JP3498627B2 - Imaging device and exposure control method thereof - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus having exposure adjusting means and an exposure control method therefor, and more particularly, to an image pickup apparatus attached to a video camera, a digital still camera, a PC and other products, and an exposure control method therefor. It is about.

[0002]

21 is a block diagram of automatic exposure adjustment in an image pickup apparatus disclosed in Japanese Patent Publication No. 5-37595. In the figure, 20 is a lens, 21 is a diaphragm mechanism, and 22
Is a drive circuit, 23 is an imaging device, 24 is a preamplifier,
25 is a variable gain amplifier, 26 is an A / D converter, 27
Is a sync separation circuit, 28 is a switching circuit, 29 is a switching control circuit, 30 is an integrating circuit, 31 is an abnormality determining circuit, and 32 is
Is an average value calculation circuit, 33 is a comparison circuit, and 34 is a target memory.

Next, the operation will be described. The incident light from the subject that enters the lens 20 is photoelectrically converted by the imaging device 23 after the diaphragm of the lens is adjusted by the diaphragm 21 and the amount of light is adjusted, and is output as an imaged video signal. The A / D converter 26 converts the luminance signal in the picked-up video signal into a digital signal and inputs the digital signal to the integrating circuit 30 selected by the switching circuit 28.

The sync separation circuit 27 separates the vertical and horizontal sync signals from the picked-up video signal, and the switching control circuit 2 in the subsequent stage.
Reference numeral 9 controls switching of the switching circuit 28 based on the both synchronizing signals and the clock signal used for controlling the image pickup device 23, and switches corresponding to each photometric area divided as shown in FIG. That is, FIG.
The A / D converter conversion value of the picked-up image signal in the area A of FIG.
Each A / D converter conversion value in F is the integrating circuit 30
Input from B to the integrating circuit 30F.

The integrating circuits 30A to 30F integrate one field of the input video signal and output it to the abnormality determining circuits 31A to 31F. The abnormality determining circuit 31 deletes the integrated value of the area including the low brightness below a certain level and the high brightness above a certain level from the input integrated value, and the average value calculating circuit 32 calculates the average brightness value.

The comparison circuit 33 compares with a predetermined brightness level stored in the target memory 34 in advance, and the diaphragm 21 and the diaphragm 21 so that the brightness average value approaches the brightness level defined in the target memory 34. Variable gain amplifier 25
To control.

In the conventional image pickup apparatus, the comparison circuit 3 is arranged so that the integrated value of the video signal approaches a constant level as described above.
3 is used to perform exposure adjustment based on the comparison result of the comparison circuit 33, that is, TTL (Trough The Lens) photometry is mainly used. Further, in the example shown in FIG. 21, the mechanical aperture is used for the exposure adjustment, but when an image pickup device capable of changing the charge accumulation period is used, the same effect can be obtained even if the accumulation time is changed.

Further, as shown in the block diagram of the image pickup apparatus shown in FIG. 23, in addition to the above-mentioned TTL photometry, a photometric sensor for photometrically measuring the brightness of an externally photographed object is used as in the photometry in a silver halide camera. There is also a method. In FIG. 23, 40 is a photometric sensor lens, 41 is a photometric sensor, and 42 is an A / D.
A converter, 43 is a lens, 44 is a diaphragm, 45 is an imaging device, 46 is a variable gain amplifier, 47 is a drive unit for controlling the opening and closing of the diaphragm 47, and 48 is a microcomputer. The operation of the image pickup apparatus configured as described above will be described.

The amount of incident light collected by the lens 43 is adjusted by the diaphragm 44 to form the image on the image pickup device 45. The variable gain amplifier 46 amplifies the signal output from the image sensor 45 and outputs a video signal. The photometric sensor lens 40 is provided on the photometric sensor 41 by the image pickup device 4
It is provided so as to form an image with the same angle of view as the image formed on the image plane 5. The voltage value output from the photometric sensor 41 changes depending on the amount of incident light, and the output voltage value is digitally converted by the A / D converter 42 and then input to the microcomputer 48. The microcomputer 48 inputs the photometric sensor 41
The amount of incident light, that is, the brightness of the object being imaged can be known from the voltage value of. The microcomputer 48 is the photometric sensor 4
The aperture of the diaphragm 44 mechanism and the gain of the variable gain amplifier 46 that are provided in advance so that a constant video signal can be obtained from the value obtained from 1 and the video signal level output from the variable gain amplifier 46 is The exposure is controlled so that it becomes constant.

Although two examples of exposure control of the image pickup apparatus have been described above, most of the automatic exposure controls perform exposure control by the TTL photometry shown in FIG. 21 or the external photometry shown in FIG.

[0011]

Since the exposure control of the conventional image pickup apparatus is configured as described above, in the TTL photometry, the integrated value integrated for each field is compared by the comparison circuit every time and a constant brightness level is obtained. In order to obtain a constant brightness level, it is necessary to make comparisons only according to the aperture value of the diaphragm to obtain a constant brightness level. On the other hand, there is a problem in that the diaphragm operation oscillates if a large value is set for the opening degree in order to shorten the time.

Regarding the exposure control in the external photometry, the lens for the photometric sensor is required to have high precision in order to form an image similar to that of the image pickup device on the photometric sensor. Since the range is narrow, precision is required for exposure control, and it must be configured with consideration for environmental dependence such as the precision of the diaphragm mechanism and the temperature characteristics of the photometric sensor. There was a problem that I was in trouble.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain an image pickup apparatus and an exposure control method therefor which realize highly accurate and high-speed exposure control with a simple circuit configuration. And

[0014]

In an image pickup apparatus according to the present invention, an exposure adjusting means for adjusting an exposure amount of an image pickup using an image pickup element, and an arithmetic means for performing an operation based on a signal obtained from the image pickup element. And a control means for controlling the exposure adjusting means, wherein the control means controls the first exposure from the exposure amount of the first imaging.
The second image pickup is performed by increasing or decreasing the exposure amount by the correction amount of, and whether the second image pickup is overexposure or deficient is determined based on the calculation result of the calculating unit. When it is determined that the second imaging is underexposure when the exposure amount is increased by the first correction amount, the exposure amount is increased by the second correction amount larger than the first correction amount. The exposure adjustment unit is controlled to perform the image pickup of No. 3, and the second image pickup is judged to be overexposed when the second image pickup is the exposure amount increased by the first correction amount from the first image pickup. If so, the exposure adjustment means is controlled so that the exposure amount is reduced by the second correction amount smaller than the first correction amount and the third imaging is performed. When it is determined that the second imaging is overexposure when the exposure amount is reduced by the correction amount of 1 , First to control the exposure adjustment unit to perform the third imaging by reducing only the exposure correction amount larger than the second correction amount, the second imaging is first than the first imaging 1
If the exposure amount is reduced by the correction amount of
When it is determined that the image pickup is insufficiently exposed, the exposure adjustment unit is controlled to increase the exposure amount by the second correction amount smaller than the first correction amount and perform the third image pickup.

Further, in the image pickup apparatus according to the present invention, the exposure adjustment means for adjusting the charge accumulation time of the image pickup element, the calculation means for performing an operation based on the signal obtained from the image pickup element, and the charge accumulation time are set. It is provided with a table in which the addresses are set in order from the longest time to the shortest time, and the control means for controlling the exposure adjusting means. The control means is set to the nth address (n is an integer) of the table. performing a first imaging in the charge accumulation time, the first to determine the excess and deficiency of exposure during imaging based on the calculation result of the calculating means, the exposure at the time of the first imaging is excessive when,
A value m (m is an adjustment
Number) was added (n + m) sets the number locations charge accumulation time
In performing a second imaging, lack exposure during the first imaging
If m is, then m is subtracted from the address n in the table.
Second imaging with charge accumulation time set at address (nm)
It was carried out, based on the calculation result of the calculating means to determine the excess and deficiency of exposure during the second imaging during the second imaging
A exposure is excessive, and at the same time as the second deficiency judgment of exposure of the exposure <br/> the excess determination during the first imaging during imaging, the table (n + 2 × m) performs a third imaging at the set charge accumulation time at the address, the exposed during the second imaging an excessive, and of the second imaging
When the determination of overexposure or underexposure is different from the determination of overexposure or underexposure during the first imaging , the (n + m /
2) The third image is taken at the charge accumulation time set at the address.
If the exposure was insufficient during the second imaging, and
The determination of excess or deficiency in the exposure at the time of the second image pickup is based on the above
When it is the same as the over / under deficiency of the exposure when shooting 1
Charge storage set at address (n-2 × m) in the table
The third imaging is performed during the product time, and the dew during the second imaging is performed.
The exposure is insufficient and the exposure during the second imaging
Excess or deficiency of the exposure is related to the exposure during the first imaging.
If it is different from the excess / deficiency judgment, (nm / m /
2) to control the exposure adjustment unit of the third imaging a row Migihitsuji at the set charge accumulation time at the address.

Further, in the image pickup apparatus according to the present invention, the p address, the (p + 1) address and the (p + 2) address of the table are provided.
Address (p is an integer and the lowest address in the table ≤ p ≤
The charge accumulation time set in the highest address of the table-2) was set to ((charge accumulation time set in p address / charge accumulation time set in (p + 1) address)) = ((p + 1) address There is a relation of charge accumulation time / charge accumulation time set at address (p + 2).

Further, in the image pickup apparatus according to the present invention, the exposure adjustment means includes a circuit for amplifying the signal output from the image pickup element, and the table shows the charge accumulation time and the amplification factor of the amplification circuit when the image is exposed. Are set in order of increasing or decreasing.

Further, in the image pickup apparatus according to the present invention, the exposure adjusting means for adjusting the charge accumulation time of the image pickup element and one screen of the signal obtained from the image pickup element or a part thereof are integrated to obtain an integrated value Σ. Calculating means for calculating, and a table in which the charge storage time is set in order from the upper address of the address so that the length of the time increases or decreases at a constant rate,
And a control unit for controlling the exposure adjustment unit, the control unit performing the first imaging at the charge accumulation time set at the address n (n is an integer) of the table, and the integrated value Σ accumulated by the calculating unit is If it is within the predetermined range, the difference between the constant C and the integrated value Σ is divided by the ratio so that the address value indicating the table value corresponding to the proper exposure value and the table value used in the first imaging are obtained. The exposure adjustment means calculates a difference from the instructed address value, adds or subtracts the value obtained by the calculation as an exposure correction value so that the integrated value Σ approaches the constant C, and performs the next imaging. To control.

Furthermore, in the exposure control method of the image pickup apparatus according to the present invention, the first exposure amount at the time of the first image pickup
The calculation is performed based on the signal obtained by increasing or decreasing the exposure amount by the correction amount of 2 to perform the second imaging, and whether the exposure is excessive or insufficient for the second imaging is determined based on the calculation result. , When the second image pickup is the exposure amount increased by the first correction amount from the first image pickup, and it is determined that the second image pickup is underexposed, the second image pickup is larger than the first correction amount. The second imaging is performed when the third imaging is performed by increasing the exposure by the correction amount of 2 and the second imaging is the exposure that is increased by the first correction amount from the first imaging. When it is determined that the exposure is overexposed, the exposure amount is reduced by the second correction amount smaller than the first correction amount to perform the third image capturing, and the second image capturing is performed by the first image capturing amount than the first image capturing amount. If the second imaging is determined to be overexposure when the exposure amount is reduced by Decreases only exposure amount amount larger than the second correction amount performed third imaging of the second image capturing first
When it is determined that the second image pickup is underexposure when the exposure amount is reduced by the first correction amount from the image pickup of
The exposure amount is increased by the second correction amount smaller than the first correction amount, and the third imaging is performed.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1. FIG. 1 is a configuration diagram of an image pickup apparatus according to Embodiment 1 of the present invention. In the figure, 1 is a CCD which is an image pickup device, 2 is an amplifier for amplifying a video signal, 3 is an A / D converter, 4 is a timing generator (hereinafter referred to as TG) which generates a pulse for driving the CCD 1, and 5 is an image The calculating means for integrating signals, 6 is control means, 7 is a look-up table (hereinafter referred to as LUT) recorded and held in the control means 6, and 8 is a lens.

The operation of the image pickup apparatus configured as described above will be described. The signal output from the CCD 1 is amplified by the amplifier 2 and converted into a digital signal via the A / D converter 3. TG4 is CCD1
Is a circuit for generating the drive pulse of, and the charge accumulation time of the CCD 1 can be changed by changing the pulse interval of the drive pulse. Since changing the charge storage time is equivalent to adjusting the amount of light incident on the CCD 1, the exposure of the image pickup device can be adjusted. The arithmetic means 5 integrates the digital video signals input from the A / D converter 3 for one field or more, and outputs the integrated value Σ to the control means 6. The calculating means 5 may integrate all areas in the video signal, or may integrate a part thereof (for example, only the central portion (A) shown in FIG. 22 in center-weighted photometry). The controller 6 controls the CCD 1 based on the integrated value Σ calculated by the calculator 5 and the LUT 7.
The charge accumulation time is determined, and the drive pulse interval of the TG4 is controlled so that the CCD 1 reaches the charge accumulation time. The control means 6 can be realized by a microcomputer in an ordinary image pickup device or the like.

With the above configuration, C is set so that the average value of the video signal obtained from the A / D converter 3 is always constant.
The storage time of CD1 can be controlled, and automatic exposure control can be realized. Here, as the means for adjusting the exposure amount, an electronic shutter for adjusting the charge accumulation time of the image sensor is used, but if a diaphragm mechanism etc. is attached,
The same exposure adjustment can be performed by controlling the diaphragm mechanism to adjust the amount of light incident on the lens 8.

The operation of the control means 6 will be described. Control means 6
Has a LUT 7 as shown in FIG. 1 in advance, and the LUT 7 stores the charge accumulation time and the address in association with each other. FIG. 2 is a diagram illustrating the LUT 7. In the figure, the LUT 7 stores N kinds of charge accumulation times corresponding to addresses 1 to N in a table, and each charge accumulation time corresponds to the brightness of one of the brightnesses of the N kinds of objects. It is the charge accumulation time for proper exposure. For example, when the table value T = 1 / S at the address 1 is the charge storage time corresponding to the brightness 10 lux of the subject (hereinafter, the looks is referred to as lx), the table value at the address 2 is the brightness 10 of the subject. ^If the charge accumulation time corresponds to ^k (lx) (where k is a constant), the value is 1 / (S ^k ).
Becomes In the LUT 7 of FIG. 2, the table is set so as to correspond to the case where the brightness of the subject, which is the optimum exposure for the charge accumulation time, increases exponentially, and logarithmically in the exposure control of the imaging device. Since many numerical values are handled, the value of the above charge accumulation time is easy to handle. Here, in LUT7, 10 (l
When it is desired to include the brightness from x) to 100,000 (lx), k = (100000/10) ^{1 / N} may be set.

FIG. 4 and FIG. 5 exemplify the relationship between the charge accumulation time relating to exposure control and the illuminance of the subject. 6 and 7
3 is a flowchart illustrating an operation of the image pickup apparatus according to the first embodiment. The operation will be described below with reference to the flowcharts shown in FIGS.

First, the control means 6 in FIG. 1 performs initial setting for starting image pickup (P1 in FIG. 6). For example, in order to perform the initial setting of the charge storage time of the CCD 1 of FIG.
The address value n0 of the LUT 7 as shown in is set to the variable n which means the address value of the LUT. That is, as the initial value of the charge accumulation time, the charge accumulation time T at the address n0
_n0 is selected. Further, 0 is substituted for the variable i that stores the number of times of exposure correction in order to start imaging. Here, as an example, the charge storage time T _n0 of the initial value is set to an intermediate value (= midL) within the range of the illuminance of the subject that is the target of exposure control, but the present invention is not limited to this.

Next, the control means 6 in FIG. 1 outputs the previously selected charge accumulation time T _n0 to the TG 4, and the TG 4 drives the CCD 1 so as to pick up the current image at the charge accumulation time T _n0 ( P2 of FIG. 6).

The video signal _{picked up} at the charge storage time T _n0 is passed through the amplifier 2 and the A / D converter 3 to the calculation means 5
Are integrated and the integrated value Σ is output to the control means 6. The control means 6 inputs the integrated value Σ (P in FIG. 6).
3) Compared with the value provided in advance, more specifically, the integrated value ΣAPL that the arithmetic means 5 will output when the video signal is the average value level (APL) to be converged (FIG. 6).
P4). If the integrated value Σ obtained here is larger than the integrated value ΣAPL, it means that overexposure has occurred. To limit the amount of incident light, the charge accumulation time T of the CCD 1 is shortened, that is, the shutter speed is increased (see FIG. 2). It is necessary to reduce the charge accumulation time T of (1) to reduce the exposure amount). Further, when the integrated value Σ is smaller than the integrated value ΣAPL, it means that the exposure is insufficient, and the charge accumulation time of the CCD 1 is lengthened, that is, the shutter speed is decreased (the charge accumulation time T in FIG. It is necessary to increase the amount). Therefore, in the present embodiment,
The following processing is performed.

When the integrated value Σ is larger than the integrated value ΣAPL, the exposure correction value nc is obtained as shown in P6 of FIG. More specifically, a value obtained by subtracting the address n stored in the variable n from the maximum address value nmax (address N in the table shown in FIG. 2) is set as the exposure correction value nc. Note that the address n at this point (P6 in FIG. 6) is the address value of the LUT in which the charge accumulation time used for the current imaging is set. Next, a new address n is obtained by adding the calculated exposure correction value nc to the address n (see P in FIG. 6).
7) Let the charge storage time at this new address n be the charge storage time at the time of the next imaging.

Here, the correction in the direction of increasing the address (corresponding to the correction of shortening the charge accumulation time in the LUT shown in FIG. 2) is set to up, and conversely, the correction in the direction of decreasing the address (also the charge accumulation time is (Corresponding to correction to lengthen) do
The direction of correction is stored as wn. For example, as described above, a value obtained by subtracting the address n of the LUT of the charge accumulation time used for the current imaging from the maximum value nmax of the address is set as the correction value nc (P6 in FIG. 6), and the correction value n is set to the address n.
In such a case, the correction direction is u
The variable up, which is p and is provided in the control means 6 that means the direction of correction, is set to 1, and the variable down is set to 0 (FIG. 6).
P9).

The charge storage time is set as shown in FIG.
Assuming that the charge storage time in the initial image pickup corresponds to midL (corresponding to an intermediate value of the illuminance range of the subject imaged by the image pickup apparatus), it is obtained by the processing of P6 and P7 in FIG. 6 described above. The charge accumulation time corresponding to the corrected (n + nc) address n is the charge accumulation time at the time of the next image pickup. Here, nm is an example of the exposure correction value.
Although ax-n is used, a fraction of the exposure correction value, for example, (nmax-n) / 2 or the like does not cause any problem, and similar effects can be obtained.

On the contrary, when the integrated value Σ is smaller than the integrated value ΣAPL, the LU of the charge accumulation time used for the current imaging is calculated.
A value obtained by subtracting the minimum value nmin of the address (address 1 in the LUT shown in FIG. 2) from the address n of T is set as the exposure correction value nc (P10 in FIG. 6). Next, the exposure correction value nc is subtracted from the address n (P11 in FIG. 6), and the charge accumulation time at that address value is set as the charge accumulation time at the next image pickup. When the above process is performed, the correction direction is down, and up is set to 0 and down is set to 1 (P12 in FIG. 6).

After performing the above-described processing, the exposure correction is set to 1
Once, the variable i for storing the number of exposure corrections is set to 1 (P13 in FIG. 6).

Next, the charge accumulation time Tn corresponding to the address n for which exposure correction has been performed in P7 or P11 in FIG. 6 described above.
An image is taken at (P2 in FIG. 6). Next, the integrated value Σ obtained by the image pickup is obtained (P3 in FIG. 6), and the process shifts to P14 in FIG. 7 from the second exposure correction (P4 in FIG. 6).
Similar to P5 in FIG. 6, in P14 in FIG. 7, the obtained integrated value Σ is compared with the integrated value ΣAPL (P1 in FIG. 7).
4).

From the second exposure correction, the correction direction is confirmed (P15 or P20 in FIG. 7). Integrated value Σ is integrated value Σ
If it is larger than APL, it is necessary to perform exposure correction (correction for shortening the charge accumulation time) in the up direction because of excessive exposure as described above. First, it is determined whether or not the direction of the previous exposure correction is up (P15 in FIG. 7), and if it is up, the exposure correction in the same direction is performed this time, and the direction of the previous exposure correction is up. If not, that is, if it is down, the direction of the exposure correction is reversed. Then, in the case of exposure correction in the same direction, the previous exposure correction value nc is doubled (P16 in FIG. 7), and the address n (that is, the address value of the charge accumulation time used in the current imaging) is doubled. The exposure correction value nc is added, and this is set as a new address n (P18 in FIG. 7). When the direction of the exposure correction is reversed, the previous exposure correction value nc is halved (P17 in FIG. 7), and the address n (that is, the address value of the charge accumulation time used in the current imaging) is concerned. Add the 1/2 exposure compensation value nc,
This is set as a new address n (P18 in FIG. 7). Then, since the up exposure is corrected, up is set to 1 and dow
n is set to 0 (P19 in FIG. 7).

On the contrary, when the integrated value Σ is smaller than the integrated value ΣAPL, the exposure is insufficient as described above, and d
It is necessary to perform exposure correction (correction that lengthens the charge accumulation time) in the down direction. First, it is determined whether or not the direction of the previous exposure correction is down (P20 in FIG. 7), and if it is down, the exposure correction in the same direction is performed this time, and the direction of the previous exposure correction is down. If not, that is, if it is up, the direction of the exposure correction is reversed. Then, in the case of exposure correction in the same direction, the previous exposure correction value nc is doubled (P21 in FIG. 7) and doubled from the address n (that is, the address value of the charge accumulation time used in the current imaging). The exposure correction value nc is subtracted, and this is set as a new address n (P23 in FIG. 7). When the direction of exposure compensation is reversed, the previous exposure compensation value nc is halved (see P in FIG. 7).
22), the exposure correction value nc multiplied by 1/2 is subtracted from the address n (that is, the address value of the charge accumulation time used in the current imaging), and this is set as a new address n (P23 in FIG. 7). . Then, since the down exposure correction is performed, u
p is set to 0 and down is set to 1 (P24 in FIG. 7). As an example of the process of P22 of FIG. 7 and the process of P23 of FIG. 7, a process of multiplying nc by 2 or 1/2 is shown, but this is advantageous in performing high-speed exposure control from the viewpoint of easy handling. Is. Especially, EV (Expo)
It is particularly easy to handle in the exposure control by "SureValue".

Then, the next image pickup is carried out at the charge accumulation time Tn corresponding to the address n for which the exposure correction was carried out at P18 or P23 in FIG. 7 (P2 in FIG. 6). The integrated value Σ obtained by the image pickup is obtained again (P3 in FIG. 6), and the same exposure correction process is repeated thereafter.

In the image pickup apparatus of the first embodiment, when the direction of the current exposure correction is reversed from the direction of the previous exposure correction as shown in FIG. 4, the amount of the current exposure correction is set to the value of the previous exposure correction. Half the amount. For example, in the case shown in FIG. 4, assuming that the first exposure correction amount is the nc step, the exposure correction amount is sequentially reduced to nc / 2, nc / 4, nc / 8. In this way, the exposure correction can be performed with high accuracy by decreasing the amount of the exposure correction as the proper exposure is approached, and the time until the proper exposure value is obtained can be shortened.

On the contrary, as shown in FIG. 5, when the direction of the current exposure correction is the same as that of the previous exposure correction, the current exposure correction amount is set to be twice the previous exposure correction amount. This makes it possible to quickly obtain the proper exposure value when the proper exposure and the current exposure setting are greatly different from each other or when the illuminance of the subject is greatly changed. For example, as shown in FIG. 5, even if the illuminance of the subject fluctuates greatly when the amount of exposure correction is nc / 8 steps, nc / 4, nc / 2, n
By increasing the amount of exposure compensation in sequence with c steps,
Can quickly follow changes in subject illuminance.

When the address n exceeds the upper limit of the address value of the LUT, the address n is set to the maximum address value, and when the address n is lower than the lower limit, the processing concerning the upper and lower limits of the address n is set to the minimum address value. Although not described, it goes without saying that it is necessary to add it to the processing in the flow chart if necessary.

In the first embodiment, the example in which the exposure correction is performed for each image pickup is shown, but the present invention is not limited to this, and the exposure correction may be performed once for a plurality of image pickups. Good. For example, three times of imaging may be set as one block, and exposure correction may be performed once for each block. Furthermore, in the process shown in P3 of FIG.
Not only this time, but the calculation may be performed using the information obtained by imaging a plurality of times such as the previous time and the time before the last time.

Embodiment 2. FIG. 8 is a configuration diagram illustrating an imaging device according to the second embodiment of the present invention. Figure 8
1, the same reference numerals as those in FIG. 1 indicate the same or corresponding portions. In FIG. 8, 9 is a D / A converter. The second embodiment differs from the first embodiment in that the gain of the amplifier 2 can be controlled by the control means 6 via the D / A converter 9.

The operation of the image pickup apparatus configured as shown in FIG. 8 will be described. In the first embodiment, the exposure control is performed by controlling the charge storage time of the CCD 1. On the other hand, in the image pickup apparatus according to the second embodiment shown in FIG. 8, the gain of the video signal can be changed by controlling the gain of the amplifier 2 in addition to the control of the CCD 1, and thus the average of the video signals can be changed. It is possible to control the level APL.

The charge accumulation time of the CCD 1 and the control of the amplifier 2 relating to the automatic exposure control will be described below. Similar to the first embodiment, the charge storage time (shutter speed) of the CCD 1 and the gain of the amplifier 2 corresponding to the brightness of N kinds of subjects are stored in the control unit 6 of FIG. 8 as a LUT (look-up table) 7. It is provided. FIG. 9 exemplifies the lookup table.

FIG. 10 is a view for explaining an example of the relationship between the charge storage time T set in the LUT 7 shown in FIGS. 8 and 9, the gain G of the amplifier 2 and the object illuminance. As shown in FIG. 10, when the illuminance of the subject is large (for example, area B in FIG. 10), the gain of the amplifier 2 is a constant value Gtyp (G0 in FIG. 9), and the exposure amount is adjusted by adjusting the charge accumulation time of the CCD 1. It is performed by controlling T. On the other hand, when the subject is dark or the like, sufficient exposure cannot be obtained only by lengthening the charge accumulation time T of the CCD 1 (for example, area A in FIG. 10).
For example, the exposure amount is adjusted by changing the gain G of the amplifier 2.

In the range in which the exposure amount can be adjusted by adjusting the charge storage time of the CCD 1 shown in FIG. 6, the exposure adjustment is performed by controlling the charge storage time according to the brightness of the subject. However, with this alone, the maximum charge accumulation time that can be taken by the CCD 1 is the lowest subject illuminance for which exposure adjustment is possible, and therefore the charge accumulation time cannot be lengthened for a darker subject. Therefore, in the second embodiment, the exposure of a dark subject as described above is adjusted by increasing the gain of the amplifier 2.

In the LUT 7 shown in FIG. 9, the gain of the amplifier 2 is G0 until the charge accumulation time of the CCD 1 becomes the longest (1 / S), and for a darker subject, the gain G0 is an exponent by a power of k. The table value is set so that it will increase. LUT7 provided in this way
The operation of the control means 6 using is shown as a flow chart in FIGS. The processing procedure of the flowchart shown in FIG. 12 is the same as that of the flowchart of FIG. 7 shown in the first embodiment. Therefore, only different points will be described here. In the flowchart shown in FIG. 11, the address n0 of the LUT 7 is set to the address n as the initial setting, and the charge accumulation time T _n0 and the gain G0 corresponding to the initial address n0 are set to Tn and Gn, respectively.
Is selected as the initial value (P1 in FIG. 11). Further, at the time of image capturing, the image is captured with the charge accumulation time Tn and the gain Gn (P2 in FIG. 11). Other processes are the same as those in the first embodiment. By controlling the exposure as described above, it is possible to adjust the exposure corresponding to the illuminance of a wide range of subjects.

As described above, the image pickup apparatus according to the second embodiment is provided with the amplifier that amplifies the output signal of the image pickup element, and the charge accumulation time of the image pickup element is adjusted by adjusting the gain of the amplifier. It is possible to perform an appropriate exposure adjustment even for a dark subject that could not be sufficiently adjusted by just adjusting the exposure.

Embodiment 3. Embodiment 3 according to the present invention
In the image pickup apparatus of No. 2, in the exposure control shown in the first and second embodiments, the integrated value Σ accumulated by the calculation means 5 shown in FIGS. 1 and 8 is k1 <Σ <k2 (where k1 When <APL <k2) (1), the control unit 6 performs the processing described later. Here, k1 and k2 in the equation (1) are predetermined constants, and CCD1
It is determined in consideration of the hardware limitation of the computing means 5. For example, "the maximum value of the integrated value Σ that can be integrated by the computing unit 5", "the integrated value Σ of the computing unit 5 when the output signals of all the pixels of the CCD 1 are saturated", or "the output signals of all the pixels of the CCD 1 are When the gain of the amplifier 2 is maximized at the time of saturation, k1 and k2 are determined based on the integrated value Σ of the calculation means 5. Hereinafter, the maximum value of the integrated value Σ of the calculation means 5 based on such determination criteria of k1 and k2 will be referred to as Σmax.

A specific example of how to determine k1 and k2 will be shown. For example, the maximum value of the obtained video signal level is defined as 100%, and the APL (average value level at which the video signal should converge) of the video signal at the proper exposure is 50%. At this time,
If the integrated value Σ of the calculating means 5 obtained when the video signal level is maximum (100%) is Σ100% and the integrated value Σ of the calculating means 5 at the proper exposure is Σ50%, Σ50% = 0. The relationship of 0.5 × Σ100% holds. Then, for example, k1 = 0.2 × Σ100%, k2
= 0.8 × Σ100%, k1 and k2 are set so as to sandwich the integrated value Σ50% at the time of proper exposure. Note that Σ100% here is an example of Σmax described above.

The control means 6 determines whether or not the integrated value Σ integrated by the calculation means 5 for the picked-up video signal satisfies the above equation (1), so that the exposure amount of the picked-up image is appropriate. To see if it is close to. For example, when the integrated value Σ of the imaged video signal satisfies the equation (1), it can be known that the charge storage time and the amplifier gain used for imaging are close to the values at the proper exposure.

When the obtained integrated value Σ satisfies the equation (1), the control means 6 shown in FIGS. 1 and 8 corrects the address value n of the LUT 7 used for the current image pickup by the equation (2). Then, the next image pickup is performed using the corrected address value n. The charge storage time and the gain used for the current imaging are set to the address value n of the LUT 7 before the correction, and the charge storage time and the gain set to the address value n of the LUT 7 after the correction are set to the charge storage time and the gain. Then, the next image is taken. LUT address value _{(atto Bu-less values of the LUT used in the next imaging)} = LUT address value _{(atto Bu-less values of the LUT used in the current imaging) - (Σ-Σ50%)} / k3 ···· (2) Here, k3 Is related to the rate of change of the integrated value Σ of the calculation unit 5 when the address value n of the LUT 7 is increased or decreased by one step, and is a value obtained from the ratio of the table value (charge storage time) of the LUT 7. For example, if the table value when the address value n is m is S _m , and the table value when the address value n is m + 1 which is one step larger than m is S _{m + 1} , k3 =
(S _{m + 1} / S _m −1) × Σmax.

Further, for example, as described in the first embodiment, in the LUT 7 shown in FIG.
When trying to include the brightness up to 0000 (lx), the coefficient k in FIG. 2 is k = (100000/10) ^{1 / N}
And it is sufficient. Here, if N in FIG. 2 is 127, that is, the number of tables in FIG. 2 is 127, k = (10
0000/10) ^1/127 = 1.076, and the table value increases or decreases by 7.6% each time the address value n increases or decreases by one step. Therefore, in this case, k3 = 0.076 × Σma
x.

The integrated value at the target proper exposure is Σ50%
, The obtained integrated value Σ is Σmax (Σ100
%) Between 20% and 80%, it is determined that the exposure value used for the current imaging is an exposure value close to the proper exposure value, and the next exposure value is determined using the formula (2). . The calculation of the equation (2) is performed by calculating the difference between the average value level APL of the video signal to be converged and the average value level of the video signal obtained under the present exposure condition, and calculating the difference as the exposure amount of the LUT. It is divided by the rate of change of (charge accumulation time), and the exposure value used for the next imaging is determined based on the value of the division result. " However, here, "the average value level A at which the video signal should converge"
Instead of "PL", "average value level A at which the video signal should converge"
Using the integrated value ΣAPL that would be output by the calculation means 5 when it was PL, instead of “the average value level of the video signal obtained with the exposure amount of this time”, The output integrated value Σ ”is used, but they are equivalent. By such processing, it is possible to quickly control the exposure value of the imaging device to be near the optimum exposure value.

When the integrated value Σ obtained as described above satisfies, for example, the formula (1), that is, when it is determined that the exposure value at the time of image pickup is close to the proper exposure, the proper exposure value is calculated by the formula (2). By doing so, the exposure value for the next imaging is determined. On the other hand, if the exposure value at the time of image capture deviates greatly from the proper exposure, even if a calculation formula such as formula (2) is used, exposure control can be speeded up and precision improved. Does not contribute much and may even diverge or worsen due to a calculation error or the like. In this case, therefore, the exposure control described in the first and second embodiments is used. As a result, high-speed, high-accuracy and highly-reliable automatic exposure control can be realized.

Fourth Embodiment 8 and 13 to 2
Reference numeral 0 is a diagram illustrating an image pickup apparatus according to Embodiment 4 of the present invention. FIG. 13 is a diagram illustrating an example of the LUT 7 shown in FIG. 8 of the fourth embodiment according to the present invention, FIGS. 14 and 15 are diagrams illustrating the exposure control of the fourth embodiment according to the present invention, and FIGS. FIG. 19 is a flowchart illustrating the operation of the image pickup apparatus according to the fourth embodiment of the present invention, and FIG.
FIG. 6 is a diagram illustrating a relationship among a charge accumulation time, an amplifier gain, and a subject illuminance in the LUT illustrated in FIG. The configuration of the imaging device shown in FIG. 8 can be realized in the same manner as in the second embodiment. The symbol “*” used in FIGS. 13 and 16 and the following description means multiplication, and the symbol “↑” means exponentiation.

In the fourth embodiment, control of the charge storage time by the CCD 1 of FIG. 8 and control of the amplifier 2 for performing automatic exposure control will be described below. Similar to the third embodiment,
CCD in the control means 6 according to the brightness of N kinds of subjects
A table in which the charge accumulation time of 1 (shutter speed) and the gain of the amplifier 2 are set is provided as the LUT 7. FIG. 13 shows the relationship between the charge storage time T and the gain G.
The LUT 7 is configured so that the charge accumulation time becomes longer as the address n becomes larger.
Maximum charge storage time T that can be set in the image sensor 1 at the address
* K ↑ n (T times k to the nth power) is provided. At addresses larger than n, the charge accumulation time T is all (T * k
↑ n), and the gain of the amplifier 2 gradually increases. As shown in FIG. 13, the gain G of the amplifier 2 is G0 at the address n, and is multiplied by k thereafter, and G0 * k, G0
* K ↑ 2, G0 * k ↑ 3. ． ． The table is configured to increase exponentially with. LU as above
In T7, as the address of the address n increases, the charge accumulation time exponentially increases, and after the charge accumulation time reaches the maximum time, the gain of the amplifier 7 exponentially increases. Is configured.

By configuring the LUT 7 as described above,
EV (Exposure Value) 2, 2 is usually used to control the exposure value of the image pickup device.
Since it is provided as * 1.414, 2 * 1.414 ↑ 2, 2 * 1.414 ↑ 3, ..., it is easy to handle the value.

In the LUT 7 shown in FIG. 13, when a subject having a constant illuminance is imaged, the exposure amount increases as the address address increases. Also, now in FIG.
It is assumed that the number of addresses of the LUT 7 shown in is N = 255. The charge accumulation time and the gain of each are provided with the charge accumulation time and the gain of which the proper exposure is provided corresponding to the brightness of the subject in 255 steps. Assuming that the table value at the address is the charge storage time T and the gain G corresponding to the brightness 100000 (lx) of the subject, the table value at the second address is 100000 / k (lx).
The charge accumulation time and the gain value correspond to (where k is a constant). The brightness of the subject is set to increase exponentially, and the exposure control of the image pickup apparatus is exponentially logarithmic, so the value is easy to handle. For example, in LUT7, 1 (lx) to 10000
To include brightness up to 0 (lx), k = (10
0000/10) ^1/256 = 1.046, so LU
Each value is set to T7 so that the proper exposure is obtained corresponding to the brightness of the subject whose brightness increases by 4.6%. For example, 1 when the charge storage time is 0
Assuming 0 μsec, the address 1 is 10.46 μs
ec (10 * 1.046), address 2 is 10.9
It becomes 4 μsec (10 * 1.046 ↑ 2). If the gain at the address n is doubled, the gain at the address n + 1 is 2.092 and at the address n + 2 is 2.188.

14 and 15 show examples showing the relationship between the illuminance of the subject and the address value of the LUT 7 which defines the exposure value for automatic exposure control. FIG. 16 shows a flowchart of the calculation procedure in the control means 6. The operation will be described below with reference to the flowchart shown in FIG.

First, in order to start image pickup, initial setting is performed (P1 in FIG. 16). The variable that determines the charge storage time is Tn, and the variable that determines the gain is Gn. Initial setting is C
The address n0 in the LUT7 is set in order to set the charge storage time of CD1, and the charge storage time Tn and the gain Gn are the charge storage time T * k ↑ n and G in n0.
Select 0. In addition, the number i of exposure control is set to 0 for i to start imaging. Here, as an example, the charge accumulation time of the initial value is set to the intermediate value 127 (or 128) within the range in which the target exposure control is performed.

Next, the control means 6 in FIG. 8 outputs the previously selected charge accumulation time Tn to TG4 and the gain Gn to the amplifier 2
D / A converter 9 that outputs a control signal that determines the gain to
The image is picked up under the above-mentioned image pickup conditions, which is output to (P in FIG. 17).
2).

The video signals picked up under the above-mentioned image pickup conditions are integrated by the calculation means 5 via the amplifier 2 and the A / D converter 3 and the integrated value Σ is output to the control means 6.
The control means 6 inputs the integrated value Σ (P3 in FIG. 17),
It is determined whether or not the obtained integrated value Σ is within the range provided in advance according to the following equation (3). 0.15 * Σmax <Σ <0.85 * Σmax (3) where Σmax is Σmax described in the third embodiment.
According to the above equation (3), it is determined whether or not the imaging condition of the obtained integrated value Σ is a value close to the proper exposure. When the formula (3) is satisfied, it is determined that the image capturing condition is close to the proper exposure, and when the formula (3) is not satisfied, it is determined that the image capturing condition is not close to the proper exposure (FIG. 17). P4).

When the integrated value Σ obtained by the above determination is out of the range provided in advance, the number of times of exposure control is determined by checking the value of i. When i = 0, the first exposure correction process is determined (P5 in FIG. 17).
Next, it is compared with the integrated value ΣAPL of the signal level obtained when the average value level APL of the video signal to be converged (FIG. 1).
7 P6). If the integrated value Σ obtained here is smaller than ΣAPL, it means that the exposure is insufficient, and it is necessary to lengthen the accumulation time of the CCD 1 or increase the gain in order to limit the amount of incident light. Also, the integrated value Σ is APL
When larger, it means overexposed,
It is necessary to shorten the accumulation time of the CCD 1 or reduce the gain.

First, when the integrated value Σ is smaller than APL, the exposure correction value nc is obtained. Maximum address value nmax
The value obtained by subtracting the address n of the LUT of the charge accumulation time used for the previous imaging from (= 255) is the correction value (= 255-
126) (P7 in FIG. 17). Next, the exposure correction value is halved to obtain the exposure correction value (P in FIG. 17).
8).

When the exposure correction value is a large value, if the brightness variation of the image obtained by correcting the exposure is large, the image becomes very unsightly. Therefore, the correction value obtained by the above process is within a certain range. It is determined whether or not there is, and when it is out of the range, a limit is applied within a predetermined range. For example ± 192
When the value of is set as a range, the correction value is selected from any value between -192 and +192,
When it is smaller than the above value, it is set to -192, and when it is larger than the above value, it is set to +192 (P9 in FIG. 17).

Finally, the exposure correction value n calculated at the address n
c is added, and the imaging condition (charge storage time and gain) at that address value is set to the charge storage time and gain in the next imaging (P10 in FIG. 17). Since the integrated value Σ obtained by the previous imaging was smaller than ΣAPL,
On the LUT 7 shown in FIG. 3, by increasing the address value, the correction is performed in the direction of increasing the exposure amount. Further, the correction in the direction of increasing the charge accumulation time (direction of increasing the address address of the LUT 7 in FIG. 13) is set to up,
On the contrary, the correction direction is set with the correction in the direction in which the charge accumulation time is shortened (direction in which the address address of the LUT 7 is small in FIG. 13) as down. That is, when the correction value nc is added to the address n of the LUT used for the above-mentioned imaging, the correction direction is up, and the variable up provided in the control means 6 which means the correction direction is set to 1, down 0
(P11 in FIG. 17).

On the contrary, when the integrated value Σ is larger than ΣAPL, the address n to the minimum value nmin (LUT in FIG. 13) of the LUT of the charge accumulation time used for the image pickup now.
Correction value n is 1/2 of the value obtained by subtracting 0)
c (P13, 14 in FIG. 17). Next, the value of the correction value nc is checked in the same manner as P9 (P15 in FIG. 17), and the exposure correction value nc calculated from the address n is subtracted (FIG. 1).
7 P16). The charge accumulation time and the gain at the exposure-corrected address value n are set as the charge accumulation time and the gain at the next imaging. When the processing in which the exposure correction value nc is subtracted from the address address n is performed as described above, the correction direction is down, up is 0, and down is 1
(P17 in FIG. 17). Here, since the configuration of the table values recorded and held in the LUT 7 is configured as shown in FIG. 13, it is clearly shown that the correction direction is different from that of the first and second embodiments without misunderstanding. deep.

After performing the above-described processing, the exposure correction is set to 1
Once, the exposure correction number i is set to 1 (P in FIG. 17).
12).

Next, an image is picked up at the charge accumulation time Tn and the gain Gn corresponding to the address n of the LUT whose exposure is corrected at P10 or P16 in FIG. 17 (P in FIG. 17).
2). Similarly, the integrated value Σ obtained by imaging is obtained (P3 in FIG. 17), and the process shifts to P18 from the second exposure correction (P5 in FIG. 17). Then, the integrated value Σ and ΣAPL obtained similarly to P6 of FIG. 17 are compared (P18 of FIG. 19).

From the second exposure correction, the correction direction is confirmed (P19, P21, P27, P32 in FIG. 19). First, when the integrated value Σ is smaller than ΣAPL, it is necessary to perform exposure correction in the up direction because of excessive exposure as described above. First, it is determined whether or not the previous exposure correction direction is up (P19 in FIG. 19), and if it is up, the exposure correction in the same direction is performed this time, and the previous exposure correction direction is up. If not, that is, if it is down, the direction of the exposure correction is reversed.

In the case of exposure correction in the same direction, the previous exposure correction value nc is doubled, and the exposure correction value nc is added to the address value n in the current image pickup value. First, it is determined whether up is 0 (P19 in FIG. 19). When up is 0, u in the previous process
Since the process of p has not been performed, it is determined that the direction of the exposure correction is reversed, and the exposure correction value nc is multiplied by 1/2 to calculate the exposure correction value (P20 in FIG. 19). And
1 is substituted for up, which is the direction of correction, and 0 is substituted for down (P22 in FIG. 19). Finally, the range of the exposure correction value nc is checked in the same manner as P9 of FIG. 17, and nc is added to the address address n to perform exposure correction (P26 of FIG. 19).

If up is not 0 in P19, it is determined that the up process was performed in the previous process, and then it is determined whether or not the up process is 1 (P21 in FIG. 19). u
When p is 1, 2 is substituted for up (P2 in FIG. 19)
3). Then, similarly, the processes of P25 and P26 are performed. Also, after substituting 2 for up, if the integrated value Σ is smaller than ΣAPL in the next shooting, that is, if the exposure is insufficient, the exposure correction value nc is doubled (P24 in FIG. 19), and similarly P2 is set.
5, the process of P26 is performed, and this time, the doubled correction value is added. When the direction of the exposure correction is reversed as described above, the correction value is not doubled immediately, but is corrected once with the same correction value and then the processing is performed, which is overcorrection at the time of image pickup, which causes a hunting phenomenon. This is to prevent such things.

If the integrated value Σ is larger than ΣAPL, it is necessary to perform the exposure correction in the down direction because the exposure is excessive as described above. First, it is determined whether or not the direction of the previous exposure correction is 0 (see P2 in FIG. 19).
7) If it is down, the exposure correction in the same direction is performed again this time, and if it is not down, that is, if it is up, the direction of exposure correction is reversed. In the case of exposure correction in the same direction, the previous exposure correction value nc is doubled to add the correction. When the down value is 0, it means that the down processing has not been performed in the previous processing, so it is determined that the direction of the exposure correction is reversed, and the previous exposure correction value nc is multiplied by 1/2 to calculate the exposure correction value. (P29 of FIG. 19). Then, 0 is substituted for up, which is the direction of correction, and 1 is substituted for down (P30 in FIG. 19). Finally, the range of the exposure correction value nc is checked in the same manner as P9 in FIG. 17 (P31 in FIG. 19).
Exposure compensation is performed by subtracting nc from the address n (P31 in FIG. 19).

Next, at P27 of FIG. 19, down is 0.
If not, it is determined that the down process was performed in the previous process, and then it is determined whether or not the down process is 1 (P32 in FIG. 19). When down is 1, down
2 is substituted for (P33 in FIG. 19). And similarly in FIG.
The processing of P30 and P31 of 9 is performed. Also, after substituting 2 for up, if the integrated value Σ is larger than ΣAPL in the next shooting, that is, if the exposure is excessive, the exposure correction value nc is doubled (P34 in FIG. 19), and similarly, FIG. The processing of P30 and P31 is performed, and the doubled correction value is added this time. If the direction of exposure compensation is reversed as described above,
The reason why the correction value is not doubled but is corrected once with the same correction value and then the processing is performed is to prevent overcorrection at the time of image pickup and the occurrence of a hunting phenomenon, for the same reason as described above. .

Then, the image is picked up at the charge accumulation time and the gain corresponding to the address n of the LUT for which the exposure correction is performed in P26 or P31 of FIG. 19 (P2 of FIG. 17). The integrated value Σ obtained by imaging again is obtained (P in FIG. 17).
3) The process from the second exposure correction is similarly repeated.

When the direction of the exposure correction is reversed as shown in FIG. 14 by performing the above processing, the number of steps n of the exposure correction value nc is multiplied by 1/2 to obtain 1 /
The exposure correction is sequentially performed for 2 nc, 1/4 nc, and 1/8 nc, and the exposure correction is performed so that the determined APL value is obtained. In this way, by making the width of the control finer as it approaches the proper exposure, highly accurate control can be performed, and the time until the proper exposure value is obtained can be shortened. On the contrary, when the charge accumulation time corresponding to the target illuminance of the subject is greatly different or the illuminance of the subject is greatly changed, as shown in FIG. 15, for example, when the correction step number is 1/8 nc If the illuminance changes significantly, the number of steps is 1/8 nc, 1/4 nc, 1 /
By increasing the number of steps to 2 nc, it is possible to quickly follow changes in the illuminance of the subject.

Further, if the expression (3) is satisfied in P4 of FIG. 17 by the above-described repeated processing or in the initial shooting, it is determined that the shooting condition is close to the proper exposure condition, and the following processing is performed. First, the formula (3) will be described. Formula (3)
In order to determine whether the exposure value is close to the proper exposure value as described above, for example, it is determined whether the integrated value Σ is within 15% to 85% of the maximum integrated value Σmax. Here, the APL obtained at the proper exposure is 50% of the maximum value of the signal level, and the integrated value of the video signal at that time is ΣAPL. Therefore, the equation (3) can be expressed by the following equation (4). Σmax * 0.15 <Σ <Σmax * 0.80 (4)

When the equation (4) is satisfied, the exposure correction value nc is calculated by the following equation (5) (P36 in FIG. 18). nc = (Σ-ΣAPL) / 12 (5) As described above, the table values of the LUT 7 shown in FIG. 13 are provided with a difference of 4.6%. The maximum integrated value is 255, so 255 * 4.6% = 1
It becomes 2, and by dividing the value obtained by subtracting the integrated value ΣAPL obtained at the time of the proper exposure value from the obtained integrated value Σ by 12, it is possible to roughly estimate the difference in address value up to the proper exposure. Therefore, when an image is picked up under an image pickup condition close to the proper exposure value, the exposure correction value can be calculated at once by the equation (5).

When the integrated value obtained as described above satisfies the formula (4), that is, when the exposure value at the time of image pickup is close to the proper exposure, the proper exposure value is calculated by the formula (5) and the next image pickup is performed. The exposure value is determined, and when it is out of the condition of the formula (4), the exposure control described in the first and second embodiments is performed to realize high-speed and highly accurate automatic exposure control. it can.

In this flowchart, the LUT
In the case of the upper limit of the address value of, the maximum address value is used, and in the case of the lower limit, the minimum address value is used, the upper and lower limit processing is not particularly described, but it is necessary to add it to the processing in the flowchart if necessary. Needless to say.

[0081]

Since the present invention is constructed as described above, it has the following effects. In the image pickup apparatus according to the present invention, an exposure adjustment unit that adjusts an exposure amount of image pickup using the image pickup device, a calculation unit that performs calculation based on a signal obtained from the image pickup device, and a control that controls the exposure adjustment unit. The control means performs the second imaging by increasing or decreasing the exposure amount by the first correction amount from the exposure amount of the first imaging, and performs the second imaging based on the calculation result of the calculation means.
When it is determined that the second image pickup is underexposed when the second image pickup is the exposure amount increased by the first correction amount from the first image pickup, Controls the exposure adjustment means to increase the exposure amount by a second correction amount larger than the first correction amount to perform the third image pickup, and the second image pickup is performed by the first image pickup by the first image pickup by the first image pickup. When it is determined that the second imaging is overexposure when the exposure amount is increased by the amount, the exposure amount is decreased by the second correction amount smaller than the first correction amount and the third imaging is performed. The exposure adjustment means is controlled so that
If the exposure amount is reduced by the correction amount of
When it is determined that the image pickup of 1 is overexposure, the exposure adjustment unit is controlled to reduce the exposure amount by the second correction amount larger than the first correction amount and perform the third image pickup, and the second image pickup is performed. When the exposure amount is decreased from the first image pickup by the first correction amount and the second image pickup is determined to be underexposure, only the second correction amount smaller than the first correction amount is used. Since the exposure adjustment unit is controlled so as to increase the exposure amount and perform the third image pickup, it is possible to obtain an image pickup apparatus that realizes high-speed exposure control.

Further, in the image pickup apparatus according to the present invention, the exposure adjustment means for adjusting the charge accumulation time of the image pickup element, the calculation means for performing an operation based on the signal obtained from the image pickup element, and the charge accumulation time are set. It is provided with a table in which the addresses are set in order from the longest time to the shortest time, and the control means for controlling the exposure adjusting means. The control means is set to the nth address (n is an integer) of the table. performing a first imaging in the charge accumulation time, the first to determine the excess and deficiency of exposure during imaging based on the calculation result of the calculating means, the exposure at the time of the first imaging is excessive when,
A value m (m is an adjustment
Number) was added (n + m) sets the number locations charge accumulation time
In performing a second imaging, lack exposure during the first imaging
If m is, then m is subtracted from the address n in the table.
Second imaging with charge accumulation time set at address (nm)
It was carried out, based on the calculation result of the calculating means to determine the excess and deficiency of exposure during the second imaging during the second imaging
A exposure is excessive, and at the same time as the second deficiency judgment of exposure of the exposure <br/> the excess determination during the first imaging during imaging, the table (n + 2 × m) performs a third imaging at the set charge accumulation time at the address, the exposed during the second imaging an excessive, and of the second imaging
When the determination of overexposure or underexposure at the time of exposure differs from the determination of overexposure or underexposure at the time of the first imaging, (n + m /
2) The third image is taken at the charge accumulation time set at the address.
If the exposure was insufficient during the second imaging, and
The determination of excess or deficiency in the exposure at the time of the second image pickup is based on the above
When it is the same as the over / under deficiency of the exposure when shooting 1
Charge storage set at address (n-2 × m) in the table
The third imaging is performed during the product time, and the dew during the second imaging is performed.
The exposure is insufficient and the exposure during the second imaging
Excess or deficiency of the exposure is related to the exposure during the first imaging.
If it is different from the excess / deficiency judgment, (nm / m /
2) and controls the exposure adjustment means third imaging a row Migihitsuji at the set charge accumulation time at the address, it is possible to quickly follow to variations in object illuminance, reliable,
It is a Turkey to realize high-speed exposure control with a simple configuration.

Further, in the image pickup apparatus according to the present invention, the p address, the (p + 1) address and the (p + 2) address of the table are set.
Address (p is an integer and the lowest address in the table ≤ p ≤
The charge accumulation time set in the highest address of the table-2) was set to ((charge accumulation time set in p address / charge accumulation time set in (p + 1) address)) = ((p + 1) address Since there is a relation of charge accumulation time / charge accumulation time set at (p + 2) address, it is possible to quickly follow the fluctuation of the illuminance of the subject and to obtain an image pickup apparatus which is particularly reliable and realizes high-speed exposure control. be able to.

Further, in the image pickup apparatus according to the present invention, the exposure adjusting means is provided with a circuit for amplifying the signal output from the image pickup element, and the table shows the charge accumulation time and the amplification factor of the amplifying circuit when the image is exposed. Is set in the order of increasing or decreasing, it is possible to obtain an image pickup apparatus that can realize high-speed and highly reliable exposure control and can cope with a wide illuminance of an object.

Further, in the image pickup apparatus according to the present invention, the exposure adjustment means for adjusting the charge accumulation time of the image pickup element and one screen of the signal obtained from the image pickup element or a part thereof are integrated to obtain an integrated value Σ. Calculating means for calculating, and a table in which the charge storage time is set in order from the upper address of the address so that the length of the time increases or decreases at a constant rate,
And a control unit for controlling the exposure adjustment unit, the control unit performing the first imaging at the charge accumulation time set at the address n (n is an integer) of the table, and the integrated value Σ accumulated by the calculating unit is If it is within the predetermined range, the difference between the constant C and the integrated value Σ is divided by the ratio so that the address value indicating the table value corresponding to the proper exposure value and the table value used in the first imaging are obtained. The exposure adjustment means calculates a difference from the instructed address value, adds or subtracts the value obtained by the calculation as an exposure correction value so that the integrated value Σ approaches the constant C, and performs the next imaging. It is possible to obtain an image pickup apparatus capable of performing accurate exposure control particularly at high speed when the exposure amount of the image pickup is close to the proper exposure.

Furthermore, in the exposure control method of the image pickup apparatus according to the present invention, the first exposure amount at the time of the first image pickup
The calculation is performed based on the signal obtained by increasing or decreasing the exposure amount by the correction amount of 2 to perform the second imaging, and whether the exposure is excessive or insufficient for the second imaging is determined based on the calculation result. , When the second image pickup is the exposure amount increased by the first correction amount from the first image pickup, and it is determined that the second image pickup is underexposed, the second image pickup is larger than the first correction amount. The second imaging is performed when the third imaging is performed by increasing the exposure by the correction amount of 2 and the second imaging is the exposure that is increased by the first correction amount from the first imaging. When it is determined that the exposure is overexposed, the exposure amount is reduced by the second correction amount smaller than the first correction amount to perform the third image capturing, and the second image capturing is performed by the first image capturing amount than the first image capturing amount. If the second imaging is determined to be overexposure when the exposure amount is reduced by Decreases only exposure amount amount larger than the second correction amount performed third imaging of the second image capturing first
When it is determined that the second image pickup is underexposure when the exposure amount is reduced by the first correction amount from the image pickup of
Since the third exposure is performed by increasing the exposure amount by the second correction amount smaller than the first correction amount, it is possible to obtain the exposure control method of the imaging device that realizes the high-speed exposure control.

[Brief description of drawings]

FIG. 1 is a configuration diagram of an image pickup apparatus according to a first embodiment of the present invention.

FIG. 2 is a diagram illustrating a lookup table according to the first embodiment of the present invention.

FIG. 3 is a diagram illustrating a lookup table according to the first embodiment of the present invention.

FIG. 4 is a diagram illustrating exposure control according to the first embodiment of the present invention.

FIG. 5 is a diagram illustrating exposure control according to the first embodiment of the present invention.

FIG. 6 is a flowchart illustrating an operation of the image pickup apparatus according to the first embodiment of the present invention.

FIG. 7 is a flowchart illustrating an operation of the image pickup apparatus according to the first embodiment of the present invention.

FIG. 8 is a configuration diagram of an image pickup apparatus according to a second embodiment of the present invention.

FIG. 9 is a diagram illustrating a lookup table according to the second embodiment of the present invention.

FIG. 10 is a diagram illustrating a relationship among a charge storage time, an amplifier gain, and a subject illuminance in the lookup table according to the second embodiment of the present invention.

FIG. 11 is a flowchart illustrating an operation of the image pickup apparatus according to the second embodiment of the present invention.

FIG. 12 is a flowchart illustrating an operation of the image pickup apparatus according to the second embodiment of the present invention.

FIG. 13 is a diagram illustrating a lookup table according to the fourth embodiment of the present invention.

FIG. 14 is a diagram illustrating an exposure control according to a fourth embodiment of the present invention.

FIG. 15 is a diagram illustrating an exposure control according to a fourth embodiment of the present invention.

FIG. 16 is a flowchart illustrating an operation of the image pickup apparatus according to the fourth embodiment of the present invention.

FIG. 17 is a flowchart illustrating an operation of the image pickup apparatus according to the fourth embodiment of the present invention.

FIG. 18 is a flowchart illustrating an operation of the image pickup apparatus according to the fourth embodiment of the present invention.

FIG. 19 is a flowchart illustrating an operation of the image pickup apparatus according to the fourth embodiment of the present invention.

FIG. 20 is a diagram illustrating a relationship among charge accumulation time, amplifier gain, and object illuminance in the lookup table according to the fourth embodiment of the present invention. .

FIG. 21 is a configuration diagram of a conventional imaging device.

FIG. 22 is a diagram showing a photometric area for exposure control of a conventional image pickup apparatus.

FIG. 23 is a configuration diagram of a conventional imaging device.

[Explanation of symbols]

1 CCD, 2 amplifiers, 3 A / D converters,
4 timing generator, 5 computing means, 6
Control means, 7 LUT, 8 lens, 9 D / A
Converter, 20 lens, 21 diaphragm, 22 drive circuit, 23 imaging device, 24 preamplifier, 2
5 Variable gain amplifier, 26 A / D converter, 2
7 sync separation circuit, 28 switching circuit, 29 switching control circuit, 30 integrating circuit, 31 abnormality determination circuit, 32 average value calculation circuit, 33 comparison circuit, 3
4 target memory, 40 photometric sensor lens, 41 photometric sensor, 42 A / D converter, 43 lens,
44 diaphragm, 45 image sensor, 46 variable gain amplifier.

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04N 5/225-5/247

Claims (5)

(57) [Claims] 1. An exposure adjusting unit that adjusts an exposure amount of an image pickup using an image pickup device, a calculating unit that performs an operation based on a signal obtained from the image pickup device, and a control unit that controls the exposure adjusting unit. The control means performs the second imaging by increasing or decreasing the exposure amount by the first correction amount from the exposure amount of the first imaging, and the second imaging is performed based on the calculation result of the calculating means. If it is determined that the second imaging is underexposure when the second imaging is an increase of the exposure amount by the first correction amount compared to the first imaging, The exposure adjustment means is controlled to increase the exposure amount by the second correction amount larger than the first correction amount to perform the third imaging, and the second imaging is performed by the first correction amount more than the first imaging amount. The second image is judged to be overexposed when the exposure amount is increased. If it is detected, the exposure adjustment means is controlled so that the exposure amount is decreased by the second correction amount smaller than the first correction amount to perform the third image pickup, and the second image pickup is performed more than the first image pickup. When it is determined that the second image pickup is overexposure when the exposure amount is reduced by the first correction amount, the exposure amount is reduced by the second correction amount larger than the first correction amount. The second image pickup is underexposed when the exposure adjusting unit is controlled to perform the third image pickup and the second image pickup is the exposure amount reduced by the first correction amount from the first image pickup. If it is determined that the exposure adjustment means is controlled to increase the exposure amount by the second correction amount smaller than the first correction amount and perform the third image pickup. 2. An exposure adjusting means for adjusting a charge storage time of an image pickup device, a calculation means for performing an operation based on a signal obtained from the image pickup device, A table that is set in order from a higher address and a control unit that controls the exposure adjustment unit are provided, and the control unit performs the first imaging at the charge accumulation time set at the n-th address (n is an integer) of the table. It was carried out, first to determine the excess and deficiency of exposure during imaging based on the calculation result of the calculating means, when exposed during the first imaging is excessive is the address n of the table Add a value m (m is an integer) to correct the exposure
Performing a second imaging at e was (n + m) sets the number locations charge accumulation time, when exposed during the first imaging is insufficient, the Te
Set to the (n-m) address obtained by subtracting the above m from the n-address
It has been subjected to the second image pickup in the charge accumulation time when the second image pickup based on the calculation result of the calculating means
Determines excess or deficiency of exposure of the exposure time of the second imaging an excessive, and the second
When determining whether the exposure is excessive or insufficient during the second imaging ,
If it is the same as the overexposure / underexposure judgment of
+ 2 × m) , the third image capturing is performed for the charge accumulation time set to the address, and the exposure during the second image capturing is excessive, and
When determining whether the exposure is excessive or insufficient during the second imaging ,
If it is different from the judgment of whether the exposure is over or under,
3rd at the charge accumulation time set at (n + m / 2)
There rows imaging, a lack exposure during the second imaging, and the first
The above-mentioned first is the determination of excess or deficiency regarding the exposure at the time of image capturing.
If it is the same as the over / under judgment of exposure at the time of imaging,
At the time of charge accumulation set in the address (n-2 × m) of the table
The third imaging is performed between the two, and the exposure at the time of the second imaging is insufficient, and the third imaging is performed .
The above-mentioned first is the determination of excess or deficiency regarding the exposure at the time of image capturing.
If it is different from the over / under judgment about exposure at the time of imaging,
At the time of charge accumulation set in the address (nm-2) of the table
An image pickup apparatus, characterized in that the exposure adjustment means is controlled so as to perform a third image pickup between them. 3. The charge accumulation time set at addresses p, (p + 1) and (p + 2) of the table (where p is an integer and the lowest address of the table ≦ p ≦ the highest address of the table-2). Is (charge storage time set at address p / charge storage time set at address (p + 1)) = (charge storage time set at address (p + 1) / charge storage time set at address (p + 2)) 3. The image pickup apparatus according to claim 2, wherein the image pickup apparatus has the following relationship. 4. The exposure adjustment means includes a circuit for amplifying a signal output from an image pickup device, and the table has a charge accumulation time and an amplification factor of the amplification circuit in order of increasing or decreasing exposure amount during image pickup. The imaging device according to claim 2, wherein the imaging device is set. 5. A calculation is performed based on a signal obtained by increasing or decreasing the exposure amount by a first correction amount from the exposure amount at the time of the first image pickup, and performing a calculation based on a signal obtained by the second image pickup. The exposure of the second imaging is judged to be excessive or deficient based on the second imaging, and the second imaging is exposed when the second imaging is the exposure increased by the first correction amount from the first imaging. If it is determined to be insufficient, the exposure amount is increased by the second correction amount larger than the first correction amount to perform the third image pickup, and the second image pickup is performed by the first correction amount more than the first image pickup. When it is determined that the second imaging is overexposure when the exposure amount is increased, the exposure amount is decreased by the second correction amount smaller than the first correction amount and the third imaging is performed. , When the second image pickup is the exposure amount reduced by the first correction amount from the first image pickup, When it is determined that the image pickup is overexposure, the exposure amount is reduced by the second correction amount larger than the first correction amount, and the third image pickup is performed. When it is determined that the second image pickup is underexposure when the exposure amount is reduced by the correction amount, the exposure amount is increased by the second correction amount smaller than the first correction amount and the third exposure amount is increased. An exposure control method for an image pickup apparatus, which is characterized by performing image pickup.