JPH0923372A - Image input device - Google Patents

Abstract

(57) [Abstract] [Objective] To provide an image input device capable of obtaining a high-quality digital image signal even for a subject having a large contrast without using an A / D converter having high precision and high resolution. To do. [Constitution] The image pickup device 1A is controlled to control the exposure time by an exposure control device 5, and carries out N times of image pickup for the same object to be photographed by changing the exposure time. , The modulator 2, the demodulator 3, the A / D converter 4, and the address controller 7, and sequentially stored in the N first to Nth image memories 6a prepared in the image storage device 6. It Then, in the gradation synthesizer 8, gradation synthesis is performed based on the N images from the image accumulator 6 and a new digital image signal is output. Even if the D converter 4 does not have high precision and high resolution, it is possible to obtain a high-quality digital image signal.

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 configuration shown in FIG. 5 is generally well known. That is, the image input device includes an image pickup device 1 that outputs an electric signal corresponding to a subject, a modulator 2 that applies a format required for the device to an output signal of the image pickup device 1, and the modulator 2. Demodulator 3 for demodulating the output signal of the device 2
And an analog-digital converter (hereinafter, referred to as “A /
D 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 apparatus, in order to obtain an output signal with good image quality, particularly for an object to be photographed with a large contrast, which is a difference in brightness and darkness, an A / D converter is required. 4 requires high precision and high resolution, which causes a problem of increasing the price of the device.

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. Another object of the present invention is to achieve high-resolution A /
An object of the present invention is to provide an image input device which can obtain a high-quality digital image output signal with low noise without using a D converter.

[0007]

According to a first aspect of the present invention, there is provided an image input device, which is an image pickup means for converting an optical image signal from an object to be photographed into an electric signal and an output signal of the image pickup means into a digital signal. In the image input device, the exposure control means for changing the exposure time of the image pickup means over a predetermined number of times, and the image signals having different exposure times are input through the signal conversion means. Then, while storing each of them, a storage unit that can read out each of these storage data and a gradation synthesizing unit that outputs an image signal that is gradation-synthesized based on a plurality of image signals read from the storage unit. And is provided with,
In the gradation synthesizing means, based on a predetermined number of digital image signals, gradation synthesizing is performed under predetermined conditions to generate and output a new digital image signal. A high quality digital image signal can be obtained without using a high resolution A / D converter. You.

An image input apparatus according to a second aspect of the present invention includes image pickup means for converting an optical image signal from a subject 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. In the image input device provided, an image pickup control unit that controls the operation of the image pickup unit so that the same image pickup target is picked up a predetermined number of times by the image pickup unit, and the image pickup unit through the signal conversion unit. While storing a predetermined number of image signals obtained by the above, each of the stored data can be read out, and a plurality of image signals are read from the storage means, and the arithmetic mean of the plurality of image signals is read. And a high-quality digital signal with less noise without using an A / D converter with high accuracy and high resolution. Those which can be obtained Le images.

An image input apparatus according to a third aspect of the present invention comprises an image pickup means for converting an optical image signal from an object to be photographed into an electric signal, and a signal conversion means for converting an output signal of the image pickup means into a digital signal. In the image input device provided, a digital image signal for a predetermined number of times of image pickup by the image pickup means is input through the signal conversion means,
Each time each digital image signal is input, the arithmetic mean value with the digital image signals input until then is calculated,
When the arithmetic mean value is calculated based on the number of digital image signals corresponding to the predetermined number of times, the digital image signal having the arithmetic mean value is output, and the signal processing means is provided, which is highly accurate. Use a high resolution A / D converter. As a result, a high-quality digital image with less noise can be obtained.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of an image input apparatus according to the present invention will be described below with reference to FIGS. Here, FIG. 1 is a block diagram showing a device configuration of the image input device according to the invention of claim 1.
FIG. 4 is a flowchart showing a procedure of a gradation synthesizing process in the image input device shown in FIG. 1, FIG. 3 is a block diagram showing a device configuration of the image input device according to claim 2, and FIG. 4 is a configuration diagram showing a device configuration in the image input device according to claim 3. FIG. 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 apparatus according to the first aspect of the invention will be described with reference to FIGS. 1 and 2. The 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 and a modulator 2.
Although the demodulator 3 and the A / D converter 4 are basically the same as the conventional device described in FIG. 5, this device further controls the exposure of the imager 1A. An exposure controller 5, an image accumulator 6 for storing the output signal of the A / D converter 4 in an area designated by the address controller 7,
An address controller 7 that controls the address of the image storage device 6 in accordance with the exposure control of the exposure controller 5 with respect to the image pickup device 1A;
And a gradation synthesizing unit 8 for synthesizing the output signals from the image storage unit 6 and outputting the synthesized gradation.

The image pickup device 1A as an image pickup means is, for example,
An image pickup tube or CCD element is used to convert an optical image signal from an image pickup target into an electric signal.
The electric signal from is converted by the modulator 2 into an image signal of a predetermined format, for example, an NTSC image signal.

This image pickup device 1A is basically the same as the one used conventionally, but in this embodiment, the exposure is changed in accordance with a control signal from an exposure control device 5 which will be described later. It can be changed.

The demodulator 3 demodulates the input signal from the modulator 2 and outputs RGB signals if the input signal is a color signal, for example, and 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 as a signal converting means and stored in the image storage 6 as described later.

The exposure controller 5 as exposure control means controls the exposure time of the image pickup device 1A by changing the control signal for controlling the exposure of the image pickup device 1A. The image accumulator 6 as an image signal storage means is an A / D converter 4
Which stores the digital image signal output from
In this embodiment, the first to Nth image memories 6a are provided, and more specifically, for example,
A rewritable storage element represented by a RAM or the like is suitable. In addition, in FIG. 1, the first to Nth image memories 6a are represented as image memories 1 to N, respectively.

An address controller 7 as an address control means designates in which image memory 6a the digital image signal output from the A / D converter 4 is stored in the image storage device 6. Is. In FIG. 1, it is equivalently represented by a switch. That is, the electronic switch is composed of the movable contact 7a and the N fixed contacts 7b, and which fixed contact 7b the movable contact 7a is connected to depends on the exposure control of the exposure controller 5 for the image pickup device 1A. It is decided according to the details (details will be described later).

The gradation synthesizing unit 8 serving as a gradation synthesizing unit reads out the image signals accumulated in the image accumulating unit 6 and performs gradation synthesizing and outputs the details. It will be described later with reference to the flowchart of FIG.

In such a configuration, first, when obtaining an image signal for one object to be photographed, the exposure controller 5 changes the exposure time of the image pickup device 1A into N steps, and outputs the image pickup device 1A at each exposure time. The signal is modulated and demodulated and converted into a digital signal by the A / D converter 4. Here, as a specific example of changing the exposure time in N stages, for example, the ratio of the exposure time is 2 ^0: 2 ^1: 2 ^2: ·
・: It is possible to change so that it becomes 2 ^(N-1) .

The digital image signal output from the A / D converter 4 at each exposure time passes through the address controller 7 to the first image memory 6a (referred to as "image memory 1" in FIG. 1). ) Is to be stored in order. That is, when the exposure time is gradually increased as described above, the digital image signal with the shortest exposure time is stored in the first image memory 6a. Each image memory 6a
The digital image signal for the longest exposure time is stored in the Nth image memory 6a.

Then, after the storage in the image storage device 6 is performed as described above, the stored digital image signal is read out by the gradation synthesizing unit 8 and the gradation synthesizing is performed as described below. Is done.

FIG. 2 is a flow chart showing the procedure of the gradation synthesizing process performed by the gradation synthesizing unit 8. The contents will be described below with reference to FIG. To describe the outline of the entire gradation synthesizing process, one digital image is newly obtained from a plurality of digital images obtained for the same subject.

That is, it is premised that this type of image is composed of a plurality of pixels, the upper limit of the pixel value indicating the gradation of the pixel is set, and each pixel forming a new image is set. With regard to the above, the one whose exposure amount is close to the upper limit of this pixel value is selected from the plurality of digital images stored in the image storage 6, and one digital image is newly constructed by the pixels selected from the plurality of images. It is designed to output.

The specific processing procedure will be described with reference to FIG. 2. First, when starting the processing, the upper limit of the pixel value is set (step 100 in FIG. 2). The setting of the upper limit value is determined in consideration of various electrical requirements of the side using the output signal of the present apparatus, and the specific value cannot be limited here.

Next, the image signals are fetched from the image accumulator 6 to the gradation synthesizer 8 and arranged in the order of the images with the largest exposure amount, and the scanning described below is started (step 102 in FIG. 2). reference). First, of a plurality of image signals read from the image accumulator 6, the pixel value of a pixel at a predetermined position (for example, a pixel located at the upper right corner of the image) is first calculated for the image signal with the largest exposure amount. It is determined whether or not it is smaller than the defined upper limit value (see step 104 in FIG. 2).

When it is determined that the pixel value is larger than the upper limit value (in the case of NO), in the image signal having the next exposure amount, the pixel value of the pixel at the same predetermined position is similarly determined. It is determined whether or not it is smaller than the upper limit value (see steps 110 and 104 in FIG. 2).

On the other hand, when it is determined that the pixel value is smaller than the upper limit value (in the case of YES), the number of the image to which the pixel belongs (for example, the image with the largest exposure amount is 1 and the exposure amount is (Numbers that are assigned in ascending order in the order of decreasing), are multiplied by the upper limit value of the initially set pixel value (see step 100 in FIG. 2), and the pixel value is added to the multiplication result. Is set as a new pixel value (step 106 in FIG. 2).

Here, the physical meaning of determining a new pixel value as described above is that the upper limit of the pixel value indicating the gradation of each image is set to the image number of the image having different exposure amount of N gradations. By multiplying, the gradation that is the basis of the image in the overall gradation of 1 to N steps is obtained, and by adding the pixel value to that value, all gradations of the image of 1 to N steps are obtained. The gradation of the pixel inside is required.

After the above-mentioned processing, it is determined whether or not scanning has been performed on the entire screen (see step 108 in FIG. 2),
If it is determined that the pixel is not yet finished (in the case of NO), the same process as described above is performed on the corresponding next pixel (see step 112 in FIG. 2).
On the other hand, if it is determined that the scanning for the entire screen is completed (YES), the gradation synthesizer 8 outputs a new image signal that is gradation-combined as described above. A series of processing is completed (see step 114 in FIG. 2).

In the above embodiment, when the A / D converter 4 has 8 bits, an image of (2 ⁸ × N) gradation is obtained from the N images accumulated in the image accumulator 6. Will be possible. As described above, according to the present embodiment, it is possible to obtain an image signal of high gradation without using an A / D converter having a particularly high resolution.

In the above embodiment, the exposure controller 5, the address controller 7 and the gradation synthesizer 8 are shown as independent, but these are so-called CP.
It is more preferable because it can be easily realized by using U. In this case, an interface circuit is required for connection with peripheral circuits such as the image pickup device 1A.

Next, the second embodiment will be described. Since the basic configuration of the device in this embodiment is the same as that shown in FIG. 1, the description of the so-called hardware configuration will be omitted. First, the characteristic points of the second embodiment will be described generally. The number of bits of the digital image signal output from the A / D converter 4 is set to a predetermined value (for example, N) of the number of times of image pickup by the image pickup device 1A. The number of bits is increased by a corresponding amount, and the resolution of the digital image signal is substantially improved without increasing the resolution of the A / D converter 4.

That is, for example, if the number of bits of the A / D converter 4 is 8 bits, the digital image signal output from the gradation synthesizer 8 is (8 + N) -bit image data. That is, the image has 2 ^{(N + 8)} gradations.

Specifically, when N = 1 is explained,
If there are two 8-bit images, A and B, respectively, and the gradation is 0 for black and 255 for white, assume that for A and B, the exposure time for B is 1/2. When an image of a very bright object is picked up, the pixel value becomes 255 in A, and that portion cannot be fully expressed, but in B, the gradation can correspond, and the pixel value in the brightest portion is 255 or less, for example 240.

When the two images of A and B are combined, the portion where the pixel value of A is 254 or less is not changed and 2
55 is more than 255, so the pixel value of B +25
6 is the pixel value. This is an image with gradation of 0 to 511, that is, 9 bits.

Next, with reference to FIG. 3, an embodiment of the image input apparatus according to the present invention will be described. In FIG. 3, the same components as those shown in FIG. 1 are designated by the same reference numerals, detailed description thereof will be omitted, and different points will be mainly described below.

In the example shown in FIG. 3, the image input device corresponds to a predetermined number of images, and a counter 15 for counting a predetermined number of times (for example, N times) of the same image pickup target by the image pickup device 1B as an image pickup means. A frame memory 16 as an image signal storage means having a memory capacity, and an averaging means 17 as an averaging means for performing an averaging on the image signals read from the frame memory 16 are provided. . Note that, in FIG. 3, the first to Nth memories 16a that form the frame memory 16 are referred to as memories 1 to N, respectively.

In such a structure, when the image pickup is started, the counting operation of the counter 15 makes it possible to obtain N image signals for the same image pickup object.
The address controller 7 sequentially connects the movable contact 7a to each fixed contact 7b according to the count value of the counter 15, and thereby the N memories 16 constituting the frame memory 16 are connected.
In a, the image signals at the time of each image pickup are input from the A / D converter 4 and stored.

Therefore, N image signals are stored in the frame memory 16, and the stored image signals are read out by the averaging unit 17, which is added to calculate the average. It is supposed to be done. Therefore, each pixel value in one image signal obtained from the arithmetic mean 17 becomes the result of arithmetic mean of pixel values in N image signals.

As described above, by obtaining the new image signal by obtaining the addition average by using the N image signals, even if the A / D converter having a relatively low resolution is used, compared to the conventional case. It is possible to obtain a high quality image signal with less noise.

Next, an image input apparatus according to the invention of claim 3 will be described with reference to FIG. Note that FIG.
Constituent elements that are the same as the constituent elements shown in FIG. 6 are given the same reference numerals, detailed description thereof will be omitted, and hereinafter, different points will be mainly described. The frame memory 18 as the image signal storage means in this example is different from the example shown in FIG. 3 in that it has a memory capacity for one image only and does not have a memory capacity for a plurality of images. is there.

Further, between the averaging unit 17 as the averaging unit and the frame memory 18, the reading from the frame memory 18 according to the count of the counter 15 as the counting unit and the averaging in the averaging unit 17 are performed. Is calculated, and writing to the frame memory 18 is performed.

That is, in this embodiment, the same number of times the image pickup object is picked up a predetermined number of times (for example, N times) is the same as in the image input device shown in FIG. 3, but the image pickup device 1B is used. The processing procedure of the signal obtained from the above is different as described below.

First, when the first image pickup is performed, the output signal of the image pickup device 1B is stored in the frame memory 18 as a digital image signal via the modulator 2, the demodulator 3 and the A / D converter 4. The Rukoto.

Next, when the second image pickup is performed, the digital image signal of the first time is input from the frame memory 18 to the averaging unit 17, while the second image is input to the frame memory 18 in the same manner as described above. The digital image signal for the second time is A
It is input from the / D converter 4 and stored.

Subsequently, when the third image pickup is performed, the digital image signal for the second image pickup from the frame memory 18 is input to the arithmetic mean 17, and is already accumulated in the arithmetic mean 17. The arithmetic mean with the digital image signal for the first image pickup is calculated, and the calculation result is accumulated in the arithmetic mean 17, while the digital image signal from the A / D converter 4 for the third image pickup is calculated. It will be stored in the frame memory 18.

Here, the arithmetic operation in the averaging unit 17 is
For the first and second digital image signals, the average value is simply calculated. After that, the average value (additional average value) is calculated by multiplying the previous addition average value by the number once added to the previous time. A value obtained by adding the value of the newly input digital image signal to the result and further dividing the value by the number of times of input is the addition average value.

Thereafter, the previous digital image signal is input from the frame memory 18 to the averaging unit 17 every time the image capturing is performed up to a predetermined number of times, and the averaging unit 1
In the inside of the frame memory 1, the arithmetic mean with the accumulated average value up to the last time is accumulated and accumulated.
The storage of a new digital image signal in 8 is repeated.

When a predetermined number of times of image pickup is performed, the image data is taken into the arithmetic mean 17 through the frame memory 18 as it is, and the last arithmetic mean with the arithmetic mean until then is calculated. The calculation result is the frame memory 1
8 and is read out from the frame memory 18 to the outside as needed.

In this embodiment, the number of bits of one pixel (each component of RGB or monochrome signal) in the frame memory 18 is A / A from the viewpoint of reducing the calculation error.
The number of bits is preferably larger than the number of bits in the D converter 4.

[0050]

As described above, according to the first aspect of the present invention, a plurality of image signals are combined on the basis of a plurality of image signals to obtain a new image signal which is subjected to gradation synthesis. Since a high-quality image signal can be obtained based on the image signal of, the high-precision and high-resolution A / D converter is unnecessary even for a subject having a large contrast, and the image quality can be improved. In addition, since a high-precision and high-resolution A / D converter is not required, the cost of the device can be reduced.

Further, in the invention according to the second or third aspect, based on the plurality of digital image signals, the arithmetic mean of the plurality of digital image signals is obtained to obtain a new digital image signal. For example, even if the object to be photographed is relatively dark, an image having an average value obtained by several times of imaging can be obtained, so that the image quality can be improved without using a high-resolution A / D converter. There is an effect that can be done.

[Brief description of drawings]

FIG. 1 is a configuration diagram showing a device configuration of an image input device according to a first aspect of the 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 device configuration in the image input device according to claim 2;

FIG. 4 is a configuration diagram showing a device configuration in an image input device according to a third aspect of the invention.

FIG. 5 is a configuration diagram showing a conventional device configuration example.

[Explanation of symbols]

1, 1A, 1B ... Imager, 2 ... Modulator, 3 ... Demodulator, 4 ... A / D converter, 5 ... Exposure controller, 6 ... Image accumulator, 6a ... Image memory, 7 ... Address controller, 7a ... movable contact, 7b ... fixed contact, 8 ... gradation synthesizer, 15 ... counter, 16 ... frame memory, 17 ... summing averager, 18 ... frame memory

Claims (3)

[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. The exposure control means for changing the exposure time of the means over a predetermined number of times, and the image signals having different exposure times are input and stored through the signal conversion means, while these stored data can be read out respectively. An image input device comprising: a storage unit; and a gradation synthesizing unit that outputs an image signal subjected to gradation synthesis based on a plurality of image signals read from the storage unit. 2. 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. Image pickup control means for controlling the operation of the image pickup means so that the same image pickup target is imaged a predetermined number of times, and a predetermined number of image signals obtained by the image pickup means via the signal conversion means, Each storage unit is provided with storage means for reading the stored data, and arithmetic means for reading out a plurality of image signals from the storage means and calculating an arithmetic mean of the plurality of image signals. An image input device characterized by the following. 3. An image input apparatus comprising: an image pickup means for converting an optical image signal from an object to be photographed into an electric signal; and a signal conversion means for converting an output signal of the image pickup means into a digital signal. A digital image signal for a predetermined number of times of image pickup by the means is input via the signal conversion means, and each time each digital image signal is input,
An arithmetic mean value with the digital image signals input until then is calculated, and when the arithmetic mean value based on the number of digital image signals corresponding to the predetermined number of times is calculated, a digital image signal having the arithmetic mean value is calculated. An image input device comprising a signal processing means for outputting.