Telescope system

Abstract

To measure a geometric relation between one side of an optical conjugate relation of a telescope optical system recognized as an observation visual field of a telescope and the other side of the conjugate relation recognized as a detector, a light source or the like in six degrees of freedom of translation and rotation, to specify an observation visual field direction in real time, and to contribute to improvement of definition of an image obtained by the telescope.SOLUTION: A light flux from an observation field of view or the like and a light flux emitted from a light source disposed around a detector are integrated on the same optical path using an optical element such as a cross prism, and both light fluxes are superimposed and photographed. By comparing the captured image with an arrangement pattern of an object (for example, a fixed star) whose coordinates are known, a coordinate system (for example, a celestial sphere coordinate system) to which an observation target belongs is directly associated with a detector coordinate system.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to telescopes, and more particularly to a technique for determining the observation field of a space telescope or the pointing direction of an optical communication telescope, for example. [Background technology]

[0002] Space telescopes are one type of telescope that form an image of an object to be observed or aimed at, and are used for a variety of purposes. A space telescope is an astronomical telescope launched into space, such as in satellite orbit, and can observe celestial bodies without being obstructed by the Earth's atmosphere, and without being affected by the absorption, emission, and scattering of electromagnetic waves by the atmosphere. Gamma rays, X-rays, ultraviolet rays, and far-infrared rays are absorbed by the atmosphere, making them difficult to observe from the ground, but by placing a telescope outside the atmosphere, observations can be made without being obstructed by the atmosphere. Another major advantage is that the image is not distorted by atmospheric flow.

[0003] For example, X-ray telescopes are instruments used to observe various X-ray celestial bodies in space, such as supernova remnants, high-temperature gas in galaxy clusters, black holes, and neutron stars. X-ray telescopes use grazing incidence mirrors, which cause X-rays to be totally reflected by an extremely smooth metal surface at a shallow angle. In the X-ray region, the refractive index of metal is lower than that of a vacuum, so if X-rays are incident on a smooth metal surface at an angle shallower than the critical angle, the X-rays will be totally reflected from the surface, and it is possible to focus the X-rays by adjusting the geometric shape of the metal surface. A grazing incidence X-ray telescope consists of a reflector that focuses X-rays and a two-dimensional X-ray detector that detects X-rays at its focal plane. Large X-ray space telescopes operated on satellites can have focal lengths of over 10 m. In order to fit such large telescopes into the fairing of the launch vehicle, an extension mechanism is often used for the structure connecting the X-ray mirror and the X-ray detector. In this case, after launch, the folded extension structure is deployed in orbit and then used for observations.

[0004] The instantaneous field of view of an X-ray telescope using an extendable structure changes constantly due to not only the uncertainty of the satellite bus's attitude but also the geometric fluctuations of the structure in orbit and thermal distortion due to sunlight. Because the observation time required to acquire one X-ray data frame is significantly longer than the temporal stability of the instantaneous field of view, if the photons reaching the X-ray detector were simply integrated as image data, the fluctuations in the instantaneous field of view would manifest themselves as image blur, resulting in a significant reduction in the spatial discrimination of the image. Therefore, the X-ray detector is, for example, an area-type photon counter array, which measures the position and time at which X-ray photons arrive at each pixel address. The X-ray observation data obtained in this way are then superimposed after the end of the observation period, with corrections made to account for the variations in the instantaneous field of view direction at the time of each photon's arrival, improving the spatial discrimination of the image. This process is called X-ray image reconstruction.

[0005] As an example, the X-ray astronomy satellite ASTRO-H employs the CAMS (Canadian AstroH Metrology system), a system designed to measure the relative displacement between the X-ray mirror and detector, and estimates the instantaneous field of view of the X-ray telescope from the measurement results via a structural model to reduce positional instability associated with the superposition of image data. However, this method cannot directly measure the uncertainty of the absolute imaging position due to structural deformation of the satellite body to which the extendable structure is attached (see, for example, Non-Patent Document 1), nor can it address the uncertainty of the X-ray focusing position due to deformation of the X-ray mirror itself or the satellite's pointing detection and control limits.

[0006] For astronomical telescopes deployed on the ground, a known method for imaging a celestial body is to first introduce the target celestial body into the field of view of the telescope, and then, while imaging the celestial body, rotate the telescope mount in two orthogonal axes to track (guide) the target celestial body so as to cancel out the movement of the target celestial body due to its diurnal motion. Patent Document 1 discloses an astronomical telescope that uses a beam splitter placed between the objective lens and a cooled CCD to guide a portion of the light beam to an image sensor for autoguiding, and states that the telescope is applicable to the infrared, ultraviolet, and X-ray regions in addition to the visible region.

[0007] In a space telescope that is mounted on an artificial satellite or the like and used for observation, a total of six degrees of freedom consisting of translation and rotation are maintained without mechanical constraints, so there are limits to the applicability of the technology described in Patent Document 1 to space telescopes. Furthermore, in a long-focus telescope with a focal length of more than 10 m, i.e., a narrow-field telescope, the assumption that a visible light source object suitable for tracking actually exists around a target celestial object such as an X-ray source does not always hold true, so in this respect as well, there are limits to the applicability of the technology described in Patent Document 1 to space telescopes.

[0008] Patent Document 2 discloses a cross prism as an optical element that combines optical paths. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] Luigi C. Gallo et al, In-flight performance of the Canadian Astro-H Metrology System, Journal of Astronomical Telescopes, Instruments, and Systems 4(2), 021405(2018) [Patent documents]

[0010] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-102914 [Patent Document 2] Patent No. 7446648 Summary of the Invention [Problem to be solved by the invention]

[0011] In particular, in observation systems where the relative geometric positional relationship between the mirror used for focusing light and the detector that detects photons is time-indeterministic over the observation period, as is the case with large X-ray telescopes with long apex distances, there is a problem of reduced image resolution due to the fact that the instantaneous field of view changes from moment to moment during the observation period.

[0012] Furthermore, in space telescopes that observe wavelength ranges other than X-rays, such as infrared, visible light, and ultraviolet, as well as in other imaging optical instruments, if the relative geometric relationship between the optical system that forms the image of the subject and the detector lacks stability, similar problems to those encountered with large X-ray telescopes will arise.

[0013] Therefore, the present invention aims to measure the geometric relationship between one side of the optical conjugate relationship recognized as the observation field of view and the other side of the conjugate relationship recognized as a detector, light source, etc. in the optical system of a telescope in terms of six degrees of freedom (translation and rotation), identify the observation field of view direction in real time, and contribute to improving the resolution of images, etc. [Means for solving the problem]

[0014] The present invention is characterized by quantitatively identifying the field of view by uniquely associating the coordinate system in which the observation target (e.g., a celestial coordinate system) and the detector coordinate system without being affected by external or internal disturbances. A bundle of rays emitted from a light source (e.g., any celestial body, including but not limited to a specific celestial body) in the coordinate system to which the observation target (e.g., a specific celestial body) belongs and a bundle of rays emitted from light sources arranged around the detector are integrated onto the same optical path using an optical element such as a cross prism, and the two bundles of rays are superimposed to obtain an image in which they are superimposed. This system, which uniquely associates the coordinate system of the observation target (e.g., celestial coordinates) and the detector coordinate system by comparing the captured image with the arrangement pattern of an object (e.g., a star) whose coordinates are known, can be called a field of view direction vector detection system.

[0015] The deviation of the field of view pointing vector, detected by geometric matching between an object with known coordinates located in the coordinate system to which the observation object belongs and the field of view of the detector mapped to that coordinate system, from the desired observation reference orientation may be fed back to the attitude control system of the satellite carrying the telescope, or in the case of a large X-ray telescope, may be used as a positional offset for each image when overlaying X-ray data obtained in orbit onto a single image in the post-processing process of constructing an X-ray image.

[0016] A single set of telescopes may be used to point at an observation target, or a telescope array may be formed by using multiple telescopes simultaneously in parallel. In a telescope array, if the field of view of the detector mapped onto the celestial coordinate system is specified for each telescope constituting the telescope, the relative positional relationship of the observation field of each telescope is quantified, and images are synthesized to cancel out any difference from a reference pointing direction commonly determined for the entire array, then even if the optical aperture size of each individual telescope is small, the synthetic optical system consisting of all the multiple telescopes constituting the telescope array can realize a large synthetic aperture as a whole, and since each of these telescopes shares a field of view with each other, the entire telescope having such a synthetic optical system will be effectively bright. Since the array functions as a single telescope with a large aperture ratio, it contributes to improving the ability to detect low-luminosity objects. X-ray telescopes typically have a low aperture ratio due to the use of grazing incidence mirrors, but such a telescope array provides a technical solution to overcome this difficulty. Furthermore, with a telescope array, it is even possible to construct an optical system that is bright enough to be exempt from the Abbe's sine condition of a single telescope while suppressing the occurrence of aberrations.

[0017] In a telescope array in which multiple telescopes are directed so that they each share at least a portion of the field of view of adjacent telescopes, it is possible to realize a wide-angle X-ray telescope, which is generally technically difficult to achieve due to the properties of X-ray mirrors. The field-of-view pointing vector detection system is suitable for quantifying the amount of correction when overlapping the fields of view of such telescopes. Furthermore, multiple targets may be observed simultaneously by independently pointing any multiple fields of view of each telescope without overlapping each other. In this case, the field-of-view pointing vector detection system is also suitable for quantifying the relationship between each independent field-of-view pointing vector.

[0018] The above-mentioned characteristics of a telescope array, which can specify a field of view and synthetically realize a large aperture or a wide field of view, can be developed into a flexible array telescope system in which synthetic apertures and synthetic fields of view can be interchanged by providing, for example, a mechanical stage to arbitrarily set the nominal pointing direction of each telescope. [Effects of the Invention]

[0019] The present invention has the function of uniquely associating a coordinate system (e.g., a celestial coordinate system) to which an object to be observed belongs with a detector coordinate system. Therefore, even if temporary geometric distortion occurs in the telescope optical system, causing light to no longer be focused at a nominal image point, or if the geometric relationship between the optical system and the detector that constitutes the telescope fluctuates over time, the present invention has the effect of detecting fluctuations in each instantaneous field of view caused by these disturbances in real time, using this information as satellite attitude control information, and maintaining high spatial discrimination ability in images obtained by superimposing or combining multiple pieces of data acquired over a period significantly longer than the time constant of these disturbances. The quantitative function of the field-pointing vector of the present invention is effective in realizing a telescope array that synthetically achieves a large aperture and a wide field of view, as well as a flexible and integrated observation device that allows interchangeability between synthetic aperture and synthetic field of view. [Brief explanation of the drawings]

[0020] [Figure 1] 1 is a schematic configuration diagram of an X-ray telescope system according to a first embodiment of the present invention. [Figure 2] FIG. 10 is a perspective view showing an example of the configuration of a cross prism. [Figure 3] FIG. 10 is a front view of the cross prism for explaining that the prisms constituting the cross prism are defined as first to fourth spaces of the cross prism. [Figure 4] 10 is a diagram showing the normal light path of incident light entering from the first space and the third space, reflected only once in the cross prism, and emitted from the second space. FIG. [Figure 5] 10 is a diagram showing an example of a stray light path in which incident light entering from the third space is reflected two or more times within the cross prism and emitted into the second space. FIG. [Figure 6] 10A and 10B are diagrams showing examples of the arrangement of light-absorbing prisms in a cross prism. [Figure 7] FIG. 10 is a diagram showing an example in which a light absorbing film is vapor-deposited on a cross prism. [Figure 8] FIG. 10 is a diagram for explaining a method for identifying the coordinates of a detector in celestial coordinates. [Figure 9] FIG. 2 is a diagram illustrating a first example of the arrangement of light sources. [Figure 10] FIG. 10 is a diagram illustrating a second example of the arrangement of light sources. [Figure 11] FIG. 10 is a diagram illustrating a third example of the arrangement of light sources. [Figure 12] FIG. 10 is a side view of a third example of the arrangement of light sources. [Figure 13] FIG. 10 is a diagram showing an example of an image captured by a photodetector. [Figure 14] FIG. 10 shows the change in instantaneous position of the detector in celestial coordinates. [Figure 15] This is a diagram showing how the functions of a large aperture telescope and a wide-angle telescope can be realized using multiple telescopes. [Figure 16] FIG. 1 shows how simultaneous observation of multiple regions can be achieved using multiple telescopes. DETAILED DESCRIPTION OF THE INVENTION

[0021] Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings. Note that the items described in the following embodiments are merely examples and are not intended to limit the scope of the present invention. Furthermore, items not described in the embodiments have not been intentionally excluded.

[0022] The following description will be given taking an X-ray telescope, which is one form of space telescope, as an example. FIG. 1 shows a schematic configuration of an X-ray telescope system according to a first embodiment of the present invention. The X-ray telescope 1 is a Wolter I-type grazing incidence telescope. It includes multiple reflecting mirrors 2a-1 to 2a-3, 2b-1 to 2b-3, and a two-dimensional X-ray detector 3 (hereinafter referred to as "detector 3") for detecting X-ray images. The detector 3 is, for example, an array element sensitive to X-rays and operating in photon counting mode. A light source 4 is installed at a predetermined position around the detector 3. In addition, a cross prism 5 is arranged on the optical path of the multiple reflecting mirrors 2a-1 to 2a-3 as an optical element that combines light beams from two opposing directions and emits them from a surface different from the entrance surface. The light beams branched by the cross prism 5 are focused by a condenser lens system 6 and captured by a photodetector 7. The photodetector 7 is, for example, a CCD image sensor or a CMOS image sensor. The data captured by the photodetector 7 is sent to a processing device 8. Based on the data captured by the photodetector 7, the processing device 8 determines the field of view in which the detector 3 observes the celestial sphere through the telescope. The image construction device 9 is a processing system that reconstructs an X-ray image from the data detected by the detector 3, and reconstructs the X-ray image by taking into account information on the observation field of view in celestial coordinates obtained by the processing device 8.

[0023] Reflecting mirrors 2a-1 to 2a-3 and 2b-1 to 2b-3 are cylindrical mirrors and are arranged concentrically. Furthermore, reflecting mirrors 2a-1 to 2a-3 and reflecting mirrors 2b-1 to 2b-3 are arranged in a nested manner. X-rays emitted by celestial body 10 are reflected by reflecting mirror 2a-1, reflected again by reflecting mirror 2b-1, and directed to the focal plane. Similarly, X-rays reflected by reflecting mirrors 2a-2 and 2a-3 are reflected again by reflecting mirrors 2b-2 and 2b-3, respectively, directed to the focal plane, and detected by detector 3.

[0024] Light arriving from a celestial object whose coordinates on the celestial sphere are known is reflected by cross prism 5 and directed toward condensing lens system 6. Light emitted from light source 4 located around detector 3 is reflected by reflecting mirrors 2b-1 to 2b-3 and 2a-1 to 2a-3, and then by cross prism 5 and directed toward condensing lens system 6. In other words, cross prism 5 combines the light beams from the celestial object whose coordinates are known and the light beam from light source 4. In this example, a cross prism is shown as an example of an optical element that has the function of combining the light beams from the celestial object whose coordinates are known and the light beam from light source 4, but optical elements other than a cross prism may also be used. The light beams combined by cross prism 5 are imaged by condensing lens system 6. Photodetector 7 captures an optical image in which the light image of the celestial object whose coordinates are known and the light image of light source 4 are superimposed.

[0025] The cross prism 5 absorbs X-rays, but the degree of absorption varies depending on the wavelength of the X-rays. If the absorption is large enough to be non-negligible, the cross prism 5 will end up blocking part of the field of view of the X-ray telescope 1. Even in such a case, the size of the cross prism 5 is small compared to the aperture of the X-ray telescope 1, so the effect of blocking can be practically ignored.

[0026] Details of the cross prism 5 will be described with reference to Figs. 2 to 7. The cross prism 5 may be formed by joining four triangular prisms, each with a cross section in the shape of an isosceles right triangle, as shown in Fig. 2. An optical thin film that functions as a half mirror without wavelength selectivity (does not exhibit dichroic characteristics) is vapor-deposited on the joining surface of each prism. Details will be described later, but one of the multiple prisms is characterized by having the function of absorbing light.

[0027] For convenience in the following explanation, the four prisms will be referred to as the first space, second space, third space, and fourth space (see Figure 3). Figure 4 is a front view of the cross prism 5 shown in Figure 2, showing only the optical path of (a part of) incident light that is perpendicular to the outer surfaces of the first and third spaces of the cross prism 5, is reflected only once inside the cross prism 5, the minimum number of times, and is emitted from the second space.

[0028] Note that both cases involve reflection at the bonding surfaces of the prisms that make up the cross prism 5, and also include cases where light passes through a certain bonding surface and is then reflected by that bonding surface. Here, the optical path that is reflected only once internally and is emitted from the second space is called the "normal optical path."

[0029] 5 is a simplified diagram showing an example of the optical path of incident light from the direction of the third space, reflected two or more times inside the cross prism 5, and emitted from the second space. Such an optical path of light, reflected two or more times inside the cross prism 5, and emitted from the second space, is called a "stray light path."

[0030] Although the joint surface of the cross prism 5 is treated as a half mirror, multiple internal reflections result in the generation of multiple "stray light paths."

[0031] To address this stray light, one of the four prisms constituting the cross prism 5 is a prism with light absorption capabilities. In other words, the cross prism 5 is a rectangular cross prism formed by joining three so-called transparent prisms with one prism with light absorption capabilities. As shown in FIG. 6 , when a prism with light absorption capabilities is placed in the fourth space, the light beam entering the fourth space is absorbed. Even if multiple stray light paths are generated within the cross prism 5, the stray light is absorbed when the light path enters the fourth space. As a result, the number of light paths of the stray light exiting the cross prism 5 can be reduced. In this embodiment, all four prisms are made of a synthetic quartz-based material, and only the prism made of synthetic quartz-based material in the fourth space has light absorption capabilities.

[0032] In other embodiments of the cross prism 5, in addition to the light-absorbing prism, a light-absorbing film similar to the prism material may be applied to one surface of the second and third spaces adjacent to the fourth space, as shown in Figure 7. Furthermore, the exposed surface corresponding to the light-absorbing film may be roughened and coated with black paint. In these cases, the stray light component is scattered and diffused over a wide angular range across the entire background light, which is expected to mitigate the effects of stray light concentration that are detrimental to the detection of normal light.

[0033] Next, the light source 4 will be described in detail. The light source 4 is a point light source that emits light in the sensitivity band of the photodetector 7, and is, for example, a light-emitting diode (LED), or the output end of an optical fiber connected to an external light source. The wavelength of the light source 4 may be any wavelength to which the photodetector 7 is sensitive, and corresponds to, for example, white, red, yellow, green, blue, etc. in visible light. The photodetector 7 is, for example, a CCD image sensor or a CMOS image sensor. If the photodetector 7 is sensitive to near-infrared light, an LED that emits near-infrared light may be used as the light source 4.

[0034] Preferably, multiple light sources 4 are arranged around the detector 3, which is a two-dimensional sensor sensitive to X-rays. As shown in Figure 8, by arranging multiple light sources 4, the field of view position and angular displacement (x, y, θ) of the detector 3 relative to the celestial coordinates can be determined. It goes without saying that the light source 4 is installed with the positional relationship between the light source 4 and the detector 3 known.

[0035] 9 shows a first example of the arrangement of the light source 4. In this example, two light sources 401 and 402 are arranged on both sides of the detector 3.

[0036] 10 shows a second example of the arrangement of the light sources 4. In this example, four light sources 411 to 414 are arranged on the four sides of the detector 3.

[0037] FIG. 11 shows a third example of the arrangement of the light sources 4. In this example, three light sources are arranged near each of the four sides of the detector 3. The three light sources arranged near each side are offset in the optical axis direction, as shown in FIG. 12. The degree of enlargement of each light source image detected by the photodetector 7 is converted into a defocus amount z for the entire detector 3 using the relationship between the longitudinal magnification of the optical system, which is determined by the focal length ratio between the reflecting mirror and the focusing lens system. Furthermore, the translational component of the displacement from the nominal position of the light source image detected by the photodetector 7 is converted into translational amounts x and y of the detector 3 using the lateral magnification of the optical system. The rotational component of the positional displacement is converted into θz of the detector 3. Furthermore, the relative displacement difference between the defocus amounts corresponding to each side of the detector 3 is converted into rotational amounts θx and θy of the detector 3, thereby making it possible to detect the displacement of the detector 3 with six degrees of freedom (x, y, z, θx, θy, θz).

[0038] Next, a detailed description will be given of the processing device 8. The processing device 8 determines the observation field of view of the detector 3 relative to the celestial coordinates based on the image data acquired by the photodetector .

[0039] Since the cross prism 5 combines the bundles of rays from celestial objects whose coordinates are known with the bundles of rays from the light sources 4 arranged around the detector 3, the image captured by the photodetector 7 is, for example, as shown in Fig. 13, an image in which optical images 101-104 of celestial objects whose coordinates are known are superimposed on optical images 441, 442 of the light sources 4 (in this example, there are four celestial objects whose coordinates are known, and two light sources arranged around the detector 3). Data such as the positions (coordinates in the celestial coordinate system) and brightness (magnitude) of the celestial objects are known, and this data on the celestial objects is stored in an astronomical object catalog built into the processing device 8.

[0040] An example of the procedure for determining the conjugate position of the detector 3 in celestial coordinates will be described below. Step 1: The satellite's own attitude determination system, installed on the satellite body, directs the telescope's field of view in the direction of the observation target. The degree of field determination is sufficiently good compared to the overall field of view used for observation, but is significantly coarser than the area per pixel of the detector used for observation. Furthermore, as mentioned above, the telescope's field of view orientation exhibits time fluctuations significantly larger than the solid angle that the detector pixel subtends on the observation target surface due to disturbances inside and outside the telescope. Step 2: 1 and focused on the photodetector 7 via the condensing lens system 6, is compared with a known celestial object catalogue stored in the processing device 8, and a coordinate system conjugate to the celestial sphere facing the cross prism 5 is localized on the light-receiving surface of the photodetector 7. For the localization, a matching algorithm for the catalogue database of known celestial objects and the captured celestial object images, which has been conventionally used in star trackers as satellite attitude detection sensors commonly used in spacecraft such as artificial satellites, may be applied, but the present invention is not limited to this and does not preclude the use of new algorithms. Step 3: The bundle of rays emitted by light source 4 around detector 3 shown in Figure 1 enters the X-ray telescope, where it is collimated, and is emitted toward the observation line of sight on the celestial sphere. A portion of this bundle of rays is made to enter cross prism 5 from the surface of cross prism 5 opposite the surface onto which the bundle of rays from the celestial object enters, and is then focused onto photodetector 7 via focusing lens system 6. Assuming that the two ray-incident surfaces of the cross prism are sufficiently parallel to each other, the image point of light source 4 on photodetector 7 is obtained as the coordinates on the celestial sphere of photodetector 7 in a coordinate system that is commuterable with the celestial sphere located in step 2.

[0041] When performing step 2, the light source 4 used in step 3 may be turned off to reduce disturbances in matching the celestial object array image captured by the detector 7 with the celestial object catalog. Once the identification of the celestial object catalog has been confirmed, the accuracy of field of view identification is unlikely to decrease even if the light source 4 is turned on continuously. Therefore, steps 2 and 3 may be performed simultaneously and in parallel, and when the X-ray photons reach the detector 3, data related to the identification of the field of view direction may be recorded together with the X-ray data and time.

[0042] Next, we will explain the details of the image construction device 9. The image construction device 9 is a device that generates an X-ray image by superimposing data of each instantaneous field of view detected by the detector 3. From the unique correspondence between the celestial coordinate system and the detector coordinate system, it calculates which pixel of the detector a photon from the target celestial body 10 will be incident on, and generates a reconstructed image.

[0043] Detector 3 is an array element that operates in photon counting mode, and the position and time of the pixel that receives a photon are identified. The instantaneous field of view of the X-ray telescope changes from moment to moment due to the influence of the X-ray telescope's structural deformation, etc. As shown in Figure 15, the observation field of view of detector 3 through the telescope in celestial coordinates changes from moment to moment.

[0044] As described above, the instantaneous position of the field of view of the detector 3 in celestial coordinates is constantly measured by the processing device 8, and the position of the field of view of the detector 3 at each time is known. The image construction device 9 calculates the coordinates in the celestial coordinate system that correspond to the pixels that receive photons based on the position of the field of view of the detector 3 in celestial coordinates measured by the processing device 8, associates the celestial coordinates of the pixels that receive the photons, and generates an X-ray image by overlaying the X-ray observation data based on the celestial coordinate system.

[0045] The image construction device 9 performs data processing and can be installed anywhere, such as on an artificial satellite in orbit or on the ground.

[0046] As another example, we will explain an X-ray telescope array, which is a group of multiple X-ray telescopes used as a single large telescope. This is a composite telescope system in which the individual observation field directions of the multiple X-ray telescopes are correlated with each other. However, it is not easy to precisely correlate the observation field directions of each telescope using a mechanical structure method.

[0047] For example, even if multiple telescopes are mechanically arranged side by side, there is no guarantee that the optically conjugate coordinates on the celestial sphere of the X-ray detectors mounted on each telescope will actually match. Therefore, simply overlaying the observation data obtained from each X-ray detector will not produce an image with high spatial resolution. Therefore, in this embodiment, the observation field of view direction in celestial coordinates of the X-ray detector mounted on each telescope is identified, the difference from the reference field of view direction common to each telescope is detected, and this difference is corrected before overlaying. By adjusting the fields of view of the individual X-ray telescopes constituting an X-ray telescope array so that they overlap partially but do not completely coincide, it becomes possible to observe an area on the celestial sphere that is significantly larger than the individual fields of view of each individual X-ray telescope, shared by the fields of view of multiple telescopes, as shown in Figure 15. In this case, each individual telescope is mounted on a stage that adjusts its field of view orientation, and its field of view is directed in the nominal pointing direction of each telescope. However, since the difference in the instantaneous fields of view actually pointed by each telescope fluctuates over time, stitching (cutting and pasting) the data acquired by each telescope requires the overlapping of the data after determining the field of view orientation according to the present invention. Furthermore, the combined data can function as a telescope with a large combined aperture, enabling a bright optical system with a large aperture and a focal length relatively short compared to the diameter of the combined aperture to be realized by combining small individual telescopes. The telescope array of the present invention makes it possible to realize a synthetic aperture telescope whose field of view and aperture can be freely adjusted according to the observation purpose, under the condition that the product A of the telescope's aperture area S and the field of view solid angle Ω is constant. If the fields of view of each telescope constituting the array are overlapped in the same direction, it functions as a single large aperture telescope. Furthermore, if the fields of view of each telescope are directed in different directions, it functions as a single wide-angle telescope with a wide field of view.

[0048] Note that the field of view of an array telescope does not necessarily have to have overlapping areas; as shown in Figure 16, the product A of the aperture area S and the field of view Ω can be divided into A1, A2, ... Ak, allowing two or more independent areas to be observed simultaneously.

[0049] In the above embodiment, an X-ray telescope with a Walter 1 type grazing incidence optical system has been described, but the present invention may also be applied to telescopes that observe electromagnetic waves other than X-rays, such as ultraviolet light, visible light, and infrared light, and telescopes for optical communications. Furthermore, the telescope is not limited to space telescopes mounted on satellites, as long as it is equipped with an optical system and a detector. Furthermore, the object being observed is not limited to celestial bodies. In this case, instead of a celestial coordinate system, a coordinate system to which the object being observed belongs is used. [Explanation of symbols]

[0050] 1 X-ray telescope 2a-1~2a-3,2b-1~2b-3 Reflector 3. Two-dimensional X-ray detector 4 light source 5 Cross Prism 6 Condenser lens system 7. Photodetector 8 Processing equipment 9 Image Composition Device

Claims

1. a telescope including an optical system for collecting electromagnetic waves from an observation target or a target, and a detector for detecting the electromagnetic waves at the focal plane of the optical system; a light source disposed at a predetermined position around the detector; an optical component disposed in the optical path of the telescope, which combines a bundle of rays incident from the observation target or target object and a bundle of rays incident from the light source and outputs the combined bundle of rays; a condenser lens system that forms an image of the light beam emitted from the optical component; a photodetector that captures an image formed by the condenser lens system; a processing device that calculates the direction of the field of view of the telescope from the image captured by the photodetector; A telescope system with

2. 2. The telescope system of claim 1, wherein said electromagnetic waves are X-rays.

3. 3. The telescope system according to claim 1, wherein the optical component is a cross prism having a light absorbing function.

4. The telescope system according to claim 1 or 2, wherein the light source includes a plurality of light sources arranged offset in the optical axis direction of the telescope.

5. 3. The telescope system of claim 1, wherein the light source comprises a plurality of light sources arranged along a side of the detector.

6. 3. The telescope system of claim 1, wherein the images captured by the photodetector include an image captured by the photodetector with the light source turned on and an image captured by the photodetector with the light source turned off.

7. 3. The telescope system according to claim 1, wherein data detected by said detector is processed based on the field of view of the telescope calculated by said processing device to obtain a constituent image.

8. A telescope array system comprising a combination of a plurality of telescope systems according to claim 1 or 2.

9. 9. The telescope array system according to claim 8, wherein the angles between the optical axes of the plurality of telescopes are variable.

Images