JP2004226100A - Observation system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain an observation system which can cover the whole body of the incident opened surface of an observing optical system and to which the function of discovering an optical path having a possibility of becoming a harmful flare at observing time can be give by securing sufficient corrected luminance with a low power consumption. <P>SOLUTION: A radiometric correcting device 1A has many fine light sources 11 which are bundled in a planar state to constitute a light emitting surface. The area surrounded by a circumscribed circle 12 circumscribing the fine light sources 11 has an area including the incident opened surface 5a of the observing optical system 4. <P>COPYRIGHT: (C)2004,JPO&NCIPI

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an observation system for monitoring the sensitivity of an optical sensor mounted on a satellite whose mission is to perform earth observation or planetary exploration by using a radiometric calibration device.
[0002]
[Prior art]
In a conventional observation system, by emitting calibration light that uniformly illuminates all pixels of the detector, all pixels of the one-dimensional array detector can be calibrated at the same time. The effect of degassing can be reduced (for example, see Patent Document 1).
[0003]
[Patent Document 1]
Japanese Patent No. 2660364 (page 4, FIG. 1)
[0004]
[Problems to be solved by the invention]
Conventional observation systems do not have the ability to find light paths that can cause harmful flares during observation because the light does not uniformly illuminate the entire entrance aperture of the observation optical system. There was a problem.
[0005]
The present invention has been made in order to solve the above-described problems, and an object of the present invention is to obtain an observation system that can cover the entire entrance aperture of an observation optical system and has sufficient calibration luminance with low power consumption. With the goal.
[0006]
[Means for Solving the Problems]
The observation system according to the present invention is a radiometric calibration device that outputs a calibration light beam, a bending mirror that introduces the calibration light beam during calibration, an observation optical system that passes the calibration light beam that is introduced by the bending mirror, A CCD detector for detecting the calibration light flux emitted from the observation optical system. Further, the radiometric calibration device has a large number of minute light sources that are bundled in a planar shape to form a light emitting surface, and a region surrounded by a circumscribed circle circumscribing the large number of minute light sources is an incident light of the observation optical system. It has an area including the opening surface.
[0007]
BEST MODE FOR CARRYING OUT THE INVENTION
Embodiment 1 FIG.
First, an observation system related to the present invention will be described with reference to the drawings. FIG. 9 is a diagram showing a configuration of an observation system related to the present invention. In FIG. 9, in order to avoid complication, a partly broken surface is provided to make the components easy to see.
[0008]
In FIG. 9, the radiometric calibration device 1 is a device mounted on a base plate 8 and including at least one lamp as a component. The pointing mirror 2 mainly has a function of rotating around a pointing mirror rotation axis 3 in order to set various observation directions at the time of observation, but between the observation, the radiometric calibration device 1 transmits the observation optical system 4 to the observation optical system 4. The angle at which the calibration light beam 7 is introduced can be set.
[0009]
In FIG. 1, the radiometric calibration device 1 is designed to supply a calibration beam 7 having a stable radiation intensity in an environment where the calibration beam 7 is encountered from the ground to on-orbit. By being incident on the system 4 and collecting its output, it is possible to monitor contamination on the optical surface of the observation optical system 4, deterioration of transmission or reflection, deterioration of the detector sensitivity, and the like. The radiometric calibrator 1 having the lamp usually has a small exit aperture as shown in the figure, so that the calibration beam 7 cannot cover the entire entrance aperture 5a and exit aperture 5b of the observation optical system 4. Did not.
[0010]
FIG. 10 is a diagram for explaining the operation of the observation system shown in FIG.
[0011]
In FIG. 10, the pointing mirror 2 is omitted from the tunnel diagram. The calibration light beam 7 emitted from the radiometric calibration device 1 reaches the CCD detector 6 via the pointing mirror 2, the entrance aperture 5a of the observation optical system 4, and the exit aperture 5b of the observation optical system 4.
[0012]
The size of the area through which the light beam captured by the CCD detector 6 with the calibration light beam 7 passes on the optical surface of the observation optical system 4 is the light beam exiting the entire exit aperture of the radiometric calibration device 1 heading for one pixel of the CCD detector 6. However, the size of the area passing on the optical surface of the observation optical system 4 and the light flux emitted from the center point of the radiometric calibration device 1 toward all the pixels of the CCD detector 6 pass on the optical surface of the observation optical system 4. Is obtained as a convolution with the size of the region to be processed.
[0013]
As a result, the entrance aperture 5a of the observation optical system 4 is greatly affected by the exit aperture of the radiometric calibration device 1, and the exit aperture 5b of the observation optical system 4 is greatly affected by the size of the CCD detector 6. . Although the CCD detector 6 is drawn in a rectangular shape in FIG. 10, since the CCD detector 6 actually has a shape close to a straight line, the area size on the entrance aperture 5a of the observation optical system 4 substantially matches the radiometric calibration device 1, and The size of the area on the exit aperture surface 5b of the optical system 4 matches the size of the CCD detector 6 which is slightly thicker in the short side direction.
[0014]
For this reason, if contamination adheres to the optical surface of the observation optical system 4 through which the calibration light beam 7 does not pass, it does not appear as a change in output on the CCD detector 6. However, since the observation light passes through almost the entire optical surface of the observation optical system 4 and reaches the CCD detector 6, the influence of the contamination appears on the data at the time of observation. That is, the radiometric correction of the data at the time of observation could not be completed completely by the calibration data by the apparatus as described above. In order to solve this drawback, a method has been proposed in which the luminous flux diameter at the time of calibration is extended to the entrance aperture surface 5a of the observation optical system 4 by using a diffusion plate or a plurality of lamps. The brightness of the light is significantly reduced. In addition, the latter method involves an enormous amount of power consumption and heat generation, and thus has been unsuitable for use on a satellite.
[0015]
On the other hand, the radiometric calibration device 1 has an advantage that when contamination is attached to a region through which the calibration light beam 7 passes, the attachment location can be specified under specific conditions. For example, when a spot or minute area of contamination adheres to the entrance aperture 5 a of the observation optical system 4, it appears as an output change in many pixels of the CCD detector 6. When the same contamination adheres to 5b, there is a characteristic that an output change appears only in some pixels of the CCD detector 6. Therefore, it is possible to estimate which optical surface is contaminated from this output change, and at the same time, it is possible to determine which part of the optical surface is contaminated. However, this characteristic also did not function sufficiently because the calibration light flux 7 did not impinge on the entire entrance aperture surface 5a of the observation optical system 4.
[0016]
Next, if a refracting optical system exists inside the observation optical system 4, flare due to reflection between optical surfaces is always superimposed on data at the time of observation. A flare caused by a normally propagating light beam can be obtained analytically. However, when an abnormal propagation, such as a prism inside the observation optical system 4, the light beam reflected on the side surface of the prism is complicated. Since three-dimensional reflection occurs, it is extremely difficult to analytically obtain the three-dimensional reflection.
[0017]
Therefore, the amount of flare due to this abnormal propagation could not be estimated by radiometric correction. If the optical path that could cause harmful flare at the time of observation can be grasped in advance, more accurate calibration will be possible. The phenomenon that causes harmful flare at the time of observation is mostly caused by the fact that a ghost source conjugate with the CCD detector 6 is present near the observation optical system 4. In other words, if the radiometric calibration device 1 is placed near the observation optical system 4, it is possible to add a function that can detect in advance the ghost, that is, an optical path that may cause harmful flare at the time of observation. It is. However, the radiometric calibration device 1 could not have the function because the entire surface of the entrance aperture 5a of the observation optical system 4 was not uniformly illuminated.
[0018]
The problem of measuring the line of sight of the entire optical system in which the pointing mirror 2 and the observation optical system 4 are coupled on the trajectory has been desired, but not realized. The line of sight of the entire optical system changes its direction when the metal frame mounting portion holding the optical system is distorted due to environmental factors. This distortion is also caused by the temperature environment encountered by the orbited satellite. However, when distortion occurs on the orbit, it has been impossible at all to measure the distortion. For this reason, it has been the mainstream to make predictions through thermal structure analysis and confirm them at the design stage. In order to detect such deformation, a system that actively emits a light beam is required, but a satellite with limited power consumption has not been actively introduced. However, since the radiometric calibration device 1 has a built-in light source, there is a possibility that a function of measuring the distortion can be added. However, the radiometric calibration device 1 succeeds in adding the function. Not.
[0019]
Next, an observation system according to the first embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing a configuration of an observation system according to Embodiment 1 of the present invention. In the drawings, the same reference numerals indicate the same or corresponding parts.
[0020]
In FIG. 1, the pointing mirror 2 of the related art is replaced with a bending mirror 9, but the pointing function is not an essential requirement of the present invention, and it is sufficient if there is a function of switching between two modes during observation and calibration. Therefore, the bending mirror 9 is used instead of the pointing mirror 2. The radiometric calibration device 1A has a planar light emitting surface, and is installed on or in the base plate 8.
[0021]
FIG. 2 is a diagram showing the structure and operation of the radiometric calibration device of the observation system according to the first embodiment of the present invention.
[0022]
In FIG. 2A, the radiometric calibration device 1A has a large number of minute light sources (having a diameter of about 5 mm) 11 arranged in a circumscribed circle 12. As the minute light source 11, a light source with good power efficiency and low power consumption or heat generation even when a plurality of light sources are turned on at once, for example, a white LED is optimal. Further, the minute light sources 11 are arranged in a plane at intervals so as to prevent the minute light sources 11 from being destroyed by mutual heat generation. This circumscribed circle (having a diameter of about 200 mm) 12 is a virtual circle circumscribing all the minute light sources 11.
[0023]
FIG. 2B is a diagram for explaining the operation of the radiometric calibration device of the observation system according to the first embodiment. In the figure, the circumcircle 12 of the radiometric calibration device 1A is projected onto the entrance aperture 5a of the observation optical system, and the area surrounded by the projected image of the circumcircle 12 is surrounded by the entrance aperture 5a of the observation optical system. FIG. By turning on all but a part of the minute light source 11 of the radiometric calibration apparatus 1A in FIG. 2A, the calibration light beam 7 can irradiate the entire surface of the entrance aperture 5a of the observation optical system. ing. Note that the dotted line represents the folding mirror 9.
[0024]
As a result, the radiometric calibration device 1A has a light-emitting surface that covers the entire entrance aperture surface 5a of the observation optical system, and has sufficient calibration luminance with low power consumption. The turning on and off of the minute light source 11 is to connect a power source to all of the minute light sources 11 via a switch, and to open and close a switch corresponding to the minute light source 11 programmed in advance by a CPU or the like. The same applies to the embodiments.
[0025]
Embodiment 2 FIG.
An observation system according to Embodiment 2 of the present invention will be described with reference to the drawings. FIG. 3 is a diagram showing a configuration of a radiometric calibration device of an observation system according to Embodiment 2 of the present invention.
[0026]
In FIG. 3A, the overall configuration is the same as that of the first embodiment, but since the function of the radiometric calibration device 1A is different from that of the first embodiment, the configuration of the radiometric calibration device 1A is different. Only shown.
[0027]
In the figure, assuming a hemisphere (not shown) having a section of a circumscribed circle 12 surrounding a large number of minute light sources 11 of the radiometric calibration apparatus 1A, a first plane 14 including a pixel array of the CCD detector 6 and an optical axis 13 is illustrated. Are drawn with a plurality of meridians 17 having both ends of the diameter 15 of the circumscribed circle 12 included in the circle as poles 16. In order to avoid complication of the drawing, the meridian 17 is shown only on one side with the first plane 14 as a boundary.
[0028]
FIG. 3B is a diagram of FIG. 3A viewed from the optical axis direction.
[0029]
In the figure, a small light source group 19 is determined along a selected meridian projection curve 18 obtained by projecting a meridian selected from a plurality of meridians 17 in FIG. In the figure, the minute light source group 19 is indicated by a filled circle (black circle). All the minute light sources 11 in the minute light source group 19 are turned on. The other meridians 17 can be similarly grouped, and can be configured to be individually lit for each minute light source group (group).
[0030]
When the minute light source group 19 is turned on along the selected meridian projection curve 18, the calibration light beam 7 enters the observation optical system 4 along the curved surface including the selected meridian projection curve 18, so that the curved surface and the observation surface are observed. The line of intersection with the optical surface of the optical system 4 substantially describes the meridian of the optical surface. In addition, since the points on the meridian of the optical surface correspond one-to-one with the pixels of the CCD detector 6, a function of specifying a region of contamination attached on the meridian of the optical surface of the observation optical system 4 is provided. . Accordingly, the same effect as that of the first embodiment can be obtained, and at the same time, the contamination or deterioration area on the optical surface in the observation optical system can be specified.
[0031]
Embodiment 3 FIG.
An observation system according to Embodiment 3 of the present invention will be described with reference to the drawings. FIG. 4 is a diagram showing a configuration of a radiometric calibration device of an observation system according to Embodiment 3 of the present invention.
[0032]
In FIG. 4, the overall configuration of the observation system of the third embodiment is the same as that of the first embodiment, but the configuration of the radiometric calibration device 1A is different from that of the second embodiment. Only the configuration of the metric calibration device 1A is shown.
[0033]
In the third embodiment, a function of specifying an abnormal propagation light path which causes a flare generated in the observation optical system 4 is added.
[0034]
When the observation optical system 4 is rotationally symmetric, a ghost that causes a flare caused by a normally propagating light beam is dominated by a light beam incident from the vicinity of the rotational symmetry axis, but involves side reflection of a prism or the like. Ghosts that cause flare due to abnormal propagation often exist far away from the rotational symmetry axis of the observation optical system 4.
[0035]
In order to find such a ghost, it is necessary to scan the front surface of the entrance aperture surface 5a of the observation optical system 4 with a narrow light beam. For example, as shown in FIG. 4, there is a method in which a surface surrounded by a circumscribed circle 12 is vertically and horizontally divided into a grid. A small light source group 21 is a group in which the small light sources 11 surrounded by the hexagonal shape are divided by the divided gratings 20 in the horizontal, right diagonal, and left diagonal directions. In the figure, they are indicated by solid circles (black circles).
[0036]
If there is a ghost causing flare due to abnormal propagation near the minute light source group 21, turning on all minute light sources of the minute light source group 21 causes an abnormally large output to appear at a specific pixel of the CCD detector 6. The abnormal propagation light path can be immediately identified. When all of the small light sources 11 are turned on, the average output is increased, so that the ghost becomes relatively small and it is impossible to make a distinction. This has the effect that an abnormal propagation light path that causes flare occurring in the observation optical system can be specified.
[0037]
Embodiment 4 FIG.
An observation system according to Embodiment 4 of the present invention will be described with reference to the drawings. FIG. 5 is a diagram showing a configuration of a radiometric calibration device of an observation system according to Embodiment 4 of the present invention.
[0038]
In FIG. 5A, the overall configuration of the observation system according to the fourth embodiment is the same as that of the first embodiment, but the configuration of the radiometric calibration device 1A is different from the other embodiments.
[0039]
In the figure, a first minute light source group 22a and a second minute light source group 22b indicated by oblique lines are groups selected centering on both ends of the virtual line segment 23 on the light emitting surface, and these two groups can be turned on at the same time. It is like that. Incidentally, reference numeral 24 denotes a virtual line indicating the pixel arrangement direction of the CCD detector 6.
[0040]
FIG. 5B is a diagram for explaining the arrangement of the radiometric calibration device 1A of the observation system according to the fourth embodiment.
[0041]
In the figure, a line segment 25 forming a chord is a chord other than the diameter stretched on the entrance aperture surface 5 a of the observation optical system 4, and the chord is parallel to the pixel arrangement direction of the CCD detector 6. The virtual line segment 23 and the chord line segment 25 on the light emitting surface constitute a plane parallel to the optical axis 13 via the bending mirror 9. The first minute light source group 22a and the second minute light source group 22b are minute light source groups whose centers are located at both ends of the virtual line segment 23 on the light emitting surface. Normally, the entrance aperture surface 5a of the observation optical system 4 has a circular shape, and tangent lines at both ends of the line segment 25 forming a chord have an angle θ with each other.
[0042]
FIG. 6A is a graph showing an output profile of all pixels appearing on the CCD detector 6 when the first minute light source group 22a and the second minute light source group 22b in the fourth embodiment are simultaneously turned on.
[0043]
In the figure, the output sharply drops near the both ends of the pixel to form a trapezoidal output profile. This occurs because a light beam is cut off at the edge of the entrance aperture surface 5a of the observation optical system 4.
[0044]
Therefore, the direction of the optical axis 13 changes due to the eccentricity / tilt of the optical system existing from the bending mirror 9 to the CCD detector 6, and when the change is in the pixel arrangement direction of the CCD detector 6, the output is changed. The profile shifts left and right without changing the width of the trapezoid as shown by the solid line in FIG.
[0045]
On the other hand, when the change is in the direction orthogonal to the pixel arrangement, the trapezoidal width of the output profile changes as shown by the solid line in FIG. In each case, the dotted line indicates the profile before the change. By using this characteristic to determine a change in the optical axis 13, a change in the line of sight of the observation optical system 4 can be captured, and distortion generated on the orbit can be measured.
[0046]
FIG. 7 is a diagram showing another configuration example of the fourth embodiment.
[0047]
In FIG. 7, the relationship between the line segment 25 forming the chord and the virtual line segment 23 on the light emitting surface is the same as in FIG. However, the first minute light source group 22a and the second minute light source group 22b are provided with a Λ (lambda) type structure 26 made of, for example, an aluminum plate inside the optical system so as to enter the effective diameter of the observation optical system 4. Therefore, it is not necessary to set the centers of the virtual line segments 23 on both ends on the light emitting surface.
[0048]
The Λ-shaped structure 26 is provided so as to form an A-shape with the virtual line 24 indicating the pixel arrangement direction of the CCD detector 6. With this configuration, the output profile shown in FIG. 6 can be obtained more reliably.
[0049]
FIG. 8 shows a Λ-shaped structure 26 which is a truss 27 which forms a part of a lens barrel and is made of, for example, a resin pipe.
[0050]
It is said that energy loss can be minimized and the problem can be solved by using a truss structure required as a reinforcing structure, rather than adding the Λ-shaped structure 26 that causes energy loss as the observation optical system 4 alone. There are benefits. According to the above configuration, the same effect as that of the first embodiment can be obtained, and at the same time, it is possible to measure the change of the line of sight under the environment encountered on the orbit.
[0051]
【The invention's effect】
As described above, in the observation system according to the present invention, the radiometric calibration device has a large number of minute light sources that are bundled in a plane and forms a light emitting surface, and is surrounded by a circumscribed circle circumscribing these minute light sources. The region indicated has an area including the entrance aperture of the observation optical system. Therefore, it is possible to cover the entire entrance aperture surface of the observation optical system, and it is possible to secure sufficient calibration luminance with low power consumption.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of an observation system according to Embodiment 1 of the present invention.
FIG. 2 is a diagram showing a structure and an operation of a radiometric calibration device of the observation system according to the first embodiment of the present invention.
FIG. 3 is a diagram showing a configuration of a radiometric calibration device of an observation system according to Embodiment 2 of the present invention.
FIG. 4 is a diagram showing a configuration of a radiometric calibration device of an observation system according to Embodiment 3 of the present invention.
FIG. 5 is a diagram illustrating a configuration and an arrangement of a radiometric calibration device of an observation system according to a fourth embodiment of the present invention.
FIG. 6 is a diagram showing an output profile of a radiometric calibration device of an observation system according to Embodiment 4 of the present invention.
FIG. 7 is a diagram showing another configuration example of the observation system according to the fourth embodiment of the present invention.
FIG. 8 is a diagram in which the Λ-shaped structure of FIG. 7 is configured by a truss.
FIG. 9 is a diagram showing a calibration method by an observation system of a related technique.
FIG. 10 is a diagram showing an operation of the observation system of the related art.
[Explanation of symbols]
1A radiometric calibration device, 4 observation optical system, 5a entrance aperture, 5b exit aperture, 6 CCD detector, 7 calibration beam, 8 base plate, 9 folding mirror, 10 folding mirror rotation axis, 11 micro light source, 12 circumscribed circle , 13 optical axis, 14 first plane, 15 diameter, 16 poles, 17 meridian, 18 meridian projection curve, 19 minute light source group, 20 division grating, 21 minute light source group, 22a first minute light source group, 22b second minute Light source group, 23 virtual line segments, 24 virtual line indicating the pixel arrangement direction of the CCD detector, 25 string line segments, 26 ° structure, 27 truss.

Claims (7)

A radiometric calibration device that outputs a calibration beam,
A bending mirror for introducing the calibration light beam during calibration,
An observation optical system that passes the calibration light beam introduced by the bending mirror,
A CCD detector that detects the calibration light flux emitted from the observation optical system,
The radiometric calibration device has a large number of minute light sources that are bundled in a planar shape to form a light emitting surface, and a region surrounded by a circumscribed circle circumscribing the large number of minute light sources is an entrance aperture surface of the observation optical system. An observation system having an area including: The radiometric calibration device, when assuming a hemisphere having a cross section of the circumscribed circle as the plurality of minute light sources, the diameter of the circumscribed circle included in a plane including the pixel array and the optical axis of the CCD detector. Draw a plurality of meridians with both ends as poles, group the plurality of small light sources along a plurality of meridian projection curves obtained by projecting the plurality of meridians on the cross section, and individually light up each group. The observation system according to claim 1, wherein: The radiometric calibration device, the plurality of minute light sources are grouped into groups for each of a plurality of minute light sources in a region surrounded by a plurality of division grids on a surface surrounded by the circumscribed circle, and individually for each group. The observation system according to claim 1, wherein the observation system is turned on. The radiometric calibration device includes a plurality of minute light sources, each of which includes a chord other than a diameter that is parallel to a plane including a pixel array and an optical axis of the CCD detector and is stretched on an entrance aperture of the observation optical system. The center is located at both ends of a line segment formed by intersecting a second plane parallel to the light-emitting surface and the light-emitting surface is grouped into two groups for each of a plurality of small light sources that are in contact with the circumscribed circle, and the two groups are simultaneously turned on. The observation system according to claim 1, wherein: Further comprising a Λ-shaped structure to block the outer edge of the aperture inside the observation optical system,
The observation system according to claim 4, wherein the Λ-shaped structure is arranged so as to intersect with a plane including an optical axis and a pixel array of the CCD detector so as to form an A-shape. The observation system according to claim 5, wherein the Λ-shaped structure is constituted by a truss forming a part of a lens barrel. The observation system according to any one of claims 1 to 6, wherein the minute light source is configured by a white LED.

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