JP2012208227A - Point light source optical system, optical device, and manufacturing method of point light source optical system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a point light source optical system capable of generating fine light beams easily without using a diffraction optical element that requires advanced techniques and huge costs.SOLUTION: A point light source optical system comprises: a light source 1, a collimator lens 2 for converting light emitted from the light source 1 into an approximately parallel light beam; a first diffraction mechanism 3 for diffracting the light beam passed through the collimator lens; a second diffraction mechanism 6 for diffracting the light beam passed through the first diffraction mechanism 3; a third diffraction mechanism 9 for diffracting the light beam passed through the second diffraction mechanism 6; and a fourth diffraction mechanism 12 for diffracting the light beam passed through the third diffraction mechanism 9. The first diffraction mechanism 3 to the fourth diffraction mechanism 12 include diffraction optical elements 5, 8, 11 and 13 for diffracting the incident light beams into a predetermined direction and light guide parts 4, 7, 10 and 14 for guiding the light beams diffracted by the diffraction optical elements 5, 8, 11 and 13 to a predetermined direction.

Description

  The present invention relates to a point light source optical system, an optical apparatus including the point light source optical system, and a method for manufacturing the point light source optical system.

  Conventionally, as a scanning image display device that displays an image by scanning a laser light source two-dimensionally using a scanning mirror such as a MEMS mirror or a galvanometer mirror, for example, a focus-free projector or a head using an eyepiece optical system in combination There is a mounted display. However, the laser light source has a problem that the specular reflection is difficult to remove because the luminous flux does not spread as a characteristic, and it is costly to ensure safety.

  Therefore, an apparatus that easily generates a thin light beam by diffracting light twice by a diffractive optical element after making light from an LED light source into a substantially parallel light beam by a collimator lens is disclosed (for example, see Patent Document 1). .

JP 2010-276981

  However, in the conventional point light source optical system, when the light guide material is made thin in order to reduce the exit surface of the light source, the light beam emitted from the diffractive optical element is reflected in the light guide member, and a part thereof is diffractive optically again. The light enters the element and is emitted in a direction different from the desired direction, and light is wasted. In order to solve this problem, it is necessary to use a diffractive optical element having a large diffraction angle. However, in order to manufacture such a diffractive optical element, a high level of technology and a great deal of cost are required. In view of such a problem, an object of the present invention is to provide a point light source optical system that easily generates a thin light beam without requiring high technology and great cost.

  In order to solve the above problems, in the present invention, a light source, a collimator lens that converts light emitted from the light source into a substantially parallel light beam, and a first diffraction mechanism that diffracts the light beam that has passed through the collimator lens; A second diffraction mechanism for diffracting the light beam that has passed through the first diffraction mechanism, a third diffraction mechanism for diffracting the light beam that has passed through the second diffraction mechanism, and the third diffraction mechanism. A fourth diffractive mechanism for diffracting the passed light beam, and the first to fourth diffractive mechanisms diffract the incident light beam in a predetermined direction and the diffractive optical element. A point light source optical system comprising: a light guide unit that guides the light beam diffracted by the element in a predetermined direction.

  In the present invention, the recording material of the diffractive optical element is fixed to a light guide that guides diffracted light diffracted by the diffractive optical element in a predetermined direction when the diffractive optical element is used, and one laser beam is After being separated into two laser beams, one laser beam is irradiated onto the recording material in the same direction as the light is incident when the diffractive optical element diffracts the light, and at the same time, the other laser beam is irradiated with the other laser beam. A method of manufacturing a diffractive optical element is provided, wherein a diffraction grating is formed by making the light incident from the surface of the light guide unit from which the diffracted light is emitted.

  According to the present invention, it is possible to provide a point light source optical system that easily generates a thin light beam without using a diffractive optical element that requires high technology and great cost.

It is a perspective view (conceptual figure) which shows the point light source optical system of 1st Embodiment of this application. It is explanatory drawing of a diffraction mechanism. (A) shows a state where a part of the light beam emitted from the transmissive holographic optical element is totally reflected in the thin plate-shaped light guide material and then incident on the transmissive holographic optical element again. (B) shows the diffraction angle θ for preventing the light from entering the transmissive holographic optical element again after being totally reflected in the thin plate-shaped light guide material. It is explanatory drawing of the point light source optical system of 1st Embodiment of this application. (A) has shown until the light beam inject | emitted from LED permeate | transmits the 1st diffraction mechanism and the 2nd diffraction mechanism, and is inject | emitted. (B) shows the state of refraction when the light diffracted by the reflective holographic optical element passes through the adhesive layer and the wedge-shaped light guide. It is explanatory drawing of the point light source optical system of 2nd Embodiment of this application. (A) has shown until the light beam inject | emitted from LED permeate | transmits the 1st diffraction mechanism and the 2nd diffraction mechanism, and is inject | emitted. (B) shows the light beam emitted from the second diffraction mechanism until it passes through the third diffraction mechanism and the fourth diffraction mechanism and is emitted. It is a perspective view (conceptual figure) which shows the point light source optical system used for the optical apparatus of 3rd Embodiment of this application. (A) is explanatory drawing which shows the optical apparatus of 3rd Embodiment of this application. (B) is explanatory drawing which shows the modification of the optical instrument of 3rd Embodiment. It is explanatory drawing which shows the manufacturing method of 4th Embodiment of this application.

(First embodiment)
Hereinafter, a first embodiment of the present invention will be described with reference to FIGS. 1 to 3. FIG. 1 is a perspective view (conceptual diagram) of a point light source optical system 100 according to the first embodiment of the present invention. In the perspective view, for the sake of explanation, the direction from the left front to the back right is defined as the X axis, the direction from the right front to the left back is defined as the Y axis, and the vertical direction is defined as the Z axis.

  As shown in FIG. 1, the point light source optical system 100 of the first embodiment includes an LED 1 as a light source and a collimating lens 2 that converts a light beam from the LED 1 into a substantially parallel light beam (a light beam along the Z axis). The first diffractive mechanism 3 is a reflection holographic optical element 5 (hereinafter referred to as “HOE”) which is a diffractive optical element that diffracts a light beam transmitted through the wedge-shaped light guide material 4. The wedge-shaped light guide 4 guides the light beam emitted from the reflective HOE 5 along the X axis and guides it to the second diffraction mechanism 6.

  Here, the apex angle θ4 of the wedge-shaped light guide material 4 shown in FIG. 3A is an angle formed by a light beam that travels by entering the wedge-shaped light guide material 4 from the reflective HOE 5 and a surface on which the light beam enters. It is formed substantially the same as θ5. As a result, in the first diffractive mechanism 3, the inside of the wedge-shaped light guide 4 is advanced as a light beam substantially parallel to the X axis, and loss of light due to reflection in the wedge-shaped light guide 4 can be prevented. .

  The second diffractive mechanism 6 is composed of a thin plate-shaped light guide material 7 and a reflective HOE 8, and the light beam (X-axis direction) emitted from the first diffractive mechanism 3 is transmitted through the thin plate-shaped light guide material 7 and reflected. The light enters the mold HOE 8, is diffracted, enters the thin light guide 7 again, travels along the Z axis while being totally reflected in the thin light guide 7, and is guided to the third diffraction mechanism 9.

  The third diffractive mechanism 9 includes a wedge-shaped light guide material 10 and a reflective HOE 11, and a light beam (in the Z-axis direction) emitted from the second diffractive mechanism 6 is transmitted through the wedge-shaped light guide material 10 and reflected. The light enters the mold HOE 11, is diffracted, enters the wedge-shaped light guide 10 again, travels along the Y-axis along the wedge-shaped light guide 10, and is guided to the fourth diffraction mechanism 12. The effect of making the light guide material 10 in a wedge shape is the same as the effect in the first diffraction mechanism.

  The fourth diffractive mechanism 12 includes a reflective HOE 13 and a rod-shaped light guide material 14, and a light beam (Y-axis direction) emitted from the third diffractive mechanism 9 is transmitted through the rod-shaped light guide material 14 and reflected. The light enters the mold HOE 13, is diffracted, enters the rod-shaped light guide material 14 again, travels along the Z axis while being totally reflected in the light guide material, and is emitted from the injection portion 14 a. Note that the first to fourth diffraction mechanisms 3, 6, 9, and 12 use first-order diffracted light as diffracted light.

  As described above, the light emitted from the LED 1 passes through the first to fourth diffractive mechanisms 3, 6, 9, and 12 sequentially to become a thin light beam, and the light from the rod-shaped light guide material 14 of the fourth diffractive mechanism 12. Injected from the injection unit 14a. For example, if the thickness of the thin light guide 7 in the X-axis direction is 50 μm and the thickness of the rod-shaped light guide 14 in the Y-axis direction is 50 μm, a light flux of 50 μm × 50 μm square can be obtained. Become.

  In general, in a point light source optical system using a diffractive optical element and a light guide material, as shown in FIG. 2B, for example, if a light source of 50 μm × 50 μm square is obtained, The thickness must be 50 μm. If the width of substantially parallel light transmitted from the light source 16 through the collimating lens 17 is, for example, 5,000 μm, at least tan θ> in order to pass all the light of 5,000 μm width through the light guide member having a thickness of 50 μm. When the transmission type HOE 18 having a diffraction angle of 50 must be used and the condition of tan θ> 50 is not satisfied, a part of the light is thin-plate-shaped light guide 15 as shown in FIG. Then, the light enters the transmission type HOE 18 again and leaks out of the diffraction mechanism 20, and light is wasted. This is the same even when a reflective HOE is used. However, in order to manufacture a HOE having a diffraction angle θ satisfying tan θ> 50, a high technical skill and a great cost are required.

  In contrast, the point light source optical system 100 according to the first embodiment includes four diffraction mechanisms from the first diffraction mechanism 3 to the fourth diffraction mechanism 12. As a result, as shown in FIG. 3A, for example, light having a width of 5,000 μm transmitted through the collimator lens 2 is once approximately 706 μm wide by the reflective HOE 5 and the wedge-shaped light guide material 4 of the first diffraction mechanism 3. The light is diffracted by the second diffractive mechanism 6 including the thin light guide material 7 having a thickness of 50 μm (dimension in the X-axis direction) and then having a width of 50 μm (X-axis direction). ) Is emitted from the thin plate-shaped light guide material 7. In this case, the reflection type HOEs 5 and 8 have a diffraction angle at which tan θ10 is about 7.08. In the above example, if tan θ10 is larger than 5√2, it is possible to prevent the light reflected in the thin light guide 7 in the second diffraction mechanism 6 from entering the reflective HOE 8 again.

  The light beam emitted from the second diffractive mechanism 6 is still 5,000 μm in the Y-axis direction although the width in the X-axis direction is 50 μm at this time. Therefore, the light beam emitted from the second diffraction mechanism 6 is diffracted by the third diffraction mechanism 9 so that the width of 5,000 μm (dimension in the Y-axis direction) becomes about 706 μm width (dimension in the Z-axis direction). To do. The light beam emitted from the third diffractive mechanism 9 is diffracted by the fourth diffractive mechanism 12 including the rod-shaped light guide material 14 having a dimension in the Y-axis direction of 50 μm, so that the width is 50 μm (dimension in the Y-axis direction). And In this case, the reflection type HOEs 11 and 13 also have a diffraction angle at which the value corresponding to tan θ10 is about 7.08. In the above example, if tan θ10 is larger than 5√2, it is possible to prevent the light reflected in the rod-shaped light guide material 14 in the fourth diffraction mechanism 12 from entering the reflective HOE 13 again. Therefore, the point light source optical system 100 according to the first embodiment, unlike the point light source optical system that requires the HOE having a diffraction angle satisfying tan θ> 50, requires high technical power and great cost in manufacturing the HOE. It can not be said.

  Further, by making the refractive indexes of the wedge-shaped light guide materials 4 and 10, the thin plate light guide material 7 and the rod-shaped light guide material 14 used for the first to fourth diffraction mechanisms 3, 6, 9 and 12 substantially the same. Since the HOE having the same diffraction angle can be used in the first to fourth diffraction mechanisms 3, 6, 9, and 12, the cost can be reduced.

Further, the reflective HOE 5 and the wedge-shaped light guide material 4 are bonded by an adhesive. FIG. 3B shows that the light diffracted by the reflective HOE 5 is refracted at the boundary surface between the reflective HOE 5 and the adhesive layer 18 and at the boundary surface between the adhesive layer 18 and the wedge-shaped light guide material 4. It shows how it is. The refractive index of the reflective HOE 5 is n1, the refractive index of the wedge-shaped light guide 4 is n2, the refractive index of the adhesive layer 18 is n3, the incident angle from the reflective HOE 5 to the adhesive layer 18 is θ1, and the adhesive layer 18 When the incident angle to the wedge-shaped light guide material is θ3, the diffracted light does not cause total reflection when incident on the wedge-shaped light guide material. Therefore, the wedge-shaped light guide material 4 and the reflective HOE 5 are bonded. In general, the adhesive 18 is
n1 * sinθ1 <n3 * sinθ3 <n2
It is necessary to satisfy. In general, since the adhesive 18 is a resin, it is very difficult to control the refractive index. there,
n3> n1, n3> n2
The refractive index management of the adhesive 18 can be facilitated by using the adhesive 18 that becomes. This is not limited to the first diffraction mechanism 3, and the same applies to the second to fourth diffraction mechanisms 6, 9, and 12.

  As the adhesive 18, a transparent ultraviolet curable resin can be used. For example, the product “Norland Optical Adhesives” of “Norland Products, Inc.” is used.

  In the point light source optical system 100 according to the first embodiment, four diffraction mechanisms are provided from the first diffraction mechanism 3 to the fourth diffraction mechanism 12, but more than that may be used. In this case, the structure is complicated, but it is possible to use HOE having a smaller diffraction angle. Further, if the thickness of the member corresponding to the light guides 7 and 14 is reduced without using the HOE having a small diffraction angle, a thinner light beam can be emitted.

  For the wedge-shaped light guide materials 4 and 10, the thin plate light guide material 7 and the rod-shaped light guide material 14, optical resins such as acrylic resin and polycarbonate resin, glass, and the like can be used.

  Further, the number and arrangement of the wedge-shaped light guide materials in the entire point light source optical system are not limited to this embodiment, and it is also possible to use a thin plate light guide material for the first diffraction mechanism or the third diffraction mechanism. Moreover, it is also possible to use a wedge-shaped light guide material instead of the thin-plate light guide materials of the second diffraction mechanism and the fourth diffraction mechanism. However, for example, since it is not easy to manufacture a thin wedge-shaped light guide material having a thickness of 50 μm even at the thickest part in the Z-axis direction, there is a diffraction mechanism close to the light source as in the first embodiment. It is more efficient to arrange a wedge-shaped light guide material having a certain thickness and use a thin plate light guide material in a diffraction mechanism far from the light source.

  Instead of the wedge-shaped light guide material, a plate-shaped light guide material having the same dimension in the Z-axis direction as the dimension in the Z-axis direction of the light emitting surface of the wedge-shaped light guide material may be used. In this case, the thickness increases, but the manufacturing cost can be reduced.

  In the first embodiment, the dimension of the third diffraction mechanism 9 in the X-axis direction is matched with the dimension of the light beam narrowed by the first diffraction mechanism 3 and the second diffraction mechanism 6 in the X-axis direction. However, a diffraction mechanism having the same configuration as that of the first diffraction mechanism 3 may be disposed as the third diffraction mechanism 9. Similarly, a diffraction mechanism having the same configuration as that of the second diffraction mechanism 6 may be arranged as the fourth diffraction mechanism 12. In this case, the size of the point light source optical system is increased, but the manufacturing cost can be reduced.

  In the first embodiment, after the width of the light beam is narrowed in one direction by the first diffraction mechanism 3 and the second diffraction mechanism 6, the width in the direction perpendicular thereto is reduced to the third diffraction mechanism 9 and the fourth diffraction mechanism 12. Although the light flux is narrowed by narrowing, the order does not necessarily have to be such. That is, in the first embodiment, the light emitted from the collimator lens is diffracted in the order of the X-axis direction, the Z-axis direction, the Y-axis direction, and the Z-axis direction. The diffraction may be performed in the order of the Y-axis direction, the Z-axis direction, and the X-axis direction, or may be performed in the other order.

  The reflective HOEs 5, 8, 11, and 13 are desirably so-called thick holograms (volume holograms). With such a thick hologram, the diffraction ratio (diffraction efficiency) to the first-order diffracted light can be increased.

  The diffraction mechanism of the first embodiment uses a reflection type HOE. However, a part of the diffraction mechanisms may be a diffraction mechanism using a transmission type HOE as in the second embodiment to be described later.

(Second Embodiment)
Hereinafter, a second embodiment of the present invention will be described with reference to FIG. The difference from the first embodiment is that a reflective HOE is used in the first embodiment, whereas a transmissive HOE is used in this embodiment. The configuration is the same as that of the first embodiment.

  That is, as shown in FIG. 4A, the point light source optical system 120 of the second embodiment has an LED 18 as a light source, and a collimating lens 19 that makes a light beam from the LED 18 a substantially parallel light beam. The first diffraction mechanism 20 includes a transmission type HOE 21 that diffracts the light beam emitted from the collimating lens 19 and a wedge-shaped light guide material 23 that guides the light beam emitted from the transmission type HOE 21 to the second diffraction mechanism 22. ing. The second diffraction mechanism 22 includes a thin plate-shaped light guide material 24 and a transmission type HOE 25, and the light beam emitted from the first diffraction mechanism 20 is incident on the transmission type HOE 25, diffracted, and the thin plate-shaped light guide material 24. And is guided to the third diffraction mechanism 26 while being totally reflected in the thin plate-shaped light guide 24.

  As shown in FIG. 4B, the third diffractive mechanism 26 includes a transmissive HOE 27 and a wedge-shaped light guide 28, and the light beam emitted from the second diffractive mechanism 22 is transmitted to the transmissive HOE 27. Incident, diffracted, incident on the wedge-shaped light guide 28, and guided to the fourth diffraction mechanism 29. The fourth diffractive mechanism 29 includes a transmissive HOE 30 and a rod-shaped light guide 31, and the light beam emitted from the third diffractive mechanism 26 enters the transmissive HOE 30, is diffracted, and enters the rod-shaped light guide 31. Then, the light is emitted from the emission part 31 a while being totally reflected in the rod-shaped light guide 31. Note that the first and second diffraction mechanisms 20, 22, 26, and 29 all use first-order diffracted light as diffracted light.

  As described above, the light emitted from the LED 18 becomes a thin light beam by being repeatedly diffracted by the diffraction mechanisms 20, 22, 26 and 29, and is emitted from the emission part 31 a of the rod-shaped light guide material 31. For example, if the thickness of the thin light guide 24 is 50 μm and the thickness of the bar light guide 31 is 50 μm, a light beam of 50 μm × 50 μm square can be obtained.

  As in the first embodiment, by providing the first to fourth diffraction mechanisms 20, 22, 26, 29, high technical power and high cost are not required in the manufacture of HOE, and light from the light source is emitted. The point light source optical system does not waste.

  Further, by using the wedge-shaped light guide materials 23 and 28 as the light guide material in the first and third diffraction mechanisms 20 and 26, the light beams emitted from the transmission type HOEs 21 and 27 are reflected in the light guide material. It is possible to prevent the light from entering the transmission type HOEs 21 and 27 again. That is, the apex angles θ6 and θ7 of the wedge-shaped light guide materials 23 and 28 are angles formed by the light flux that travels from the transmission type HOE 21 and 27 to the wedge-shaped light guide materials 23 and 28 and the surface on which the light flux enters. The angles θ8 and θ9 are substantially the same. As a result, in the first and third diffraction mechanisms 20 and 26, the inside of the wedge-shaped light guide materials 23 and 28 proceeds without being totally reflected, and light loss due to reflection in the wedge-shaped light guide materials 23 and 28. Can be prevented.

  Furthermore, by making the refractive indexes of the wedge-shaped light guide materials 23, 28, the thin plate-shaped light guide material 24, and the rod-shaped light guide material 31 used in the first to fourth diffraction mechanisms 20, 22, 26, 29 substantially the same. Since the diffraction mechanisms 1 to 4 can use HOEs having the same diffraction angle, the cost is reduced.

Assuming that the refractive index of the transmission type HOE 21 is n1, the refractive index of the wedge-shaped light guide material 23 is n2, and the refractive index of an adhesive (not shown) that bonds the transmission type HOE 21 and the wedge-shaped light guide material 23 is n3. As in the embodiment, in order to prevent total reflection before the diffracted light enters the light guide and to facilitate the refractive index management,
n3> n1, n3> n2
It is good to use the adhesive which becomes. This is not limited to the first diffraction mechanism 3, and the same applies to the second to fourth diffraction mechanisms 22, 26, and 29.

  As the adhesive, a transparent ultraviolet curable resin can be used. For example, the product “Norland Optical Adhesives” of “Norland Products, Inc.” is used.

  In the second embodiment, four diffractive mechanisms are provided from the first diffractive mechanism 20 to the fourth diffractive mechanism 29, but may be more than that. In this case, the structure is complicated, but it is possible to use HOE having a smaller diffraction angle. Further, if the thickness of the member corresponding to the light guide portions 24 and 31 is reduced without using the HOE having a small diffraction angle, a thinner light beam can be emitted.

  For the wedge-shaped light guide materials 23 and 28, the thin plate light guide material 24, and the rod-shaped light guide material 29, an optical resin such as acrylic resin or polycarbonate resin, glass, or the like can be used.

  The number and arrangement of the wedge-shaped light guide materials in the entire point light source optical system are not limited to this embodiment, and it is also possible to use a thin plate light guide material for the first diffraction mechanism 20 or the third diffraction mechanism 26. In addition, a wedge-shaped light guide material can be used in place of the thin plate-shaped light guide materials of the second diffraction mechanism 22 and the fourth diffraction mechanism 29. However, since it is not easy to manufacture a thin wedge-shaped light guide material having a thickness of 50 μm at the thickest part in the Z-axis direction, for example, the diffraction mechanism close to the light source is present as in the first embodiment. It is more efficient to arrange a wedge-shaped light guide material having a certain thickness and arrange a thin plate light guide material in a diffraction mechanism far from the light source.

  Instead of the wedge-shaped light guide material, a plate-shaped light guide material having the same dimension in the Z-axis direction as the dimension in the Z-axis direction of the light emitting surface of the wedge-shaped light guide material may be used. In this case, the thickness increases, but the manufacturing cost can be reduced.

  In the second embodiment, the third diffraction mechanism 26 may be adjusted to the width of the light beam emitted from the second diffraction mechanism 22 as in the first embodiment. A diffraction mechanism having the same configuration may be used for the third diffraction mechanism 26. Similarly, the fourth diffraction mechanism 29 may be matched with the width of the light beam emitted from the third diffraction mechanism 26, but a diffraction mechanism having the same configuration as the second diffraction mechanism 26 may be used.

  In the second embodiment, after the width of the light beam is narrowed in one direction by the first diffraction mechanism 20 and the second diffraction mechanism 22, the width in the direction perpendicular thereto is reduced to the third diffraction mechanism 26 and the fourth diffraction mechanism 29. Although the light flux is narrowed by narrowing, the order does not necessarily have to be such.

  The diffraction mechanisms 20, 22, 26, and 29 of the second embodiment all use transmissive HOEs, but some of the diffraction mechanisms use reflective HOEs as in the first embodiment. A diffraction mechanism may be used.

(Third embodiment)
Hereinafter, a retinal scanning display device 300 according to the third embodiment will be described as an example of an optical apparatus including the point light source optical system according to the present invention with reference to FIGS. 5 and 6. FIG. 5 is a perspective view (conceptual diagram) for explaining an example of the point light source optical system 200 used in the retina operation type display device 300 of the third embodiment.

  In the point light source optical system 200, as in the first embodiment, the LEDs 33, 34, and 35 as light sources, the collimating lenses 36, 37, and 38, the wedge-shaped light guide 39, and the reflective HOEs 40, 41, and 42 are used. A first diffraction mechanism 43 comprising: a thin plate-shaped light guide material 44 and a second diffraction mechanism 48 comprising reflective HOEs 45, 46, 47; a wedge-shaped light guide material 49 and reflective HOEs 50, 51, 52; A third diffraction mechanism, and a fourth diffraction mechanism 56 composed of a rod-shaped light guide 54 and a reflective HOE 55.

  The point light source optical system according to the third embodiment includes, as a light source, an LED (R) 33 that emits red light, an LED (G) 34 that emits green light, and an LED (B) that emits blue light. 35 are arranged at predetermined intervals, and a collimating lens (R) 36, a collimating lens (G) 37, and a collimating lens (B) 38 are arranged correspondingly. Further, in the first, second, and third diffraction mechanisms, the reflection type HOE (R) 40, 45, 50, 55 reflection type set to have a predetermined diffraction angle according to the wavelength of light of RGB three colors. HOE (G) 41, 46 (not shown), 51, 55 and reflective HOE (B) 42, 47 (not shown), 52, 55 are arranged corresponding to the three colors of RGB of the LED. . The reflection type HOE 55 of the fourth diffraction mechanism is formed by superimposing the reflection type holograms corresponding to RGB colors on three layers.

  With the above-described configuration, each of the three colors RGB is diffracted by the first diffraction mechanism 43 to the fourth diffraction mechanism 56 to become a thin light beam, and the emission portion 57 of the rod-shaped light guide material 54. Therefore, it is possible to display a color image based on the video signal by changing the intensity of RGB light in the retina operation type display device 300. Note that light sources of colors other than RGB may be used according to the color of the display image, and the number of light sources may be other than three.

  For the wedge-shaped light guide materials 39 and 49, the thin plate light guide material 44, and the rod-shaped light guide material 54, an optical resin such as acrylic resin or polycarbonate resin, glass, or the like can be used.

  If the refractive indexes of these light guide materials are substantially the same, the first diffraction mechanism 43 to the fourth diffraction mechanism 56 can use the HOE having the same diffraction angle, so that the cost can be reduced.

The refractive index of the reflective HOE (R) 40 is n1, the refractive index of the wedge-shaped light guide material 39 is n2, and the refractive index of the adhesive (not shown) that bonds the reflective HOE (R) 40 and the wedge-shaped light guide material 39 to each other. Assuming that the rate is n3, as in the first embodiment, in order to prevent total reflection before the diffracted light enters the light guide material and to facilitate refractive index management,
n3> n1, n3> n2
It is good to use the adhesive which becomes. Note that this is not limited to the adhesion between the reflective HOE (R) 40 and the wedge-shaped light guide 39, but the reflective HOE (G) 41, the reflective HOE (B) 42, and the wedge-shaped light guide. The same applies to the adhesion between the first diffraction mechanism 43 and the second diffraction mechanism 48, 53, and 56 as well as the first diffraction mechanism 43.

  As the adhesive, a transparent ultraviolet curable resin can be used. For example, the product “Norland Optical Adhesives” of “Norland Products, Inc.” is used.

  In the point light source optical system 200 according to the third embodiment, four diffractive mechanisms are provided from the first diffractive mechanism 43 to the fourth diffractive mechanism 56, but may be more than that. In this case, the structure becomes complicated, but it is possible to use HOE having a smaller refraction angle. Further, if the thickness of the member corresponding to the light guides 44 and 54 is reduced without using the HOE having a small diffraction angle, a thinner light beam can be emitted.

  The number and arrangement of the wedge-shaped light guide materials in the point light source optical system 200 are not limited to the present embodiment, and it is also possible to use a thin plate light guide material for the first diffraction mechanism 43 or the third diffraction mechanism 53. In addition, it is also possible to use the thin light guide material of the second diffraction mechanism 48 and the fourth diffraction mechanism 56 instead. However, since it is not easy to manufacture a thin wedge-shaped light guide material having a thickness of 50 μm at the thickest part in the Z-axis direction, for example, the diffraction mechanism close to the light source is present as in the first embodiment. It is more efficient to arrange a wedge-shaped light guide material having a certain thickness and to use a thin plate light guide material for the diffraction mechanism far from the light source.

  The third diffractive mechanism 53 has the same thickness as the first diffractive mechanism, although the thickness in the X-axis direction is reduced in accordance with the dimension in the X-axis direction of the light beam whose width is narrowed by the second diffractive mechanism 48. The diffraction mechanism having the configuration may be used as the third diffraction mechanism. Similarly, a diffraction mechanism having the same configuration as the second diffraction mechanism may be used for the fourth diffraction mechanism. In this case, the size of the point light source optical system is increased, but the manufacturing cost can be reduced.

  In the third embodiment, after the width of the light beam is narrowed in one direction by the first diffraction mechanism 43 and the second diffraction mechanism 48, the width in the direction perpendicular thereto is reduced to the third diffraction mechanism 53 and the fourth diffraction mechanism 56. Although the light flux is narrowed by narrowing, the order does not necessarily have to be such. In other words, in the third embodiment, the light emitted from the collimating lens is diffracted in the order of the X-axis direction, the Z-axis direction, the Y-axis direction, and the Z-axis direction. The diffraction may be performed in the order of the Y-axis direction, the Z-axis direction, and the X-axis direction, or may be performed in the other order.

  Further, the diffraction mechanisms 43, 48, 53, and 56 of the third embodiment all use reflective HOEs, but may be combined with a diffraction mechanism using transmissive HOEs as in the second embodiment described above. good.

  If the three-color optical paths of RGB in the wedge-shaped light guide material 39 of the first diffractive mechanism 43 and the thin plate-shaped light guide material 44 of the second diffractive mechanism 48 are simply arranged at intervals in the same member, There is a possibility that part of the light diffracted by the reflection type HOE enters another optical path, and these lights are mixed together. Therefore, it is effective to provide a boundary surface capable of total reflection in a part between adjacent optical paths. For example, as shown in FIG. 5, a gap 57 along the direction of the optical path can be provided. The gap portion 57 may be penetrated in the thickness direction of the light guide material, may be a groove shape, or may be a closed space embedded inside. By adopting such a configuration, the light beams of the three colors of RGB are totally reflected at the boundary surface, and the light beams can be prevented from intermingling.

  For light mixing, it is also effective to make the HOE a wavelength selective HOE. According to this, even if each light beam is mixed in the light guide material, only a light beam having a necessary wavelength can be selected and diffracted.

  The fourth diffraction mechanism 56 uses a reflective HOE 55 formed by superimposing three layers of diffraction gratings corresponding to light of each RGB color, but the first diffraction mechanism 43 to the third diffraction mechanism 53 Similarly, three HOEs corresponding to RGB may be provided.

  On the other hand, in the first diffraction mechanism 43 to the third diffraction mechanism 53, a reflection type HOE similar to the fourth diffraction mechanism 56 can be used. In this case, light of three colors RGB can be emitted from a single light source, and there is no need to separate the RGB optical paths, so that the apparatus can be made simple and small as in the first embodiment. . Note that the three-layer HOE 55 corresponding to light of each RGB color is not limited to the reflective type, and may be a transmissive type.

  Next, with reference to FIG. 6A, the overall configuration of the retina operation type display device 300 including the point light source optical system 200 of the third embodiment will be described. The retinal scanning display apparatus 300 has the point light source optical system 200 and a collimator lens 58 that converts light emitted from the emission unit 57 into substantially parallel light with the emission unit 57 of the point light source optical system 200 as a focal position. A movable mirror 59 as a scanning unit that scans the retina (fundus) 63 of the observer, which is the scanning surface, with substantially parallel light from the collimating lens, and a relay lens 60 that relays the light beam reflected by the movable mirror. And an image forming optical system 62 comprising an image forming lens 61 for forming an image of this light beam on the retina 63 of the observer, and a control unit 64 for controlling the brightness of the light emitted from the light source and the operation of the movable mirror. . Here, the light source is composed of the LEDs 33, 34, and 35 as described above, and radiates light of R, G, and B, respectively. At this time, the image signal (the image signal to be displayed on the retina of the observer ( Based on the input signal), the controller 64 controls the brightness of each light beam to be modulated and emitted. As described above, when the thickness of the light guide material is 50 μm, the point light source optical system emits light of about 50 μm square (light obtained by combining R, G, and B) from the emitting portion 57. Will be.

  In the retinal scanning display device 300, the movable mirror 59 as a scanning unit is configured by MEMS (Micro Electro Mechanical Systems). In addition, this scanning part is not limited to these, A conventionally well-known appropriate scanning means can be used. And this movable mirror is controlled by the control part 64 so that a mirror surface vibrates with respect to two axis | shafts of a horizontal direction and a perpendicular direction at a predetermined angle and a predetermined frequency, respectively. The predetermined frequency corresponds to the horizontal scanning frequency and the vertical scanning frequency. The movable mirror 59 is arranged by the imaging lens 61 of the imaging optical system 62 so that the mirror surface is substantially conjugate with the pupil 66 of the observation eye 65. With such a configuration, the movable mirror 59 virtually vibrates at the position of the observer's pupil 66, scans the light beam on the retina 63, and synthesizes an image according to the scanning angle. Therefore, based on the video signal, the intensity of RGB light emitted from the light sources 33, 34, and 35 is changed based on the video signal under the control of the control unit 64 in synchronization with the frequency of the movable mirror 59. Displayed images.

  Note that the light beam emitted from the emission unit 57 of the point light source optical system 200 and passed through the two optical systems of the collimating lens 58 and the imaging optical system 62 is a substantially parallel light beam on the pupil 66 of the observation eye 65. In the retina 63, it becomes conjugate with the emitting portion by the refractive power of the crystalline lens. Therefore, the size of one pixel of the image scanned on the retina is multiplied by the magnification of the optical system configured by the collimating lens, the relay optical system, and the crystalline lens 67 of the observation eye, with respect to the size of the emitting portion. Is equal to Although this naturally varies depending on the configuration of the optical system, it is usually required that the diameter of the emitting portion is several tens of μm in order to obtain a VGA level image.

  More specifically, the size of one pixel in the retina 63 in the observation eye 65 in which the focal length of the crystalline lens 67 is 17 mm in the image display with a visual field of 20 degrees in the horizontal direction is 10 μm. Therefore, if the focal length of the collimating lens disposed on the side of the emission unit 57 of the point light source optical system 200 is determined so that the magnification is 1/5, the diameter of the emission unit 57 can be set to 50 μm. In the case of the optical system as shown here, if it is assumed that a stop is provided in a portion optically conjugate with the retina between the relay lens 60 and the imaging lens 61 of the imaging optical system 62, the emission unit 57 is provided. It is assumed that an appropriate size is about 100 μm, which is slightly larger than 50 μm of the present embodiment. In order to display a higher resolution image, a thinner light beam is required. However, according to the present invention, this can also be realized.

  Alternatively, as in the modification of the third embodiment shown in FIG. 6B, the movable mirror 68 can be configured to be condensed light instead of parallel light. That is, the light from the emitting portion 57 of the point light source optical system 200 is converted into substantially parallel light by the collimating lens 69, the substantially parallel light from the collimating lens 69 is condensed by the movable mirror 68, and the imaging optical system 70 An image is formed on the retina 63 of the observer by the imaging lens 71 and the retina 63 is scanned. Such a configuration is advantageous in that since the objective relay lens 60 is not used, the retinal scanning display device 400 can be significantly reduced in size. In this case, the size of one pixel of the image scanned on the retina is calculated by multiplying the size of the emission unit 57 by the magnification of both the collimating lens 69 and the imaging lens 71. Therefore, although the light efficiency is somewhat reduced, the size of the emission portion 57 can be set to about 100 μm.

(Fourth embodiment)
Hereinafter, the manufacturing method of the diffraction member for point light source optical systems concerning a 4th embodiment of the present invention is explained, referring to FIG.

  In the manufacturing method according to the fourth embodiment, for example, a laser device 72, a beam splitter 73 that divides a laser emitted from the laser device 72 into object light and reference light, and emitted from the beam splitter as object light. A first mirror 74 that reflects the laser beam in a predetermined direction, a beam expander 75 on the object beam side that spreads the laser beam reflected by the first mirror 74 into a parallel light beam having a predetermined magnification, and a laser beam emitted from the beam expander. A second mirror 76 that reflects in the direction and a reference light side beam expander 77 that spreads the laser emitted from the beam splitter 73 as reference light into a parallel light beam with a predetermined magnification are prepared.

  Further, a holographic photosensitive material 79 is attached in advance to a wedge-shaped light guide material 78 used in the point light source optical system, and exposure is performed by causing object light and reference light to enter from the incident side and the emission side, respectively.

  The holographic photosensitive material 79 is very delicate and does not easily diffract due to bending or the like. In particular, in the point light source optical system according to the present application, since a light beam is emitted from the HOE at an acute angle, the diffraction pattern cannot be recorded correctly with a fine warp of the HOE. However, according to the above configuration, by integrating the wedge-shaped light guide material 78 and the HOE, the bending and warping of the HOE can be eliminated, and the diffraction pattern can be recorded with high accuracy.

  After exposure, processing according to the photosensitive material is performed to complete the HOE. For example, when a photosensitive material such as a silver salt emulsion that requires development processing is used, development processing, bleaching processing, drying processing, and the like are performed after exposure. On the other hand, when a photosensitive material such as a photopolymer that does not require development processing is used, it is completed after exposure by applying ultraviolet light or applying heat.

  In FIG. 7, the manufacturing of the reflective HOE is described. However, the same method can be used in the manufacturing of the transmissive HOE. As long as it is a light guide material used in the system, for example, a plate-shaped light guide material may be used. Furthermore, the generation method of the object light and the reference light is not limited to the above method, and can be appropriately changed as necessary.

  As described above, according to the present invention, it is possible to provide a diffractive optical element without a sophisticated technique, and to provide a point light source optical system with reduced costs.

1 LED
2 Collimating lens 3 First diffraction mechanism 4 Wedge-shaped light guide material 5 Reflective HOE
6 Second diffraction mechanism 7 Thin light guide 8 Reflective HOE
9 Third diffraction mechanism 10 Wedge-shaped light guide material 11 Reflective HOE
12 Fourth diffraction mechanism 13 Reflective HOE
14 Bar-shaped light guide material 14a Ejection part 15 Thin plate-shaped light guide material 16 Light source 17 Collimating lens 18 LED
19 Collimating lens 20 First diffraction mechanism 21 Transmission type HOE
22 Second diffraction mechanism 23 Wedge-shaped light guide 23
24 Thin plate-shaped light guide material 25 Transmission type HOE
26 Third diffraction mechanism 27 Transmission type HOE
28 Wedge-shaped light guide material 29 Fourth diffraction mechanism 30 Transmission type HOE
31 Bar-shaped light guide material 31a Ejection part 33 LED (R)
34 LED (G)
35 LED (B)
36 Collimating lens (R)
37 Collimating lens (G)
38 Collimating lens (B)
39 Wedge-shaped light guide 40 Reflective HOE (R)
41 Reflective HOE (G)
42 Reflective HOE (B)
43 First diffraction mechanism 44 Thin plate-shaped light guide material 45 Reflective HOE (R)
46 Reflective HOE (G)
47 Reflective HOE (B)
48 Second diffraction mechanism 49 Wedge-shaped light guide material 50 Reflective HOE (R)
51 Reflective HOE (G)
52 Reflective HOE (B)
53 Third diffraction mechanism 54 Rod-shaped light guide 55 Reflective HOE
56 Fourth diffraction mechanism 57 Emitter 58 Collimator lens 59 Movable mirror 60 Relay lens 61 Imaging lens 62 Imaging optical system 63 Retina (fundus)
64 control unit 65 observation eye 66 pupil 67 crystal 68 movable mirror 69 collimating lens 70 imaging optical system 71 imaging lens 72 laser device 73 beam splitter 74 first mirror 75 object beam side beam expander 76 second mirror 77 reference beam side Beam expander 78 Wedge-shaped light guide material 79 Holographic photosensitive material 100 Point light source optical system 120 Point light source optical system 200 Point light source optical system 300 Retina scanning display 400 Retina scanning display

Claims (12)

A light source;
A collimating lens that converts light emitted from the light source into a substantially parallel luminous flux;
A first diffraction mechanism for diffracting the light beam transmitted through the collimating lens;
A second diffraction mechanism for diffracting the light beam that has passed through the first diffraction mechanism;
A third diffraction mechanism for diffracting the light beam that has passed through the second diffraction mechanism;
A fourth diffraction mechanism for diffracting the light beam that has passed through the third diffraction mechanism,
The first to fourth diffraction mechanisms include a diffractive optical element that diffracts the incident light beam in a predetermined direction, and a light guide unit that guides the light beam diffracted by the diffractive optical element in a predetermined direction. A point light source optical system comprising:   The point light source optical system according to claim 1, wherein at least one of the light guide portions has a wedge shape.   The point light source optical system according to claim 1, wherein the diffractive optical element reflects and diffracts the light beam.   The point light source optical system according to claim 1, wherein the diffractive optical element transmits and diffracts the light flux.   5. The point light source optical system according to claim 1, wherein the refractive index of the light guide section is substantially the same in any of the diffraction mechanisms. The diffractive optical element and the light guide are bonded by an adhesive material,
6. The point light source optical system according to claim 1, wherein a refractive index of the adhesive is larger than each refractive index of the diffractive optical element and the light guide unit. A plurality of the light sources;
The plurality of light sources each emit light having different wavelengths,
The point light source optical system according to any one of claims 1 to 6, wherein the diffractive optical element having a predetermined diffraction angle is arranged for each light having a different wavelength. . The optical paths in the light guide material of the light having different wavelengths are respectively different in position,
The point light source optical system according to claim 7, wherein the light guide unit has a boundary surface that separates the optical paths of the light having different wavelengths.   The point light source optical system according to claim 1, wherein the diffractive optical element includes a diffraction grating that diffracts light having two or more different wavelengths.   The point light source optical system according to claim 7, wherein colors of light emitted from the light source are red, green, and blue.   An optical apparatus comprising the point light source optical system according to claim 1. The recording material of the diffractive optical element is fixed to a light guide unit that guides the diffracted light diffracted by the diffractive optical element in a predetermined direction when the diffractive optical element is used,
After separating one laser beam into two laser beams, one laser beam is irradiated onto the recording material in the same direction as the light is incident when the diffractive optical element diffracts the light, and at the same time A method of manufacturing a diffractive optical element, wherein a diffraction grating is formed by allowing the other laser beam to enter from a surface of the light guide portion from which the diffracted light is emitted.

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