JP2005345959A - Reflection-type optical system and control method for reflection-type optical system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new reflection-type optical system having wide angle of vision and high resolution. <P>SOLUTION: The reflection-type optical system is constituted of a spherical mirror 11, and a 1st correction lens 12, a 2nd correction lens 13 and a 3rd correction lens 14, provided successively from a light incident side on the side of the center of curvature of the spherical mirror. Then, a focal plane 15 is provided between the spherical mirror 11 and the 3rd correction lens 14. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a reflective optical system and a control method for the reflective optical system.

  Conventional optical systems used in conventional telescopes include high-resolution optical systems that cut the speed of seconds and wide-angle optical systems that use fisheye lenses, but there are reflective optical systems that combine both wide-angle and high-resolution. There wasn't. For example, even a wide-angle camera for tracking an artificial satellite has only a few degrees of field of view, and enormous costs were required to cover the whole sky, making it impossible. There are also wide-angle cameras that use fisheye lenses, etc., but because they are lens optical systems, the light sampling rate is low, the detection sensitivity is low, and the light wavelength range that can be detected due to the problem of light transmittance to the lens There was also a problem that it was limited.

  An object of the present invention is to provide a novel reflective optical system having a wide viewing angle and high resolution.

In order to achieve the above object, the present invention provides:
A spherical mirror, and a first correction lens, a second correction lens, and a third correction lens that are sequentially provided from the light incident side on the curvature center side of the spherical mirror, and the spherical mirror and the third correction lens The present invention relates to a reflective optical system characterized in that a focal plane is provided between a lens and a lens.

  In the reflective optical system of the present invention, since the spherical mirror is used as the main mirror, a large viewing angle can be secured with a large aperture. On the other hand, in order to obtain a light image with sufficient brightness, the aperture ratio of the spherical mirror must be reduced. However, since the correction lens as described above is provided, aberration due to the reduction of the aperture ratio of the spherical mirror. Can be suppressed.

  Since the three correction lenses are used as described above, the viewing angle and resolution of the entire reflective optical system can be freely controlled by controlling the surface shape based on various control methods. The optical image having a wide viewing angle can be focused on the focal plane with high resolution.

  As described above, according to the present invention, a novel reflective optical system with a wide viewing angle and high resolution can be provided.

  The details of the present invention and other features and advantages will be described in detail below based on the best mode.

  FIG. 1 is a configuration diagram showing an example of a reflective optical system of the present invention. The reflective optical system 10 shown in FIG. 1 includes a spherical mirror 11, a first correction lens 12, a second correction lens 13, and a third correction lens that are sequentially provided from the light incident side on the curvature center side of the spherical mirror. And a correction lens 14. A spherical focal plane 15 having the same radius of curvature as the spherical mirror 11 is provided between the spherical mirror 11 and the third correction lens 14.

  In the reflective optical system 10 shown in FIG. 1, since the spherical mirror 11 is used as the main mirror, a large viewing angle can be secured with a large aperture. On the other hand, in order to obtain a light image with sufficient brightness, the aperture ratio of the spherical mirror 11 must be reduced. However, the correction lenses 12 to 14 suppress an increase in aberration due to the reduction of the aperture ratio of the spherical mirror 11. be able to.

  Next, the shape and arrangement of the spherical mirror 11 and the correction lenses 12 to 14 of the reflective optical system 10 shown in FIG. 1 are optimized.

  The optical system focuses light by a combination of reflection of light by a mirror and refraction of light by a lens. Reflection or refraction of a light beam by a mirror or lens depends on an incident angle θ with respect to the optical axis of the light beam and a wavelength λ of the light beam. Further, the range of fluctuation depends on the nature of the light source. Therefore, in order to optimize, the incident angle θ and the wavelength λ of the light beam should be changed within a range according to the purpose of use, and as a total, the degree of “blurring” of the focus should be used as a criterion for judgment. .

  An evaluation function can be illustrated as an example of quantifying the “blur”. Focus blur s (θ, λ) when a predetermined θ and λ are assumed for a predetermined optical system design can be evaluated by tracking the light beam with a computer. Then, by collecting and adding various values within the range of the target incident angle θ and wavelength λ, it is possible to reproduce the focal blur that would actually occur by a computer simulation.

但し、θは各光学素子に対する光の入射角度であり、λは光の波長である。 Therefore, if the optical system design, that is, the shape and arrangement of the mirror or lens is changed little by little and the shape and arrangement of the mirror or lens that minimizes the evaluation of the “blur” of the fictitiously reproduced focus is given The optimum optical design should be determined for the intended purpose, that is, in the range of the incident angle θ of the light to be observed and the wavelength λ of the light beam. In the present invention, in order to quantify the blur as described above, an evaluation function F as shown below is defined. The evaluation function F is called a “modified Powell method” that has already been established as a computer algorithm.

However, (theta) is the incident angle of the light with respect to each optical element, (lambda) is the wavelength of light.

なる式で表すことができる。なお、Ｚは各光学素子における表面の、基準面からの高さであり、ｈは各光学素子の光軸からの距離であり、Ｒは各光学素子の曲率半径であり、Ａは４次の補正係数であり、Ｂは６次の補正係数であり、Ｃは８次の補正係数であり、Ｚ₀は、光軸上での光学素子表面の位置である。 In order to systematically optimize the shape and arrangement of the spherical mirror 11 and the correction lenses 12 to 14 as one optical system using the evaluation function F described above, it is preferable to model these shapes and arrangement. In the present invention, a ray tracing program that ignores the wave nature of light can be used as the model. In this case, the shape and arrangement of the optical elements of the spherical mirror 11 and the correction lenses 12 to 14 are as follows.

It can be expressed by the following formula. Z is the height of the surface of each optical element from the reference plane, h is the distance from the optical axis of each optical element, R is the radius of curvature of each optical element, and A is the fourth order B is a sixth-order correction coefficient, C is an eighth-order correction coefficient, and Z ₀ is the position of the optical element surface on the optical axis.

  Therefore, in the range between the incident angle θ of the light to be observed and the wavelength λ of the light beam, each argument in the expression (2) is changed, and each argument when the evaluation function F represented by the expression (1) is minimized is changed. By determining, the optimal shape and arrangement of the spherical mirror 11 and the correction lenses 12 to 14 can be determined within the range of the incident angle θ and the wavelength λ.

  In the reflective optical system 10 shown in FIG. 1, the incident angle θ of the light beam to the spherical mirror 11 and the correction lenses 12 to 14 changes in the range of 0 to 25 degrees, and the light line has a wavelength λ of 330 nm to 410 nm. Assuming a wavelength distribution of nitrogen fluorescence having a spectrum, the shape and arrangement of the spherical mirror 11 and the correction lenses 12 to 14 are defined by the optimized numerical values of each argument as shown in Table 1.

  In Table 1, the surface numbers in the leftmost column correspond to the surfaces of the correction lenses 12 to 14 and the surface of the spherical mirror 15 shown in FIG. That is, the surface number 1 means “surface 1” on the light incident side of the first correction lens 12, and the surface number 2 means “surface 2” on the spherical mirror 11 side of the first correction lens 12. To do. The surface number 3 means “surface 3” on the light incident side of the second correction lens 13, and the surface number 4 means “surface 4” on the spherical mirror 11 side of the second correction lens 13. The surface number 5 means “surface 5” of the third correction lens 14 on the light incident side, and the surface number 6 means “surface 6” of the third correction lens 14 on the spherical mirror 11 side. The surface number 7 means “surface 7” on the light incident side of the spherical mirror 11.

  In the above optimization, the first correction lens 12 and the third correction lens 14 are in a symmetrical positional relationship with respect to the second correction lens 13, and the optical axis of the optical system 10 shown in FIG. The correction lenses 12 to 14 pass through the respective central portions. Further, the reference surface of the spherical mirror 11 is a plane perpendicular to the optical axis through two midpoints where the two surfaces of the second correction lens 13 and the optical axis intersect, and the reference surfaces of the correction lenses 12 to 14 are A plane perpendicular to the optical axis passes through the midpoint between the two surfaces of the second correction lens 13 and the optical axis.

  In Table 1, “R = ∞” means that the radius of curvature is infinite, that is, the optical element is a flat plate without having a curvature.

  FIG. 2 visualizes the shape of the surface 2 of the first correction lens 12, and FIG. 3 visualizes the shape of the surface 3 of the second correction lens 13. Referring to FIGS. 2 and 3, for example, when the pitch of Fresnelization is 10 mm, the depth from the reference surface can be about 0.5 mm, and the surface can be sufficiently Fresneled. It can be seen that 13 can be composed of a Fresnel lens. Although not shown, the same result can be obtained for the correction lens 14. In this case as well, a predetermined surface can be made Fresnel, and the correction lens 14 can be made of a Fresnel lens.

  FIG. 4 shows the focal point of the reflection optical system 10 shown in FIG. 1 defined by the calculated values of each argument shown in Table 1 with respect to the fluorescent light beam by nitrogen having the emission line spectrum between the wavelength λ = wavelength 330 nm and 410 nm. 6 is a graph showing a relationship between a spot size d on the surface 15 and an incident angle θ. As is apparent from FIG. 4, it can be seen that a fine spot size of 1 minute or less is maintained until the incident angle θ is in the range of about 25 degrees. Therefore, it can be seen that an optical image in a wide viewing angle range of about 50 degrees can be obtained with a high resolution of 1 arc angle or less.

  Therefore, by preparing about 10 reflective optical systems 10 as shown in FIG. 1, it is possible to monitor the whole sky with a high resolution of about 1 minute angle.

  As described above, the present invention has been described in detail based on the embodiments of the present invention with specific examples. However, the present invention is not limited to the above contents, and all modifications and changes are made without departing from the scope of the present invention. It can be changed.

  The present invention can be suitably used as an industrial apparatus in the fields of disaster prevention, defense, environmental science, monitoring, inspection, and the like, particularly in combination with a photoelectric imaging system and a solid-state imaging device.

It is a block diagram which shows an example of the reflection type optical system of this invention. It is the figure which visualized the shape of the surface of the 1st correction lens of the optical system shown in FIG. It is the figure which visualized the shape of the surface of the 2nd correction lens of the optical system shown in FIG. 2 is a graph showing a relationship between a spot size d on the focal plane and an incident angle θ in the optical system shown in FIG. 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Reflective optical system 11 Spherical mirror 12 1st correction lens 13 2nd correction lens 14 3rd correction lens 15 Focal plane

Claims (22)

  A spherical mirror; and a first correction lens, a second correction lens, and a third correction lens that are sequentially provided from the light incident side on the curvature center side of the spherical mirror, and the spherical mirror and the third correction lens. A reflective optical system, characterized in that a focal plane is provided between the lens and the lens. The shape and arrangement of the spherical mirror and the correction lens are

(Z: height of the surface of each optical element from the reference surface, h: distance from the optical axis of each optical element, R: radius of curvature of each optical element, A: fourth-order correction coefficient, B: sixth-order The reflection type optical system according to claim 1, wherein the reflection type optical system is expressed by the following equation: C: eighth-order correction coefficient, Z ₀ : position of optical element surface on optical axis The shape and arrangement of the spherical mirror and the correction lens based on the above equation (1)

The reflection according to claim 2, wherein the value is optimized based on an evaluation function (θ: incident angle of light with respect to each optical element, λ: wavelength of light). Mold optics. The shape and arrangement of the first correction lens on the incident side of the light are optimized as Z ₀ = −118.8, R = ∞, and A = B = C = 0 in the above equation (1). The reflective optical system according to claim 2, wherein the optical system is a reflective optical system. The shape and arrangement of the first correction lens on the spherical mirror side are as follows: Z ₀ = −118.8, R = −4330.6, A = 9.13768 × 10 ⁻¹⁰ , B The reflective optical system according to any one of claims 2 to 4, wherein the optical system is optimized as = -3.24485 × 10 ^-15 and C = 0. The shape and arrangement of the second correction lens on the light incident side are Z ₀ = −1.5, R = −8938.3, A = 5.763315 × 10 ^{− in the} above equation (1). ¹⁰ , B = −2.9923 × 10 ⁻¹⁵ , and C = −4.770851 × 10 ⁻²¹ , the reflective optical system according to claim 2. . The shape and arrangement of the second correction lens on the spherical mirror side are Z ₀ = 1.5, R = 8938.3, A = −5.76315 × 10 ⁻¹⁰ , B = The reflective optical system according to claim 2, which is optimized as 2.93923 × 10 ⁻¹⁵ and C = 4.770851 × 10 ⁻²¹ . The shape and arrangement of the third correction lens on the incident side of the light are Z ₀ = 115.8, R = 4330.6, A = −9.13768 × 10 ^{−10 in the} above equation (1). , B = 3.24485 × 10 ⁻¹⁵ , and C = 0, the reflective optical system according to claim 2. The shape and arrangement of the third correction lens on the spherical mirror side are optimized as Z ₀ = 18.8, R = ∞, A = B = C = 0 in the above equation (1). The reflective optical system according to any one of claims 2 to 8. The shape and arrangement of the spherical mirror on the incident side of the light are optimized as Z ₀ = 903.8, R-897.4, A = B = C = 0 in the above equation (1). The reflection-type optical system according to any one of claims 2 to 9, wherein the reflection-type optical system is characterized.   The reflective optical system according to any one of claims 1 to 10, wherein at least one of the first correction lens, the second correction lens, and the third correction lens is a Fresnel lens. system. The reflective optical system according to claim 1, wherein an incident angle of the light is 25 degrees or more and a spot size of the light is 1 minute or less.
A reflection type comprising a spherical mirror, and a first correction lens, a second correction lens, and a third correction lens, which are sequentially provided from the light incident side on the curvature center side of the spherical mirror. Optical system. Providing a spherical mirror and a first correction lens, a second correction lens, and a third correction lens sequentially from the light incident side on the curvature center side of the spherical mirror;
Setting a focal plane between the spherical mirror and the third correction lens;
The shape and arrangement of the spherical mirror and the correction lens

(Z: height of the surface of each optical element from the reference surface, h: distance from the optical axis of each optical element, R: radius of curvature of each optical element, A: fourth-order correction coefficient, B: sixth-order Correction coefficient, C: 8th order correction coefficient)
The shape and the arrangement based on the equation (1) of the spherical mirror and the correction lens

A control method for a reflective optical system, wherein the value is optimized based on an evaluation function (θ: light incident angle on each optical element, λ: light wavelength). . The shape and arrangement of the first correction lens on the incident side of the light are optimized as Z ₀ = −118.8, R = ∞, and A = B = C = 0 in the above equation (1). The method for controlling a reflective optical system according to claim 13, wherein: The shape and arrangement of the first correction lens on the spherical mirror side are as follows: Z ₀ = −118.8, R = −4330.6, A = 9.13768 × 10 ⁻¹⁰ , B The method for controlling a reflective optical system according to claim 13 or 14, wherein the control method is optimized as = -3.24485 × 10 ^-15 and C = 0. The shape and arrangement of the second correction lens on the light incident side are Z ₀ = −1.5, R = −8938.3, A = 5.763315 × 10 ^{− in the} above equation (1). The reflective optical system according to claim 13, wherein the reflective optical system is optimized as ¹⁰ , B = −2.9923 × 10 ⁻¹⁵ , and C = −4.770851 × 10 ^−21. Control method. The shape and arrangement of the second correction lens on the spherical mirror side are Z ₀ = 1.5, R = 8938.3, A = −5.76315 × 10 ⁻¹⁰ , B = The method for controlling a reflective optical system according to any one of claims 13 to 16, wherein the control method is optimized as 2.93923 × 10 ⁻¹⁵ and C = 4.770851 × 10 ⁻²¹ . The shape and arrangement of the third correction lens on the incident side of the light are Z ₀ = 115.8, R = 4330.6, A = −9.13768 × 10 ^{−10 in the} above equation (1). B = 3.24485 × 10 ⁻¹⁵ and C = 0, the control method for a reflective optical system according to claim 13. The shape and arrangement of the third correction lens on the spherical mirror side are optimized as Z ₀ = 18.8, R = ∞, A = B = C = 0 in the above equation (1). The control method for a reflective optical system according to any one of claims 13 to 18. The shape and arrangement of the spherical mirror on the incident side of the light are optimized as Z ₀ = 903.8, R-897.4, A = B = C = 0 in the above equation (1). The method for controlling a reflective optical system according to any one of claims 13 to 19, characterized in that it is characterized in that:   Based on the optimization using the formula (1) and the formula (2), at least one of the first correction lens, the second correction lens, and the third correction lens is configured by a Fresnel lens. The method for controlling a reflective optical system according to any one of claims 13 to 20, wherein the control method is used.   The method of controlling a reflective optical system according to any one of claims 13 to 21, wherein an incident angle of the light is 25 degrees or more and a spot size of the light is 1 minute or less.

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