JPH05119268A - Monochromatic telescope optical system - Google Patents

Abstract

PURPOSE:To obtain a monochromatic telescope optical system which accurately calibrates the light intensity distribution of the monochrome image of an infinity object by detecting the irregularity of intensity caused by an optical system for making an image monochrome and an image pickup device. CONSTITUTION:A calibration optical system 2 is attachably detachably arranged between an objective optical system 1 and the optical system 3 for making the image monochrome, and it is inserted in an optical path at the time of calibration and retreated to the outside of the optical path at the time of observing. The optical system 2 is provided with an aperture-stop to form the image of the infinity object at the position of the aperture-stop. The position and the size of the exit pupil of the single objective optical system 1 are coincident with those of the exit pupil of the synthetic system of the optical systems 1 and 2. A white image by the optical system 1 (synthetic system of the optical systems 1 and 2 at the time of calibration) is made monochrome by the optical system 3 and the monochrome image is picked up by an image pickup device 4.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical system of a monochromatic telescope used for observing a monochromatic image of a sufficiently large infinite object which has a substantially uniform luminance distribution and can be regarded as an almost perfect diffusing surface. is there.

[0002]

2. Description of the Related Art An optical system of a conventional monochromatic telescope has a structure as shown in FIG. In FIG. 2, a white image of an object at infinity is formed by the objective optical system 1, and the white image is monochromaticized by the monochromatic optical system 2 and re-imaged on the imaging surface of the imaging device 4. Then, a monochromatic image of the object at infinity is captured by the image capturing device 4.

[0003]

However, in the conventional monochromatic telescope optical system as described above, the sensitivity unevenness of the image pickup device when picking up an image of an object at infinity, the transmittance unevenness of the monochromatic optical system, and the monochromatic conversion. Due to the influence of interference fringes and the like caused by the internal reflection of the optical system and the reflection on the image pickup surface of the image pickup apparatus, there is a problem in that the picked-up monochromatic image has intensity unevenness that is not originally present in an infinite object.

The present invention has been made in view of the above circumstances, and a monochromatic telescope optical system capable of measuring the intensity unevenness of a monochromatic image caused by a member constituting an optical system to calibrate the intensity unevenness. It is intended to provide.

[0005]

SUMMARY OF THE INVENTION A monochromatic telescope optical system of the present invention comprises an objective optical system for forming an image of an object at infinity and a monochromatic image for re-imaging the image formed by the objective optical system. In order to achieve the above-mentioned object, the following conditions are provided between the objective optical system and the monochromatic optical system, and an imaging unit that captures a monochromatic image by the monochromatic optical system. A calibration optical system satisfying the above conditions is removably arranged. (a) The calibration optical system has an aperture stop. (b) An image of the object at infinity is formed at the position of the aperture stop of the calibration optical system. (c) The exit pupil of the combined system of the objective optical system and the calibration optical system in the state where the calibration optical system is arranged has the same position and size as the exit pupil of the objective optical system alone.

[0006]

FIG. 1 is an optical path diagram showing the basic construction of the monochromatic telescope optical system according to the present invention. In FIG. 1, the objective optical system 1, the monochromatic optical system 3, and the image pickup device 4 are provided in the same manner as in the conventional configuration, but the telescope optical system of the present invention includes the objective optical system 1 and the monochromatic optical system 3. A calibration optical system 2 that satisfies the above conditions (a) to (c) is provided between them, and is retracted outside the optical path by a retracting device 5 as needed.

Next, FIG. 3 is an optical path diagram showing an optical path during observation of the monochromatic telescope optical system according to the present invention. At the time of observation, the calibration optical system 2 is retracted out of the optical path by the retracting device 5 as shown in the figure, and the white image Iwo of the object at infinity is intermediately imaged by the objective optical system 1, and the monochromatic optical The system 3 forms the monochromatic image Imo of the white image Iwo, and the imaging device 4 captures the monochromatic image Imo. At this time, the shape of the light flux from the objective optical system 1 to the white image Iwo is determined by the exit pupil Pex of the objective optical system 1, as shown in FIG.

Next, at the time of calibration, the retracting device 5 inserts the calibration optical system 2 into the optical path (state of FIG. 1). Calibration optical system 2 when the calibration optical system 2 is inserted as described above
Since the exit pupil of the combined system of the objective optical system 1 and the exit pupil Pex of the objective optical system 1 alone have the same position and size, the two will not be distinguished hereinafter.

FIG. 5 shows a light beam that passes through a combined system of the objective optical system 1 and the calibration optical system 2 during calibration. In FIG. 5, an image Iwc by the combining system is assumed at the same position as the image Iwo at the time of observation (FIG. 3). Statue Iwc
Since the shape of the light flux that forms an image on (1) is determined by the exit pupil Pex, it coincides with the light flux that forms on the white image Iwo during observation.

Therefore, the shapes of the light fluxes passing through the monochromatic optical system 3 and reaching the image pickup device 4 also match during observation and calibration, and the monochromatic optical system for the monochromatic image picked up by the image pickup device 4 is obtained. It can be said that the influences of 3 and the imaging device 4 are equal at the time of observation and at the time of calibration.

As shown in FIG. 6, an image Iso of an object at infinity is formed on the aperture stop Sac of the calibration optical system 2. Therefore, when viewed from the image Iwc side, an image of the image Iso can be formed on the exit pupil Pex. That is, an image Ipo of an object at infinity is formed on the exit pupil Pex. Since it is assumed that an object at infinity has a substantially uniform luminance distribution and has a sufficiently large spread that can be regarded as an almost perfect diffusing surface, the image Ipo on the exit pupil Pex also has a substantially uniform luminance distribution. It may be considered that the light is almost omnidirectional within the range of the light beam incident on the monochromatic optical system 3 and covers the entire exit pupil Pex. That is, at the time of calibration, it can be said that ideal illumination without unevenness is provided at the position of the white image Iwc.

Therefore, the unevenness in the intensity of the image picked up by the image pickup device 4 at the time of calibration can be treated as being generated by the monochromatic optical system 3 and the image pickup device 4 itself, and the image signal (from the image pickup device 4 at the time of calibration ( The intensity unevenness itself generated by the monochromatic optical system 3 and the image pickup device 4) is multiplied by an appropriate coefficient and subtracted from the image signal at the time of observation to obtain an observed image signal in which the intensity unevenness is calibrated. As described above, in order to make the combined exit pupil of the objective optical system 1 and the calibration optical system 2 and the exit pupil of the objective optical system 1 substantially coincide with each other, the following condition (1) is satisfied. It is desirable to be satisfied. (1) f _c ≤ (2f ₀ ² tan ω ₀ ) / φ ₀ where f _c : focal length of calibration optical system 2, f ₀ : focal length of objective optical system 1, ω ₀ : apparent infinity object In, the actual viewing angle by the radius of the circle when the diameter is maximum among the assumed circles touching inside of it (for example, if the apparent infinity object is a circle, the angle at which the radius is actually viewed) , Φ ₀ : the maximum diameter of the entrance pupil of the objective optical system 1. If the entrance pupil is circular, its diameter is the maximum, and if the entrance pupil is non-circular, the maximum diameter of the diameters passing through the center of the entrance pupil. The diameter is. If this condition (1) is not satisfied, the size of the combined exit pupil of the objective optical system 1 and the calibration optical system 2 will be smaller than the exit pupil of the objective optical system 1, and the size (shape) of both will be reduced. Difficult to match. Furthermore, in order to simply configure the calibration optical system 2, it is more desirable to satisfy the following condition (2). _{(2) Bfc <f 0/} 5 However, BFC: from the most image side surface of the optical calibration system 2 in a state in which the optical calibration system 2 is arranged to space the white image formed by the objective optical system 1 (intermediate image) position Axial distance, f ₀ : focal length of the objective optical system 1. If the condition (2) is not satisfied, the refracting power of the calibration optical system 2 will become strong. Therefore, in order to satisfactorily correct various aberrations,
There is no choice but to increase the number of lens components. Therefore, the calibration optical system 2 becomes complicated and large in size, which is not preferable.

[0013]

【Example】

Example 1 A monochromatic telescope optical system for solar observation according to Example 1 of the present invention will be described with reference to FIGS. 7, 8 and 9. Figure 7
8 and FIG. 8 are optical path diagrams showing the configuration of the optical system at the time of observation and calibration of this embodiment, respectively, and FIG. 9 is a schematic perspective view of the monochromatic telescope optical system according to this embodiment.

First, the structure of the optical system during observation will be described.
In FIG. 7, the objective optical system 1 comprises an aperture stop 1a and an objective lens 1b.
o is formed in front of the monochromatic optical system 3. The monochromatic optical system 3 is composed of a field lens 3a, a filter 3b, and a relay lens 3c, monochromates the sun white image Iwo, and forms a monochromatic image Imo of the sun on an imaging surface of an imaging device (not shown).

The calibration optical system 2 in this embodiment comprises a first lens 2a, an aperture stop 2b and a second lens 2c, and is mounted on a rotary stage 5a as shown in FIG. The rotating stage 5a is rotatable about an axis orthogonal to the optical axis of the telescope, and during observation (Fig. 7),
The calibration optical system 2 is fixed so that its optical axis is orthogonal to the optical axis of the telescope, and is removed from the optical path. It goes without saying that, in FIG. 7, there is a space between the first lens 2a and the aperture stop 2b of the calibration optical system 2 so that the light beam from the objective optical system 1 cannot be blocked.

The data (R: radius of curvature, D: distance to next surface, n: refractive index) of each surface in the optical system at the time of observation described above are shown. The object plane at the time of observation is at infinity.
In Table 1, the first surface is the aperture stop 1a (φ = 4) of the objective optical system 1.
8.73458 circular opening), second side and third side
The surface is the objective lens 1b (plano-convex lens), and the fourth surface is the white image I.
wo, the fifth and sixth surfaces are field lenses 3a (plano-convex lenses) of the monochromatic optical system 3, the seventh and eighth surfaces are monochromatic filters 3b, and the ninth to tenth surfaces are relay lenses 3c.
These are surfaces that form (convex lens + concave lens).

Next, the structure of the optical system during calibration will be described. At the time of calibration, the calibration optical system 2 is rotated counterclockwise by the rotary stage 5a in the inner surface of the paper of FIG. 7, and is fixed at a position coaxial with the optical axis of the telescope, as shown in FIG. In FIG. 8, a white image Iwc is formed at the same position as the white image Iwo at the time of observation by the combination system of the objective optical system 1 and the calibration optical system 2 (details will be described later), and this white image is formed by the monochromatic optical system 3. It is converted into a monochromatic image and is re-imaged as a monochromatic image Imc.

Data of each surface in the optical system during calibration (R: radius of curvature, D: distance to next surface, n: refractive index)
Is shown in Table 4. In Table 4, the first to third surfaces are the objective optical system 1, the fourth and fifth surfaces are the calibration system first lens (plano-convex lens), and the sixth surface is the calibration system aperture stop 2b (φ = 3.096). Of the calibration system second lens 2c (convex lens), the ninth surface is a white image Iwc, and the tenth surface is a tenth surface.
Surfaces to 16 are surfaces constituting the monochromatic optical system 3, respectively.

In this embodiment, in the optical system at the time of calibration (FIG. 8), the object plane is located behind the first surface (on the side of the image sensor).
An imaginary plane Ip is assumed at a position of 1165.7 mm. This virtual plane Ip is a plane which is directed toward the center of the sun and is uniformly illuminated by the sun. In the optical system of FIG. 8, the virtual plane Ip can be considered as a secondary light source. The virtual plane Ip is conjugated with the image Iwc by the objective lens 1b, the calibration system first lens 2a, and the calibration system second lens 2c.

Next, the results of ray tracing during observation and calibration will be described. The initial values of the four rays traced are shown in Table 2 (at the time of observation) and Table 5 (at the time of calibration), and the ray tracing results are shown in Table 3 (at the time of observation) and Table 6 (at the time of calibration).
Shown in. The rays 1 to 4 in Tables 2 and 5 correspond to each other one-to-one, and the ray 1 is a marginal ray that passes through the edge of the exit pupil and forms an image on the optical axis, and the ray 2 is a monochromatic image Imo or Im.
It represents the chief ray of a light beam having an image height of 6 mm on c. Ray 3
And 4 represent the marginal ray attached to the ray 2.

In Table 6 (at the time of calibration), focusing on the ray 2, the ray intersects the optical axis on the sixth surface. The ray 2 has an initial value parallel to the optical axis as shown in Table 5. Therefore,
An image of an object at infinity, that is, a sun image is formed on the sixth surface. Since the sixth surface is the calibration system aperture stop 2b, a sun image is formed on the exit pupil of the objective optical system 1 when viewed from the image Iwc. It is considered that the sun image has a substantially uniform luminance distribution and has almost no directivity inside the light flux. Further, the visual radius of the sun is 0.2 with respect to the magnitude of the angle of inclination of the initial values of the light rays 1 to 4 shown in Table 5 with respect to the optical axis is 0.2017125 °.
It is 62 ° or more, which can be said to be sufficiently large for the optical system of the present embodiment. Therefore, at the time of calibration, it can be considered that the position of the image Iwo is uniformly illuminated as a reference.

Among the corresponding surfaces in Table 3 (at the time of observation) and Table 6 (at the time of calibration), particularly the fourth surface of Table 3 (white image Iw)
o) and the ninth surface (white image Iwc) of Table 6, and the combination of the fifth surface of Table 3 and the tenth surface of Table 6. These are a set of the white intermediate images Iwo and Iwc and the field lens 3 a of the monochromatic optical system 3. From the data shown in the table, it can be seen that all of the rays 1 to 4 pass through at the same image height during observation and during calibration. The fact that the two principal rays 2 pass through the same position indicates the coincidence of the exit pupil positions.
The fact that the two marginal rays of rays 1, 3, and 4 pass through the same position indicates that the exit pupil diameters match. Since the configurations of the optical systems after the monochromatic optical system 3 are exactly the same at the time of observation and at the time of calibration, the monochromatic optical system 3,
Naturally, the paths of the light rays in the image pickup device 4 are the same. Therefore, the effects of the monochromatic optical system 3 and the imaging device 4 are the same during observation and during calibration.

However, if the monochromatic image Imc is imaged with the calibration optical system 2 inserted (FIG. 8), the monochromatic optical system 3 is obtained.
Also, it is possible to detect the intensity unevenness caused by the image pickup device 4, and thus it is possible to calibrate the intensity unevenness of the monochromatic image Imo imaged at the time of observation (the calibration optical system 2 is retracted).

[0024]

[Table 1]

[0025]

[Table 2]

[0026]

[Table 3]

[0027]

[Table 4]

[0028]

[Table 5]

[0029]

[Table 6]

Second Embodiment A monochromatic telescope optical system for observing the sun according to a second embodiment of the present invention will be described with reference to FIGS. 10, 11, and 12. 10 and 11 are optical path diagrams showing the configuration of the optical system at the time of observation and calibration of this embodiment, respectively, and FIG. 12 is a schematic perspective view of the monochromatic telescope optical system according to this embodiment. The points that are the same as those of the first embodiment will be briefly described.

First, the structure of the optical system during observation will be described.
In FIG. 10, the objective optical system 11 comprises an aperture stop 11 a and an objective lens 11 b, and the objective optical system 11 forms a solar white image Iwo in front of the monochromatic optical system 13.
The monochromatic optical system 13 includes a collimator lens 13a, a filter 13b, and an imaging lens 13c, and the solar white image Iw.
o is monochromatic to form a monochromatic image Imo of the sun on the imaging surface of the imaging device (not shown). The monochromatic optical system 13 in this embodiment is a parallel system.

Further, the calibration optical system 2 includes the first lens 12
a, an aperture stop 12b, and a second lens 12c.
It is fixed on the translation stage 15 as shown in FIG. The translation stage 15 can move forward and backward in a direction orthogonal to the optical axis of the telescope, and at the time of observation (FIG. 10), the calibration optical system 12 is fixed while retracted from the optical path of the telescope.

Table 7 shows data (R: radius of curvature, D: distance to next surface, n: refractive index) of each surface in the optical system at the time of observation described above. The object plane at the time of observation is at infinity. In Table 7, the first surface is the aperture stop 11 of the objective optical system 11.
a (having a circular aperture of φ = 30), the second surface to the fourth surface are the objective lens 11b (convex lens + concave lens), the fifth surface is the white image Iwo, and the sixth surface to the eighth surface are the monochromatic optical system 13. Collimator lens 13a (concave lens + convex lens), the ninth and tenth surfaces are monochromatic filters 13b, and eleventh to thirteenth surfaces.
The surfaces are the surfaces forming the imaging lens 13c (convex lens + concave lens), respectively.

Next, the structure of the optical system during calibration will be described. During calibration, the calibration optical system 12 is translated by the translation stage 15 and is fixed at a position coaxial with the optical axis of the telescope, as shown in FIG. In FIG. 11, a white image Iwc is formed at the same position as the white image Iwo at the time of observation by the combined system of the objective optical system 11 and the calibration optical system 12, and the white image Iwc is the monochromatic optical system 1.
In FIG. 3, the image is monochromatic and is re-imaged as a monochromatic image Imc.

Data of each surface in the optical system during calibration (R: radius of curvature, D: distance to next surface, n: refractive index)
Is shown in Table 10. In Table 10, the first to fourth surfaces are the objective optical system 11, and the fifth and sixth surfaces are the calibration system first lens 12a.
(Concave lens), 7th surface is calibration system aperture stop 12b, 8th and 9th surfaces are calibration system 2nd lens 12c (convex lens), 10th surface is white image Iwc, 11th to 18th surfaces are monochromatic These are surfaces that respectively configure the optical system 13.

In this embodiment, the optical system at the time of calibration (FIG. 11)
In, the imaginary plane Ip is assumed as the object plane at a position of 190.85 mm forward (sun side) from the first surface. The virtual plane Ip is imaged by the objective lens 11b, the calibration system first lens 12a, and the calibration system second lens 12c.
It is conjugated with c.

Next, the results of ray tracing performed during observation and calibration will be described. The initial values of the four rays traced are shown in Table 8 (at the time of observation) and Table 11 (at the time of calibration), and the ray tracing results are shown in Table 9 (at the time of observation) and Table 12 (at the time of calibration). The method of selecting the four light rays of the light rays 1 to 4 is the same as that in the first embodiment, and the light ray 2 represents the chief ray of the light flux having an image height of 5 mm on the monochromatic image Imo or Imc.

In Table 12 (at the time of calibration), focusing on the ray 2, it intersects the optical axis on the seventh surface (calibration system aperture stop 2b). As shown in Table 11, ray 2 has an initial value parallel to the optical axis. Therefore, it can be said that an object image at infinity, that is, a sun image is formed on the seventh surface. That is, when viewed from the image Iwc, a sun image is formed on the exit pupil of the objective optical system 11. Further, the magnitude of the inclination of the initial values of the light rays 1 to 4 shown in Table 11 with respect to the optical axis is 0.24090 °,
It can be said that the sun (visual radius 0.262 ° or more) is sufficiently large for the optical system of this embodiment. Therefore, at the time of calibration, it can be considered that the position of the image Iwc is uniformly illuminated as a reference for calibration.

Table 9 (at the time of observation) and Table 12 (at the time of calibration)
Among the corresponding surfaces of No. 5, particularly, the fifth surface of Table 9 and the tenth surface of Table 12 (white images Iwo and Iwc), the sixth surface of Table 9 and Table 1
Focusing on the second set of the eleventh surface (the first surface of the collimator lens 13a), it can be seen that all of the light rays 1 to 4 pass at substantially the same image height during observation and during calibration. This means that the exit pupil of the objective optical system 11 alone at the time of observation and the exit pupil of the combined system of the objective optical system 11 and the calibration optical system 12 at the time of calibration match in position and size. Also in the present embodiment, since the configurations of the optical systems after the monochromatic optical system 13 are exactly the same at the time of observation and at the time of calibration, the directions of the rays of light in the monochromatic optical system 13 and the imaging device 14 are the same,
The effects of the monochromatic optical system 13 and the imaging device 14 are the same during observation and during calibration.

From the above, it is clear that the optical system of Example 2 can also detect the intensity unevenness caused by the monochromatic optical system 13 and the image pickup device 14 to calibrate the solar monochromatic image at the time of observation. is there.

[0041]

[Table 7]

[0042]

[Table 8]

[0043]

[Table 9]

[0044]

[Table 10]

[0045]

[Table 11]

[0046]

[Table 12]

[0047]

As described above, according to the present invention, since the calibration optical system satisfying a specific condition is removably disposed between the objective optical system and the monochromatic optical system, the infinity imaged at It is possible to quantitatively detect the intensity unevenness caused by the imaging device and the monochromatic optical system among the intensity unevenness generated in the object monochromatic image, and it is possible to accurately calibrate the light intensity distribution on the object monochromatic image at infinity. Become. Further, since the calibration optical system can be easily inserted into and removed from the optical path by an appropriate retracting means,
It is possible to perform high-frequency calibration during a series of observations, which is very advantageous in improving observation accuracy.

[Brief description of drawings]

FIG. 1 is an optical path diagram showing a basic configuration of a monochromatic telescope optical system according to the present invention.

FIG. 2 is an optical path diagram showing a basic configuration of a conventional monochromatic telescope optical system.

FIG. 3 is an optical path diagram for explaining an optical path during observation of the monochromatic telescope optical system in FIG.

FIG. 4 is an explanatory diagram for explaining a shape of a light beam when the monochromatic telescope optical system in FIG. 1 is observed.

5A and 5B are explanatory views for explaining the shape of a light beam when the monochromatic telescope optical system in FIG. 1 is calibrated.

6 is an optical path diagram for explaining an optical path during calibration of the monochromatic telescope optical system in FIG.

FIG. 7 is an optical path diagram showing a configuration of a monochromatic telescope optical system according to Example 1 of the present invention during observation.

FIG. 8 is an optical path diagram showing a configuration during calibration of the monochromatic telescope optical system in the first embodiment of the present invention.

FIG. 9 is a schematic perspective view of a monochromatic telescope according to the first embodiment of the present invention.

FIG. 10 is an optical path diagram showing a configuration at the time of observation of the monochromatic telescope optical system in the second example of the present invention.

FIG. 11 is an optical path diagram showing a configuration at the time of calibration of the monochromatic telescope optical system in the second embodiment of the present invention.

FIG. 12 is a schematic perspective view of a monochromatic telescope according to a second embodiment of the present invention.

[Explanation of symbols]

 1, 11 Objective optical system 2, 12 Calibration optical system 2a, 12a Calibration system first lens 2b, 12b Calibration system aperture stop 2c, 12c Calibration system second lens 3,13 Monochromatic optical system 3a Field lens 13a Collimator lens 3b, 13b Monochromatic filter 3c Relay lens 13c Imaging lens 4,14 Imaging device 5 Rotating stage 15 Translation stage

Claims (1)

[Claims] 1. An objective optical system for forming an image of an object at infinity, a monochromatic optical system for monochromatically re-imaging an image formed by the objective optical system, and a monochromatic image by the monochromatic optical system. In a monochromatic telescope optical system having an image pickup means for picking up an image, a calibration optical system satisfying the following conditions is removably arranged between the objective optical system and the monochromatic optical system. Monochromatic telescope optics. (a) The calibration optical system has an aperture stop. (b) An image of the object at infinity is formed at the position of the aperture stop of the calibration optical system. (c) The exit pupil of the combined system of the objective optical system and the calibration optical system in the state where the calibration optical system is arranged has the same position and size as the exit pupil of the objective optical system alone.