synchronization (a subject image with an appropriate exposure can be obtained by causing a strobe to emit light when the subject is backlit), and at this time, it is initially set. Shutter speed (1/60 of the above example
Except that (equivalent to seconds) changes depending on the brightness of the subject,
This is the same as the above example. However, if the shutter time becomes too short at this time, the above-mentioned ts-t1 >>ts-ts' will not hold and the exposure accuracy will be affected. At this time, therefore, the aperture will be made small, and the shutter time will be lengthened to some extent. It is necessary to devise. An example will be described. For example, it is assumed that the set exposure amount is reached immediately after the strobe emits light and the shutter is closed. That is, the shutter time shift (ts-ts') is almost equal to the longest flash emission time.
There was.

In order to keep the shutter speed deviation within -0.2 EV, if the strobe light emission time is yms and the shutter speed at which stroboscopic photography is possible is x ms, then y <(1-2
^{-0. 2} ) x. Therefore, to enable shutter speed up to 1/250, strobe light emission time is 517 μs or less, and up to 1/500 is strobe light emission time is 258 μs or less, and strobe light emission is possible to up to 1/1000. The time is 129 μs or less. Similarly, to keep the shutter speed deviation within -0.4 EV, y
<(1-2 ^−0.4 ) x, so shutter speed 1 /
Up to 250 968μs or less, up to 1/500 4
84 μs or less, up to 1/1000 242 μs or less,
If it is up to 1/2000, it will be 121 μs or less, and if the shutter-second deviation is large, the subject hit by the strobe will be properly exposed, but the part where the strobe light cannot reach will be underexposed or overexposed.

Also, the longest strobe emission time (50 μs to 5 μs)
00 μs) is not fixed but can be linked to distance information from an AF (autofocus) system (not shown). For example, if (subject distance) × (aperture) is small considering the set aperture, the amount of light emission can be small, and thus ts−tx can be estimated to be small. On the contrary, if (subject distance) × (diaphragm) is large, a large amount of light emission is required, and ts−tx can be estimated long.

FIG. 9 shows stroboscopic light emission characteristics when (subject distance) × (aperture) is small, and FIG. 10 shows (subject distance) ×
FIG. 6 is a diagram showing strobe emission characteristics when the (aperture) is large. As mentioned above, (subject distance) x (aperture)
When is small, the amount of light emission is small, so that the area A becomes small as shown in FIG. On the other hand, when (subject distance) × (diaphragm) is large, a large amount of light emission is required, and the area A becomes large as shown in FIG.

If such a method is used, even if the shutter speed becomes short during the daytime synchronization as described above, t
Since s'-tx is estimated, ts-ts' can be shortened, and the error can be reduced as compared with the above example. Therefore, faster daytime synchronization becomes possible.
Of course, when ts 'comes after ts, the initially set ts is ignored, and the integration of the solid-state image sensor continues until ts', that is, until the stop signal is output. However, although not shown in the figure, when the amount of light emission is insufficient and the stop signal is not output, the charge accumulated in the photosensor unit is discharged at either ts or ts'. That is, the shutter is closed. Alternatively, after a lapse of a time longer than ts or ts', the shutter speed at the limit of camera shake (for example, 1 /
60 seconds) or the slowest shutter speed (eg 1 /
The exposure may be completed by forcibly transferring the electric charge accumulated in the photosensor portion for 8 seconds).

Next, the photographing control flow of this embodiment shown in FIG. 11 will be described. Step S10 in FIG. 113
In step 1, when the photographer turns on the main switch, electric power is supplied to each unit in step S102.
At 3, a capacitor (not shown) in the flash light emitting circuit 120 is charged. Strobe charging may be performed only when necessary. Furthermore, in step S104, the photographer waits for the release button (not shown) to be pressed. When the release button is pressed, in step S105, the MPU2
7 starts exposure control for exposure control using the weighted outputs of the pixels 50b and 50c of the second group, and after exposure control is completed in step S106, it is determined in step S107 whether strobe light emission is necessary. To do. Although various modes of exposure control can be considered, the pixels 50b, 50 of the second group
The optimum exposure condition can be determined based on the value obtained by weighting the data continuously read from c.

At this time, when it is determined that the stroboscopic light emission is necessary because the illuminance of the subject is low, the MPU 27 starts the exposure in step S108 and sends a trigger signal to the light emitting circuit 120 in step S109 to cause the strobe 2 to emit light. .

The signal reading from the pixels 50b and 50c of the second group is started after the exposure is started or immediately before the light emission. Read the output every clock and check the output value. The pixel signals are used as they are for the pixels 50b and 50c of each second group. The signals from each pixel are read simultaneously for each clock. That is, the output of each pixel is added and read. Starting reading out before strobe light emission corresponds to resetting each pixel before light emission.

In step S110, the second group of pixels 50
Based on the outputs from b and 50c, it is determined whether or not the strobe light emission amount exceeds a predetermined value. If the MPU 27 determines that the strobe light emission amount has exceeded the predetermined value, the MPU 27 sends a stop signal to the light emission circuit 120 to forcibly end the strobe light emission or end the exposure (the first group of pixels 50).
a) stop the charge accumulation or discharge the charge). On the other hand, if it is determined that the flash emission amount has not exceeded, MP
The U 27 waits until the scheduled exposure time ends in step S113, and completes the exposure operation in step S114.

On the other hand, when it is determined that the stroboscopic light emission is unnecessary because the illuminance of the subject is high, the MPU 27 starts the exposure in step S112 without performing the stroboscopic light emission, and ends the scheduled exposure time in step S113. Waits until the exposure operation is completed in step S114.

Thereafter, in step S115, the MPU 27
The image signal is read from the first group of pixels 50a and stored in a memory (not shown) in step S16. The power supply is cut off as necessary (step S117).

A supplementary explanation of the above control will be given. After the strobe light emission, the second light read after the light emission is triggered by the light emission.
The pixel signals of the pixels 50b and 50c of the group are integrated every clock. The integrated value is compared with a preset threshold value (photometric level) in the comparator 7,
When the threshold value is reached, a stop signal is output to the image sensor control circuit, and the electronic shutter of the image sensor is closed to end the exposure.

As a method of extracting a signal, in addition to reading every clock, an output may be taken out in a state where a signal line is directly connected from a pixel which has been reset and cleared once. In this case, the strobe light is integrated by the pixel. It is recommended that the signal obtained by adding the outputs of the respective pixels (light receiving elements) be compared by the comparator 7. As will be described later with reference to FIG. 12, the pixels 50b and 50c of the second group can be selected in some cases. For example, when the pixels that receive light from a high-luminance subject are the pixels of the second group, it may not be possible to ignore the intensity of the strobe light. When the output of such a pixel is used for photometry control, an error may occur in the detection of the amount of strobe light. In order to eliminate this, the pixel of the second group is scanned in advance to detect whether or not the high-intensity subject light is received, and when it is received, this pixel is excluded so as not to be used as a light-receiving element. Is. However, since the strobe light emits relatively strong light in a short time, the influence of the normal light within the light emission time may be negligible, and in that case, the selection work may be omitted.

In the present embodiment, when the output of the pixels of the second group reaches the preset photometric level, the stop signal is output from the comparator 7 and input to the image sensor control circuit 23. As a result, the image sensor control circuit ends the exposure of the image sensor. The above functions can be integrated on the image sensor 22. The photometric level and the like may be set externally.

When the pixels of the color image pickup device are used as the second group of pixels, in the BGR filter, there are a method in which the pixels are represented by green pixels and a method in which the BGR pixels are selected and represented in a well-balanced manner. It is possible to mount another color filter only on the pixels of the second group, or not to mount it.

FIG. 12 is a diagram showing a photographing control flow for explaining in detail the modified example of the strobe exposure control of FIG. The present modification shows control when light from a high-luminance subject such as a light emitter such as a light enters a pixel of the second group. After the exposure control ends in step S106 in FIG. 11, the MPU 27 determines in step S201 in FIG. 12 whether the second group of pixels 50b and 50c that have received the light from the high-luminance subject should be divided. If the MPU 27 determines that the pixels should be divided,
The pixels 50b and 50c of the second group are scanned at high speed (the output of each pixel is checked). If the output of any of the pixels is lower than the specified value (threshold value), it is determined that the light is not from the high-luminance subject, and the MPU 27 registers the pixel. on the other hand,
If the output of any of the pixels is equal to or greater than the specified value (threshold value), it is determined that the light is from a high-luminance subject, and the MPU 27 determines
Excluding such pixels, the photometry of the strobe reflected light is performed.
The threshold value may be a fixed value, but when there are three or more pixel signals, it is possible to find the average value and exclude the pixel signals that are far from the average value.

In step S206, all the pixels 5 of the second group
When the scan of 0b and 50c is completed, or when it is determined in step S201 that it is not necessary to divide the pixels 50b and 50c of the second group that received the light from the high-brightness subject, the MPU 27 performs exposure in step S207. Start
In step S208, the pixels 50b and 50c of the second group are reset, and in step S209, the flash light emitting circuit 120 is
Strobe light 2 is emitted via. After that, step S
In 210, the MPU 27 reads the signal output from the pixel 50a of the first group, in step S211, integrates the signal, compares the integrated value with a specified value (threshold value), and if it exceeds the specified value. In step S214, the stroboscopic light emission is stopped, or the exposure is ended (the charge accumulation in the pixel 50a of the first group is stopped or the charge is discharged).
After waiting for the scheduled time to pass in step 13, the exposure is ended in step S114 in FIG.

In the present embodiment described above, the first group of pixels 50a for image data acquisition and the second group of pixels 50b, 50c for exposure control data acquisition are independent. However, if the pixels 50b and 50c of the second group are so-called non-destructive readable pixels, the amount of the accumulated charges can be confirmed without being taken out, so that the pixels are accumulated in the pixels 50b and 50c of the second group. The charged electric charges can be used as a part of the image data, whereby the image quality can be improved. Alternatively, the integration may be started after the charge of the pixels 50b of the second group is completely discharged and then the charge of the pixels 50a of the first group can be output.

As described above, since the charge of any pixel can be read out by using the CMOS type image pickup device, a part of the pixels of the image pickup device 22 can be used for acquiring exposure control data as in the present embodiment. Therefore, the light receiving element for measuring the field brightness, which is provided in the prior art, becomes unnecessary, and the cost can be reduced and the degree of freedom in appearance design can be increased.

Although the present invention has been described with reference to the embodiments, the present invention should not be construed as being limited to the above embodiments, and it goes without saying that appropriate modifications and improvements are possible. is there. For example, the present invention can be used for general exposure control, not limited to photometry of strobe reflected light. or,
The present invention is not limited to the electronic still camera, but can be applied to various imaging devices such as a radiation imaging device.

It is also possible to use only the pixels on which the G filter is mounted as the second group of pixels for acquiring the exposure control data. Further, it is not necessary to fix the positions of the pixels of the second group. For example, in the case of center-weighted photometry, the pixel of the second group is selected from the pixel in the center of the image pickup section, and in the case of average photometry, the second group of pixels is selected from the entire image pickup section. It is also possible to select a group of pixels.

The terminal for acquiring image data and the terminal for acquiring exposure data may be shared, or a separate strobe light amount integration output terminal may be provided. When scanning and reading the signals from the pixels of the second group, the signals can be read separately for each part. For example, since an important subject is often located in the center, it is possible to read from the center, read it in columns or rows, or read it in a spiral shape. By providing two memories (charge storage units) in one pixel and separately recording the image charge before strobe light emission and the image charge after light emission, the data before light emission can be acquired without damage. In order to control the strobe light emission time, it is possible to estimate an appropriate amount of light in advance and make the light emission earlier by the amount corresponding to the exposure end time.

[0075]

According to the image processing system of the present invention, the number of necessary parts and the number of adjustment steps are reduced, so that the cost is low, the design is not restricted, and the photometry is possible with a small error. It is possible to provide an image sensor used for that purpose.

[Brief description of drawings]

FIG. 1 is an equivalent circuit diagram of a CMOS image sensor according to the present embodiment.

FIG. 2 is a schematic configuration diagram of an image sensor circuit 20 including the image sensor of FIG.

FIG. 3 is a schematic configuration diagram of a modified example of an image sensor circuit including the image sensor of FIG.

FIG. 4 is a schematic configuration diagram showing an array of pixels in an image pickup section.

5 is a wiring diagram for signal extraction when the image pickup unit in FIG. 4 is used.

FIG. 6 is a wiring diagram for pixel arrangement and signal extraction of an image pickup unit according to a modification.

FIG. 7 is a diagram showing a schematic configuration of an electronic still camera which is an example of an image capturing apparatus according to the present embodiment.

FIG. 8 is a strobe emission characteristic diagram.

FIG. 9 is a diagram showing stroboscopic light emission characteristics when (subject distance) × (aperture) is small.

FIG. 10 is a diagram showing strobe emission characteristics when (subject distance) × (aperture) is large.

FIG. 11 is a diagram showing a shooting control flow of the present embodiment.

FIG. 12 is a diagram illustrating a shooting control flow for describing in detail a modified example of the flash exposure control in FIG.

[Explanation of symbols]

2 Strobe 7 comparator 22 CMOS image sensor 23 Image sensor control circuit 27 MPU 50 Imaging unit 50a First group of pixels 50b Second group of pixels (peripheral or upper area) 50c Second group of pixels (central region) 50d Second group of pixels (lower area) 51 Timing generator 52 Vertical shift register 53 Horizontal shift register 57 Weighting circuit

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) H04N 5/335 H04N 5/335 Q (72) Inventor Takao Hosaka 1 Sakura-cho, Hino-shi, Tokyo Konica Stock Company (72) Inventor Hiroshi Kobayashi 1 Sakura-cho, Hino City, Tokyo Konica stock company (72) Inventor Atsushi Takayama 2970 Ishikawa-cho, Hachioji-shi, Tokyo Konica stock company (72) Inventor Koichi Sato Tokyo 2970 Ishikawa-cho, Hachioji-shi Konica stock company (72) Inventor Sogo Kitada 2970 Ishikawa-cho, Hachioji-shi Tokyo Konica stock company F-term (reference) 2H002 DB01 DB04 DB06 DB11 DB15 DB19 DB23 DB24 DB26 DB27 DB29 DB30 DB31 GA24 HA04 JA07 5C022 AA13 AB06 AC42 AC69 5C024 BX01 CY17 DX04 EX11 GX03 GY31

Claims (16)

[Claims] 1. An imaging device for imaging an object, comprising an imaging element having a plurality of pixels arranged two-dimensionally, wherein the imaging element is a first group used for converting the object into image data. And pixels of a second group used for performing photometry, the pixels of the second group are arranged in each of a plurality of regions, and each pixel from the pixels of the second group is arranged. An image pickup apparatus comprising: a control unit that controls an exposure time based on an output signal for each area. 2. An imaging device for imaging a subject, comprising an imaging device having a plurality of pixels arranged two-dimensionally, wherein the imaging device is a first group used for converting the subject into image data. And a second group of pixels used for performing photometry, the second group of pixels are arranged in each of a plurality of regions, and the second group of pixels in each region are arranged. An imaging device, wherein an output amplifier for amplifying an output signal from a pixel is provided for each area, and photometric data is obtained based on the output signal from the pixel of the second group. 3. An imaging device for imaging a subject, comprising an imaging device having a plurality of pixels arranged two-dimensionally, wherein the imaging device is a first group used for converting the subject into image data. And pixels of a second group used for performing photometry, the pixels of the second group are arranged in each of a plurality of regions, and output from the pixels of the second group. The signal is used as photometric data by performing a predetermined weighting for each area. 4. The photographing according to claim 1, wherein the plurality of regions include a central region corresponding to the center of the photographing screen and a peripheral region corresponding to the periphery thereof. apparatus. 5. The output signal of the pixel of the second group corresponding to the central area is weighted more than the output signal corresponding to the peripheral area. The imaging device described. 6. The image data corresponding to the positions of the pixels of the second group is the first data located around the pixels of the second group.
The photographing apparatus according to any one of claims 1 to 5, wherein the photographing device is obtained based on image data of pixels of the group. 7. The image pickup apparatus according to claim 1, wherein the pixels of the second group are a part of the pixels of the first group. 8. The image pickup device according to claim 1, further comprising a determination unit that determines whether or not the charge accumulated in the pixels of the second group exceeds a threshold value. Imaging device. 9. The image pickup apparatus according to claim 1, wherein the image pickup device has an output terminal that outputs the electric charge accumulated in the pixels of the second group to the outside. 10. When there are three or more pixels of the second group in one region, the value of the electric charge accumulated in one of the pixels is relative to the average value of the electric charges accumulated in other pixels. 10. The image capturing apparatus according to claim 1, wherein, when the charge value is higher than a predetermined value, the charge of the pixel having a high charge value is excluded and compared with the threshold value. 11. The charge accumulated in the pixels of the second group is discharged at the same time.
0. The imaging device according to any one of 0. 12. The imaging device according to claim 1, wherein the charges accumulated in the pixels of the second group are discharged according to a clock. 13. The charge accumulated in the pixels of the second group can be detected without being discharged, and the charge of the second group of pixels can be detected. Imaging device. 14. The accumulated charge is discharged in the order in which the trigger signal is applied by sequentially applying a trigger signal to the pixels of the second group. The imaging device according to claim 1. 15. The pixel of the second group has at least two charge storage units.
The imaging device according to any one of 1. 16. The image capturing apparatus according to claim 1, wherein the charges accumulated in the pixels of the second group are sequentially discharged from the pixel on the center side corresponding to the image capturing screen. .