JPH09261531A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide the image pickup device by which suitable exposure is obtained for various object scenes including back light scene with a simple configuration. SOLUTION: An image pickup pattern is divided into sub photometry areas, and a sub object value setting means 91 sets a sub photometry object value to each sub photometry area, to which each sub photometry area value is to be reached, and an arithmetic means 92 calculates a total sum of deviations between each sub photometry object value set by the sub object value setting means 91 and each sub photometry value to obtain an exposure control variable with respect to an object to be picked up, and an exposure control means 93 controls the exposure with respect to the image pickup based on the exposure control variable obtained by the arithmetic means 92.

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 a built-in exposure control section.

[0002]

2. Description of the Related Art As an exposure control device applied to an image pickup device, various types have been proposed. As a general image pickup device, there are a silver salt camera to which a normal silver salt film is applied, a video camera for electronically picking up an image, and the like.
In recent years, still video cameras that electronically capture still images have become widespread. Various types of exposure control devices are applied to these imaging devices. For example, since a silver salt camera records an image using a film, it is equipped with a photometric sensor for measuring the amount of light for photographing. At the beginning of the emergence of this type of camera, it was equipped with a single photometric sensor, but in recent years it has come to be equipped with multiple photometric sensors, and furthermore, it has expanded its area. It has been developed into a form in which an area sensor is provided for performing photometry for each of the held photometric target regions and performing exposure control based on the photometric value.

On the other hand, in a video camera, the image pickup device itself for converting an image of a subject into an electric signal can also function as a photometric sensor. Therefore, a system in which the image pickup device is also used as an area sensor for photometry has already been realized. There is. In both the photometric system for the silver halide camera and the photometric system for the video camera described above, the average value (average photometric value) of the luminance is calculated over the entire screen area or almost the entire screen area related to the shooting, and the average photometric value is determined. In general, the exposure control is performed so as to reach the single control target value of. It should be noted that there has been already proposed a system in which various modifications are made instead of performing control by setting a single control target value for the average photometric value.

For example, this is a method of measuring the brightness of only a part of the screen to be photographed, which is called partial metering or spot metering. There is also a method (weighted average photometry) of obtaining photometric values of various portions on the screen, multiplying each portion by a weighting coefficient, and then obtaining an average value. Further, there is a so-called peak metering method in which the photometric values of the brightest part and the darkest part in the screen are obtained and the values are controlled so as to be predetermined values.

In each of the above methods, a single control target value is set in correspondence with the photometric value, and control is performed so that the photometric value matches this target value. Incidentally, a method of variably setting the single control target value has also been proposed in the past. However, variably setting the target value is merely selective setting in accordance with the situation, and there is no change in taking a single value at a certain point in time. Therefore, the technology is essentially the same as the conventional control method using a single control target value.

The method of changing the level of the control target value is applied, for example, when performing control corresponding to backlight. When a person standing by the window is the subject, a means to specially identify that the background is extremely bright and the target subject is relatively dark is provided, and the target is set when the subject is backlit. The level is variably set, or the screen is divided into multiple areas and weighted for each area to average the brightness on the screen. Some are configured to change. As a method of changing the weighting, there is a method of setting the weighting for a specific area to zero, that is, excluding some information depending on the case. Further, it is proposed that fuzzy reasoning is applied as an arithmetic algorithm in various judgment operations. All of the above are in the category of the method of variably setting a single target value.

[0007]

However, in any of the conventional methods described above, a single target value is set at a temporary point and the photometric value at that time is made to match this target value. The control is performed as follows. Therefore, it is essentially difficult to determine the optimum exposure value in which the different brightness of each part in the screen to be photographed is separately considered.

It is well known that, in the conventional method such as average photometry, when a person or the like near a window is used as a subject, so-called black crushing, that is, a phenomenon in which the subject appears in total darkness occurs. This phenomenon occurs because the person who is the main subject is relatively darkly crushed because the very bright part of the background is strongly influenced because the entire screen is viewed on average. In order to avoid this, it is possible to perform spot metering only on the central part of the screen where such a main subject exists, but if the position of the main subject deviates from the central part of the screen, it will not work and will be ignored. There is a risk of malfunction when shooting a general scene. In order to deal with such a problem, a method of tracking the photometric area with respect to the movement of the subject has been proposed, but the system itself for tracking the subject is very complicated and large-scale. In addition, it is still difficult to obtain sufficient tracking accuracy.

Further, in the above-mentioned weighted average photometry, when the photometric value is calculated, each corresponding photometric value is weighted. Although the weighting coefficient may be variably set, the weighting coefficient is assigned to each photometric value. Since the calculation is performed by obtaining the sum of these values after multiplying by, the effect of the subject with high brightness has a large effect on the overall photometric value, and it is relatively There was a problem that the information in the dark part could not be sufficiently reflected in the total photometric value. Due to such a situation, when shooting a backlit scene or the like, a so-called main subject is often crushed.

In view of the above points, the present invention does not include a complicated and costly component such as an automatic tracking device and a fuzzy inference circuit, has a simple configuration, and is suitable for various object scenes including a backlight scene. It is an object of the present invention to provide an imaging device capable of obtaining a suitable exposure.

[0011]

In order to solve the above-mentioned problems, an image pickup apparatus of the present invention is: a whole or a part of a photographing screen is divided into a plurality of areas, each area being a sub-photometering area, Sub-photometric means for obtaining the sub-photometric value corresponding to the brightness of the subject to be photographed for each photometric area, and the sub-photometric target to be separately reached for each sub-photometric value output from the sub-photometric means A sub-target value setting means for setting a value, and a total sum of deviations between the sub-target values set by the sub-target value setting means and the corresponding sub-photometric values It is characterized by further comprising: a calculation unit for obtaining the exposure control amount; and an exposure control unit for controlling the exposure related to the photographing based on the exposure control amount obtained by the calculation unit.
……… (1)

[0012]

The sub target value set by the sub target value setting means and the sub target value set by the sub target value setting means for each sub photometric area, which is an area formed by dividing the whole or a part of the photographing screen by the calculating means. In order to obtain the exposure control amount for the subject to be photographed by calculating the sum of the deviations from the respective sub-photometric values corresponding to, the image within the luminance range (luminance reproduction range) was adjusted according to the situation of the scene. It is possible to take a picture.

The features found in various limited aspects of the present invention will be listed below. The calculation means includes level normalization means for normalizing the levels of the respective deviations between the respective sub-photometric values and the corresponding sub-target values. The imaging device according to (1) above
(2) The calculating means includes level normalizing means for normalizing the levels of the respective deviations between the photometric values and the corresponding sub-target values, and the levels. The image pickup apparatus according to (1) above, further comprising: a weighting unit that weights each value standardized by the normalizing unit. The control means performs feedback control by changing a parameter relating to exposure so that the photometric value converges to a predetermined value, and the feedback control is performed.
The imaging device according to (2) or (3)
(4) The sub-target value setting means forms an order of magnitude of each sub-photometric value and sets each sub-target value so as to correspond to the order. The image pickup device according to (1), (2), (3) or (4) above, characterized by: (5) The sub target value setting means corresponds to each of the sub photometric values. Setting a plurality of sub target values based on different setting grounds as each of the sub target values to be set, the calculation means performs a different calculation for each of the plurality of sub target values with respect to each of the sub photometric values. The imaging device according to (1), (2), (3) or (4) above, characterized in that it includes means for obtaining the photometric value from the result of each of the respective calculations. -The sub target value setting means is according to the order formed by the sub photometric means. (5) A means for uniquely selecting a predetermined value as a sub-target value from a group of candidate values that can be set as sub-target values corresponding to the respective photometric values. Imaging device
(7) The sub-target value setting means performs a calculation considering the level distribution of each sub-target value according to the order formed by the sub-photometric means, and is a candidate that can be set as the sub-target value. The image pickup apparatus according to (5) above, characterized in that it includes means for selecting a predetermined value from the group of values and setting it as a sub-target value .... (8) And a means for setting a sub target value by performing a calculation in consideration of the level distribution of each sub target value according to the order formed by the sub photometric means. Image pickup device (9) When the sub-photometric value deviates from a predetermined level range, the photometric calculation means suppresses the calculation result value of the sub-photometric value and the sub-target value set for the sub-photometric value. Including means to do (10) The image pickup device for photoelectrically converting the subject light through the optical system and outputting the light, and the output signal of the image pickup device for A / D conversion. And a DCT calculation means for obtaining a DCT coefficient by performing DCT calculation for each block when the screen related to this video signal is divided into a plurality of blocks. (1), (2), (3), characterized by being applied as an area
Imaging device according to (4), (5), (6), (7), (8), (9) or (10) ... (11)

[0014]

1 is a block diagram showing the configuration of a digital electronic still camera as one embodiment of an image pickup apparatus of the present invention. In FIG. 1, subject light that has entered the image pickup optical system 1 from a not-shown subject side passes through a diaphragm 2 and is imaged on a photoelectric conversion surface of an image pickup device 3 for photoelectrically converting an image by the image pickup optical system 1. . The output of the image pickup device 3 is supplied to the image pickup process circuit 5 through the preprocess circuit 4. The pre-processing circuit 4 performs so-called pre-processing prior to signal processing in the imaging process circuit 5. In this example, the pre-processing circuit 4 is configured to include an A / D conversion circuit inside itself and performs digital signal processing. The imaging process circuit 5 performs various signal processing necessary for obtaining a signal suitable for a recording operation in a subsequent stage such as color adjustment on the signal supplied from the pre-processing circuit 4, and outputs the output thereof as a recording process. Supply to the circuit 6. In the recording process circuit 6,
Recording information, that is, processing such as compression of digital image data is performed, and output data processed by the circuit is stored in a digital memory card as a recording medium through the memory card interface 7. If an EVF (electronic viewfinder) is provided, the recording process circuit 6 supplies image data to be displayed on the EVF. On the other hand, the signal output from the preprocessing circuit 4 is supplied to an area integration circuit 8 which will be described in detail later. Area integration circuit 8
Is means for calculating a sub-photometric value, which will be described later, for performing exposure control in the apparatus according to the present embodiment,
The integration operation is performed on the digital video signal (luminance signal) supplied from the preprocessing circuit 4. The output of the area integration circuit 8 is input to the microcomputer 9. Since the integration process itself for each area in the area integration circuit 8 is a simple addition operation process, it can be executed by a microcomputer if it is sufficient in terms of processing speed and the like, but it is installed in a normal product. A microcomputer of such a form is not suitable for performing digital integration processing, and therefore it is necessary to prepare a separate integration circuit as in the illustrated example.

The microcomputer 9 performs various processes on the data supplied from the area integration circuit 8,
The main processing is as follows: (a) Sub target value setting processing ... 91 (b) Photometric value calculation processing ... 92 (c) Exposure control determination processing ... In the sub target value setting in (a) above, for example, order determination, level distribution determination, target value selection / calculation, etc. are performed. In the photometric value calculation processing of (b), for example, difference calculation, suppression processing, level standardization, and weighting calculation are performed. In the exposure control determination process of (c), for example, the control deviation is calculated by setting the control target value and comparing the control target value with the photometric value. The above (a) to (c)
The output of the microcomputer 9 including the processing function unit is supplied to the iris driver 10 for adjusting the diaphragm and the imager driver 11 for driving the image sensor 3 so as to obtain the element shutter function. It is configured so that appropriate control of can be performed.

The integration processing for each area in the area integration circuit 8 will be described below. Here, the “area” is a plane area in which the subject exists, and from another perspective, it can be said that the area is the area of the photoelectric conversion surface of the image pickup device 3. In this specification, a plurality of areas virtually divided in this "area" will be referred to as "sub-areas". In addition, the integral value of each "sub-area" when the integration process regarding the video signal level (luminance signal level) is performed for each "sub-area" is referred to as "sub-photometric value". Each of the above "sub areas"
It is common in this type of device to standardize on the area when the areas of are different. The area referred to here corresponds to the number of pixels included in the "sub area" in a device that handles an image signal (video signal) as digital data. That is, in this case, the number of pixels can be treated as a concept equivalent to the area, and when the number of pixels included in each subarea is equal, the sub-photometric value from each subarea is the area. It will have an equal impact on the whole.

On the other hand, in the case where the area of one sub-area is twice as large as that of the other sub-area, even if a subject having the same brightness and luminance is photographed, the sub-photometric value from the sub-area with a large area is obtained. Since it shows a relatively high value, the sub-photometric value from the sub-area whose area is twice as large as that of the other area is divided by 2 and processed to obtain an essentially equal output before the next step. Need to send to processing. However, such processing may be performed as necessary, and in the present embodiment, by setting the areas of the sub-areas to be equal, an output equivalent to that which has already been standardized effectively is obtained. It may be configured to obtain. In this case, so to speak, "area standardization" has been performed.

FIG. 2 shows each sub-photometric area virtually according to the order of allocation of sub-photometric areas to the photoelectric conversion surface (effective imaging area) of the image sensor and the magnitude of the sub-photometric value corresponding to each sub-photometric area. It is a schematic diagram which shows the state rearranged. The total number of pixels in the effective image pickup area of the image pickup element shown in FIG. 2 is 768 in the horizontal direction and 480 in the vertical direction, which is a specification that is relatively frequently used in electronic image pickup such as an electronic camera. As an example of dividing the effective image pickup area of this image pickup device so that the areas of the respective sub-photometry areas are equal, as described above, the left and right end portions of the area are each 9 pixels, and the upper and lower end portions are each 15 pixels. A frame-shaped pixel region to which the photometry of (3) is not assigned is taken, and the region inside the frame-shaped pixel region is divided into 5 × 5 = 25 sub photometric areas.

As a result of dividing the effective image pickup area and assigning the sub-photometric areas in this way, one sub-photometric area is composed of horizontal 150 pixels and vertical 90 pixels. As a luminance photometric value for this one sub photometric area, that is, a sub photometric value, a value of 256 × 150 × 90 is obtained when the quantization per pixel is performed with 8 bits. That is, the maximum value is 3,456,000. Of course, the minimum value is 0.

The numbers 1 to 25 are assigned to all the 25 sub photometric areas described above. This number is represented by N, and the sub-photometric value obtained from each sub-photometric area is S
Represented by (N). The maximum value of the sub photometric value S (N) is 3,456,000 as described above, and the minimum value is 0. Here, for all of these 25 sub-photometric values S (N), they are collectively bracketed {S (N)}.
This is expressed as {D (N)}, and this {S (N)} is rearranged in ascending order from the smallest value. That is, the {S (N)} is distributed correspondingly in 5 × 5 = 25 regions inside the frame-shaped pixel region, and the {S (N)} is rearranged in order from the smallest value {D ( N)} forms a series as shown in FIG. Since {D (N)} is arranged in ascending order, when D is compared with N and N + 1 which is one more than that, D (N + 1) is always greater than or equal to D (N). In other words, D (N) corresponds to any S (N), but the corresponding D (N) for the S (N) always has the magnitude relation as described above.

A value FK is set as a candidate value for the sub-photometric value. FK is defined in the following (Equation 1).

[Equation 1] This (Equation 1) is set based on a certain assumption as an embodiment of the present invention. This assumption is that the maximum value (3,456,000) of one sub-photometric value S (N) corresponds to 120% of the video signal, and 0% of the video signal corresponds to 0 of the digital output (sub-photometric value). Correspondence relations such as “correspondence” are set, and some possible target values are set from the smaller one to the larger one in this range.

A video signal level of 120% is 3,456.
The candidate value FK of the sub-photometric value is made to correspond to the correspondence relationship that 0% is 0 in 000, and 30% is set as F1.
(Because it is a video level, it may be called in a unit of IRE), F2 is 45%, F3 is 60%,
F4 is set to 75% and F5 is set to 90%. In the above, about 60% is regarded as an approximately intermediate video signal level, and 120% is associated with the maximum value of the digital signal quantized by 8 bits as described above, so that it is brighter than this. It stands on the assumption that no state exists.

An arithmetic expression applied to what kind of calculation of the photometric value or setting of the sub target value is actually performed by using each value such as S (N), D (N), and FK defined above. Will be specifically described below. First, the following (Equation 2) is used as the arithmetic expression of the photometric value.

[Equation 2]

(Equation 2) includes both concepts of sub-target value setting and photometric value calculation. That is, for the symbol TS, the photometric value has been set to S in the above-mentioned example, whereas in FIG.
This symbol TS is applied in the meaning of the final photometric value calculated by the block 92 (photometric value calculation) of the embodiment of the present invention, that is, the total photometric value. The same applies to D and FK. The symbol ρ is newly introduced. This is a weighting coefficient used as necessary, and will be described in detail later.

Focusing on the numerator on the right side of (Equation 2), it has a form in which FK is subtracted from D, which means that the target value FK is subtracted from the sub-photometric value. In (Equation 2), the sum of the differences as a result of the subtraction is obtained, which means that the sum of the deviations between each sub-target value and each corresponding sub-photometric value is calculated. It complies with one requirement of item 1.

Focusing on the denominator on the right side of (Equation 2), there is a target value FK, which means that the deviation between each sub-target value and each corresponding sub-photometric value is standardized. Therefore, it corresponds to the claims and claim 2 of the present application.

Further, the right side of (Equation 2) is adapted to be multiplied by a weighting coefficient ρ, which means that a predetermined weighting is applied to each value standardized by the level standardizing means. And corresponds to the scope of claims and claim 3 of the present application.

In (Equation 2), Σ is set to 1 to 5 for K and i. On the other hand, since the candidate value FK of the sub-photometric value is defined by the above-mentioned (Equation 1),
It is a variable that takes different values depending on which of K is 1 to 5. On the other hand, although the definition itself of D is obtained by rearranging S in the ascending order of the values as described above, the expression of 5 (K-1) +2 is taken as an argument in it. This means that when i and K take any value from 1 to 5, the argument in the parentheses of D takes 1 to 25. That is, there are 25 S (N) 's originally, and 25 D (N)' s rearranged, so it is exactly 1: 1.
There is D corresponding to i and K corresponding to. When a certain K and i are specified, the argument in the parentheses of D is 1
Since any one of the values up to 25 is determined and is not duplicated, in other words, if any of the values 1 to 25 of D is designated, K and i corresponding to the designated D are determined. There is a relationship such as. Focusing on this relationship (Equation 2)
Easy to understand the physical meaning of.

As an example of the phenomenon expressed by (Equation 2), what kind of calculation is performed on S (7) obtained from the sub photometric area whose sub photometric value S is 7 will be described. . First, since the sub-photometric values S are rearranged, it is not possible to calculate simply by S (7). In this case, the value of S is 1 from the dark side.
If it is the eighth, it means that S (7) is D (18). Therefore, the fact that the sub-photometric value S is 7 is applied in the form of D (18) in (Equation 1). Looking at what is K and i corresponding to the argument 18 of D (see FIG. 2), K is 4, which corresponds to 1: 1.
It can be seen that i is 3.

In the above case, it is considered to set a sub-target value for S (7) (herein referred to as a sub-target value by the symbol M). This is S (N)
Is set to M (N), it is considered to set the sub-target value M (7) for S (7). Since K is 4 in the above case, the sub-target value M (7) = F4. This F4
Is defined by (Equation 1), and specifically, 7
That is, 2,160,000, which is a value equivalent to 5IRE, is selected.

As described above, all of the sub target values 1 to S (25) corresponding to the sub photometric areas 1 to 25 can be set as described above, and as a result, a predetermined value corresponding to each of them can be set. Sub-target values will be given. This means that for each photometric value D obtained by rearranging the photometric values S, each corresponding K (which one of the sub target value candidates) is determined. Explaining how to determine the sub-target value in this example, 25 pieces of data arranged in ascending order are classified into groups of 5, and F1 is set for the smallest group.
, F2 for the next smallest group, F3 for the middle group, F4 for the next group, and F5 for the largest group. This is the meaning of (Formula 1) described above.

The above-mentioned point is that the target value setting means forms an order of magnitude of each sub-photometric value and sets each sub-target value so as to correspond to the order. The sub-target value setting means corresponds to each sub-photometric value according to the order formed by each sub-photometric means, which corresponds to the feature of one limited aspect (5) in the imaging apparatus of the present invention. In a further limited aspect (7) in the image pickup apparatus of the present invention, which includes means for uniquely selecting a predetermined value as a sub-target value from the group of candidate values that can be set as the sub-target value. Corresponds to the feature of.

Next, how to perform the exposure control will be described. For simplicity of explanation, it is assumed that the weighting factors ρ are all ones. Assuming that ideal control is performed, in that state, each sub-photometric value should match the corresponding sub-target value and the control deviation should be 0. Therefore, TS = (Equation 2) It becomes 0. In other words, it means that it is natural to set TS = 0 as the control target value. However, if consideration is given to various exposure corrections, T
It goes without saying that S = 0 is not always set as the control target value. However, in the present embodiment, TS =
0 is set as the control target value. The operation of setting the control target value is executed in (c) exposure control determination processing 93 in the microcomputer 9 in the block diagram of FIG.

In this exposure control judgment processing operation, TS
When it is = 0, it means that the exposure is appropriate. Therefore, the exposure state is maintained as it is and no change is made. When TS is larger than 0, it means that the photometric value is higher than the target value. Therefore, it is determined that the exposure is overexposed, and the control operation is performed in the direction of lowering the exposure. On the contrary, when TS is smaller than 0, it means that the photometric value is lower than the target value. Therefore, it is determined that the exposure is underexposure, and the control operation is performed in the direction of increasing the exposure. In the adjusting operation for raising or lowering the exposure, the aperture value or the shutter value is adjusted by controlling the aperture or the shutter driver of the image pickup device as described in the block diagram of FIG. When the above control is repeated, a feedback loop is formed, and the deviation is converged and stabilized so that TS = 0, that is, TS = 0.
The above-mentioned point is one limiting aspect in the image pickup apparatus of the present invention in which the exposure control means performs feedback control by changing parameters related to exposure so as to converge the photometric value to a predetermined value. ) Corresponding to the characteristics in.

The weighting coefficient ρ in (Equation 2) will be described below. Once again confirming the suffixes K and i of ρ, K is a number commonly used with K of the target value FK, and the target value changes from a dark target value to a bright target value corresponding to 1 to 5 of K. It is in the form of being compatible. The photometric values corresponding to each of these target values are also values for D rearranged according to the order, and the photometric values corresponding to K of 1 to 5 are arranged in order from dark photometric values to bright photometric values. It is in the form of being. Therefore,
The i of the weighting coefficient ρKi can be treated as an arbitrary value, but for K, this value is 1 for the weighting coefficient corresponding to relatively dark information (or target value) such as ρ1i or ρ2i. If the same value as in the assumption of is set, and the lighter ones such as ρ4i and ρ5i are reduced in weighting value, low-luminance-oriented photometric control is performed.

An example of such low-luminance-oriented photometric control is: ρ1i = ρ2i = 1; ρ3i = 1 /
2; ρ4i = ρ5i = 1/4 is set. Contrary to the above, in the case of performing high-luminance-oriented type photometry control,
Set 1i = ρ2i = 1/4; ρ3i = 1/2; ρ4i = ρ5i = 1. Further, in the case of carrying out the photometric control with emphasis on medium luminance, for example: ρ1i = ρ5i = 0; ρ2i = ρ4i = 1/2; ρ3i
Set to = 1. By setting the weighting coefficient ρ to 0 as in the medium-luminance-oriented type, that is, setting 0 to the extremely bright portion and the extremely dark portion, the data of those portions can be invalidated. In other words, in the concept of applying the weighting coefficient ρ, this coefficient ρ is set to 0
It means that the corresponding data is invalidated by setting.

The weighting coefficient ρ can be selected arbitrarily according to the design, but when handled on a digital computer, if it can be set as 2 to the n-th power, the calculation load can be reduced. In particular, in the case of multiplying 2 by the nth power, if n is selected as 0 or a negative number (meaning that it is not a positive number), 1/2, 1 / is obtained as in the above example.
Since there is a need to select from a series of numbers such as 4, 1/8, there is no need to increase the number of digits according to the increase in the number to be selected, and there is an advantage that the calculation can be simplified.

Next, the level standardization will be described. In the above (Equation 2), as a form of level standardization,
The difference (deviation) between the target value and the photometric value is placed in the numerator, and the difference is divided by the sub-target value. However, in addition to the above, the following (Equation 3), ( It is also possible to take the form shown in Formula 4).

(Equation 3)

(Equation 4) In this (Equation 3), D + FK is placed in the denominator, and in (Equation 4), only D is placed in the denominator. In any case, it is said that the purpose of level standardization is to reduce the influence of the brightness of the subject corresponding to the photometric area as much as possible, that is, treat the data in the bright part and the data in the dark part as equally as possible. Therefore, it is possible to apply various forms as long as it has the meaning of avoiding the influence of partial values from becoming significantly larger. It stands on.

However, it can be said that, ideally, it will take the form of (Equation 3). The reason is that this (Equation 3) has a meaning equivalent to the value of the difference on the numerator side normalized by the average value. In the case of (Equation 2),
Although the denominator does not include D, it is not always desirable that, when the value of D enters the denominator side, the standardization constant changes depending on the sub-photometric value at that time. This is because there may be cases.

Next, a second embodiment of the present invention will be described below. In the second embodiment, the block diagram is the same as that of FIG.
The processing in 1 and 92 is different, and the others are the same. In this embodiment, the calculation of (Equation 5) is executed as the photometric value calculation.

(Equation 5) The first term on the right side of this (Equation 5) has the same format as that of (Equation 2) that TS = Σ · Σ, but as the second term on the right side,

(Equation 6) Is added. This (Equation 6) is a term for adding weighting when processing data according to the position on the screen.

The point to be particularly noted is that the portion exactly the same as (Equation 2) in the first term on the right side has nothing to do with which sub-photometric area the data corresponds to (position), and is exclusively concerned with the photometric measurement. While the sub-target value is set and weighted depending on the order in which the values correspond to the order of brightness, the part of (Equation 6) in the second term on the right side is the data. Is that weighting is performed according to which sub-photometric area (position) corresponds to. In the example presented here, a common value of F3 is applied to the second term on the right side. This F3 can be said to be an intermediate value when viewed according to the definition of (Equation 1). This corresponds to about 60% at the video level, and this F3 is used as a sub target value, and normalization is also performed by this F3. This standardization is, so to speak, “level standardization”, and is also a requirement in the invention of the present application, which produces a particular effect in comparison with the conventional apparatus.

When weighting is performed to give the characteristics of center-weighted photometry in this embodiment, for example, j of ρj is 1 to 6, 10, 11, 15, 16, 16, 20 to 2.
5 may be set to 0. This means that the outer one circumference of the 25 sub light metering areas is weighted to 0 and the data from there is not used. On the other hand, ρ7,
For ρ8, ρ9, ρ12, ρ14, ρ17, ρ18, and ρ19, the weight is set to 1/2. This means that the weight is halved for the region of one round surrounding the center. ρ
Reference numeral 13 is a central area, and 1 is weighted here.
If the above weighting is performed, the second term of the right side (Equation 6)
In this area, the central portion of the area is focused on regardless of the brightness value in each sub-metering area.

It should be particularly noted in the present invention that in (Equation 5), both (Equation 2) of the first term on the right side and (Equation 6) of the second term are taken into consideration. For example, when paying attention to only one certain sub-photometric area, it may occur twice instead of only once in (Equation 5). Specifically, for sub-photometric areas where ρj is not 0 in the second term on the right-hand side (Equation 6), that is, data of an area to which 1/2 or 1 is given as the weighting, A certain weighting has already been made by performing the calculation based on the setting basis that the order of the brightness level is given in the formula 2), and further, which sub-photometric area corresponds to the second term on the right side. That is, the weighting is performed according to (position).

More specifically, assuming that the area S (12) is D (4), it is the fourth from the darkest in (Equation 2) of the first term on the right side of (Equation 5). The data means that it is the sub-photometric value corresponding to the darkest part, and the sub-target value at that time is processed as F1, and is standardized by F1 and its weighting coefficient is 1. Has become. On the other hand, in (Equation 6) of the second term on the right side of (Equation 5), the target value is an intermediate value F3 because it is an area that surrounds the central portion and is standardized by this F3. Therefore, the weighting coefficient is 1/2.

Data of the same area, which are processed based on different grounds, are added with different weights, and the result shows that the overall judgment reflects the meaning of bright or dark TS. Is supposed to get. That is, in the embodiment based on (Equation 5), both the area-based (positional position of the sub-photometry area) determination and the determination corresponding to the order of the brightness levels are taken into consideration at the same time, which is one limitation of the present invention. This is a very characteristic point as an objective aspect. In terms of effects, it is particularly excellent in that it is possible to realize appropriate exposure control that takes into consideration both the factors related to the positional distribution of the sub-photometric area and the degree of the brightness level.

As a modified example of the above-described second embodiment, it is not always limited to the above-mentioned two setting grounds, and it is conceivable to further add other setting grounds. That is, even when a large number of terms processed by the difference from the sub-target value appear in a row, or when it is desired to add various items to be considered, by simply adding these terms, the terms are added. Information on (item) TS
Can be reflected. How much the term (item) is reflected can be arbitrarily set by the processing of the weighting coefficient. Therefore, it is possible to add the third and fourth terms additionally. In addition, in the above-mentioned example, the description has been given mainly of processing the luminance output.
The information obtained from the video signal is not only luminance information but also data relating to color information (for example, chromaticity value). Therefore, even if the data is extracted from the same area, what is its chromaticity value? It is also one preferred embodiment to add a term in which different target values and weighting are performed according to the above.

Next, regarding the setting of the sub target value for the sub photometric value, not only the order of the brightness levels is simply followed, but also the judgment of the brightness distribution is taken into consideration, and a plurality of sub target values are prepared in advance. A third embodiment in which the sub target value candidates are selected will be described.
In this embodiment, the value Ak defined by (Equation 7) is used.

(Equation 7) In this (Equation 7), k is an integer of 0-5. The denominator of (Equation 7) is 5, and the numerator is k × MAX {S (N)} as the first term and (5-k) × MIN {S (N)} as the second term. The meaning of this (Equation 7) will be described with reference to FIG. 3. When 0 or 5 is substituted for k, the MIN
The values are {S (N)} and MAX {S (N)}. When k takes a value of 1 to 4 in the meantime, it takes a value which is obtained by equally dividing between A5 and A0 which are just MAX and MIN.

The reason for using Ak as described above is to enable the case-separated processing using the coefficient αN, K in the following (Equation 8) for calculating TS. . For a certain area N, the sub-photometric value S (N) always exists as a value between MAX and MIN. The sub-photometric value S (N) has a shape corresponding to which one of the five equally divided level ranges shown in FIG.
(N) is between A0 and A1, between A1 and A2, or between A2 and A3
Or A3 to A4 or A4 to A5. The equation (8) using such Ak is as follows.

(Equation 8) Analyzing this (Equation 8), two coefficients, that is, coefficients αN, K, are obtained for the value obtained by subtracting the sub target value FK from the sub photometric value S (N) in the numerator and the denominator of FK. And weighting coefficient ρ K (for weighting according to brightness)
It means that Σ with K of 1 to 5 is prepared for the product obtained by multiplying by, and Σ of N = 1 to 25 corresponding to 25 areas of N is taken for this Σ. Coefficient α
The definition of N, K is 1 when S (N) is between Ak-1 and Ak, and 0 otherwise.

As the processing at the end point, S (N) = A5 is also set to 1. However, the idea is to determine whether α becomes 1 or 0 by dividing the case as described above. S in any of the areas (level ranges) in FIG.
It corresponds to whether the value of (N) belongs. That is, a certain K
When the second stage is entered, α is set to 1, and when it is not entered, it is set to 0. As a result, the sub-metering between A4 and A5 at the top of the five-stage classification is performed. For the value, a sub-target value of F5 is given. If there is a sub photometric value between A2 and A3 in the middle, a sub target value of F3 is given. That is, the sub target value for each S (N) is obtained by classifying the brightness distribution of the subject into five levels and allocating F1 to F5 according to the respective brightness.

In the above-described second embodiment, the sub-photometric values are rearranged in the order of brightness and are divided into five parts, and F1 to F5 are assigned, so that the values are actually very bright. Even if there are many bright areas with 10 bright areas and the rest are dark, the processing is performed unconditionally in increments of 5. However, in the third embodiment, processing that reflects the distribution state of luminance is performed. However, more appropriate exposure control can be performed.

Next, a fourth embodiment of the present invention will be described below. The fourth embodiment is the same as the above-mentioned third embodiment.
In the embodiment, the corresponding sub-target value is selected from preset sub-target value candidates, but the difference is that the optimum sub-target value is calculated. The arithmetic expression for obtaining the optimum sub target value in this case is the following (Equation 9).

[Equation 9] M (N) in (Equation 9) corresponds to the sub-target value for S (N) described in the first embodiment. In this case, M (N) is directly calculated by the proviso of (Equation 9). In this proviso, MAX {S (N)} is also used for the calculation, but the meaning of this expression can be easily understood with reference to FIG. In the above description, the values of F are F1 to F5, but F0 and F6 are set as the values of F in FIG. However, the symbol (value) of F ~ is defined by the above-mentioned (Equation 1), and by substituting 0 and 6 into K of this equation, these F0 and F6 can be obtained. This corresponds to a video signal level of 15% and 105%, and is set as a representative of a fairly dark value and a fairly bright value.

In the above, what value to correspond to is to be determined according to design circumstances. For example, instead of F1 described above and F0,
Even if F is applied instead of F6, it operates as a photometric system, but it is expected that F0 and F6 described above can obtain more appropriate characteristics. The setting of M (N) in the proviso of (Equation 9) is performed by setting the MAX of the value of S (N) which is being focused on among various values of the sub-photometric value S (N) as shown in FIG. , MIN, the ratio of the target value M (N) to be given this time to F6 in the bright part and F0 in the dark part, which are considered as control target values, should be the ratio between F6 and F0. Means

Naturally, according to the brightness of the subject, the idea that a bright place is a bright target value and a dark place is a dark target value is the basis of the present invention. Therefore, if this is taken to the extreme, It is ideal to set the target value corresponding to the distribution ratio, and the fourth embodiment can be considered. Here, once again, the target value M (N) is not selected as one of the prepared target value candidate values, but is merely calculated according to the level distribution of the sub-photometric value at that time. It is given by.

Next, a fifth embodiment of the present invention will be described below. This embodiment does not seek any special characteristics regarding the setting of the sub target value and the calculation method of the sub photometric value, and it is possible to apply those in the above-mentioned respective embodiments to these. The sub-photometric value detection unit has a feature. FIG. 5 shows the fifth aspect of the present invention.
3 is a block diagram showing an embodiment of FIG. In this embodiment, an image sensor for photoelectrically converting subject light through an optical system and outputting the same, and a digital video signal obtained by A / D converting an output signal of the image sensor are provided with a plurality of screens related to the video signal. DCT calculation means for performing DCT calculation for each block when the block is divided into
Is further provided, and the block is applied as the sub photometric area.

The embodiment of FIG. 5 will be described in comparison with the embodiment of FIG. Parts corresponding to those in FIG. 1 are designated by the same reference numerals. In FIG. 1, the block 8 has an area-by-area integration circuit section, but this circuit section integrates the output data from the preprocess 4 for each sub-photometry area. On the other hand, in the configuration of FIG. 5, there is no circuit portion for performing this integration. Instead of this, as shown in detail in the recording process circuit portion of the block 6, a DCT operation unit 61 is provided inside this.

In the DCT operation section 61, the amount of data supplied to the recording process section circuit 6 is very huge, and if the data is recorded as it is, the required capacity of the storage device becomes too large, which is uneconomical. Alternatively, since there is a problem that the data recording time also becomes long, the information is compressed to deal with such a problem. D
The CT operation (Discrete Cosine Transformation) is one of the methods that have been widely used in recent years to compress the information of a still image for the above purpose. In this DCT operation, one wide image area (pixel area) to be compressed is divided into a plurality of sub-blocks, and the internal data of each sub-block is converted into the frequency domain. The amount of information is compressed by performing a process of thinning out unnecessary data from the data converted into the frequency domain. By converting to the frequency domain, the low frequency domain, ie
Coefficients (DC coefficients) that are DC or close to DC with little or no spatial change are always calculated for each block.

The DC coefficient mentioned above corresponds to the average value of the luminance in the block. Therefore, the DC coefficient has a meaning that it can be used as the sub-photometric value in the block, and this point is used in the fifth embodiment. That is, the division into sub-blocks for performing DCT calculation corresponds to the division into sub-photometry areas, and the DC coefficient of each sub-block corresponds to the sub-photometry value. It is intended to set a sub-target value for each meaningful sub-block and perform exposure control that makes the most of the features of the present invention.

FIG. 6 is a schematic diagram showing a screen division situation in the embodiment of FIG. FIG. 6 corresponds to the screen described in FIG. 2, and is composed of horizontal 768 × vertical 480 pixels. In the present embodiment, it is planned to use the screen (imaging device) having such a configuration, but the applicable screen (imaging device) is not limited to this. Figure 7
FIG. 9 is a schematic diagram showing a state of a screen by another image pickup element applicable to the embodiment of FIG. The one shown in FIG. 7 is composed of horizontal 640 pixels × vertical 480 pixels. How to set the DCT block is a design choice,
The most commonly used one is to divide one block into blocks each having 8 × 8 pixels and 8 × 8 = 64 pixels. In this case, in the image sensor of FIG. 6, the number of areas is 5760 blocks of 96 × 60 blocks, and in the image sensor of FIG. 7, the number of blocks is 80 × 60.
4800 blocks. DC for each of these blocks
The average value of the luminance signal corresponding to the sub-photometric value is obtained as a coefficient.

Although the number of these blocks is much larger than that of the 25 sub-photometric areas described above, the present invention originally performs a fine exposure control reflecting the situation of each partial area. Since it is intended, it is possible to perform ideal control in line with the spirit of the invention by subdividing the sub-photometry area (block) as finely as possible within the capability of the arithmetic function unit. On the contrary, if the sub-photometric area is made too rough (large), there may occur a boundary of a region that cannot be regarded as one region of the subject. For example, even if a photometric value with the same intermediate value is detected, there is actually a subject with intermediate brightness, and there are half a bright object and half a dark object, resulting in an intermediate value. The meaning of the phenomenon is different from the case where a specific value is detected. The idea underlying the present invention is to apply various photometric target values and control methods on the premise that photometric values are obtained such that each place is bright, dark, or intermediate. Therefore, it is expected that a preferable result can be expected rather by setting the sub-photometric area by dividing it into a large number (finely) as described above.

Except for the fifth embodiment, the case where the sub photometric area is 25 has been described.
One is for convenience of explanation. However, it can be said that setting at least this level is sufficient for realizing the preferable exposure control expected in the present invention. Further, if the sub-photometric area is not divided into too many areas and set, the burden on various arithmetic function units is reduced, and the advantage that a simple and inexpensive device as a whole can be realized cannot be overlooked.
Therefore, in the fifth embodiment, it is also possible to simplify the configuration by configuring the result of addition processing performed on some blocks in advance as each sub-photometric value. That is, one block of the DCT can be associated with one sub-photometric area, or a plurality of blocks of the DCT can be associated with one sub-photometric area. A block "block addition" shown by a broken line in the block 9 of FIG. 5 is a functional block for the above-mentioned addition processing applied in the latter case.

It is difficult to realize the configuration in which the output from the pre-process is immediately integrated completely as in block 8 in FIG. 1 unless the data processing speed is sufficiently high. If the processing is performed on the result value that has undergone a certain amount of processing such as output, it becomes possible to perform this arithmetic processing in the microcomputer. Therefore, by adopting such a configuration, for example, even in the processing having 25 areas as in the first embodiment, the DC coefficient of the DCT calculation can be used without separately providing an area-specific integrating circuit. The same processing can be realized with.

Next, a sixth embodiment of the present invention will be described below. In this embodiment, the following (Equation 10)
Set the target value for control by.

(Equation 10) The sixth embodiment differs from the first embodiment in that the coefficient βK, i is further multiplied. As understood from the proviso of (Equation 10), K = 1
~ 4, that is, the 20th data from the darkest (D (1)
.About.D (20)), the coefficient .beta.K, i has no effect. It has an effect only when K = 5 and only when D (20 + i) ≧ F5.
According to (Equation 1), since F5 = 2,592,000, it may be described as such, but it is described as above for simplification of the description. Also, the numerical value 3,456,000
Is the maximum value that D (N) can take, as described above. now,
The sub-target value for D (20 + i) is F5 because K = 5. Therefore, if the brightness distribution of the subject is within an appropriate range, the control result will approach D (20 + i) = F5, or if D (20 + i) <F5 and the control is stable, the brightest category will be obtained. This also means that the subject is reproduced as a signal of a sufficiently low level (not too bright), so there is no problem. But,
In the case of D (20 + i)> F5, the control is stable despite the result of "overexposure". Therefore, this is "underexposure" in other terms. It suggests that it exists.
If such other term is the low luminance portion, the result is that "the low luminance portion is underexposed even at a low target level, and the high luminance portion D (20 + i) is at a high target level F5.
However, there is a possibility that so-called black underexposure or underexposure may occur in the image.

Therefore, it is necessary to save the occurrence of so-called black crushing and white crushing. The control that can be taken in such a case is to abandon the reproduction of one of the low-luminance portion and the high-luminance portion and save only the other. The coefficient β K, i takes the following values (Table 1) according to the value of D for the five high-intensity terms of K = 5.

[Table 1] Therefore, “when the high-luminance portion is equal to or less than the target value F5, the same control as that of the first embodiment is performed, but as it becomes larger than F5, the degree of contribution of the term of the high-luminance portion to the control is increased. By suppressing it, the faithful reproduction of this high-brightness part is abandoned. " Thereby, reproducibility of other parts can be secured.

In the above, the effect of "suppressing the degree of contribution to control" is that "the sub-photometric value exceeds the predetermined level range by the photometric calculation means in one limiting aspect (10) of the image pickup apparatus of the present invention. It includes a means for suppressing the calculation result value of the sub-photometric value and the sub-target value that is set for the sub-photometric value, which corresponds to "suppressing the calculation result value of the sub-target value". It is a thing.

Also, the coefficient βK, i = 0 may occur. In this case, the concept of "suppression" may include "disabling". Furthermore, in the example of (Table 1) above, βK, i is D (2
0 + i) changes continuously (increase or decrease) with respect to the value of 0 + i), but this means that control is performed smoothly and naturally, and reproduction of high and low luminance parts is reproduced at the maximum. However, βK, i is not limited to this, and may take a value that changes appropriately discontinuously. Furthermore, in the above example, "suppression" is performed on the high-luminance part,
It goes without saying that the low-luminance portion may be targeted.
Alternatively, it may be applied to other conditions, or may be applied simultaneously to a plurality of conditions as required. Furthermore, in the above-mentioned example, it is realized by additionally multiplying the coefficient βK, i based on the first embodiment, but the basic configuration can be arbitrarily selected, and its realizing method (format) is also arbitrary. .

In each of the above embodiments, the number of pixels in one screen is 768 × 480, for example.
When this is the number of pixels of a so-called 1-frame screen in an NTSC system 2: 1 interlaced video signal, various signal processing in an actual image pickup device is often executed in units of a so-called 1-field screen. When processing is performed in units of one field screen as described above, it is sufficient to set each target value by setting the number of pixels in one screen to 768 × 240, assuming that the number of pixels in the vertical direction is half.

Although the above example is an electronic still camera using a digital memory, the present invention can be applied to various photographing devices including a video camera recorder, a silver salt still camera, and a silver salt cinema camera. .

The above-mentioned invention of the present application, the constitutions seen in various limited aspects thereof, the problems solved by them, and the effects as the invention will be summarized below.

(1) The whole or a part of the photographing screen is divided into a plurality of areas, and each area is defined as a sub-photometry area,
Sub-photometric means for obtaining the sub-photometric value corresponding to the brightness of the subject to be photographed for each photometric area, and the sub-photometric target to be separately reached for each sub-photometric value output from the sub-photometric means A sub-target value setting means for setting a value, and a total sum of deviations between the sub-target values set by the sub-target value setting means and the corresponding sub-photometric values An image pickup apparatus comprising: a calculation unit for obtaining an exposure control amount; and an exposure control unit for controlling exposure related to the photographing based on the exposure control amount obtained by the calculation unit.

In the prior art prior to the invention of (1) above,
It has been difficult to determine the optimum exposure value that separately considers the different brightness of each part in the screen to be captured. The invention of (1) above has a simple structure that does not include a complicated and costly component such as an automatic tracking device or a fuzzy inference circuit, and obtains suitable exposure for various subject scenes including a backlight scene and the like. The present invention intends to provide an image pickup apparatus capable of performing the above.

According to the invention of the above (1), since the individual target values are given to the respective sub-photometric values, the bright target value is bright, the dark target value is dark, and the intermediate brightness is bright. , An intermediate or average target value is given to each of them, and an exposure in consideration of the brightness range of the image pickup system can be obtained.

In the invention of the above (1), the brightness range is, in other words, a brightness reproduction area.
As described above, the imaging system cannot reproduce everything from bright areas to dark areas. Therefore, when attempting to perform exposure control that is as appropriate as possible within the reproducible range, use the invention described in (1) above. Exposure control is desirable.

(2) The calculating means includes level standardizing means for normalizing the levels of the respective deviations between the respective sub-photometric values and the corresponding sub-target values. The imaging device according to (1) above, characterized in that there is.

In the technique prior to the invention of the above (2), no particular consideration was given to how the influence of the bright portion and the influence of the dark portion of the subject are associated and reflected in the exposure control.

According to the invention of the above (2), in addition to the effect of the invention of the above (1), in particular, the information amount of the bright portion and the information amount of the dark portion of the subject are treated equally, so that as a whole. The effect that the influence of the bright part is not received too strongly is exerted.

In the invention (2), the level standardization means standardizes the level. This is a concept that should be distinguished from the above-mentioned "standardization regarding the area", and this also means that the standardization regarding the area is performed in the present embodiment and then the standardization regarding the level is further performed. It will be understood from that. In other words, the fact that the area is standardized only guarantees that the same value can be obtained from each area when there is a subject with the same brightness, and areas with different brightness are not guaranteed. Regarding a certain field (an image in which a bright subject and a dark subject are mixed), how the influence of the bright portion and the influence of the dark portion contribute to the exposure adjustment cannot be adjusted at all. In a conventional operation such as normal weighting or simple weighting addition / subtraction that does not perform standardization but only takes a difference, the proportion of the output from the bright portion as a numerical value becomes high, and the influence of this bright portion is dominant. Tend to be next door. Level normalization is effective in suppressing the tendency that the influence of such bright areas becomes dominant.

(3) The calculating means includes level standardizing means for normalizing the respective levels between the respective photometric values and the respective sub-target values corresponding thereto, and the level standardizing means. The image pickup apparatus according to (1) above, further comprising: a weighting unit that weights each value standardized by the converting unit.

According to the invention of the above (3), in addition to the effect of the invention of the above (1), it is possible to perform the focus exposure control particularly regarding the brightness distribution of the subject and the like.

(4) The exposure control means performs feedback control by changing parameters relating to exposure so as to converge the photometric value to a predetermined value, and (1) and (2) above. Alternatively, the imaging device according to (3)

According to the invention of the above (4), the above (1),
In addition to the effect of the invention of (2) or (3), in particular, exposure control can be performed very easily and stably.

(5) The sub-target value setting means forms an order of magnitude of each sub-photometric value and sets each sub-target value so as to correspond to the order. Characteristic above (1), (2), (3) or (4)
Imaging device according to

According to the invention of the above (5), the above (1),
In addition to the effects of the invention of (2), (3) or (4),
In particular, the calculations for photometry and exposure control become very simple. Since the ordering simply rearranges the order according to the magnitude relationship, processing based on it will greatly simplify the above calculation.

(6) The sub-target value setting means sets a plurality of sub-target values based on different setting grounds as the sub-target values to be set corresponding to the respective sub-photometric values, and the above-mentioned calculation is performed. The means includes means for performing a different calculation for each of the plurality of sub target values with respect to each of the sub photometric values and obtaining the photometric value from the result of the different calculation. , (2), (3) or (4) the imaging device according to

According to the invention of the above (6), the above (1),
In addition to the effects of the invention of (2), (3) or (4),
In particular, it is possible to perform delicate and high-level exposure control in which both the brightness distribution on the screen and the order of brightness or other elements related to photometry are considered in any distribution.

(7) The sub-target value setting means selects from among a group of candidate values which can be set as sub-target values corresponding to the sub-photometric values according to the order formed by the sub-photometric means. The image pickup apparatus according to (5) above, further including means for uniquely selecting a predetermined value as a sub-target value.

According to the invention of (7) above, in addition to the effect of the invention of (5) above, in particular, a process relating to exposure control can be performed very easily.

When the format is selected from the target values prepared in advance, the candidate values to be prepared in advance are fixedly held in, for example, the EE / PROM.
If this fixed value can be relatively easily rewritten by another means, it is easy to give various variations of the control, and the control system has a simple structure. The feature is added. This is a great advantage particularly when the present invention is systematically configured.

(8) The sub-target value setting means performs a calculation considering the level distribution of each sub-target value according to the order formed by the sub-photometry means, and is a candidate value that can be set as a sub-target value. The image pickup apparatus according to (5) above, further including means for selecting a predetermined value from the group of and setting it as a sub-target value.

According to the invention of (7) above, in addition to the effect of the invention of (5) above, in particular, delicate exposure control is performed in consideration of both the order of brightness and the brightness distribution on the screen. Is possible.

(9) The sub-target value setting means includes means for setting a sub-target value by performing calculation in consideration of the level distribution of each sub-target value according to the order formed by the sub-photometric means. The image pickup apparatus according to (5) above, which is an optical image pickup apparatus.

According to the invention of (9) above, in addition to the effect of the invention of (5) above, in particular, delicate exposure control is performed in consideration of both the order of brightness and the brightness distribution on the screen. Is possible.

(10) The photometric calculation means is means for suppressing the calculation result value of the sub photometric value and the sub target value set for the sub photometric value when the sub photometric value deviates from a predetermined level range. The imaging device according to (5) above, which includes:

According to the invention of the above (10), the above (5)
In addition to the effect of the invention, it is possible to perform the exposure control that gives priority to the reproducibility of either one of the areas only when the brightness difference between the high brightness portion and the low brightness portion on the screen is too large. .

(11) An image sensor for photoelectrically converting the subject light through the optical system and outputting it, and a plurality of screens related to this image signal in a digital image signal obtained by A / D converting the output signal of this image sensor. DC for obtaining DCT coefficients by performing DCT calculation for each block when divided into blocks
T calculation means is further provided, and the block is applied as the sub-photometry area.
(2), (3), (4), (5), (6), (7),
Imaging device according to (8), (9) or (10)

According to the invention of the above (11), the above (1), (2), (3), (4), (5), (6),
In addition to the effects according to the invention of (7), (8), (9) or (10), it is essential in particular to perform a DCT operation which is one operation method of data compression which is becoming popular in this type of device. By using each block when the screen is divided into a plurality of blocks, the exposure control can be performed with a simple structure without newly setting division of the sub-block.

[0096]

EFFECTS OF THE INVENTION In the screen, a bright target value is given to a bright part, a dark target value is given to a dark part, and an intermediate or average target value is given to an intermediate brightness part. A suitable exposure can be obtained in consideration of the brightness range of the image pickup system.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a digital electronic still camera as one embodiment of an image pickup apparatus of the present invention.

[Fig. 2] Virtually rearranging each sub-photometric area according to the order of allocation of sub-photometric areas to the photoelectric conversion surface (effective imaging area) of the image sensor and the magnitude of the sub-photometric value corresponding to each sub-photometric area. It is a schematic diagram which shows the state which was done.

FIG. 3 is a diagram for explaining an arithmetic expression (Equation 7) in the embodiment of the present invention.

FIG. 4 is a diagram for explaining an arithmetic expression (Equation 9) in the embodiment of the present invention.

FIG. 5 is a block diagram showing a fifth embodiment of the present invention.

FIG. 6 is a schematic diagram showing a screen division situation in the embodiment of FIG.

FIG. 7 is a schematic diagram showing a state of a screen by another image pickup element applicable to the embodiment of FIG.

[Explanation of symbols]

 1 Imaging Optical System 2 Aperture 3 Image Sensor 4 Pre-Process Circuit 5 Imaging Process Circuit 6 Recording Process Circuit 61 DCT Calculation Section 7 Memory Card Interface 8 Area Integration Circuit 9 Microcomputer 91 Sub-Target Value Setting Processing 92 Photometric Value Calculation Processing 93 Exposure Control Judgment processing 94 Block addition 10 Iris driver 11 Imager driver

Claims (3)

[Claims] 1. An entire area or a part of a photographic screen is divided into a plurality of areas as sub-photometric areas, and a sub-photometric value corresponding to the brightness of the subject to be photographed is set for each sub-photometric area. Sub-photometric means for obtaining, sub-target value setting means for setting a sub-photometric target value that should be reached separately for each sub-photometric value output from the sub-photometric means, and set by the sub-target value setting means Computing means for computing the sum of the deviations of the respective sub-target values and the respective sub-photometric values corresponding thereto to obtain the exposure control amount for the subject to be photographed; and the exposure obtained by the computing means. An image pickup apparatus comprising: an exposure control unit that controls an exposure related to the photographing based on a control amount. 2. The calculation means comprises level standardization means for standardizing the levels of the respective deviations between the respective sub-photometric values and the corresponding sub-target values. The image pickup apparatus according to claim 1, wherein 3. The level normalizing means for normalizing the level of each deviation between each photometric value and each sub target value corresponding thereto, and the level normalizing means. The image pickup apparatus according to claim 1, further comprising a weighting unit that weights each value standardized by the unit.