JPH1198409A - Image detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an excellent image even from an object where an extremely bright part and an extremely dark part are in existence in mixture by generating reflection control data to set a reflection luminous quantity of a reflection means to be a prescribed value based on an electric signal from an image sensor and controlling a reflectance of the reflection means to be smaller for the bright part of the object and to be higher for the dark part of the object. SOLUTION: A video image of an object received through a lens system 100 is made incident onto a reflection type liquid crystal matrix 11 via a half mirror 101, a light reflected in the reflection type liquid crystal matrix 11 transmits through a half mirror 101 and is made incident onto an image sensor 12, where the light is converted into an image signal. A signal control section 13 calculates new reflectance data based on the image signal obtained by scanning and the reflectance data used to obtain the image signal and provides the data to the reflection type liquid crystal matrix 11. Thus, the quantity of light optimum to each area of the object is controlled and photographing at an equivalently wide dynamic range is attained.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image detecting apparatus for detecting an image of a subject, and more particularly to a technique for controlling the amount of light incident on an arbitrary area on an image sensor for each area.

[0002]

2. Description of the Related Art In an image detecting apparatus used in a conventional image pickup apparatus, a mechanical aperture mechanism is used to realize proper exposure. The aperture mechanism controls the amount of light reaching the image sensor via the optical system by continuously changing the diameter of the substantially circular hole. In recent years, an electric diaphragm mechanism has been developed which controls the amount of light reaching the image sensor via the optical system by electrically controlling the amount of light transmitted through the transmission type liquid crystal.

[0003]

However, in the conventional mechanical aperture mechanism, the light amount of the entire image is controlled. Therefore, if the exposure is performed with reference to the bright part of the subject in which the bright part and the dark part are mixed. The dark areas become darker,
The detection capability of the image sensor is exceeded. Conversely, if the exposure is performed with reference to the dark portion, the bright portion becomes even brighter, and in this case also exceeds the detection capability of the image sensor. Further, in the aperture mechanism using the transmission type liquid crystal, since the transmittance of the transmission type liquid crystal is about 40 to 50%, there is a problem that the entire image becomes dark.

In order to solve such a problem, researches and developments have been made to expand the dynamic range of an image sensor with respect to the amount of incident light, and a subject in which a bright portion and a dark portion coexist using this image sensor. Attempts have been made to obtain good images.

[0005] However, such an image sensor having an expanded dynamic range is difficult to obtain at present, and even if it is available, it is expensive. Also,
For example, when taking a bright scene outside the tunnel from a dark position inside the tunnel, or conversely, taking a dark scene inside the tunnel from a bright position outside the tunnel, an extremely bright part and extremely dark inside the subject. An image sensor having a wide dynamic range that can capture an image of both parts without crushing the image when the parts are mixed has not yet been developed. Therefore, there is a demand for an image detection device capable of shooting in a wide dynamic range despite being configured using existing image sensors.

Accordingly, the present invention is to provide an image detecting device having a wide dynamic range capable of obtaining a good image even for a subject in which an extremely bright portion and an extremely dark portion are mixed. Aim.

[0007]

In order to achieve the above object, an image detecting apparatus according to the present invention has a plurality of small sections for reflecting incident light, and the amount of reflection in each small section is reflected. A reflection unit controlled by control data, a reflection control unit for generating reflection control data to be supplied to the reflection unit, and a reflection unit whose reflection amount is controlled by reflection control data from the reflection control unit. An image sensor that converts reflected light from the small section into an electric signal; and an image signal generating unit that generates an image signal based on the electric signal from the image sensor and reflection control data from the reflection control unit. ing.

[0008] The image detecting apparatus may further include an optical system for guiding an image of the subject to the reflecting means.
The optical system includes, for example, a lens system, a mirror, and a prism for guiding an image of a subject to an image sensor.

Further, the image detecting device can be configured such that each of the plurality of small sections included in the reflection means corresponds to any one of the plurality of photoelectric conversion elements forming the image sensor. In addition, each of the plurality of small sections included in the reflection unit may be configured to correspond to two or more photoelectric conversion elements among the plurality of photoelectric conversion elements forming the image sensor.

In the above image detecting apparatus, the plurality of small sections of the reflecting means are constituted by a plurality of liquid crystal cells in which the amount of reflected light is controlled by the reflection control data.
The reflection means can be constituted by a reflection type liquid crystal matrix in which the plurality of liquid crystal cells are arranged in a matrix.

In this case, the reflection control means generates reflection control data for setting the amount of light reflected from each liquid crystal cell of the reflection means to a predetermined value based on an electric signal from the image sensor. The reflectivity of each liquid crystal cell of the reflection means can be controlled based on the reflection control data. According to this configuration, the amount of light incident on the image sensor is determined by keeping the time of reflection by the reflection unit constant and controlling only the reflectance. Therefore, if the reflecting means is controlled so that the reflectance of a bright portion of the subject is small and the reflectance of a dark portion is large, a good image can be obtained from any portion. In other words, shooting in a wide dynamic range becomes possible.

Further, the reflection control means generates reflection control data for setting the amount of reflected light from each liquid crystal cell of the reflection means to a predetermined value based on an electric signal from the image sensor. The reflection time of each liquid crystal cell can be controlled based on the reflection control data. According to this configuration, the amount of light incident on the image sensor is determined by keeping the reflectance of each liquid crystal cell constant and controlling only the reflection time of the reflection means. Therefore, if control is performed such that the reflection time of a bright part of the subject is short and the reflection time of a dark part is long, the same operation and effect as described above can be obtained.

Further, the reflection control means generates reflection control data for setting the amount of light reflected from each liquid crystal cell of the reflection means to a predetermined value based on an electric signal from the image sensor, and The means can be configured such that the reflectance of each liquid crystal cell and the reflection time of each liquid crystal cell are controlled based on the reflection control data. According to this configuration,
The amount of light incident on the image sensor is determined by controlling the reflectance and the reflection time of each liquid crystal cell. Therefore, if control is performed so that the reflectance of an extremely bright portion of the subject is small and the reflection time is short, and conversely, the reflectance of an extremely dark portion is large and the reflection time is long, a good image can be obtained from any portion. Can be obtained. In this case, it is possible to capture an image with a wider dynamic range than when only the reflectance or the reflection time is controlled.

In the above image detecting apparatus, the plurality of small sections of the reflecting means are constituted by a plurality of small mirrors whose light quantity of reflected light is controlled by the reflection control data, and the reflecting means is constituted by the plurality of small mirrors. Can be constituted by digital micromirror devices arranged in a matrix.

In this case, the reflection control means generates reflection control data for setting the amount of light reflected from each of the small mirrors of the reflection means to a predetermined value based on an electric signal from the image sensor. The reflection time of the reflection means at each small mirror can be controlled based on the reflection control data.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an image detecting device according to an embodiment of the present invention will be described. In the following, for the sake of simplicity, an image detection device that detects a monochrome image will be described. However, it is needless to say that the present invention can be applied to an image detection device that detects a color image.

(Embodiment 1) FIG. 1 shows a configuration of an image detecting apparatus according to Embodiment 1 of the present invention. This image detecting device comprises an optical system 10, a reflective liquid crystal matrix 1
1, an image sensor 12 and a signal control unit 13.

The optical system 10 includes a lens system 100 and a half mirror 101. The lens system 100 is used to form an image of a subject on the image sensor 12. The half mirror 101 is provided to guide the light from the lens system 100 to the reflective liquid crystal matrix 11 and the image sensor 12 at a substantially right angle. By providing the half mirror 101, it is possible to use the reflection type liquid crystal matrix 11 having a narrow reflection viewing angle. The “reflection viewing angle” is the same as the “viewing angle” of the transmissive liquid crystal, which is the limit angle at which an image can be viewed.
This is the limit angle at which incident light can be reflected. Therefore, if the reflective liquid crystal matrix 11 having a sufficiently wide reflection viewing angle is used, the half mirror 101 can be omitted as shown in FIG.

The image sensor 12 has m × n pixels G
_ij (i = 1, 2,..., m, j = 1, 2,... n), and each pixel is constituted by one photoelectric conversion element. Each photoelectric conversion element of the image sensor 12 is scanned at a constant period by a scanning circuit (not shown) built in the image sensor 12. In this scanning, each photoelectric conversion element outputs an analog signal having an amplitude corresponding to the amount of light incident during one scanning cycle. This analog signal is supplied to the signal control unit 13 as an image signal.

As shown in FIG. 3, the reflection type liquid crystal matrix 11 includes a liquid crystal cell array 20, a liquid crystal driving unit 21, a Y line driving unit 22, and an X line driving unit 23. The liquid crystal cell array 20 has a matrix structure of m × n liquid crystal cells S _ij , similarly to the image sensor 12. FIG. 4 is a cross-sectional view of the liquid crystal cell array 20.
The liquid crystal cell array 20 is configured by sequentially laminating a metal reflector 31 serving also as one electrode, a liquid crystal layer 32, a transparent electrode 33 constituting the other electrode, and a glass plate 34 on a glass plate 30. The amount of light transmitted through the liquid crystal layer 32 of each liquid crystal cell is controlled by the alignment direction of the liquid crystal molecules according to the applied electric field, thereby controlling the reflectance of each liquid crystal cell.

The liquid crystal drive unit 21 includes a signal control unit 1 described later.
The control signal SY and the control signal SX corresponding to the reflectance data from 3 are supplied to the Y line driving unit 22 and the X line driving unit 23, respectively. The Y line drive unit 22 selects one Y line _Yj of the liquid crystal cell array 20 according to a control signal SY from the liquid crystal drive unit 21. X-line drive unit 23
In response to a control signal SX from the liquid crystal driving unit 21, selects one X line X _i of the liquid crystal cell array 20. Thereby, one liquid crystal cell S _ij is selected. Further, the X-line drive unit 23 applies a voltage according to the control signal SX to the selected liquid crystal cell _Sij . The reflectance of the selected liquid crystal cell S _ij is controlled by the applied voltage. The above processing is sequentially performed for all the X lines and the Y lines during one scanning cycle, so that the reflectances of all the liquid crystal cells are controlled.

The liquid crystal cells S _ij included in the reflection type liquid crystal matrix 11 correspond to the pixels G _ij of the image sensor 12. Therefore, by controlling the reflectance of an arbitrary liquid crystal cell S _{ij in} the reflective liquid crystal matrix 11, the amount of light incident on the pixel G _ij in the image sensor 12 corresponding to the liquid crystal cell S _ij is controlled. You. Therefore, the amount of light of the image incident on the image sensor 12 can be controlled in pixel units.

In the image detecting apparatus described above, the liquid crystal cells in the reflection type liquid crystal matrix 11 and the pixels in the image sensor 12 correspond to each other one by one. A plurality of pixels (photoelectric conversion elements) may correspond to a cell. In an image detection device that does not need to control the amount of light incident on the image sensor 12 in pixel units, by employing such a configuration, the number of liquid crystal cells forming the reflective liquid crystal matrix 11 can be reduced. Further, it may be configured such that one row or one column of pixels corresponds to one liquid crystal cell.
According to this configuration, the configuration of the reflective liquid crystal matrix 11 is further simplified, and the configuration of the signal control unit 13 is also simplified.

The signal control section 13 corresponds to the reflection control means and the image signal generation means of the present invention. When operating as reflection control means, the signal control unit 13
The reflectance data is generated based on the image signal from the LCD, and supplied to the reflective liquid crystal matrix 11. This reflectance data corresponds to the reflection control data of the present invention. In addition, the signal control unit 13 that operates as an image signal generation unit corrects the image signal from the image sensor 12 based on the reflectance data and outputs the image signal to the outside. The signal control unit 13 will be described later in more detail.

In the image detecting apparatus configured as described above, the image of the subject captured through the lens system 100 is incident on the reflective liquid crystal matrix 11 after the optical path is changed by the half mirror 101. Then, the light reflected by the reflective liquid crystal matrix 11 is transmitted through the half mirror 101 and enters the image sensor 12. At this time, the reflectance of each liquid crystal cell of the reflective liquid crystal matrix 11 is determined according to the reflectance data generated based on the image signal obtained in the previous scan. The image sensor 12 converts the incident light into an electric signal having an amplitude corresponding to the light amount. The electric signal is extracted to the outside by the image sensor 12 being scanned, and is supplied to the signal control unit 13 as an image signal (video signal).

The signal controller 13 is based on the image signal obtained from the image sensor 12 in the current scan and the reflectance data used for obtaining the image signal (hereinafter referred to as "old reflectance data"). New reflectance data is calculated and supplied to the reflective liquid crystal matrix 11. Thereby, the reflectance of each liquid crystal cell of the reflective liquid crystal matrix 11 in the next scan is determined. Also, the signal control unit 13
Corrects the image signal obtained from the image sensor 12 in the current scan according to the old reflectance data, and outputs it as a final image signal to the outside.

Next, the details of the signal control unit 13 will be described with reference to the block diagram shown in FIG. The signal control unit 13 includes an A / D conversion unit 50, a video signal storage unit 51, a signal comparison unit 52, a reflectance information control unit 53, a reflectance information storage unit 54, and a video signal correction unit 55. The signal control unit 13 employs a pipeline system in which scanning and calculation processing of reflectance data and correction processing of a digital video signal are processed in parallel within one scanning cycle.

The A / D converter 50 converts an analog image signal sent from the image sensor 12 at regular intervals into a digital video signal. This digital video signal is supplied to the video signal storage unit 51.

The video signal storage unit 51 includes an A / D conversion unit 50
Temporarily store the digital video signal from the camera. The digital video signal stored in the video signal storage unit 51 is supplied to a signal comparison unit 52 and a video signal correction unit 55.

The signal comparing section 52 compares the digital video signal from the video signal storage section 51 with a reference signal. A signal indicating the comparison result (hereinafter, referred to as a “bright / dark signal”) is supplied to the reflectance information control unit 53. Here, the reference signal is
It is used to define a control target value of the amount of light incident on the image sensor 12, and the value can be determined as appropriate. The light / dark signal is composed of a difference value between the digital video signal and the reference signal. The light / dark signal is composed of a positive difference value (including zero) when the digital video signal is equal to or larger than the reference signal, and a negative difference value when the digital video signal is smaller than the reference signal.

The reflectance information control unit 53 includes a signal comparing unit 52
Liquid crystal matrix 11 based on the light / dark signal from the camera and the reflectance data stored in the reflectance information storage unit 54.
The reflectance data for determining the reflectance of each liquid crystal cell is generated. For example, the reflectance information control unit 53 generates reflectance data that reduces the reflectance when the light-dark signal has a positive difference value, and generates the reflectance data when the brightness signal has a negative difference value.
Generates reflectance data that increases the reflectance. The reflectance data generated by the reflectance information control unit 53 is supplied to a reflectance information storage unit 54.

The reflectance information storage unit 54 stores the reflectance data calculated by the reflectance information control unit 53. The reflectance data stored in the reflectance information storage unit 54 is supplied to the reflective liquid crystal matrix 11 (see FIGS. 1 and 2), and is also supplied to the video signal correction unit 55 as old reflectance data.

The video signal correction unit 55 includes a video signal storage unit 5
A final image signal is generated by calculating the digital video signal from the unit 1 and the reflectance data from the reflectance information storage unit 54. The above processing is sequentially performed on the image signals corresponding to each pixel sequentially obtained from the image sensor 12. Thereby, the reflection type liquid crystal matrix 11
Therefore, an image signal in which the brightness of each area of the image is adjusted is output from this image detection device.

In order to deepen the understanding of the operation of the image detecting apparatus, further explanation will be given below using specific numerical values. Generally, it is difficult to make the reflectivity of each liquid crystal cell of the reflective liquid crystal matrix 11 variable in the range of 0 to 100%.
Therefore, in the following, it is assumed that the reflectivity can be changed in the range of 10 to 70%. Note that, for example, “reflectance 20%” means that 20% of the incident light amount is reflected. As the reflectance data, a percentage representing the reflectance is used as it is.

Assuming that the control target value of the illuminance on the image sensor 12 is 10 lux (lx) as the reference signal in the signal comparing section 52, 10
The voltage generated when lux light is applied is adopted.

Now, when light of 20 lux is incident on the image sensor 12, the signal comparing section 52 generates a light / dark signal having a positive difference value and supplies it to the reflectance information control section 53.
The reflectance information control unit 53 generates reflectance data such that the reflectance of the reflective liquid crystal matrix 11 becomes 50% of the current reflectance based on the light / dark signal. This is obtained by multiplying the reflectance data currently stored in the reflectance information storage unit 54 by 0.5. The new reflectance data thus calculated is stored in the reflectance information storage unit 54. Thus, in the next scan,
Light of 10 lux, which is a control target value, is incident on the image sensor 12.

By performing the above processing for all the pixels of the image sensor 12, the entire area of the image sensor 12 is irradiated with light of 10 lux as a control target. Even if the subject is changed, the above-described operation is performed in each scanning cycle, so that the entire area of the image sensor 12 is controlled to always emit 10 lux of light as a control target.

On the other hand, the video signal correction unit 55 multiplies the digital video signal from the video signal storage unit 51 by the reciprocal of the reflectance data from the reflectance information storage unit 54. As a result, if the amount of light incident on the image sensor 12 is the control target value, the amount of light actually incident on the image detection device is obtained. The signal corresponding to the obtained light quantity is
The image signal is output to the outside as an image signal.

When the light quantity incident on the image sensor 12 is small and does not reach the control target value even at the maximum reflectance of 70%, or when the light quantity incident on the image sensor 12 is large and the minimum reflectance is 10%, the control target value is not obtained. Even when the value exceeds the value, the amount of light actually incident on the image detection apparatus can be obtained by multiplying the amount of light incident on the image sensor 12 by the reciprocal of the reflectance data. That is, when a reflectance exceeding the lower limit (10%) or the upper limit (70%) is required, an image having a fixed reflectance is obtained.

If the sensitivity (dynamic range) required in a system using this image detection device is predetermined, the reflectance information control unit 53 controls the reflectance within a predetermined range. This can be handled by configuring.

The signal controller 13 controls the light quantity incident on the image sensor 12 based on the reflectance data from the reflectance information controller 53 so that the amount of light incident on the image sensor 12 is constant. The video signal always has a constant value. This means that the reflectance data itself represents an image of the subject. Therefore, the reflectance data itself from the reflectance information control unit 53 can be used as an image signal, and in this case, the video signal correction unit 55 can be omitted.

In the above-described image detection device, the reflectance data stored in the reflectance information storage unit 54 is updated every scan cycle by the data calculated by the reflectance information control unit 53. However, the content of the reflectance information storage unit 54 may be arbitrarily updated from outside the signal control unit 13.

(Embodiment 2) In the image detection apparatus according to Embodiment 1 described above, the amount of light reflected by the reflective liquid crystal matrix is controlled by controlling the reflectivity. The image detection device according to No. 2 controls the effective reflection light amount by controlling the reflection time in the reflection type liquid crystal matrix.

The configuration of the image detection device according to the second embodiment of the present invention is substantially the same as the configuration of the image detection device according to the first embodiment (see FIGS. 1 and 2). Therefore, only the differences will be described below.

In FIG. 1 and FIG.
Outputs the “reflectance data” for determining the reflectivity of each liquid crystal cell of the reflective liquid crystal matrix 11 in the first embodiment, whereas the second embodiment outputs each liquid crystal of the reflective liquid crystal matrix 11 in the second embodiment. “Reflection time data” for determining the reflection time in the cell is output.

In the first embodiment, the reflection type liquid crystal matrix 11 transmits reflected light during one scanning cycle to the image sensor 12.
Continue to irradiate the photoelectric conversion element inside. On the other hand, in the second embodiment, the time during which the reflected light from the reflective liquid crystal matrix 11 irradiates the photoelectric conversion elements in the image sensor 12 is variable within one scanning cycle. Reflective liquid crystal matrix 1
The configuration of the first embodiment is the same as that of the first embodiment (see FIG. 3), but the operations of the liquid crystal drive unit 21 and the X-line drive unit 23 are different from those of the first embodiment in order to realize the above functions.

That is, the liquid crystal driving section 21 is
The control signal SY and the control signal SX corresponding to the reflection time data from the XY line driving unit 22 are supplied to the Y line driving unit 22 and the X line driving unit 23, respectively. The selection of one Y line _Yj of the liquid crystal cell array 20 according to the control signal SY from the liquid crystal drive unit 21 is the same as that of the first embodiment. The X-line driving unit 23 includes the liquid crystal driving unit 2
In response to a control signal SX from 1 selects one of the X lines X _i of the liquid crystal cell array 20. Thereby, one liquid crystal cell S _ij is selected. Also, the X-line driving unit 23
Is applied to the liquid crystal cell S _ij of the voltage for the maximum (e.g., 70%) was the selected reflectance of only the liquid crystal cell time in accordance with the control signal SX, then the minimum reflectance of the liquid crystal cell (for example 10 %). This allows
The selected liquid crystal cell S _ij reflects the incident light for a time corresponding to the reflection time data. The above processing is sequentially performed for all the X lines and the Y lines during one scanning cycle, so that the reflection time in all the liquid crystal cells is controlled.

By controlling the reflection time at an arbitrary liquid crystal cell S _ij in the reflective liquid crystal matrix 11, the amount of light incident on the pixel G _ij in the image sensor 12 corresponding to the liquid crystal cell S _ij can be reduced. Controlled. Therefore,
The amount of light of an image incident on the image sensor 12 can be controlled in pixel units.

The signal control section 13 corresponds to the reflection control means and the image signal generation means of the present invention. When operating as reflection control means, the signal control unit 13
Generate reflection time data based on the image signal from
It is supplied to the reflective liquid crystal matrix 11. This reflection time data corresponds to the reflection control data of the present invention. In addition, the signal control unit 13 operates as an image signal generation unit.
Corrects the image signal from the image sensor 12 based on the reflection time data, and outputs it as an image signal to the outside. The signal control unit 13 will be described later in more detail.

In the image detecting device configured as described above, the image of the subject captured through the optical system 10 is incident on the reflective liquid crystal matrix 11. At this time, the reflection time of each liquid crystal cell of the reflection type liquid crystal matrix 11 is determined according to the reflection time data generated based on the image signal obtained in the previous scan. Then, the light reflected by the reflection type liquid crystal matrix 11 enters the image sensor 12. Image sensor 12
Converts the incident light into an electric signal having an amplitude corresponding to the light amount. This signal is extracted to the outside by the image sensor 12 being scanned, and is supplied to the signal control unit 13 as an image signal (video signal).

The signal control unit 13 is based on the image signal obtained from the image sensor 12 in the current scan and the reflection time data used for obtaining the image signal (hereinafter referred to as “old reflection time data”). New reflection time data is calculated and supplied to the reflection type liquid crystal matrix 11. Thereby, the reflection type liquid crystal matrix 1 in the next scan is
The reflection time of each liquid crystal cell is determined. Also,
The signal control unit 13 corrects the image signal obtained from the image sensor 12 in the current scan according to the old reflection time data, and outputs the corrected image signal to the outside as a final image signal.

Next, the details of the signal control unit 13 will be described with reference to the block diagram shown in FIG. In the signal control unit 13 according to the second embodiment, a reflection time information control unit 63 is used instead of the reflectance information control unit 53 according to the first embodiment.
However, a reflection time information storage unit 64 is provided instead of the reflectance information storage unit 54. Embodiment 1
The same or corresponding parts are denoted by the same reference characters, and description thereof will be omitted or simplified.

The reflection time information control unit 63 includes the signal comparing unit 5
Then, reflection time data for determining the reflection time in each liquid crystal cell of the reflection type liquid crystal matrix 11 is generated based on the light / dark signal from 2 and the reflection time data stored in the reflection time information storage unit 64. The reflection time information control unit 63 generates, for example, reflection time data that shortens the reflection time when the light / dark signal has a positive difference value, and lengthens the reflection time when it has a negative difference value. Such reflection time data is generated. The reflection time data generated by the reflection time information control unit 63 is supplied to the reflection time information storage unit 64.

The reflection time information storage unit 64 stores the reflection time data calculated by the reflection time information control unit 63. The reflection time data stored in the reflection time information storage section 64 is supplied to the reflection type liquid crystal matrix 11 (see FIGS. 1 and 2) and is also supplied to the video signal correction section 55 as old reflection time data.

The video signal correction unit 55 includes a video signal storage unit 5
A final image signal is generated by calculating the digital video signal from the unit 1 and the reflection time data from the reflection time information storage unit 64. The above processing is performed by the image sensor 12.
Are sequentially performed on the image signals corresponding to the respective pixels sequentially obtained from. As a result, an image signal in which the brightness of each area of the image is adjusted by the reflective liquid crystal matrix 11 is output from the image detection device.

The operation will be further described below using specific numerical values. As in the first embodiment, the maximum reflectance of each liquid crystal cell of the reflective liquid crystal matrix 11 is 70%, and the minimum reflectance is 10%. As the reflection time data, the time of reflection at the maximum reflectance is used.

As a reference signal in the signal comparing section 52, assuming that the control target value of the amount of light on the image sensor 12 is 10 lumen seconds (lm · s), a light beam of 10 lumen enters the photoelectric conversion element for 1 second. In this case, the voltage generated when the power is turned on is adopted.

Now, when a light quantity of 20 lumen seconds is incident on the image sensor 12, the signal comparing section 52 generates a light / dark signal having a positive difference value and supplies it to the reflection time information control section 63. The reflection time information control unit 63 generates reflection time data such that the reflection time in the reflection type liquid crystal matrix 11 becomes 50% of the current reflection time based on the light / dark signal. This is obtained by multiplying the reflection time data currently stored in the reflection time information storage unit 64 by 0.5. The new reflection time data calculated in this way is stored in the reflection time information storage unit 64. Thus, in the next scan, a light flux of 10 lumen seconds, which is the control target value, is incident on the image sensor 12.

By performing the above processing for all the pixels of the image sensor 12, light of 10 lumen seconds, which is a control target, is incident on the entire area of the image sensor 12. Even if the subject is changed, the above-described operation is performed for each scanning cycle, so that the entire area of the image sensor 12 is controlled so that a light flux of 10 lumen seconds, which is a control target, is incident.

On the other hand, the video signal correction section 55 multiplies the digital video signal from the video signal storage section 51 by the reciprocal of the reflection time data from the reflection time information storage section 64. As a result, if the amount of light incident on the image sensor 12 is the control target value, the amount of light actually incident on the image detection device is obtained. A signal corresponding to the obtained light amount is output from the image detection device to the outside as an image signal.

When the amount of light incident on the image sensor 12 is small and does not reach the control target value even with the maximum reflection time, or when the amount of light incident on the image sensor 12 is large and the minimum reflection time is reached, Even when the value exceeds the value, the amount of light actually incident on the image detecting apparatus can be obtained by multiplying the amount of light incident on the image sensor 12 by the reciprocal of the reflection time data. That is, when a reflection time exceeding the lower limit or the upper limit is required, the reflected light is reflected by the image sensor 12.
An image in which the time of incidence (reflection time) on the image is fixed is obtained.

As described above, in the second embodiment, the reflection type liquid crystal matrix 11 is used as the reflection means. Instead of this reflection type liquid crystal matrix 11, a small mirror manufactured by a micromachine technology is integrated. DM
D (digital micromirror device) can be used.
This DMD is constituted by a large number of small mirrors formed on a semiconductor substrate by a micromachine process. Each mirror is formed on a spring, and the on / off of light is controlled by tilting the mirror by static electricity.

When the sensitivity (dynamic range) required in a system using this image detecting device is predetermined, the reflection time is controlled by the reflection time information control unit 63 within a predetermined range. This can be handled by configuring.

The signal control unit 13 is controlled by the reflection time data from the reflection time information control unit 63 so that the amount of light incident on the image sensor 12 is constant. The video signal always has a constant value. This means that the reflection time data itself represents an image of the subject. Therefore, the reflection time data itself from the reflection time information control unit 63 can be used as an image signal. In this case, the video signal correction unit 55 can be omitted.

In the above-described image detecting device, the reflection time data stored in the reflection time information storage unit 64 is
1 according to the data calculated by the reflection time information control unit 63
Although the configuration is updated every scanning cycle, the signal control unit 13
May be configured to arbitrarily update the contents of the reflection time information storage unit 64 from outside.

In the first embodiment, the amount of light incident on the image sensor 12 is controlled by controlling the reflectance of the liquid crystal cell of the reflective liquid crystal matrix 11.
In the second embodiment, the amount of light incident on the image sensor 12 is controlled by controlling the reflection time of the reflective liquid crystal matrix 11 in the liquid crystal cell.
The configuration may be such that the amount of light incident on the image sensor is controlled by both the reflectance and the reflection time of the liquid crystal cell. In this case, since the amount of light incident on the image sensor 12 can be varied in a large range, the dynamic range of the image sensor with respect to the amount of incident light can be further expanded as compared with the first and second embodiments.

By configuring the image detecting device as described above, for example, when photographing a bright scene outside the tunnel from a dark position inside the tunnel, or conversely, photographing a dark scene inside the tunnel from a bright position outside the tunnel. Even when the subject contains extremely bright and extremely dark parts, the optimal light intensity control can be performed for each area of the subject. Shooting becomes possible. The increment of the dynamic range is 48 dB if the gradation of the reflection type liquid crystal matrix 11 is controlled by 8 bits.
Assuming that the dynamic range of No. 2 is 60 dB, a dynamic range of 108 dB can be realized in total.

Although the image detecting apparatus for detecting a monochrome image has been described above, the present invention can be applied to an image detecting apparatus for detecting a color image. In this case, a reflective liquid crystal matrix in which a color filter 35 is provided between a transparent electrode 33 and a glass plate 34 as shown in FIG. 7 is used. Then, one pixel is formed by the photoelectric conversion elements in the image sensor 12 corresponding to one set of R, G, and B. In this case, since the amount of light incident on each photoelectric conversion element forming a pixel is controlled, it is possible to obtain a good color image even for a subject in which an extremely bright part and an extremely dark part are mixed, for example. Can be.

Further, in the image detection devices according to the first and second embodiments, the reflectance is higher than the transmittance of the transmissive liquid crystal cell in order to control the amount of light incident on the image sensor. The adoption of a much larger reflective liquid crystal cell or DMD solves the problem that the entire image generated when a transmissive liquid crystal is used becomes dark.

[0070]

As described in detail above, according to the present invention,
For example, it is possible to provide an image detection device having a wide dynamic range capable of obtaining a good image even for a subject in which an extremely bright portion and an extremely dark portion are mixed.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of an image detection device according to Embodiments 1 and 2 of the present invention.

FIG. 2 is a diagram showing a configuration of a modification of the image detection device according to the first and second embodiments of the present invention.

FIG. 3 is a diagram illustrating a configuration of a reflective liquid crystal matrix used in the image detection devices according to the first and second embodiments of the present invention.

FIG. 4 is a cross-sectional view showing a configuration of a liquid crystal cell array of a monochrome reflective liquid crystal matrix used in the image detection devices according to Embodiments 1 and 2 of the present invention.

FIG. 5 is a block diagram illustrating a configuration of a signal control unit used in the image detection device according to the first embodiment of the present invention.

FIG. 6 is a block diagram illustrating a configuration of a signal control unit used in an image detection device according to a second embodiment of the present invention.

FIG. 7 is a cross-sectional view showing a configuration of a liquid crystal cell array of a reflective liquid crystal matrix for color used in the image detection device according to the embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 10 optical system 11 reflective liquid crystal matrix 12 image sensor 13 signal control unit 50 A / D conversion unit 51 video signal storage unit 52 signal comparison unit 53 reflectance information control unit 54 reflectance information storage unit 55 video signal correction unit 63 reflection time Information control unit 64 Reflection time information storage unit 100 Lens system 101 Half mirror

Claims (10)

[Claims] A plurality of sub-sections for reflecting incident light; a reflection section for controlling the amount of reflection in each sub-section according to reflection control data; and a reflection control section for supplying the reflection section to the reflection section. Reflection control means for generating data; an image sensor for converting reflected light from each subsection of the reflection means, the reflection amount of which is controlled by the reflection control data from the reflection control means, to an electric signal; and An image signal generating means for generating an image signal based on the electric signal of (1) and reflection control data from the reflection control means. 2. The image detecting apparatus according to claim 1, further comprising an optical system for guiding an image of a subject to said reflection means. 3. The image detection device according to claim 1, wherein each of the plurality of small sections included in the reflection means corresponds to any one of a plurality of photoelectric conversion elements forming the image sensor. apparatus. 4. The method according to claim 1, wherein each of the plurality of small sections included in the reflection unit corresponds to two or more photoelectric conversion elements among the plurality of photoelectric conversion elements forming the image sensor. The image detection device according to claim 1. 5. A plurality of sub-sections of said reflecting means are composed of a plurality of liquid crystal cells of which the amount of reflected light is controlled by said reflection control data, and said reflecting means has a plurality of liquid crystal cells arranged in a matrix. The image detection device according to claim 1, wherein the image detection device includes a reflection type liquid crystal matrix. 6. The reflection control means generates reflection control data for setting the amount of light reflected from each liquid crystal cell of the reflection means to a predetermined value based on an electric signal from the image sensor. 6. The image detection device according to claim 5, wherein the reflectance of each liquid crystal cell of the means is controlled based on the reflection control data. 7. The reflection control means generates reflection control data for setting the amount of light reflected from each liquid crystal cell of the reflection means to a predetermined value based on an electric signal from the image sensor. 6. The image detecting device according to claim 5, wherein a reflection time of each liquid crystal cell of the means is controlled based on the reflection control data. 8. The reflection control means generates reflection control data for setting the amount of reflected light from each liquid crystal cell of the reflection means to a predetermined value based on an electric signal from the image sensor. 6. The image detecting apparatus according to claim 5, wherein the reflectance of each liquid crystal cell and the reflection time of each liquid crystal cell are controlled based on the reflection control data. 9. A plurality of small sections of said reflecting means are constituted by a plurality of small mirrors whose light quantity of reflected light is controlled by said reflection control data, and said reflecting means comprises a plurality of said small mirrors arranged in a matrix. The image detection device according to claim 1, wherein the image detection device is a digital micromirror device. 10. The reflection control means generates reflection control data for setting the amount of light reflected from each of the small mirrors of the reflection means to a predetermined value based on an electric signal from the image sensor. 10. The image detecting apparatus according to claim 9, wherein a reflection time of each of the small mirrors of the means is controlled based on the reflection control data.