JPH08154211A - Image pickup device - Google Patents

Abstract

PURPOSE: To attain image pickup of an object moving at a high speed and to extent the dynamic range by dividing a light receiving plane of a 2-dimension light receiving element into very small areas as if the light were received from the same part of the image pickup object. CONSTITUTION: An ND filter made of metallic vapor-deposition film is formed on the light receiving plane of a CCD image pickup element 1 as an extinction filter FL in plural stripes. Thus, the light receiving plane is divided into very small areas comprising extinction areas subject to extinction and non-extinction areas not subject to extinction, and a signal processing means SP regards it that the very small areas receive a light from the same part of an object and provides an output of an image signal with respect to the very small areas. Thus, the dynamic range for a stronger intensity of a received light and the dynamic range for a weaker intensity of a received light are provided. Since a detection signal of the extinction area and a detection signal of the non- extinction area are read simultaneously during the scanning for one image picture, the reduction in an output signal is suppressed to the utmost and then an image pickup object moving at a high speed is picked up.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image pickup apparatus having a two-dimensional light receiving element for receiving light from an object to be imaged.

[0002]

2. Description of the Related Art Such an image pickup device uses a CCD image pickup device, a MOS image pickup device, an image pickup tube, or the like to transmit light from an image pickup object.
A three-dimensional light receiving element receives light and photoelectrically converts the light to capture an image of the imaging target. In order to properly image the imaging target, the amount of light from the imaging target needs to be within the dynamic range of the two-dimensional light receiving element, that is, the range in which the output signal appropriately changes according to the amount of received light. However, the actual imaging target is, for example, an image of the vicinity of the exit of the tunnel from the inside of the tunnel, or an image of a place where a strong sunlight and a shaded area are mixed. , A wide dynamic range may be required.

In such a case, if the two-dimensional light receiving element normally takes an image, an object to be imaged cannot be properly imaged due to occurrence of halation or the like. Therefore, conventionally, it has been considered that a CCD image pickup device is adopted as a two-dimensional light receiving device and the electronic shutter function of the CCD image pickup device is used to widen the dynamic range. That is, when the image signal of the same image pickup target is picked up by changing the shutter speed of the electronic shutter in two steps and the image is picked up with the shutter speed lengthened, when the image signal is saturated beyond the dynamic range of the CCD image pickup device, The configuration is such that an image signal obtained by capturing an image with a short shutter speed is adopted.

[0004]

However, in the above-described conventional configuration, the image pickup target needs to be substantially stopped while the image pickup target is picked up at two shutter speeds, and the image pickup target moving at high speed is picked up. In that case, it is necessary to set the shutter speed to an extremely high speed. If you set the shutter speed to a very high speed, as a result,
The amount of light received by the CCD image sensor will decrease,
There is an inconvenience that the output signal of the CCD image pickup device is lowered. The present invention has been made in view of the above circumstances, and an object thereof is to suppress a decrease in output signal as much as possible and to enable imaging of a moving object that moves at a high speed, and The point is to widen the dynamic range.

[0005]

An image pickup apparatus of the present invention comprises a two-dimensional light receiving element for receiving light from an object to be imaged, and a first characteristic configuration thereof is that the two-dimensional light receiving element receives light. The surface is divided into minute areas that can be regarded as receiving light from the same part of the imaging target, and a neutral density filter that attenuates the amount of light received by one part of the divided areas more than other parts is arranged for each divided area. Then, in the two-dimensional light receiving element, the detection signals of the dimming region by the dimming filter and the non-dimming region that is not dimmed by the dimming filter can be individually read over the entire light receiving surface. The dynamic range of the dimming region and the dynamics of the non-dimming region are determined from the signal reading unit and the signals read by the signal reading unit of the dimming region and the non-dimming region of the minute region to be processed. Having a dynamic range that includes a range is that a signal processing means for conversion into an image signal of the small region is provided.

A second characteristic configuration is the same as the first characteristic configuration, wherein the signal processing means converts the detection signal of the dimming region and the detection signal of the non-dimming region into a digital signal A.
/ D converter and the dimming area, which is converted into a digital signal by the A / D converter, using the detection signal of the dimming area and the detection signal of the non-dimming area of the minute area to be processed as address signals. And a look-up table storing data for outputting an image signal of the minute area having a dynamic range including the dynamic range of the non-dimming area.

A third characteristic configuration is the same as the first characteristic configuration, wherein the signal processing means outputs the detection signal of the non-dimming area to the image when the received light intensity of the non-dimming area is within the dynamic range. When the received light intensity of the non-dimmed area exceeds the dynamic range, the detection signal of the dimmed area is used as the image signal. According to a fourth characteristic configuration, in the first, second or third characteristic configuration, the dimming region and the non-dimming region are:
The two-dimensional light receiving elements are arranged alternately along the horizontal scanning direction.

[0008]

According to the first characteristic configuration of the present invention, on the light receiving surface of the two-dimensional light receiving element, the light receiving amount of a part of each minute region which can be regarded as receiving light from the same part of the image pickup object is received. There is a neutral density filter that attenuates light more than other parts. That is, when the light from the imaging target is imaged on the light receiving surface of the two-dimensional light receiving element, strictly speaking, in the above-mentioned minute area, the light reduction area where the light reduction filter is arranged and the light reduction filter are reduced. Light from different parts of the imaging target will form an image in the non-dimmed area that is not illuminated, but by making the area of the minute area sufficiently small, it is practically possible to image in the dimmed area and the non-dimmed area. The signal processing can be performed assuming that the light from the same part of the object is received.

When the signal reading means reads the detection signals of the dimming area and the non-dimming area separately, the signal processing means detects the detection signal of the dimming area and the non-dimming area in the minute area to be processed. The signal is converted into an image signal for the minute area. The range of the dynamic range with respect to the amount of received light is deviated between the dimming region and the non-dimming region. The non-dimming region has a dynamic range on the side where the received light is weak, and the received light is strong in the dimming region. It will have a dynamic range on the side. Therefore, the image signal after the conversion processing by the signal processing means has a dynamic range in the dimming region, that is, a dynamic range on the side where the received light is strong and a dynamic range in the non-dimming region, that is, a dynamic range on the side where the received light is weak. Can have.

According to the second characteristic configuration of the present invention, the signal processing means outputs the detection signal of the dimming region and the detection signal of the non-dimming region in the microscopic region of the two-dimensional light receiving element to be processed.
/ D conversion is performed, and the signal after the conversion is input to the lookup table as an address signal, and a signal corresponding to the input detection signal of the dimming region and the detection signal of the non-dimming region is a micro region to be processed. Is output from the lookup table as the image signal of. When the look-up table is used in this way, the signal output from the look-up table can be arbitrarily stored in the look-up table, so that no complicated signal processing is required for the address signal, The optimum signal can be output at high speed.

According to the third characteristic configuration of the present invention, the signal processing means outputs the detection signal of the non-dimming area as an image signal of the minute area when the received light intensity of the non-dimming area is within the dynamic range. However, when the received light intensity in the non-dimmed area exceeds the dynamic range, the detection signal in the dimmed area is processed so as to be an image signal in the minute area. That is, even when the dynamic range of the non-dimming area and the dynamic range of the dimming area partially overlap, the detection signal of the non-dimming area is preferentially used, and the light receiving sensitivity of the two-dimensional light receiving element is as high as possible. I am trying to be.

According to the fourth characteristic configuration of the present invention, the light-reducing regions and the non-light-reducing regions in the minute region are alternately arranged along the horizontal scanning direction of the two-dimensional light receiving element, so that the signal reading means is used. In the read signal, the detection signal of the dimming region of the minute region to be processed and the detection signal of the non-dimming region are continuous. Therefore, in the case of performing conversion processing on a minute area to be processed, the signal processing means, once holding the preceding signal of the detection signal of the non-dimmed area or the detected signal of the attenuated area of the minute area, immediately after that. Then, the subsequent detection signal of the minute area is sent, so that the conversion process may be executed from the subsequent detection signal and the detection signal once held previously. That is, the conversion process for one micro area can be executed in series.

[0013]

According to the first characteristic structure, the image signal after the conversion processing by the signal processing means has a dynamic range in the dimming region, that is, a dynamic range in which the received light is strong and a dynamic range in the non-dimming region. That is, it is possible to have a dynamic range on the side where the received light is weak, and moreover, the reading of the detection signal of the dimming region and the reading of the detection signal of the non-dimming region are performed during scanning of one screen. Since they can be performed at the same time, the decrease in the output signal can be suppressed as much as possible, and the dynamic range of the two-dimensional light receiving element can be widened while enabling the imaging of a moving object that moves at high speed.

According to the second characteristic configuration, by using the look-up table as described above, the conversion based on the detection signal of the dimming region and the detection signal of the non-dimming region requires complicated processing. Instead, since it can be performed in an optimal state and at high speed, the operational effect of the first characteristic configuration can be achieved while simplifying the configuration. According to the third characteristic configuration, the effect of the first characteristic configuration can be obtained while the light receiving sensitivity of the two-dimensional light receiving element is maximized as described above.

According to the fourth characteristic configuration, since the conversion processing for one micro area can be executed in series as described above, for example, the dimming area and the non-dimming area of one micro area are two-dimensional. In the configuration in which the light receiving elements are arranged in the vertical scanning direction, it is necessary to detect the detection signal of the dimming region and the detection signal of the non-dimming region separately, and therefore different horizontal scanning is required to read the detection signal of one minute region. It is necessary to read at the timing of, after receiving the preceding signal of the detection signal of the non-dimming area or the detection signal of the dimming area of the minute area to be processed, until receiving the subsequent signal forming a pair, Since the detection signals of other minute areas are mixed and the storage means and the management means for managing the stored information are required, the above-mentioned first, second or 3 The effect by the characteristic configuration is produced. It is possible.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the image pickup apparatus of the present invention will be described below with reference to the drawings. The image pickup apparatus IP shown in FIG. 1 includes a CCD image pickup element 1 that receives light from an image pickup target and photoelectrically converts the light.
A lens 2 for forming an image of light from an image pickup object on the light receiving surface of the CCD image pickup device 1, a signal processing means SP for processing an output signal of the CCD image pickup device 1, and various output image signals of the signal processing means SP. And a video circuit 7 for converting into a video signal of the standard.

The signal processing means SP includes an 8-bit A / D converter 3 for A / D converting the output signal of the CCD image pickup device 1, a latch 4 for temporarily holding the output of the A / D converter 3, and an A. The D / A converter 3 and the output of the latch 4 are used as address inputs for the lookup table 5 and the D / A converter 6 for D / A converting the output of the lookup table 5. The clock 8, the frequency dividing circuit 9, the AND element 10, the inverter element 11, and the delay circuit 12 are provided.

On the light receiving surface of the CCD image pickup device 1, as shown in FIG. 2, an ND filter made of a metal vapor deposition film is formed in a plurality of stripes as a neutral density filter FL, and the neutral density filter FL is used. A dimming region that is dimmed and a non-dimming region that is not dimmed by the dimming filter FL are formed. In FIG. 2, in order to facilitate the explanation of the principle, a total of 8 × 10 80
Although the CCD image pickup device 1 composed of pixels is shown, actually, a device having a pixel number of about 500 × about 500 is used. In FIG. 2, the horizontal direction is the horizontal scanning direction and the vertical direction is the vertical scanning direction. In the neutral density filter FL, each striped portion has a shape extending in the vertical scanning direction with a width of one pixel, and is horizontal. The pixel in which the neutral density filter FL is formed and the pixel in which it is not formed are alternately arranged in the scanning direction.

In the image pickup device IP of this embodiment, the light receiving surface of the CCD image pickup element 1 is adjacent to the pixel on which the neutral density filter FL is formed and in the horizontal scanning direction, which will be described in detail later. The signal processing means SP is divided into minute regions each of which is formed by a pair with a pixel on which the neutral density filter FL is not formed.
Considers that the micro area receives light from the same portion of the imaging target, and outputs an image signal for the micro area.

For convenience of explanation, as shown in FIG.
Rows or rows of each pixel are numbered 1 to 8, and columns or columns are numbered a to j, and each pixel is specified and described by the row and column numbers and symbols. An electronic circuit for individually reading a signal for each pixel is integrated with the light receiving surface, and the CCD image pickup element 1 is a signal for reading a detection signal of the two-dimensional light receiving element IM and the two-dimensional light receiving element IM. It has both functions of the reading means RD. While the light from the imaging target is being imaged on the light receiving surface of the CCD image pickup device 1 by the lens 2, the CCD image pickup device 1 sequentially outputs the detection signal of each pixel from the upper left pixel to the lower right pixel. Then, the A / D converter 3 outputs the output signal and performs A / D conversion of the output signal in synchronization with the clock pulse from the clock 8. The clock pulse of the clock 8 is synchronized with the timing of sending the detection signal of each pixel of the CCD image pickup device 1. As shown in the timing chart of FIG. 3, the output of the A / D converter 3 is (1, a), (1, b), (1,
c) ……… in order of latch 4 and lookup table 5
Sent to

The latch 4 outputs the input from the A / D converter 3 with the clock pulse obtained by dividing the clock pulse of the clock 8 by the frequency dividing circuit 9. That is, as shown in FIG. 3, (1, a), (1, c),
Every other pixel in the horizontal scanning direction (1, e) ... Outputs only the signal of the pixel on which the neutral density filter FL is formed.
8-bit output of A / D converter 3 and 8 of latch 4
The output of the bit is connected to the 16-bit address input of the look-up table 5,
Outputs 8-bit data stored in the address specified by the address input to the D / A converter 6. The D / A converter 6 is supplied with the clock pulse shown at the bottom of the timing chart of FIG. 3 as a D / A conversion timing signal.

This clock pulse is input to the address of the look-up table 5 to the pixel to which the signal of the pixel in which the neutral density filter FL is formed is input from the latch 4 and to which the signal is input from the latch 4. It indicates the timing at which the signals of the pixels that are adjacent in the horizontal scanning direction, that is, the pixels for which the neutral density filter FL is not formed, are input from the A / D converter 3, and the output of the clock 8 and the frequency dividing circuit 9 is output. From the AND element 10, the inverter element 11, and the delay circuit 12. Therefore,
In the D / A converter 6, the look-up table 5 includes a signal from a pixel on which the neutral density filter FL is formed and the neutral density filter FL that is adjacent to the pixel in the horizontal scanning direction.
The data output corresponding to the signal from the pixel in which is not formed is output as an analog signal.

Next, the relationship between the address input and output data of the lookup table 5 will be described with reference to FIG. In FIG. 4, the horizontal axis represents the brightness of the light from the imaging target received by the light receiving surface of the CCD image sensor 1 on a log scale, and the vertical axis represents the 8-bit data output from the A / D converter 3. The line segment A in FIG. 4 indicates the brightness of the light received by the pixel in the non-dimming area and the detection signal of that pixel by A / D.
It shows the relationship of 8-bit data obtained by conversion,
The line segment B in FIG. 4 shows the relationship between the brightness of the light received by the pixel in the dimming area and the 8-bit data obtained by A / D converting the detection signal of the pixel.

That is, the pixels on which the neutral density filter FL is not formed have a dynamic range in the luminance range from the point p to the point q in FIG. 4, and the pixels on which the neutral density filter FL is formed are There is a dynamic range in the luminance range from point r to point s in FIG. 4, and 8-bit signals of 00 to FF are assigned within each dynamic range. The look-up table 5 is composed of 8-bit data determined by the line segment A and 8-bit data determined by the line segment B with respect to the brightness received by the CCD image pickup device 1.
8-bit data determined by the line segment C is stored at the address specified by the 6-bit address signal. Specifically, when the light having the luminance indicated by the point t is incident on the CCD image pickup device 1, the signal indicated by the point 1 is obtained by A / D converting the signal of the pixel in which the neutral density filter FL is not formed. When the signal of the pixel in which the optical filter FL is formed is A / D-converted, the data shown by the point m is obtained, but the address specified by the point 1 and the point m of the lookup table 5 has 8 bits of the point n. The data is stored.

Therefore, in the signal processing means SP, a pixel in which the neutral density filter FL is formed and a pixel which is adjacent to the pixel in the horizontal scanning direction and in which the neutral density filter FL is not formed are, for example, ( 1, a) and (1, b) or (1, c) and (1, d) are considered to receive light of the same brightness, that is, from the same portion of the imaging target. Assuming that light is being received, the detection signals of these two pixels are set to 1 as the image signals of the two pixels.
Outputs two analog signals. As is clear from FIG. 4, the analog signals output as the image signals of the two pixels have a dynamic range including a dynamic range in the dimming region and a dynamic range in the non-dimming region.

[Other Embodiments] Other embodiments will be listed below. In the above embodiment, the signal processing means SP inputs the detection signal of the dimming region and the detection signal of the non-dimming region of the two-dimensional light receiving element IM as address signals to the lookup table 5, and the dimming region and non-dimming region are input. Although an image signal having a dynamic range including both the dynamic ranges of the regions is generated, as shown in FIG. 5, as a configuration for selectively outputting the detection signal of the dimming region and the detection signal of the non-dimming region Is also good. In the block diagram shown in FIG. 5, the detection signals of the dimming region and the non-dimming region of the two-dimensional light receiving element IM are A / D converted by the A / D converter 3 as in the block diagram of FIG. Only the detection signal of the dimming area is output from the latch 4. The operation timings of the A / D converter 3 and the latch 4 are the same as those in the block diagram of FIG.

The output of the A / D converter 3 and the output of the latch 4 are switched by the switch 20 and selectively D /
It is output to the A converter 6. The switching control of the switch 20 is performed by the comparator 21, which inputs the output of the A / D converter 3 to the D / A converter 6 when the output signal from the CCD image pickup device 1 is equal to or lower than the reference voltage (Vref). If the output signal from the CCD image pickup device 1 exceeds the reference voltage (Vref), the switch 20 is switched so that the output of the latch 4 is input to the D / A converter 6. Above reference voltage (Vref)
Is set to a voltage value corresponding to a state where the two-dimensional light receiving element IM is saturated or a state immediately before the saturation. Also, D
The D / A conversion timing of the A / A converter 6 is the same as in the block diagram shown in FIG.

Therefore, the two-dimensional light receiving element IM is not saturated,
When the received light intensity of the received light from the imaging target is within the dynamic range, the detection signal of the non-dimming area is output from the D / A converter 6 as an analog signal, and the two-dimensional light receiving element IM is saturated, that is, When the non-dimmed area is saturated and the received light intensity of the received light from the imaging target exceeds the dynamic range, the detection signal of the dimmed area is output from the D / A converter 6 as an analog signal. As a result, the output of the D / A converter 6 has a dynamic range including the dynamic range of the dimming region and the non-dimming region.
In the block diagram of FIG. 5, the output of the latch 4 is added to the output of the latch 4 to correct the attenuation amount corresponding to the non-dimming region, or the output of the latch 4 is output based on the switching information of the switch 20. The output of the D / A converter 6 may be multiplied to correct the attenuation rate equivalent amount only when is output from the D / A converter 6.

In the above embodiment, the neutral density filter FL is composed of an ND filter made of a metal vapor deposition film.
As shown in FIG. 6 by extracting one pixel respectively, the non-dimming area is covered with the light shielding film 25 at the end portion of the pixel as shown in FIG. 6A, and the dimming area is as shown in FIG. The neutral density filter FL may be configured so as to be covered with the light shielding film 26 having a small opening. Alternatively, as shown in FIG. 6C, the neutral density filter FL may be configured by uniformly covering the openings of the light shielding film 25 in the peripheral portion with an ND filter made of a metal vapor deposition film.

In the above embodiment, the neutral density filter FL is composed of the ND filter, but it is not always necessary to be the ND filter and may be composed of, for example, an interference filter having a specific wavelength characteristic.

In the above embodiment, the neutral density filter FL
Is a 1-pixel wide stripe shape extending in the vertical scanning direction,
In addition, although it is formed alternately for each pixel in the horizontal scanning direction, for example, it is formed in a stripe shape having a width of one pixel extending in the horizontal scanning direction, and alternately formed for each pixel in the vertical scanning direction. The arrangement of the dimming region and the non-dimming region in the minute region which can be regarded as receiving the light from the same part of the target can be appropriately changed.

In another embodiment shown in the block diagram of FIG. 5, the switching control of the switch 20 is performed based on the detection signal itself of the CCD image pickup device 1, but a photosensor for measuring the amount of light received by the CCD image pickup device 1. May be separately provided, and the switch 20 may be controlled to be switched according to the detection value of the photo sensor.

In the above embodiment, the two-dimensional light receiving element IM
Although the case where the CCD image pickup device 1 is adopted is illustrated as an example, the image pickup tube may be used as the two-dimensional light receiving device IM.

In the above embodiment, the neutral density filter FL is formed on the light receiving surface of the CCD image sensor 1, but the glass plate on which the neutral density filter FL is formed is arranged close to the light receiving surface of the CCD image sensor 1. Also good.

It should be noted that reference numerals are given in the claims for convenience of comparison with the drawings, but the present invention is not limited to the structures of the accompanying drawings by the entry.

[Brief description of drawings]

FIG. 1 is a block diagram according to an embodiment of an image pickup apparatus of the present invention.

FIG. 2 is a schematic configuration diagram of a two-dimensional light receiving element IM according to an embodiment of the present invention.

FIG. 3 is a timing chart according to an embodiment of the present invention.

FIG. 4 is an operation explanatory diagram according to the embodiment of the present invention.

FIG. 5 is a block diagram according to another embodiment of the present invention.

FIG. 6 is a configuration diagram of a neutral density filter according to another embodiment of the present invention.

[Explanation of symbols]

 3 A / D converter 5 Look-up table FL Dimming filter IM Two-dimensional light receiving element RD Signal reading means SP signal processing means

Claims (4)

[Claims] 1. An image pickup apparatus comprising a two-dimensional light receiving element (IM) for receiving light from an image pickup target, wherein a light receiving surface of the two-dimensional light receiving element (IM) is provided from the same portion of the image pickup target. The two-dimensional light receiving element is divided into minute regions that can be regarded as receiving light, and for each divided region, a neutral density filter (FL) that attenuates the amount of light received by a part of the divided region is arranged more than other parts. In (IM), the dimming region by the dimming filter (FL) and the dimming filter (F
L), a signal reading unit (RD) capable of individually reading the detection signals of the respective non-dimmed areas which are not dimmed over the entire light-receiving surface, and the dimmed area and the non-dimmed area of the minute area to be processed. A signal for converting from a signal read by the signal reading means (RD) in the dimming region to an image signal in the minute region having a dynamic range including the dynamic range of the dimming region and the dynamic range of the non-dimming region. An imaging device provided with processing means (SP). 2. The signal processing means (SP) includes an A / D converter (3) for converting the detection signal of the dimming region and the detection signal of the non-dimming region into a digital signal, and the A / D converter. The dynamic range of the dimming region and the non-dimming region are converted into digital signals in (3), using the detection signal of the dimming region and the detection signal of the non-dimming region of the minute region to be processed as address signals. The image pickup apparatus according to claim 1, further comprising: a look-up table (5) which stores data for outputting an image signal of a minute area having a dynamic range including a dynamic range of a light area. 3. The signal processing means (SP) uses the detection signal of the non-dimming area as the image signal when the received light intensity of the non-dimming area is within the dynamic range, The image pickup apparatus according to claim 1, wherein the detection signal of the dimming area is used as the image signal when the received light intensity of the above exceeds the dynamic range. 4. The imaging device according to claim 1, 2 or 3, wherein the dimming regions and the non-dimming regions are alternately arranged along a horizontal scanning direction of the two-dimensional light receiving element (IM). .