JP5092159B2 - Optical apparatus and optical design method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical system for condensing light captured by a telescope having a wide visual field and a large opening size at a detector having a small effective diameter where noise influence can be ignored. <P>SOLUTION: Light that enters a primary image formation optical system and generates a primary image formation surface passes through a secondary optical system comprising a lens array with a plurality of small-diameter lenses. The secondary optical system is a relay optical system and enlarges at least the lateral magnification of the primary image formation surface to a prescribed value, so that each visual field of the small-diameter lens is expanded, becomes emitted light having a small inclination angle, and generates a secondary image formation surface. Light emitted from the secondary image formation surface is condensed at a detector arranged so that it becomes a common emission pupil of each small-diameter lens for forming the lens array, thus converting the visual field of the entire opening size of the primary image formation optical system to a visual field of a number of discrete small-diameter lenses, and hence essentially securing the large opening size of the primary image formation optical system and reducing the influence of background light, and realizing an optical system suitable for long-distance laser radar without any noise. <P>COPYRIGHT: (C)2008,JPO&amp;INPIT

Description

  The present invention relates to a telescope, that is, an optical device and an optical design method for the telescope, and more particularly to a technique related to visual field scanning in an optical system used for light amount detection including a laser rangefinder.

  When the light from the object is captured by the light receiving unit and guided to the detector, it is desirable that the aperture diameter of the light receiving unit is large. However, in order to increase the sensitivity (S / N ratio) of the detector, Is more advantageous. The condition of condensing light on a detector having a small effective diameter is a significant restriction on the tilt angle of the light beam with respect to the optical axis. This will be described in the case of a laser radar used in a conventional optical system with visual field scanning.

FIG. 9 is an example of a block diagram showing the basic configuration of the laser radar. The laser radar is roughly divided into a laser transmission unit 100, a reception unit 110, and a signal processing unit. When the laser transmission unit 100 emits a laser, the laser light (transmission light) is irradiated on the surface to be irradiated. Since it is scattered and returns in the transmission direction, the receiving unit 110 receives using a Cassegrain antenna having a large aperture, and collects it on a detector and detects it. The signal processing unit starts a digital counter when a transmitted light pulse is detected, and stops counting up the digital counter when a received light pulse is detected, measures a round trip time, Measure distance. By the way, it is known that the intensity of light scattered on the surface of the measurement object attenuates in inverse proportion to the square of the distance from the laser transmitter 100. Therefore, when performing long-distance measurement, it is necessary to increase the laser transmission output and increase the aperture area of the reception telescope so that the amount of received light collected on the detector is maintained above a certain level.
On the other hand, reducing background light (excess light) as much as possible leads to noise reduction. Therefore, it is desirable that the field of view of the receiving telescope is limited only to a field that is sufficient for the spot of the transmitting laser to enter, so that it is not unnecessarily widened. It is necessary to keep.

  Next, the mechanism of the scanning optical system using the laser radar having such characteristics will be described. Optical scanning mechanisms used in photocopiers include rotating polygon mirrors and oscillating mirror galvanometer mirrors, but these sliding parts cause deterioration in performance over time and shortening of service life. there is a possibility. Further, when considering two-dimensional scanning, there is a problem that both the weight and the volume increase because the conventional optical scanning mechanism requires at least two devices. Further, the scanning speed is also slower than a scanning mechanism using a so-called micromachine, which is a MEMS (Micro Electro Mechanical System) in which an electric circuit and a mechanical structure are integrated.

Therefore, if the scanning mechanism is realized using MEMS technology, it is possible to reduce the size, and of course, because it is supported by the spring structure, it does not generate friction only by the deformation resistance of the material, and it is also lightweight because of its small size. The scanning speed can be improved. Further, since two-dimensional scanning is possible with one device, there is no increase in weight and volume due to an increase in devices. Furthermore, since silicon, which has excellent mechanical properties (spring constant, specific gravity) and thermal properties, is the main material, it is suitable for harsh environments such as outer space.
Although this MEMS technology has many advantages, when a MEMS mirror is used as the two-dimensional scanning mechanism of a laser rangefinder, the major drawback is that the light receiving (aperture) surface is small to compensate for light attenuation. It becomes. In other words, as described above, the laser rangefinder has a characteristic that the magnitude of light attenuates in inverse proportion to the square of the distance. Therefore, the emitted laser must detect a small amount of light scattered by the irradiation target. However, with a small aperture area unique to MEMS mirrors, a sufficient light receiving area cannot be secured, and the measurement distance cannot be increased. For example, the distance image sensor of Nippon Signal Co., Ltd. uses a MEMS mirror of about 5 mm square, and the measurement distance is only about 10 m due to low laser output.

  Therefore, conventionally, when measuring long distances in a scanning optical system using a laser radar, the light receiving area, that is, the aperture area of the receiving telescope is set in order to avoid the influence of significant signal attenuation due to the distance as much as possible. A common approach is to perform field scans with a larger mirror and a larger mirror in front of the receiving telescope. For example, the rendezvous sensor of Jena-Optronik GmbH is a long-distance scanning type laser radar, but it scans the field of view by rotating a large mirror in two directions.

The following summarizes the problems with the prior art.
(1) Use of mirror:
In order to realize a long-distance scanning laser radar, the aperture diameter of the receiving telescope must be made as large as possible. For this reason, the conventional method has been to scan the field of view by attaching a large mirror in front of this receiving telescope. However, when the mirror is used, various disadvantages as described above must be taken into account. It was shortened with a small mirror. For this reason, realization of a laser radar that does not use a mirror has been desired.

(2) Condensing light to a detector with a small effective diameter:
If the receiving telescope has a large aperture diameter, it is clear from calculations that it is actually difficult to focus on a detector with a small effective diameter. The incident angle θen and the entrance pupil diameter Den, and the exit angle θex and the exit pupil diameter Dex are in the relationship of Expression (1).
θen ・ Den = θex ・ Dex (1)
Therefore, simply concentrating light entering the telescope with an aperture diameter Den = 100 mm at an incident angle θen = 5 ° onto a detector having an effective diameter Den = 1.5 mm results in an output angle θex = 80 °. In this calculation, light must be guided almost directly above or below (or just beside) the detector. In reality, it is extremely difficult to capture light from such a large aperture telescope with a small detector. Therefore, even in the case of a receiving telescope having a large aperture diameter, there has been a demand for focusing on a detector having a small effective diameter with a realistic light tilt angle.

(3) Regarding the increase in noise accompanying the increase in the visual field range:
An optical system with a wide field of view can be constructed to accommodate a telescope with a large aperture diameter. For example, an optical system that includes the entire field of view to be scanned can be considered, but as the field of view widens, more background light is captured and received. The signal-to-noise ratio of the circuit is degraded. For this reason, conventionally, a small field of view close to the laser spot diameter is scanned for a large aperture diameter if it is used for short distances determined from the size of the field of view that can tolerate noise, or if it is compatible with long distances. I had to deal with it. However, in consideration of the reduction in size and weight and the scanning speed, it is desirable that a long-range laser radar can be configured without scanning with a telescope having a large aperture diameter. In other words, there has been a demand to construct a telescope having a small aperture and a small field of view without scanning a field of view using a mirror or the like.

  Therefore, the present invention requires that the light receiving unit be enlarged if an object with a wide field of view (especially a dark object) is to be viewed, while collecting light received by a large light receiving unit with a detector having a small effective diameter. Accordingly, an object of the present invention is to provide an optical system that overcomes the problem that the inclination angle of the light toward the detector with respect to the optical axis becomes extremely large and cannot be collected.

In order to achieve the above object, according to the present invention, in an optical device including a primary imaging optical system, a relay optical system, and an exit pupil generation optical system, an object point of the relay optical system is formed by the primary imaging optical system. A primary imaging plane, and then the primary imaging by a relay optical system comprising a plurality of lens arrays having a plurality of lenses that make the entire field of the primary imaging optical system a set of discrete partial fields. The surface is transferred to the secondary image forming surface at an arbitrary lateral magnification larger than 1 ×, and then the light from the secondary image forming surface is received by the exit pupil generating optical system to emit light from each lens. A positive refracting power is applied to form a common exit pupil.
In this case, light passing through a plurality of lenses in the lens array may enter the exit pupil generating optical system to form a plurality of exit pupils. Further, a photodetector is arranged behind the exit pupil generating optical system so that the common exit pupil generated by the exit pupil generating optical system corresponds to the effective diameter of the photodetector, and the primary imaging optical system is arranged. Incident light may be detected.

  In addition, a shutter system for all or part of the plurality of lenses is provided in a region where the paths of light passing through adjacent lenses in the lens array are separated from each other and do not overlap, and the primary imaging is performed by opening and closing the shutter system. An optical path that passes through the optical system and reaches the exit pupil may be selectively blocked. Thereby, it is possible to select only a light beam from an arbitrary partial field of view. Further, the primary imaging optical system may be configured as a telecentric optical system.

  In order to achieve the above object, the present invention provides an optical apparatus including an afocal optical system that emits a parallel light beam incident on a primary imaging optical system as a parallel light beam from a collimating optical system. The incident parallel light beam is formed as an object point on the primary imaging plane, the traveling direction of the light received by the collimating optical system is bent at a positive refraction angle within a predetermined range to form an exit pupil as a parallel light beam, The light from the primary imaging surface formed by the primary imaging optical system by the relay optical system disposed between the primary imaging optical system and the collimating optical system becomes incident light to the collimating optical system. . In addition, the relay optical system of this configuration includes a plurality of lens arrays having a plurality of lenses that make the entire field of view of the primary imaging optical system a set of discrete partial fields of view, and the primary imaging plane is more than 1 ×. Is transferred to the secondary imaging surface at a large arbitrary lateral magnification. In this case, a photodetector may be arranged at the exit pupil position formed by the collimating optical system.

  According to the present invention, light received through the entire aperture diameter of the primary imaging optical system is passed through a secondary optical system comprising a lens array having a plurality of small-diameter lenses, and the secondary optical system is a relay optical system. Thus, at least the lateral magnification of the primary imaging surface generated by the primary imaging optical system is enlarged so as to be a predetermined value, so that each field of view of the small-diameter lens is expanded and the emitted light becomes a small inclination angle. Since the secondary imaging plane is generated, the light emitted from the secondary imaging plane is focused on a detector arranged so as to be a common exit pupil of each small-diameter lens forming the lens array. The field of view of the entire aperture diameter of the primary imaging optical system can be dispersed into at least the small fields of many discrete small-diameter lenses that allow object recognition, and light passing through each of the small fields can be collected again. It becomes. As a result, it is possible to reduce the influence of background light while substantially securing the large aperture diameter of the primary imaging optical system, and to realize an optical system suitable for a long-distance laser radar without noise.

An embodiment of an optical device of the present invention will be described below with reference to the drawings. The present invention abandons the conventional concept of field scanning by a mirror, and allows each light beam obtained from the entire large aperture diameter to pass through a relay optical system configured by using a plurality of discrete small-diameter lenses, thereby tilting the light and viewing field range. This is based on the technique of changing the light intensity and receiving light with a detector having a small effective diameter. In the present embodiment, an example is shown in which the primary imaging optical system is configured by a telecentric optical system in which a small stop (telecentric stop) is placed at the focal point of the lens and the optical axis and the principal ray can be regarded as parallel.
FIG. 1 is a basic conceptual diagram for explaining an optical device of the present invention. An actual optical device includes various other mechanisms such as a light transmission unit, a gain control, and an overall control unit, but is omitted here because they are not directly related to the features of the present invention.

  FIG. 1 shows an optical path from when an object is present on the left side until light emitted from the light transmitting unit is irradiated onto the object and enters the detector 6. As understood by the line arrows in the figure, the light from the object side first enters the telecentric optical system 3 that is a primary imaging optical system to generate a primary imaging surface, The small diameter lens (referred to as “microlens” in this embodiment) passes through a relay optical system 4 composed of a plurality of lens arrays 1 and 2, passes through a condenser lens 5, and finally a detector. 6 is detected. The optical configuration of this optical apparatus will be described in detail below.

A light beam entering the telecentric optical system 3 at an incident angle θ from the object side is converted into a (position) image height d as shown in FIG. The conversion formula between the incident angle and the image height is expressed by Expression (2).
d = f · tanθ (2)
Specifically, in FIG. 1, light (indicated by a solid line) that enters at a certain incident angle (θ °) with respect to the telecentric lens (focal length f) is focused at the point a, whereas the front ( The light that enters from (θ = 0 °) (shown by a broken line) is focused on the point b on the optical axis. In any case, all the light from the telecentric optical system 3 generates a primary imaging plane at a distance f from the telecentric image side main surface. This means that the telecentric optical system 3 converts the viewing angle of the receiving telescope into a position (image height) at a distance f.

  A relay optical system 4 including a lens array 1 and a lens array 2 is disposed behind the telecentric optical system 3. The lens array 1 includes a plurality of microlenses 1, and each microlens 1 is discretely arranged at a predetermined pitch interval. The lens array 2 has the same configuration. As shown in FIG. 1, each light beam entering the telecentric optical system 3 at a certain angle of incidence is condensed on a position (image height) determined with respect to the angle of incidence on the primary imaging plane and then the lens array 1. Can enter the microlens 1. That is, the light emitted from the telecentric optical system 3 having a large diameter becomes light incident on the lens array 1. Here, since the microlenses 1 of the lens array 1 are discretely arranged at a predetermined pitch interval, all of the light entering the telecentric optical system 3 is not necessarily incident on any of the microlenses 1. However, if the lens array 1 has a sufficiently small pitch interval, it is obvious that substantially all the light from the telecentric optical system 3 passes through the lens array 1 side. That is, if the pitch interval is smaller than the size of the object, in principle, the object can be recognized by the light that has passed through the lens array 1. For example, when trying to recognize a person with this optical apparatus, the presence of a person can be detected by using the lens array 1 arranged with a pitch interval narrower than the width of the person. From the viewpoint of the field of view, the arrangement of the plurality of microlenses 1 in the lens array 1 means that the entire field of view with a wide aperture on the telecentric optical system side is replaced with a set of fields of small microlenses.

As described above, light incident on the pitch interval region of each microlens 1 becomes light that is not finally collected by the detector 6, and as the pitch interval increases, the field of view of the entire lens array 1, that is, each microlens. The total field of view of the lens 1 becomes small and does not correspond to the field of view of the entire large aperture diameter of the telecentric optical system 3. On the other hand, if the diameter of the microlens 1 is too large, the entire field of view with a large aperture is not divided, and the principle of the present invention of small field division by a small microlens cannot be fully utilized. Therefore, the lens array 1 in which the small-diameter microlenses 1 are arranged with a sufficiently small pitch interval will greatly enhance the effects of the present invention.
Further, in the present embodiment, the case where the relay optical system 4 is configured by the two lens arrays 1 and 2 is shown, but the present invention is not necessarily limited thereto, and three or more lens arrays may be used. In addition, each microlens in each lens array does not necessarily have the same size, the same focal length, and the same pitch interval. The lens attributes may be different such that the distance is different or the pitch interval is wide or narrow. The same applies to the microlenses 2 of the lens array 2.
Further, in order to clearly limit the light beam incident on the microlens 1 out of the light beam emitted from the telecentric optical system 3, it is paired with each of the microlenses 1 on the primary imaging plane generated by the telecentric optical system 3. In addition, a mask having an opening smaller than that of the microlens 1 may be disposed. In this case, the microlens array may be continuously arranged.

  Returning to FIG. 1, here, the cross-sections of the four microlenses on each of the lens arrays 1 and 2 and the progression of light (solid line and broken line) among the two microlenses are shown. FIG. 2A shows the relationship between the field of view of the telecentric optical system 3 and the field of view of the microlens array 1, and the relationship between the lens array 1 and the lens array 2 constituting the relay optical system 4 is shown. This is shown in FIG. As shown in FIG. 2A, assuming that the shaded portion of the lattice that is discretely arranged at the pitch interval of the microlens 1 is the field of view per one of the microlenses 1, the dimension outside the lattice is the aperture of the telecentric optical system 3. It corresponds to the field of view as a whole. For the sake of convenience, in FIG. 2, the sum of the fields of view of the telecentric optical system 3 is a set of nine fields of view, and the relationship of each field of view of the microlens to this is shown, but it goes without saying that the number is not limited to this.

  That is, the entire field of view of the telecentric optical system 3 does not enter the relay optical system 4, but the region other than the field of view of each microlens 1 is considerably included when viewed from the sum of the fields of view of the telecentric optical system 3. As described above, the ratio increases as the pitch interval increases, and the field of view of each scattered microlens is only a minute (narrow) range. Therefore, in the present invention, the field of view of each microlens 1 of the relay optical system 4 is expanded to the full lattice frame divided as shown in FIG. In order to enlarge a small image on the microlens 1 to a predetermined range of a divided grating frame determined by the relationship with the effective diameter of the detector 6 by the relay optical system 4 of the microlens 1 and the microlens 2, The focal length of the microlens 2 may be made longer than the focal length of the microlens 1 to convert FNO (F number) darker. It is clear from the above equation (2) that this is also reducing the exit angle of the light exiting from each microlens 2 of the lens array 2 at the same time.

If the focal length of the microlens 1 is fm1 and the focal length of the microlens 2 is fm2, the magnification m in the relay optical system 4 is
m = fm2 / fm1 (3)
It is. In the above formula (3), the FNO (F number) is darkly converted to 1 / m by increasing the combined focal length for each minute region (field of view per microlens). In this way, the restriction caused by the pupil magnification of the emission angle θex in the equation (1) can be relaxed by FNO conversion.

  Finally, the light exiting from the relay optical system 4 is condensed on the detector 6 having a small effective diameter. As shown in FIG. 1, the light from each microlens 2 converted to a small emission angle by the relay optical system 4 generates a secondary imaging plane, but the light beam then travels toward the condenser lens 5. The condenser lens 5 is an optical system that forms an exit pupil corresponding to a real image of the entrance pupil (aperture stop) of the telecentric optical system 3, and refracts the received light and guides it to the detector 6. That is, by disposing the detector 6 at the exit pupil position, the light emitted from each microlens 2 of the lens array 2 is formed as a common exit pupil in the detector 6, and the detector 6 passes through the entrance pupil. Is received. Since the entire optical system is configured as an afocal optical system, the parallel light beam reaches the detector 6, but the detector 6 is arranged at the exit pupil of the entire optical system. As long as the light beam reaches the detector 6, it may be divergent or convergent. The condensing lens 5 constitutes the “exit pupil generation optical system” recited in the claims.

  As described above, according to the optical device of the present embodiment, a plurality of lens arrays having a large number of microlenses 1 and 2 are used for entering light having a large incident angle with respect to the large aperture diameter of the telecentric optical system 3. Light is received by the relay optical system 4 constituted by 1 and 2. This is a unique idea of the present invention that a set of a large number of minute (narrow) fields that exist discretely corresponds to a large aperture diameter. In a strict sense, the total field of view of the entire aperture diameter of the telecentric optical system 3 is It is not an exact match. However, there is no inconvenience of replacing with a set of such discrete fields of view instead of a complete aperture diameter as long as the missing part of the field of view does not interfere with object detection. . On the contrary, the discrete field of view by the microlenses 1 and 2 produces an effect that could not be achieved in the past, corresponding to the aperture diameter substantially the same as the telecentric optical system 3 having a large aperture diameter with a small field of view without scanning the field of view. It is something to be made. In other words, the present invention does not allow focusing on a detector having a small effective diameter by pursuing to completely capture the entire wide field of view by giving up part of the field of view at the aperture diameter of the receiving telescope. This solves the problems that long-range laser radars have.

  Next, an example of setting a shutter mechanism (shutter system) for preventing light from the microlenses 1 and 2 from entering the detector 6 in the above-described embodiment will be described. FIG. 3 shows a state in which the shutter mechanism is arranged on the primary imaging plane at a distance f from the telecentric image side main surface in FIG. Note that a motor drive system for controlling opening and closing of the shutter is omitted. Since the shutter exists corresponding to a part or all of each of the microlenses 1 and 2, it is referred to as “shutter array 7” in the present embodiment. For example, when the background light is excessively captured and the noise ratio is large, the shutter array 7 that can close the shutters corresponding to many microlenses 1 may be used. On the other hand, for example, when the background light is sufficiently cut in relation to the pitch interval between the microlenses 1 and 2 and the lens diameter, it is not necessary to block the light further. In such a case, all the shutters may be opened so that the light path is substantially the same as in FIG. 1 without the shutter mechanism.

FIG. 3 shows an example in which the shutter array 7 is arranged on the primary imaging plane generated by the telecentric optical system 3, that is, a configuration in which light is blocked in front of the relay optical system 4. However, the position of the shutter array 7 is not necessarily limited to this. It is not limited to. For example, FIG. 4 shows an example in which a shutter array 7 is disposed between the lens array 1 and the lens array 2 and light is allowed to pass through the lens array 1 but is shielded in front of the lens array 2. Not limited to these examples, until the light emitted from the telecentric optical system 3 enters the detector 6, the microlenses 1, 2 on the lens arrays 1, 2 are respectively adjacent to the microlenses 1, 2 or the microlenses 1, 2. It is sufficient that the shutter array 7 is located at an arbitrary position where the light from the light does not overlap, and it is desirable that the light can be blocked by selectively opening and closing the shutter with respect to an arbitrary microlens.
The shutter array 7 is not limited to the one using the MEMS mechanism. For example, any liquid crystal shutter that has a light shielding function in an array shape may be used. Further, the present invention is not limited to the transmissive shutter structure, and may be an arrayed reflection device such as a DMD element. These shutter device controls include electrical, mechanical, or any other method.

  Next, FIG. 5 shows an example of an array that covers a large aperture diameter in the field of view of a large number of microlenses, and a circular field of view of 5 ° (θen = θen = 180 mrad). This is an example shown in the case of 5 °). Each black circle is the field of view (1.5 mrad) of each microlens. Further, an example in which a 1200 μm square shutter is arranged with a period of 1.3 mm corresponding to each microlens is shown.

In the present embodiment, the case where the primary imaging optical system is configured by a telecentric optical system has been described. The reason for this is that in a telecentric optical system, the optical axis and principal ray are parallel, so that each point on the primary imaging plane can be treated as if it exists on the optical axis, and an image corresponding to an inclination angle with respect to the optical axis. This is because it is not necessary to consider a high deviation. Therefore, the present invention includes the case where the primary image-forming optical system is configured without using the telecentric optical system. In this case, a process for correcting the image height deviation may be added.
Furthermore, unlike the above-described embodiment, the present invention can be implemented using an optical system that handles diffused light, such as an integrating sphere, without configuring a relay optical system. In the case of an optical system that handles diffused light, although the time resolution is somewhat inferior to that of a relay optical system, there is an advantage that the field of view expressed discretely in the relay optical system becomes continuous. However, the visual field in this case is formed by the shutter size.

The technology of the optical device (optical system) described in this embodiment can be applied to a laser distance meter and the like, and is expected to be realized in a wide range by being incorporated in various products such as automobiles and aircrafts.
Further, according to the optical device of the present embodiment, the entire field of view of the reception telescope having a large aperture diameter is regarded as a collection of minute fields of view, so that the signal noise caused by background light is maintained while maintaining the aperture area of the reception telescope. Occurrence can be remarkably suppressed. Unlike the conventional long-distance scanning laser rangefinder, which had to mount a large mirror in front of the telescope to scan the field of view, the optical system configuration of this embodiment does not use a mirror mechanism. Since light can be detected, it does not include sliding parts, and does not cause a cause of failure due to a decrease in performance and life of various parts over time. In addition, the optical device can be miniaturized and lightly slaved.
Further, since the shutter corresponding to the micro lens of the relay optical system is provided so as to be selectively opened and closed, light detection can be performed while appropriately adjusting the field of view according to the object or in relation to the noise ratio.
Accordingly, the reliability of the optical apparatus is improved, and the superiority of the present invention is remarkable when used in an environment where high reliability is required, such as satellite equipment, as well as general mechanical parts. It will be.

Finally, a detailed design example when concretely implementing the present invention is shown below.
・ Wavelength: 1064nm
-Field diameter: 10 ° circumferential field (or 7 ° rectangular field)
-Instantaneous visual field diameter: 5.3 minutes (1.5mrad)
-Instantaneous visual field interval: 50 arc minutes (50 arcmin, 14.54 mrad)
-Condensing optics Effective diameter: φ100mm (equivalent to entrance pupil diameter)
Focal length: 82mm
Aperture ratio: F0.82
・ Relay optical system Relay magnification: 7 times Emission chief ray tilt angle: 60 °
Exit pupil diameter: φ1mm (detector diameter)

This optical apparatus is configured as an afocal optical system as a whole. That is, the optical system emits a light beam incident as a parallel bundle as a parallel bundle. This optical system includes (1) a condensing optical system, (2) a relay optical system, and (3) an exit pupil generating lens.
(1) The condensing optical system (primary optical system) is configured as an exit side telecentric optical system with four groups and four aspherical surfaces. An aperture stop is disposed at the incident side lens position of the condensing optical system. Therefore, the aperture stop becomes the entrance pupil as it is. That is, “the position and the diameter of the aperture stop” coincides with “the position and the diameter of the entrance pupil”.
(2) The relay optical system has a function of enlarging and transferring an image of a minute area discretely cut out from the image plane of the condensing optical system and enlarging it to the same size as the discrete pitch.
(3) The exit pupil generation lens is an optical system having the image plane of the relay optical system as an object plane, and generates an exit pupil behind this lens. This exit pupil corresponds to a real image of the aperture stop of the condensing optical system. Therefore, if the photodetector is arranged at this position, all the light beams that have passed through the entrance pupil (aperture stop) reach the detector.

The condensing optical system sets the entrance pupil diameter to 100 mm in order to obtain a desired received light energy. Since the exit pupil diameter (detector diameter) is set to φ1 mm, the pupil magnification Mp (pupil magnification) of the entire optical apparatus (hereinafter simply referred to as “the present optical system”) is 1/100.
A conservative law of Ma × Mp = 1 exists between the pupil magnification, the angular magnification (corresponding to the ratio of the incident chief ray tilt angle and the exit chief ray tilt angle) of this optical system, and Ma (angular magnification). Yes (Helmholtz-Lagrange's law). Therefore, in the case of this lens, Ma = 1 / Mp = 100.
Therefore, if the field of view (half angle) is 5 °, the exit chief ray inclination angle is Mp × 5 ° = 100 × 5 ° = 500 °, that is, 1000 ° in all angles. In practice, however, such an arrangement cannot exist.

Therefore, if the maximum value of the tilt angle with respect to the optical axis of the light beam emitted from the optical system toward the detector is defined as 60 °, the realizable field of view is only 60 ° / Ma = 60 ° / 100 = 0.6 ° at most. I understand that it is not too much. Therefore, assuming that a region of a total of 0.6 ° is discretely arranged in the range of 5 ° half-width, if the diameter of each discrete region (instant visual field) is set to 5.3 arcmin (0.088 °, 1.5mrad), 6.88 Thus, 6 to 7 discrete regions can be secured per half field of view. Now, assuming that the entrance pupil diameter of the condensing optical system is 100 mm, the field half angle θ is 5 °, and the corresponding image size y is 7.2 mm, the focal length f that the present optical system should have is y = f × tan θ. From the relationship, 7.2 mm = f × tan (5 °), so that f = 82 mm. At this time, the aperture ratio F of the condensing optical system is 0.82.
(Effective shutter diameter: Rectangular inscribed circle is equivalent to 7.2mm x 2 = φ14.4mm)
The image size corresponds to the total effective area size of the MEMS shutter.
(Effective shutter diameter: Converted to the size of a rectangular inscribed circle, 7.2mm x 2 = φ14.4mm equivalent)

  The field of view and the shutter are arranged in the same manner as in FIG. Further, a mask corresponding to each instantaneous visual field is arranged on the image plane of the condensing optical system. If a relay system having a lateral magnification M of 7 times is arranged behind the mask, each instantaneous visual field size is enlarged 7 times. In other words, the focal length of the combining optical system composed of the condensing optical system and the relay system is enlarged seven times. Therefore, the focal length of the composite optical system is expanded to 574 mm. This means that the composite aperture ratio becomes dark up to F5.74. Further, the relay lens is configured by arranging two aspheric lens arrays facing each other. In order to apply the above specifications to all instantaneous visual fields exactly equally, the condensing optical system is designed as an exit side telecentric.

As described above, the MEMS shutter is arranged with one opening inside each relay system for each instantaneous visual field arranged discretely. Light rays are emitted from the image plane created by the relay system at a divergence angle equivalent to F5.74. In order to emit this as a parallel light beam having an exit pupil diameter of φ1 mm, a pupil generating lens having a focal length of 5.74 mm may be disposed. The pupil generating lens is assumed to be a Fresnel lens, but is not necessarily limited to this.
FIG. 6 shows the result of the mounting design based on the actual ray tracing based on the above principle, that is, the lens data, and FIGS.

The aspheric coefficient K in the lens data is a conical coefficient, and A, B, C, D, and E are 4th to 12th even-order aspheric coefficients, respectively, and the apex of each surface (the lens surface and With respect to the surface depth (so-called sag amount) Z from the contact plane at the intersection of the optical axes), the following equation is defined. Here, r is the radius of curvature at the surface vertex, and h is the surface height from the optical axis.

It is a figure for demonstrating the basic concept of the optical apparatus of this invention. It is a figure which shows the relationship of each visual field of a telecentric optical system, a relay optical system, and a micro lens. It is a figure which shows an example when the shutter mechanism has been arrange | positioned to the optical apparatus of this invention. It is a figure which shows the example when the shutter mechanism is arrange | positioned in the position different from the example of FIG. It is the figure which showed an example of the arrangement | sequence which covers a big aperture diameter in the visual field of many microlenses. It is the lens data used in the specific Example of this invention. It is an optical system block diagram used in the specific Example of this invention. It is an optical system block diagram used in the specific Example of this invention. It is a basic block diagram of the laser radar used with the optical system with the conventional visual field scanning.

Claims (6)

An optical device including a primary imaging optical system, a relay optical system, and an exit pupil generation optical system, and passes light incident on the primary imaging optical system to the relay optical system and the exit pupil generation optical system for,
The primary imaging optical system generates a primary imaging plane so as to form an object point of the relay optical system, and the relay optical system converts the entire field of the primary imaging optical system into a set of discrete partial fields. A plurality of lens arrays having a plurality of lenses, wherein the primary imaging surface is transferred to a secondary imaging surface at an arbitrary lateral magnification greater than 1x,
The optical apparatus, wherein the exit pupil generation optical system receives light from the secondary imaging plane and gives a positive refractive power to the exit light from each lens to form a common exit pupil.   The primary imaging optical system is arranged by arranging the photodetector behind the exit pupil generating optical system so that a common exit pupil generated by the exit pupil generating optical system corresponds to an effective diameter of the photodetector. The optical device according to claim 1, wherein the optical device detects light incident on the light source. A shutter system for all or part of the plurality of lenses is provided in a region where the paths of light passing through adjacent lenses in the lens array are separated from each other and do not overlap, and the primary imaging is performed by opening and closing the shutter system. the optical device according to claim 1 or 2, characterized in that blocks the optical path reaching the exit pupil passes through the optical system selectively. The optical device according to any one of claim 1 to 3, wherein the primary image-forming optical system is telecentric optical system. An optical device of an afocal optical system that emits a parallel light beam incident on a primary imaging optical system as a parallel light beam from a collimating optical system,
A primary imaging optical system for forming an incident parallel light beam as an object point on the primary imaging surface;
A collimating optical system that forms the exit pupil as a parallel beam by bending the traveling direction of the received light at a positive refraction angle within a predetermined range;
A relay optical system that bridges so that light from the primary imaging surface formed by the primary imaging optical system becomes incident light to the collimating optical system,
The relay optical system includes a plurality of lens arrays having a plurality of lenses that make the entire field of view of the primary imaging optical system a set of discrete partial fields of view, and the primary imaging surface is arbitrarily larger than 1 time. An optical apparatus for transferring to a secondary imaging plane at a lateral magnification of. The optical device according to claim 5 , wherein a photodetector is disposed at an exit pupil position formed by the collimating optical system.

Images