JP2014225829A - Structure of optical system for infrared camera - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain an infrared camera having a structure in which a large F value is obtained with an opening diameter as small as possible.SOLUTION: The infrared camera comprises: a condenser lens D for condensing infrared rays; an infrared detector A for detecting infrared rays having passed through the condenser lens D; and a shutter C disposed between the condenser lens D and the detector A and having a blade C3 for performing an opening and closing operation. An opening of a container member C1 for containing the blade C3 in an opened state is formed as an inclined plane S1 along the inclination of a beam bundle L incident to the detector A from the condenser lens D.

Description

  The present invention relates to the structure of an optical system of an infrared camera (imaging device).

As a performance index of a lens used in a camera optical system, there is a value called an F value. The F value is a value obtained by dividing the focal length of the lens by the effective aperture, and is an index indicating the brightness of the lens. The smaller the value, the brighter the optical system. When the object is dark, it is possible to compensate for the brightness by using illumination in the visible optical system. However, in the infrared optical system, since the amount of infrared rays generated by the object is detected and the measurement temperature is calculated, it is difficult to increase the physical quantity corresponding to the brightness from the outside. Therefore, the brightness of the optical system is a very important performance factor.

In a general infrared camera, the temperature is measured using an infrared detector that measures the amount of infrared rays. In addition to the infrared rays emitted from the measurement object, this detector is also affected by the amount of heat generated from the inside of the casing to which the detector is attached. Therefore, as it is, the temperature is not stabilized as the temperature of the housing changes. Therefore, there is a case where a structure for blocking the heat influence from the structure is provided. This structure is called a radiation (cold) shield.

Since the radiation shield is arranged so that structures other than the lens are not visible from the detector, the radiation shield is generally configured to cover the front side (detection surface side) of the detector. In that case, the field of view in front of the detector is limited to some extent, and therefore the F-number tends to increase. In addition, if there is variation in the temperature of the radiation shield, the effect on the detection surface will differ, so considering the surface uniformity of the measurement results, the shield will be as stable in temperature as possible. It is desirable that

  An infrared detector is a collection of sensors arranged two-dimensionally, but since the output characteristics of each sensor vary, the output value when measuring an object at a certain temperature is May be different. Therefore, in order to make the output value obtained uniform, some correction processing is required. One of the correction methods uses a shutter. In the correction using the shutter, the shutter is closed to block the forward field of view, the temperature of the field of view of the detector is made uniform, and calculation processing based on the temperature of the shutter at that time is performed, and a sensor corresponding to each pixel The output value is made uniform.

JP06-94523 A (Summary)

When the shield structure and the shutter are arranged in the housing, it is not desirable to arrange the shutter in the shield structure from the viewpoint that the temperature inside the shield needs to be uniform. For this reason, the shutter is disposed outside the shield. In that case, the opening diameter of the shutter needs to be larger than the opening diameter of the shield because of the light bundle. In addition to the opening of the shutter, since it is necessary to provide a space for housing the structure when the shutter is opened, an increase in the opening diameter leads to an increase in the size of the entire shutter. This is a major obstacle to the pursuit of camera miniaturization.

An example of a conventional shutter arrangement is shown in FIG. 1B.
A is an infrared detector, B is a radiation shield, C is a shutter, and D is an infrared lens. First, the opening diameter of the radiation shield B is set to a certain value due to optical design values, lens dimensions, and housing restrictions. Since the straight line connecting the opening and the end of the detector A is the outermost side of the light beam L, the shutter C arranged outside the shield B as viewed from the detector A does not block the light beam L. Need to design. In this case, since both the shutter C and the shield B have a constant thickness, the light flux L is expanded by the thickness of the shutter C on the lens D side in FIG. 1B. Therefore, the opening diameter of the shutter C must be set larger than the shield B. An increase in the opening diameter of the shutter C is directly linked to an increase in the outer diameter.

An object of the present invention is to obtain an infrared camera having a structure having a large F value with a smaller aperture diameter.

The infrared camera of the present invention is disposed between a condenser lens for collecting infrared rays, an infrared detector for detecting infrared rays transmitted through the condenser lens, and the condenser lens and the detector. In an infrared camera provided with a shutter having blades that perform opening and closing operations,
The opening of the housing member that houses the blades in the open state is formed by an inclined surface along the gradient of the light beam incident on the detector from the condenser lens.

According to the present invention, the opening of the housing member is formed with an inclined surface along the gradient of the light beam, so that the opening can be made as small as possible. Accordingly, since a large F value can be maintained, it is possible to design a housing with a smaller size without degrading optical performance.

FIG. 1A is a schematic configuration diagram of an optical system of an infrared camera according to an embodiment of the present invention, and FIG. 1B is a schematic configuration diagram of an optical system of a conventional infrared camera. FIG. 2A is an enlarged sectional view showing the structure of the shutter of the embodiment, and FIG. 2B is a sectional view showing the conventional example.

Preferably, on the condenser lens side and the detector side of the blade, the first and second housing members are disposed so as to sandwich the blade, respectively.
The first housing member on the condenser lens side is thicker than the second housing member on the detector side, and at least the opening of the first housing member is formed by the inclined surface.

The shutter itself that is opened and closed is generally thin, and the first housing member is generally thick in order to protect the shutter from the influence of heat from the outside. Therefore, the effect of this invention becomes remarkable by making the opening of this 1st accommodating member into an inclined surface.

Preferably, a radiation shield for suppressing unnecessary infrared rays from entering the detector is provided on the detector side of the shutter,
The opening of the shield is formed by an inclined surface along the gradient of the light beam.

In this case, the opening of the shield is formed with an inclined surface along the gradient of the light beam, and therefore the opening can be made as small as possible. Accordingly, since a large F value can be maintained, it is possible to design a housing with a smaller size without degrading optical performance.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
As shown in FIG. 1A, in this embodiment, the opening shapes of the shield B and the shutter C are set to a shape that follows the inclination of the light beam L. This makes it possible to set the opening area without creating a structurally useless portion.

A comparison of the shapes of the normal shutter C and the shutter C of this embodiment is shown in FIGS. 2A and 2B.
2A is an example of the present invention, and FIG. 2B is a conventional example. The shutter C has a structure in which the first and second accommodating members C1 and C2 on both sides accommodate the blade C3 that opens and closes. Since the conventional shutter C does not have an inclination as shown in FIG. 2B, the entire aperture has to be enlarged in order to cope with the expansion of the light beam L. Therefore, the entire shutter C becomes large.

On the other hand, in the present embodiment of FIG. 2A, the opening of the inner second housing member C2 is smaller than the first housing member C1 and the blade C3, the blade C3 is slightly larger, and the opening of the thick outer first housing member C1 is , An inclination along the light beam L is provided. As a result, the inner and outer diameters of the shutter C itself can be reduced.

  By aligning the inclination of the opening of the shield B in FIG. 1A so as to follow the inclination angle of the shutter C, it is possible to further reduce the arrangement.

This embodiment will be described in more detail.
In FIG. 1A, the condensing lens D condenses infrared rays. In the detector A, a large number of detection elements are secondarily arranged, and the infrared rays transmitted through the condenser lens D are detected. The shutter C is disposed between the condenser lens D and the detector A.

2A, the shutter C has a blade C3 that opens and closes, and first and second housings disposed on the condenser lens D (FIG. 1A) side and the detector A (FIG. 1A) side of the blade C3. Members C1 and C2 are provided. That is, both the housing members C1, C2 are arranged so as to sandwich the blade C3.

In the case of the present embodiment, the first housing member C1 on the condenser lens D (FIG. 1A) side is thicker than the second housing member C2 on the detector A (FIG. 1A) side, and the first housing member C1 has the first housing member C1. The opening is formed by the inclined surface S1. That is, the opening of the first housing member C1 is formed by an inclined surface S1 along the gradient of the light beam L incident on the detector A from the condenser lens D in FIG. 1A.
Here, the “inclined surface S1 along the gradient of the light beam L” means that the inclined surface S1 is formed along the outer peripheral surface of the light beam L incident on the detector A from the condenser lens D. In addition, “along” means that the outer peripheral surface and the inclined surface S1 do not need to coincide completely.

2A, the first housing member C1 may be made of plastic, the second housing member C2 may be made of metal, and the blade C3 may be made of an aluminum plate.

In the case of the present embodiment, a radiation shield B for suppressing unnecessary infrared rays from entering the detector A is provided on the detector A side of the shutter C in FIG. 1A. The opening of the shield B is formed by an inclined surface S2 along the gradient of the light beam L.
The radiation shield B may also be used as a radiator that cools the detector A with a Peltier element, and is generally formed of metal.

The present invention can be used for the structure of an optical system of an infrared camera.

A: (Infrared) detector B: (Radiation) Shield C: Shutter C1: First housing member C2: Second housing member C3: Blade D: Infrared (condensing) lens L: Light bundles S1, S2: Inclined surface

Claims (4)

A condensing lens for condensing infrared light, an infrared detector for detecting infrared light transmitted through the condensing lens, and a blade that is disposed between the condensing lens and the detector and performs an opening / closing operation Infrared camera comprising a shutter having
An infrared camera, wherein an opening of a housing member that houses the blade in an open state is formed with an inclined surface along a gradient of a light beam incident on the detector from the condenser lens. The camera of claim 1.
On the condenser lens side and the detector side of the blade, the first and second housing members are arranged so as to sandwich the blade, respectively.
The first housing member on the condenser lens side is thicker than the second housing member on the detector side, and at least the opening of the first housing member is formed by the inclined surface. The camera according to claim 1 or 2,
On the detector side of the shutter is provided a radiation shield that suppresses unnecessary infrared rays from entering the detector,
An infrared camera in which an opening of the shield is formed by an inclined surface along a gradient of the light beam. A condensing lens for condensing infrared light, an infrared detector for detecting infrared light transmitted through the condensing lens, and a shutter disposed between the condensing lens and the detector. In infrared camera,
On the detector side of the shutter is provided a radiation shield that suppresses unnecessary infrared rays from entering the detector,
An infrared camera in which an opening of the shield is formed by an inclined surface along a gradient of the light beam.

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