JP2002199271A - Image pickup device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image pickup device that conducts iris control or the like by an optimum time and an optimum data capacity by selectively revising the number of division areas of an image pickup object face corresponding to fluctuation in a luminance level of an image pickup object. SOLUTION: An integration means having a specific division area and a means that calculates a standard deviation from integrated values by each division area calculate a fluctuation evaluation value of luminance levels of an image pickup object, the number of optimum division areas is decided from the fluctuation evaluation value and the integration means that integrates the luminance of the image pickup object by the number of optimum divisions calculates the luminance evaluation value of the image pickup object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a digital integrator used for an exposure adjusting device such as a digital still camera and a focusing device.

[0002]

2. Description of the Related Art An ordinary iris apparatus includes an auto iris apparatus that divides an object to be imaged into a plurality of regions and controls a luminance evaluation value obtained from a value obtained by integrating luminance signals in each divided region to a target value. AE apparatus), and an integrating circuit is used to calculate the luminance evaluation value.
In this integrating circuit, the number of divided areas of the imaging screen is fixed to one such as 64 divisions or 128 divisions in advance. A luminance evaluation value, which is an integrated value of a luminance signal, is calculated by an integrating circuit having a fixed number of divided areas, and the iris is controlled to an optimal state by a control program of a microcomputer.

In general, an AE apparatus is realized by obtaining a luminance evaluation value from the entire area of an object to be imaged and adjusting the aperture diameter of a diaphragm or the shutter speed. Thus, when there is no variation in the luminance signal level itself of the imaging target (in a state of low density), the imaging target can be almost certainly photographed with appropriate brightness. However, when the luminance signal level of the imaging target itself varies (in a state where there are many shades and a complicated pattern), the density of the imaging target is averaged, so that the main subject in the imaging target becomes dark. May be. Therefore, the imaging target area is divided into a plurality of parts, the brightness evaluation value in each area is obtained, and the weighting coefficient is assigned to the brightness evaluation value of each area, so that the imaging target is photographed with appropriate brightness. I have.

FIG. 3 (a) shows an example of a weighting factor for each area. In this example, the imaging target is divided into 16 regions, and the weight coefficient of four 2 × 2 regions located at the center is 5, and the weight coefficient of 12 regions located at the periphery is 1. Is set. If the subject is located at the center of the imaging target, the luminance signal of the background in the peripheral part is difficult to be reflected in the luminance evaluation value. You can shoot with brightness.

[0005] As described above, in the conventional imaging apparatus, it is determined from the luminance information that the subject to be imaged is located at the center, the left and right ends, and the like, and the right end is determined as shown in FIG. It can be changed to a weighting factor that emphasizes.

[0006]

However, if there is a variation in the luminance signal level of the object to be imaged within the divided single area, the luminance evaluation value of the single area is an average value of shading, so that the object to be imaged is optimized. You may not be able to shoot at a high brightness. In the case where there is such a variation in the luminance level, by dividing the divided area of the imaging target into smaller pieces, it is possible to allocate a more optimal weight coefficient to the variation in the luminance signal level of the imaging target as shown in FIG. it can.

When the variation in the luminance signal level of the object to be imaged is small, fine division is not required, and the integrated value calculated as the number of divided areas increases is large. It only consumes quantity. In addition, when the luminance signal level of the imaging target has a large variation, if the number of divided regions is small, averaging is performed in units of divided regions. Will be included.

Therefore, a main object of the present invention is to optimize the number of divided areas of an integrating circuit in accordance with variations in the luminance signal level of an object to be imaged. It is possible to obtain an evaluation value to be performed.

[0009]

According to a first aspect of the present invention, there is provided an image pickup apparatus having a digital integrator for obtaining a luminance level or the like of an object to be imaged from an image signal taken by an image sensor. Integrating means for calculating an integrated value of different numbers of divided areas; calculating means for calculating a variation evaluation value of the brightness level itself of the imaging target; and determining an optimal number of divided areas for the variation from the variation evaluation value of the brightness level. The imaging apparatus includes a digital integration device including a selection unit and an evaluation value calculation unit that calculates a luminance evaluation value for setting an exposure to an optimum value from the integrated value of the integration unit.

According to a second aspect of the present invention, there is provided an image pickup apparatus having a digital integrator for obtaining a luminance level or the like of an object to be picked up from an image signal taken by an image pickup device. Calculating means for calculating a variation value of the brightness level itself; determining means for determining an optimal number of divided areas for the variation from the variation value of the brightness level; and an integration value of an optimal number of divisions among the plurality of integration means. This is an imaging apparatus provided with a digital integrator including selection means for setting a luminance evaluation value.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an overall block diagram of the apparatus of this embodiment. The camera 1 has a focus lens 10
The light of the subject incident from the focus lens 10 is transmitted through the aperture mechanism 11 to the CCD imager 1.
2 is irradiated. On the front of the CCD imager 12, 3
A color filter (not shown) in which primary color filter elements are arranged in a Bayer array is mounted. As a result, a pixel signal having any one of R, G, and B primary color components is output from the CCD imager 12 and is converted by the A / D converter 13 into pixel data that is a digital signal.

A timing generator (TG) 21 which operates in response to a shutter speed instruction signal output from the microcomputer 19 controls the exposure time of the CCD imager 12 and sends a timing signal to a memory control circuit 22 so that a pixel signal is transmitted. Data is written to the DRAM 14. The pixel data held in the DRAM 14 is thereafter read out by the memory control circuit 22 and the signal processing circuit 1
5 is input.

The signal processing circuit 15 calculates luminance data (Y data) and color difference data (RY data and BY data) based on the input R, G and B pixel data. The signal processing circuit 15 inputs the calculated color difference data to a white balance adjustment circuit (not shown), and inputs the Y data to a fixed division integration circuit 16 having a fixed number of division areas. FIG. 2 (a) shows the fixed divided area.
Shown in Here, the entire imaging target is divided into eight equal parts in the vertical direction and eight equal parts in the horizontal direction, and divided into 64 regions.

The fixed division integration circuit 16 integrates the input Y data for each of the 64 divided areas and supplies it to the SD calculation circuit 17. The SD calculation circuit 17 includes a fixed division integration circuit 16
The standard deviation (SD data) of the 64 integrated values output from is calculated and input to the selection circuit 18. This standard deviation value is equivalent to the variation evaluation value S _Y of the brightness level of the imaging target, and when the variation that the imaging target has a complicated luminance change is large, the variation evaluation value S _Y becomes large, Conversely, when the imaging target is smooth with little change in luminance, the variation evaluation value S _Y becomes small.

The selection circuit 18 obtains the optimum number m of divided areas based on the variation evaluation value S _Y input from the SD calculation circuit 17. If the variation evaluation value S _Y is large, an integrated value of a finer area is required, so the number of divided areas is increased. Conversely, when the variation evaluation value S _Y is small, the integrated value of a fine area is not required, so that the number of divided areas is reduced. As a specific example, when the variation evaluation value S _Y is less than the predetermined value A, the optimal division number m is set to m as shown in FIG.
= 64, and when the variation evaluation value S _Y is equal to or more than A, the optimal division number m is set to an optimal division number m according to the variation evaluation value S _Y , such as m = 128 as shown in FIG. m
Is determined. A is a value previously obtained by an experiment. Although the present embodiment has been described using two divided areas of 64 and 128, the number of divided areas and the type of division are not limited.

When the optimum division number m is determined, iris control and the like are executed. Specifically, the optimal division number m output from the selection circuit 18 is taken into the microcomputer 19 and passed to the optimal division integration circuit 23. Optimal division integration circuit 23
Again, type Y data from the signal processing circuit 15 calculates the integrated value I _M for each divided region. The microcomputer 19 calculates a target value and an integrated value I _M for obtaining a preset optimum exposure amount.
Is compared with the luminance evaluation value I _{Y of the} entire screen, which is the sum of m divided areas of the motor driving circuit 20.
And a shutter speed instruction signal to the TG 21 at the same time.
The shutter speed of the CD imager 12 is controlled.

The microcomputer 19 performs the above processing when the release button (not shown) is half-pressed or when a finger is touched, and determines the optimal exposure amount. When the release button is depressed, the microcomputer 19 turns on the switch 24 and sends pixel data from the DRAM 14 to the signal processing 2.
Enter 5 In the signal processing 25, signal processing and data compression suitable for the recording medium 26 are performed and recorded.

FIG. 4 is a block diagram showing another embodiment. Since the structure from the camera 1 to the signal processing circuit 15 is the same as that of FIG. 1 showing the above embodiment, the description is omitted, and the signal processing circuit is omitted. Only the configuration after 15 is shown. That is, the different part is the configuration of the integration means for calculating the luminance evaluation value of the imaging target, that is, the configuration of the fixed division integration circuit 16, the optimal division integration circuit 23, and the like.

Y data calculated by the signal processing circuit 15
Is divided into 64 by dividing the integration area of the imaging target into 64.
To the circuit 30 and the 128-division integrating circuit 31, respectively.
You. The DRAM 32 temporarily stores the integrated value for each divided area.
It is for holding. Temporarily accumulated integration results
Of which is obtained by the 64 division integrating circuit 30
The value is supplied to the SD evaluation circuit 33 and integrated for each divided area.
Calculate the standard deviation of the values. The SD evaluation circuit 33 calculates
The standard deviation thus obtained is, as described above, a variation evaluation value S. _YTona
If the value is smaller than the predetermined value A, the 64 division integrating circuit 30 is selected.
In the case of A or more, the 128-division integrating circuit 31 is selected.
The selection control signal indicating selection is sent to the division number selection circuit 34.
Supply. The number-of-divisions selection circuit 34 is based on the selection control signal.
And the integrated value of the 64 division integrating circuit 30 or 128 division
Either of the integrated values of the integrating circuit 31
The luminance evaluation value is passed to the microcomputer 19. Then my
In the process of the controller 19, the target value and the luminance
Optimize aperture value and shutter speed from evaluation value
Exposure control will be performed. In the description of the present embodiment, 64
Although division and 128 division were used, this division number and the division number
There is no restriction on the type.

In both of the above embodiments, the exposure control has been described. However, as in the focus control and the white balance adjustment,
It is needless to say that the imaging screen can be used to divide the imaging screen into a plurality of regions and evaluate the degree of focusing and the distribution of color information.

[0021]

As described above, according to the present invention, the number of divided regions of the integrating circuit is always kept at an optimum value for the variation in the brightness level of the object to be imaged. The number of integrated values from the circuit is optimal. Therefore,
The calculation time of the integrated value is shortened, and the data capacity for holding the calculation result is not wasted.

[Brief description of the drawings]

FIG. 1 is a block diagram schematically illustrating an imaging apparatus according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an example of a divided region of an integrating circuit that is a part of the imaging apparatus in FIG. 1;

FIG. 3 is a diagram illustrating weighting factors of divided regions corresponding to luminance information of an imaging target.

FIG. 4 is a block diagram showing a part of an imaging apparatus according to another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Camera 10 ... Focus lens 11 ... Aperture mechanism 21 ... Timing generator (TG) 24 ... Switch

Claims (5)

[Claims] A calculating means for calculating a variation in luminance information of the imaging screen; a selecting means for selecting a number of divided areas of the imaging screen in accordance with the variation; and a first integrating means for integrating luminance information for each divided area. An imaging device comprising: 2. The method according to claim 1, wherein the calculating means calculates the variation by obtaining a standard deviation from an output value of the second integrating means for integrating the luminance information for each specific divided area. Imaging device. 3. The imaging apparatus according to claim 2, wherein the selection unit determines an optimal number of divided areas for the variation of the second integration unit. 4. According to the number of different divided areas of an imaging screen,
A plurality of integrating means for integrating the luminance information for each divided area; a calculating means for calculating a variation in the luminance information of the imaging screen; and the plurality of integrating means for providing the optimal number of divided areas for the variation calculated by the calculating means An imaging apparatus comprising: a selection unit that selects one of the integration units. 5. The method according to claim 1, wherein the calculating means calculates the variation by obtaining a standard deviation of an integrated value obtained from the integrating means, which is a specific number of divided areas, among the plurality of integrating means. The imaging device according to claim 4.