JPH1188757A - Extinction filter, night vision device provided with extinction filter and halation preventing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an extinction filter attenuating only the light of not less than prescribed illuminance and transmitting fine light without attenuating it when an optical image containing strong light is made incident. SOLUTION: The extinction filter 10 is constituted by arranging extinction filter cells being plural fine areas. Optical sensor circuits 22 for detecting the illuminance of light which is made incident on liquid crystal cells 14a are arranged for the respective liquid crystal cells 14a. When light with the illuminance of not less than a prescribed value is made incident on the optical sensor circuit 22, only the liquid crystal cell 14a is driven and only light with the illuminance of not less than the prescribed value is attenuated. The light of not more than the prescribed value is made to pass without attenuating it.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a dimming filter, a night vision apparatus having the dimming filter, and a method for preventing halation, and more particularly to a dimming filter for adjusting illuminance when an optical image including a light spot having a predetermined illuminance or more is incident. The present invention relates to an optical filter, a night vision device for preventing halation by using the neutral density filter, and a halation prevention method.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 11, a weak light radiated from a target is incident, and the light is amplified several hundred times to several thousand times to form a clear optical image on a monitor screen. Is known. This night vision device 100
Is used in various fields such as monitoring the target in an environment where it is difficult to recognize or identify the target at night or the like, and observing stars and nocturnal creatures.

As shown in FIG. 11, an image intensifier 10 is used as a photodetector in the night-vision apparatus 100.
2 and the like, and weak light radiated from a target 104 (for example, a night lighthouse, a search light, a navigation light, etc.) is transmitted through the optical lens system 106 to the image intensifier 1.
02. The image intensifier 102 includes a fiber plate 102a having a photocathode on the rear surface, an electron lens system 102b, a photomultiplier tube (microchannel plate; MCP) 102c, a fiber plate 102d having a phosphor screen, and the like. The optical image amplified by the intensifier 102 is photographed by an imaging device 108 such as a CCD device disposed on the rear surface of the fiber plate 102d, and is displayed on a monitor 110 or the like as a clear image.

[0004]

However, since the night vision device 100 amplifies the acquired light several hundred times to several thousand times, as shown in FIG. If the light includes light of a brightness or higher, for example, if light from a lighthouse is directly incident at night, the monitor 110 of the night-vision device may be used.
On the upper part, a saturated image in which the part emitting the strong light is light-saturated is displayed. In addition, this light saturation outputs a similar light-saturated image 112 not only in a portion that emits strong light but also in a considerably wide area around the portion. As a result, it becomes impossible to observe the light-saturated portion.
This phenomenon is called halation, and the video information of the video signal in the part where the phenomenon occurs is completely destroyed. Therefore, there is a problem that a video erased by halation cannot be reproduced even if any image processing is performed.

If only halation is to be avoided,
The gain of the image intensifier 102 may be reduced, but there is a problem in that the incident light from a portion where other light is weak (a dark portion) also decreases, and an optical image cannot be output due to insufficient incident light. Furthermore, it is also conceivable to use a filter that detects that a certain amount of light or more is incident and attenuates the incident light. However, as described above, the state is the same as the state where the gain of the image intensifier 102 is lowered, and a favorable state is obtained. An output image cannot be obtained and observation becomes impossible.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and has a simple configuration even when an optical image of a target including strong light is obtained. A dimming filter that can be attenuated below, and a dimming filter that can obtain optical images of other dark portions without causing halation even when an optical image of a target including strong light is incident. It is an object of the present invention to provide a night vision device and a halation prevention method provided.

[0007]

In order to achieve the above object, the structure of the neutral density filter according to the present invention is to receive each light spot constituting an optical image and form an optical image receiving surface as a whole. A plurality of fine regions, and an optical sensor arranged in each of the fine regions and detecting the illuminance of light incident on the fine regions,
A variable transmission member that is arranged in each micro area and changes the light transmittance of the micro area to attenuate the illuminance of the transmitted light when the corresponding optical sensor detects light of a predetermined illuminance or more, including: The light transmittance is adjusted.

[0010] According to this configuration, incident light is detected for each of a plurality of fine regions constituting the optical image light receiving surface, and only when light having a predetermined illuminance or more (light having a certain brightness or more) is detected, a corresponding operation is performed. The illuminance of transmitted light is attenuated by adjusting only the light transmittance of the minute region to be transmitted. On the other hand, light weaker than the predetermined illuminance is transmitted without forcible attenuation. As a result, only strong light can be reliably attenuated and converted to an optical image having a certain illuminance or less.

In order to achieve the above object, the fine regions of the neutral density filter according to the present invention are characterized in that they are arranged in a matrix and form an optical image receiving surface.

[0010] According to this configuration, the wiring of the fine optical sensor and the variable transmission member arranged in each of the fine regions can be easily arranged, and the neutral density filter can be manufactured at low cost.

In order to achieve the above object, the variable transmission member of the light source filter is constituted by a liquid crystal layer.

According to this structure, the phase state of the liquid crystal is changed by changing the voltage supplied to the liquid crystal according to the output from the optical sensor, and the light transmittance can be easily adjusted for each fine region. Will be possible.

To achieve the above object, a neutral density filter for attenuating the illuminance of an incident optical image by a predetermined amount,
A photoelectric surface that converts an optical image that has passed through the neutral density filter into a photoelectron image, an electron multiplier that multiplies the electron group of the photoelectron image, and a phosphor screen that generates an amplified optical image from the multiplied electron group. An imaging device that captures the amplified optical image, wherein the darkening filter is the above-described darkening filter, and adjusts light transmittance for each fine region to prevent halation. Features.

According to this structure, the halation can be reliably prevented by merely attaching the above-described neutral density filter to the conventional device, and the gain of the other light weak portion can be secured. A clear and good optical image can be easily obtained.

In order to achieve the above object, each light spot constituting an incident optical image is individually received in a plurality of fine areas, and the illuminance of each light spot is individually detected, and each fine light spot is detected. When the illuminance of the light spot received by the area is equal to or greater than a predetermined illuminance, the light transmittance of the liquid crystal layer in the minute area where the light spot is incident is individually attenuated based on the detected illuminance of the light spot, and the imaging of the night-vision device is performed. The illuminance of the light spot reaching the element is adjusted to a predetermined value or less to prevent halation.

According to this configuration, halation is prevented from occurring on the optical image of the target including a strong light portion.
It is possible to secure the gain of other light weak parts.

[0017]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention (hereinafter referred to as embodiments) will be described below with reference to the drawings.

FIG. 1 shows a neutral density filter 10 according to the present embodiment.
Is shown with night vision device 12. The other parts of the night-vision device 12 except for the neutral density filter 10 have the same configuration as the conventional night-vision device 100 shown in FIG. 11, and therefore, the same members are denoted by the same reference numerals and description thereof will be omitted. .

The characteristic feature of the present embodiment is that the neutral density filter 10 is provided on the front surface of the image intensifier 102, that is, the portion where the incident light forms an optical image by the optical lens system 106 (a form different from that of FIG. 11). The characteristic of the neutral density filter is that it detects the incident illuminance at each point in the incident area with an area, and attenuates only the strong light (part of the predetermined illuminance or more). I have it.

As shown in FIG. 1, light emitted from a target (a lighthouse in this embodiment) 104 is transmitted to an optical lens system 106.
Is supplied to the neutral density filter 10. In the neutral density filter 10, the transmittance of a portion including light having a predetermined illuminance or higher is selectively reduced, and attenuated to a predetermined value or lower. The optical image whose upper limit illuminance has been limited by the neutral density filter 10 is amplified in a photoelectron image state by an image intensifier 102, converted into an optical image again, photographed by an image sensor 108 such as a CCD, and Is output. In this case, light of a predetermined illuminance or more of the light of the optical image that has passed through the optical lens system 106 is restricted by the neutral density filter 10 before being supplied to the image intensifier 102, so that the image intensifier 102
Is supplied only with light weaker than a predetermined illuminance, the image intensifier 102 performs an amplifying operation within the allowable capacity to prevent halation, and the originally weak light constituting the optical image is filtered by a neutral density filter. Because it passes without forced attenuation at 10,
Amplification is performed in the image intensifier 102 as before.

FIG. 2 is a schematic diagram showing the overall configuration of the neutral density filter 10. The neutral density filter 10 includes:
For example, it has a five-layer structure in which indium oxide films (ITO films) 16a and 16b are arranged on both sides of a liquid crystal layer 14 as a variable transmission member, and these are sandwiched between glass substrates 18a and 18b. The liquid crystal layer 14, as shown in FIG.
A plurality of 12 μm × 20 μm fine regions 20 (hereinafter referred to as dimming filter cells 20) are arranged in a matrix. The neutral density filter cell 20 includes a liquid crystal cell 14a and an optical sensor circuit 22 for controlling the liquid crystal cell 14a. In other words, the ITO
The films 16a and 16b are transparent electrodes, and the light attenuating filter cell 20 is passed through the ITO film 16a on the light incident surface side.
The optical sensor circuit 22 provided for each of the optical sensor circuits 22 can recognize the incident light for each of the neutral density filter cells 20. As a result, the potential of the ITO film 16a on the light incident surface side is determined by the incident light, a voltage corresponding to the intensity of the incident light is applied to each liquid crystal cell 14a, and the liquid phase changes in each liquid crystal cell 14a. And the light transmittance is determined. That is, the attenuation of the passing light is determined.

FIG. 4A shows an equivalent circuit for explaining the configuration of the neutral density filter cell 20 constituting the neutral density filter 10. One neutral density filter cell 20 includes the optical sensor circuit 22 and the liquid crystal. And a cell 14a. In the present embodiment, it is assumed that an AC voltage is applied to each liquid crystal cell 14a to perform phase change. Therefore, the optical sensor circuit 22 is composed of two photodiodes 22a that allow current flows in different directions. The photodiode 22a is, for example, a PIN junction or a PN
Joints are preferred. In addition, the photodiode 2
A resistor 22b for preventing overcurrent is connected in series to 2a. Further, a driving power source 24 for the liquid crystal cell is connected to the liquid crystal cell 14a via the optical sensor circuit 22, and a voltage is applied to the liquid crystal cell 14a according to the amount of light received by the photodiode 22a.

FIG. 4B shows an example of an equivalent circuit when the neutral density filter 10 is configured by arranging the equivalent circuit of FIG. 4A in a matrix in correspondence with FIG. In this case, a liquid crystal cell driving power supply 24 for supplying a voltage to each liquid crystal cell 14a is shared, and each is connected by a thin film metal electrode 26. The ground is connected to the IT on the light transmitting surface side of each liquid crystal cell 14a.
The O. film 16b is used. In FIG. 4B, only one photodiode is shown for the optical sensor circuit 22 to simplify the drawing.

As shown in FIG. 4C, when the incident illuminance E exceeds a predetermined illuminance, that is, the limit incident illuminance (Eth) which causes halation, the light sensor circuit 22 rapidly applies the light to the liquid crystal cell 14a. It has a characteristic that the voltage is increased, the phase transition of the liquid phase is performed, and the attenuation L of the transmitted light transmitted through the liquid crystal cell 14a is increased.

FIG. 5 is an enlarged view of FIG. 3 and shows the liquid crystal cell 14a and the optical sensor circuit 22 from the light incident surface side via the glass substrate 18a and the ITO film 16a. FIG.
As described in the equivalent circuit of (b), each liquid crystal cell 14a
The thin film metal electrode 26 is disposed around the liquid crystal cell 14a, is connected to the optical sensor circuit 22 disposed in a part of each liquid crystal cell 14a, and is connected to the liquid crystal cell driving power supply 24 shown in FIG. I have. Further, the ITO film 16b on the light transmitting surface side is connected to the driving power supply 24 for the liquid crystal cell.

As shown in FIG. 13, when an optical image including strong light is incident on a lighthouse or the like as shown in FIG. 13, the actual incident illuminance recognized by one horizontal scanning line at an arbitrary timing is as follows. For example, as shown in FIG. 6A, there is a variety depending on the screen position, and a portion exceeding the limit incident illuminance Eth (screen positions D and E) is also included. The aforementioned neutral density filter 10
In the case of the night vision device 12 provided with
When the light sensor circuit 22 disposed on the LCD receives light exceeding the limit incident illuminance Eth, a voltage corresponding to the received illuminance is applied to each liquid crystal cell 14a, and the amount of light reduction is determined. FIG. 6B shows the filter attenuation at screen positions D and E exceeding the limit incident illuminance Eth. As a result, the light transmitted through the neutral density filter 10 is as shown in FIG.
As shown in (1), only the illuminance at the screen positions D and E exceeding the limit incident illuminance Eth is corrected to be equal to or less than the limit incident illuminance Eth. Therefore, in this state, when light enters the image intensifier 102 (see FIG. 1), the light at the screen positions A, B, and C is multiplied and output as usual, and only the light at the image positions D and E is output. Is multiplied to the maximum value that does not cause halation.

FIG. 7 is a schematic diagram showing the relationship between incident light and outgoing light with respect to the neutral density filter 10. In the figure, the light emitted from the light sources A to E indicates that the thicker the arrow, the stronger the light. The light from the light sources D and E is the above-mentioned limit incident illuminance E
th, and is attenuated below the limit incident illuminance Eth by passing through the neutral density filter 10.
Since the light from the light sources A to C is originally less than the limit incident illuminance Eth, the light sensor circuit 22 does not react,
The liquid crystal cell 14a emits the incident light without attenuating it without performing a phase transition.

As described above, the illuminance of light incident on the corresponding liquid crystal cell 14a is detected by the optical sensor circuit 22 arranged for each liquid crystal cell 14a of the neutral density filter cell 20 which is a fine region, and the illuminance is applied to the liquid crystal cell 14a. By changing the applied voltage and adjusting the transmittance of the liquid crystal cell 14a, only light exceeding the limit incident illuminance Eth is attenuated, and other weak light is transmitted without being attenuated. Halation can be prevented by preventing light having a luminous intensity exceeding the limit incident illuminance from being incident on the image intensifier 102. In addition, since the light below the limit incident illuminance is multiplied as usual by the image intensifier 102, a clear night vision image can be obtained.

FIGS. 8A and 8B show another configuration example of the optical sensor circuit. An optical sensor circuit 28 disposed between the liquid crystal cell 14a and the liquid crystal cell drive power supply 24 includes:
It is composed of one photodiode 28a and one thin film transistor (TFT). The TFT 28
b is usually used for driving a liquid crystal display, and the T.b.
The photodiode 28a is connected to the gate electrode of the FT 28b to perform the same operation as that of the optical sensor circuit 22 described above. When a configuration using the TFT 28b is adopted, a DC power supply 30 is separately required. Further, similarly to the optical sensor circuit 22, the photodiode 28
The resistor a for overcurrent prevention is connected to a.

FIG. 9 is an explanatory diagram showing the liquid crystal cell 14a and the light sensor circuit 28 of the neutral density filter 10 when the light sensor circuit 28 is employed. In this case, as in FIG.
Thin-film metal electrodes 26a and 26b are arranged around each liquid crystal cell, and supply a voltage from the liquid crystal cell drive power supply 2 and the DC power supply 30. In this case, the ground is also
The ITO film 16b on the light transmitting surface side of each liquid crystal cell 14a (FIG. 2)
See).

As described above, the conventional liquid crystal display device (LC
By simply adding a photodiode to the liquid crystal cell with a thin film transistor used in D.), a neutral density filter capable of preventing halation can be easily formed.

FIG. 10 shows a configuration example of a liquid crystal cell used in the present embodiment. FIG. 10A shows TN (Twist Nemat).
An ic) type liquid crystal cell 32 is used, and is operated by being sandwiched between two polarizers (plates) 34a and 34b perpendicular to the polarization direction. In the state (a-1) where no voltage is applied,
The incident light of linearly polarized light passing through the polarizer 34a passes through the TN type liquid crystal cell 32, and is transmitted along the torsion of the liquid crystal molecules.
(Deg.) Optical rotation. Therefore, the light is transmitted to the second polarizer 34b.
Can be transmitted. On the other hand, in the state (a-2) where a certain voltage is applied, most of the liquid crystal molecules are arranged in parallel to the direction of electrolysis, that is, the traveling direction of light in the cell, and pass without any optical rotation. Therefore, the light is
And is blocked. When used in the neutral density filter of the present embodiment, the amount of light transmitted in each fine region is adjusted by changing the optical rotation from 0 to 90 (deg.).

FIG. 10B uses a GH (Guest-Host) type liquid crystal cell 36, in which a dye molecule is mixed into the GH type liquid crystal cell 36 to produce a color. That is, the color of the transmitted light can be changed depending on the presence or absence of the applied voltage. That is, when black is used for the dye molecules, transmitted light can be attenuated as a whole. When an Nn type nematic liquid crystal is used for a liquid crystal or an n type dye is used for a dye,
When a voltage is applied, the arrangement of the liquid crystal molecules changes to color the passing light, thereby attenuating the light intensity. That is, in the state (b-1) where no voltage is applied, the light passing through the polarizer 34 is not colored even after passing through the GH type liquid crystal cell 36, and the illuminance of the light is attenuated. There is no. On the other hand, when a voltage is applied to some extent as in (b-2), black coloring is performed when passing through the GH type liquid crystal cell 36, and as a result, the light intensity is attenuated. When used in the neutral density filter of the present embodiment, the amount of transmitted light in each fine region is adjusted by changing the colorant by adjusting the voltage.

FIG. 10C shows DS (Dynamic Scatter).
ing) type liquid crystal cell 38, which uses a nematic liquid crystal of a homogenous arrangement, and in a state where no voltage is applied (c-1), the DS type liquid crystal cell 38 is transparent so as to transmit incident light as it is. It is. On the other hand, (c−
When a certain voltage or more is applied as in 2), the liquid crystal molecules move, exhibit a random turbulent appearance, and an infinite number of birefringent regions are formed inside the cell. Therefore, incident light is scattered and becomes cloudy. When used for the neutral density filter of the present embodiment,
The amount of white turbidity is changed by voltage adjustment to adjust the amount of transmitted light in each fine region.

FIG. 10D shows a PD (Polymer Dispers).
An ion) type liquid crystal cell 40 is used, in which a polymer is dispersed in a liquid crystal layer. When no voltage is applied as shown in (d-1), a liquid crystal portion having a different molecular direction is used. Since the optical refractive index of the polymer portion 40a is different from that of the polymer portion 40b, the incident light is scattered and looks cloudy. On the other hand, (d-2)
As shown in (1), when a voltage is applied, the molecular arrangement of the liquid crystal is aligned. As a result, the optical refractive indices of the liquid crystal portion 40a and the polymer portion 40b match, and the incident light passes without being scattered, and the illuminance does not decrease. However, in the case of the PD type liquid crystal cell 40, the amount of attenuation of transmitted light decreases when a voltage is applied, which is opposite to the above three types.
Is used in a neutral density filter, it is necessary to reduce the output of the optical sensor circuit when the output exceeds the limit incident illuminance Eth.

In this embodiment, the case where the darkening filter is applied to a night vision device to prevent halation has been described as an example. However, only light having a predetermined illuminance or more with respect to incident light is attenuated. Light other than the above is applicable to a device that needs to be transmitted without attenuation, and the same effect as in the present embodiment can be obtained.

The circuit configuration of the optical sensor circuit, the type of liquid crystal cell, and the like are also examples, and the present invention can be applied to a neutral density filter as long as it has the same function. Can be.

[0038]

According to the present invention, incident light is detected for each of a plurality of fine regions constituting the optical image receiving surface of the neutral density filter, and light having a predetermined illuminance or higher (light having a predetermined brightness or higher) is detected. Only at the time of detection, the light transmittance of the corresponding minute area is adjusted to attenuate the illuminance of the transmitted light, and light weaker than a predetermined illuminance is transmitted without forcible attenuation. As a result, it is possible to reliably attenuate only strong light and convert it into an optical image having a certain illuminance or less with an easy configuration.

Further, if this neutral density filter is used in a night vision device, light having a predetermined illuminance or more is prevented from being incident on the night vision device, halation can be reliably prevented, and the light intensity originally lower than the predetermined illuminance can be prevented. The light is incident on the night vision device without being attenuated, and the light is multiplied to obtain a clear optical image.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram illustrating a configuration of a night vision device including a neutral density filter according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating a configuration of a neutral density filter according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram illustrating a state in which liquid crystal cells constituting a neutral density filter according to the embodiment of the present invention are arranged in a matrix.

FIG. 4 is an explanatory diagram illustrating an equivalent circuit of a neutral density filter cell according to an embodiment of the present invention and a neutral density filter that is an aggregate thereof, and a limit incident illuminance of the neutral density filter.

FIG. 5 is an enlarged view of a neutral density filter according to the embodiment of the present invention.

FIG. 6 is an explanatory diagram illustrating a change in illuminance of the night vision device according to the embodiment of the present invention.

FIG. 7 is a schematic diagram illustrating attenuation of transmitted light of the neutral density filter according to the embodiment of the present invention.

FIG. 8 is an explanatory diagram illustrating an equivalent circuit of another configuration of the neutral density filter cell according to the embodiment of the present invention.

FIG. 9 is an enlarged view of the neutral density filter cell shown in FIG. 8;

FIG. 10 is an explanatory diagram illustrating a liquid crystal cell applicable to the neutral density filter according to the embodiment of the present invention.

FIG. 11 is an explanatory diagram illustrating a configuration of a conventional night vision device.

FIG. 12 is an explanatory diagram illustrating occurrence of halation in a conventional night vision device.

[Explanation of symbols]

Reference Signs List 10 neutral density filter, 14a liquid crystal cell, 20 neutral density filter cell (fine area) 22 optical sensor circuit, 22a
Photodiode, 22b resistor, 24 drive power supply for liquid crystal cell, 26 thin film metal electrode.

Claims (5)

[Claims] 1. An optical image receiving surface which receives each light spot constituting an optical image, and comprises a plurality of fine regions which together constitute an optical image receiving surface; And a variable transmission member disposed in each of the micro regions and, when the corresponding optical sensor detects light of a predetermined illuminance or more, changes the light transmittance of the micro regions to attenuate the illuminance of the transmitted light. A light reduction filter, wherein light transmittance is adjusted for each fine region. 2. The filter according to claim 1, wherein the fine regions are arranged in a matrix to form an optical image light receiving surface. 3. The filter according to claim 1, wherein the variable transmission member is formed of a liquid crystal layer. 4. An optical filter that attenuates the illuminance of an incident optical image by a predetermined amount, a photocathode that converts an optical image that has passed through the optical filter into a photoelectron image, and an electron that multiplies an electron group of the photoelectron image. A night vision apparatus including a multiplier, a phosphor screen that generates an amplified optical image from the multiplied electron group, and an imaging device that captures the amplified optical image. A night vision apparatus, which is a neutral density filter and adjusts light transmittance for each fine region to prevent halation. 5. Each of the light spots constituting the incident optical image is individually received by a plurality of fine areas, and the illuminance of each of the light spots is individually detected. When the illuminance is equal to or more than the predetermined illuminance, the light transmittance of the liquid crystal layer in the minute region where the light spot is incident is individually attenuated based on the detected light spot illuminance, and the illuminance of the light spot reaching the imaging device of the night vision device is reduced. A method for preventing halation, comprising adjusting the value to a predetermined value or less to prevent halation.