JP2919715B2 - Imaging 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 image pickup apparatus such as a video camera and an electronic camera in which the dynamic range of an image pickup device is extended.

[0002]

2. Description of the Related Art Generally, the dynamic range of an image sensor is determined by the ratio between the noise level and the saturation level of an output signal.
When the dynamic range of the imaging target is wider than the dynamic range of the imaging device, a means for adjusting the exposure amount to the imaging device (for example, illumination intensity, aperture amount, exposure time, transmission amount of a filter, etc.) is provided. It is well known that an image with a dynamic range wider than the dynamic range of an image sensor can be captured by changing the exposure amount in multiple stages and capturing an image (Rangaraj).
M. Rangayyan, Richard Gordon: "Expanding the dynami
c range of x-rayvideodensitometry using ordinary i
mage digitizing devices ", Applied Optics, Vol.23, N
o.18, pp.3117-3120, 1984: JP 57-212448: JP 60
-52171: JP-A-60-52172: JP-A-62-108678: JP-A-1-99
036: JP-A-2-100564).

[0003]

In JP-A-62-108678, for example, the exposure amount of an image sensor is changed in two stages, and a first image captured with a first exposure amount is stored in a first image memory. Then, imaging is performed with the second exposure amount, and a wide dynamic range image is generated by combining the second image obtained by the imaging with the first image stored in the first image memory. .

However, in this case, if a video with a wide dynamic range is to be output as a video by applying the method to imaging of a moving object, the image data is written each time a wide dynamic range image is generated, and independent of the image data. It is necessary to provide a display image memory that can be read out at the timing of video display. For this reason, there has been a problem that the control of the display image memory is complicated and the device becomes large.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to be suitable for imaging of a moving object,
An object of the present invention is to save the memory capacity and reduce the size and simplification of the device.

[0006]

According to a first aspect of the present invention, there is provided an image pickup device for picking up an object, and outputting an image picked up with a first exposure amount in a first time interval. An image pickup control means for controlling the image pickup device to output image data picked up by the second exposure amount in the second time interval; and an image data picked up by the first exposure amount in the first time interval. In a first image memory for storing the image data at the address corresponding to the pixel, and in a second time interval, sequentially reading out image data taken with the second exposure amount from the image sensor, and reading the first exposure amount from the first image memory. Is read out, and the first lightness value of the image data obtained by imaging with the first exposure amount and the second lightness value of the image data obtained by imaging with the second exposure amount , Composite brightness over a wide dynamic range , A second image memory for storing the combined brightness value calculated by the calculation unit at an address corresponding to the pixel, and a combined brightness value stored in the second image memory in a first time interval. And select
In the second time section, there is provided a selecting means for selecting and outputting the combined brightness value calculated by the calculating means.

[0007]

[0008]

[0010] The invention according to claim 2 relates to an imaging apparatus for changing the exposure amount when taking an image in three or more stages and combining the brightness values in the three or more stages to obtain a combined brightness value . Immediately
That is, in an imaging device, an imaging device for imaging an object,
The exposure amount for the image element is changed to n steps or more (n ≧ 3).
And image the object, and from the first time section to the n-th time section
Let's take an image with the first to n-th exposures, respectively.
Imaging control means for controlling output of a captured image;
An image memory for storing image data corresponding to pixels;
Image data to the address corresponding to each pixel in the memory
Read the image data at that address before writing the data
The memory control means and the m-th (2 ≦ m ≦ n) time interval
Receiving data from the image memory and the image sensor.
The brightness value read from the image memory and the brightness value
Imaging with the m-th exposure in the m-th time interval to be output
From the m-th lightness value of the image data obtained by
Calculating means for calculating a combined lightness value up to the amount of light; and an image sensor
Output and the output of the arithmetic means are selected and stored in the image memory.
First selecting means for outputting, output of image memory and calculating means
Second selecting means for selecting and outputting one of the outputs of
In the time section of, the output of the image sensor is changed by the first selecting means.
Selecting and storing the output in an image memory;
To select the output of the image memory, and in the n-th time interval
Selects the output of the calculating means by the first selecting means and
The output is stored in the image memory, and the calculation
Select the output of the stage, and from the second time interval to the (n-1) th time
In the section, the output of the calculating means is selected by the first selecting means.
And store the output in the image memory and input the second selection means.
Control means for controlling so as to shut off the power and the output
And characterized in that:

According to a third aspect of the present invention, an image memory is provided in parallel.
A first image memory and a second image memory arranged in rows.
And the first image memory is a memory for storing an intermediate composite value.
And the second memory is used as a memory for storing the final combined brightness value.
It is composed. That is, an image sensor for imaging an object
And the exposure amount for the image sensor is made n stages or more (n ≧ 3)
The object is imaged by changing it, and from the first time interval to the n-th time
In the interval, the first exposure to the n-th exposure
Control means for controlling output of an image picked up by the camera
Are arranged in parallel to store image data corresponding to pixels.
A first image memory and a second image memory, and a first image memory
Image data to address corresponding to each pixel for memory
Read image data at that address prior to writing
The memory control means and the m-th (2 ≦ m ≦ n) time interval
Receiving data from the first image memory and the image sensor.
And the brightness value read from the first image memory and the imaging element
Image obtained with the m-th exposure output from the child
From the m-th lightness value of the data to the m-th exposure
Calculating means for calculating the degree value, output of the image sensor and calculating means
Output to the first image memory by selecting one of the outputs
Selecting means, output of the second image memory, and output of the calculating means
A second selecting means for selecting and outputting one of the first
In the section, the output of the image sensor is selected by the first selecting means.
The output is stored in the first image memory and the s-th (2 ≦ s ≦
In the time interval of (n-1), calculation is performed by the first selecting means.
Selecting the output of the means and storing the output in the first image memory
Then, in the n-th time section, calculation is performed by the first selecting means.
Selecting the output of the means and storing the output in the second image memory
In the p-th (1 ≦ p ≦ n−1) time section,
The output of the second image memory is selected by the second selection means,
In the section of n, the second selecting means sets the
Control means for controlling output selection.
Features.

According to the first aspect of the present invention, one control cycle for obtaining image data with a wide dynamic range is constituted by the first time section and the second time section following the first time section. In the image sensor, carrier accumulation is performed by the second exposure amount in the first time section,
In the second time interval, carrier accumulation with the first exposure amount is performed. Then, in the first time interval, image data captured from the image sensor at the first exposure time in the second time interval of the previous control cycle is read, and in the second time interval, the image data is read from the image sensor at the current time. In the first time section of the control cycle, the image data captured at the second exposure time is read out.

[0011] Then, in a first time section, image data captured with the first exposure amount is stored in the first image memory. In the second time interval, image data captured with the second exposure amount is sequentially read from the image sensor,
Image data captured at a first exposure amount is read from an image memory, and a first brightness value of image data obtained by imaging at a first exposure amount, and an image obtained by imaging at a second exposure amount From the second brightness value of the data, a combined brightness value in a wide dynamic range is calculated. The calculated combined brightness value is stored in the second image memory at an address corresponding to each pixel. Then, in the first time section, the combined brightness value stored in the second image memory is selected, and in the second time section, the combined brightness value calculated by the calculating means is selected and output. Thereby, the same combined lightness value is output in the second time section of the previous control cycle and the first time section of the main control cycle. As described above, according to the first aspect of the present invention, the image memory reads and writes the image data in synchronization with the first and second time intervals determined by the imaging control means. Therefore, it is not necessary to provide an image memory which is necessary, and the size and simplification of the device can be achieved. And the second
With the image memory and the selection means, it is possible to output the latest brightness value of the wide dynamic range always synthesized in the first time section and the second time section.

[0012]

[0013]

[0014]

[0015]

[0016]

[0017]

[0018]

[0019] invention the image memory according to claim 2, combined value of the intermediate obtained by combining the brightness value of the captured image up to that time interval is stored. The calculating means calculates a combined brightness value of the brightness value stored in the image memory and the brightness value newly read from the image sensor in the time section, and stores the calculated brightness value in the image memory. In the first time section, the final combined lightness value calculated in the previous control cycle is stored in the image memory, and this combined lightness value is output. Since the final combined brightness value in the control cycle is calculated, that value is output as the latest value. In other sections, since the content of the image memory is an intermediate composite brightness value, no image data is output. Claims in this way
The invention described in ( 2) can output a moving image with a simple configuration even when the exposure amount is changed in three or more steps.

The third image memory functions in the same manner as the second image memory. That is, the intermediate combined lightness value calculated by the calculating means is stored in the first image memory. On the other hand, the second image memory stores the final combined brightness value calculated by the calculation means. Until the calculating means calculates the final combined brightness value in the control cycle, the final combined brightness value in the previous control cycle stored in the second image memory is output. In the final time section, the result of calculating the final combined brightness value in the control cycle is output, so that the latest final combined brightness value is the output of the imaging device.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to specific embodiments. First Embodiment In FIG. 1, a synchronization signal S1 is generated from a synchronization signal generator 1. The synchronization signal S1 is a timing signal that is input to the CCD imaging device 4 and outputs data of each pixel. The synchronization signal is input to the field counter 2 and counted by the field counter 2. Since the field counter 2 is a 1-bit counter, every time one pulse of the synchronization signal is input, “0”,
"1", "0", "1", and so on. The output “1” of the field counter 2 is the first field, ie,
It means the first time section (section A). The output “0” of the field counter 2 means a second field, that is, a second time section (B section). Hereinafter, the signal output from the field counter 2 is referred to as a “field determination signal”.

The field discrimination signal S2 output from the field counter 2 is input to the exposure time control device 3,
The exposure time control device 3 outputs a signal representing the first exposure time T1 to the CCD image pickup device 4 with an electronic shutter when "0" of the field determination signal S2 is input, and receives "1" of the field determination signal S2 Second exposure time T2
Is output to the CCD image sensor 4. Thereby, the CCD image pickup device 4 with an electronic shutter captures an image of the object with the first exposure amount and the second exposure amount. The output of the image sensor 4 is connected to the A / D converter 5, and the output of the A / D converter 5 is connected to the input terminal of the image memory (first image memory) 6 and the second input terminal W 2 of the arithmetic unit 7. It is connected to the.
The output of the image memory 6 is the first input terminal W of the arithmetic unit 7.
1 connected.

The output of the arithmetic unit 7 is stored in an image memory (second
The input terminal of the image memory 8 and the second input terminal U2 of the selector 9 are connected. The output of the image memory 8 is connected to the first input terminal U1 of the selector 9. And
The output of the selector 9 is connected to the D / A converter 10.

Synchronous signal S output from synchronous signal generator 1
1 is an A / D converter 5, an image memory 6, an image memory 8,
The field discrimination signal S2 is input to the D / A converter 10, and is input to the image memory 6, the image memory 8, and the selector 9. When the field discrimination signal S2 is "0", the stored data is read from the image memory 6, and when the field discrimination signal S2 is "1", the output of the A / D converter 5 is sent to the image memory 6. It is memorized. When the field discrimination signal S2 is "1", the stored data is read from the image memory 8, and when the field discrimination signal S2 is "0", the output of the arithmetic unit 7 is stored in the image memory 8. . Further, when the field discrimination signal S2 is "0",
The selector 9 outputs the signal of the second input terminal U2, that is, the output signal of the arithmetic unit 7, and when the field discrimination signal S2 is "1", the selector 9 outputs the signal of the first input terminal U1, that is, the image memory 8 Output signal. In addition, data for each pixel is written, read, and transferred in synchronization with the synchronization signal S1.

The arithmetic unit 7 calculates a composite value of the value input from the first input terminal W1 and the value input from the second input terminal W2, and outputs the result to the image memory 8 and the second input terminal U2 of the selector 9. It is a device to do. The arithmetic unit 7 is configured as shown in FIG. The value D2 input from the second input terminal W2 is converted by the function generators 22 and 23 into a predetermined function value. Also, the value D input from the first input terminal W1
1 is a multiplier 2 multiplied by a predetermined coefficient by a multiplier 21
Enter 4 In the multiplier 24, the output of the function generator 22 and the output of the multiplier 21 are multiplied, and the result is output to the adder 26. On the other hand, the output of the function generator 23 and the value D2 input from the second input terminal W2 are input to a multiplier 25, multiplied by the values, and the result is input to an adder 26. The adder 26 includes a multiplier 24 and a multiplier 25
, And the result D0 is output from the output terminal W0.

It is assumed that an image of the object to be imaged is formed on the light receiving surface of the image sensor 4 by an appropriate optical system.
It is assumed that the output of the image sensor 4 maintains linearity when the incident light intensity is equal to or lower than the saturation level of the output of the image sensor. In the case of the present embodiment, the exposure amount can be changed in two stages depending on the shutter speed of the electronic shutter of the image sensor. That is, the exposure amount can be reduced as the shutter speed is reduced. As a method of changing the exposure amount, instead of changing the shutter speed of the electronic shutter of the CCD imaging device 4 as described above, for example, the amount of light incident on the imaging device can be electrically controlled using a liquid crystal or the like. A variable transmittance filter or an electronic shutter may be provided in front of the light receiving surface of the image sensor.

The arithmetic unit 7 changes the lightness value D of the pixel corresponding to each of the two images picked up by the image pickup device 4 while changing the exposure amount.
When 1 and D2 are given to the first input terminal W1 and the second input terminal W2, the brightness value with the expanded dynamic range is output from the output terminal W0.

The image memory 6 is a bitmap type image memory for storing a brightness value D2 of an image captured with the second exposure amount. The selector 9 selects one of the output of the image memory 8 and the output of the arithmetic unit 7, and selects the D / A converter 1
0 is output. The D / A converter 10 converts data output from the selector 9 into an analog signal in pixel units and outputs the analog signal as a video signal.

The multiplier 21 of the arithmetic unit 7 converts the first brightness value D1 given to the first input terminal W1 of the arithmetic unit 7 into the second brightness value D2 given to the second input terminal W2 of the arithmetic unit 7. Is a device for multiplying the first lightness value D1 by the ratio T2 / T1 of the exposure amount of the second lightness value D2 to the first lightness value D1 in order to convert the lightness value into a lightness value corresponding to the sensitivity.

The function generators 22 and 23 of the arithmetic unit 7
Generates functions f and g, respectively. Here, the function f is 0 when the second brightness value D2 is equal to or less than the first predetermined value,
The function is a function that gradually changes from 0 to 1 from the first predetermined value to the second predetermined value. The function g is 1 when the second lightness value D2 is equal to or less than the first predetermined value, and gradually changes from 1 to 0 from the first predetermined value to the second predetermined value.

Examples of the functions f and g are shown in FIGS. 4A and 4B, respectively. The functions f and g are, as will be described later, the first brightness value D1 and the second brightness value D1 of the first image, respectively.
This determines the ratio of the second brightness value D2 of the image to be used. Therefore, f (D2) + g (D2)
Is preferably a unit amount for any value of D2. Therefore, in the examples shown in FIGS. 4A and 4B,
g (D2)

[0032]

It is assumed that g (D2) = 1-f (D2). Note that f (D2) + g (D2) is an arbitrary D
Even if the value of 2 does not become a unit amount but slightly changes, this does not usually greatly degrade the performance of the present apparatus.

The multiplier 24 of the arithmetic unit 7 multiplies the output value of the multiplier 21 by the output value of the function generator 22 and outputs the result.
The multiplier 25 multiplies the second brightness value D2 by the output value of the function generator 23 and outputs the result. The adder 26 adds the outputs of the multiplier 24 and the multiplier 25 and outputs the result.
Output.

Therefore, for the first lightness value D1 and the second lightness value D2 which are two inputs of the arithmetic unit 7, the arithmetic unit 7 shown in FIG.

D0 = (D1 × T2 / T1) × f (D2) + D2 × g (D2)

Is calculated to output a composite lightness value D0. In this way, the composite brightness value D0 in the wide dynamic range image is calculated from the first brightness value D1 of the first image and the second brightness value D2 of the second image.

The operation of the thus configured apparatus of this embodiment will be described below with reference to the timing chart shown in FIG. The k-th control cycle includes a first time section A _k where the field discrimination signal S2 is “1” and a second time section B _k where the field discrimination signal S2 is “0”. The exposure period precedes the pixel data readout period from the image sensor 4 by one time section. Therefore, in the second time section B _k-1 of the k-1th control cycle, the image sensor 4 is exposed for the first exposure time T1, and the image data resulting from the exposure is in the first time section B of the _k- th control cycle. At _Ak , the data is sequentially read for each pixel. Similarly, in the first time section A _k of the k-th control cycle, the image sensor 4 is exposed for the second exposure time T2, and image data resulting from the exposure is obtained in the second time section B _k of the k-th control cycle. , Are sequentially read out for each pixel.

In the first time section A _k of the k-th control cycle
In the first time section A _{k of} the k-th control cycle, the field discrimination signal S2 is “1”, the image memory 6 is set to the writing mode, and the output of the A / D converter 5 is the first. Lightness value D
_{1, k, 1,} D _{1, k, 2,} ... _, D _{1, k, n} are sequentially stored at addresses corresponding to the pixels. The selector 9 is set to a mode in which the first input terminal U1 is connected to the output terminal. As a result, the combined brightness values D _{0, k-1,1,} D _{0, k−1} stored in the image memory 8 in the second time interval B _k−1 of the k−1 control cycle. _{, 2,} ... _, D _{0, k-1, n} are sequentially output to the D / A converter 10. Then, the signal is converted into an analog signal in pixel units by the D / A converter 10, and is sequentially output as a video signal of the (k-1) th control cycle.
As shown in FIG. 2, the output timing of the corresponding pixel from the selector 9 is delayed by the processing time as compared with the read timing from the image sensor 4, so that the video signal is synchronized with a delay of a fixed time. Become.

In the second time interval B _k of the k-th control cycle
In the second time section B _{k of} the k-th control cycle, the field determination signal S2 is “0”, and the image memory 6 is set to the reading mode. Accordingly, the first lightness value D stored in the image memory 6 in the first time interval A _k of the k control cycle
_{1, k, 1,} D _{1, k, 2,} ... _, D _{1, k, n} are sequentially output to the first input terminal of the arithmetic unit 7. In the second time interval B _k , the arithmetic unit 7 outputs the second brightness values D _{2, k, 1,} D _{2, k, 2,} ... _, D output from the A / D converter 5. _{2, k and n} are sequentially input to the second input terminal W2 of the arithmetic unit 7 for each pixel.
Then, the arithmetic brightness value D _{0, k, 1,} D _{0, k, 2,}
.. _, D _{0, k, n} are calculated, and the combined brightness values D _{0, k, 1,} D
_{0, k, 2,} ... _, D _{0, k, n} are sequentially stored in the image memory 8 for each pixel. At the same time, the selector 9 is set to a mode in which the second input terminal U2 is connected to the output terminal. Thus, the combined brightness value D calculated by the arithmetic unit 7
_{0, k, 1,} D _{0, k, 2,} ... _, D _{0, k, n} are output to the D / A converter 10. Then, those values are D / A converted, and the k-th
It is output as a video signal of the control cycle. Incidentally, as shown in FIG. 2, compared with the readout timing from the image sensor 4,
Since the output timing of the corresponding pixel from the selector 9 is delayed by the processing time, the video signal is synchronized with a delay of a fixed time.

Thereafter, the operation in the next control cycle is similarly executed. The electronic shutter function of a normal CCD image pickup device controls the exposure amount by discharging accumulated charges until a certain time after the start of a frame, and then accumulating the charges until a certain time. Therefore, as shown in the present embodiment, the two types of exposure times T1 and T2 for performing imaging are T1 <
By setting the relationship of T2, it is possible to reduce the blur of a wide dynamic range image synthesized from the first brightness value D1 of the first image and the second brightness value D2 of the second image. That is, by making T1 smaller than T2, as shown in FIG.
, And the carrier accumulation time by the exposure time T2 can be made closer, so that image blurring is reduced. On the other hand, if T1> T2, as shown in FIG. 5B, the carrier accumulation time based on the exposure time T1 and the carrier accumulation time based on the exposure time T2 are separated, and the image blur becomes large.

Second Embodiment As a second embodiment, the arithmetic unit 7 in the embodiment shown in FIG. 1 is replaced with a lookup table 3 as shown in FIG.
It can be replaced with 1. That is, for a combination of all possible values of the first lightness value D1 and the second lightness value D2 input to the arithmetic unit 7, the combined lightness value D0 is calculated in advance to create a table. By doing so, the arithmetic unit 7 can be replaced with a look-up table. In this case, there is an advantage that the configuration is simplified.

When the output value d of the image sensor 4 is non-linear with respect to the intensity of incident light, a conversion h (d) for linearly converting the output value d can be included in this table. For example, the arithmetic unit 7

When calculating D0 = (D1 × T2 / T1) × f (D2) + D2 × g (D2),

D0 = (h (d1) × T2 / T1) × f (h (d2)) + h (d2) × g (h (d2)) is calculated in advance to create a table.

Here, d1 and d2 are the first lightness value and the second lightness value output from the image sensor 4, respectively.

[0043] As a third embodiment the third embodiment, as shown in FIG. 7, may be analog data instead of the image memory 6 of the first embodiment is a configuration using an image memory 41 which can store. in this case,
In the image memory 41, the first analog image data captured at the first exposure time T1 is stored in a field discrimination signal S2.
_Are stored in the first time section _Ak of “1”. Then, the first analog image data thereof stored, the field determination signal S2 are read out in the second time interval B _k of "0", the first analog image data read is A / D converter 43, is converted into a digital value.
The value is input to the first input terminal W1 of the arithmetic unit 7. At the same time, in the second time interval B _k ,
The second analog image data imaged at the second exposure time T2 is read out from the A / D converter 42.
Is converted into a digital value, and is input to the second input terminal W2 of the arithmetic unit 7.

As a result, in the same manner as in the first embodiment, the arithmetic unit 7 performs a composite operation of the brightness values. The composite brightness value D0, which is the calculation result, is stored in the image memory 8 and is input to the second input terminal U2 of the selector 9. The selector 9 outputs the combined brightness value D0 stored in the image memory 8 in the first time section A _k , and outputs the calculation result of the calculation device 7 in the second time section B _k , as in the first embodiment. Is output. In this embodiment, as shown in FIG. 7, since the image memory 41 can be provided on the same chip as the imaging device 4 using a CCD or the like, there is an advantage that the apparatus can be downsized when the image size is large. There is.

Fourth Embodiment A fourth embodiment can be configured as shown in FIG. The apparatus according to the present embodiment is an imaging apparatus configured so that the dynamic range expansion rate can be changed by a dynamic range expansion rate signal. 8, reference numeral 51 denotes a dynamic range expansion ratio signal, 52 denotes a dynamic range expansion ratio control device, 53 denotes an arithmetic unit, and the other components are the same as those shown in FIG.

The arithmetic unit 53 is configured as shown in FIG. In FIG. 9, 21 'is a multiplier, 55 is a magnification control signal, and the others are the same as those in the configuration of FIG. FIG.
When the dynamic range enlargement ratio is designated by the dynamic range enlargement ratio signal 51 in the apparatus of FIG. 1, the signal is transmitted to the control device 8 by the signal 54, and the ratio of the first exposure time T1 to the second exposure time T2 is determined. Is changed to the value of At the same time, the value of the coefficient T2 / T1 which is transmitted to the arithmetic unit 53 by the signal 55 and multiplied by the multiplier 21 'is also changed. It is also possible to replace the arithmetic unit in FIG. 9 with a look-up table or the like in the same manner as in the case of the second embodiment in FIG.

Fifth Embodiment In FIG. 10, a synchronizing signal generator 1, a field counter 2, an exposure time controller 3, and an image sensor 4 are the same as those shown in FIG.
This is the same as the device of the embodiment. In this embodiment, one image memory 62 is used instead of the image memories 6 and 8 of the first embodiment, and a selector 61 is added.

In the present embodiment, the A / D converter 5
Is connected to the second input terminal W2 of the arithmetic unit 7, and the output of the arithmetic unit 7 is connected to the second input terminal V2 of the selector 61.
2 and the second input terminal U2 of the selector 9. The output of the selector 61 is connected to the input terminal of the image memory 62, and the output of the image memory 62 is connected to the first input terminal W1 of the arithmetic unit 7 and the first input terminal U of the selector 9.
1 connected.

The synchronizing signal S 1 output from the synchronizing signal generator 1 is input to the image sensor 4, A / D converter 5, image memory 62 and D / A converter 10, and is output from the field counter 2. The frame discrimination signal S2 is supplied to the selector 61,
The image is input to the image memory 62 and the selector 9.

The arithmetic unit 7 calculates a composite value of the value input from the first input terminal W1 and the value input from the second input terminal W2, and calculates the second input terminal V2 of the selector 61 and the second value of the selector 9. This is a device that outputs to the input terminal U2. The arithmetic unit 7 has the same configuration as that of the first embodiment shown in FIG.

The image memory 62 is a bit map type image memory for holding an image captured with the first exposure amount or a wide dynamic range image output from the arithmetic unit 7, and is used for writing an address corresponding to each pixel. It is configured to read the address beforehand.

FIG. 12 shows a configuration example of the image memory 62.
In the figure, 610 is a memory, 611 is an address translator,
612 is a register. The selector 61 selects one of the output of the A / D converter 5 and the output of the arithmetic unit 7 and outputs it to the image memory 62. Selector 9
Is to select and output one of the output of the image memory 62 and the output of the arithmetic unit 7. D / A converter 10
Converts the data output from the selector 9 into an analog signal in pixel units and outputs it as a video signal.

Referring to the timing chart shown in FIG. 11, the apparatus of this embodiment configured as described above will be described.
The operation will be described below. As in the first embodiment, the k-th control cycle includes a first time section A _k and a second time section B _k . The exposure time and reading of the image data from the image sensor 4 are the same as in the first embodiment.

In the first time section A _k of the k-th control cycle
When the field discrimination signal S2 of the k-th control cycle is “1”, the first
In the time section A _k , the selector 61 sets the first input terminal V1
Is set to the mode to connect to the output terminal. As a result, the first brightness value D1 output from the image sensor 4 is sequentially stored in the image memory 62 for each pixel. The selector 9 is set to a mode in which the first input terminal U1 is connected to the output terminal. As a result, the combined brightness value D0 that has been combined and stored in the image memory 62 in the (k-1) th control cycle is output to the D / A converter 10.

Accordingly, the composite brightness values D _{0, k-1,1,} D _{0, k-1,2,} ... Of each pixel calculated in the (k-1) th control cycle from the address corresponding to each pixel in the image memory 62 _. …… _, D
_{0, k-1, and n} are sequentially read. Then, the value is transferred to the D / A converter 10 via the selector 9, converted into an analog signal for each pixel, and sequentially output as a video signal.

At the timing delayed by at least one pixel read time from the read timing of each pixel from the image memory 62, the first data read from the image sensor 4 and converted into a digital value by the A / D converter 5 is read. Lightness value D
_{1, k, 1,} D _{1, k, 2,} ... _, D _{1, k, n} are stored in the image memory 62 via the selector 61 for each address corresponding to each pixel. In the present embodiment, as shown in FIG. 11, at the same timing when the first brightness value D _{1, k, i} of the pixel i is output from the A / D converter 5, the image memory 62 corresponding to the pixel i is output.
, The combined brightness value D _{0, k-1, i} is read from the address
First brightness value D of pixel i output from D converter 5
_{1, k, i} are written to the address corresponding to the pixel i of the image memory 62 with a predetermined delay.

FIG. 13 shows the operation of the image memory 62 shown in FIG. 12 at this time. The register 612 has a memory 610
The address corresponding to the image origin is set. The synchronizing signal S1 generated from the synchronizing signal generator 1 is referred to an address corresponding to the image origin stored in the register 612 by the address converter 611 to the memory 610.
Is converted to the real address. For example, suppose that the content of the address of the memory 610 corresponding to the pixel 6 in FIG. 13 has been read. At this time, since the value of the pixel 4 delayed by a predetermined time is input to the image memory 62, it is stored in the same address of the memory 610 that has just been read.
After the processing in this time section is performed in this manner, the address stored in the register 12 is updated to a new origin address in response to the change in the field determination signal S2.

In the case of the present embodiment, in the image memory 62, the timing of reading and writing the address corresponding to each pixel is the same in the first time section A _k and the second time section B _k. It is. This has the advantage that control of the image memory and its peripheral circuits is simplified.

During the reading of the first brightness value D1 of the first image data from the image pickup device 4 in the first time section _Ak , the image pickup device 4 uses the second exposure time T1.
2, the object is imaged.

In the second time section B _k of the k-th control cycle
In the second time section B _{k of} the k-th control cycle, the selector 61
Is set to a mode in which the second input terminal V2 is connected to the output terminal. As a result, the composite brightness value D0 calculated by the calculation device 7 is sequentially stored in the image memory 62 for each pixel. The selector 9 is set to a mode in which the second input terminal U2 is connected to the output terminal. Thus, the composite brightness value D0 calculated by the calculation device 7 is output to the D / A converter 10.

In the second time section B _k , the second lightness value D _{2, k, 1,} D _{2, k} read from the image pickup device 4 and converted into a digital value by the A / D converter 5 _{, 2,} …… _, D
_{2, k and n} are sequentially input to the second input terminal W2 of the arithmetic unit 7 for each pixel. On the other hand, the image memory 62 stores the first time section A _k
First lightness value D _{1, k} stored _{during, 1, D 1, k,} 2, ......,
D1 _{, k, n} are read out in synchronization with the input of the second brightness value for each pixel, and those values are sequentially input to the first input terminal W1 of the arithmetic unit 7.

In the arithmetic unit 7, the first lightness values D1 _{, k, 1,} D1 _{, k, 2,} ... _, D1 _{, k, n} input from the first input terminal W1.
And the second brightness value D input from the second input terminal W2
_{2, k, 1,} D _{2, k, 2,} ... _, D _{2, k, n
0, k, 1, D 0} , k, 2, ......, D 0, k, n is computed, these values are input from the output terminal W0 to the second input terminal U2 of the selector 9. These values are sent to D / A via selector 9
The signal is converted into an analog signal in pixel units by the converter 10,
These are sequentially output as video signals.

At the same time, the combined brightness values D _{0, k, 1,} D
_{0, k, 2, ......,} D 0, k, n is input to the second input terminal V2 of the selector 61, the values via the selector 61,
It is stored at a predetermined address corresponding to each pixel of the image memory 62. Note that the storage in the image memory 62 is adjusted so as to be performed after the reading of the content of the same address is completed, as described above.

In the second time section B _k , the imaging of the object by the first exposure time T 1 is performed by the imaging device 4. The image obtained by the imaging is read out from the imaging element 4 in the first time section A _{k + 1} of the next control cycle k + 1.

Thereafter, the operation in the next control cycle is similarly executed.

[0066] When freeze the image for the purpose of performing the image processing, when the timing signal S3 freeze at any point is given to the synchronization signal generating device 1, corresponds to the end of the second time interval B _k Pause operation at the timing of As a result, the image with the combined lightness value D0 in the wide dynamic range is always frozen in the image memory 62.

Sixth embodiment . In the fifth embodiment, the image memory 62 of FIG.
May be configured as shown in FIG. In FIG. 14, 631
And 632 are selectors, and 633 and 634 are image memories. The selector 631 alternately selects the image memory 633 and the image memory 634 for each frame.
The data input to the selector 631 is written to a predetermined address of the selected image memory. The selector 632 includes an image memory 633 and an image memory 63.
4 are alternately selected for each frame. However, the selector 632 selects the image memory not selected by the selector 631. Data read from a predetermined address of the selected image memory is output to the output of the selector 632.

FIG. 15 shows the operation of the image memory shown in FIG. In the first time section A _k , data is written to the image memory 634 with the first brightness value D1 captured at the first exposure time, and the combined brightness value calculated and stored in the previous control cycle k-1 is stored. D0 is read from the image memory 633. In the second time interval B _k , the first lightness value D1 is read from the image memory 634, and the first lightness value D1 is read.
1 and synthesized brightness value by the arithmetical unit 7 from the second lightness value D2 Metropolitan output from the image pickup device 4 in the second time interval B _k D0
Is calculated, and the combined brightness value D0 is written to the image memory 633.

Therefore, in each image memory 633, the contents are read in the preceding frame, and data is written in the subsequent frame. Using this configuration has an advantage that the image memory 62 can be configured even when a memory element having a relatively low access speed is used.

Seventh Embodiment This embodiment differs from the fifth embodiment shown in FIG. 10 in that three or more types of exposure amounts are changed to obtain a first lightness value D1, a second lightness value D2, and a third lightness value. The present invention relates to an apparatus that obtains a value D3 and calculates a composite lightness value D0 from those lightness values. As the number of changes in the exposure amount is increased, the dynamic range can be further expanded, and an image with higher density value accuracy can be obtained.

In FIG. 16, 1 is a video synchronizing signal generator, 81 is a field counter, 82 is an exposure time controller, 4 is an image sensor, 5 is an A / D converter, 83 is an arithmetic unit, 62 is an image memory, 9 is a selector and 10 is a D / A converter. Among them, the video synchronization signal generator 1, the image sensor 4, the A / D converter 5, the image memory 62, the selector 9, and the D / A converter 10 are substantially the same as those in the fifth embodiment of FIG. Has functions.

The field counter 81 uses the signal from the video synchronization signal generator 1 to count the number of time sections in the control cycle, that is, the number of fields. When the counter value j exceeds the set value _jmax , the counter value is reset to zero. The exposure time control device 82 calculates the value j of the field discrimination signal S2 output from the field counter 81.
, The image sensor 4 is exposed for an exposure time Tj + 1. Except for the last time section, the field discrimination signal S2
Is equal to the section number m of the m-th time section. In the section number m _max of the last time section, the field discrimination signal S2
Is 0.

The first input terminal W1 of the arithmetic unit 83 is connected to the output of the image memory 62, and the second input terminal W2 of the arithmetic unit 83 is connected to the output of the A / D converter 5. The arithmetic unit 83 is basically the same as the arithmetic unit 7 of the fifth embodiment shown in FIG. 10, but changes the arithmetic method according to the value j of the field discrimination signal S2 (the coefficient of the equation 2). And a function).

[0074] That is, the first time interval A _k value j of the field discrimination signal S2 is "1", and outputs the inputted data from the second input terminal W2 of the arithmetic unit 83. When the value j of the field discrimination signal S2 is a value other than 1, that is, in a time section after the second time section, that is, in a second time section B _k , a third time section C _k (FIG. 1
In FIG. 7, three time sections are shown, but the number of time sections, that is, the number of types of exposure time is arbitrary. )
The arithmetic unit 83 executes an arithmetic operation for synthesizing the brightness value read from the image sensor in the current time section with the combined value up to the past time section. Therefore, in the m-th time section, T1 to T
A combining operation is performed using the first lightness value D1 to the m-th lightness value Dm obtained by imaging at an exposure time of m. Note that a composite value using the first lightness value D1 to the (m-1) th lightness value Dm-1 is stored in the image memory 62. And
In the last time section m _max (j = 0), the first lightness values D1 to m _max −1 stored in the image memory 62
And the combined value to the brightness value Dm _max -1 of lightness value D of the m _max read from the imaging device 4 in this time interval
and a m _max, brightness value D of the first lightness value D1~ first m _max
The composite value D0 up to m _max is calculated.

The arithmetic unit 83 calculates the first time interval A _k
Then, the data input to the second input terminal W2, that is, A
Since the output of the / D converter 5 is output as it is, the arithmetic unit 83 also has the function of the selector 61 shown in FIG.

In the final time section m _max in which the value of the field discrimination signal S 2 is “0”, the selector 9 outputs the input data of the second input terminal U 2, that is, the output of the arithmetic unit 83 to D /
Output to the A converter 10. In the first time section A _k in which the value of the field determination signal is “1”, the input data of the first input terminal U1, that is, the output of the image memory 62 is D / D.
Output to the A converter 10. The selector 9 does not output a value in a time section other than the first time section and the last time section.

The operation of the thus configured apparatus of the present embodiment will be described below. If j _max is 1, then
That is, when there are two time sections, the same operation as in the fifth embodiment shown in FIG. 10 is performed. The operation of the present apparatus when j _max is 2 will be described with reference to the timing chart of FIG.

In the first time section A _k of the k-th control cycle
When the field discrimination signal S2 of the k-th control cycle is “1”, the first
In the time section A _k , the arithmetic unit 83 outputs the second input terminal W2
Is selected, and the input data is stored in the image memory 62.
Output to Therefore, the first brightness value D1 is stored in the image memory 6
2 is stored. The selector 9 is set to a mode in which the first input terminal U1 is connected to the output terminal. This allows
The combined brightness value D0 that has been combined and stored in the image memory 62 in the (k-1) th control cycle is stored in the D / A converter 10
Is output to

Therefore, the composite brightness values D _{0, k-1,1,} D _{0, k-1,2, and} D of each pixel calculated in the (k-1) th control cycle from the address corresponding to each pixel in the image memory 62 _. …… _, D
_{0, k-1, and n} are sequentially read. Then, those values are transferred to the D / A converter 10 via the selector 9, converted into analog signals in pixel units, and sequentially output as video signals. As in the fifth embodiment, the timing is adjusted so that reading of data from the image memory 62 is performed prior to writing.

Therefore, in this time interval, the image memory 6
2, a first lightness value D _{1, k, 1,} D _{1, k, 2,} read out from the image sensor 4 and converted into a digital value by the A / D converter 5
.. _, D _{1, k, n} are transferred to the image memory 6 via the arithmetic unit 83.
2 is stored for each address corresponding to each pixel.

In the first time interval A _k , while the first brightness value D1 of the first image data is being read from the image sensor 4, the second exposure time T 1 is set by the image sensor 4.
2, the object is imaged.

In the second time section B _k of the k-th control cycle
In the second time interval B _{k of} the k-th control cycle, the arithmetic unit 83
Are sequentially stored in the image memory 62 for each pixel. Further, the selector 9 is set to a cutoff mode in which input and output are separated.

In the second time section B _k , the second brightness values D _{2, k, 1,} D _{2, k} read from the image sensor 4 and converted into digital values by the A / D converter 5 _{, 2,} …… _, D
_{2, k, n} are sequentially input to the second input terminal W2 of the arithmetic unit 83 for each pixel.
To enter. On the other hand, the first time interval A
first lightness value stored during the _{k D 1, k, 1,} D 1, k, 2, ......
_, D _{1, k, n} are read out in synchronism with the input of the second brightness value for each pixel, and those values are stored in the first input terminal W of the arithmetic unit 83.
1 is sequentially input.

In the arithmetic unit 83, the first brightness values D _{1, k, 1,} D _{1, k, 2,} ... _, D input from the first input terminal W1
_{1, k, n} and a second brightness value D _{2, k} inputted from the second input terminal _{W2, 1, D 2, k} , 2, ......, D 2, k, intermediate from _n combined value value D
_{T, k, 1, DT, k, 2,} ... _{, DT, k, n} are calculated, and their values are output from the output terminal W0 to the image memory 62, and correspond to each pixel of the image memory 62. Is stored at the specified address. Note that the storage in the image memory 62 is adjusted so as to be performed after the reading of the content of the same address is completed, as described above.

In the second time section B _k , the imaging of the object by the third exposure time T 3 is performed by the imaging device 4. The image obtained by the imaging is read out from the imaging element 4 in the next time section.

Intermediate time section of the k-th control cycle The operation is the same as the operation in the second time section described above.

The third time section C _{k of} the k-th control cycle (final
Mode time interval) selector 9 selects the second input terminal U2, i.e., the output data of the arithmetic unit 83 except that it is set in the mode to be outputted to the D / A converter 10, a second time interval Is the same as the control of

The above processing is repeatedly executed. When the image is frozen for the purpose of performing image processing or the like, the operation is temporarily stopped at a timing corresponding to the end of the field where the counter value is 0. As a result, a wide dynamic range image can be always frozen in the image memory 62.

Eighth Embodiment The apparatus of the seventh embodiment can be operated as follows. That is, normally, the operation where the counter value is 0 and 1 is repeated with j _{max of the} field counter 81 set to 1, and when the timing signal is given, j _max is set to 2 and the operation when the field counter value is 0, 1 and 2 is performed. To do. While _jmax is 1, the present apparatus operates substantially the same as the apparatus of the fifth embodiment shown in FIG. That is, a video signal of a composite image can be output in two time intervals.

On the other hand, if j _max is set to 2, images of two types of exposure amounts T1 and T2 were synthesized before that, whereas three types of exposure amounts T1, T2 and T3 were used.
Images are synthesized. When j _max is set to 2, no video signal is output in the second time interval B _k in FIG. 17, but a more accurate image is obtained in the image memory 62. Therefore, by operating as described above, a video signal is normally output in each time section (field), and when a timing signal is given, the type of exposure can be increased to obtain an image synthesized with high accuracy. Here, as an example, the case where j _max is set to 2 is shown, but it is obvious that j _max can be set to a value of 2 or more.

Ninth Embodiment A ninth embodiment shown in FIG. 18 is different from the seventh embodiment in FIG. 16 in that two image memories 101 and 102 arranged in parallel are used instead of the image memory 62. is there. Seventh
In the embodiment, when the value of j _max is set to 2 or more, the video signal is not output unless the value of the field determination signal is “0” or “1”, that is, other than the first time section or the last time section. . However, in the present embodiment, a video signal of the composite brightness value is always output.

The image memory 101 is a memory for holding a wide dynamic range image obtained by synthesis, that is, a final synthesized brightness value D0. The image memory 102 has the same function as the image memory 62 in the seventh embodiment, except that the image memory 102 does not output to the selector 9. That is, the image memory 1
02 is a memory for storing the first lightness value D1 and the intermediate combined lightness value DT up to that time interval. Synchronous signal generator 1, field counter 81, exposure time controller 8
2. The imaging device 4, the A / D converter 5, and the arithmetic device 83 are the seventh
It works in the same way as the device of the embodiment. As shown in FIG. 19, the image memory 101 stores the final composite brightness value D0 calculated by the arithmetic unit 83 in the field discrimination signal S2 of “0”, that is, in the last time section. Also, the image memory 1
01 indicates that the field discrimination signal S2 is other than “0”, that is,
In the period other than the last time section, the final combined lightness value D0 in the previous control cycle stored therein is output to the selector 9. The selector 9 outputs the final combined lightness value D0 of the previous control cycle stored in the image memory 101 to the D / A converter 10 except for the last time section, and calculates in this control cycle in the last time section. The final combined brightness value D0 calculated by the device 83 is output to the D / A converter 10.
With this operation, a video signal having the composite brightness value D0 can be always obtained.

[0093]

In the last time section (the field discrimination signal S2 is "0"), the arithmetic unit 83 sets the exposure amounts T1 to Tj _max +1.
All brightness values captured at an exposure dose of up to D1 through Dj _max +
The final combined brightness value D0 obtained by combining 1 is output. This value is output to the D / A converter 10 via the selector 9 in the last time interval, and is also stored in the image memory 101.

Other than the last time section (field discrimination signal S
2 is other than “0”), the arithmetic unit 83
Then, a combined brightness value of the intermediate combined brightness value DT stored up to that point and the brightness value output from the image sensor 4 in this time interval is calculated. Then, the updated intermediate combined brightness is stored in the image memory 102.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a configuration of an imaging apparatus according to a first specific example of the present invention.

FIG. 2 is a timing chart for explaining the operation of the first embodiment.

FIG. 3 is a block diagram showing a detailed configuration of an arithmetic unit of the first embodiment.

FIG. 4 is a characteristic diagram showing characteristics of a function of a function generator of the arithmetic device.

FIG. 5 is a timing chart showing completion of exposure time and lightness value synthesis timing.

FIG. 6 is a block diagram showing a configuration of an arithmetic unit in the second embodiment.

FIG. 7 is a block diagram illustrating a configuration of an imaging apparatus according to a third embodiment.

FIG. 8 is a block diagram illustrating a configuration of an imaging apparatus according to a fourth embodiment.

FIG. 9 is a block diagram showing a configuration of an arithmetic unit in the device of the fourth embodiment.

FIG. 10 is a block diagram illustrating a configuration of an imaging apparatus according to a fifth embodiment.

FIG. 11 is a timing chart illustrating the operation of the fifth embodiment device.

FIG. 12 is a block diagram showing a configuration of an image memory in the fifth embodiment.

FIG. 13 is an explanatory diagram for explaining reading and writing of data from an image memory in the fifth embodiment.

FIG. 14 is a block diagram showing a configuration of an image memory in the sixth embodiment device.

FIG. 15 is a timing chart illustrating the operation of the sixth embodiment device.

FIG. 16 is a block diagram illustrating a configuration of an imaging apparatus according to a seventh embodiment.

FIG. 17 is a timing chart for explaining the operation of the seventh embodiment.

FIG. 18 is a block diagram illustrating a configuration of an imaging apparatus according to a ninth embodiment.

FIG. 19 is a timing chart illustrating the operation of the ninth embodiment device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 4 ... Image sensor 6 ... Image memory 7 ... Calculator 8 ... Image memory 9 ... Selector 41 ... Image memory

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-5-7336 (JP, A) JP-A-2-174470 (JP, A) JP-A-2-65384 (JP, A) (58) Field (Int.Cl. ⁶ , DB name) H04N 5/235-5/243 H04N 5/335

Claims (3)

(57) [Claims] 1. An image pickup apparatus for picking up an object with different exposure amounts and combining the obtained image data to obtain an image with a wide dynamic range, comprising: an image pickup element for picking up an object; The object is imaged by changing the amount in two stages, an image captured with a first exposure amount is output in a first time interval, and image data captured with a second exposure amount is output in a second time period. Imaging control means for controlling output from an imaging element; and a first image memory for storing the image data imaged at the first exposure amount in an address corresponding to the pixel in the first time interval; In the second time interval, the image data imaged at the second exposure amount is sequentially read from the image sensor, and the image data imaged at the first exposure amount from the first image memory is read. The image data is read out, obtained by imaging with the first exposure value, the first brightness value of the image data obtained by imaging with the first exposure amount, and imaging with the second exposure amount in the second time interval output from the image sensor. Calculating means for calculating a combined brightness value in a wide dynamic range from the second brightness value of the image data obtained, and a second image memory for storing the combined brightness value calculated by the calculating means at an address corresponding to the pixel Selecting the combined brightness value stored in the second image memory in the first time section, and selecting the combined brightness value calculated by the calculation means in the second time section And an output selecting means. 2. An image pickup apparatus for picking up an object with different exposure amounts, and combining the obtained image data to obtain an image with a wide dynamic range. The object is imaged by changing the amount to at least n steps (n ≧ 3). During the first to n-th time intervals, the images captured at the first to n-th exposure amounts are respectively obtained. Imaging control means for controlling output of the image data; an image memory for storing the image data corresponding to each pixel; and an address of the image memory prior to writing the image data to an address corresponding to each pixel. Memory control means for reading out the image data, and for the m-th (2 ≦ m ≦ n) time interval, receiving the data from the image memory and the image sensor and reading the brightness read from the image memory And calculating the combined brightness value up to the m-th exposure amount from the m-th brightness value of the image data obtained by imaging with the m-th exposure amount in the m-th time section output from the image sensor. Computing means; first selecting means for selecting one of the output of the image sensor and the output of the computing means and outputting to the image memory; selecting one of the output of the image memory and the output of the computing means; A second selecting means for outputting, and in a first time section, an output of the image pickup device is selected by the first selecting means, the output is stored in the image memory, and an output of the image memory is stored by the second selecting means. Selecting an output, in an n-th time section, selecting the output of the calculating means by the first selecting means, storing the output in the image memory, and selecting the output of the calculating means by the second selecting means And from the second time interval In the (n-1) -th time section, the output of the calculating means is selected by the first selecting means, the output is stored in the image memory, and the input and output of the second selecting means are cut off. An imaging apparatus comprising: a control unit configured to perform control as described above. 3. An image obtained by imaging an object with different exposure amounts
By combining image data, images with a wide dynamic range
In an image pickup apparatus for obtaining an image, an image pickup element for picking up an object and an exposure amount for the image pickup element are set to n or more stages (n ≧ 3).
The object is imaged by changing it, and from the first time interval to the n-th time
In the interval, the first exposure to the n-th exposure
Control means for controlling output of an image picked up by the camera
And a second parallel arrangement for storing image data corresponding to pixels.
One image memory and a second image memory, and an address corresponding to each pixel with respect to the first image memory
Prior to writing the image data to the
Data control means for reading data from the first image memory and the image sensor in the m-th (2 ≦ m ≦ n) time interval, and a brightness value read from the first image memory; Calculating means for calculating a combined brightness value up to the m-th exposure value from an m-th brightness value of image data obtained by imaging with the m-th exposure amount output from the imaging device; and Select one of the output and the output of the calculation means
A first selecting means for outputting to the first image memory, an output of the second image memory, and an output of the calculating means.
A second selection means for selecting whichever, in the first time interval, and stores the output in the first image memory by selecting the output of the imaging device by said first selecting means, the s ( In the time interval of 2 ≦ s ≦ n−1),
The output of the calculating means is selected by the first selecting means, the output is stored in the first image memory, and the output of the calculating means is selected by the first selecting means in an n-th time interval. Storing the output in said second image memory;
In the first p (1 ≦ p ≦ n- 1) of the time interval, by said second selecting means selects the output of the second image memory, in the zone of the n, by the second selection means,
Control means for controlling the output of the calculation means to be selected .