JPH06148503A - Focus adjusting device for infrared camera - Google Patents

Abstract

PURPOSE:To focus to the infinite point by providing a two-dimensional image detector, a light source and a focus control two-dimensional detector in a plane and a flat plate window on a substance side to control then so as to condense light to the focus control two-dimensional detector. CONSTITUTION:Infrared rays are transmitted through an optical system 2 and a part of them is reflected by a flat plate window 1 and then transmitted through the optical system 2 again. An image reflected by the flat plate window 1 makes a mirror image which is symmetrical to an optical axis, and when a focus control two-dimensional detector 5 is provided in a symmetrical position to a light source 4, infrared rays emitted from the light source 4 is focused in vicinity about the focus control two-dimensional detector 5 to form an image on the focus control two-dimensional detector 5. A processing circuit 6 gives a quantity of focus control to a focus control mechanism control device 7 to control a focus control mechanism 8. This operation is always performed, thereby being able to allow the focus position of the optical system 2 to coincide with the location of a two-dimensional picture detector 3 under any change of the ambient temperature.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a focus adjusting device for an infrared imager for detecting a target in a fire control system, for example.

[0002]

2. Description of the Related Art In general, an infrared imager for detecting a target in a fire control system needs to always focus the imager at infinity regardless of the presence or absence of a target so that a distant target can be found. On the other hand, since the infrared imager is mounted on a ship or an aircraft, the ambient temperature is wide such that it may reach −50 to 70 ° C. At this time, the optical system in the infrared imager has a refractive index of the material due to temperature change. The focus position moves due to changes in shape and shape. As a result, in some cases, even if the focus of the infrared imaging device is at infinity, the focus may be deviated due to a temperature change over time.

Conventionally, a focus adjusting device as shown in FIG. 6 has been used for such a focus shift. In the figure, 2 is an optical system, 3 is a two-dimensional image detector, 6 is a processing circuit, 7 is a focus adjustment mechanism controller, 8 is a focus adjustment mechanism, 12 is a memory, 13 is an optical axis, and 14 is a temperature sensor.

Next, the operation will be described. The amount of movement of the focal position due to temperature change is stored in the memory 12 as data by calculation or test in advance. Processing circuit 6
Compares the temperature data from the temperature sensor 14 installed in the vicinity of the optical system 2 with the data in the memory 12 to obtain the amount of focus compensation, and through the focus adjusting mechanism control device 7 and the focus adjusting mechanism 8, the optical system 2 The focus is adjusted by moving a part or the whole.

[0005]

Since the conventional focus adjusting device is constructed as described above, if the optical system 2 has a temperature distribution due to a rapid environmental temperature change, etc., it is stored in the memory 12. There was a problem that the amount of focus movement could not be obtained correctly from the data and it could not function sufficiently.

The present invention has been made in order to solve the above problems, and was made in order to obtain a focus adjustment device capable of correcting the focus movement due to temperature change. It is a thing.

[0007]

A focus adjusting apparatus according to the present invention has a flat window on the object side of an optical system, and a light source and a focus adjusting two-dimensional detector on the same plane as the two-dimensional image detector. It is to be placed.

[0008]

In the focus adjusting device according to the present invention, the output of the focus adjusting two-dimensional detector obtained when the infrared light emitted from the light source reaches the focus adjusting two-dimensional detector after reflecting off the flat window. The focus of the optical system is adjusted to maximize the peak value.

[0009]

Embodiment 1 A conceptual diagram of a focus adjusting device of the present invention will be described with reference to FIG.
In the figure, 1 is a flat window, 2 is an optical system, 3 is a two-dimensional image detector,
Reference numeral 4 is a light source, 5 is a two-dimensional detector for focus adjustment, and 13 is an optical axis.

Next, the operation will be described. The infrared light emitted from the light source 4 at room temperature shown in FIG.
When the parallel light from the target is imaged on the two-dimensional image detector 3, it becomes a parallel light flux by passing through the optical system 2. The parallel light flux is incident on the flat plate window 1, and most of it is transmitted, but part of it is reflected and re-enters the optical system 2. The optical system 2 focuses this parallel light flux on the same plane as the two-dimensional image detector 3. When the focus adjustment two-dimensional detector 5 is installed at this condensing point, an output of the same magnitude as that of the light source 4 having a high peak can be obtained. Next, when the environmental temperature rises in this state, the refractive index of the lens material forming the optical system 2 generally rises, so that the focal position of the optical system 2 approaches the optical system 2. Therefore, the infrared light emitted from the light source 4 becomes a convergent light flux when passing through the optical system 2 as in the high temperature of FIG. Since the light is condensed between the two-dimensional image detectors 3 and diverged on the focus adjusting two-dimensional detector 5, the output obtained from the focus adjusting two-dimensional detector 5 has a low peak and a wide spread. Becomes
Here, the optical system 2 is moved to the two-dimensional image detector 3 side as shown in FIG. 1C so that the peak of the output obtained from the focus adjustment two-dimensional detector 5 is maximized. The parallel light from the target can be focused on the two-dimensional image detector 3 side.

On the other hand, when the ambient temperature is lowered, generally, the refractive index of the lens material constituting the optical system 2 is lowered so that
The focus position of the optical system 2 is the same as in the case of the low temperature in (d).
Stay away from. Therefore, the light emitted from the light source 4 cannot be completely collected even by the two-dimensional focus adjustment detector 5. Here, by moving the optical system 2 to the optical window side as shown in FIG. 1E, the target at infinity is reversed so that the peak of the output obtained from the focus adjustment two-dimensional detector 5 is maximized. It is possible to collect the parallel light from the side of the two-dimensional image detector 3 side.

A first embodiment of the focus adjusting device for an infrared imaging device according to the present invention will be described below with reference to FIG. 1 in the figure
Is a flat window, 2 is an optical system, 3 is a two-dimensional image detector, 4 is a light source, 5 is a focus adjusting two-dimensional detector, 6 is a processing circuit, 7 is a focus adjusting device control mechanism, 8 is a focus adjusting mechanism, 13 is an optical axis.

The focus adjusting device for an infrared imaging device according to the present invention is constructed as described above and operates as follows. The infrared light emitted from the light source 4 passes through the optical system 2, a part of which is reflected by the flat plate window 1 and passes through the optical system 2 again. Flat window 1
Is installed perpendicularly to the optical axis, the image reflected by the flat window 1 is a mirror image symmetrical to the optical axis. Therefore, when the focus adjustment two-dimensional detector 5 is installed at a symmetrical position with respect to the light source 4, the infrared light emitted from the light source 4 is collected in the vicinity of the focus adjustment two-dimensional detector 5 and the focus adjustment two-dimensional detection is performed. An image is formed on the container 5. The processing circuit 6 gives an appropriate focus adjustment amount to the focus adjustment mechanism control device 7 so that the peak of the output obtained from this image is maximized, and the focus adjustment mechanism control device 7 gives the focus adjustment amount to the given focus movement amount. The adjusting mechanism 8 is controlled. By always performing this operation, the focus position of the optical system 2 and the two-dimensional image detector 3 can be made to coincide with each other regardless of any change in the environmental temperature.

Second Embodiment Next, a second embodiment of the focus adjusting device for an infrared imaging device according to the present invention will be described with reference to FIG. In the figure, 1 to 8 and 13 are parts having the same names and functions as in the first embodiment.

The focus adjusting device for an infrared imaging device according to the present invention is constructed as described above. In the first embodiment, since the flat window 1 is installed perpendicularly to the optical axis, the two-dimensional image detector 3 may detect itself, and a narcissus phenomenon may occur in which the center of the screen is dark and the periphery is bright. As a countermeasure, the flat window 1 may be installed with an inclination with respect to the optical axis. FIG. 3 shows an embodiment in which the flat window 1 is tilted and installed, and operates as follows. When the focal plane of the optical system 2 and the two-dimensional image detector 3 are coincident with each other, the infrared light emitted from the light source 4 passes through the optical system 2 and is at an angle α ′ represented by “Equation 5” with respect to the optical axis. It becomes an inclined parallel light flux.

[0016]

[Equation 5]

When the flat window 1 is set so that the optical axis is incident at an angle α represented by "Equation 6", the infrared light reflected by the flat window 1 is reflected by the optical axis at an angle α represented by "Equation 7". "It becomes a light beam that is inclined.

[0018]

[Equation 6]

[0019]

[Equation 7]

When this parallel light beam passes through the optical system 2 again, it is condensed at a position of a distance x'with respect to the optical axis represented by "Equation 8", and an image of the light source 4 is formed.

[0021]

[Equation 8]

When ε is set to a value other than 0 so as to satisfy the condition of "Equation 9", the infrared light emitted from the light source 4 is condensed outside the two-dimensional image detector 3.

[0023]

[Equation 9]

The focus adjustment two-dimensional detector 5 is installed at this position, and the processing circuit 6 focuses an appropriate focus adjustment amount so that the peak of the output of the focus adjustment two-dimensional detector 5 obtained from the image is maximized. The focus adjustment mechanism controller 7 controls the focus adjustment mechanism 8 so that the focus movement amount is given. By always performing this operation, the focus position of the optical system 2 and the two-dimensional image detector 3 can be made to coincide with each other regardless of any change in the environmental temperature.

Third Embodiment Next, a third embodiment of the focus adjusting device for an infrared imaging device according to the present invention will be described with reference to FIG. In the figure, 1 to 4, 6 to 8 and 13 are parts having the same names and functions as those of the first embodiment, 9 is an image detection area of the two-dimensional image detector, 10 is an unused part of the two-dimensional image detector, 11 Is an image separation device.

The infrared ray image pickup focus adjusting apparatus according to the third embodiment of the present invention is obtained by replacing the focus adjusting two-dimensional detector 5 of the first embodiment with an unused portion 10 of the two-dimensional image detector. The two-dimensional image detector 3 detects the target in the image detection area 9 and also detects the image emitted from the light source 4 in the unused portion 10 thereof, and outputs it to the image separation device 11 as well. The image separation device 11 separates the target two-dimensional image from the image of the light source 4, and outputs only the output obtained from the image of the light source 4 to the processing circuit 6. The processing circuit 6 gives an appropriate focus adjustment amount to the focus adjustment mechanism control device 7 so that the peak of the output becomes maximum, and the focus adjustment mechanism control device 7 controls the focus adjustment mechanism so as to have the given focus movement amount. . By always performing this operation, the focus position of the optical system 2 and the two-dimensional image detector 3 can be made to coincide with each other regardless of any change in the environmental temperature.

Fourth Embodiment Next, a fourth embodiment of the focus adjusting device for an infrared imaging device according to the present invention will be described with reference to FIG. 1-4, 6-11 in the figure
And 13 are parts having the same names and functions as those in the third embodiment.

The infrared ray image pickup focus adjusting apparatus according to the present invention is obtained by replacing the focus adjusting two-dimensional detector 5 of the second embodiment with an unused portion 10 of the two-dimensional image detector.
The infrared light emitted from the light source 4 forms an image of the light source 4 on the unused portion 10 of the two-dimensional image detector by the same operation as in the second embodiment, and the output of the obtained two-dimensional image detector 3 is the same as that of the second embodiment. The focus adjustment is performed by the same operation as that of No. 3, and the focus position of the optical system 2 and the two-dimensional image detector 3 regardless of any change in the environmental temperature
Can always be matched.

[0029]

As described above, according to the present invention, the light source and the focus adjusting two-dimensional detector are installed on the same plane as the two-dimensional image detector, and the flat window is installed on the object side of the optical system. By controlling the infrared light emitted from the light source to be focused on the focus adjustment two-dimensional detector, there is an effect that the optical system can always be focused at infinity.

[Brief description of drawings]

FIG. 1 is a diagram for explaining the principle of the present invention.

FIG. 2 is a diagram showing a first embodiment of a focus adjustment device for an infrared image pickup device according to the present invention.

FIG. 3 is a diagram showing a second embodiment of a focus adjustment device for an infrared imaging device according to the present invention.

FIG. 4 is a diagram showing a third embodiment of a focus adjusting device for an infrared imaging device according to the present invention.

FIG. 5 is a diagram showing a fourth embodiment of a focus adjusting device for an infrared imaging device according to the present invention.

FIG. 6 is a diagram showing an embodiment of a conventional focus adjustment device for an infrared image pickup device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Flat window 2 Optical system 3 Two-dimensional image detector 4 Light source 5 Two-dimensional detector for focus adjustment 6 Processing device 7 Focus adjustment mechanism control device 8 Focus adjustment mechanism 9 Image detection area of two-dimensional image detector 10 Two-dimensional image detection Unused part of the vessel 11 image separation device 12 memory 13 optical axis 14 temperature sensor

Claims (4)

[Claims] 1. An infrared imaging device having an optical system for condensing infrared rays transmitted through a flat plate window and a two-dimensional image detector installed on a focal plane of the optical system, wherein a focal position of the optical system is provided. A focus adjusting mechanism for moving the optical system, a flat window installed so that the optical axis of the optical system is vertically incident, an image detection area of the two-dimensional image detector on the same plane as the two-dimensional image detector A light source installed outside, a focus adjustment two-dimensional detector installed on the same plane as the two-dimensional image detector and at a position symmetrical to the light source with respect to the optical axis, and the focus adjustment two-dimensional detector A processing circuit that obtains and outputs a focus movement amount so that the peak value of the output of the detector is maximized, and a focus adjustment mechanism control device that controls the focus adjustment mechanism so that the focus movement amount obtained by the processing circuit is obtained. Infrared imaging characterized by comprising Focus adjustment device. 2. An infrared imaging device having an optical system for condensing infrared rays transmitted through a flat window and a two-dimensional image detector installed on a focal plane of the optical system, wherein a focal position of the optical system is provided. A focus adjusting mechanism for moving the optical system, a flat window installed so that the optical axis of the optical system is incident at an angle α, and an image detection area of the two-dimensional image detector on the same plane as the two-dimensional image detector. A light source that is provided outside and is located at a distance x from the optical axis, and a light source that is located on the same plane as the two-dimensional image detector and is located at a distance x ′ in the same direction as the light source and the optical axis. The focus adjustment two-dimensional detector installed in the device, the processing circuit for obtaining and outputting the focus movement amount so that the peak value of the output of the focus adjustment two-dimensional detector is maximized, and the processing circuit A focus adjustment mechanism control that controls the focus adjustment mechanism so that the focus movement amount is obtained. Control device, and the above α, x,
A focus adjusting device for an infrared imaging device, wherein x ′ has the following relationship. [Equation 1] [Equation 2] 3. An infrared imaging device having an optical system for condensing infrared rays transmitted through a flat window and a two-dimensional image detector installed on a focal plane of the optical system, wherein a focal position of the optical system is provided. A focus adjustment mechanism for moving the optical system, a flat window installed so that the optical axis of the optical system is vertically incident, and an image detection area of the two-dimensional image detector on the same plane as the two-dimensional image detector. A light source installed in the two-dimensional image detector, an unused part of the two-dimensional image detector installed at a position symmetrical with respect to the optical axis of the light source, and a peak value of the output of the unused part of the two-dimensional image detector. It is characterized by further comprising: a processing circuit that obtains and outputs a focus movement amount so as to be maximized; and a focus adjustment mechanism control device that controls the focus adjustment mechanism so that the focus movement amount obtained by the processing circuit is obtained. Focus adjustment device for infrared imager. 4. An infrared imaging device having an optical system for condensing infrared rays transmitted through a flat plate window and a two-dimensional image detector installed on a focal plane of the optical system, wherein a focal position of the optical system is provided. A focus adjusting mechanism for moving the optical system, a flat window installed so that the optical axis of the optical system is incident at an angle α, and an image detection area of the two-dimensional image detector on the same plane as the two-dimensional image detector. A light source which is provided outside and is installed at a position of distance x from the optical axis, and an unused portion of the two-dimensional image detector installed at a position of distance x ′ in the same direction with respect to the light source and the optical axis. A processing circuit for obtaining and outputting a focus movement amount so that a peak value of an output of an unused portion of the two-dimensional image detector is maximized; and the focus movement amount for obtaining the focus movement amount obtained by the processing circuit. A focus adjustment mechanism control device for controlling the adjustment mechanism, x, focus adjustment device of the infrared imager, characterized in that there is a relationship following equation between x '. [Equation 3] [Equation 4]