JP3505323B2 - Automatic exposure adjustment device - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic exposure control device used in an electronic still camera for obtaining a still image.

[0002]

2. Description of the Related Art In an image pickup device such as an electronic still camera, an automatic exposure control device has been favored which realizes an optimum exposure state by adjusting a charge accumulation period of a CCD imager using an electronic shutter. Generally, this charge storage period is expressed as a shutter speed, and for example, if the shutter speed is 1/60, it means that the charge storage period is 1/60 seconds. Therefore, in the following description, the charge storage period will be described as a shutter speed.

The exposure control method described above is based on the premise that the CCD imager output changes substantially linearly with respect to the change in the amount of light incident on the CCD imager, as shown in FIG. When shooting is performed at the speed S0 and the luminance level of the entire screen of Ya is obtained, the shutter speed S0 is set to the ratio of the luminance level Ya and the target luminance level Yt expected to realize the optimum exposure state. By multiplying, the optimum next shutter speed SP can be determined by the equation (1). The target brightness level Yt is set in advance by an actual measurement value.

[0004]

[Formula 1] SP = S0 × Yt / Ya More specifically, it is actually difficult to determine the exposure and the shutter speed in one operation, and the same operation is repeated about three times to finally perform the main exposure. Determines the shutter speed of. That is, first, when the photographer operates the release button, the image pickup signal output from the CCD imager obtained by executing the first exposure after setting the shutter speed to the initial value St in the period a of FIG. The luminance level Yr is detected, and Sp1 = St × Yt / in the period b.
From the Yr calculation formula, the shutter speed S at the next exposure
Calculate p1. Next, exposure is performed at the newly set shutter speed Sp1 in the period c, and in the period d, the shutter speed Sp1 is multiplied by the ratio of the screen brightness level obtained by the exposure in the period c and the target brightness level, and the next time. The shutter speed Sp2 of is determined.

Further, in the period e, a new shutter speed S
The third exposure is performed at p2, and the shutter speed Sp3 is determined by multiplying the shutter speed Sp2 by the ratio of the screen brightness level obtained by the third exposure during the period f and the target brightness level. Then, the main exposure is performed at the shutter speed Sp3 finally determined in the period g,
The obtained image pickup signal is subjected to signal processing and a still image is recorded on the recording medium.

As the initial value St, it is preferable to set the speed as low as possible in order to reduce the influence of flicker, and conversely, as fast as possible in outdoor shooting. Considering the overall balance, it is about 1/250 seconds. Just set it.

[0007]

The equation (1), which is the arithmetic expression in the above-mentioned exposure control method, is based on the change of the light quantity to the CCD.
It is premised that the imager output changes linearly, and there is no problem in the linear area where the light intensity rises to the right in Fig. 2, but there is a very bright subject in the screen, and the light intensity increases, causing If the CCD major output is saturated, disadvantageously occurs. For example, as shown in FIG.
When the average brightness level of the screen is equal to or less than the target value corresponding to the target brightness level when converted to the average value, and the high brightness part reaches the saturation level, the shutter speed of the next exposure is calculated by the above formula. When calculation is performed and exposure is performed, in order to increase the average brightness level to the target value, it is necessary to slow down the shutter speed and set a longer charge storage period in order to obtain a larger amount of incident light. In the region, the brightness level does not change even if the amount of incident light increases, and it becomes difficult to raise the average brightness level to the target value at the shutter speed set by calculation.

Similarly, when the average luminance level exceeds the target value and there is a high luminance portion exceeding the saturation level as shown in FIG. 5, the shutter speed is lowered to lower the average luminance level to the target value. It functions to reduce the amount of incident light by increasing the speed to shorten the charge accumulation period, but in this case, even if the amount of incident light decreases, the saturation level remains fixed at the saturation level. It is difficult to reduce the average brightness level to the target value with the set shutter speed.

As described above, when there is a high-luminance portion that greatly exceeds the saturation level in the screen, the amount of incident light is not reflected in the luminance level in the saturation area. Therefore, this luminance level is evaluated. Even if the amount of light is adjusted, the calculation result and the actual control result will deviate from each other, making it difficult to optimally adjust the exposure.

In order to eliminate such an inconvenience, if the number of times of setting work of the shutter speed by the screen brightness evaluation performed before the main exposure is increased, the shutter speed can be gradually converged to the target value. Such a countermeasure is not allowed in an electronic still camera which requires a very short time from button operation to main exposure, that is, quick response.

[0011]

According to the present invention, an image pickup screen of a CCD imager is divided into a plurality of areas, and an area-brightness detecting means for detecting the brightness level of each area as an area-brightness level, and an area-brightness detecting means. Counting means for counting the number of areas whose levels exceed a predetermined level, second brightness detecting means for detecting the brightness level of the entire screen as the screen brightness level, and the ratio of the screen brightness level and the target brightness level to the current shutter speed. Shutter speed determining means for multiplying and determining the next shutter speed,
When the screen brightness level is lower than the target brightness level,
The ratio is corrected from the count value of the counting means and the saturation level of the CCD imager, and when the screen brightness level is higher than the target brightness level, a correction amount proportional to the number of areas which is the saturation level is added to the screen brightness level. And level correction is performed.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram of an electronic still camera which is a device of the present embodiment, and FIG. 6 is a flow chart for explaining the operation in the block diagram.

In FIG. 1, reference numeral 1 denotes a CCD imager which photoelectrically converts light incident through an optical system and outputs it as an image pickup signal. The CCD imager 1 has a front surface of a light receiving portion R as shown in FIG. , G and B primary color filters 3
0s are arranged in a mosaic pattern, and one of R, G, and B is arranged in a one-to-one correspondence with each of the light-receiving units forming each pixel of the CCD imager 1.

The light that has passed through the lens is supplied to the light receiving portion of the CCD imager 1 through this color filter and photoelectrically converted, and the obtained charge is an exposure period set corresponding to the shutter speed, that is, charge accumulation. It is accumulated during the period and output to the outside.

More specifically, the CCD as shown in FIG.
The imager 1 includes a light receiving portion 82 corresponding to each pixel, a vertical transfer register 83 for vertically transferring the accumulated charges of photoelectric conversion outputs at these light receiving portions, and a vertical transfer register arranged at the end of these vertical transfer registers. And a horizontal transfer register 84 for horizontally transferring the charges transferred from the register, and is driven and controlled by a timing signal output from the timing generator (TG) 10.

Here, the light receiving portion 8 is used as the timing signal.
2 to read out the accumulated charge from the vertical transfer register 83 to the vertical transfer register 83, the vertical transfer pulse to transfer the charge in the vertical transfer register 83 line by line in the vertical direction, and the charge in the horizontal transfer register 84 in the pixel direction in the horizontal direction. There are a horizontal transfer pulse to be transferred and a sweep pulse for sweeping the photoelectric conversion output of the light receiving portion to an overflow drain (not shown) to invalidate it during a non-exposure period, that is, a non-charge accumulation period.

The timing generator 10 receives a shutter speed instruction signal, which will be described later, and controls the charge accumulation period by controlling the output period of the sweep-out pulse in order to realize the instructed shutter speed. Incidentally, the control of the shutter speed by the output control of the sweep-out pulse in this way is a known technique as an electronic shutter function.

In this way, the charge accumulated in each pixel of the CCD imager 1 is sequentially output as an image pickup signal. here,
Since the color filter array is set as shown in Fig. 8,
After the charge is accumulated in the CCD imager 1, the G signal that has passed through the green color filter at the lower left end is first output, and then the B signal that has passed through the blue color filter at the right end is sequentially output, and when the output at the lower end is completed, Next, the color signals in the second column from the bottom are sequentially output in the same manner.

Reference numeral 2 denotes an A / D converter for sequentially digitizing an image pickup signal output from the CCD imager 1, that is, a color signal corresponding to each color filter. The A / D conversion output is sequentially output to the RAM 7 in the subsequent stage as image data. Written.

Writing to the RAM 7 is controlled by a writing control signal from the writing / reading control circuit 8, an address is given to the RAM 7 in advance for each pixel of the CCD imager 1, and the timing generator 10 outputs the address. Based on the timing signal, the writing of data is controlled so that the image pickup signal of each pixel is stored in the storage position of the corresponding address. In order to determine which pixel in the CCD imager the input data is, the vertical pulse reset by the read pulse and counting the vertical transfer pulse, and the horizontal counter reset by the vertical transfer pulse. It becomes possible by providing a horizontal counter for counting the pulses and determining the vertical and horizontal positions by the count value of each counter.

In this way, when the process of taking out the accumulated charges of all the pixels by one exposure of the CCD imager 1 is completed,
Image data of any one of R, G, and B color signals is stored in the RAM 7 for each pixel.

When the writing of the data of all the pixels to the RAM 7 is completed, the L-shaped three pixels each formed of one R, G and B in the color filter of FIG. A plurality of blocks B11, B12, ... Are formed as one block, and by the read control signal from the write / read control circuit 8,
The R, G, and B image data is read for each of these blocks. In FIG. 9, the filter of the pixels included in the block is underlined, one block is surrounded by a solid line, and the boundaries of the R, G, and B filters in this block are indicated by chain lines. There is.

Reference numeral 9 denotes R in the same block read out,
An arithmetic unit that substitutes G and B color signal data into a predetermined arithmetic expression to generate luminance data Dy indicating the luminance signal level and color difference data Dr and Db indicating the R-Y and BY color difference signal levels. If the color signal data of R, G, and B in a certain block is r, g, and b, the arithmetic expression is Dy = 3r + 6g
+ B, Dr = r-g, and Db = b-g are set.

The brightness data Dy calculated in this manner is sequentially input to the digital integration circuit 20 in the subsequent stage for each block, and is set in advance in the image pickup screen: vertical direction × horizontal direction = 16 ×
It is digitally integrated for each of the 256 areas of 16 and is supplied to the microcomputer 16 in the subsequent stage as a brightness level for each area. More specifically, the integrating circuit 20 includes the adder 2
1 and a memory 22, a storage area is set in the memory 20 for each area including each of the blocks set as shown in FIG. 9, and the brightness data of a block is input from the computing unit 9. And the accumulated data in the storage area of the area including this block is read from the memory 20 to the adder 21, and the added data and the arithmetic unit 9 are read in the adder 21.
The brightness data from is added and written as new integrated data in the storage area of the corresponding area in the memory 22, and the integrated data is updated. Here, since each block is always located in any one area, the integrated data of any area is updated every time the brightness data is input, and all blocks of one screen are updated. When the brightness data is input to the integrating circuit 20, the sum of the brightness data of the blocks in each area is finally stored in the memory 22, and the sum of each area is the brightness level Y (i) of each area.
(I: integer from 1 to 256). Each area has the same size, and the number of blocks included in each area is set to be the same.

In the microcomputer 16, 25 for each obtained area
The exposure adjustment operation is executed based on the six brightness levels, and the result of this exposure adjustment is supplied to the timing generator 10 in the subsequent stage as a shutter speed instruction signal for instructing the shutter speed.

Reference numeral 6 receives the image data stored in the RAM 7 by the exposure adjustment for the three screens after the shooting command input by the release button 14 is input, and the image data stored in the RAM 7 is received, and the color separation, the gamma correction and the signal compression are performed. It is a signal processing circuit that performs well-known signal processing such as, and outputs as regular still image information, and executes the signal processing only when there is an operation instruction from the microcomputer 16. Reference numeral 15 is a flash memory that stores still image information output from the signal processing circuit 6.

Next, prior to a concrete exposure control operation in the microcomputer 16, an outline of a method for removing the influence of the saturation of the CCD imager 1 from the exposure control will be described.

When the brightness level during exposure adjustment, ie, dimming, is smaller than the target brightness level and the high brightness area has reached the saturation level of the CCD imager 1, the charge storage period is lengthened in order to increase the brightness level. However, the brightness level in the high brightness area does not exceed the saturation level. Therefore, it is necessary to remove the influence of the brightness level in the high brightness area.

Therefore, the next shutter speed is SP,
If the current shutter speed is S0, the brightness level of the entire screen obtained at this current shutter speed S0 is Ya, the target brightness level is Yt, the saturation level is YL, and the number of saturation areas is N, the effect of saturation from Equation 1 is obtained. Is satisfied and Expression 2 is satisfied, the shutter speed for the next time after the influence of the saturated area is removed is set.

[0030]

## EQU00002 ## SP = S0.times. (Yt-YL.times.N) / (Ya-YL.times.N) However, actually, the ratio between the current shutter speed and the next shutter speed is large, that is, the shutter speed is significantly increased. In the situation where it is necessary to make the charge accumulation period longer by slowing down, when the shutter speed is S0, even if the brightness level is below the saturation level, if the brightness level is high to some extent, the next shutter speed is used. There is a problem of saturation.

Therefore, it is necessary to take measures for an area having a high brightness level to some extent, because there is a possibility that the area will reach the saturation level by setting a new shutter speed.

Specifically, for example, the shutter speed S0
It is assumed that the area (the number of areas: E1) of which the brightness level becomes SUT by the shooting in (2) will reach the saturation level YL by the next shooting at the shutter speed SP.

In such a situation, the increase P in the calculated brightness level that cannot actually occur due to saturation is expressed by
When expressed as Yt / Ya = G, the following expression 3 is given.

[0034]

## EQU00003 ## P = SUT.times.E1.times.G-YL.times.E1 In this equation, the result obtained by multiplying the previous term, that is, the brightness level SUT by G times and multiplying by the number of areas is Become. In addition, the latter term, that is, the result of multiplying the saturation level YL by the number of areas, becomes a shaded area b, and the difference between the two becomes an increase P represented by a shaded area c.

Further, in order to simplify the equation (3), it is assumed that the increase amount of P has occurred in the area which has already reached the saturation level due to the current photographing, and the area which has already reached the saturation level. It is assumed that the number is N (N: number of saturation level conversion areas). That is, the brightness level of areas 1 to 11 becomes as shown in FIG. 11A by shooting at the current shutter speed S0, and the shutter speed SP is determined so that each brightness level is doubled with G = 2. , As shown in FIG. 11B, areas 2, 3, 6, 7,
The calculated brightness level exceeds the saturation level in the five areas 10 and the sum of the brightness levels (shaded lines) exceeding the saturation level in these five areas has already reached the saturation level shown in (c). Assuming that the saturation area is equivalent to N when converted into the amount W that exceeds the saturation level when the saturation area is doubled, the following equation 4 is established.

[0036]

[Equation 4] P = N × YL × G−N × YL = N × YL × (G-1) From the expressions 4 and 3, the following expression 5 is established.

[0037]

## EQU00005 ## N = E1.times. (SUT.times.G-YL) /YL.times. (G-1) Therefore, in order to ensure the accuracy of exposure control and simplify the calculation, the brightness level is divided into three ranges. Then, the average level of each range is approximated to the SUT of each range to calculate the saturation level conversion area number N. Specifically, the brightness level of the entire screen obtained at the current shutter speed S0 is set to the saturation level YL, the saturation level YL to a range 1/3 of the saturation level YL, and the saturation level YL from 2/3 to the saturation level YL. 1 /
It is subdivided into a range 2 of 3 areas and a range 3 which is 1/3 or less of the saturation level YL, and the number of areas whose brightness level is the saturation level YL is N1, the number of areas in the range 1 is N2, and the number of areas in the range 2 Is N3, the number of areas in range 3 is N4, the average brightness level of the area in range 1 is YL × 5/6, and the average brightness level of the area in range 2 is YL × 1/2, range 3
Approximate the average brightness level of the area at YL x 1/6,
Summarizing the number of saturation level conversion areas for each range is
Therefore, the following Expression 6 is established.

[0038]

[Equation 6] N = N1 + N2 × (YL × 5/6 × G-YL)
/ YL x (G-1) + N3 x (YL x 1/2 x G-Y
L) / YL × (G-1) + N4 × (YL × 1/6 × G−
YL) / YL × (G-1) Since the number N of saturation level conversion areas of this equation 6 is a value converted into the number of saturation areas of equation 1, N of equation 6 is substituted into N of equation 1, The next shutter speed is determined by excluding the saturation level or the brightness level of the number of areas converted to the number of saturated areas from the calculation of the shutter speed.

The countermeasure for the saturated area executed during the above exposure control will be described in detail with reference to the flowchart of FIG. First, when the photographer turns on the release button 14 to perform photographing at a shutter speed in a predetermined initial state and the detection result of the brightness levels of all areas for one screen is stored in the memory 22, At 51, each variable i, Ya, U1, U2, U3,
Clear U4. Here, Ya indicates the brightness level of the entire screen, U1 indicates the count value of the counter that counts the number of areas although the brightness level for each area is equal to the saturation level YL, and U2 indicates the saturation level for each area. U3 indicates the count value of the counter that counts the number of areas that are less than the level YL and are in the range of ⅔ × YL or more. The count value of the counter which counts the number of areas of U.sub.1 is shown, and U4 shows the count value of the counter which counts the number of areas of the one whose luminance level for each area is less than 1 / 3.times.YL.

Next, in step 52, the brightness level of each area is sequentially read as Y (i) from the memory 22, and in step 53 it is judged whether or not the brightness level Y (i) is the saturation level YL. In this case, the count value U1 is incremented in step 54, and if they are not equal, the brightness level Y (i) and 2/3 × Y are calculated in step 55.
It is determined whether or not it is L or more, and if it is 2/3 YL or more, the count value U2 is incremented in step 56 and 2
If it is less than / 3YL, 1 / 3YL in step 57.
It is determined whether or not it is the above, and if it is 1/3 YL or more, the count value U3 is incremented in step 58 and 1
If it is less than / 3YL, the count value U4 is incremented in step 80.

Thus, the count values U1, U2, U3, U
When the increment of 4 is completed, the brightness level Y (i) is added to the brightness level Ya of the entire screen in step 59, the variable i is incremented in step 60, and the variable i is changed to 256 in step 61. It is determined whether or not it has been reached, and if it has not reached 256, it is determined that a series of determination operations have not been completed for all areas of one screen, and the process returns to step 52 and the same processing is repeated.

When it reaches 256, it is determined that the determination in all areas is completed, and the process proceeds to step 62 in the subsequent stage. Therefore, when the determination work in all areas is completed, the number of areas where the brightness level Y (i) = saturation level YL becomes the count value U1, and 2/3 × YL ≦ Y (i) <
The number of areas, which is YL, becomes the count value U2, and is ⅓ ×
The number of areas where YL ≦ Y (i) <2/3 × YL is the count value U3, and the number of areas where Y (i) <1/3 × YL is the count value U4. In addition, the sum of the luminance levels of all areas is calculated for Ya.

Thus, the determination of the brightness level of each area is 1
When completed for the screen portion, the target brightness level Yt / the brightness level Ya of the entire screen is calculated as a ratio G in step 62, and the brightness level Ya and the target brightness level Yt are compared in size in step 63, and at the same time, the first time. Dimming, that is, it is determined whether or not the luminance level is obtained by the evaluation of the first imaging screen, and the first dimming and luminance level Y
If it is determined that a exceeds the target brightness level Yt, the process proceeds to step 64, and if not, the process proceeds to step 65.

In step 64, when the brightness level of the entire screen during dimming is higher than the target brightness level and the high brightness area reaches the saturation level, how much the exposure time is shortened becomes smaller than the saturation level. Considering that it is impossible to know that, a correction operation is performed in which a value obtained by multiplying the number of areas U1 reaching the saturation level by a coefficient g is added as a correction value to the brightness level. That is, the brightness level Ya is corrected by the formula shown in Expression 7. The coefficient g is a value determined in advance by experiments.

[0045]

[Equation 7] Ya ← Ya + Ya × g × U1 / 256 In this way, the luminance level of the entire screen is increased in proportion to the number of saturated areas from the actually measured value, and then in step 66, Yt
Since the ratio of / Ya is multiplied by the current shutter speed S0 to determine the next shutter speed SP, the charge accumulation period becomes shorter in the next shooting result as compared with the case where no correction is made in step 64. The brightness level of the entire screen will be suppressed, and it will be returned to the area of the straight line rising to the right in FIG. 2, and the brightness level of the entire screen will be below the target brightness level due to the second and subsequent light adjustments. Then, a series of processes after step 67 described later is controlled so as to approach the target brightness level. It should be noted that when the high brightness level is almost the same as the saturation level, it will be overcorrected, but the output of the CCD imager 1 will change substantially linearly below the saturation level. There is no particular problem because the light is dimmed at high speed in the area and fine adjustment is made by dimming in the linear area during the second and subsequent light adjustments.

Next, in step 65, the brightness level Ya and the target brightness level Yt are compared. If the brightness level Ya is equal to or higher than the target brightness level, it is not necessary to raise the brightness level by dimming, and 1 Since the correction has been completed in step 64 during the second light control, SP = SP in step 66 without correcting the brightness level of the entire screen.
Next shutter speed S by S0 × (Yt / Ya)
P will be determined.

On the other hand, if it is determined in step 65 that the brightness level of the entire screen is lower than the target brightness level, the charge accumulation period is lengthened so as to raise the brightness level by the processing of step 67 and subsequent steps. However, here, the above-mentioned measures are taken for an area that is already at the saturation level or an area that may reach the saturation level due to a slower shutter speed.

That is, at step 67, the saturation level conversion area number N is calculated by the equation (6). Here, the ratio G is the value calculated in step 62, and the number of areas N1, N
2, N3 and N4 are count values U1, U2 and U, respectively.
Equivalent to 3, U4.

Next, in step 68, the next shutter speed SP is calculated from Equation 1, and in step 69 it is determined whether the correction operation in step 67 is the first correction. If it is the first correction, The ratio G used for the correction is the value set in step 62, and in consideration of the fact that the influence of the luminance level of the area that may reach the saturation level in the next shooting is not excluded, the step 70 is performed. Then, the influence of the saturation level conversion area is eliminated from the target brightness level and the brightness level of the entire screen, and the ratio G is updated as shown in Expression 8.

[0050]

(8) G = SP / S = (Yt−YL × N) / (Ya−
YL × N) Then, returning to step 67, a series of correction operations is repeated.

If it is determined in step 68 that the correction is not the first correction, that is, the correction is the second correction, it is determined that the optimum correction has been made and all the processes are completed.
Needless to say, if the correction in step 67 by updating the ratio G is performed many times, the accuracy will be improved, but due to time constraints, the correction is limited to twice.

In this way, when the next shutter speed is determined in step 66 or 68, the microcomputer 16
Ends the exposure adjustment routine, the shutter speed determined here is supplied to the timing generator as a shutter speed instruction signal, and the charge accumulation period corresponding to this is set, and then the CCD imager 1 displays the next two screens. When driving is performed so as to photograph the eyes and the brightness level of each area is detected, a series of processes from step 51 is performed again, and thereafter, exposure and shutter speed determination are similarly repeated for three screens. The fourth screen is exposed at the shutter speed determined by the screen evaluation, and the obtained still image is supplied from the RAM 7 to the signal processing circuit 6 to perform well-known processing such as color separation processing and signal compression. After that, the still image is stored in the flash memory 15, and the shooting of one still image is completed.

In the above embodiment, when calculating the saturation level conversion area N in step 67, the brightness range is divided into three equal parts and calculated for each range. Needless to say. Further, although the average brightness level in each range is approximated to the intermediate level of each range, it may be approximated to the lower limit value of each range in order to prevent overcorrection.

The minimum value of (Ya-YL × N) in the equation 1 used in step 68 is set to 1.

Further, in the block for calculating the luminance data in the arithmetic unit 9, 3 pixels of R, G and B out of 4 pixels of 2 × 2 are used, and the color signals of these 3 pixels are Dy = 3r + 6.
It is calculated by substituting the arithmetic expression of g + b, but it is also possible to use 1 block as 2 × 2 4 pixels and multiply the sum of the G signals of 2 pixels among these by 3 times and use it instead of 6 g. Is.

[0056]

As described above, according to the invention of claim 1,
When the brightness level of the screen is lower than the target brightness level, the brightness level of the area expected to reach the saturation level can be excluded from the determinants of the next shutter speed by raising the brightness level. Highly responsive exposure control is possible.

According to the second aspect of the invention, when the screen brightness level is higher than the target brightness level, it is expected that there is an area that has already reached the saturation level, and the area that has reached the saturation level is predicted. It is possible to intentionally raise the apparent screen brightness level according to the number above the actual measurement value, reduce the area to maintain the saturation level at the next exposure adjustment, and then perform the exposure adjustment again. High-precision exposure adjustment is possible.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention.

FIG. 2 is a diagram showing a relationship between an incident light amount of a CCD imager and an imaging output.

FIG. 3 is a diagram illustrating exposure adjustment timing according to an embodiment of the present invention.

FIG. 4 is a diagram showing a relationship between a brightness level and a saturation level during normal exposure adjustment.

FIG. 5 is a diagram showing a relationship between a brightness level and a saturation level during normal exposure adjustment.

FIG. 6 is a flowchart of an embodiment of the present invention.

FIG. 7 is a diagram illustrating a CCD imager according to an embodiment of the present invention.

FIG. 8 is a diagram illustrating a color filter mounted on a CCD imager according to an embodiment of the present invention.

FIG. 9 is a diagram illustrating blocks on the CCD imager according to the embodiment of the present invention.

FIG. 10 is a diagram illustrating a correction operation according to the embodiment of the present invention.

FIG. 11 is a diagram illustrating a calculated amount in which a luminance level exceeds a saturation level due to a slow shutter speed according to an embodiment of the present invention.

[Explanation of symbols]

1 CCD imager 20 Digital integration circuit 16 microcomputer 10 Timing generator

Claims (2)

(57) [Claims] 1. An area-by-area luminance detecting means for dividing an image pickup screen of a CCD imager into a plurality of areas and detecting a luminance level of each area as an area-by-area luminance level, and an area in which the area-by-area luminance level exceeds a predetermined level. Counting means for counting the number, second brightness detecting means for detecting the brightness level of the entire screen as a screen brightness level, and multiplying the ratio of target brightness level / screen brightness level by the current charge accumulation period of the CCD imager. A charge storage period determining means for determining a next charge storage period, and when the screen brightness level is lower than the target brightness level, the count value of the counting means and the CCD
An automatic exposure adjusting device, wherein the ratio is corrected according to a saturation level of an imager. 2. An area-by-area brightness detecting means for dividing an image pickup screen of the CCD imager into a plurality of areas and detecting the brightness level of each area as an area-by-area brightness level, and the area-by-area brightness level being saturated by the CCD imager. Counting means for counting the number of areas having reached the level, second brightness detecting means for detecting the brightness level of the entire screen as the screen brightness level, and a ratio of target brightness level / screen brightness level to the current charge of the CCD imager. A charge accumulation period determining unit that determines the next charge accumulation period by multiplying the accumulation period, and a correction amount that increases as the count value of the counting unit increases when the screen brightness level is higher than the target brightness level. An automatic exposure adjustment device comprising level correction means for adding to the screen brightness level.