JPH08101303A - Flyeye - Google Patents

Abstract

PURPOSE: To impart an adequate optical function to a flyeye when there is anisotropy in the incident angle of light on the flyeye. CONSTITUTION: Both faces of this flyeye are constituted by closely bundling many elements 40 which are convex lenses existing the paraxial focal positions of the other face. The sectional shape of these elements 40 is formed to a rhombic shape. The max. value (i.e., photodetecting angle) of a main ray inclination βfor all of the incident luminous fluxes on the flyeye (many elements 40) to emit effectively from the flyeye has the characteristic that the value is large in the long opposite line direction of the rhombic shape of the element 40 and small in the short diagonal line angle. This optical characteristic is utilizable to many purposes. Namely, the optical system having the condensing function adequate for the anisotropy is constituted by using such flyeye in various cases where the incident angles of light beams have anisotropy.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fly's eye which is a set of a large number of convex lenses, and more particularly to a fly's eye having a novel optical function which is suitable when the incident angle of incident light is anisotropic. And a fly eye with a novel structure.

[0002]

2. Description of the Related Art A conventional fly's eye has a structure in which a large number of elements, both of which are convex lenses whose both surfaces are at the paraxial focal point of the other surface, are bundled together. For example, a mask pattern is baked in a manufacturing process of a semiconductor integrated circuit. It is used as a condensing optical system for illuminating an object during a plugging operation. This condensing optical system is shown in FIG. In the figure, 1 is a fly eye, 2 is a Fresnel lens as a condenser lens, and 3 is an object to be illuminated (semiconductor device). In this case, it is necessary to illuminate the target object 3 with uniform brightness. Therefore, the conventional fly-eye 1 also considers that the packing density does not decrease (no gaps occur between the elements), The cross-sectional shape of each element 4 is a hexagonal shape as shown in FIG.

When light is incident on the fly-eye 1 at an incident angle within a certain angle range, as shown in FIG.
The principal ray m of the light flux incident on each element 4 of the fly's eye 1 has an emission angle of zero (parallel to the optical axis of each element 4) regardless of the incident angle β of the light, and the Fresnel lens 2 behind
It can be regarded that the telecentric luminous flux (the luminous flux parallel to the optical axis of the fly eye 1) is emitted from many object points having the object height. Therefore, if the Fresnel lens 2 is arranged so that its rear focal position F ₁ is at the exit surface position of the fly's eye 1, all the light fluxes will pass through the exit pupil obtained at its front focal position F _2. . Therefore, if the object 3 is placed at the front focus position F ₂ , all the light fluxes incident on the fly-eye 1 can be directed to a narrow area of the object 3 regardless of the incident angle,
It is possible to perform uniform illumination with sufficient brightness.

[0004]

The conventional fly-eye 1 having no anisotropy in cross-sectional shape is suitable when used as an optical element for simply illuminating with uniform brightness as described above. , In the case of a usage mode in which the incident angle of light is anisotropic (for example, when incident on the fly eye 1 from a wide angle range from the left and right in the horizontal direction, but from a narrow angle range from the vertical direction). May not always be appropriate. Further, it is difficult to structurally reduce the manufacturing cost in the configuration in which a large number of elements are bundled like a conventional fly eye. The present invention has been made based on the above background, and in various cases where the incident angle of light to the fly's eye has anisotropy, an optical system having an appropriate condensing function according to the anisotropy is provided. It is an object of the present invention to provide a novel fly eye that can be configured, and to provide a fly eye that can be manufactured at low cost.

[0005]

The fly-eye according to claim 1 for solving the above-mentioned problems is obtained by bundling a large number of elements, which are convex lenses, whose both surfaces are at the paraxial focal point of the other surface, without any gaps. Is characterized in that each element has a diamond shape in cross section.

According to a second aspect of the present invention, the fly's eye comprises two lens array plates having an equivalent refractive power and arranged at intervals, and a pair of opposing convex lens portions in each lens array plate share a lens optical axis. In addition, they are located at the focal positions of the convex lens portions on the other side.

According to a third aspect of the fly's eye, each convex lens portion of the lens array plate of the second aspect has a diamond shape.

[0008]

In FIGS. 5 to 8, in order that all the light fluxes incident on the fly eye 41 are effectively emitted from the fly eye 41, the inclination angle β of the principal ray m of the light flux incident on the fly eye 41 and the fly eye 41 The NA of the light flux emitted from 41 (referred to as emission NA) must match. On the other hand, since each element 40 of the fly-eye 41 has a rhombic cross-sectional shape and has different dimensions in two directions at right angles, the emission NA in the long diagonal direction and the emission NA in the short diagonal direction of the diamond are different. Therefore, the maximum value of the principal ray tilt angle (that is, the allowable light-receiving angle) for all the light fluxes incident on the fly's eye 41 to effectively exit from the fly's eye 41 is large in the long diagonal direction of the rhombus and is large in the short diagonal direction. Small to This characteristic is suitable for the incident light when the incident angle range of the incident light on the fly's eye 41 is wide in the horizontal direction and narrow in the vertical direction. However, this characteristic can be utilized depending on the configuration and purpose of the optical system using the fly-eye 41.

According to the fly's eye of claim 2, FIG.
As shown in (c) and (d), the luminous flux incident on each convex lens portion 40 'of the lens array plate 41'a on the incident side faces the convex lens portion 4 on the opposite side of the lens array plate 41'b on the outgoing side.
Pass 0 '. Since the pair of convex lens portions 40 'facing each other have equivalent refractive power, they have the same optical action as the element in claim 1.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the fly-eye according to the present invention is applied as an optical element in a receiving optical system of a laser radar will be described below with reference to FIGS. FIG. 1 is a plan view showing the internal structure of the laser radar, and FIG. 2 is a front view thereof. The laser radar 20 is mounted on a vehicle to detect the position (direction and distance) of the vehicle ahead, and includes a transmission optical system 21 that emits laser light inside, and the transmission optical system 2.
1. An angle detection optical system 22 for detecting the direction of laser light (transmitted light) emitted from 1 toward an object, the object (vehicle)
Receiving optical system 2 for receiving laser light (reflected light) reflected by
3 is provided in the case 24. In each figure, the scanning direction (horizontal direction) of the transmitted light is indicated by x, the direction of the transmitted light toward the object is indicated by y, and the vertical direction is indicated by z.

As shown in FIGS. 3 and 4, the transmission optical system 21 includes a laser light source 25 for emitting a high-frequency pulsed laser beam, a collimator lens 26 for collimating the emitted laser beam, and a parallel beam. Cylindrical lens 27 that collects light only in one vertical and horizontal direction (z direction in the figure), vari-angle cone mirror 2 that reflects laser light toward an object
8. A motor 30 is provided for rotating the rotary shaft 29 of the vari-angle cone mirror 28 at a constant rotational speed.
The rotation axis 29 coincides with the cone axis of the variangle cone mirror 28. Bali angle cone mirror 28
Is a step portion 28 in which the apex angle of the conical surface 28a gradually changes in the circumferential direction, and the apex angle of the conical surface 28a changes discontinuously at a position where the conical surface 28a makes one revolution.
The shape is such that c is formed.

As shown in FIG. 3, the angle detecting optical system 22 includes the transmitting optical system 21 and the angle detecting optical system 2.
2 and the above-mentioned vari-angle cone mirror 28, which is an optical component common to both, and a laser light source 3 for emitting laser light.
5, a converging lens 36 that converges the emitted laser light toward the variangle cone mirror 28, and the laser light reflected by the variangle cone mirror 28 is received to detect the light receiving position (light spot position). The position sensor 37 is a light receiving element. The position sensor 37 outputs a signal according to the actual light receiving position in the light receiving area.

A fly-eye 41 according to an embodiment of the present invention is used in the receiving optical system 23. That is, as shown in FIGS. 5 to 7, FIG. 8A, and FIG. 8B, the receiving optical system 23 includes a fly eye 41 according to an embodiment of the present invention, and an exit surface position of the fly eye 41. There is provided a Fresnel lens 42 as a condenser lens arranged so that the rear focal position F ₁ comes to the front side, and a light receiving element 43 arranged at the front focal position F ₂ of the Fresnel lens 42. As shown in FIG. 8A, the fly-eye 41 has a structure in which a large number of elements 40, which are convex lenses, both surfaces of which are at the paraxial focal point of the other surface are bundled and joined together as shown in FIG. In the present invention, as shown in FIGS. 6 and 8B, each element 40 has a rhombic cross-sectional shape.

The operation of detecting the position of an object by the laser radar will be described. Bali Angle Cone Mirror 2
The motor 8 is driven by a motor 30 via a rotary shaft 29 and rotates at a constant speed. Laser light source 2 of transmission optical system 21
5, pulsed laser light is emitted toward the conical surface 28a of the variangle cone mirror 28. The emitted laser light is emitted from the conical surface 28a of the variangle cone mirror 28.
Reflects at and goes toward the object. In this case, since the apex angle α of the conical surface 28a of the vari-angle cone mirror 28 gradually changes in the circumferential direction, the rotation direction of the vari-angle cone mirror 28 changes the reflection direction of the laser light on the conical surface 28a. . That is, in FIG. 3, the transmitted light is swayed to the left and right, and scanning is performed with a thin line-shaped light beam (schematically indicated by a line 31). In this case, Bali Angle Cone Mirror 2
When 8 is rotated once, one scan of the transmitted light is performed. Also, the scanning direction is not reciprocating but only one direction.

The laser light (transmitted light) reflected by the vari-angle cone mirror 28 becomes an elliptical light beam toward the object, irradiates the surface of the object in a thin line shape, and reflects the laser light (reflected light) on the surface of the object. ) Is the fly-eye 4 of the receiving optical system 23
It is incident on each element 40 of 1. Since both surfaces of each element 40 are placed at the paraxial focal point of the other surface, as shown in FIG.
The principal ray m of the laser light incident on is the incident angle β of the laser light.
The output angle is zero regardless of
It becomes parallel to the optical axis of 0). On the other hand, in the Fresnel lens 42, the rear focal position F ₁ is at the exit surface position of the fly's eye 41, so the laser light transmitted through the Fresnel lens 42 becomes a parallel light flux as shown in an enlarged view of the main part in FIG. All the laser beams incident on the fly's eye 41 are at the exit pupil (the light receiving element 43 at the front focus position F ₂ of the Fresnel lens 42).
The exit pupil as viewed from the front of FIG. The light receiving element 43 is located at the front focus position F _2.
Are arranged, all the laser light incident on the fly's eye 41 is received by the light receiving element 43 regardless of the incident angle β.
To reach. In this case, the light receiving element 43 may have the diameter of the exit pupil as the effective light receiving diameter, and does not needlessly need a large light receiving area. Thus, this receiving optical system 23
The laser light incident on the fly's eye 41 from a wide angle range can be received, and all the laser light incident on the fly's eye 41 can be received by the light receiving element 43 (however, as will be described later, the light is condensed). (Ignoring lens aberrations). That is, it is possible to simultaneously satisfy a wide light receiving angle and a high light receiving efficiency (the ratio of the light received by the light receiving element 43 to the light incident on the fly's eye 41).

Design problems in determining optical parameters for the fly-eye 41, the Fresnel lens 42, and the light-receiving element 43 of the receiving optical system 23, especially the Fresnel lens 42.
A brief description will be given of the problem in determining the focal length of the. In the above description, the aberration of the Fresnel lens 42 is neglected, but in reality, due to the aberration of the Fresnel lens 42, a light beam that deviates to the side of the light receiving element 43 also occurs. The degree becomes more remarkable as the focal length of the Fresnel lens 42 becomes shorter, when the effective diameter of the fly eye 41 is constant. Therefore, in order to increase the light receiving efficiency, the longer the focal length of the Fresnel lens 42 is, the better as to the problem of aberration. On the other hand, if the incident NA to the Fresnel lens 42 is constant, the longer the focal length of the Fresnel lens 42, the larger the pupil diameter. However, generating a pupil that is larger than the effective area of the light receiving element 43 leads to a decrease in light receiving efficiency. Therefore, there is an upper limit to the focal length of the Fresnel lens 42. On the other hand, in order for all the light fluxes incident on the fly-eye 41 to be effectively emitted from the fly-eye 41, the inclination angle of the incident light flux and the NA of the emitted light flux must match. N of the luminous flux emitted from this fly eye 41
Since A is the incident NA to the Fresnel lens 42, the maximum value of the principal ray inclination angle of the light beam incident on the fly's eye 41 eventually governs the NA of the Fresnel lens 42, and is combined with the effective light receiving diameter of the light receiving element 43. The upper limit of the focal length of the Fresnel lens 42 is defined. Depending on the optical parameters thus obtained, a large aberration is usually generated. In particular, with respect to the Fresnel lens 42, the focal length is too short, and large aberration occurs. Therefore, it becomes difficult to correct the generated aberration, and the final optical system parameter is finally determined by selecting the optimum solution that mediates the aberration.

By the way, in the laser radar 20 described above, since the scanning direction is only one direction in the horizontal direction, the receiving optical system 21 is required to be able to receive the reflected light beam from a wide angle range in the horizontal direction, while in the vertical direction. May be narrow. That is, the maximum principal ray tilt angle of the incident light flux to the fly eye 41 that is allowable for being received by the light receiving element 43 differs between the vertical direction and the horizontal direction (that is, the maximum allowable principal ray tilt angle of the incident light flux is anisotropic. There is a nature). That is,
As a receiving optical system of the laser radar, it is suitable that the light receiving angle is wide in the horizontal direction and narrow in the vertical direction. However, since each element 41 of the fly-eye 41 in the present invention has a rhombic cross section having a long diagonal line in the scanning direction, it is compared with the case where the cross section of the element is a non-anisotropic shape such as a square or a regular hexagon. Then, the light receiving angle in the vertical direction is narrow, but the light receiving angle in the horizontal direction is wide. Even if the allowable light receiving angle in the vertical direction is narrow, the performance of the laser radar 20 that scans in the horizontal direction is not impaired. Therefore, the receiving optical system 23 has a wide light receiving angle as the receiving optical system of the laser radar. The cross-sectional shape of the element 40 in the illustrated example has an allowable light-receiving angle of ± 1 in the horizontal direction, for example.
It is set to 0 ° and ± 3 ° in the vertical direction. The aspect ratio of the rhombus cross section of the element 40 may be appropriately set in consideration of both the scan angle range and the required light receiving angle with respect to the vertical direction.

As described above, in the fly-eye 41, the cross section of each element 40 is a rhombus, the long diagonal direction is the horizontal direction (scan direction), and the short diagonal direction is the vertical direction. Has a large output NA,
The emission NA in the vertical direction is small. A small vertical incidence NA of the fly's eye 41 leads to a small vertical exit pupil diameter of the Fresnel lens 42 (when the focal length of the Fresnel lens 42 is constant). The smaller the exit pupil diameter, the smaller the area of the light receiving element 4
Since the light diverging from 3 can be surely eliminated, the light receiving efficiency is improved.

FIGS. 8 (c) and 8 (d) show a fly eye 41 'having substantially the same function as the fly eye 41 in which the elongated elements 40 are bundled but having a different structure. As shown in FIG. 8C, the fly's eye 41 'includes two lens array plates 4 having an equivalent refractive power and arranged at intervals.
1'a, 41'b, and as shown in FIG. 8D, a pair of convex lens portions 40 'facing each other in each lens array plate 41'a, 41'b share the lens optical axis, and They are at the focal positions of the convex lens portions 40 'on the other side. The shape of each convex lens portion 40 'on the lens array plates 41'a and 41'b is the same as that of the fly eye 41 described above.
The element 40 has a diamond shape similar to that of the element 40 of FIG.
It works the same as the individual element 40 of 1. The fly-eye 41 'made of this lens array plate is inferior in optical accuracy to the fly-eye 41 in which elements are bundled, because it is difficult to match the optical axes of the incident side and the exit side with sufficiently high accuracy, but In the application of radar, for example, unlike the case of illuminating an object at the time of burning a mask pattern in the manufacturing process of a semiconductor integrated circuit, almost strict accuracy is not required, so this lens array plate structure is adopted. can do. Further, the fly eye having this structure can be manufactured at a lower cost than the structure in which the elements are bundled. When the incident angle of the light 41 'to the fly's eye does not have anisotropy, the shape of each convex lens portion 40' on the lens array plates 41'a and 41'b is preferably a hexagon rather than a rhombus.

The fly's eye of the present invention is not limited to use as an optical element in the receiving optical system of a laser radar. In particular, the fly's eye according to claim 1 or 3 is an optical system for illuminating, for example, when the incident angle of the incident light is anisotropic (that is, from a wide angle range from the left and right in the horizontal direction). Is incident, but light is incident from a narrow angle range from the vertical direction), it can be applied as an optical element for efficiently condensing the light incident on the fly's eye into a narrow fixed area. In addition, the present invention can be applied to various cases in which an incident angle of light on a fly's eye has anisotropy and it is desirable to configure an optical system having an appropriate condensing function according to the anisotropy.

[0021]

According to the first aspect of the present invention, since each element has a rhombic cross section, the maximum value of the principal ray tilt angle for all the light flux incident on the fly eye to effectively exit from the fly eye. (That is, the light receiving angle) has a characteristic that it is large in the long diagonal direction of the diamond and small in the short diagonal direction. Therefore, in various cases where the incident angle of light to the fly's eye has anisotropy, an optical system having an appropriate condensing function according to the anisotropy can be realized by the fly's eye of the present invention. That is, it can be used as an optical element in various optical systems in which the anisotropy of the fly eye is appropriate, such as a receiving optical system of a laser radar.

According to the second aspect, the fly eye has only two.
Since it is composed of a single lens array plate, it can be manufactured at extremely low cost. In particular, it is suitable for cases such as a laser radar that does not require particularly strict accuracy.

[Brief description of drawings]

FIG. 1 is a plan view showing an internal structure of a laser radar using a fly-eye according to an embodiment of the present invention as an optical element of a receiving optical system.

FIG. 2 is a front view showing an internal structure of the laser radar.

FIG. 3 is an enlarged view showing only a transmission optical system and an angle detection optical system in FIG.

FIG. 4 is a view on arrow A in FIG.

5 is an enlarged view of a receiving optical system in the laser radar of FIG. 1 using the fly-eye according to the embodiment of the present invention.

FIG. 6 is a left side view of FIG.

FIG. 7 is an enlarged view of a main part in FIG.

8 (a) is an enlarged view of one element of the fly eye in FIG. 5, FIG. 8 (b) is a left side view of FIG. 8 (a), and FIG. 8 (c) is the fly of claim 2. A side view showing an embodiment of the eye, and FIG. 6D is an enlarged view of a main part in FIG.

FIG. 9 is a front view of an illumination optical system in a semiconductor manufacturing process using a conventional fly's eye.

10A is an enlarged view of one element of the fly eye in FIG. 9, and FIG. 10B is a left side view of FIG.

[Explanation of symbols]

 20 laser radar 21 transmission optical system 23 reception optical system 40 fly eye element 40 'convex lens portion 41, 41' fly eye 41'a, 41'b lens array plate 42 Fresnel lens 43 light receiving element

 ─────────────────────────────────────────────────── ─── Continued Front Page (72) Inventor Geiei Takeyama 8-6-27 Akasaka, Minato-ku, Tokyo Skyplaza Akasaka 201 Fujii Optical Co., Ltd.

Claims (3)

[Claims] 1. A fly-eye, characterized in that a large number of elements, each of which is a convex lens located on the paraxial focal point of the other surface of the other surface, are bundled together without a gap, and each of these elements has a rhombic cross section. . 2. A two-lens array plate having an equivalent refracting power, which is arranged at a distance from each other, and a pair of opposing convex lens portions in each lens array plate share a lens optical axis and are arranged on opposite sides of each other. A fly eye that is located at the focal point of the convex lens. 3. The fly eye according to claim 2, wherein each convex lens portion of the lens array plate has a diamond shape.