JPH099154A - Image input device - Google Patents

Abstract

PURPOSE: To provide the image input device from which an excellent quality digital image signal is obtained even in the case of an image pickup object with a high contrast without using an A/D converter with high accuracy and high resolution. CONSTITUTION: An image pickup device 1A is subject to control for exposure time by an exposure controller 5 to pick up the same object for N times with different exposure times, a digital image signal is given to a frame memory 6 via a modulator 2, a demodulator 3, and an A/D converter 4 every time image pickup is conducted, and every time the digital image signal is received by the frame memory 6, a gradation synthesizer 7 reads the digital image signal, selects a picture element satisfying a prescribed condition to decide a new picture element, writes recording of the picture element whose value is decided to a decision picture element table of a table memory 8, generates a new image by gradation synthesis from N sets of digital image signals with different exposure times finally and each picture element is stored in an image storage device 9 in the image input device.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image input device for converting an image signal picked up by an image pickup device such as a video camera into a digital signal, and more particularly to improving the output image quality and simplifying the structure. The present invention relates to an improved image input device.

[0002]

2. Description of the Related Art An image input device for converting an image signal obtained by a so-called image pickup device represented by an image pickup tube into a predetermined digital signal and outputting the digital signal is, for example,
The structure shown in FIG. 3 is generally well known. That is, this device includes an image pickup device 1 that outputs an electric signal corresponding to a subject, and a modulator 2 that applies a modulation of a format required for the device to the output signal of the image pickup device 1.
, A demodulator 3 for demodulating the output signal of the modulator 2, and an analog / digital converter (hereinafter referred to as "A / D") for converting an analog output signal from the demodulator 3 into a digital signal.
Converter ". ) 4 is provided.

In the modulator 2, for example, the image input device is NT
If it is intended to handle an SC image signal, processing for converting the signal from the image pickup device 1 into a composite signal conforming to the NTSC standard is performed. And demodulator 3
Is a signal subjected to such a modulation, that is, if it is an NTSC color image signal, it is demodulated into RGB signals, and if it is a monochrome image signal, it is demodulated into a luminance component signal and output. .

[0004]

However, in the above-mentioned conventional image input device, in order to obtain an output signal with good image quality, particularly for an object to be photographed with a large contrast, which has a difference in brightness and darkness, an A / D converter is used. The converter 4 is required to have high accuracy and high resolution, which causes a problem that the cost of the device is increased.

Further, when the object to be photographed is relatively dark, a high resolution A / D converter is required in order to obtain an output signal with good image quality without increasing noise, and the cost of the apparatus is increased. There was a problem of inviting.

The present invention has been made in view of the above circumstances, and a high-quality digital image output signal can be obtained even in a subject having a large contrast without using a high-precision, high-resolution A / D converter. An object is to provide an image input device that can be obtained.

[0007]

According to a first aspect of the present invention for solving the problems of the conventional example, an image pickup means for converting an optical image signal from an object to be photographed into an electric signal, and an output of the image pickup means. An image input device comprising a signal conversion means for converting a signal into a digital signal, wherein an exposure control means for controlling an exposure time of the image pickup means and a digital image signal output from the signal conversion means are stored. ,
A storage unit capable of reading the stored data and a plurality of digital image signals having different exposure times are input via the storage unit, and gradation combination is performed based on the plurality of digital image signals having different exposure times. And a gradation synthesizing means for generating a new image signal thus generated.

According to a second aspect of the present invention for solving the above-mentioned problems of the conventional example, in the image input device according to the first aspect, the gradation synthesizing means exposes as a pixel constituting one new image. From a plurality of image signals of different time, select the pixel closest to the predetermined pixel value, to a predetermined value determined according to the exposure time of the original image including the selected pixel,
It is characterized in that it is a gradation synthesizing means for adding pixel values of the pixels to obtain a new pixel value.

[0009]

According to the first and second aspects of the present invention, when the exposure of the image pickup means is set and the image is picked up according to the control of the exposure control means, the storage means converts the signal into a digital signal. The stored image signal is stored, and this digital image signal is taken in by the gradation synthesizing means, that is, every time the gradation synthesizing means stores digital image signals having different exposure times in the storage means An image signal is taken in, pixels that can be used for gradation synthesis are selected from this image signal under predetermined conditions, and finally a new image base is selected from a plurality of digital image signals with different exposure times. Multiple pixels are selected,
An image input device in which a new image is formed by gradation synthesis based on these plural pixels, so that a high-quality digital image signal can be obtained without using an A / D converter with high accuracy and high resolution. Is.

[0010]

Embodiments of the image input apparatus according to the present invention will be described below with reference to FIGS. here,
FIG. 1 is a configuration diagram showing a device configuration in an embodiment of an image input device according to the present invention, and FIG. 2 is a flow chart diagram showing a procedure of gradation synthesis processing in the image input device shown in FIG. is there. The members, arrangements, and the like described below do not limit the present invention and can be variously modified within the scope of the gist of the present invention.

First, an image input device (hereinafter referred to as "this device") in the present embodiment includes an image pickup device 1A represented by an image pickup tube, a modulator 2, a demodulator 3, and an A / D converter. 4 is basically the same as the conventional device described in FIG. 3, but this device further includes an exposure controller 5 as an exposure control unit, a frame memory 6 as a storage unit, It comprises a gradation synthesizer 7 as a gradation synthesizing means, a table memory 8 as a table storing means, and an image accumulator 9.

The image pickup device 1A as an image pickup means is, for example,
An image pickup tube, a CCD element, or the like is used to convert optical image information into an electric signal. In the image pickup device 1A, the exposure time can be changed stepwise by a control signal from the exposure controller 5. That is, the exposure controller 5 in the present embodiment can change the exposure time of the image pickup device 1A to a predetermined step, for example, N steps. Here, as a specific example of N-step exposure time adjustment,
For example, the ratio of each exposure time is 2 ^(N-1) : 2 ^(N-2) :
・: 2 ² : 2 ¹ : 1 can be changed to a geometric progression.

The demodulator 3 demodulates the input signal from the modulator 2 and outputs RGB signals if the input signal is, for example, a color signal. For example, the input signal is monochrome. If so, the signal of the luminance component is output. The output signal of the demodulator 3 is converted into a digital signal by the A / D converter 4 and stored in the frame memory 6.

The frame memory 6 is a memory for temporarily storing a digital image signal. In this embodiment, the exposure time is set by the exposure controller 5, and the image from the image pickup device 1A at that exposure time is set. The digital image signal for the image is stored every time the image is obtained. The gradation synthesizer 7 performs gradation combination on the digital image signals sequentially read from the frame memory 6 in the procedure described below.

The table memory 8 stores a table for confirming whether or not a new pixel value has been determined by gradation synthesis in the gradation synthesizer 7, and will be described later by the gradation synthesizer 7. Then, predetermined writing is performed. The image accumulator 9 is a memory for storing the image signal generated by gradation synthesis by the gradation synthesizer 7.

In such a configuration, in order to obtain an image signal by gradation synthesis, the exposure controller 5 changes the exposure time of the image pickup device 1A in N steps, and the output signal of the image pickup device 1A at each exposure time is modulated. It is demodulated and converted into a digital signal by the A / D converter 4.

Each time the digital image signal output from the A / D converter 4 at each exposure time is stored in the frame memory 6, the gradation synthesizer 7 reads the stored digital image signal. Then, the gradation synthesis is performed as described below.

FIG. 2 is a flow chart showing the procedure of the gradation synthesizing process performed by the gradation synthesizing unit 7. The contents will be described below with reference to FIG. The outline of the entire gradation synthesizing process is described above. A new digital image is obtained by gradation synthesizing from a plurality of digital images having different exposure times obtained for the same subject.

The specific processing procedure will be described with reference to FIG. 2. First, when starting the processing, the upper limit value of the pixel value, that is, the upper limit value of the gradation is set (step 1 in FIG. 2).
00). For example, if the resolution of the A / D converter 4 is 8 bits, the upper limit value of gradation is set to 255.

Then, the exposure controller 5 controls the exposure time of the image pickup device 1A to be the maximum exposure amount first among the predetermined N exposure amounts, and the picked-up image at this time is modulated. The digital image signal is taken into the frame memory 6 via the device 2, the demodulator 3 and the A / D converter 4 (see steps 102 and 104 in FIG. 2).

Next, the gradation synthesizer 7 scans each pixel of the image stored in the frame memory 6 (see step 106 in FIG. 2). That is, the image signal is read from the frame memory 6 to the gradation synthesizer 7. Then, of the plurality of pixels forming this image signal, first, one pixel is selected and whether or not this pixel is an undetermined pixel, that is, whether or not gradation combination has not been completed yet. If it is determined (see step 108 in FIG. 2) and it is determined that the gradation synthesis has already been completed (NO in step 108), the process proceeds to step 114 described later.

On the other hand, if it is determined that the gradation synthesis has not been completed (YES in step 108).
In the case of), the process proceeds to the pixel value determination process (see 110 in FIG. 2). It should be noted that, at the time of starting the above-mentioned scanning, the position of the pixel in one image to be started is arbitrary because it is not related to the essence of the present invention, and is not particularly specified here.

Next, in step 110, it is determined whether or not the pixel value, that is, the gradation, of the above-mentioned pixel is smaller than the upper limit value defined previously (see step 110 in FIG. 2). Then, when it is determined that it is smaller than the upper limit value (in the case of YES), the process proceeds to the next step 112.

On the other hand, when it is determined that the upper limit value is exceeded (in the case of NO), it is determined that the pixel value cannot be determined, and the necessary writing is performed in the determined pixel table of the table memory 8 to be described later. The process proceeds to 114 (see step 118 in FIG. 2).

Here, the determination pixel table stored in the table memory 8 is, so to speak, a confirmation for confirming whether or not the pixel value is determined for each pixel forming the image by gradation synthesis as described later. It should be called a list, and when it is determined that the pixel is an undetermined pixel in this step 118, "0" is written in the corresponding pixel.

In step 112, based on the determination that the pixel value of the pixel to be determined in the previous step 110 does not exceed the upper limit value, the pixel is set as one pixel of a new image signal by gradation synthesis. In use, the following pixel value conversion for gradation synthesis is performed. That is, the number of the image in which the pixel is used is set in the step 1 first.
A value obtained by adding 1 to the upper limit value set at 00 (256 in this embodiment) and adding the pixel value of the pixel to the value is used as a new pixel value (step 112 in FIG. 2). reference). Then, "1" is written to indicate that the pixel value has been determined for the corresponding pixel in the determined pixel table of the table memory 8. Further, this new pixel value will be stored in the image storage 9.

Here, the number of the image in which the pixel is used is a number given in ascending order to the image captured in the frame memory 6 in the previous step 104. In the present embodiment, since the images are captured in the descending order of the exposure amount and the scanning as described above is performed,
A number starting from 1 is added in order from the image captured with the maximum exposure amount, and the last number is N according to the number of switching of the exposure time.

Therefore, when the pixel is selected from the image with the shortest exposure time, this step 112
The new pixel value calculated in is the pixel value originally possessed by the pixel plus (N × 256). In this way, 256 pixels are added according to the image that includes the pixels that are adopted as the pixels that form the new image (in other words, according to the exposure time of the image). Even if the gradation is represented by 8 bits, it is possible to obtain an image with (2 ⁸ × N) gradations. Therefore, a special high resolution A / D converter is used. It is possible to obtain an image signal with finer gradation without using the image signal.

The relationship between the new pixel value obtained as a result of the gradation synthesis and the exposure time is as follows: a pixel having a longer exposure time has a smaller pixel value, and a pixel having a shorter exposure time has a larger pixel value. Therefore, the relationship between the pixel value before gradation synthesis and the exposure time is just opposite.

The relationship between the pixel value and the exposure time should be determined from the viewpoint of signal processing in an external device using the output signal from the present device, and the relationship between the pixel value and the exposure time as described above. If the relationship is inconvenient in the external device from the viewpoint of signal processing, data conversion is performed in the external device, or in step 112 of FIG. 2, each image having different exposure time is attached. Contrary to the above numbering, the number N is assigned to images with a long exposure time.
The reverse relationship can be obtained by adding the suffixes and the suffixes in descending order, so this is not an essential problem.

After the pixel value conversion is performed as described above, it is determined whether or not the scanning has been completed for all pixels in one screen (see step 114 in FIG. 2), and one screen is still displayed. When it is determined that the processing is not to be ended (in the case of NO), the processing after step 108 is similarly performed for the next pixel of the same image (step 1 in FIG. 2).
20).

On the other hand, when it is determined that the above-mentioned scanning is completed for all the pixels of one screen (in the case of YES), it is determined whether or not the above-described scanning is performed for all the images. Will be determined (see step 116 in FIG. 2).

In the case of this embodiment, N having different exposure times are used.
When it is determined whether or not the above-described scanning is performed on each of the images, and it is determined that the scanning is completed (YE
In the case of S), the digital image signal stored in the image storage device 9 is output to the outside, and the series of processing ends (see step 124 in FIG. 2).

On the other hand, when it is judged that the processing is not yet finished (N
(In the case of O), the image is taken while changing the exposure (see step 122 in FIG. 2), the image is taken into the frame memory 6, and the same processing as described above is performed for this image. Will be seen.

In the above embodiment, the gradation synthesizer 7
Although the table memory 8 and the table memory 8 are shown as being independent of each other, they can be easily realized by using a so-called CPU and are more preferable.

Further, in the above embodiment, the modulator 2
Although the demodulator 3 and the demodulator 3 are not necessarily provided, they may be configured so that the output signal of the image pickup device 1A is directly converted into a digital signal by the A / D converter 4.

Further, in the present embodiment, the ratio of the exposure time is set so as to be a geometric progression, but needless to say, it is not limited to such a ratio, and various settings are possible. For example, the exposure time ratio may be set to be an arithmetic progression.

[0038]

As described above, according to the present invention,
By configuring so as to obtain a new image signal by gradation composition based on a plurality of image signals having different exposure times, gradation composition can be performed by performing gradation composition based on a plurality of image signals. Since it is possible to obtain a fine image signal, it is possible to obtain high accuracy even for a subject with a large contrast.
There is an effect that a high resolution A / D converter is unnecessary and the image quality can be improved. Further, since a high-precision and high-resolution A / D converter is not required, there is an effect that the cost of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a device configuration in an embodiment of an image input device according to the present invention.

FIG. 2 is a flowchart showing a procedure of gradation combination processing in the image input device shown in FIG.

FIG. 3 is a configuration diagram showing a configuration example of a conventional device.

[Explanation of symbols]

1, 1A ... Imager, 2 ... Modulator, 3 ... Demodulator, 4
... A / D converter, 5 ... Exposure controller, 6 ... Frame memory, 7 ... Gradation synthesizer, 8 ... Image data memory,
9 ... Image accumulator

Claims (2)

[Claims] 1. An image input device comprising image pickup means for converting an optical image signal from an object to be photographed into an electric signal and signal conversion means for converting an output signal of the image pickup means into a digital signal. Exposure control means for controlling the exposure time of the means, storage means for storing the digital image signal output from the signal conversion means, and readable storage data, and different exposure times via the storage means. A plurality of digital image signals are inputted, and a gradation synthesizing means for generating a new image signal subjected to gradation synthesizing based on the plurality of digital image signals having different exposure times is provided. Image input device. 2. The gradation synthesizing means selects a pixel closest to a predetermined pixel value from a plurality of image signals having different exposure times as a pixel forming a new image and selects the selected pixel. 2. The gradation synthesizing means for adding the pixel value of the pixel to a predetermined value determined according to the exposure time of the original image including the gradation value to obtain a new pixel value. Image input device.