JP2002300589A - Photographing apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a photographing apparatus for photographing under more appropriate conditions by maintaining the cost to be low. SOLUTION: Light from a subject passes through color filters FG, FR, and FB, and is received by a first group of pixels 50a. However, since the light does not pass through the color filters but is received by a second group of pixels 50b, a second group of pixels 50b can directly detect light from the actual subject, thus improving the accuracy in data for photometry.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a photographing device,
More specifically, the present invention relates to a still image photographing apparatus such as an electronic still camera which can control an exposure amount using an electronic shutter function and a light detection function of a solid-state imaging device.

[0002]

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

[0003]

However, in a scene where the brightness of the subject changes, the brightness of the field when the release switch is half-pressed and the brightness of the field when the release switch is fully pressed are different. And exposure may be inappropriate.

On the other hand, if a photometric element is separately 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 changed according to the change in the luminance of the field. It can be faster or slower, so that proper exposure can be performed. However, when the photometric element is separately provided, there arises a problem that the cost of the electronic still camera increases and the size of the electronic still camera increases.

[0005] In order to solve such a problem, a CMOS type image pickup device having a configuration different from that of a 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 take out the electric charge accumulated in the central pixel of the two-dimensionally arranged pixels and use it as photometric data. However, a CMOS type image sensor is usually provided with a color filter, and when using an output from a specific pixel for photometry, how to handle the color filter is a problem.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the related art, and has as its object to provide a photographing apparatus capable of photographing under more appropriate photographing conditions while maintaining a low cost. And

[0007]

According to a first aspect of the present invention, there is provided a photographing apparatus comprising: a first group of pixels for imaging a subject image;
An image sensor in which pixels of a group are two-dimensionally arranged; and a color filter. Light from a subject passes through the color filter and is received by the pixels of the first group. Since light is received by the second group of pixels without passing through a filter, the second group of pixels can directly detect light from an actual subject, so that the accuracy of photometric data can be improved. .

Further, the color filter has a structure in which each pixel having two rows and two columns of pixels as one block is covered with one of three color filters. When one pixel is included, it is preferable that the remaining pixels of the first group are covered with filters of different colors. That is, if three primary color filters are used for the pixels in two rows and two columns, the number of colors increases by one color, for example, green, red, blue, and green. Therefore, in this case, by removing the green transparent filter or changing the filter to a colorless filter, the corresponding pixels are set as the pixels of the second group, and the remaining pixels are provided with the filters of one color each. A group of pixels can be used, and a decrease in image quality can be prevented.

According to a second aspect of the present invention, there is provided an image pickup device in which a first group of pixels for imaging a subject image and a second group of pixels for photometry are two-dimensionally arranged, a first color and a first color, A color filter including two-color and third-color filters, wherein the second group of pixels includes a first pixel that receives a subject image via the first-color filter; and a second-color filter. A second pixel that receives the subject image through the third color filter, and a third pixel that receives the subject image through the third color filter.
Since photometric data is obtained based on the output values of the second and third pixels, photometry can be performed according to the color temperature of the shooting scene and the characteristics of the strobe light. When the output values of the first, second and third pixels are weighted, for example, photometric data obtained by appropriately exposing the main subject can be obtained.

The color filters preferably include red, green and blue filters, but are not limited thereto.

In the image pickup device according to the present invention, the pixels of the second group are simultaneously turned on when the output signal (accumulated charge) is discharged, that is, when there are a plurality of pixels.
(Discharge state), or output may be taken out by periodically accessing at high speed. When there are a plurality of pixels in the second group, it is preferable to scan while switching pixels at high speed. This is detected at one or a plurality of locations. For example, when strobe light emission is performed, a short-term output change immediately after the light emission is observed by detecting the charges of the pixels of the second group. When the threshold value is exceeded, a signal for stopping the emission of strobe light is output. If the second group of pixels is used for exposure control, it can be interpolated later from peripheral pixels in the same manner as a defective pixel.

In addition to using a part of the two-dimensionally arranged pixels, a second group of pixels dedicated to acquiring exposure control data may be provided in the imaging unit. For example, when a light receiving element is provided between pixels, the effect on image quality is reduced,
There are problems such as an increase in the wiring area. It is also conceivable to arrange a pixel or a light receiving element around the imaging unit. It is also conceivable to provide light receiving elements arranged in a line instead of a single pixel. The charge accumulated in the second group of pixels is
It is also conceivable to divide the data into exposure control data and image data. At this time, the output of the pixel is smaller than the output of the pixel for extracting the image data. However, amplification of the output has the advantage that the deterioration of the image quality is smaller than that obtained by interpolation from surrounding pixels.

Further, if the pixel has an element structure capable of nondestructive readout (that is, a pixel from which the amount of accumulated electric charge can be obtained without discharging electric charge), it is provided for obtaining exposure control data. The signals of the second group of pixels can also be used as image data. In this case, for example, it is preferable to compare data read before the flash emission with data read after the flash emission, and terminate the exposure when the data exceeds a preset light control level.

[0014]

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. FIG. 1 is an equivalent circuit diagram of a CMOS image sensor. Although only a single pixel 50 is shown in FIG. 1, the pixels 50 are two-dimensionally arranged. A 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 selecting pixels 5 in the same scanning line.
This register selects 0. The timing generator 51 controls the entire sensor including these components. In addition, in addition to the above configuration, a CDS circuit, an AD converter, a signal processing circuit, and the like may be incorporated.

The settings inside the timing generator 51 can be made externally by serial communication. In FIG. 1, only the command input is viewed from the arrow, but it is assumed that two-wire or three-wire serial communication is performed. With this serial communication, it is possible to set and change registers in the timing generator 51. As an exposure control signal, a dedicated terminal (T
RG1, TRG2) are provided, so that the data is transmitted through such terminals.

There are several methods for controlling the image pickup device, but in this embodiment, the trigger signal T
Exposure starts at the rising edge of the pulse of RG1, and ends at the falling edge of the pulse. And
When the trigger signal TRG2 rises after the trigger signal TRG1 rises and the trigger signal TRG2 rises after the rise of the pulse of the trigger signal TRG1 and before the fall of the pulse, the exposure ends.

More specifically, the operation of each section will be described. In FIG. 1, the light receiving operation for the sweeping operation in the pixel 50 is performed by the power supply Vrst1 via the MOS transistor Q2.
This is performed by an optical sensor unit (that is, a photodiode) D <b> 1 connected to the control unit. When sweeping out the charge of the photodiode D1, the output signal RG1 of the timing generator 51 is controlled and the transistor Q2 is turned on to sweep out the charge to the power supply Vrst1. By turning on the MOS transistors Q2 of all the pixels, the charges of all the photodiodes are swept out, and the transistors Q2
Exposure is started at the point when is turned off. Such a portion corresponds to a charge discharging portion.

For charge transfer, a photodiode D
1 is a capacitor C1 via a MOS transistor Q1.
It is connected to the. This portion corresponds to a charge storage unit.
Controlling the output signal SG of the timing generator 51,
By turning on the MOS transistors Q1 of all the pixels, the charge of the photodiode D1 is 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 charge accumulated in the capacitor C1 of each pixel is turned on by turning on the MOS transistor Q5.
, One pixel (or one line) is read out to the outside. The pixel is selected by the vertical shift register 52 and the horizontal shift register 53 (here, the transistor Q6 is turned on).
This is done by specifying an address. That is,
The charge can be read out only from the addressed pixel. At this time, it is possible to read out the charge as it is, but since it is easily affected by noise, in this embodiment, the charge is once converted into a voltage and output.

Thereafter, the charge storage section is reset. More specifically, after the reading is completed, the MOS transistor Q3 is simultaneously turned on until the next photographing is started, thereby sweeping out the charge of the capacitor C1 to the power supply Vrst2 (clearing, that is, the power supply Vr2).
reset to st2). At this time, it is preferable that all pixels are simultaneously performed, since the amount of dark current noise between pixels can be equalized. However, when the amount of noise generation is sufficiently small, it may be performed pixel by pixel after reading is completed. The electric charge is amplified by the amplifier 55 of the output unit and output.

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

As a modified example, a case where a nonvolatile memory (charge storage section) is provided will be described. In an image sensor including a non-volatile charge storage unit and a non-volatile charge storage unit, first, all the pixels are simultaneously transferred from the optical sensor unit to the non-volatile charge storage unit, and then the pixels are sequentially transferred to the non-volatile charge storage unit. It is preferable to transfer the charge to the charge storage unit. This is because a flash memory or the like generally has a slow 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.
Are controlled and operated by the vertical shift register 52 and the horizontal shift register 53 controlled by the image sensor control circuit 23 (including the timing generator) which receives the control signal from the MPU 27, as described above. I have.

In the present embodiment, some of the pixels 50 are pixels (second group of pixels) for performing photometry for detecting light from a subject for exposure control, and the remaining pixels (second group of pixels) are used. (A group of pixels) has a function of converting a subject image into image data. Therefore, an output signal from the first group of pixels is amplified by the output amplifier 55 via the output terminal 55a and output to the outside of the image sensor circuit 20, and an output signal from the second group of pixels is output from the output terminal 55a. The signal is amplified by the output amplifier 56 via 56a, compared with a predetermined photometric level (threshold) by the comparator 7, and the result is output to the image sensor control circuit 23. As shown in FIG. 2, the imaging unit 54, the vertical shift register 52, the horizontal shift register 53, the image sensor control circuit 23, and the output amplifier 5
5, 56 and the comparator 7 are made into one chip. Although not shown, the one-chip circuit has a built-in register for setting the photometric level and a D / A converter, and further has a communication function for externally rewriting this register to change the photometric level. Also have.

FIG. 3 is a schematic diagram showing the arrangement of pixels in the image pickup section 54. The second group of pixels 50b (shown by hatching) are arranged at predetermined intervals in the first group of pixels 50a arranged two-dimensionally. In this embodiment, a low-cost configuration can be achieved by using a part of pixels for obtaining image data as exposure control pixels in a general-purpose CMOS image sensor. According to this configuration, a part of the image data is used as exposure control data, so that a state equivalent to a pixel defect (a so-called black defect) occurs at the position of the second group of pixels. However, since such a pixel defect can be corrected from the image data of the surrounding pixels as in the case of a black defect that can usually occur, it is considered that no major problem occurs. The number of pixels 50b in the second group is preferably about 30 to 100, assuming that the pixels 50a in the first group have 1M pixels. The second group of pixels 50b is specified by an address,
It is good to be in the state of always outputting. In such a case, the outputs of a plurality of pixels can be combined into one output. The pixels 50b of the second group may be arranged only at the center, or may be arranged at predetermined intervals over the entire imaging unit 50.

FIG. 4 is a wiring diagram for extracting signals when the image pickup unit of FIG. 3 is used. As shown in FIG. 4, the first group of pixels 50a and the second group of pixels 50b
The output amplifier 55,
56.

FIG. 5 is a schematic configuration diagram showing an array of pixels in the image pickup section 54 according to a modification of the present embodiment.
A second group of pixels 50b (shown by hatching) is arranged between the first group of pixels 50a arranged two-dimensionally. In the present embodiment, although it is necessary to manufacture the CMOS type imaging device exclusively (including the wiring dedicated to the second group of pixels 50b), unlike the configuration of FIG. Can be kept high.

FIG. 6 is a wiring diagram for extracting signals when the image pickup section of FIG. 5 is used. As shown in FIG. 6, the first group of pixels 50a and the second group of pixels 50b
The output amplifier 55,
56.

FIG. 7 is a diagram showing an arrangement relationship between pixels and filters. Of the multi-row and multi-column pixels arranged two-dimensionally,
Two rows and two columns are treated as one pixel block, and image data for one pixel is extracted from these. One pixel block including the photometric pixels is arranged as shown in FIG. Here, the upper two and the left one in the figure are the pixels 50 of the first group.
a, the remaining one is a second group of pixels 50b. The color filters cover the first group of pixels 50a with a green filter FG, a red filter FR, and a blue filter FB (disposed on the subject side). The second group of pixels 50b is not covered with any color filters. In the other pixel blocks, the first group of pixels 50a is arranged instead of the second group of pixels 50b, so that a green filter FG (not shown) is arranged at a position corresponding to the first group of pixels 50a. .

As described above, by not covering the second group of pixels 50b with a filter of any color, light from a subject can be directly received by the second group of pixels 50a, and a highly accurate photometric Data can be formed. As described above, a colorless and transparent filter may be attached instead of removing the filter at the position corresponding to the pixel 50b of the second group.

FIG. 8 is a diagram showing another arrangement relationship between pixels and filters. In this example, all the pixels in one pixel block are set as the second group of pixels 50b. From top to right in the diagram,
A green filter FG, a red filter FR, a blue filter FB, and a green filter FG are arranged in this order.

As described above, the entirety of one pixel block is
By forming the group of pixels 50b and covering them with filters of different colors, the amount of light that has passed through the filters of each color can be determined individually by the pixels 50b of the second group. At this time, by changing the ratio (weighting) of the output value of each pixel, the spectral sensitivity characteristics of the light receiving element can be changed according to, for example, the color temperature of the shooting scene or the strobe characteristics.

There are the following methods for reading out signals from the pixels of the second group. 1) A method in which all light receiving elements are accessed simultaneously, signals are read out at the same time, and the signals are added and taken out. In this case, the XY address is specified so that the output transistors of all the light receiving elements are turned on, and the signal is read. 2) A method of switching and reading out one pixel at a time at high speed. In this case, it is necessary to read out the signal at a time interval sufficiently earlier than the emission time of the strobe light in consideration of the use of the strobe. The signals read out pixel by pixel are added externally. 3) A method combining the above. In this method, 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, photometry with a high response speed can be performed, and photometry can be performed without using a complicated circuit or a complicated photometric algorithm. . The method 2) depends on the number of light receiving elements because the emission time of the strobe light is about several hundred μs.
An access speed of 0 ns or less, preferably about 10 ns or less is required, but fine photometric control described later can be performed. Method 3) is in between
It has both advantages and disadvantages. For example, signals of the light receiving elements for one column are simultaneously read, and the signals are sequentially switched and read over all columns.

In the case of individual reading, signals can be used adaptively. In the case of a CMOS image sensor, a signal can be read for each pixel, so that, for example, at the time of flash photography, a signal can be used by focusing on a pixel that changes greatly after the flash emission. At first, signals are read out from all the pixels of the second group. If there are pixels whose change is large after the strobe light emission, some or all of them are selected and only the signals from the pixels are read out. In other words, for example, when a person is photographed, photometry is performed by focusing on a portion of the face, body, or the like where the amount of reflected light is to be measured. Further, in this case, the readout cycle is shortened, the resolution in the time axis direction is increased, and more accurate photometry is possible, as the number of pixels of the second group used is reduced. Also, a dedicated second
When a group of pixels is provided, a readout circuit can also be provided exclusively. An output circuit can also be provided for exclusive use,
It can be common with the output of the image signal.

FIG. 9 is a diagram showing a schematic configuration of an electronic still camera which is an example of the photographing apparatus according to the present embodiment. In FIG. 9, an MPU 27 determines an aperture and a shutter speed, and outputs a control signal to various circuits.
Reference numeral 120 denotes a light-emitting circuit that receives a trigger signal (light-emission start signal) from the MPU 27 and emits light from the strobe 2 as a light-emitting device. Reference numeral 21 denotes a photographing lens that collects reflected light from the subject 3; Is a CMOS type imaging device shown in FIG. Reference numeral 23 denotes an image sensor control circuit that controls a light exposure of the image sensor 22 in response to a stop signal from the comparator 7 serving as a determination unit. The operation of the electronic still camera configured as described above is as follows.

The operation of this embodiment will be described with reference to the strobe light emission characteristic diagram shown in FIG. FIG.
Is a strobe light emission curve when the strobe light 2 is fully emitted. In the present embodiment, the shutter speed (for example, 1/60) in the preset flash mode is set.
Based on (t1 to ts in seconds) in the drawing, the strobe 2 is caused to emit light at the time tx shorter than the time ts when the shutter is closed by the longest emission time T2 of the strobe 2 (normally 50 μs to 500 μs) (the amount of light emission is controlled). And full light emission may be used.). In the present embodiment, in the case of the normal AE mode, first, the brightness of the subject is measured by the light that has entered the second group of pixels 50 b (FIG. 3) of the imaging device 22 through the imaging lens 21. , The MPU 27 determines the aperture and the shutter time, and the shutter time is 1 /
When the time exceeds 60 seconds, the strobe mode is automatically selected. At time t1, the image sensor control circuit 23 sends the signal T to the timing generator 51.
Exposure is started by applying RG1 to sweep out the charges in the photosensor unit (photodiode D1 in FIG. 1).

Next, after a lapse of a predetermined time, at time tx, M
When a trigger is input from the PU 27, the light emitting circuit 120 makes the strobe light emit. The subject 3 is illuminated by strobe light emission. The reflected light from the subject 3 enters the image sensor 22 via the photographing lens 21. During this time, the amount of strobe light increases rapidly as shown in FIG. At time tx, at the same time as the strobe light emission signal from MPU 27,
An integration start signal enters an integration circuit (not shown). Thus, the integration of the strobe light starts.

The integration circuit integrates the output of the second group of pixels 50b, and the output increases with time. Then, the time t when the output reaches a predetermined reference dimming level
At s', the comparator 7 operates and outputs a stop signal. The stop signal may be output from the comparator 7 through the MPU 27.

Upon receiving this stop signal, the image sensor control circuit 23 outputs a signal TRG2 to the timing generator 51 (FIG. 1), thereby terminating the exposure operation of the image sensor 22. Thereby, the image information of the subject 3 in the optimal exposure state is stored in the charge storage unit in each pixel. At this time, the integration time of the image sensor 22 is from t1 to t.
s' and (ts-t) from the first setting (t1 to ts).
s'), but this quantity is very short, (ts-
Since t1≫ts−ts ′), there is no problem, and the shutter speed originally in the flash mode (for example, 1/6
0 seconds t1 to ts) is not a problem since it is not a particularly significant number.

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

The above-described concept of exposure control can be applied to daytime synchronization (an object image with an appropriate exposure can be obtained by emitting a strobe light when the object is backlit, etc.). Shutter time (1/60 of the above example)
Seconds), depending on the brightness of the subject,
This is the same as the previous example. However, if the shutter time is too short at this time, the above-mentioned ts-t1≫ts-ts' does not hold and affects the exposure accuracy. Therefore, at this time, the aperture is made small and the shutter time is made somewhat longer. Ingenuity is required. This will be described with an example. For example, suppose that the set exposure amount is reached immediately after the strobe light is emitted and the shutter is closed. In other words, the shift of the shutter time by almost the longest light emission time of the strobe (ts-ts')
Suppose there was.

In order to make the shift of the shutter time within -0.2 EV, assuming that the flash emission time is yms and the shutter speed xms at which flash photography is possible, y <(1-2)
^{-0. 2} ) x Therefore, the strobe light emission time is 517 μs or less to enable shutter speeds up to 1/250, the strobe light emission time is 258 μs or less to enable shutter speeds up to 1/500, and the strobe light emission is possible up to 1/1000. The time is 129 μs or less. Similarly, to make the shift at the shutter time within -0.4 EV, y
<( ^1-2−0.4 ) x, the shutter speed 1 /
968 μs or less for up to 250, 4 for up to 1/500
84 μs or less, up to 1/1000, 242 μs or less,
If it is up to 1/2000, it is 121 μs or less, and if the shift in shutter time is large, the subject to which the strobe light strikes is properly exposed, but the portion where the strobe light does not reach will be underexposed or overexposed.

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

FIG. 11 shows the flash emission characteristics when (subject distance) × (aperture) is small, and FIG. 12 shows (subject distance)
FIG. 6 is a diagram illustrating strobe light emission characteristics when x (aperture) is large. As described above, when (subject distance) × (aperture) is small, the amount of light emission can be small.
As shown in FIG. On the other hand, when (subject distance) × (aperture) is large, a large amount of light emission is required, and the area A becomes large as shown in FIG.

By using such a method, even if the shutter speed becomes short at the time of 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. Accordingly, faster daytime synchronization is possible.
Of course, when ts 'is later than ts, the initially set ts is ignored, and integration of the solid-state imaging device is continued until ts', that is, until a stop signal is output. However, although not shown in the figure, when the amount of light emission is insufficient and no stop signal is output, the charge accumulated in the optical sensor unit is discharged at either ts or ts'. That is, the shutter is closed. Alternatively, after a longer time than ts or ts' elapses, the shutter speed at the camera shake limit (for example, 1 /
60 seconds) or the slowest shutter time (for example, 1 /
Exposure may be terminated by forcibly transferring the charge stored in the optical sensor unit (for example, 8 seconds).

Next, the photographing control flow of this embodiment shown in FIG. 13 will be described. Step S101 in FIG.
Then, when the photographer turns on the main switch, power is supplied to each unit in step S102, and step S103 is performed.
This charges a capacitor (not shown) in the strobe light emitting circuit 120. Strobe charging may be performed only when necessary. Furthermore, the process waits for the photographer to press a release button (not shown) in step S104, and when the release button is pressed, the MPU2 is pressed in step S105.
7 denotes a second group of pixels 50b (or a first group of pixels 50a,
Alternatively, exposure control for exposure control is started using the outputs of the two), and after the exposure control is completed in step S106,
In step S107, it is determined whether strobe light emission is necessary. There are various possible modes of exposure control.
Based on data (or data weighted for each filter color) read continuously from the group of pixels 50b,
Optimal exposure conditions can be determined.

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

After the start of the exposure or immediately before the light emission, the signal reading from the pixels 50b of the second group is started. The output is read every clock and the output value is checked. Each second group of pixels 50b uses the pixel signal as it is. The signals from each pixel are read out simultaneously for each clock. That is, the outputs of the respective pixels are added and read. Starting readout before the strobe light emission corresponds to resetting each pixel before the light emission.

In step S110, the second group of pixels 50b
It is determined whether or not the amount of strobe light emission exceeds a predetermined value based on the output from. If the MPU 27 determines that the strobe light emission amount exceeds the predetermined value, the MPU 27
By sending a stop signal to 0, the strobe light emission is forcibly terminated, or the exposure is terminated (the charge accumulation of the first group of pixels 50a is stopped or the charge is discharged). On the other hand, if the MPU 27 determines that the flash emission amount has not exceeded,
In step S113, the process waits until the scheduled exposure time ends, and the exposure operation is completed in step S114.

On the other hand, if the MPU 27 determines that strobe light emission is unnecessary because the subject illuminance is high, the MPU 27 starts exposure in step S112 without performing strobe light emission, and ends the scheduled exposure time in step S113. The exposure operation is completed in step S114.

Thereafter, in step S115, the MPU 27
Reads an image signal from the first group of pixels 50a and stores it 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 is as follows. After the flash is fired, the second flash read out after the flash is triggered.
The pixel signals of the group of pixels 50b are integrated for each clock. The integrated value is compared with a preset threshold (light control level) in the comparator 7, and when the threshold is reached, a stop signal is output to the image sensor control circuit.
The exposure is terminated by closing the electronic shutter of the image sensor.

As a method of extracting a signal, an output may be extracted in a state where a signal line is directly connected from a pixel that has been reset and cleared once, instead of reading the signal every clock. In this case, the strobe light is integrated by the pixel. A signal obtained by adding the outputs of the pixels (light receiving elements) is preferably compared by the comparator 7. As will be described later with reference to FIG. 14, in some cases, the second group of pixels 50b can be selected. For example, a pixel receiving light from a high-luminance subject is referred to as a second pixel.
In the case of a group of pixels, the intensity of strobe light may not be negligible. When the output of such a pixel is used for dimming control, an error may occur in the detection of the amount of strobe light. In order to eliminate this, the second group of pixels is scanned in advance to detect whether or not the high-luminance object light is received, and if so, the pixel is excluded so as not to be used as a light receiving element. It is.
However, since the strobe light emits relatively strong light in a short time, the influence of normal light within the light emission time may be negligible, and in that case, the selection operation may be omitted.

In this embodiment, when the output of the pixels of the second group reaches a preset dimming level, a stop signal is output from the comparator 7 and input to the image sensor control circuit 23. Thereby, the image sensor control circuit ends the exposure of the image sensor. The above functions can be integrated on the image sensor 22. The setting of the dimming level and the like may be performed from outside.

When the pixels of the color image sensor are used as the second group of pixels, the BGR filter includes a method of representing green pixels and a method of selecting each BGR pixel in a well-balanced manner. It is possible to mount another color filter only on the second group of pixels, or it is also possible not to mount another color filter.

FIG. 14 is a diagram showing a photographing control flow for explaining a modification of the flash exposure control of FIG. 13 in detail. This modification shows control when light from a high-brightness object such as a light-emitting body such as a light enters the second group of pixels. After the exposure control is completed in step S106 in FIG. 13, the MPU 27 determines in step S201 in FIG. 14 whether the second group of pixels 50b that has received light from the high-luminance subject should be divided. When determining that the pixels should be divided, the MPU 27 scans the second group of pixels 50b at high speed (checks the output of each pixel). If the output of any of the pixels is lower than a specified value (threshold), it is determined that the light is not from a high-luminance subject, and MPU2
7 registers such a pixel. On the other hand, if the output of any of the pixels is equal to or more than a specified value (threshold), it is determined that the light is from a high-luminance object, and the MPU 27 excludes such pixels and performs strobe light control. The threshold value may be a fixed value. However, when there are three or more pixel signals, an average value may be obtained and pixel signals far from the average value may be excluded.

In step S206, all the second group pixels 5
0b is completed, or in step S20
1, a second group of pixels 50 receiving light from a high-brightness subject
When it is determined that there is no need to divide b, the MPU 27
Exposure is started in step S207, and step S208
Then, the pixels 50b of the second group are reset, and Step S20
In step 9, the strobe 2 is caused to emit light via the strobe light emitting circuit 120. Then, in step S210, the MPU 27
By reading out the signal output from the second group of pixels 50a,
In step S211, the signal is integrated, and the integrated value is compared with a specified value (threshold value). If the integrated value is exceeded, the strobe light emission is stopped in step S214, or the exposure is completed (the first group of pixels 50a). Stop charge accumulation or discharge)
If not, after waiting for the scheduled time to elapse in step S213, the exposure ends in step S114 in FIG.

In the present embodiment described above, the first group of pixels 50a for acquiring image data and the second group of pixels 50b for acquiring data for exposure control are made independent. However, if the second group of pixels 50b is a so-called non-destructive readable pixel, the amount of the accumulated charges can be confirmed without taking out the accumulated charges. It can be used as a part of data, thereby improving image quality. or,
The integration may be started after the discharge of the charges of the pixels 50b of the second group is completed and after the charges of the pixels 50a of the first group can be output.

As described above, since the charge of an arbitrary pixel can be read out by using the CMOS type image pickup device, a part of the pixel of the image pickup device 22 is replaced with the exposure control data acquisition data as in this embodiment. This eliminates the need for a light-receiving element for measuring the luminance of the field, which is provided in the prior art, thereby reducing costs and increasing the degree of freedom in external design. You.

Next, another embodiment of the CMOS type image pickup device will be described with reference to FIGS. FIG.
1 is a circuit configuration diagram of a CMOS image sensor according to the present embodiment. As shown in FIG. 15, this CMOS image sensor has a two-dimensional array sensor configuration, in which unit pixels having the above-described structure are arranged in a matrix in the column direction and the row direction.

A vertical shift register 102, which is a circuit for generating a vertical scanning signal (VSCAN), is disposed on the left side of the pixel area. Unit pixels 10 arranged in the row direction for each row
To the gate of the MOS transistor Qxxa in 0, the vertical scanning signal supply lines v1 and v2 that are output one by one from the vertical shift register 102 are respectively connected.

A horizontal shift register 103, which is a circuit for generating a horizontal scanning signal (HSCAN), is arranged below the pixel area. Unit pixels 10 arranged in the column direction for each column
The source of the MOS transistor Qxxa in 0 is connected to different vertical output lines h1 and h2 for each column. Each of the vertical output lines h1 and h2 is a switch M which is different for each column.
The drains of the OS transistors Q01 and Q02 are connected one by one. The gates of the switches Q01 and Q02 are connected to a horizontal shift register 103 which is a circuit for generating a horizontal scanning signal (HSCAN).

Further, a timing generator 101 which is a circuit for generating a shutter signal (VSHT) and a drain voltage (VDD) is arranged on the right side of the image area. Drain voltage supply lines from a timing generator 101, which is a drain voltage (VDD) generation circuit, are connected to drains of MOS transistors in all the two-dimensionally arranged unit pixels 100. further,
MOS in all unit pixels 100 arranged two-dimensionally
A shutter signal supply line from a timing generator 101 which is a circuit for generating a shutter signal (VSHT) is connected to a gate of the transistor.

The sources of the switches Q 01 and Q 02 are connected to an amplifier 105 through a common constant current source 104, and the output of the amplifier is connected to an output 106. That is, the source of the MOS transistor Qxxb in each unit pixel 100 is connected to the transistors Qxxa and Q01.
, And Q02 to the constant current source 104 to form a pixel-based source follower circuit. Therefore, each MOS
The potential difference between the gate and the source and the potential difference between the bulk and the source of the transistor Qxxb are determined by the connected constant current source (load circuit) 104.

The vertical scanning signal (VSCAN) and the horizontal scanning signal (HSCAN) are used to sequentially turn on the MOS of each unit pixel.
By driving the transistor Qxxb, a video signal (Vout) proportional to the amount of incident light is read. As described above,
Since the unit pixel 100 includes the light receiving diode Dxx and the MOS transistors Qxxb and Qxxa, the pixel portion can be created by using the CMOS technology. Therefore, the pixel portion can be formed on the same semiconductor substrate as the peripheral circuits such as the scanning circuits 101 to 103 and the constant current source 104.

The feature of this element structure is that exposure can be started and ended for all pixels at the same time as in a progressive scan type CCD image pickup element. This is effective when performing accurate exposure control using a light source such as a strobe that emits light only for a short time. In a normal CMOS type image pickup device, reading is performed sequentially one pixel at a time or one line at a time. In this case, there is no problem in ordinary exposure, but when performing exposure by short-time light emission such as strobe light, exposure conditions are limited. That is, light emission must be started while all pixels are performing exposure, and light emission must be terminated. Exposure cannot be terminated by stopping the transfer of charges as in the case of this element.

FIG. 16 shows a case where the sensor of FIG.
9 is a timing chart of each input signal for operating the CMOS image sensor according to the present embodiment in relation to an example in which is used as a second group of pixels. Using a p-type well region,
In addition, it is applied when the optical signal detection transistor Qxxb is an nMOS. The element operation can be repeatedly performed in the order of a sweeping period (initialization), an accumulation period (exposure period), a reading period, a sweeping period (initialization), and so on.

The operation of the above configuration will be described in detail.
There are four voltage values: 0 V, VL (for example, about 1 V), VM (for example, about 3 V), and VH (for example, about 5 V).
In the sweeping period, VH is added to VDD and VSH (t
0). This makes it possible to sweep out charges accumulated in the carrier pocket below the gate of the photodiode Dxx and the MOS transistor Qxxb. After the initialization is completed, VDD is set to VM and VSH is set to VL (t1).
As a result, charges are generated in accordance with the amount of light incident on the photodiode, and the generated charges flow into a carrier pocket formed below the gate of the MOS transistor. The exposure is started from here. The strobe light is emitted in the latter half of the exposure period (t3). At time t2 slightly before time t3, I
11, reading of signals from D11 is started. Using h1, a signal is read from D11 at regular time intervals and integrated. When the integrated value reaches a certain threshold, that is, when the amount of light emission of the strobe light reaches an appropriate value, the exposure is terminated. At this time, this is realized by changing VSH from VL to VM (t4). As a result, during the exposure period, the MOS transistor Qxxb
The flow of charges flowing into the carrier pocket below the gate of the gate stops, and the exposure ends. Thereafter, reading is started by operating the horizontal shift register and the vertical shift register. For example, H1 and V1 are each set to 0V
, The signal from Q11b can be read. Similarly, signals of all pixels can be read out by a combination of Hx and Vx. After reading out all the signals, VDD and VSH are set to VH again to perform initialization to prepare for the next exposure. After a certain period of time, or after the strobe light emission ends, a signal from each pixel is read. At this time, since the signal from the pixel including D11 has already been read, little charge remains. The above example uses a four-pixel sensor, and uses one pixel as a light receiving element. This is basically the same even if the number of pixels increases. However, since there are a plurality of pixels in the second group, an address is set so that the read transistor of each pixel is turned on so that signals from these pixels can be read simultaneously.
The read signals are added and read. It is also conceivable that the output signal after the addition becomes too large and exceeds the dynamic range of the output amplifier. In this case, it is possible to read out a signal for one screen by dividing the second group of pixels one by one or several pixels, not all at the same time, but by increasing the clock for reading. . The output signals are externally added and integrated. The basic structure of the above-mentioned CMOS image sensor is disclosed in, for example, JP-A-11-195778, and will not be described in detail below.

Although the present invention has been described with reference to the embodiments, it should be understood that the present invention should not be construed as being limited to the above embodiments, and that modifications and improvements can be made as appropriate. is there. For example, the present invention can be used not only for strobe light control but also for general exposure control. In addition, the present invention is not limited to an electronic still camera, and can be applied to various imaging apparatuses such as a radiation imaging apparatus.

It is also conceivable to use only the pixels on which the G filter is mounted as a second group of pixels for acquiring 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 metering, the pixels of the second group are selected from the center pixel of the image pickup unit, and in the case of average photometry, the second group of pixels is selected from the entire image pickup unit. A group of pixels can also be selected.

A terminal for acquiring image data and a terminal for acquiring exposure data may be shared, or a strobe light intensity integration output terminal may be separately provided. When scanning and reading out the signals from the pixels of the second group, the signals can be read out separately for each part. For example, since an important subject is often located at the center, it may be read out from the center, read out by column or row, or read in a spiral. By providing two memories (charge storage units) in one pixel and separately recording the image charge before the flash emission and the image charge after the flash emission, the data before the light emission can be acquired intact. In order to control the strobe light emission time, an appropriate amount of light can be estimated in advance, and the light emission can be performed earlier than the exposure end time.

[0073]

According to the image processing system of the present invention, it is possible to provide a photographing apparatus capable of photographing under more appropriate photographing conditions while keeping costs low.

[Brief description of the drawings]

FIG. 1 is an equivalent circuit diagram of a CMOS image sensor according to an 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 illustrating an arrangement of pixels in an imaging unit;

FIG. 4 is a wiring diagram for extracting signals when the imaging unit of FIG. 3 is used.

FIG. 5 is a schematic configuration diagram illustrating an arrangement of pixels in an imaging unit according to a modification of the present embodiment.

FIG. 6 is a wiring diagram for extracting a signal when the imaging unit of FIG. 5 is used.

FIG. 7 is a diagram showing an arrangement relationship between pixels and filters.

FIG. 8 is a diagram showing another example of the arrangement relationship between pixels and filters.

FIG. 9 is a diagram showing a schematic configuration of an electronic still camera which is an example of a photographing apparatus according to the present embodiment.

FIG. 10 is a strobe light emission characteristic diagram.

FIG. 11 is a diagram illustrating strobe light emission characteristics when (subject distance) × (aperture) is small.

FIG. 12 is a diagram illustrating strobe light emission characteristics when (subject distance) × (aperture) is large.

FIG. 13 is a diagram illustrating a photographing control flow according to the present embodiment.

FIG. 14 is a diagram showing a shooting control flow for explaining a modification of the flash exposure control of FIG. 13 in detail.

FIG. 15 is a circuit configuration diagram of a CMOS image sensor according to the present embodiment.

FIG. 16 is a timing chart of the present embodiment.

[Explanation of symbols]

 2 Strobe 7 Comparator 22 CMOS image sensor 23 Image sensor control circuit 27 MPU 50 Imager 50a First group of pixels 50b Second group of pixels 51 Timing generator 52 Vertical shift register 53 Horizontal shift register

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification FI FI Theme Court ゛ (Reference) H04N 5/235 H01L 27/14 A 5/335 D (72) Inventor Kyozushi Miyata Sakuracho, Hino City, Tokyo 1 Konica Corporation (72) Inventor Hiroshi Kibayashi 1 Sakuracho, Hino-shi, Tokyo 1 Konica Corporation (72) Inventor Jun Takayama 2970 Ishikawacho, Hachioji-shi, Tokyo Konica Corporation (72) Invention Person Koichi Sato 2970 Ishikawa-cho, Hachioji-shi, Tokyo Inside Konica Corporation (72) Inventor Takeshi Kitada 2970 Ishikawa-cho, Hachioji-shi, Tokyo Inside Konica Corporation F-term (reference) 2H002 DB01 HA04 4M118 AA10 AB01 BA14 CA02 FA06 FA34 FA42 FA44 GC09 GC14 5C022 AB03 AB15 AC42 AC55 AC78 5C024 BX01 CY17 EX12 EX52 GX02 GX21 GY31 5C065 AA01 AA03 BB08 BB30 BB41 BB43 CC03 DD15 DD17 EE05 EE06 GG15 GG32

Claims (5)

[Claims] An image pickup device in which a first group of pixels for imaging a subject image, a second group of pixels for photometry are two-dimensionally arranged, and a color filter, wherein light from the subject is An imaging device, wherein the light passes through the color filter and is received by the first group of pixels, but is received by the second group of pixels without passing through the color filter. 2. The color filter according to claim 1, wherein a pixel in two rows and two columns is one pixel.
Each pixel to be a block is structured to be covered with one of the three color filters.
2. The imaging apparatus according to claim 1, wherein when one group of pixels is included, the remaining pixels of the first group are covered with filters of different colors. 3. 3. An image sensor in which a first group of pixels for capturing an image of a subject and a second group of pixels for photometry are two-dimensionally arranged, and a filter of a first color, a second color, and a third color. Wherein the second group of pixels receives a subject image via the first color filter, and receives the subject image via the second color filter. And a third pixel that receives a subject image through the third color filter, and obtains photometric data based on output values of the first, second, and third pixels. Photographing device. 4. The photographing apparatus according to claim 3, wherein the output values of the first, second, and third pixels are weighted to obtain photometric data. 5. The photographing apparatus according to claim 1, wherein the color filters include red, green, and blue filters.