JP2018044987A - Reflection optical device, far-infrared ray imaging system, and gas detection system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost reflection optical device that is bright and compact, and has excellent optical performance, a far-infrared ray imaging system having the same, and a gas detection system.SOLUTION: A reflection optical device DU includes a reflection optical system TU forming an optical image IM of an object and an image sensor GT for converting the optical image IM into an electrical signal. The reflection optical system TU is composed of a diaphragm ST and first to fourth reflection surfaces S1 to S4 in order from an object side to form the optical image IM on a sensor surface SS of the image sensor GT after forming an intermediate image IM0 in between from the first to the fourth reflection surfaces S1 to S4. An angle of a central principal ray for forming an image at a center of a sensor surface SS of the image sensor GT deflected by the first to fourth reflection surfaces S1 to S4 is appropriately set.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a reflective optical device, a far-infrared imaging system, and a gas detection system. For example, it can be used in a wide wavelength band (especially in the infrared region from mid-infrared to far-infrared with a wavelength of 3-14 μm). The present invention relates to a reflection optical apparatus having a simple reflection optical system, a far infrared imaging system and a gas detection system including the reflection optical apparatus.

  Conventionally, various types of reflection optical systems have been proposed. For example, the reflection optical system described in Patent Document 1 is an off-axial optical system in which the reflection surface is decentered, and a light beam (center light beam) that forms an image at the center of the sensor surface by disposing a diaphragm between the reflection surfaces. The diaphragm surface is inclined with respect to the principal ray. In particular, in the reflective optical system for a line sensor, the light beam incident on the first reflection surface and the light beam emitted from the second reflection surface intersect, and the light beam incident on the third reflection surface and the fourth reflection surface are emitted. The arrangement is such that the light beam intersects with the stop, and the volume of the reflection optical system is made compact by the arrangement.

  The reflective optical system described in Patent Document 2 is a wide-angle lens system or a fish-eye lens system, and includes a plurality of decentered reflecting surfaces, thereby correcting distortion specific to fish-eye lenses and correcting trapezoidal distortion in oblique shooting. It is possible. In addition, the mirror size is reduced despite the wide-angle optical system, which is composed of an aperture disposed on the forefront and four reflecting surfaces and forms an intermediate image.

  The reflective optical system described in Patent Document 3 is composed of a plurality of decentered reflecting surfaces, and has a configuration capable of cutting unnecessary light. The diaphragm arranged at the forefront and the four reflecting surfaces are configured to form an intermediate image with an arrangement different from that of Patent Document 2.

  The reflective optical system described in Patent Document 4 includes a diaphragm surface and three or more decentered reflecting surfaces. For example, the correction of aberration is facilitated while reducing the size of all the reflecting surfaces by employing a configuration comprising four reflecting surfaces and forming an intermediate image between the second surface and the third surface.

JP 2004-258541 A JP 2006-215172 A WO00 / 048033 WO2011 / 077988

  In the reflective optical system described in Patent Document 1, since an intermediate image is not formed, the first reflective surface and the fourth reflective surface become enormous when employed in a bright F-number optical system that captures a two-dimensional image. If the arrangement is such that the beams do not cut the luminous flux, the volume of the reflective optical system will increase. Further, since the correction is insufficient due to the aberration generated by the large mirror surface, it cannot be used as a telephoto optical system having a bright F number.

  In the reflection optical system described in Patent Document 2, the deflection angle of the central light beam with respect to the principal ray is opposite to that of the first reflection surface and the second reflection surface. Similarly, the deflection angles at the third reflecting surface and the fourth reflecting surface are also opposite in sign. With such a configuration, it is not possible to sufficiently correct asymmetric aberration due to the decentered reflecting surface. In a telephoto optical system having a long focal length, aberrations increase with the focal length, and this type of reflective optical system cannot provide high optical performance. Further, since the chief ray of the central light beam is perpendicular to the image plane, it becomes difficult to correct the aberration in the decentering direction when the F number becomes bright.

  Also in the reflection optical system described in Patent Document 3, the deflection angle between the first reflection surface and the second reflection surface is opposite, and the deflection angle between the third reflection surface and the fourth reflection surface is also opposite. As in the reflection optical system described in Patent Document 2, since aberrations that are asymmetric in the decentering direction cannot be canceled, aberration correction cannot be sufficiently performed when used in a bright F-number optical system.

  In the reflection optical system described in Patent Document 4, the deflection angle of the central light beam with respect to the principal ray is the same for the first reflection surface and the second reflection surface, and similarly, the third reflection surface and the fourth reflection surface. The deflection angle at is also the same sign. For this reason, aberrations that are asymmetric in the decentering direction are canceled to some extent, and the arrangement is advantageous for correcting aberrations of off-axis light beams. However, since the deflection angle by the fourth reflecting surface is small, a large aberration is generated on the fourth reflecting surface. Therefore, when used in a bright F-number optical system, the aberration of axial light increases, and sufficient performance cannot be ensured.

  The present invention has been made in view of such circumstances, and an object thereof is to provide a reflective optical device that is bright, has good optical performance, is compact, and is low in cost, and a far-infrared imaging system and gas detection system including the same. There is to do.

In order to achieve the above object, a reflective optical device according to a first aspect of the present invention includes a reflective optical system that forms an optical image of an object by a reflection action, and an image sensor that converts the optical image into an electrical signal. A reflective optical device,
The reflection optical system includes, in order from the object side, a stop, a first reflection surface, a second reflection surface, a third reflection surface, and a fourth reflection surface, and the first reflection surface to the fourth reflection surface. After forming an intermediate image until, forming the optical image on the sensor surface of the image sensor,
In the stop, a right-handed local orthogonal coordinate system (X, Y, Z) having the stop center as the origin and the normal line at the stop center as the Z axis is set, and the first to fourth reflections are set. In each of the surfaces, a right-handed local orthogonal coordinate system (X, Y, Z) having the surface vertex as the origin and the normal at the surface vertex as the Z-axis is set, and is set at the center of the sensor surface. If the luminous flux to be imaged is the central luminous flux and the principal ray of the central luminous flux is the central principal ray,
The YZ plane of the stop and the YZ plane of the first to fourth reflecting surfaces coincide with each other, all the central principal rays are present on the YZ plane, and the first to fourth reflecting surfaces are within the YZ plane. It is arranged eccentrically so as not to cut the light beam incident from the stop, the focal lengths in the Y direction and X direction are equal, and the F number in the Y direction is 1.32 or less,
The following conditional expressions (1) to (4) are satisfied.
rFnoX> rFnoY (1)
φ1 × φ2> 0 (2)
φ3 × φ4> 0 (3)
139 ° <| φ4 | <146 ° (4)
However,
φ1: angle at which the central principal ray is deflected by the first reflecting surface,
φ2: angle at which the central chief ray is deflected by the second reflecting surface,
φ3: angle at which the central chief ray is deflected by the third reflecting surface,
φ4: angle at which the central chief ray is deflected by the fourth reflecting surface,
Each value of φ1 to φ4 is ± (90 ° to 180 °),
rFnoY: the ratio of the F number to the pupil in the Y direction,
rFnoX: the ratio of the F number to the pupil in the X direction,
rFnoY = DY / (| f | × tan (θY)),
rFnoX = DX / (| f | × tan (θX)),
DY: the diameter of the entrance pupil in the Y direction,
DX: entrance pupil diameter in the X direction,
| F |: absolute value of the focal length of the reflecting optical system,
θY: an angle at which two light beams passing through the end of the diaphragm of the central light beam intersect in the vicinity of the sensor surface in the YZ plane,
θX: an angle at which two rays passing through the edge of the diaphragm in the central light beam intersect in the vicinity of the sensor surface in the XZ plane,
It is.

  The reflective optical device according to a second aspect of the present invention is the reflective optical device according to the first aspect, wherein the first reflective surface and the second reflective surface form an intermediate image, and the third reflective surface and the fourth reflective surface are formed on the sensor surface. An optical image is formed.

  A reflective optical device according to a third invention is characterized in that, in the first or second invention, two or more of the first to fourth reflective surfaces are XY polynomial surfaces that are asymmetric with respect to the XZ plane. To do.

  A reflective optical device according to a fourth aspect of the present invention is characterized in that, in any one of the first to third aspects of the invention, a total horizontal angle of view of the reflective optical system is not less than 10 ° and not more than 17 °.

  A far-infrared imaging system according to a fifth aspect of the present invention is a far-infrared imaging system including the reflective optical device according to any one of the first to fourth aspects, wherein the reflective optical system is a telephoto optical system, The image sensor is a far infrared sensor.

  The far-infrared imaging system according to a sixth aspect of the present invention further includes a wide-angle optical system that forms an optical image of an object by refraction, and takes a telephoto image with the telephoto optical system. The system is characterized in that a wide-angle image is taken.

  A far-infrared imaging system according to a seventh invention is characterized in that, in the fifth or sixth invention, the far-infrared sensor has sensitivity in a wavelength band of 8 to 12 μm.

  A gas detection system of an eighth invention is a gas detection system including the reflective optical device according to any one of the first to fourth inventions, wherein the reflective optical system is a telephoto optical system, and the image The sensor is a cooling infrared sensor, and an image of the diaphragm is present between the fourth reflecting surface and the cooling infrared sensor.

  According to a ninth aspect of the present invention, the gas detection system according to the eighth aspect further includes a wide-angle optical system that forms an optical image of an object by refraction, and takes a telephoto image with the telephoto optical system. In this case, a wide-angle image is taken.

  A gas detection system according to a tenth aspect of the present invention is characterized in that, in the eighth or ninth aspect, the cooling infrared sensor has sensitivity in a wavelength band of 3 to 5 μm.

  The gas detection system according to an eleventh aspect is characterized in that, in the eighth or ninth aspect, the cooling infrared sensor has sensitivity in a wavelength band of 7 to 10 μm.

  According to the present invention, it is possible to realize a reflective optical device that is bright, has good optical performance, is compact, and is low-cost, and a far-infrared imaging system and gas detection system including the same.

1 is an optical path diagram showing an optical configuration of a first embodiment (Example 1). FIG. 4 is a lateral aberration diagram of Example 1. FIG. 4 is a lateral aberration diagram of Example 1. FIG. 3 is a distortion diagram of the first embodiment. The optical path figure which shows the optical structure of 2nd Embodiment (Example 2). FIG. 4 is a lateral aberration diagram of Example 2. FIG. 4 is a lateral aberration diagram of Example 2. FIG. 6 is a distortion diagram of the second embodiment. The optical path figure which shows the optical structure of 3rd Embodiment (Example 3). FIG. 4 is a lateral aberration diagram of Example 3. FIG. 4 is a lateral aberration diagram of Example 3. FIG. 6 is a distortion diagram of Example 3. The optical path figure which shows the optical structure of 4th Embodiment (Example 4). FIG. 6 is a lateral aberration diagram of Example 4. FIG. 6 is a lateral aberration diagram of Example 4. FIG. 6 is a distortion diagram of the fourth embodiment. FIG. 3 is a lens configuration diagram of Reference Example 1. FIG. 6 is a longitudinal aberration diagram of Reference Example 1. FIG. 6 is a lens configuration diagram of Reference Example 2. FIG. 6 is a longitudinal aberration diagram of Reference Example 2. The schematic diagram which shows the example of schematic structure of the infrared imaging system carrying a reflective optical apparatus. The figure which shows the flow of operation | movement of the infrared imaging system carrying a reflective optical apparatus. Explanatory drawing which shows the positive / negative direction of the deflection angle by reflection.

  Hereinafter, a reflective optical device, a far-infrared imaging system, a gas detection system, and the like according to embodiments of the present invention will be described. A reflective optical device according to an embodiment of the present invention is a reflective optical device that includes a reflective optical system that forms an optical image of an object by reflection and an image sensor that converts the optical image into an electrical signal. The reflecting optical system includes, in order from the object side, a stop, a first reflecting surface, a second reflecting surface, a third reflecting surface, and a fourth reflecting surface. After the intermediate image is formed up to four reflecting surfaces, the optical image is formed on the sensor surface of the image sensor.

  In the diaphragm, a right-handed local orthogonal coordinate system (X, Y, Z) having the diaphragm center as the origin and the normal line at the diaphragm center as the Z axis is set. In each of the four reflecting surfaces, a right-handed local orthogonal coordinate system (X, Y, Z) having the surface vertex as the origin and the normal at the surface vertex as the Z axis is set. If the light beam that forms an image at the center is the central light beam, and the principal ray of the central light beam is the central principal ray, the YZ plane of the diaphragm coincides with the YZ plane of the first to fourth reflecting surfaces, and the central principal ray All the light rays are present on the YZ plane, and the first to fourth reflecting surfaces are arranged eccentrically so as not to cut the light beam incident from the stop in the YZ plane, and the focal lengths in the Y direction and the X direction are equal. The F number in the Y direction is 1.32 or less To have.

The following conditional expressions (1) to (4) are satisfied.
rFnoX> rFnoY (1)
φ1 × φ2> 0 (2)
φ3 × φ4> 0 (3)
139 ° <| φ4 | <146 ° (4)
However,
φ1: angle at which the central principal ray is deflected by the first reflecting surface,
φ2: angle at which the central chief ray is deflected by the second reflecting surface,
φ3: angle at which the central chief ray is deflected by the third reflecting surface,
φ4: angle at which the central chief ray is deflected by the fourth reflecting surface,
Each value of φ1 to φ4 is ± (90 ° to 180 °),
rFnoY: the ratio of the F number to the pupil in the Y direction,
rFnoX: the ratio of the F number to the pupil in the X direction,
rFnoY = DY / (| f | × tan (θY)),
rFnoX = DX / (| f | × tan (θX)),
DY: the diameter of the entrance pupil in the Y direction,
DX: entrance pupil diameter in the X direction,
| F |: absolute value of the focal length of the reflecting optical system,
θY: an angle at which two light beams passing through the end of the diaphragm of the central light beam intersect in the vicinity of the sensor surface in the YZ plane,
θX: an angle at which two rays passing through the edge of the diaphragm in the central light beam intersect in the vicinity of the sensor surface in the XZ plane,
It is.

  In a refractive optical system using an optical component that transmits and refracts light like a lens, a bright F-number optical system can be realized by appropriate design. However, since the lens itself is heavy and has a different refractive index for each wavelength of light, there are problems such as an increase in the weight of the entire optical system and generation of chromatic aberration. Especially in telephoto optical systems, these problems are serious because the focal length is long. In addition, since a special glass material is required depending on the wavelength of light, a telephoto lens having a large lens diameter is expensive.

  On the other hand, in reflective optical systems using optical components such as mirrors that reflect light, light and inexpensive materials can be used for optical components by using surface reflection, and the direction of reflection is independent of the wavelength of light. Since chromatic aberration is the same, chromatic aberration does not occur. For this reason, the reflective optical system is suitable for constituting a telephoto optical system. However, since the light beam is bent by the reflecting surface and an overlapping portion of the incident light beam and the emitted light beam is generated, it is very difficult to realize a bright F-number optical system.

  When photographing visible light, it is possible to use an optical system with an F number of about 8 because it is in a bright environment when photographing outdoors, and a telephoto optical system with a long focal length is not necessary when photographing indoors. Therefore, the reflection optical system of the donut light beam whose secondary mirror cuts the light beam of the primary mirror can be used as a telephoto optical system for outdoor use. When a brighter reflective optical system is required, for example, each mirror is arranged so as to be decentered so as not to cut each other's light beam, thereby realizing a reflective optical system with an F number of about 3 to 1.35. Is possible.

  However, in order to realize a brighter reflecting optical system having an F number of 1.32 or less, further conditions are required for the arrangement of the reflecting surfaces. In other words, in a reflective optical system in which the reflecting surface is decentered in the YZ plane and arranged so as not to cut off the light beam incident from the stop, the F number for the pupil in the X direction is larger than the F number for the pupil in the Y direction. It will be necessary.

  For example, regarding the light collection angle corresponding to the F number, in the X direction, two light beams passing through the aperture of the light beam (center light beam) imaged at the center of the sensor surface in the XZ plane are near the sensor surface. When the value of DX / (| f | × tan (θX)) is calculated with θX as the angle at which the crossing occurs, the ratio rFnoX of the F number in the X direction with respect to the pupil is obtained. Where | f | is the absolute value of the focal length of the reflective optical system, and DX is the diameter of the entrance pupil in the X direction. The same applies to the Y direction. When DY / (| f | × tan (θY)) is calculated, a ratio rFnoY of the F number in the Y direction with respect to the pupil is obtained. However, θY is an angle at which two light beams passing through the end of the diaphragm of the light beam (center light beam) imaged at the center of the sensor surface in the YZ plane intersect near the sensor surface, and DY is an entrance pupil in the Y direction. Is the diameter.

  Further, in this reflection optical system, the focal length f is the same value in both the X direction and the Y direction, and the luminous flux that forms an image at a height of 1% with respect to the principal ray (central principal ray) of the central luminous flux and the maximum image height. Are defined as fX = ΔX / tan (ΔθX) and fY = ΔY / tan (ΔθY), using the difference between the height at which the principal ray reaches the sensor surface and the incident angle. However, fX is the focal length in the X direction, fY is the focal length in the Y direction (because the focal lengths in the X direction and the Y direction are equal, f = fX = fY), and ΔX is a light beam that forms an image at a height of 1% in the X direction. X coordinate on the sensor surface, ΔY is the Y coordinate on the sensor surface of the light beam having a height of 1% in the Y direction, and ΔθX is a light beam imaged in the center of the sensor and a light beam having a height of 1% in the X direction. The angle difference between the incident light and ΔθY is the difference in the angle of the incident light between the light focused at the center of the sensor and the light having a height of 1% in the Y direction.

  More specifically, the fact that the X direction has a larger F number means that the angle formed by the principal ray of the central beam (center principal ray) and the sensor surface is not 90 °, but has a slight inclination in the YZ plane. This indicates that the F number in the Y direction is brighter. From this point of view, it is desirable that the inclination formed by the sensor surface and the central chief ray is 90 ° (perpendicular) to 1 to 3 ° in absolute value in the YZ plane. That is, the absolute value of the angle of incidence of the central chief ray on the sensor surface (based on the surface normal) in the YZ plane is desirably 1 to 3 ° (−3 ° to −1 °, 1 ° to 3 °). .

  If the absolute value of the incident angle is larger than 3 °, aberration correction at a bright F number becomes easy, but the focal length differs greatly between the X direction and the Y direction, resulting in an unnatural image. If the absolute value of the incident angle is smaller than 1 °, it is easy to make the focal lengths coincide with each other in the X direction and the Y direction, but it becomes difficult to correct the aberration when the bright F number is used. The aberration in this case corresponds to spherical aberration in a non-decentered system, but is an asymmetrical aberration in a decentered system.

  In the conditional expression (1), the ratios FFnoY and rFnoX of the F number with respect to the pupil, not the F number itself, are defined because it is possible that the decentered reflective optical system does not have a circular aperture. As the definition of the F number itself, the F number in the X direction is FnoX = 1 / (2 × sin (θX / 2)), and the F number in the Y direction is FnoY = 1 / (2 × sin (θY / 2)). It is defined as

  Further, as can be seen from the conditional expressions (2) to (4), the deflection angles φ1 and φ2 have the same sign at the deflection angles φ1, φ2, φ3, and φ4 where the central principal ray is bent at the first to fourth reflecting surfaces. The deflection angles φ3 and φ4 have the same sign. 23, as shown in FIG. 23, the direction of the principal ray incident on the reflecting surface is set to 0 °, and the direction reflected in the counterclockwise direction from 0 ° to 180 ° is set to be positive (FIG. 23A). The direction reflected in the clockwise direction from 0 ° to 180 ° is set to be negative (FIG. 23B). That is, the deflection angle takes a value of + 180 ° to −180 °.

  The light beam formed to form a two-dimensional image has the smallest aberration when the deflection angle by the optical surface is 0 ° or ± 180 °. If the reflecting optical system is formed of a reflecting surface that is not decentered in the YZ plane, a reflecting optical system with small aberration can be realized. However, as described above, since the light beam is cut between the reflecting surfaces, the light beam has a donut shape. In this case, only an F number of about 8 can be realized even with a fairly large entrance pupil. On the other hand, if the reflecting surface is decentered in the YZ plane, a bright reflecting optical system can be realized. In order to reduce the aberration, the deflection angle should be as close to ± 180 ° as possible, and ± (90 ° to 180 °) should be taken. Even in such a configuration, since the off-axis light beam is reflected at different positions by the upper light beam and the lower light beam, an asymmetric aberration is generated in the Y direction. Such asymmetric aberration can be canceled to some extent by giving a deflection angle of the same sign on the next reflecting surface.

  By satisfying conditional expression (2), the deflection angles φ1 and φ2 have the same sign, and when conditional expression (3) is satisfied and the deflection angles φ3 and φ4 have the same sign, a bright reflective optical system can be obtained. It is possible to realize an optical system in which aberrations are corrected both on and off the axis. Taking the values of the deflection angles φ1 to φ4 in this way physically means that the light beam incident on the first reflecting surface intersects the light beam emitted from the second reflecting surface, and similarly enters the third reflecting surface. And the luminous flux emitted from the fourth reflecting surface intersect each other. At this time, if an intermediate image is formed between the first reflecting surface and the fourth reflecting surface, it is possible to prevent all the reflecting surfaces from becoming extremely large, which is a more advantageous configuration for aberration correction. It becomes.

  The deflection angles φ1 and φ2 and the deflection angles φ3 and φ4 may be the same or opposite. There are four types of combinations of signs of deflection angles that satisfy the conditional expressions (2) and (3): positive / positive / positive / positive / negative / negative / negative / negative / positive / negative / negative / negative. In Examples 1 to 4 to be described later, positive / negative / negative is positive, but in negative / negative / positive, the positive / negative / negative are folded up and down. In the case of positive / positive, the lower half is bent in a “reverse 4 shape” and the sensor surface is in the direction of the incident surface. In negative / positive / positive, the optical path is reversed up and down. Positive / positive / negative and negative / negative / negative are optically mirror-symmetrical and have the same performance. The same applies to positive / negative / negative and negative / positive / positive. From an optical point of view, the mirrors are mirror-symmetrical and have the same performance. In short, the same reflection optical system can be obtained by reversing the view of the Y axis.

  More preferably, the conditional expression (4) is satisfied, that is, the absolute value of the deflection angle φ4 by the fourth reflecting surface is set to 139 ° to 146 °. As described above, the closer the deflection angle is to ± 180 °, the smaller the aberration on the reflecting surface. Since the condensing angle of the light beam that forms an image on the sensor surface is determined on the fourth reflecting surface, in a bright F-number reflecting optical system, the aberration correction becomes easier as the deflection angle of the fourth reflecting surface is closer to ± 180 °. However, in order to correct the asymmetrical aberration of the off-axis light beam as described above, the deflection angle φ3 and the deflection angle φ4 have the same sign, and the light beam incident on the third reflection surface and the light beam emitted from the fourth reflection surface And intersect. At this time, if the deflection angle φ4 is larger than ± 146 °, the third reflecting surface cuts off the light beam emitted from the fourth reflecting surface, and a reflecting optical system with a bright F number cannot be constructed. On the other hand, when the deflection angle φ4 is smaller than ± 139 °, aberration correction for a wide luminous flux is insufficient, and sufficient aberration (spherical aberration) that can be used as a bright F-number reflective optical system cannot be corrected.

  As described above, the four reflecting surfaces are decentered in the YZ plane and arranged behind the stop to constitute the reflecting optical system, and an intermediate image is formed between the first reflecting surface and the fourth reflecting surface. Thus, it is possible to easily correct the aberration by suppressing the effective diameter of all the reflecting surfaces. The first reflection surface and the second reflection surface have the same sign, and the third reflection surface and the fourth reflection surface have the same sign. The asymmetrical aberration in the Y direction generated by the eccentric arrangement of the fourth reflecting surface can be canceled to some extent, and the aberration of the off-axis light beam can be made sufficiently small. Furthermore, by setting the absolute value of the deflection angle by the fourth reflecting surface to 139 ° to 146 °, an arrangement in which the axial aberration is small and the reflecting surfaces do not cut off the light beams from each other even when a bright F number is secured. Can be realized. With such a configuration, even on a telephoto optical system having a long focal length, sufficient on-axis performance and off-axis performance can be ensured with a bright reflective optical system having an F number of 1.32 or less. Therefore, it is possible to provide an inexpensive and lightweight telephoto optical system for an image sensor or an infrared image system that requires a large amount of light.

  Therefore, according to the above characteristic configuration, it is possible to realize a reflective optical device that is bright, has good optical performance, is compact, and is low in cost. By using the reflection optical device for an infrared imaging system such as a far infrared imaging system or a gas detection system, it becomes possible to add a high-performance infrared image input function to the infrared imaging system at a low cost. It can contribute to cost reduction, high performance, and high functionality of the system. A description will now be given of conditions and the like that are desirable for achieving these effects in a well-balanced manner and achieving higher optical performance, lighter weight, and smaller size.

  It is desirable that an intermediate image is formed by the first reflecting surface and the second reflecting surface, and the optical image is formed on the sensor surface by the third reflecting surface and the fourth reflecting surface. Even in the case of an optical system composed of only a reflecting surface, the effective diameter of a surface with a long focal length, such as a telephoto lens, increases with increasing distance from the stop. By making an intermediate image somewhere in the optical system, the increase in effective diameter can be suppressed to some extent. In particular, when an intermediate image is formed with the first reflection surface and the second reflection surface, the size of the intermediate image can be reduced. Furthermore, since the distance to the reflecting surface can be made substantially equal before and after the intermediate image, a high effect of reducing the effective diameter can be obtained. In addition, an image is formed by pairing two surfaces having the same sign of deflection angle, so that asymmetrical aberration due to decentering of the reflecting surface can be canceled well, and both on-axis aberration and off-axis aberration are small. Can be suppressed.

  It is desirable that two or more of the first to fourth reflecting surfaces are XY polynomial surfaces that are asymmetric with respect to the XZ plane. As described above, by setting the deflection angles φ1 and φ2 and the deflection angles φ3 and φ4 to the same sign, asymmetrical aberrations are canceled to some extent. However, since the off-axis light beam passes through different heights on the respective reflecting surfaces, the aberration correction of the off-axis light beam is not sufficient. In order to correct such aberration of the off-axis light beam, it is necessary to use an XY polynomial surface that is asymmetric with respect to the XZ plane. Note that the XZ plane in this case is viewed in local coordinates of each reflecting surface.

  It is desirable that the horizontal total angle of view of the reflective optical system is 10 ° or more and 17 ° or less. Even a bright optical system with an F-number of about 1.2 to 1.32 does not have a long focal length in an optical system having a horizontal total angle of view larger than 17 °. In this case, even if a refractive optical system is adopted, the diameter of each lens does not become so large, and there is no problem in terms of weight and cost. An optical system having a horizontal total angle of view smaller than 10 ° is unlikely to be used for general purposes. In other words, it is considered to be used for advanced security such as military use, but in this case, the cost does not become a problem. In military applications and the like, performance tends to be emphasized, but the reflective optical system is disadvantageous because the same performance cannot be obtained unless the reflective surface is made with twice as severe accuracy as the refractive surface. Therefore, the optical system having the longest focal length among the optical systems used for general purposes is targeted.

  Next, an infrared imaging system including the above-described reflection optical device will be described. Examples of the infrared imaging system include a far infrared imaging system and a gas detection system. These infrared imaging systems are equipped with a reflective optical system consisting of four non-axisymmetric reflecting surfaces as a telephoto optical system, and an infrared image sensor, thereby reducing the cost and performance of the infrared imaging system. Can be achieved. When a prism is used as the reflection optical system, chromatic aberration correction may be required if the telephoto optical system has a wide wavelength range. Therefore, if necessary, use a correction optical element in combination with the reflection optical system. Also good.

  An infrared imaging optical system is often expressed as a wide-angle optical system even if the diagonal total field angle 2ω is 25 to 30 °. Therefore, as a telephoto optical system for infrared rays, the diagonal total field angle 2ω is more than 22 °. Also, an imaging optical system having a small size can be assumed. Unless the telephoto optical system has a small angle of view, it is not necessary to use a reflective optical system. In other words, a wide-angle optical system can provide a sufficiently compact and inexpensive imaging optical system even with a refractive optical system. In addition, it is difficult to realize a wide-angle optical system with a reflective optical system, and a bright optical system is required because it is a telephoto optical system.

  Specific examples of infrared image sensors include thermal sensors such as pyroelectric sensors, microbolometers, and thermopiles; quantum sensors and the like. Pyroelectric sensors use a pyroelectric effect in which a ceramic containing lead zirconate titanate or the like spontaneously polarizes due to temperature changes. In most cases, it has a single light-receiving surface (sensor surface) and is inexpensive. It is a sensor. The microbolometer is a temperature sensor that has a light-receiving surface (sensor surface) in which a heat-sensitive material such as amorphous silicon or vanadium oxide is two-dimensionally arranged by a microfabrication technique and detects a change in resistance value due to a temperature rise. Common microbolometers currently used have 80 × 80, 320 × 240, 640 × 480 and the like. In the past, most of the sensors were cooled with liquid nitrogen to provide sufficient temperature resolution. However, in recent years, manufacturing technology has advanced, and products with a high temperature detection capability have been manufactured without cooling. It is coming. The thermopile is a temperature sensor that uses a thermocouple capable of converting heat into electric energy in series or in parallel to form a sensor surface, and is the second cheapest sensor after the pyroelectric sensor.

  A quantum sensor is a sensor that uses the internal photoelectric effect. Although the sensitivity is high, it is necessary to cool the sensor to suppress noise, and it is also called a cooling type sensor (in contrast, a thermal type sensor such as a pyroelectric sensor is called a non-cooling type sensor because it does not require cooling). Although the wavelength is sensitive from ultraviolet rays to far infrared rays, it is often used as a 3 to 5 μm mid-infrared sensor as an image sensor. As the sensor material, cadmium mercury telluride, antimony indium, potassium arsenide and the like are used.

  The far-infrared imaging system provided with the reflective optical device is characterized in that the reflective optical system is a telephoto optical system and the image sensor is a far-infrared sensor. The far infrared rays used are mainly infrared rays having a wavelength in the range of 7 to 14 μm. The body temperature of humans and animals is emitted light having a wavelength of 8 to 12 μm, and most of the far infrared optical system is used at a wavelength of 8 to 12 μm. The far-infrared region in the wavelength band of 8 to 12 μm is a range in which the temperature of the substance can be detected, and there are many that can be applied such as temperature measurement, human detection in the dark, and security. Recently, far-infrared sensor manufacturing technology has advanced, and inexpensive thermopiles, uncooled microbolometers, and the like have been manufactured, and an inexpensive lens system compatible with these has been desired. In addition, a lineup of far-infrared lens systems applicable to various fields is also desired, and an inexpensive telephoto optical system is awaited.

  However, since an inexpensive uncooled far-infrared sensor has a lower sensitivity than a cooled sensor, a lens system having an F number of about 1.0 to 1.3 is required. This is because, when a lens system darker than this is used, an image with a low contrast is obtained with infrared rays no matter how much the performance of the optical system is improved.

  When a bright F-number lens system is realized by a refracting optical system, the effective diameter necessary for the lens is increased according to the focal length, so that the cost is considerably increased. Even if it is used for an inexpensive uncooled far-infrared sensor, the far-infrared imaging system becomes expensive. Conventionally, a system in which a telephoto lens of a refractive optical system is combined with a relatively expensive cooling type sensor is known. Such a system is used as an advanced monitoring system for military use because the sensor itself is expensive. Therefore, the cost of the lens system is not important. Further, since the cooling type sensor has higher sensitivity than the non-cooling type sensor, the lens system may have an F number of about 2.5 to 3.5, and the cost of the refractive lens is not so high.

  In the far-infrared imaging system equipped with the reflection optical device, matching with an inexpensive far-infrared sensor by using a reflection optical system in which four reflecting surfaces are decentered in the YZ plane as a telephoto optical system. It is possible to combine a good and inexpensive reflective optical system. As a result, an inexpensive far-infrared imaging system can be realized.

  The far-infrared imaging system including the reflection optical device further includes a wide-angle optical system that forms an optical image of an object by refraction, and takes a telephoto image with the telephoto optical system, and captures a wide-angle image with the wide-angle optical system. It is desirable to have a configuration for taking a picture. It is further desirable to take a telephoto image and a wide-angle image at the same time.

  As an application example of the far-infrared imaging system, a security system for monitoring an intruder or the like can be considered. By using far-infrared images for the security system, it is possible to monitor a place where there is no illumination light, or a remote place where the illumination light does not reach. In remote monitoring, it is important to enlarge and display distant objects with a telephoto optical system to determine whether they are intruders, but it is also important to find suspicious persons and suspicious objects that do not know where to intrude at the same time. is there. In order to find a suspicious person or a suspicious object, an infrared image of a wide area is required. Therefore, it is preferable to provide a wide-angle optical system having a horizontal field angle of about 90 °. Alternatively, it is preferable that the wide angle optical system has a horizontal angle of view of about twice or more than that of the telephoto optical system.

  Since the far-infrared sensor does not have a large number of pixels, it is impossible to monitor a wide range only by telephoto shooting, and it is difficult to detect a monitoring target (such as a suspicious object) because the pixels are too coarse only by wide-angle shooting. For example, unmanned airplanes (drones) are small in size from 30 cm square to 1 m square and move at a high speed of about 50 km / h. In order to monitor such a suspicious object, it is efficient to detect the presence of the suspicious object from a distance of about 100 m, and then perform an enlarged image to determine the object.

  Therefore, a wide-angle optical system and a telephoto optical system are used as follows. First, the entire wide area is photographed with the wide-angle optical system, and the intruding target is detected from the obtained far-infrared image. Then, the detection of the monitoring target is reliably determined by changing the imaging range with a rotating mirror or the like and performing the enlarged imaging with the telephoto optical system around the detection range. From the determination result, if it is determined that it is a monitoring target, a notification is made, and if it is determined that it is not a monitoring target, the process returns to wide-angle shooting. By combining such a wide-angle optical system and a telephoto optical system, it is possible to detect abnormal phenomena (intruders, etc.) from a wide range even with low resolution. By this, it becomes possible to recognize the abnormal phenomenon more reliably.

  In the gas detection system including the reflection optical device, the reflection optical system is a telephoto optical system, the image sensor is a cooling infrared sensor, and the image of the diaphragm is the fourth reflection surface and the cooling infrared sensor. It exists in between. The mid-infrared rays used are radiated light having a wavelength of 2.5 to 7 μm. Most image sensors for mid-infrared are sensitive to radiation of 3-5 μm. A high-temperature object of 100 degrees or more emits strong radiated light in this range. However, since a radiation amount of a normal temperature object changes with a slight temperature change, this wavelength range can also be used for temperature measurement of a normal temperature object.

  In a camera that detects an invisible gas as an image, an absorption wavelength unique to each gas in the mid-infrared band (wavelength 2.5 to 7 μm) or the far-infrared band is used. That is, a gas image is captured by a mid-infrared or far-infrared image sensor. A highly sensitive cooling (quantum) sensor is used for gas imaging. A general infrared camera using a cooling sensor for mid-infrared uses a lens system having an F-number of about 2.5 to 3.5 because the sensitivity of the sensor is high. However, in order to photograph gas, only an absorption band having a narrow wavelength range can be used, so a bright lens having an F number of about 1.3 to 1.5 is required.

  A telephoto lens is required to detect gas far away, but the longer the focal length, the larger the effective diameter of the lens system. In order to realize a bright F-number lens system, a large lens is required in the refractive optical system. A large lens has problems such as an increase in weight and a high cost and difficulty in securing a material.

  In the gas detection system equipped with the reflection optical device, a gas detection system equipped with a bright and low-cost telephoto optical system is realized by decentering the four reflection surfaces in the YZ plane so as not to cut the light beam. Is possible. In addition, by constructing the aperture image located closest to the object side between the fourth reflecting surface and the sensor surface, the field of view can be seen near the cold door aperture placed in front of the sensor surface of the cooling sensor. The same effect is obtained as when the aperture is set. Therefore, it is possible to realize a gas detection system of a telephoto optical system from which noise is sufficiently removed.

  The gas detection system including the reflection optical device further includes a wide-angle optical system that forms an optical image of the object by refraction, and takes a telephoto image with the telephoto optical system, and takes a wide-angle image with the wide-angle optical system. It is desirable to adopt a configuration that performs the above. It is further desirable to take a telephoto image and a wide-angle image at the same time.

  The catalytic combustion type gas detection device can only detect gas pinpoint, but if a camera equipped with a cooling (quantum) sensor is used in the gas detection system, gas leaks in the imaging area, etc. It is possible to detect all over. As a more preferable gas detection system, first, a wide-angle area is photographed with a wide-angle optical system to observe whether there is an abnormality. If an abnormality is observed, a telephoto optical system is used to check whether the abnormality is a gas cloud by enlarging the image. At this time, it is preferable to provide a wide-angle camera simultaneously with the telephoto camera as the gas detection camera. When an abnormality is detected by image recognition in a video shot with a wide-angle camera, a telephoto camera that can change the shooting range with a rotating mirror or the like is enlarged and shot in the direction in which the abnormality is detected. By combining such a wide-angle optical system and a telephoto optical system, it is possible to detect abnormal phenomena such as gas leaks from a wide range even with low resolution, and after detection, the magnified image is taken with the telephoto optical system. This makes it possible to recognize abnormal phenomena more reliably.

  In the far-infrared imaging system, it is preferable that the far-infrared sensor has sensitivity in a wavelength band of 8 to 12 μm. Moreover, in the gas detection system, it is preferable that the cooling infrared sensor has sensitivity in a wavelength band of 3 to 5 μm or 7 to 10 μm.

  Since a reflective optical system composed of only a reflective surface does not cause chromatic aberration, it can be used for sensors in all wavelength bands. However, the sensor used in the visible to near-infrared region has sufficient sensitivity, and in shooting scenes using a telephoto optical system, there is a sufficient amount of light as in the outdoors. No need for a brighter lens system. Further, in the ultraviolet band, a quantum type sensor is used as in the case of the mid-infrared band. However, since the quantum type sensor has sufficient sensitivity for a normal shooting scene, the F number is 2.5 to 3.5. Lenses are sufficient. That is, a sufficiently compact telephoto optical system can be configured in a wavelength band other than the mid-infrared band or the far-infrared band.

  Therefore, in the far-infrared imaging system having an inexpensive far-infrared sensor that requires a reflection optical system having an F number of 1.0 to 1.3, the reflection optical system can be sufficiently compact and low in cost. In a gas detection system that requires an F number of 1.3 to 1.5 under special conditions such as taking a gas image, the reflection optical system can be sufficiently compact and cost-effective.

  In addition, when using a far-infrared band for gas detection, it is preferable to use a wavelength around 7 to 10 μm. As in the case of using the mid-infrared band, a gas composed of molecules of two or more elements has an intrinsic absorption wavelength in this range. The use of a filter having a narrow transmission wavelength range in order to capture this unique absorption wavelength is the same as in the case of the mid-infrared band, and this requires that the optical system be bright with an F number of about 1.3. A far-infrared sensor with good sensitivity is often a cooling type, and in order to cope with a cold door aperture, it is preferable that the aperture is on the last surface or the image of the aperture is near the sensor surface. For this reason, the four surfaces are arranged asymmetrically to ensure brightness, and the four-surface reflecting optical system in which the image of the stop exists near the sensor surface is matched.

  FIG. 21 schematically shows a schematic configuration example of an infrared imaging system equipped with a reflective optical device, and FIG. 22 shows an operation flow of the infrared imaging system. The infrared imaging system SE shown in FIG. 21 corresponds to a far-infrared imaging system, a gas detection system, and the like, and includes a reflective optical device DT, a refractive optical device DW, a rotating mirror MR, a driving mechanism AC, a signal processing unit 1, A control unit 2, a memory 3, an operation unit 4, a display unit 5, a notification unit 6 and the like are provided. The signal processing unit 1, the control unit 2, the memory 3, the operation unit 4, the display unit 5, the notification unit 6, and the like can be configured as a personal computer, for example.

  The reflection optical device DT is formed on a reflection optical system (telephoto optical system) OT that forms an optical image (image plane) IM of an object by reflection and a sensor surface (light receiving surface, imaging surface) SS that is a photoelectric conversion unit. The refractive optical device DW includes a refractive optical system (wide-angle optical system) that forms an optical image (image plane) IM of an object by refraction. System) OW and an image sensor GW that converts an optical image IM formed on a sensor surface (light receiving surface, imaging surface) SS, which is a photoelectric conversion unit, into an electrical signal. The reflective optical system OT and the refractive optical system OW are arranged so that the optical axes AX are orthogonal to each other, and a configuration in which a telephoto image is taken with the reflective optical system OT and a wide-angle image is taken with the refractive optical system OW. It has become.

  The rotating mirror MR is disposed on the object side of the reflection optical system OT, reflects light from the object, and enters the reflection optical system OT. The drive mechanism AC is an actuator that rotates the rotating mirror MR at high electrical speed, and performs mirror driving so that the rotating mirror MR can scan a part of a wide area that is a photographing range of the refractive optical system OW. . In addition, you may make it perform the scanning (for example, laser scanning) of the illumination light with respect to the imaging | photography range using the rotation mirror MR.

  In the infrared imaging system SE, signals generated by the image sensors GT and GW are subjected to predetermined digital image processing, image compression processing, and the like as required by the signal processing unit 1, and the memory 3 (semiconductor memory, Recorded on an optical disk or the like, or in some cases via a cable or converted into an infrared signal or the like and transmitted to another device (for example, a communication function such as a mobile phone).

  The control unit 2 is composed of a microcomputer and controls functions such as a shooting function (still image shooting function, moving image shooting function, etc.), an image reproduction function, etc .; control of a driving mechanism AC; control of a lens moving mechanism for focusing, etc. Etc. intensively. For example, the control unit 2 controls the reflective optical device DT and the refractive optical device DW so as to perform at least one of still image shooting and moving image shooting of a subject.

  The display unit 5 includes a display such as a liquid crystal monitor, and performs image display using image signals converted by the image sensors GT and GW or image information recorded in the memory 3. The operation unit 4 is a part including operation members such as an operation button (for example, a release button) and an operation dial (for example, a shooting mode dial), and transmits information input by the operator to the control unit 2. The alerting | reporting part 6 is a part which alert | reports the presence of the monitoring object outside with an audio | voice etc. As shown in FIG.

  In the infrared imaging system SE, as shown in FIG. 22, in cooperation with the refractive optical system (wide-angle optical system) OW and the reflective optical system (telephoto optical system) OT, the monitoring target (intruder, suspicious object, gas leak, etc.) Perform detection. First, an entire wide area is imaged by a wide-angle imaging detection system including a wide-angle optical system OW or the like. The obtained infrared image is subjected to image processing to detect a monitoring target, and the position information is output. Then, a telephoto imaging detection system consisting of a reflective optical system (telephoto optical system) OT, etc., automatically adjusts the shooting direction, changes the shooting range with a rotating mirror, etc., and enlarges shooting with the telephoto optical system around the detection range Do. Image processing is performed on the obtained infrared image, and detection of the monitoring target is reliably determined. From the determination result, if it is determined to be a monitoring target, a report is made. For example, an image is displayed on a display system including the display unit 5 (FIG. 21) and the warning unit 6 issues a warning by voice or the like. If it is determined that it is not a monitoring target, it returns to wide-angle shooting. As described above, the combined detection of the wide-angle optical system OW and the telephoto optical system OT enables detection of abnormal phenomena (intruders, etc.) from a wide range even with low resolution, and after detection, the telephoto optical system By zooming in, it is possible to recognize abnormal phenomena more reliably.

  FIGS. 1, 5, 9, and 13 show first to fourth embodiments of the reflective optical device DT in optical cross sections, respectively, and FIGS. 17 and 19 refer to specific examples of the reflective optical device DW. Examples 1 and 2 are shown as optical sections. The reflective optical device DW of Reference Example 1 electrically connects a refractive optical system (far-infrared wide-angle lens system) OW composed of first to third lenses L1 to L3 and an optical image IM formed on the sensor surface SS. An image sensor GW for converting the signal into a signal. The reflective optical device DW of Reference Example 2 electrically connects a refractive optical system (medium infrared wide-angle lens system) OW including first and second lenses L1 and L2 and an optical image IM formed on the sensor surface SS. An image sensor GW for converting the signal into a signal.

  In the first to fourth embodiments of the reflective optical device DT, a reflection optical system OT that forms an optical image IM of an object by reflection action, and an optical image IM formed on the sensor surface SS as an electrical signal. A reflective optical device DT including an image sensor GT for conversion; The reflective optical system OT includes, in order from the object side, a stop ST, a first reflective surface S1, a second reflective surface S2, a third reflective surface S3, and a fourth reflective surface S4. After the intermediate image IM0 is formed between the surface S1 and the fourth reflecting surface S4, the optical image IM is formed on the sensor surface SS of the image sensor GT. At this time, the intermediate image IM0 is formed by the first reflecting surface S1 and the second reflecting surface S2, and the optical image IM is formed on the sensor surface SS by the third reflecting surface S3 and the fourth reflecting surface S4. Further, an image ST0 of the stop ST is formed between the fourth reflecting surface S4 and the sensor surface SS.

  In each embodiment of the reflective optical device DT, the YZ plane in the stop ST coincides with the YZ plane in the first to fourth reflection surfaces S1 to S4, and the central principal ray CR is all on the YZ plane. The first to fourth reflecting surfaces S1 to S4 are arranged eccentrically so as not to cut the light beam incident from the stop ST in the YZ plane. Further, the focal lengths in the Y direction and the X direction are equal, and the F number in the Y direction is 1.32 or less, which satisfies the conditional expressions (1) to (4).

  In each embodiment of the reflective optical device DT, the deflection angles φ1 and φ2 have positive values, and the deflection angles φ3 and φ4 have negative values. However, the deflection angles φ1 and φ2 may be negative values, and the deflection angles φ3 and φ4 may be positive values, or a combination thereof. In the embodiment of the reflective optical device DT, the aperture diameter (= the diameter of the entrance pupil) has the same value. However, it is possible to increase the aperture diameter in the X direction to increase the F number in the X direction. It is. Since it is not decentered in the XZ plane, it will not be cut even if the beam width in the X direction is increased.

  In each embodiment of the reflective optical device DT, it is decentered only in the YZ plane. However, the first reflecting surface S1 and the second reflecting surface S2 may be decentered in the YZ plane, and the third reflecting surface S3 and the fourth reflecting surface S4 may be decentered in the XZ plane, or a reverse combination. Since aberrations due to decentration are corrected by pairing two surfaces, aberration correction can be similarly performed for such a combination.

  In each embodiment of the reflective optical device DT, it corresponds to the image sensor GT of mid-infrared or far-infrared. However, since the optical system is composed only of a reflective surface, even when using visible light, near-infrared light, ultraviolet light, etc., a brighter F-number is required than before, and a lightweight telephoto optical system is required. It is possible to apply it if it is intended for use.

  Hereinafter, the optical configuration of the reflective optical device, the far-infrared imaging system, and the gas detection system embodying the present invention will be described more specifically with reference to the construction data of the examples. Examples 1 to 4 (EX1 to 4) listed here are numerical examples respectively corresponding to the first to fourth embodiments of the above-described reflective optical device DT, and the first to fourth embodiments are described. The optical path diagrams (FIGS. 1, 5, 9, and 13) shown respectively show the optical arrangements, optical paths, and the like of the corresponding first to fourth embodiments. Reference Examples 1 and 2 (RX1 and RX2) are numerical examples corresponding to the refractive optical device DW described above. Reference Example 1 is a wide-angle lens system for far infrared rays, and Reference Example 2 is a wide-angle lens system for middle infrared rays. . Lens configuration diagrams (FIGS. 17 and 19) showing specific examples of the reflective optical device DW respectively show the lens arrangement, the lens cross-sectional shape, and the like of Reference Examples 1 and 2 (RX1 and RX2).

  As construction data of each embodiment, surface data, specifications, XY polynomial surface data and eccentricity data are shown. Table 1 shows correspondence data and related data of each conditional expression for each example. In the surface data, i (i = 1, 2, 3, 4) is a reflection surface number (i-th reflection surface Si: i-th reflection surface counted from the object side). In the field of surface number i, OB is The object surface, ST is a stop, IM0 is an intermediate image, ST0 is a stop image, and IM is an image plane (optical image). R is a paraxial radius of curvature (mm), and d is a surface interval. However, the surface interval d other than the object distance is described as eccentricity data. The decentration data indicates the arrangement of the optical surface, and the surface data and the XY polynomial surface data mainly indicate the shape of the optical surface.

  The arrangement of the optical surfaces in each of the examples (EX1 to EX4) is as follows: surface vertex coordinates (x, y, z) and rotation angle (rotation angle around the X axis, rotation angle around the Y axis, rotation angle around the Z axis) in the eccentricity data. ) Respectively. The surface vertex coordinates of the optical surface are determined based on the local orthogonal coordinate system (X, Y, z) in the global orthogonal coordinate system (x, y, z) using the surface vertex as the origin of the local orthogonal coordinate system (X, Y, Z). , Z) origin coordinates (x, y, z) = (X-axis parallel eccentricity, Y-axis parallel eccentricity, Z-axis parallel eccentricity) (unit: mm). The inclination of each optical surface is expressed by rotation angles about the axis, the Y axis, and the Z axis (unit: °; counterclockwise rotation with respect to the positive directions of the X, Y, and Z axes is X, Y, Z) This is the positive direction of the rotation angle.) However, the coordinate systems are all defined by the right-handed system, and the global orthogonal coordinate system (x, y, z) is an absolute coordinate system that matches the local orthogonal coordinate system (X, Y, Z) of the aperture stop ST. ing. The X direction, the Y direction, and the Z direction are coordinate axis directions in an orthogonal coordinate system (X, Y, Z) in which the surface vertex of the optical surface is the origin and the normal line at the surface vertex is the Z axis, The reference direction of the rotation angle around the coordinate axis (that is, the coordinate axis direction before rotation) is the coordinate axis direction (x direction, y direction, z direction) in the orthogonal coordinate system (x, y, z).

  In each of the embodiments (EX1 to EX4), the central principal ray CR (the principal ray of the central light beam formed at the center of the sensor surface SS) passes through the surface vertices of the reflecting surfaces S1 to S4. . However, the movement of the y-coordinate and z-coordinate of the surface vertex can be regarded as equivalent to the replacement of the term including odd-order coefficients for Y of the XY polynomial surface. Similarly, rotation around the X axis can be considered equivalent to replacing a term containing a first order coefficient for Y. For this reason, as long as the deflection angles and optical total lengths of the reflecting surfaces S1 to S4 are the same, even if the decentration data and the surface shape data are different, they can be regarded as equivalent optical systems.

The surface with * in the reflection surface number is an aspheric surface (XY polynomial surface) having no rotational symmetry axis, and the surface shape is a local orthogonal coordinate system (X, Y, Z) having the surface vertex as the origin. It is defined by the following formula (FS) used. An aspheric coefficient is shown as XY polynomial surface data. It should be noted that the coefficient of the term and the conic constant K not described in the XY polynomial surface data of each embodiment are 0, and E−n = × 10 ⁻ⁿ for all data.
Z = (C0 · h ² ) / [1 + √ {1− (1 + K) · C0 ² · h ² }] + Σ (X ^m · Y ⁿ · AmBn) (FS)
However, in the formula (FS),
h: height in the direction perpendicular to the Z axis (h ² = X ² + Y ² ),
Z: Displacement amount in the Z-axis direction at the position of height h (based on the surface vertex),
C0: curvature at the surface vertex (= 1 / r),
K: conic constant,
AmBn: m-order X and n-order Y aspherical coefficients (Σ represents the sum of 1st order to ∞th order for m and n),
It is.

  As specifications of each example (EX1 to EX4), the design wavelength (nm), the focal length (mm) of the entire system in the X and Y directions, the F number (Fno) in the X and Y directions, and the optical total length (mm) ), Half field angles (°; ωX, ωY) in X and Y directions, diagonal full field angles (°, 2ω), optical distance (mm) from the stop ST to the intermediate image IM0, and sensor surface SS The angle of incidence of the central chief ray CR on the surface (plane normal reference, °) is shown. The focal length of the entire system takes a negative value, which indicates that an image is formed on the sensor surface SS after the intermediate image IM0 is formed.

  In Examples 1 to 4, the F number is different between the X direction and the Y direction, the Y direction is 1.317 to 1.273, and the X direction is 1.326 to 1.296. Since it is decentered in the YZ plane, it is difficult to increase the F number in the YZ plane, and the deflection angle of the last reflecting surface S4 defined by the conditional expression (4) is a point.

  FIGS. 2 and 3; FIGS. 6 and 7; FIGS. 10 and 11; FIGS. 14 and 15 are lateral aberration diagrams (wavelength 12000.00 nm) corresponding to Examples 1 to 4 (EX1 to EX4), respectively. . 2, 6, 10, and 14, (A) and (F) are (50%, 0%), (B) and (G) are (50%, 100%), (C), ( (H) is (0%, -100%), (D), (I) is (0%, 100%), (E), (J) is (0%, 0%). ), (A) to (E) are the lateral aberrations in the tangential beam (T), and (F) to (J) are the lateral aberrations in the sagittal beam (S). Yes. 3, 7, 11, and 15, (A) and (E) are (100%, -100%), (B) and (F) are (100%, 0%), (C), (G) shows lateral aberration with respect to the angle of view (X, Y) of (100%, 100%), and (D), (H) respectively (50%, -100%). D) shows transverse aberration with the tangential beam (T), and (E) to (H) show transverse aberration with the sagittal beam (S).

  In each of the examples (EX1 to EX4), since all optical surfaces having power (power: an amount defined by the reciprocal of the focal length) are reflection surfaces, chromatic aberration does not occur. Therefore, the lateral aberration diagram showing the optical performance shows the lateral aberration with respect to the wavelength of 12 μm, but the results are the same for other wavelengths. Further, since all the reflecting surfaces S1 to S4 are decentered in the YZ plane, it is not possible to display spherical aberration and curvature of field shown by the rotationally symmetric reflecting optical system OT. For this reason, lateral aberration is shown with respect to the angle of view (X, Y) at 9 positions on the plus side of the X coordinate.

  4, 8, 12, and 16 are distortion diagrams corresponding to Examples 1 to 4 (EX1 to EX4), respectively, and the distortion is shown in a lattice graph. In the distortion diagram, a solid line is a distortion grid of each example, and a broken line is a grid of ideal image points (no distortion) in consideration of the anamorphic ratio. The X direction is the horizontal image height (Horizontal FOV (Field Of View)), and the Y direction is the vertical image height (Vertical FOV (Field Of View)).

  In the construction data of each reference example (RX1, 2), as surface data, in order from the left column, surface number i (OB: object surface, ST: aperture, IM: image surface), paraxial radius of curvature r (mm) , The shaft upper surface distance d (mm). The refractive index is the ratio of the traveling speed of light in the material to the vacuum, and is displayed for the d-line (587 nm) in the visible region. However, since this value has no meaning in the far-infrared region, the refractive index for a wavelength of 10 μm is often representatively shown in Reference Example 1, and this value is shown. For example, the refractive index at a wavelength of 10 μm of far-infrared optical materials used conventionally is germanium (Ge) = 4.004, silicon (Si) = 3.418, zinc sulfide (ZnS) = 2.200, selenium. Zinc halide (ZnSe) = 2.407 or the like. In the mid-infrared region, the refractive index for a wavelength of 4 μm is typically representative. However, since the reference example 2 is a system that performs gas detection using an absorption wavelength unique to each gas, the refractive index with respect to a wavelength of 3.3 μm near the absorption wavelength is shown.

  As a value representing the nature of dispersion, the Abbe number νd of d-line is used for visible light. This Abbe number is expressed by νd = (Nd−1) / (Nf−Nc) (where Nd is the refractive index at the d-line, Nf is the refractive index at the F-line, and Nc is the refractive index at the C-line. Rate.). However, since this value has no meaning in the far-infrared region, in Reference Example 1, the value ν represented by the formula: ν = (N10-1) / (N8−N12) is used as a value representing the dispersion property. (N8: refractive index at a wavelength of 8 μm, N10: refractive index at a wavelength of 10 μm, N12: refractive index at a wavelength of 12 μm). The larger the value ν, the smaller the difference in refractive index due to color, and the smaller the dispersion. For example, dispersions of infrared optical materials conventionally used are Ge = 1250, Si = 1860, ZnS = 23 (used for achromatic), ZnSe = 57 (used for achromatic), and the like.

  In the mid-infrared region, dispersion is often expressed using refractive indexes of 3 μm and 5 μm for a wavelength of 4 μm. However, in Reference Example 2, only the vicinity of the absorption wavelength specific to each gas in the mid-infrared region is used, so that the refractive index of 3.2 μm and 3.4 μm with respect to the wavelength of 3.3 μm is expressed as a substitute for dispersion. use. That is, the refractive index with respect to wavelength (nm) = 3400.00, 3300.00, 3200.00 is shown for the glass material: silicon (Si) used in Reference Example 2, respectively. In Reference Examples 1 and 2, the flat plate PT in front of the image plane IM is a protective plate of the image sensor GW.

In each reference example (RX1, 2), the surface with the surface number i marked with * is an aspheric surface rotationally symmetric with respect to the optical axis AX, and the surface shape is a local orthogonal coordinate system (X , Y, Z) is defined by the following formula (AS). As aspheric data, an aspheric coefficient or the like is shown. It should be noted that the coefficient of the term not described in the aspherical data of each example is 0, and E−n = × 10 ⁻ⁿ for all data.
Z = (C0 · h ² ) / [1 + √ {1− (1 + K) · C0 ² · h ² }] + Σ (Aj · h ^j ) (AS)
However,
h: height in a direction perpendicular to the Z axis (optical axis AX) (h ² = X ² + Y ² ),
Z: Displacement amount in the Z-axis (optical axis AX) direction at the position of height h (on the surface apex basis),
C0: curvature at the surface vertex (= 1 / r),
K: conic constant,
Aj: j-order aspheric coefficient (Σ represents the sum of the fourth to ∞ orders for j),
It is.

  As specifications of each reference example (RX1, 2), design wavelength (nm), focal length (mm) of the entire system, F number (FNO), full length (mm), half angle of view ω (°) , The horizontal full field angle 2ωX is shown.

  18 and 20 are aberration diagrams corresponding to Reference Examples 1 and 2 (RX1 and RX2), respectively, (A) is a spherical aberration diagram, (B) is an astigmatism diagram, and (C) is a distortion aberration diagram. It is. In the spherical aberration diagram, the amount of spherical aberration is represented by the amount of deviation (unit: mm) in the optical axis AX direction from the paraxial image plane, and the vertical axis indicates the height of incidence on the pupil normalized by its maximum height. Value (ie, relative pupil height). In FIG. 18A, the spherical aberration amount at the design wavelength (evaluation wavelength) of 10000 nm is indicated by a solid line, the spherical aberration amount at a wavelength of 8000 nm is indicated by a one-dot chain line, and the spherical aberration amount at a wavelength of 12000 nm is indicated by a broken line. Yes. In FIG. 20A, the spherical aberration amount at the design wavelength (evaluation wavelength) of 3300 nm is indicated by a solid line, the spherical aberration amount at a wavelength of 3200 nm is indicated by a one-dot chain line, and the spherical aberration amount at a wavelength of 3400 nm is indicated by a broken line. Yes. In the astigmatism diagram, the broken line T represents the tangential image surface at the design wavelength, and the solid line S represents the sagittal image surface at the design wavelength in terms of the deviation (unit: mm) in the optical axis AX direction from the paraxial image surface. The vertical axis represents the image height (IMG HT, unit: mm). In the distortion diagram, the horizontal axis represents distortion (%) at the design wavelength, and the vertical axis represents image height (IMG HT, unit: mm).

  The far-infrared wide-angle lens system of Reference Example 1 is a numerical example of a far-infrared refractive optical system (wide-angle optical system) OW that can be used in a security system using far-infrared images, and has a horizontal full field angle of 2ωX: 90. It is °. Since it is a rotationally symmetric refractive optical system OW, normal spherical aberration, curvature of field, and distortion are shown for a design wavelength of 10 μm. The wide-angle lens system for mid-infrared of Reference Example 2 is a numerical example of a refractive optical system (wide-angle optical system) OW for mid-infrared that can be used in a gas detection system, and has a horizontal total angle of view 2ωX: 24 °. . Since it is a rotationally symmetric refractive optical system OW, normal spherical aberration, curvature of field, and distortion are shown for a design wavelength of 3.3 μm.

Example 1
Unit: mm
Surface data
ird
OB: INFINITY INFINITY
ST: Refer to INFINITY eccentricity data
1 *: -100.14090 Refer to the eccentricity data (first reflective surface S1)
2 *: 60.86147 Eccentric data reference (second reflecting surface S2)
IM0: INFINITY Refer to eccentricity data
3 *: -130.89573 Eccentric data reference (3rd reflective surface S3)
4 *: 63.96635 Refer to eccentricity data (4th reflective surface S4)
ST0: INFINITY Refer to eccentricity data
IM: INFINITY

Spec design wavelength 3000-12000nm
Focal length -23.600 (X), -23.600 (Y)
Fno 1.326 (X), 1.317 (Y)
Optical total length 238.26
Half angle of view 8.500 ° (ωX), 6.400 ° (ωY)
Full diagonal angle of view 21 ° (2ω)
Optical distance from aperture stop ST to intermediate image IM0 93.90
Incident angle of central chief ray CR to sensor surface SS (surface normal reference) + 3 °

XY polynomial surface data: i = 1 *
B1: 7.2370E-03
A2: -5.4458E-04
B2: 2.6655E-03
A2B1: 5.9099E-05
B3: -3.0936E-05
A4: -6.8016E-07
A2B2: -6.6986E-07
B4: -1.9721E-06
A4B1: 2.7601E-08
A2B3: -4.3344E-08
B5: -1.1597E-08
A6: -1.2412E-09
A4B2: 9.7558E-10
A2B4: 2.5420E-09
B6: 1.7065E-10
A6B1: -1.3791E-10
A4B3: -3.0482E-11
A2B5: 5.4139E-12
B7: -2.1623E-12
A8: -1.6632E-12
A6B2: -8.9718E-13
A4B4: -5.4222E-12
A2B6: -6.8835E-12
B8: -8.6240E-14

XY polynomial surface data: i = 2 *
B1: -3.2364E-02
A2: 9.3012E-04
B2: -3.4681E-03
A2B1: -3.9189E-05
B3: -3.9299E-05
A4: -2.1575E-06
A2B2: -6.6414E-07
B4: -3.0706E-06
A4B1: 2.5730E-07
A2B3: -1.5473E-08
B5: -8.1441E-08
A6: -5.7192E-09
A4B2: -1.4720E-08
A2B4: 7.5141E-10
B6: -4.7555E-09

XY polynomial surface data: i = 3 *
B1: -4.6964E-01
A2: 5.9341E-04
B2: 8.5086E-03
A2B1: -2.9868E-05
B3: -8.9264E-05
A4: 4.1490E-07
A2B2: 1.7351E-06
B4: 4.5216E-07
A4B1: 1.8410E-09
A2B3: 1.7975E-08
B5: -1.3414E-08
A6: -8.4565E-11
A4B2: 3.6612E-10
A2B4: 2.8953E-09
B6: 1.8469E-09
A6B1: 3.0225E-12
A4B3: 1.0390E-11
A2B5: -3.2635E-11
B7: -6.0317E-11
A8: 5.3703E-14
A6B2: 5.5608E-13
A4B4: 3.3048E-13
A2B6: -3.5737E-12
B8: -2.4319E-12

XY polynomial surface data: i = 4 *
B1: 1.7533E-01
A2: -1.9105E-03
B2: 1.8171E-04
A2B1: 2.2888E-05
B3: 1.5839E-05
A4: -2.3409E-07
A2B2: -5.7983E-09
B4: 2.1603E-07
A4B1: 2.2557E-09
A2B3: 4.9950E-09
B5: 1.7347E-09
A6: -4.9567E-11
A4B2: -1.8352E-11
A2B4: 6.7368E-11
B6: 3.5761E-11
A6B1: 1.3596E-12
A4B3: 2.0063E-12
A2B5: 4.5714E-13
B7: -3.0604E-13
A8: -6.8812E-15
A6B2: 1.7959E-14
A4B4: 6.8818E-14
A2B6: 1.2214E-13
B8: 6.4279E-14

Eccentric data: i = 1 (diaphragm surface reference global coordinates)
X-axis parallel eccentricity: 0.000000
Y axis parallel eccentricity: 0.000007
Z-axis parallel eccentricity: 41.085256
Rotation around X axis: -19.677297
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: i = 2 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y axis parallel eccentricity: 18.077974
Z-axis parallel eccentricity: 19.680643
Rotate around X axis: -64.939315
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentricity data: IM0 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -6.654935
Z-axis parallel eccentricity: 21.415624
Rotate around X axis: -85.987358
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: i = 3 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -52.247579
Z-axis parallel eccentricity: 24.613880
Rotation around X axis: -80.827953
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: i = 4 (diaphragm surface reference global coordinates)
X-axis parallel eccentricity: 0.000000
Y axis parallel eccentricity: -36.075799
Z-axis parallel eccentricity: -9.512866
Rotate around X axis: 3.894833
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentricity data: ST0 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -29.907022
Z-axis parallel eccentricity: 16.672959
Rotate around X axis: 10.255842
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentricity data: IM (diaphragm surface reference global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -22.112710
Z-axis parallel eccentricity: 49.759102
Rotate around X axis: 10.255842
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Example 2
Unit: mm
Surface data
ird
OB: INFINITY INFINITY
ST: Refer to INFINITY eccentricity data
1 *: -105.04129 Eccentric data reference (first reflective surface S1)
2 *: 75.07433 Refer to the eccentricity data (second reflecting surface S2)
IM0: INFINITY Refer to eccentricity data
3 *: -166.62204 Eccentric data reference (3rd reflective surface S3)
4 *: 79.71076 Refer to eccentricity data (4th reflective surface S4)
ST0: INFINITY Refer to eccentricity data
IM: INFINITY

Spec design wavelength 3000-12000nm
Focal length -29.500 (X), -29.500 (Y)
Fno 1.318 (X), 1.300 (Y)
Optical total length 297.41
Half angle of view 6.818 ° (ωX), 5.128 ° (ωY)
Full angle of view 17 ° (2ω)
Optical distance from aperture stop ST to intermediate image IM0 127.73
Incident angle of central chief ray CR to sensor surface SS (surface normal reference) + 3 °

XY polynomial surface data: i = 1 *
B1: -5.9208E-01
A2: -2.0089E-04
B2: 3.1701E-03
A2B1: 6.9196E-05
B3: -5.7101E-06
A4: -2.9188E-07
A2B2: 6.7174E-07
B4: -1.3215E-06
A4B1: 8.8389E-09
A2B3: -1.2005E-08
B5: -1.0706E-08
A6: -1.5649E-10
A4B2: 6.4709E-10
A2B4: 2.7537E-09
B6: -2.5403E-09
A6B1: -5.4903E-11
A4B3: -8.1534E-11
A2B5: -6.9768E-11
B7: -4.2063E-11
A8: -5.3786E-13
A6B2: -3.0234E-12
A4B4: -7.3699E-12
A2B6: -8.4541E-12
B8: 3.0789E-12

XY polynomial surface data: i = 2 *
B1: -4.1656E-02
A2: 2.4397E-04
B2: -2.6420E-03
A2B1: -1.2911E-05
B3: -1.0571E-05
A4: -1.4438E-06
A2B2: 9.4826E-08
B4: -6.4473E-07
A4B1: 1.1040E-07
A2B3: 9.6818E-09
B5: -5.4133E-09
A6: -1.7689E-09
A4B2: -5.1396E-09
A2B4: 3.7002E-11
B6: -1.3380E-09

XY polynomial surface data: i = 3 *
B1: -4.5536E-01
A2: 5.1022E-04
B2: 8.4604E-03
A2B1: -2.9259E-05
B3: -1.1545E-04
A4: 2.1316E-07
A2B2: 1.5481E-06
B4: 1.5292E-06
A4B1: -1.1656E-09
A2B3: -1.6690E-10
B5: -1.8301E-08
A6: -1.3176E-11
A4B2: 7.9239E-11
A2B4: 5.7610E-10
B6: -1.1758E-09
A6B1: 1.8232E-12
A4B3: 3.1370E-12
A2B5: -3.6223E-12
B7: -2.2226E-11
A8: 1.0053E-14
A6B2: 1.2388E-13
A4B4: 7.8069E-13
A2B6: -1.7010E-13
B8: 1.6112E-12

XY polynomial surface data: i = 4 *
B1: 2.2496E-01
A2: -1.3709E-03
B2: 7.0603E-04
A2B1: 1.7015E-05
B3: 1.4535E-05
A4: -1.1760E-07
A2B2: 1.0337E-07
B4: 2.0804E-07
A4B1: 1.3288E-09
A2B3: 3.2643E-09
B5: 1.5737E-09
A6: -1.2724E-11
A4B2: 1.2827E-11
A2B4: 5.5455E-11
B6: 2.7996E-11
A6B1: 4.9467E-13
A4B3: 1.0831E-12
A2B5: 9.6018E-13
B7: 3.1090E-13
A8: -1.0975E-15
A6B2: 3.6210E-15
A4B4: 2.0954E-14
A2B6: 2.9043E-14
B8: 1.4756E-14

Eccentric data: i = 1 (diaphragm surface reference global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -0.000005
Z-axis parallel eccentricity: 51.700790
Rotation around X axis: -50.232848
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: i = 2 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: 22.321376
Z-axis parallel eccentricity: 24.339533
Rotate around X axis: -64.964322
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentricity data: IM0 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -18.295049
Z-axis parallel eccentricity: 27.215112
Rotate around X axis: -85.950303
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: i = 3 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -66.190456
Z-axis parallel eccentricity: 30.606029
Rotation around X axis: -80.835230
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: i = 4 (diaphragm surface reference global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -44.814484
Z-axis parallel eccentricity: -11.793358
Rotate around X axis: 5.090738
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentricity data: ST0 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y axis parallel eccentricity: -37.443463
Z-axis parallel eccentricity: 24.178524
Rotation around X axis: 8.580203
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentricity data: IM (diaphragm surface reference global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -29.923989
Z-axis parallel eccentricity: 60.874924
Rotation around X axis: 8.580203
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Example 3
Unit: mm
Surface data
ird
OB: INFINITY INFINITY
ST: Refer to INFINITY eccentricity data
1 *: -140.64055 Eccentric data reference (first reflective surface S1)
2 *: 99.48215 Refer to eccentricity data (second reflecting surface S2)
IM0: INFINITY Refer to eccentricity data
3 *: -227.49664 Eccentric data reference (3rd reflective surface S3)
4 *: 104.88284 Eccentric data reference (4th reflective surface S4)
ST0: INFINITY Refer to eccentricity data
IM: INFINITY

Spec design wavelength 3000-12000nm
Focal length -39.334 (X), -39.334 (Y)
Fno 1.298 (X), 1.273 (Y)
Optical total length 393.97
Half angle of view 5.124 ° (ωX), 3.850 ° (ωY)
Full angle of view 12.5 ° (2ω)
Optical distance from aperture stop ST to intermediate image IM0 170.79
Incident angle of central chief ray CR to sensor surface SS (surface normal reference) + 3 °

XY polynomial surface data: i = 1 *
B1: -5.9090E-01
A2: -3.7549E-04
B2: 2.2667E-03
A2B1: 3.3187E-05
B3: 4.9080E-06
A4: -2.5833E-07
A2B2: 2.2949E-07
B4: -6.6756E-07
A4B1: -7.7902E-10
A2B3: -1.3095E-08
B5: -6.7431E-09
A6: 6.8164E-11
A4B2: 8.9529E-11
A2B4: 3.5542E-10
B6: -1.7674E-09
A6B1: -7.6012E-12
A4B3: -2.4500E-11
A2B5: -2.5687E-11
B7: -2.0783E-11
A8: -1.1044E-13
A6B2: -6.0060E-13
A4B4: -1.4555E-12
A2B6: -1.4077E-12
B8: 1.6794E-12

XY polynomial surface data: i = 2 *
B1: -4.0359E-02
A2: -2.0255E-04
B2: -2.1699E-03
A2B1: -1.2460E-05
B3: -4.1190E-06
A4: -1.0310E-06
A2B2: 1.1879E-08
B4: -2.7754E-07
A4B1: 5.0951E-08
A2B3: -2.3848E-09
B5: 1.1970E-09
A6: -5.8797E-10
A4B2: -1.9563E-09
A2B4: -2.3310E-10
B6: -9.7575E-10

XY polynomial surface data: i = 3 *
B1: -4.5468E-01
A2: 3.7303E-04
B2: 6.9152E-03
A2B1: -2.3253E-05
B3: -9.0738E-05
A4: 9.0396E-08
A2B2: 8.3828E-07
B4: 7.6378E-07
A4B1: -1.3340E-09
A2B3: -1.6728E-09
B5: -1.6120E-08
A6: 3.3857E-12
A4B2: 2.1424E-12
A2B4: -1.3138E-10
B6: -1.5480E-09
A6B1: 4.6624E-13
A4B3: 2.0289E-12
A2B5: 7.0667E-12
B7: 2.7286E-11
A8: -2.2111E-16
A6B2: 7.4613E-15
A4B4: 3.0885E-13
A2B6: 7.4038E-14
B8: 1.8573E-12

XY polynomial surface data: i = 4 *
B1: 2.2310E-01
A2: -1.0569E-03
B2: 5.7427E-04
A2B1: 8.7047E-06
B3: 7.5274E-06
A4: -5.6886E-08
A2B2: 4.1417E-08
B4: 8.5655E-08
A4B1: 3.3550E-10
A2B3: 9.6864E-10
B5: 3.7113E-10
A6: -1.8351E-12
A4B2: 2.6900E-12
A2B4: 1.1983E-11
B6: 3.4354E-12
A6B1: 8.3287E-14
A4B3: 1.9251E-13
A2B5: 1.4641E-13
B7: 2.2743E-14
A8: -3.5064E-16
A6B2: -2.1410E-17
A4B4: 3.0863E-15
A2B6: 3.0218E-15
B8: 1.6363E-15

Eccentric data: i = 1 (diaphragm surface reference global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -0.000002
Z-axis parallel eccentricity: 68.563060
Rotation around X axis: -50.251167
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: i = 2 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: 29.569940
Z-axis parallel eccentricity: 32.493473
Rotation around X axis: -64.966077
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentricity data: IM0 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -25.879923
Z-axis parallel eccentricity: 36.405123
Rotate around X axis: -85.964827
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: i = 3 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y axis parallel eccentricity: -88.294528
Z-axis parallel eccentricity: 40.808041
Rotation around X axis: -80.835264
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: i = 4 (diaphragm surface reference global coordinates)
X-axis parallel eccentricity: 0.000000
Y axis parallel eccentricity: -60.070046
Z-axis parallel eccentricity: -15.054813
Rotation around X axis: 4.950851
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentricity data: ST0 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -48.466975
Z-axis parallel eccentricity: 41.708200
Rotate around X axis: 8.552981
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: IM (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -40.438848
Z-axis parallel eccentricity: 80.981335
Rotate around X axis: 8.552981
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Example 4
Unit: mm
Surface data
ird
OB: INFINITY INFINITY
ST: Refer to INFINITY eccentricity data
1 *: -144.89464 Eccentric data reference (first reflective surface S1)
2 *: 96.07589 Refer to the eccentricity data (second reflecting surface S2)
IM0: INFINITY Refer to eccentricity data
3 *: -262.76000 Eccentric data reference (3rd reflective surface S3)
4 *: 96.31704 Eccentric data reference (4th reflective surface S4)
ST0: INFINITY Refer to eccentricity data
IM: INFINITY

Spec design wavelength 3000-12000nm
Focal length -39.333 (X), -39.333 (Y)
Fno 1.297 (X), 1.273 (Y)
Optical total length 381.82
Half angle of view 5.124 ° (ωX), 3.850 ° (ωY)
Full angle of view 12.5 ° (2ω)
Optical distance from aperture stop ST to intermediate image IM0 177.16
Incident angle of central chief ray CR to sensor surface SS (surface normal reference) + 3 °

XY polynomial surface data: i = 1 *
B1: -5.8975E-01
A2: 1.8578E-04
B2: 1.7674E-03
A2B1: 2.5033E-05
B3: -1.4559E-05
A4: -1.9678E-07
A2B2: 2.3287E-07
B4: -2.4714E-07
A4B1: 1.9598E-09
A2B3: -1.7026E-09
B5: -4.7901E-09
A6: 7.0147E-11
A4B2: 1.6924E-10
A2B4: -2.8597E-10
B6: -1.2628E-09
A6B1: 3.7867E-12
A4B3: -2.8091E-12
A2B5: 1.7074E-11
B7: -3.7049E-12
A8: -6.3722E-14
A6B2: 1.3220E-13
A4B4: -2.8546E-13
A2B6: 2.0696E-12
B8: 1.4580E-12

XY polynomial surface data: i = 2 *
B1: -4.0206E-02
A2: -7.6370E-04
B2: -3.1028E-03
A2B1: -5.3151E-06
B3: -1.2040E-05
A4: -6.0358E-07
A2B2: 8.5886E-08
B4: -2.3310E-07
A4B1: 1.0253E-08
A2B3: 2.9088E-09
B5: -2.0851E-09
A6: -3.1304E-10
A4B2: -3.3258E-10
A2B4: -1.1257E-09
B6: -8.1045E-10
A6B1: 8.4462E-11
A4B3: -7.8978E-12
A2B5: 6.8116E-12
B7: -1.7995E-12
A8: -3.5859E-13
A6B2: -3.0191E-12
A4B4: 1.2932E-12
A2B6: 2.7253E-12
B8: 5.8311E-13

XY polynomial surface data: i = 3 *
B1: -4.8906E-01
A2: -2.1992E-04
B2: 8.7181E-03
A2B1: -2.7952E-05
B3: -1.0131E-04
A4: 1.1551E-07
A2B2: 1.2231E-06
B4: 1.6937E-06
A4B1: -2.3927E-09
A2B3: -1.6702E-08
B5: -1.8364E-08
A6: 1.4125E-11
A4B2: 1.5799E-10
A2B4: 6.8377E-10
B6: 1.7130E-09
A6B1: -2.6767E-13
A4B3: -1.3173E-12
A2B5: 1.6688E-11
B7: -4.3253E-11
A8: -1.4218E-15
A6B2: 6.3268E-15
A4B4: 7.8703E-15
A2B6: -3.9658E-13
B8: -5.1485E-12

XY polynomial surface data: i = 4 *
B1: 2.3219E-01
A2: -1.1330E-03
B2: 8.0151E-04
A2B1: 1.1353E-05
B3: 1.2802E-05
A4: -7.1838E-08
A2B2: 7.4503E-08
B4: 1.3918E-07
A4B1: 4.9982E-10
A2B3: 1.7226E-09
B5: 1.2040E-09
A6: -1.3429E-12
A4B2: 7.7269E-12
A2B4: 3.0221E-11
B6: 2.1282E-11
A6B1: 8.4300E-14
A4B3: 4.0677E-13
A2B5: 6.4317E-13
B7: 2.7642E-13
A8: -8.6226E-16
A6B2: -1.3792E-16
A4B4: 4.7742E-15
A2B6: 8.4432E-15
B8: 3.3666E-15

Eccentric data: i = 1 (diaphragm surface reference global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: 0.000039
Z-axis parallel eccentricity: 68.540576
Rotation around X axis: -50.211104
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: i = 2 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: 29.569940
Z-axis parallel eccentricity: 32.493472
Rotation around X axis: -64.966077
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentricity data: IM0 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y axis parallel eccentricity: -32.271742
Z-axis parallel eccentricity: 36.855999
Rotate around X axis: -85.964826
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: i = 3 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y axis parallel eccentricity: -88.294528
Z-axis parallel eccentricity: 40.808041
Rotation around X axis: -80.835264
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: i = 4 (diaphragm surface reference global coordinates)
X-axis parallel eccentricity: 0.000000
Y axis parallel eccentricity: -63.414310
Z-axis parallel eccentricity: -16.186923
Rotate around X axis: 7.241143
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentricity data: ST0 (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y axis parallel eccentricity: -48.825900
Z-axis parallel eccentricity: 52.912871
Rotate around X axis: 8.921277
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Eccentric data: IM (diaphragm surface global coordinates)
X-axis parallel eccentricity: 0.000000
Y-axis parallel eccentricity: -45.585812
Z-axis parallel eccentricity: 68.259950
Rotate around X axis: 8.921277
Rotation around Y axis: 0.000000
Rotation around Z axis: 0.000000

Reference Example 1 (Wide-angle lens system for far infrared rays)
Unit: mm
Surface data
ird N / ν
OB: INFINITY INFINITY
1 *: 18.72159 7.000000 4.004 / 1251
2: 8.68331 17.091768
3 (ST): INFINITY 0.500000
4 *: 37.85306 7.000000 4.004 / 1251
5: 2247.90524 8.688493
6 *: 13.95820 1.515826 4.004 / 1251
7 *: 28.79085 3.541168
8: INFINITY 1.000000 3.4178 / 1860
9: INFINITY 0.899200
IM: INFINITY 0.000000

Spec design wavelength 10000.0nm
Focal length 3.9586
FNO 1.3000
Total length 46.3373
Half angle of view ω 51.9214 °
(Horizontal full angle of view 2ωX = 90.000 °)

Aspheric data: i = 1 *
K: 0.000000
A4: 0.100503E-04
A6: -0.121120E-07
A8: 0.147112E-09
A10: 0.000000E + 00

Aspheric data: i = 4 *
K: -8.763694
A4: -0.978501E-05
A6: 0.109269E-05
A8: -0.306888E-07
A10: 0.000000E + 00

Aspheric data: i = 6 *
K: 0.545783
A4: -0.339683E-05
A6: -0.700369E-07
A8: 0.000000E + 00
A10: 0.000000E + 00

Aspheric data: i = 7 *
K: 0.035719
A4: 0.804669E-04
A6: 0.000000E + 00
A8: 0.000000E + 00
A10: 0.000000E + 00

Reference Example 2 (Wide-angle lens system for mid-infrared)
Unit: mm
Surface data
ird glass material
OB: INFINITY INFINITY
1 *: 24.60599 4.000000 Si
2: 18.18242 37.531970
3 *: 385.58552 10.000000 Si
4: -74.70601 16.480269
5: INFINITY 1.267849 Si
6: INFINITY 1.778000
7 (ST): INFINITY 18.517000
IM: INFINITY 0.000000

Spec design wavelength 3300nm
Focal length 22.6000
FNO 1.5000
Total length 71.0581
Half angle of view ω 17.0770 °
(Horizontal full field angle 2ωX = 24.000 °)

Aspheric data: i = 1 *
K: 0.492117
A4: -0.439116E-05
A6: -0.280107E-07
A8: 0.652010E-10
A10: -0.234771E-12

Aspheric data: i = 3 *
K: -5.901358
A4: -0.177937E-05
A6: 0.206428E-08
A8: -0.306562E-11
A10: 0.203044E-14

Refractive wavelength (nm) 3400.00 3300.00 3200.00
Si 3.432409 3.433184 3.434033

DT reflection optical device OT reflection optical system (telephoto optical system)
S1 to S4 First to fourth reflecting surfaces ST Aperture ST0 Aperture image IM0 Intermediate image IM Image plane (optical image)
GT Image sensor DW Refractive optical device OW Refractive optical system (Wide-angle optical system)
L1 1st lens L2 2nd lens L3 3rd lens GW Image sensor SS Sensor surface CR Central principal ray AX Optical axis SE Infrared imaging system (far infrared imaging system, gas detection system)
MR rotating mirror AC drive mechanism 1 signal processing unit 2 control unit 3 memory 4 operation unit 5 display unit 6 notification unit

Claims (11)

A reflection optical device comprising: a reflection optical system that forms an optical image of an object by reflection action; and an image sensor that converts the optical image into an electrical signal,
The reflection optical system includes, in order from the object side, a stop, a first reflection surface, a second reflection surface, a third reflection surface, and a fourth reflection surface, and the first reflection surface to the fourth reflection surface. After forming an intermediate image until, forming the optical image on the sensor surface of the image sensor,
In the stop, a right-handed local orthogonal coordinate system (X, Y, Z) having the stop center as the origin and the normal line at the stop center as the Z axis is set, and the first to fourth reflections are set. In each of the surfaces, a right-handed local orthogonal coordinate system (X, Y, Z) having the surface vertex as the origin and the normal at the surface vertex as the Z-axis is set, and is set at the center of the sensor surface. If the luminous flux to be imaged is the central luminous flux and the principal ray of the central luminous flux is the central principal ray,
The YZ plane of the stop and the YZ plane of the first to fourth reflecting surfaces coincide with each other, all the central principal rays are present on the YZ plane, and the first to fourth reflecting surfaces are within the YZ plane. It is arranged eccentrically so as not to cut the light beam incident from the stop, the focal lengths in the Y direction and X direction are equal, and the F number in the Y direction is 1.32 or less,
A reflective optical device satisfying the following conditional expressions (1) to (4);
rFnoX> rFnoY (1)
φ1 × φ2> 0 (2)
φ3 × φ4> 0 (3)
139 ° <| φ4 | <146 ° (4)
However,
φ1: angle at which the central principal ray is deflected by the first reflecting surface,
φ2: angle at which the central chief ray is deflected by the second reflecting surface,
φ3: angle at which the central chief ray is deflected by the third reflecting surface,
φ4: angle at which the central chief ray is deflected by the fourth reflecting surface,
Each value of φ1 to φ4 is ± (90 ° to 180 °),
rFnoY: the ratio of the F number to the pupil in the Y direction,
rFnoX: the ratio of the F number to the pupil in the X direction,
rFnoY = DY / (| f | × tan (θY)),
rFnoX = DX / (| f | × tan (θX)),
DY: the diameter of the entrance pupil in the Y direction,
DX: entrance pupil diameter in the X direction,
| F |: absolute value of the focal length of the reflecting optical system,
θY: an angle at which two light beams passing through the end of the diaphragm of the central light beam intersect in the vicinity of the sensor surface in the YZ plane,
θX: an angle at which two rays passing through the edge of the diaphragm in the central light beam intersect in the vicinity of the sensor surface in the XZ plane,
It is.   The reflective optical system according to claim 1, wherein the first reflective surface and the second reflective surface form an intermediate image, and the third reflective surface and the fourth reflective surface form the optical image on the sensor surface. apparatus.   The reflective optical apparatus according to claim 1, wherein two or more of the first to fourth reflecting surfaces are XY polynomial surfaces that are asymmetric with respect to the XZ plane.   4. The reflection optical apparatus according to claim 1, wherein a horizontal total angle of view of the reflection optical system is 10 ° or more and 17 ° or less. 5.   5. A far-infrared imaging system including the reflective optical device according to claim 1, wherein the reflective optical system is a telephoto optical system, and the image sensor is a far-infrared sensor. Far-infrared imaging system.   6. The apparatus according to claim 5, further comprising a wide-angle optical system that forms an optical image of an object by refraction, taking a telephoto image with the telephoto optical system, and taking a wide-angle image with the wide-angle optical system. Far infrared imaging system.   The far-infrared imaging system according to claim 5 or 6, wherein the far-infrared sensor has sensitivity in a wavelength band of 8 to 12 µm.   5. A gas detection system comprising the reflective optical device according to claim 1, wherein the reflective optical system is a telephoto optical system, the image sensor is a cooling infrared sensor, and the diaphragm Is present between the fourth reflecting surface and the cooling infrared sensor.   9. The system according to claim 8, further comprising a wide-angle optical system that forms an optical image of an object by refraction, taking a telephoto image with the telephoto optical system, and taking a wide-angle image with the wide-angle optical system. Gas detection system.   The gas detection system according to claim 8 or 9, wherein the cooling infrared sensor has sensitivity in a wavelength band of 3 to 5 µm.   The gas detection system according to claim 8 or 9, wherein the cooling infrared sensor has sensitivity in a wavelength band of 7 to 10 µm.

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