JP2008275867A - Hologram optical element, its facturing method, and light source unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hologram optical element 22 capable of emitting bright light rays by deflecting the most of light rays emitted from a light source which are wide in radiation angle. <P>SOLUTION: A luminous flux which becomes divergence light when the light rays are made incident on a hologram photosensitive material 22a is used as at least one luminous flux out of two luminous fluxes for exposing the hologram photosensitive material 22a, and the two luminous fluxes are made incident on the hologram photosensitive material 22a coaxially or approximately coaxially. Thereby, when the hologram optical element 22 is used, the divergence light emitted from the light source can be diffracted and deflected in the hologram optical element 22. Further, not only a deflection angle formed on one side of an extension line of light emitted from the hologram optical element 22 within a face vertical to the light incident side surface of the hologram optical element 22 but also a deflection angle on the other side can be also realized, and the most of light rays emitted from the light source which are wide in the radiation angle can be deflected by the hologram optical element 22. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a hologram optical element for producing a volume phase transmission hologram optical element by exposing a hologram photosensitive material with two light beams, the hologram optical element, and a light source unit using the hologram optical element It is about.

  Light emitting diodes (LEDs) have been used in various devices in recent years because they are compact, consume less power, and have a longer life than fluorescent tubes that have been widely used as light sources. Such an LED generally has a large radiation angle (for example, about ± 60 degrees at half intensity (full angle 120 degrees)), so that a light source unit with a small radiation angle can be realized by integrating the LED and the condenser lens depending on the application. Has been. However, if a condensing lens is used to reduce the radiation angle in this way, the thickness of the package (light source unit) is approximately twice that of the case where no condensing lens is used, and the thickness of the condensing lens The thickness of the package increases accordingly.

  Therefore, in Patent Document 1, for example, as shown in FIG. 17A, a film-like transmissive hologram optical element 104 is attached to the surface of the main body 102 including the LED 101 via the intermediate layer 103, and The divergent light is shaped into parallel light by the hologram optical element 104 and emitted. Since the hologram optical element 104 is in the form of a film, disposing this in front of the LED 101 makes it possible to reduce the thickness of the entire package and reduce the size of the apparatus.

JP 2002-292930 A

  As shown in FIG. 17B, the transmissive hologram optical element 104 irradiates the hologram photosensitive material 104a on the substrate with reference light L1 and object light L2 from the same side, and refracts interference fringes. It is produced by recording as rate modulation. At this time, since the reference light L1 and the object light L2 are incident on the hologram photosensitive material 104a at different angles, when the produced hologram optical element 104 is used, from the hologram optical element 104, as shown in FIG. Light is emitted at an angle and obliquely.

  Here, as shown in FIG. 18, among the angles formed by the light beam (solid line) incident on the hologram optical element 104 during use and the extension line (broken line) of the light beam (solid line) emitted from the hologram optical element 104, The acute angle θ is called the deflection angle. Further, in order to facilitate understanding of the explanation, the hologram optical element 104 described above has parallel light as light emitted from the hologram optical element 104 when used, and light that is in the same direction as the emitted light when exposed (for example, object light L2). It is assumed that the substrate is arranged so that the incident angle with respect to the hologram photosensitive material 104a is 0 °. Therefore, in this case, the deflection angle θ when the hologram optical element 104 is used is equal to the incident angle of the reference light L1 used during exposure with respect to the hologram photosensitive material 104a. Note that the hologram optical element 104 indicated by a broken line indicates the position in the exposure state of FIG.

  FIG. 19 is a graph showing the result of simulating the relationship between the deflection angle and the diffraction efficiency when using the hologram optical element 104 of FIG. In this simulation, the manufacturing wavelength (the wavelengths of the reference light L1 and the object light L2) is λ0, the refractive index of the hologram photosensitive material 104a (for example, photopolymer) is n, the refractive index modulation amount is Δn, and the thickness of the hologram photosensitive material 104a. Λ0 = 532 nm, n = 1.5, where t is t, the incident angle of the reference light L1 to the hologram photosensitive material 104a is θ1, the incident angle of the object light L2 to the hologram photosensitive material 104a is θ2, and the reproduction wavelength is λ1. Δn = 0.008, t = 35 μm, θ1 = 0 to 85 °, θ2 = 0 °, and λ1 = 532 nm. In the simulation shown in FIG. 17A, the extension of the light beam emitted from the hologram optical element 104 in the plane perpendicular to the light incident surface 104b of the hologram optical element 104 is obtained as shown in FIG. On the other hand, based on the fact that the deflection angle θ can be formed only on one side, the range of the deflection angle θ (= θ1) is performed in the range of the same sign of 0 to 85 °.

  From this simulation result, the range of the deflection angle θ at which the diffraction efficiency is, for example, 70% or more is approximately 50 ° from 10 ° to 60 °. Therefore, assuming that the radiation angle of the LED 101 when the LED 101 is arranged and used at the condensing point P (see FIG. 18) of the reference light L1 at the time of exposure is θ3, θ3 <θ from the geometrical relationship in FIG. Therefore, in the configuration of FIG. 17A, the light emitted from the LED 101 is within a range where the emission angle is surely smaller than 50 ° as a whole (based on the optical axis of the light emitted from the LED 101, Only light within a certain range smaller than ± 25 ° is diffracted (deflected) with high diffraction efficiency. As a result, the configuration of FIG. 17A cannot realize a light source unit that emits bright light.

  The present invention has been made to solve the above-mentioned problems, and its purpose is to deflect most of light emitted from a light source (light having a wide radiation angle) and emit bright light. It is an object of the present invention to provide a light source unit, a hologram optical element used for the light source unit, and a method for manufacturing the hologram optical element.

  The hologram optical element manufacturing method of the present invention is a hologram optical element manufacturing method for producing a volume phase transmission hologram optical element by exposing a hologram photosensitive material with two light beams. As one of the light beams, a light beam that becomes divergent light when incident on the hologram photosensitive material is used, and two light beams are incident on the hologram photosensitive material coaxially or substantially coaxially.

  Here, when the produced transmissive hologram optical element is used, a light beam incident on the hologram optical element and a light beam emitted from the hologram optical element (when the light beam incident on the hologram optical element is diffracted, deflected and emitted) Of the angles formed with the extended lines of the outgoing light rays, acute angles are called deflection angles. That is, the deflection angle is an index indicating how much incident light is deflected and emitted by diffraction by the hologram optical element. As the axis of the two light beams, the optical axis of the optical system that generates the two light beams can be considered.

  According to the manufacturing method of the present invention, at least one of the two light beams for exposing the hologram photosensitive material is a light beam that becomes divergent light when incident on the hologram photosensitive material. Sometimes, a light source that emits light at a certain radiation angle such as a light emitting diode (hereinafter also referred to as an LED) is arranged at a position corresponding to the emission point of the divergent light, and the light emitted from the light source (divergent light) Can be deflected (diffracted) by the hologram optical element.

  In addition, two light beams are incident coaxially or substantially coaxially with respect to the hologram photosensitive material at the time of exposure. Therefore, when the produced hologram optical element is used, the hologram is within a plane perpendicular to the light incident side of the hologram optical element. Not only the deflection angle that can be formed on one side (plus side) with respect to the extended line of the light beam emitted from the optical element, but also the deflection angle on the other side (minus side) can be realized. Thereby, as a light source used at the time of use, a light source having a radiation angle expanded to the maximum value of the plus side and minus side deflection angles can be used. In other words, even when a light source having a wider radiation angle is used, most of the light emitted from the light source can be deflected by the hologram optical element and used. As a result, it is possible to realize a light source unit that emits bright light as compared with the conventional case where only one deflection angle is realized.

  In the method for manufacturing a hologram optical element of the present invention, it is desirable that the two light beams are incident on the hologram photosensitive material after the optical paths are combined by the optical path combining means.

  By doing so, two light beams traveling in different directions can be incident on the hologram photosensitive material coaxially or substantially coaxially by the optical path synthesis by the optical path synthesis means at the time of exposure. In addition, by using the optical path synthesis means, the manufacturing optical system can be configured simply, and the above-described effects of the present invention can be obtained with a simple configuration. As such an optical path combining means, for example, a polarization beam splitter or a pinhole mirror can be assumed.

  In the method of manufacturing a hologram optical element according to the present invention, a polarization beam splitter that transmits or reflects incident light according to a polarization state is used as the optical path synthesis unit, and the light is condensed in the optical path of the optical system that generates the divergent light. A lens, the polarization beam splitter, and a polarization state conversion unit are arranged. The polarization state conversion unit includes a first region that maintains the polarization state of incident light, and a second region that converts the polarization state of incident light. One of the first and second regions is located at the condensing position of the condenser lens, and the other is formed so as to surround one around the optical axis, Is incident on the hologram photosensitive material through a region located at a condensing position of the condensing lens among the first and second regions of the condensing lens, the polarizing beam splitter, and the polarization state converting means. The The other light beam, the polarizing beam splitter may be through both the first and second regions of the polarization change means so as to be incident on the hologram photosensitive material. Note that the first region of the polarization state converting means can be constituted by, for example, a hole (gap) or a transparent substrate (glass substrate or plastic substrate), and the second region is, for example, a half-wave plate. It is possible to configure.

  In the above manufacturing method, one light beam (for example, S-polarized light) is incident on the polarization beam splitter through the condenser lens, reflected there, and once condensed at the condensing position of the condenser lens in the polarization state converting means. From there, it becomes divergent light and enters the hologram photosensitive material. At this time, if the first region of the polarization state converting means is located at the condensing position of the condensing lens, the polarization state of the light incident on the first region is maintained as it is (the S polarization is maintained). Then, it enters the hologram photosensitive material. On the other hand, if the second region of the polarization state converting means is located at the condensing position of the condensing lens, the light incident on the second region is converted in the polarization state (converted to P-polarized light). Then, it enters the hologram photosensitive material.

  On the other hand, the other light beam (for example, P-polarized light) enters the polarization beam splitter, passes therethrough, and passes through both the first and second regions of the polarization state converting means to the hologram photosensitive material. Incident. At this time, the light that has entered the first region of the polarization state conversion means in the other light flux is emitted as P-polarized light, and the light that has entered the second region is converted into S-polarized light and emitted therefrom. The

  Therefore, when the first region of the polarization state converting means is located at the condensing position of the condenser lens (when the second region is formed so as to surround the first region around the optical axis), In the hologram photosensitive material, one light beam is incident as S-polarized light and the other light beam is incident as P-polarized light in the region corresponding to the first region, so that they do not interfere with each other and interference fringes are not formed. On the other hand, in the hologram photosensitive material, in the region corresponding to the second region (within the incident range of the other light beam), both the two light beams are incident as S-polarized light, so that they interfere with each other to form interference fringes. . That is, in the produced hologram optical element, a hologram non-configuration area is formed corresponding to the first area, and the hologram configuration area is formed so as to surround the hologram non-configuration area around the optical axis.

  When the second region of the polarization state conversion means is located at the condensing position of the condenser lens (when the first region is formed so as to surround the second region around the optical axis), In the hologram photosensitive material, one light beam is incident as P-polarized light and the other light beam is incident as S-polarized light in the region corresponding to the second region, so that they do not interfere with each other and interference fringes are not formed. On the other hand, in the hologram photosensitive material, in the region corresponding to the first region (within the incident range of the other light beam), both of the two light beams are incident as P-polarized light, so that they interfere with each other, and interference fringes are formed. . That is, in the manufactured hologram optical element, a hologram non-configuration area is formed corresponding to the second area, and a hologram configuration area is formed so as to surround the hologram non-configuration area.

  As described above, according to the manufacturing method of the present invention, in the hologram optical element, the hologram constituting area can be formed so as to surround the hologram non-constituting area. Therefore, for example, the produced hologram optical element is placed in front of a light source such as an LED. When arranged and used, the light incident on the hologram non-construction region is transmitted without being diffracted there, and the light incident on the hologram constitution region is diffracted and emitted there.

  As can be seen from the graph of FIG. 5, for example, in a transmissive hologram optical element having only a hologram structure region, the diffraction efficiency is extremely lowered in a region where the deflection angle in use is small, and the intensity of extracted light is remarkably high. descend.

  However, according to the present invention, not only the hologram constituent area but also the hologram non-constituting area is formed in the hologram optical element. For example, in the area where the deflection angle is considered to be small if the hologram is constituted, the hologram By setting it as a non-configuration region, a high amount of transmitted light can be obtained, and it is possible to avoid a significant decrease in the intensity of the extracted light. In particular, according to the present invention, since the hologram configuration area can be formed so as to surround the hologram non-configuration area, it is possible to avoid the central intensity of the light extracted from the hologram optical element from being significantly reduced.

  Further, by using a polarization beam splitter as the optical path combining means, it is possible to realize a manufacturing optical system that can easily combine the optical paths.

  In the method for manufacturing a hologram optical element according to the present invention, the first region of the polarization state converting means is located at the condensing position of the condenser lens, and the second region surrounds the first region around the optical axis. The second region may be composed of a half-wave plate, and the first region may be composed of holes formed in the half-wave plate.

  The second region is a half-wave plate, and the first region is a hole (gap) formed in the half-wave plate so that the first region is surrounded around the optical axis. The two regions can be easily formed. Therefore, when using the hologram optical element, it is possible to easily obtain an effect capable of avoiding a significant decrease in the center intensity of the extracted light.

  In the method for manufacturing a hologram optical element according to the present invention, the second region of the polarization state converting means is located at the condensing position of the condensing lens, and the first region surrounds the second region around the optical axis. The first region may be formed of a transparent substrate, and the second region may be formed of a half-wave plate.

  The first region is a transparent substrate (for example, a glass substrate or a plastic substrate), and the second region is a half-wave plate, so that the first region is surrounded around the optical axis. Can be formed. Therefore, when using the hologram optical element, it is possible to easily obtain an effect capable of avoiding a significant decrease in the center intensity of the extracted light.

  In the method for manufacturing a hologram optical element according to the present invention, a pinhole mirror in which a reflective film having a hole is formed on a transparent substrate is used as the optical path synthesizing means. The lens and the pinhole mirror are arranged, and the pinhole mirror is arranged so that the hole of the reflection film is located at the light collecting position of the light collecting lens. The light is incident on the hologram photosensitive material through the hole of the reflection film of the pinhole mirror, and the other light beam is incident on a region including the hole of the reflection film with a larger beam diameter than the hole of the reflection film with respect to the pinhole mirror. The light beam reflected by the reflection film may be incident on the hologram photosensitive material.

  In the above manufacturing method, one light beam (for example, P-polarized light) is incident on the pinhole mirror via the condenser lens, and is once condensed at the position of the hole of the reflection film, and becomes divergent light therefrom. Incident on the hologram photosensitive material. On the other hand, the other light beam (for example, P-polarized light) is incident on the region including the reflection film with a larger light beam diameter than the hole of the reflection film of the pinhole mirror, and only the light reflected by the reflection film. Is incident on the hologram photosensitive material (the light of the other light beam that has entered the hole of the reflecting film is transmitted therethrough and does not enter the hologram photosensitive material).

  Therefore, since only one light beam (only one light beam) is incident on the region of the hologram photosensitive material corresponding to the hole of the reflection film of the pinhole mirror, no interference fringes are formed. On the other hand, since the two light beams are incident in the same polarization state (P-polarized light) in the region corresponding to the formation region of the reflection film of the pinhole mirror (within the incident range of the other light beam) in the hologram photosensitive material, Interfere with each other to form interference fringes. That is, in the produced hologram optical element, a hologram non-configuration region is formed corresponding to the hole of the reflection film of the pinhole mirror, and the hologram configuration region is formed so as to surround the hologram non-configuration region around the optical axis. .

  As described above, according to the manufacturing method of the present invention, in the hologram optical element, the hologram constituting area can be formed so as to surround the hologram non-constituting area. Therefore, for example, the produced hologram optical element is placed in front of a light source such as an LED. When arranged and used, the light incident on the hologram non-construction region is transmitted without being diffracted there, and the light incident on the hologram constitution region is diffracted and emitted there.

  As can be seen from the graph of FIG. 5, for example, in a transmissive hologram optical element having only a hologram structure region, the diffraction efficiency is extremely lowered in a region where the deflection angle in use is small, and the intensity of extracted light is remarkably high. descend.

  However, according to the present invention, not only the hologram constituent area but also the hologram non-constituting area is formed in the hologram optical element. For example, in the area where the deflection angle is considered to be small if the hologram is constituted, the hologram By setting it as a non-configuration region, a high amount of transmitted light can be obtained, and it is possible to avoid a significant decrease in the intensity of the extracted light. In particular, according to the present invention, since the hologram configuration area can be formed so as to surround the hologram non-configuration area, it is possible to avoid the central intensity of the light extracted from the hologram optical element from being significantly reduced.

  Further, the pinhole mirror has a reflective film formed on a transparent substrate, and can be easily reduced in thickness. Therefore, by using a pinhole mirror as the optical path combining means, the degree of freedom increases in the arrangement angle of the pinhole mirror, and it is possible to arrange the condenser lens closer to the pinhole mirror side depending on the adjustment of the arrangement angle. Become. This makes it possible to increase the NA (numerical aperture) of the condenser lens, in other words, to shorten the focal length of the condenser lens. As a result, when the produced hologram optical element is used, light having a wider radiation angle can be deflected by the hologram optical element, and a light source unit that emits brighter light can be realized.

  In the method for manufacturing a hologram optical element according to the present invention, it is desirable that the optical axis of the optical system for generating two light beams incident on the hologram photosensitive material is coaxial with the optical system when the produced hologram optical element is used.

  In this case, for example, when the produced hologram optical element is used in front of a light source such as an LED, if the light source is arranged on the same axis as that at the time of exposure, the light emission characteristic is axially symmetric (rotationally symmetric). A light source unit can be realized.

  In the method for manufacturing a hologram optical element of the present invention, a light beam that becomes divergent light when incident on the hologram photosensitive material may be used as both of the two light beams used when exposing the hologram photosensitive material.

  In this case, when divergent light is incident on the hologram optical element at the time of use, the divergent light is emitted by diffraction and deflection at the hologram optical element. It is suitable for optical systems and light source units that require

  In the method for manufacturing a hologram optical element of the present invention, one of the two light beams used for exposure of the hologram photosensitive material is a light beam that becomes divergent light when incident on the hologram photosensitive material, and the other light beam is a hologram photosensitive material. A light beam that becomes convergent light when incident on the light beam may be used.

  In this case, when divergent light is incident on the hologram optical element at the time of use, the convergent light is emitted by diffraction and deflection at the hologram optical element. It is suitable for optical systems and light source units that require

  The hologram optical element of the present invention is a volume phase type transmission hologram optical element, which is manufactured by the manufacturing method of the present invention described above.

  Since the hologram optical element is manufactured by the manufacturing method of the present invention, for example, when a hologram optical element is arranged in front of a light source such as an LED to configure a light source unit, a light source having a wide radiation angle is used. However, most of the light emitted from the light source can be deflected by the hologram optical element. Thereby, the light source unit which radiate | emits bright light is realizable.

  The hologram optical element of the present invention is a volume phase type transmission hologram optical element, and has a hologram non-configuration area where a hologram is not formed and a hologram configuration area where a hologram is formed. The hologram non-configuration region is formed so as to surround it.

  According to the above configuration, the hologram constituent element is formed so as to surround the hologram non-constituting area to constitute the hologram optical element. Therefore, when the hologram photosensitive material is exposed with two light beams in order to produce the hologram optical element. In this case, a method is adopted in which two light beams are incident coaxially or substantially coaxially on the hologram photosensitive material while using a light beam that becomes divergent light when incident on the hologram photosensitive material as at least one of the two light beams. it can.

  Thereby, when using the hologram optical element, a light source that emits light at a certain radiation angle such as an LED is arranged at a position corresponding to the emission point of the divergent light, and the light emitted from the light source (divergent light) Can be deflected by a hologram optical element. Moreover, when the hologram optical element is used, a deflection angle that can be on one side (plus side) with respect to the extended line of the light beam emitted from the hologram optical element within a plane perpendicular to the light incident side surface of the hologram optical element. In addition, the deflection angle on the other side (minus side) can also be realized. Thereby, as a light source used at the time of use, a light source having a radiation angle expanded to the maximum value of the plus side and minus side deflection angles can be used. In other words, even when a light source having a wider radiation angle is used, most of the light emitted from the light source can be deflected by the hologram optical element and used. As a result, it is possible to realize a light source unit that emits bright light as compared with the conventional case where only one deflection angle is realized.

  In addition, as in the present invention, if the hologram optical element is configured to have a hologram constituent region and a hologram non-constituting region, the deflection angle is originally small if the hologram is configured, and the diffraction efficiency is extremely high. The holographic optical element of the present invention is formed by associating a region that decreases and a region that is originally formed around a region having a small deflection angle, a region having a large deflection angle, and a high diffraction efficiency, with the non-hologram configuration region and the hologram configuration region, respectively. Can be used.

  In this way, when the hologram optical element of the present invention is arranged in front of a light source such as an LED in association with each region, the light incident on the hologram non-configuration region is transmitted without being diffracted there, and the hologram configuration Light incident on the region is diffracted and emitted therefrom. Therefore, light having a high transmitted light amount can be obtained from the hologram non-construction region, and diffracted light can be obtained from the hologram constitution region with high diffraction efficiency. As a result, it is possible to avoid the central intensity of the light extracted from the hologram optical element from being significantly reduced.

  In the hologram optical element of the present invention, an acute angle out of the angles formed between the light beam incident on the hologram composition region and the extended line of the emitted light beam when the light beam is diffracted and deflected in the hologram composition region Is the deflection angle, it is desirable that the absolute value of the deflection angle in the hologram composition region is 5 ° or more.

  If the hologram photosensitive material that forms the volume phase type transmission hologram optical element is made of, for example, a photopolymer, the region where the absolute value of the deflection angle is 5 ° or more has high diffraction efficiency. Light with sufficient intensity can be obtained from the region.

  Note that the hologram non-configuration region surrounded by the hologram configuration region is a region in which the absolute value of the deflection angle is less than 5 ° when the hologram is originally configured, and is originally a region where the diffraction efficiency is extremely reduced. In the invention, since no hologram is formed in the region, light with sufficient intensity can be obtained with a high amount of transmitted light.

  In the hologram optical element of the present invention, it is desirable that the hologram photosensitive material that forms the hologram constituting region is made of a photopolymer.

  In this case, high diffraction efficiency can be reliably realized in the hologram composition region where the absolute value of the deflection angle is 5 ° or more, and light with sufficient intensity can be reliably obtained from the hologram composition region. In addition, if a photopolymer is used as the hologram photosensitive material, the hologram optical element can be manufactured by a dry process, which simplifies the manufacturing process.

  In the hologram optical element of the present invention, an acute angle out of the angles formed between the light beam incident on the hologram composition region and the extended line of the emitted light beam when the light beam is diffracted and deflected in the hologram composition region Is the deflection angle, the absolute value of the deflection angle in the hologram composition area may be an angle at which the diffraction efficiency of the primary light in the hologram composition area is 50% or more of the maximum diffraction efficiency.

  In this case, since the diffraction efficiency of 50% or more of the maximum diffraction efficiency of the primary light is ensured in the hologram constituent area, light with sufficient intensity can be obtained from the hologram constituent area. The hologram photosensitive material that forms the volume phase transmission hologram optical element may be, for example, a photopolymer or a silver salt material, or may be other materials.

  The hologram optical element of the present invention may be rotationally symmetric. The hologram optical element of the present invention can be easily applied to a general coaxial optical system because the hologram optical element is rotationally symmetric, that is, the hologram non-configuration region and the hologram configuration region are both rotationally symmetric. It becomes.

  In the hologram optical element of the present invention, the hologram optical element is produced by exposing a hologram photosensitive material formed on a transparent substrate with two light beams, and the transparent substrate has a lens portion on a part of the substrate. The lens portion may be configured to be positioned corresponding to the hologram non-formation region.

  For example, when the hologram optical element of the present invention is used in front of a light source such as an LED so that the lens substrate side is the light source side, the light emitted from the light source is refracted by the lens portion of the lens substrate. Then, it enters the hologram non-construction region and passes therethrough. On the other hand, in the hologram configuration area, incident light is diffracted and deflected as described above. Therefore, a thin optical element having optical power can be easily realized as the entire hologram optical element.

  The light source unit of the present invention includes a light source and a volume phase type transmission hologram optical element disposed in front of the light source, and the hologram optical element is composed of the hologram optical element of the present invention described above. It is characterized by.

  In this configuration, for example, even when a light source having a wide radiation angle is used, most of the light emitted from the light source is deflected and emitted by the hologram optical element of the present invention. Therefore, it is possible to realize a light source unit that emits bright light by effectively using light emitted from the light source.

  In the light source unit of the present invention, the wavelength of the two light beams used for exposure of the hologram photosensitive material that is the basis for producing the hologram optical element is within ± 20 nm of the peak wavelength of the light emitted from the light source in use. Is desirable.

  In this case, since the exposure wavelength and the use wavelength (peak wavelength) are substantially equal, the light emitted from the light source can be efficiently diffracted and deflected in the hologram constituent region of the hologram optical element, and the light use efficiency is high. A light source unit can be realized.

  According to the present invention, when the hologram optical element is used, the deflection angles are formed on both sides with respect to the extended line of the light beam emitted from the hologram optical element in a plane perpendicular to the light incident side surface of the hologram optical element. can do. Thereby, even when a light source with a wide radiation angle is used, the light emitted from the light source can be used by being deflected by the hologram optical element. As a result, a light source unit that emits brighter light than before can be realized.

[Embodiment 1]
An embodiment of the present invention will be described below with reference to the drawings.

(1. About the light source unit)
FIG. 2 is a cross-sectional view illustrating a schematic configuration of the light source unit according to the present embodiment. This light source unit has a light source module 1 and a hologram substrate 2, and has a configuration in which light emitted from the light source module 1 is extracted to the outside through the hologram substrate 2.

  The light source module 1 has a light source 12 in a housing 11. The light source 12 is composed of, for example, an LED (light emitting diode) that emits light having a peak wavelength (center wavelength) of 520 nm. The light source 12 has a wide radiation angle characteristic in which the radiation angle is ± 60 degrees (full angle 120 degrees) even at half intensity, and is mounted on the electrode 14 formed of a metal pattern formed on the substrate 13. Further, another electrode 15 made of a metal pattern is formed on the substrate 13, and the light source 12 and the electrode 15 are connected by an Au wire 16. The interior of the housing 11 is resin molded.

  The hologram substrate 2 includes a hologram optical element 22 on a transparent substrate 21 made of, for example, glass or plastic material. The hologram substrate 2 is bonded to the surface of the light source module 1 via an adhesive layer (not shown) so that the hologram optical element 22 is on the light source 12 side with respect to the substrate 21. As a result, the hologram optical element 22 is disposed in front of the light source 12. The hologram optical element 22 is composed of a volume phase type transmission hologram optical element.

  Therefore, the light (diverging light) emitted from the light source 12 is diffracted and deflected by the hologram optical element 22, and then passes through the substrate 21 and is emitted to the outside. As a result, a light source unit having a small orientation angle and good alignment characteristics (deflection characteristics) can be realized. Further, since the hologram optical element 22 is thin and inexpensive, the light source unit can be realized in a small size and at low cost by using such a hologram optical element 22.

(2. About hologram optical element)
Next, a detailed configuration of the above-described hologram optical element 22 will be described. FIG. 3 is a cross-sectional view showing a detailed configuration of the hologram optical element 22. The hologram optical element 22 has a hologram non-configuration area 31 and a hologram configuration area 32.

  The hologram non-configuration region 31 is a region where a hologram that diffracts and deflects incident light is not configured. Therefore, the hologram non-configuration region 31 functions as a transmission region that simply transmits light when the light is incident thereon. On the other hand, the hologram configuration region 32 is a region where a hologram for diffracting and deflecting incident light is configured. More specifically, divergent light from a point P corresponding to a light emitting point when the light source 12 is considered as a point light source is diffracted and deflected and emitted as a light beam parallel to the optical axis in the hologram composition region 32. A hologram is formed. Note that the optical axis when the hologram optical element 22 is used refers to an axis A that passes through the point P and is perpendicular to the light incident surface 22 b of the hologram optical element 22.

  Here, the hologram is formed by exposing a film-like hologram photosensitive material 22a (see FIG. 1) held on the substrate 21 (see FIG. 2) with two coherent light beams. is there. That is, the hologram is composed of interference fringes formed by two-beam interference. Therefore, it can be said that the hologram non-configuration region 31 is a region that does not have the interference fringes, and the hologram configuration region 32 is a region that has the interference fringes.

  Photopolymer, silver salt material, dichromated gelatin or the like can be used as the hologram photosensitive material 22a from which the hologram optical element 22 is produced. Here, the hologram optical element 22 can be easily processed by a dry process. Photopolymer (manufactured by DuPont, for example) can be used.

  In the present embodiment, the hologram non-configuration area 31 is located on the optical axis, and the hologram configuration area 32 is formed so as to surround the hologram non-configuration area 31 around the optical axis. Furthermore, both the hologram non-configuration region 31 and the hologram configuration region 32 are formed rotationally symmetric (axially symmetric) with respect to the optical axis. As a result, the hologram optical element 22 is configured to be rotationally symmetric as a whole. It will be. Thus, since the hologram optical element 22 is configured to be rotationally symmetric, the hologram optical element 22 can be easily applied to a general coaxial optical system. That is, the hologram optical element 22 can be arranged and used at a position coaxial with the optical system in use.

  As described above, the hologram optical element 22 has the hologram non-configuration region 31 and the hologram configuration region 32, and the hologram configuration region 32 is formed so as to surround the hologram non-configuration region 31 around the optical axis. As a result, the manufacturing method described later can be adopted when the hologram optical element 22 is manufactured. That is, a method in which two light beams are coaxially incident on the hologram photosensitive material 22a while using a light beam that becomes divergent light when entering the hologram photosensitive material 22a as at least one of the two light beams that expose the hologram photosensitive material 22a. Can be adopted. This is because, in the method in which two light beams are coaxially incident on the hologram photosensitive material 22a, a hologram can be formed only around the axis A without forming a hologram in the vicinity of the axis A as described later.

  For convenience of explanation below, a light beam incident on the hologram composition region 32 when the hologram optical element 22 is used, and an extension line of the light beam emitted when the light beam is diffracted and deflected by the hologram composition region 32 and emitted. Of these angles, the acute angle θ is called the deflection angle.

(3. Method for manufacturing hologram optical element)
Next, a method for manufacturing the hologram optical element 22 having the above-described configuration will be described. FIG. 1 is a cross-sectional view showing a schematic configuration of a main part of a manufacturing optical system used when manufacturing the hologram optical element 22.

  In the present embodiment, the hologram photosensitive material 22a is exposed to diffract and deflect the light (diverged light) from the light source 12 in the hologram construction region 32 so as to be emitted as a light beam parallel to the optical axis. As one of the light beams (for example, the reference light L1), a light beam that becomes divergent light when incident on the hologram photosensitive material 22a is used. Therefore, a condensing lens 41, a polarization beam splitter (hereinafter also referred to as PBS) 42, and a polarization state conversion member 43 (polarization state conversion means) are arranged in the optical path of the optical system that generates the divergent light. ing.

  The condensing lens 41 condenses incident light (for example, parallel light) and has a predetermined NA. Therefore, the focal length of the condenser lens 41 is set to a predetermined value. The PBS 42 is an optical path synthesizing unit that synthesizes optical paths of two light beams incident from different directions by transmitting or reflecting incident light according to the polarization state. For example, the PBS 42 transmits P-polarized light and reflects S-polarized light. Have. By using such a PBS 42, two light beams incident from different directions can be coaxially incident on the hologram photosensitive material 22a via the PBS 42.

  At this time, if the common part of the optical axes of the optical system that generates two light beams incident on the hologram photosensitive material 22a during exposure is the axis B, the axis B in the manufacturing optical system is the axis of the hologram optical element 22 that is manufactured. It is also coaxial with the axis A (see FIG. 3) of the optical system in use.

  The polarization state conversion member 43 includes a first region 43a that maintains the polarization state of incident light and a second region 43b that converts the polarization state of incident light. The second region 43b is constituted by, for example, a half-wave plate, and the first region 43a is constituted by a hole formed in the half-wave plate. The first region 43a is located at the condensing position of the condensing lens 41, and the second region 43b is formed so as to surround the first region 43a around the optical axis (axis B).

  Here, when parallel light is used as the object light L2, the size of the first region 43a of the polarization state conversion member 43 is determined by the focal length of the hologram optical element 22 to be manufactured and the minimum deflection angle due to diffraction in the hologram constituent region 32. It is determined based on θmin. More specifically, it is as follows.

FIG. 4 is an explanatory diagram showing an enlarged optical path of light incident on the hologram photosensitive material 22a from the polarization state conversion member 43. As shown in FIG. The distance (radius) from the axis B that defines the size of the first region 43a of the polarization state conversion member 43 is h (mm), the focal length of the hologram optical element 22, that is, the condensing position of the condensing lens 41. The distance from the light converging position to the light incident surface 22b of the hologram photosensitive material 22a is fl (mm), and the light beam incident on the portion corresponding to the boundary between the hologram constituting region 32 and the hologram non-constituting region 31 in the hologram photosensitive material 22a. If the angle formed with the axis B is φ (°), the distance h is expressed as follows.
h = fltanφ
At this time, from FIG. 4, since φ = θmin,
h = fltan θmin
It becomes. Therefore, it can be seen that the size of the first region 43a is determined based on these parameters. When the object light L2 is parallel light, not only the first region 43a but also the size of the hologram non-configuration region 31 is defined by the distance h.

  In the manufacturing optical system, in addition to the condenser lens 41, the PBS 42, and the polarization state converting member 43, a laser light source, a beam splitter, a beam expander, and the like are also arranged. Accordingly, the coherent light beam emitted from the laser light source is branched into two light beams by the beam splitter, and is expanded to a predetermined light beam diameter by the beam expander. The exposure time with the laser light is controlled by a shutter (not shown).

  The reference light L1 (here, S-polarized light) which is one of the two light beams is condensed by the condenser lens 41 from the parallel light state to be converged light, reflected by the PBS 42, and then converted into the polarization state. It enters the hologram photosensitive material 22a through the first region 43a of the member 43 as S-polarized light. Here, since the first region 43a is arranged at the condensing position of the condensing lens 41, the reference light L1 becomes divergent light simultaneously with the passage of the first region 43a and enters the hologram photosensitive material 22a. To do.

  On the other hand, the object light L2 (here, P-polarized light) which is the other of the two light beams passes through the PBS 42 in the state of parallel light, and is coaxial with the reference light L1 and the first region of the polarization state conversion member 43. It enters both 43a and the second region 43b, and enters the hologram photosensitive material 22a through these regions. At this time, the object light L2 incident on the first region 43a of the polarization state conversion member 43 is emitted while the polarization state is maintained there, so that it enters the hologram photosensitive material 22a as P-polarized light. On the other hand, since the object light L2 incident on the second region 43b is emitted after the polarization state is converted there, it enters the hologram photosensitive material 22a in the S-polarized state.

  That is, in the hologram photosensitive material 22a, the reference light L1 is incident on the region corresponding to the first region 43a in the S-polarized state, and the object light L2 is incident on the P-polarized state. Since these lights have different polarization directions and do not interfere with each other, no interference fringes are formed in the region. Therefore, the region is a hologram non-configuration region 31. That is, when post-exposure post-processing (for example, bake processing) is performed, the area functions as a mere transmission area.

  On the other hand, in the hologram photosensitive material 22a, the reference light L1 is incident in the S-polarized state and the object light L2 is also incident in the S-polarized state in the region corresponding to the second region 43b within the incident range of the object light L2. To do. Since these lights have the same polarization direction and interfere with each other, interference fringes are formed in the region. Therefore, the area becomes the hologram construction area 32. That is, the hologram configuration region 32 is formed so as to surround the hologram non-configuration region 31 formed near the optical axis around the optical axis.

  As a result, when the light source 12 is disposed at a position corresponding to the condensing point of the condensing lens 41 and the produced hologram optical element 22 is disposed in front of the light source 12, as shown in FIG. A hologram that transmits part of the divergent light emitted from P) (light incident on the hologram non-construction region 31) and converts the remaining light (light incident on the hologram non-construction region 32) into parallel light and emits it. The optical element 22 is obtained.

(4. Effect)
As described above, in the present embodiment, one of the two light beams that expose the hologram photosensitive material 22a (the reference light L1 in the above example) is a light beam that becomes divergent light when incident on the hologram photosensitive material 22a. Therefore, when the produced hologram optical element 22 is used, the light source 12 is disposed at a position corresponding to the emission point of the diverging light, and a part of the light (diverging light) emitted from the light source 12 is transferred to the hologram optical element. 22 can be deflected and diffracted.

  FIG. 5 is a graph showing the result of simulating the relationship between the deflection angle and the diffraction efficiency (transmitted zero order light, transmitted first order light) when the hologram optical element 22 is used. In the figure, the deflection angle that can be formed on one side with respect to the extension line of the light beam emitted from the hologram optical element 22 within a plane perpendicular to the light incident surface 22b of the hologram optical element 22 is a positive deflection angle. The deflection angle formed on the other side is expressed by a negative deflection angle. That is, in the cross section of FIG. 3, the deflection angle that is generated when a light ray emitted from the point P and rightward from the axis A is incident on the hologram optical element 22 (hologram construction region 32) is positively deflected. Assuming that the angle is a light beam emitted from the point P and the light beam on the left side of the axis A is incident on the hologram optical element 22 (hologram construction region 32), the deflection angle is a negative deflection angle.

  In the above simulation, the manufacturing wavelength (the wavelengths of the reference light L1 and the object light L2) is λ0, the refractive index of the hologram photosensitive material 22a (photopolymer) is n, the refractive index modulation amount is Δn, and the thickness of the hologram photosensitive material 22a. Λ0 = 532 nm, n = 1.5, Δn where t is t, the incident angle of the reference light L1 to the hologram photosensitive material 22a is θ1, the incident angle of the object light L2 to the hologram photosensitive material is θ2, and the reproduction wavelength is λ1. = 0.008, t = 35 μm, θ1 = −85 ° to 85 °, θ2 = 0 °, and λ1 = 532 nm. Here, the simulation is performed on the assumption that the hologram is also formed in the region near the deflection angle of 0 ° corresponding to the hologram non-configuration region 31, but the hologram non-configuration region 31 is actually formed. So (since no hologram is formed), no diffraction occurs in this region.

  From the simulation results of FIG. 5, the range of the deflection angle at which the diffraction efficiency is, for example, 70% or more is approximately 120 ° from −60 ° to 60 °, which is more than twice the conventional one. As described above, the range of the deflection angle can be ensured to be twice or more that of the prior art by causing the reference light L1 and the object light L2 to enter the hologram photosensitive material 22a coaxially during the exposure of the hologram photosensitive material 22a. This is because the hologram optical element 22 is manufactured.

  In other words, in the present embodiment, two light beams are incident on the hologram photosensitive material 22a coaxially during the exposure of the hologram photosensitive material 22a. Therefore, when the produced hologram optical element 22 is used, the light of the hologram optical element 22 is used. In the plane perpendicular to the incident surface 22b, not only the deflection angle that can be set on the plus side but also the deflection angle on the minus side can be realized. Thereby, as the light source 12 used at the time of use, the light source 12 having a radiation angle expanded to an angle corresponding to the deflection angle having the maximum absolute value at the plus side and minus side deflection angles can be used. In other words, even when the light source 12 having a wider radiation angle is used, most of the light emitted from the light source 12 (from the deflection angle having the maximum absolute value at the plus side deflection angle to the minus side deflection angle). The light in the radiation range corresponding to the angle between the deflection angles having the maximum absolute value) can be used by being deflected by the hologram optical element 22. As a result, it is possible to realize a light source unit that emits bright light as compared with the conventional case where only one deflection angle is realized.

  Further, since the two light beams used at the time of exposure are combined by the PBS 42 and then incident on the hologram photosensitive material 22a, the two light beams traveling in different directions can be incident on the hologram photosensitive material 22a coaxially. Further, by using the PBS 42, the manufacturing optical system has a simple configuration, and the above-described effects of the present invention can be obtained with such a simple configuration, and the hologram optical element 22 can be manufactured easily and inexpensively. it can.

  In the present embodiment, at the time of exposure of the hologram photosensitive material 22 a, one light beam (reference light L 1) is transmitted through the condenser lens 41, the PBS 42, and the first region 43 a of the polarization state conversion member 43 to the hologram photosensitive material 22 a. The other light beam (object light L2) is incident on the hologram photosensitive material 22a through both the PBS 42 and the first region 43a and the second region 43b of the polarization state conversion member 43. Thereby, as described above, in the produced hologram optical element 22, the hologram constituting region 32 can be formed so as to surround the hologram non-constituting region 31 around the optical axis.

  Therefore, when the produced hologram optical element 22 is arranged and used in front of the light source 12, the light incident on the hologram non-configuration region 31 is transmitted without being diffracted there, and is incident on the hologram configuration region 32. Is then diffracted and emitted. Therefore, light having a high transmitted light amount can be obtained in the hologram non-construction region 31, and light can be diffracted with high diffraction efficiency and extracted to the outside in the hologram composition region 32. As a result, it is possible to avoid extreme unevenness in the intensity distribution of the light obtained through the hologram optical element 22.

  In particular, as shown in FIG. 5, if a hologram is formed in a region near a deflection angle of 0 ° in the hologram optical element 22, this is a region where the diffraction efficiency is extremely lowered. Since this area is the hologram non-configuration area 31, it is possible to avoid a significant decrease in the intensity of the light extracted while securing a high amount of transmitted light. That is, it is possible to avoid the central intensity of the light extracted from the hologram optical element 22 from being significantly reduced.

  Further, as shown in FIG. 5, when the hologram photosensitive material 22a that forms the hologram optical element 22 is made of a photopolymer as in this embodiment, the absolute value of the deflection angle is 5 ° or more. This region has a high diffraction efficiency. Therefore, if the absolute value of the deflection angle in the hologram composition area 32 is 5 ° or more, that is, if the hologram composition area 32 is formed so that the absolute value of the deflection angle is 5 ° or more, the hologram composition area 32 is sufficient. It is possible to realize the hologram optical element 22 that can obtain light with a high intensity. On the contrary, since the region where the absolute value of the deflection angle is less than 5 ° is a region where the diffraction efficiency is extremely lowered, the region can be obtained by associating this region with the hologram non-configuration region 31 as in the present embodiment. Therefore, sufficient intensity of light can be obtained with a high amount of transmitted light.

  The absolute value of the deflection angle for distinguishing between the hologram non-configuration area 31 and the hologram configuration area 32 is not limited to the above 5 °, and may be, for example, 7 ° or 10 °. . In short, the absolute value of the deflection angle may be a value that can avoid the occurrence of extreme unevenness in the intensity distribution of the light obtained through the hologram optical element 22.

  Further, for example, if the hologram configuration region 32 is formed so that the deflection angle at which the diffraction efficiency of the primary light is 50% or more of the maximum diffraction efficiency is realized on both the plus side and the minus side, It seems that light with sufficient intensity can be obtained through the hologram forming region 32. This is the same even when the hologram photosensitive material 22a is made of a material other than the photopolymer.

  For example, FIG. 6 is a graph showing the result of simulating the relationship between the deflection angle and the diffraction efficiency when using the hologram optical element 22 obtained by exposing a hologram photosensitive material 22a made of a silver salt material. In the above simulation, λ0 = 532 nm, n = 1.5, Δn = 0.06, t = 5 μm, θ1 = −85 ° to 85 °, θ2 = 0 °, and λ1 = 532 nm.

  When such a hologram optical element 22 is configured, the deflection angle at which the diffraction efficiency of the primary light is 50% or more of the maximum diffraction efficiency is higher than that when a photopolymer is used as the hologram photosensitive material 22a. Although the absolute value is larger on the minus side, the hologram composition region 32 still has a diffraction efficiency of 50% or more of the maximum diffraction efficiency of the primary light. Therefore, the absolute value of the deflection angle in the hologram constituting region 32 is an angle at which the diffraction efficiency of the primary light in the hologram constituting region 32 is 50% or more of the maximum diffraction efficiency, regardless of the material of the hologram photosensitive material 22a. It can be said that light with sufficient intensity can be obtained from the hologram constituting region 32.

  In this embodiment, in the manufacturing optical system, the first region 43a of the polarization state conversion member 43 is located at the condensing position of the condensing lens 41, and the second region 43b has the first region 43a as the optical axis. It is formed so as to surround it. Such a polarization state conversion member 43 is easily realized by configuring the second region 43b with a half-wave plate and configuring the first region 43a with a hole formed in the half-wave plate. be able to. According to such a configuration of the polarization state conversion member 43, the second region 43 b can be easily formed so as to surround the first region 43 a around the optical axis, and thus the produced hologram optical element 22. In FIG. 5, the hologram composition region 32 can be easily formed so as to surround the hologram non-construction region 31 around the optical axis. As a result, when the hologram optical element 22 is used, it is possible to easily obtain the above-described effect capable of avoiding that the center intensity of the extracted light is significantly reduced.

  Further, since the axis B in the production optical system is coaxial with the axis A of the optical system when the produced hologram optical element 22 is used, the light source 12 is arranged on the axis A when the produced hologram optical element 22 is used. Then, it is possible to realize a light source unit whose light emission characteristics are axially symmetric (rotationally symmetric).

  In the present embodiment, the wavelength (manufacturing wavelength) of the two light beams used for exposure of the hologram photosensitive material 22a is, for example, 532 nm, which is close to the used wavelength, that is, 520 nm, which is the wavelength of light emitted from the light source 12. By making the manufacturing wavelength and the use wavelength close to each other in this way, the light emitted from the light source 12 at the time of use can be efficiently diffracted and deflected by the hologram optical element 22 (particularly, the hologram construction region 32). A highly efficient light source unit can be realized. The above-described effect can be obtained if the exposure wavelength is within ± 20 nm of the peak wavelength of the light emitted from the light source 12 in use.

(5. Modification 1 of manufacturing optical system)
Next, modified examples of the manufacturing optical system used for manufacturing the hologram optical element 22 of the present embodiment will be described below.

  FIG. 7 is a cross-sectional view showing another configuration of the main part of the manufacturing optical system used when manufacturing the hologram optical element 22 of the present embodiment. This manufacturing optical system has the same configuration as the manufacturing optical system of FIG. 1 except that a polarization state conversion member 44 (polarization state conversion means) is used instead of the polarization state conversion member 43.

  The polarization state conversion member 44 has a first region 44a that maintains the polarization state of incident light, and a second region 44b that converts the polarization state of incident light. The first region 44a is made of a transparent substrate (for example, a glass substrate or a plastic substrate), and the second region 44b is made of a half-wave plate. Note that the size of the second region 44b is determined based on the focal length of the hologram optical element 22 to be manufactured and the minimum deflection angle θmin due to diffraction in the hologram constituent region 32 based on the same consideration as in FIG. become. The second region 44b is located at the condensing position of the condensing lens 41, and the first region 44a is formed so as to surround the second region 44b around the optical axis.

  In the manufacturing optical system of FIG. 7, the reference light L1 (here, S-polarized light), which is one of the two light beams, is condensed by the condenser lens 41 from the parallel light state to become convergent light, and the PBS 42 After being reflected, it is incident on the second region 44b of the polarization state converting member 44, where it is converted to P-polarized light and incident on the hologram photosensitive material 22a. Here, since the second region 44b is arranged at the condensing position of the condensing lens 41, the reference light L1 becomes divergent light simultaneously with the passage of the second region 44b and enters the hologram photosensitive material 22a. To do.

  On the other hand, the object light L2 (here, P-polarized light) which is the other of the two light beams passes through the PBS 42 in the state of parallel light, and is coaxial with the reference light L1 and is the first region of the polarization state conversion member 44. 44a and the second region 44b are incident on the hologram photosensitive material 22a via these regions. At this time, the object light L2 incident on the first region 44a of the polarization state conversion member 44 is emitted while maintaining the polarization state there, so that it enters the hologram photosensitive material 22a as P-polarized light. On the other hand, since the object light L2 incident on the second region 44b is emitted after its polarization state is converted, it enters the hologram photosensitive material 22a in the S-polarized state.

  That is, in the hologram photosensitive material 22a, the reference light L1 is incident in the P-polarized state and the object light L2 is incident in the S-polarized state in the region corresponding to the second region 44b. Since these lights have different polarization directions and do not interfere with each other, no interference fringes are formed in the region. Therefore, the area becomes a hologram non-construction area 31 and functions as a simple transmission area.

  On the other hand, in the hologram photosensitive material 22a, the reference light L1 is incident in the P-polarized state and the object light L2 is incident in the P-polarized state in the region corresponding to the first region 44a in the incident range of the object light L2. To do. Since these lights have the same polarization direction and interfere with each other, interference fringes are formed in the region. Therefore, the area becomes the hologram construction area 32.

  As described above, even when the exposure is performed using the polarization state conversion member 44 instead of the polarization state conversion member 43, the hologram configuration region 32 transmits the hologram non-configuration region 31 formed near the optical axis. It is formed so as to surround the axis. Therefore, even if the manufacturing optical system of FIG. 7 is used, the same hologram optical element 22 as that of FIG. 3 can be obtained, and the above-described effects of the present invention can be obtained.

  In particular, by using the first region 44a as a transparent substrate and the second region 44b as a half-wave plate, the first region 44a can be easily surrounded so as to surround the second region 44b around the optical axis. Can be formed. Therefore, in the produced hologram optical element 22, the hologram constituting area 32 can be easily formed so as to surround the hologram non-constituting area 31 around the optical axis, and the center of the light to be extracted when the hologram optical element 22 is used. It is possible to easily obtain the effect of the present invention capable of avoiding a significant decrease in strength.

(6. Modification 2 of manufacturing optical system)
FIG. 8 is a cross-sectional view showing still another configuration of the main part of the manufacturing optical system used when manufacturing the hologram optical element 22 of the present embodiment. In this manufacturing optical system, a pinhole mirror 45 is used instead of the PBS 42 and the polarization state conversion member 43, and the position of the condenser lens 41 and the incident directions of the reference light L1 and the object light L2 with respect to the pinhole mirror 45 are appropriately set accordingly. Except for the set points, the configuration is the same as the manufacturing optical system of FIG.

  The pinhole mirror 45 is an optical path synthesizing unit that synthesizes and emits optical paths of two light beams incident from different directions. The pinhole mirror 45 is constituted by a flat mirror in which a reflective film 51 having a hole 51 a is formed on a transparent substrate 52. In the manufacturing optical system of FIG. 8, a condensing lens 41 and a pinhole mirror 45 are arranged in the optical path of the optical system that generates diverging light (for example, reference light L1). In addition, the pinhole mirror 45 is arranged so that the hole 51 a of the reflective film 51 is positioned at the condensing position of the condensing lens 41.

  In this state, one light beam (for example, P-polarized reference light L1) is incident on the hologram photosensitive material 22a through the condensing lens 41 and the hole 51a of the reflection film 51 of the pinhole mirror 45, and the other light beam (for example, The P-polarized object light L2) is incident on the pinhole mirror 45 in a region including the hole 51a of the reflective film 51 with a larger beam diameter than the hole 51a of the reflective film 51.

  At this time, since the hole 51a of the pinhole mirror 45 is located at the condensing position of the condensing lens 41, the reference light L1 is once condensed at the position of the hole 51a, and then becomes divergent light from the hologram photosensitive material. The light is incident on 22a as P-polarized light. Of the object light L2, the light reflected by the reflective film 51 (portion other than the hole 51a) is incident on the hologram photosensitive material 22a in the P-polarized state coaxially with the reference light L1. The light that has entered the hole 51a passes therethrough and does not enter the hologram photosensitive material 22a.

  Accordingly, in the hologram photosensitive material 22a, only one light beam (only the reference light L1) is incident on the region corresponding to the hole 51a of the reflection film 51 of the pinhole mirror 45, so that no interference fringes are formed. On the other hand, in the hologram photosensitive material 22a, in the region corresponding to the formation region (excluding the hole 51a) of the reflection film 51 of the pinhole mirror 45 within the incident range of the object light L2, both light beams have the same polarization state (above In this example, the incident light is P-polarized light, so that the two light beams interfere with each other to form interference fringes. That is, in the produced hologram optical element 22, the hologram non-configuration region 31 is formed corresponding to the hole 51 a of the reflection film 51 of the pinhole mirror 45, and the hologram is formed so as to surround the hologram non-configuration region 31 around the optical axis. A configuration region 32 is formed.

  In this way, even when the hologram optical element 22 is manufactured using the manufacturing optical system of FIG. 8, two light beams are incident on the hologram photosensitive material 22a coaxially while using divergent light as one of the two light beams at the time of exposure. In addition, the hologram composition region 32 can be formed so as to surround the hologram non-configuration region 31 around the optical axis. Therefore, even when the hologram optical element 22 is manufactured using the manufacturing optical system of FIG. 8, a bright light source unit can be realized by effectively using most of the light from the light source 12 when used. The effects of the present invention described above can be obtained, for example, it is possible to avoid the occurrence of extreme unevenness in the intensity distribution of the light obtained.

  Further, the pinhole mirror 45 is obtained by forming the reflective film 51 on the transparent substrate 52, and can be easily reduced in thickness. Therefore, the use of the pinhole mirror 45 as the optical path combining means increases the degree of freedom in the arrangement angle of the pinhole mirror 45. Therefore, for example, the pinhole mirror 45 is tilted in a direction in which the reflection surface of the pinhole mirror 45 approaches parallel to the light incident surface 22b of the hologram photosensitive material 22a (the intersection of the reflection surface of the pinhole mirror 45 and the axis B). It is also possible to make the angle more vertical).

  As a result, the condenser lens 41 can be disposed close to the pinhole mirror 45. For example, the NA of the condenser lens 41 can be increased, in other words, the focal length of the condenser lens 41 can be shortened. It becomes possible. As a result, when the produced hologram optical element 22 is used, light having a wider radiation angle among the light emitted from the light source 12 disposed at the position corresponding to the condensing point of the diverging light is transmitted to the hologram optical element 22. Accordingly, it is possible to realize a light source unit that emits brighter light.

(7. Modification 3 of manufacturing optical system)
The example in which the two light beams are incident on the hologram photosensitive material 22a at the time of exposure has been described above. However, it may not be perfectly coaxial. For example, FIG. 9 is a cross-sectional view showing the configuration of the main part of the manufacturing optical system in which two light beams incident on the hologram photosensitive material 22a during exposure are substantially coaxial. In the figure, of the two light beams incident on the hologram photosensitive material 22a during exposure, the optical axis of the optical system that generates the reference light L1 is defined as the axis B1, and the optical axis of the optical system that generates the object light L2 is defined as the axis B2. It is said. FIG. 10 is a cross-sectional view showing a schematic configuration of the hologram optical element 22 manufactured by the manufacturing optical system.

  The hologram optical element 22 can be produced, for example, by exposing the hologram photosensitive material 22a by appropriately setting the inclination angle of the pinhole mirror 45 with respect to the axis B1 and the incident angle of the object light L2 with respect to the pinhole mirror 45. it can. Therefore, in such a manufacturing optical system, the pinhole mirror 45 combines the optical paths of the two light beams so that the two light beams traveling in different directions at the time of exposure enter the hologram photosensitive material 22a substantially coaxially. Functions as a synthesis means.

  As described above, even if two light beams are incident on the hologram photosensitive material 22a substantially coaxially at the time of exposure, it is possible to obtain the hologram optical element 22 having a large deflection angle on the plus side and the minus side. It is possible to use most of the light from the light source 12 (light with a wide radiation angle). Therefore, even with such an exposure method, a light source unit that emits bright light can be realized.

  The intersection angle between the axes B1 and B2 of the two light beams at the time of exposure may be 5 ° or less, for example, or 10 ° or less. In short, it is sufficient that the produced hologram optical element 22 has an intersecting angle that can realize both the plus side and minus side deflection angles.

(8. Other configurations of the hologram optical element)
FIG. 11 shows another configuration of the hologram optical element 22, in which divergent light from a point P (light source 12) incident upon use is emitted in parallel at an angle other than perpendicular to the light exit surface 22c. It is sectional drawing which shows the schematic structure of the hologram optical element 22 to be performed.

  The hologram optical element 22 has the hologram photosensitive material 22a positioned so that the substrate 21 (see FIG. 2) is inclined with respect to the axis B at an angle other than perpendicular in the manufacturing optical system of FIG. 1, FIG. 7, or FIG. It can be produced by exposing it with two light beams. The light source unit can be downsized in the axis A direction by combining the hologram optical element 22 thus manufactured with the light source 12 to form a light source unit.

  In the figure, the axis B of the production optical system and the axis A of the optical system in use are not coaxial, but the hologram optical element 22 is arranged so that the axis A and the axis B are coaxial. Of course, the hologram optical element 22 can be tilted with respect to the axis A.

(9. Other configurations of hologram substrate)
FIG. 12 is a cross-sectional view showing another configuration of the hologram substrate 2. This hologram substrate 2 uses a transparent substrate 23 in place of the substrate 21 and has a hologram optical element 22 formed thereon. However, the hologram substrate 2 has a flat plate shape in that the substrate 23 has a lens portion 23a. This is different from the substrate 21. In use, the hologram substrate 2 is arranged in the optical system so that the substrate 23 is positioned on the light incident side with respect to the hologram optical element 22.

  The lens portion 23 a has a predetermined optical power, and is formed at a position corresponding to the hologram non-configuration region 31 of the hologram optical element 22 on the substrate 23. Such a hologram substrate 2 is obtained by attaching a hologram photosensitive material 22a on a substrate 23 with a lens portion 23a and exposing it with two light beams. When the hologram photosensitive material 22a is pasted on the substrate 23, the hologram photosensitive material 22a is positioned and pasted with the substrate 23 (lens portion 23a) in a state where a portion corresponding to the hologram non-configuration region 31 has been removed in advance. Attached. That is, in FIG. 12, the hologram non-configuration area 31 is configured by holes. Even when the hologram optical element 22 is manufactured using such a hologram photosensitive material 22a, the above-described various methods can be used as the method for exposing the hologram photosensitive material 22a.

  When the hologram substrate 2 is configured as shown in FIG. 12, after the incident light is deflected (refracted) by the lens portion 23a of the substrate 23, the light is incident on the hologram non-configuration region 31 and transmitted therethrough. it can. Therefore, when the diffraction and deflection of incident light in the hologram configuration region 32 are considered together, the hologram substrate 2 as a whole can be equivalent to one condenser lens. Note that the provision of the lens portion 23a does not significantly increase the thickness of the entire hologram substrate 2.

(10. Others)
In this embodiment, the example in which the exposure of the hologram photosensitive material 22 is performed with light of a single color (532 nm) has been described. However, three types of interference fringes corresponding to RGB are applied to the hologram photosensitive by using RGB laser light at the time of exposure. A hologram optical element 22 that diffracts light of three colors of RGB may be produced by forming the material 22a. In this case, a thin white light source module with good alignment characteristics can be realized by using the light source 12 in which the wavelength of the intensity peak of the RGB emitted light is close to the RGB diffraction peak wavelength in the hologram optical element 22.

  In the hologram optical element 22 of the present embodiment, the hologram constituent area 32 is formed in a ring shape around the hologram non-constituent area 31, so that the hologram optical element 22 is formed with an imaging lens (for example, an objective of a cheap and thin pickup). It can also be used as a lens.

  In addition, once the hologram optical element 22 is produced by the method of this embodiment, it is also possible to produce a duplicate hologram by contact copy with the master optical hologram 22 by using it as a master hologram.

[Embodiment 2]
The following will describe another embodiment of the present invention with reference to the drawings. For convenience of explanation below, the same components as those in the first embodiment are denoted by the same member numbers, and description thereof is omitted. In the present embodiment, when light emitted after being diffracted and deflected by the hologram constituent region 32 of the hologram optical element 22 during use is not parallel to the axis A, more specifically, as two light beams used for exposure of the hologram photosensitive material 22a. In both cases, a case where a light beam that becomes divergent light upon incidence on the hologram photosensitive material 22a is used will be described.

  FIG. 13 is a cross-sectional view showing a detailed configuration of the hologram optical element 22 of the present embodiment. The hologram optical element 22 of the present embodiment emits a light beam having a smaller radiation angle (divergence angle) than the diverging light when the diverging light from the point P is diffracted and deflected in the hologram constituent area 32. The configuration is the same as that of the first embodiment except that the hologram configuration region 32 is formed. Therefore, in this hologram optical element 22, as it is used, it is as if the light source 12 is arranged at a point Q on the axis A and further away from the point P, and light is emitted therefrom. A large deflection angle is realized.

  FIG. 14 is a cross-sectional view showing a schematic configuration of a main part of a manufacturing optical system used when manufacturing the hologram optical element 22 of the present embodiment. This manufacturing optical system is configured so that both the two light beams incident on the hologram photosensitive material 22a at the time of exposure become divergent light. That is, the condensing lens 41 and the pinhole mirror 45 are arranged in the optical path of the optical system that generates one divergent light. At this time, the pinhole mirror 45 is disposed so that the hole 51 a of the reflective film 51 is positioned at the condensing position of the condensing lens 41. The condensing position of the condensing lens 41 is closer to the hologram photosensitive material 22a than the condensing position of the condensing lens 46 described later. On the other hand, in the optical path of the other optical system that generates diverging light, there are a condenser lens 46, a pinhole 47 (spatial filter) having a hole 47a in the center, and the pinhole mirror 45. Is arranged. At this time, the hole 47 a of the pinhole 47 is located at the condensing position of the condensing lens 46.

  In such a manufacturing optical system, one light beam (for example, P-polarized reference light L1) is incident on the hologram photosensitive material 22a via the condenser lens 41 and the hole 51a of the reflection film 51 of the pinhole mirror 45, and the other. (For example, P-polarized object light L2) is incident on the hologram photosensitive material 22a through the condenser lens 46, the hole 47a of the pinhole 47, and the pinhole mirror 45.

  At this time, since the hole 51a of the pinhole mirror 45 is located at the condensing position of the condensing lens 41, the reference light L1 is once condensed at the position of the hole 51a, and then becomes divergent light from the hologram photosensitive material. The light is incident on 22a as P-polarized light. Further, since the hole 47a of the pinhole 47 is located at the condensing position of the condensing lens 46, the object light L2 is once condensed at the position of the hole 47a, and then becomes divergent light, which is reflected by the reflecting film 51. The light enters the pinhole mirror 45 with a larger light beam diameter than the hole 51a. The light reflected by the reflective film 51 (portion other than the hole 51a) is incident on the hologram photosensitive material 22a in the P-polarized state coaxially with the reference light L1, but is incident on the hole 51a of the reflective film 51. Does not enter the hologram photosensitive material 22a because it passes therethrough.

  Accordingly, in the hologram photosensitive material 22a, only one light beam (only the reference light L1) is incident on the region corresponding to the hole 51a of the reflection film 51 of the pinhole mirror 45, so that no interference fringes are formed. On the other hand, in the hologram photosensitive material 22a, in the region corresponding to the formation region (excluding the hole 51a) of the reflection film 51 of the pinhole mirror 45 within the incident range of the object light L2, both the two light beams have the same polarization state (the above-mentioned In this example, the incident light is P-polarized light, so that the two light beams interfere with each other to form interference fringes. That is, in the produced hologram optical element 22, the hologram non-configuration region 31 is formed corresponding to the hole 51 a of the reflection film 51 of the pinhole mirror 45, and the hologram is formed so as to surround the hologram non-configuration region 31 around the optical axis. A configuration region 32 is formed.

  Moreover, since the hologram constituent area 32 is formed by the interference between the divergent lights, the divergent light is emitted from the hologram constituent area 32 in use. More specifically, in the present embodiment, the condensing position of the condensing lens 41 in the manufacturing optical system is closer to the hologram photosensitive material 22a than the condensing position of the condensing lens 46, so that exposure is performed. When the light source 12 is arranged at a position corresponding to the condensing position of the reference light L1 at that time, light having a smaller divergence angle than the divergent light from the light source 12 (light having the same optical path as the object light L2) is transmitted from the hologram configuration region 32. Emitted.

  As described above, when the hologram optical element 22 is manufactured using the manufacturing optical system of FIG. 14, both of the two light beams used at the time of exposure are light beams that become divergent light when incident on the hologram photosensitive material 22a. Even in this case, two light beams can be incident on the hologram photosensitive material 22a coaxially, and the hologram composition region 32 can be formed so as to surround the hologram non-configuration region 31 around the optical axis. Therefore, even when the hologram optical element 22 is manufactured using the manufacturing optical system of FIG. 14, a bright light source unit can be realized by effectively using most of the light from the light source 12 when used, via the hologram optical element 22. The effects similar to those of the first embodiment can be obtained, for example, it is possible to avoid the occurrence of extreme unevenness in the light intensity distribution obtained in this way.

  In the present embodiment, when the produced hologram optical element 22 is used, light having a smaller divergence angle than the divergent light from the light source 12 is emitted from the hologram constituent region 32. Therefore, such light is required during use. The hologram optical element 22 of this embodiment is suitable for the optical system to be used.

[Embodiment 3]
The following will describe still another embodiment of the present invention with reference to the drawings. For convenience of explanation below, the same components as those in the first and second embodiments are denoted by the same member numbers, and the description thereof is omitted. In the present embodiment, when light emitted after being diffracted and deflected by the hologram constituent region 32 of the hologram optical element 22 during use is not parallel to the axis A, more specifically, as two light beams used for exposure of the hologram photosensitive material 22a. A case where a light beam (for example, reference light L1) that becomes divergent light when incident on the hologram photosensitive material 22a and a light beam (for example, object light L2) that becomes convergent light will be described.

  FIG. 15 is a cross-sectional view showing a detailed configuration of the hologram optical element 22 of the present embodiment. The hologram optical element 22 of the present embodiment has the exception that the hologram constituent area 32 is formed so that convergent light is emitted as a whole when the divergent light from the point P is diffracted and deflected by the hologram constituent area 32. The configuration is the same as that of the first embodiment.

  FIG. 16 is a cross-sectional view showing a schematic configuration of a main part of a manufacturing optical system used when manufacturing the hologram optical element 22 of the present embodiment. This manufacturing optical system is configured such that one of the two light beams incident on the hologram photosensitive material 22a during exposure is divergent light and the other is convergent light. That is, the condensing lens 41 and the pinhole mirror 45 are arranged in the optical path of the optical system that generates one divergent light. At this time, the pinhole mirror 45 is disposed so that the hole 51 a of the reflective film 51 is positioned at the condensing position of the condensing lens 41. On the other hand, the condenser lens 48 and the pinhole mirror 45 are arranged in the optical path of the other optical system that generates the convergent light. At this time, the condensing position of the condensing lens 48 is set to the opposite side to the condensing position of the condensing lens 41 with respect to the hologram photosensitive material 22a.

  In such a manufacturing optical system, one light beam (for example, P-polarized reference light L1) is incident on the hologram photosensitive material 22a via the condenser lens 41 and the hole 51a of the reflection film 51 of the pinhole mirror 45, and the other. Of light (for example, P-polarized object light L2) is incident on the hologram photosensitive material 22a via the condenser lens 48 and the pinhole mirror 45.

  At this time, since the hole 51a of the pinhole mirror 45 is located at the condensing position of the condensing lens 41, the reference light L1 is once condensed at the position of the hole 51a, and then becomes divergent light from the hologram photosensitive material. The light is incident on 22a as P-polarized light. The object light L2 is collected by the condenser lens 48 and is incident on the pinhole mirror 45 with a larger beam diameter than the hole 51a of the reflective film 51. At this time, in the object light L2, light incident on the reflection film 51 (portion other than the hole 51a) is reflected there, and is incident on the hologram photosensitive material 22a as convergent light in the P-polarized state coaxially with the reference light L1. The light incident on the hole 51a of the reflective film 51 passes therethrough and does not enter the hologram photosensitive material 22a.

  Accordingly, in the hologram photosensitive material 22a, only one light beam (only the reference light L1) is incident on the region corresponding to the hole 51a of the reflection film 51 of the pinhole mirror 45, so that no interference fringes are formed. On the other hand, in the hologram photosensitive material 22a, in the region corresponding to the formation region (excluding the hole 51a) of the reflection film 51 of the pinhole mirror 45 within the incident range of the object light L2, both the two light beams have the same polarization state (the above-mentioned In this example, the incident light is P-polarized light, so that the two light beams interfere with each other to form interference fringes. That is, in the produced hologram optical element 22, the hologram non-configuration region 31 is formed corresponding to the hole 51 a of the reflection film 51 of the pinhole mirror 45, and the hologram is formed so as to surround the hologram non-configuration region 31 around the optical axis. A configuration region 32 is formed.

  Moreover, since the hologram construction region 32 is formed by the interference between the divergent light and the convergent light, it is used when the light source 12 that emits the divergent light is arranged at a position corresponding to the condensing position of the reference light L1 at the time of exposure. Sometimes convergent light is emitted from the hologram construction region 32.

  As described above, when the hologram optical element 22 is manufactured using the manufacturing optical system of FIG. 16, one of the two light beams used at the time of exposure is divergent light and the other is convergent light. In addition, two light beams can be coaxially incident on the hologram photosensitive material 22a, and the hologram composition region 32 can be formed so as to surround the hologram non-configuration region 31 around the optical axis. Therefore, even when the hologram optical element 22 is manufactured using the manufacturing optical system of FIG. 16, a bright light source unit can be realized by effectively using most of the light from the light source 12 when used. The effects similar to those of the first embodiment can be obtained, for example, it is possible to avoid the occurrence of extreme unevenness in the light intensity distribution obtained in this way.

  Further, in the present embodiment, when the produced hologram optical element 22 is used, although the light source 12 that emits divergent light is used, convergent light is emitted from the hologram constituent region 32 by diffraction and deflection there. Therefore, the hologram optical element 22 of the present embodiment is suitable for an optical system that requires such light during use.

  Of course, it is possible to appropriately combine the configurations and methods described in the above embodiments to form a hologram optical element and thus a light source unit, or to manufacture a hologram optical element.

  The hologram optical element manufactured by the manufacturing method of the present invention can be used for various illumination devices including a light source unit, for example.

It is sectional drawing which shows the schematic structure of the principal part of the manufacturing optical system used when manufacturing the hologram optical element applied to the light source unit which concerns on one Embodiment of this invention. It is sectional drawing which shows the schematic structure of the said light source unit. It is sectional drawing which shows the detailed structure of the said hologram optical element. It is explanatory drawing which expands and shows the optical path of the light which injects into a hologram photosensitive material from the polarization state conversion member of the said manufacturing optical system. It is a graph which shows the result of having simulated the relationship between the deflection angle at the time of use of the said hologram optical element, and diffraction efficiency. It is a graph which shows the result of having simulated the relationship between the deflection angle at the time of use of another hologram optical element, and diffraction efficiency. It is sectional drawing which shows the other structure of the principal part of the said manufacturing optical system. It is sectional drawing which shows the further another structure of the principal part of the said manufacturing optical system. It is sectional drawing which shows the further another structure of the principal part of the said manufacturing optical system. FIG. 10 is a cross-sectional view illustrating a schematic configuration of a hologram optical element manufactured by the manufacturing optical system of FIG. 9. It is sectional drawing which shows the other structure of the said hologram optical element. It is sectional drawing which shows the other structure of the hologram substrate applied to the said light source unit. It is sectional drawing which shows the detailed structure of the hologram optical element which concerns on other embodiment of this invention. It is sectional drawing which shows the structure of the outline of the principal part of the manufacturing optical system used when manufacturing the said hologram optical element. It is sectional drawing which shows the detailed structure of the hologram optical element which concerns on further another embodiment of this invention. It is sectional drawing which shows the structure of the outline of the principal part of the manufacturing optical system used when manufacturing the said hologram optical element. (A) is sectional drawing which shows the schematic structure of the conventional light source unit, (b) is sectional drawing which shows the manufacturing method of the hologram optical element used for the said light source unit. It is explanatory drawing which shows typically the concept of the deflection angle in the said hologram optical element. It is a graph which shows the result of having simulated the relationship between the deflection angle at the time of use of the said hologram optical element, and diffraction efficiency.

Explanation of symbols

DESCRIPTION OF SYMBOLS 12 Light source 22 Hologram optical element 22a Hologram photosensitive material 23 Substrate 23a Lens part 31 Hologram non-construction area | region 32 Hologram composition area | region 41 Condensing lens 42 PBS (optical path synthesis means)
43 Polarization state conversion member (polarization state conversion means)
43a 1st area | region 43b 2nd area | region 44 Polarization state conversion member (polarization state conversion means)
44a First region 44b Second region 45 Pinhole mirror (optical path combining means)
51 Reflective film 51a Hole L1 Reference light L2 Object light

Claims (18)

A hologram optical element manufacturing method for producing a volume phase type transmission hologram optical element by exposing a hologram photosensitive material with two light beams,
As a light beam of at least one of the two light beams, a light beam that becomes divergent light when incident on the hologram photosensitive material is used.
A method for manufacturing a hologram optical element, wherein two light beams are incident on a hologram photosensitive material coaxially or substantially coaxially.   2. The method of manufacturing a hologram optical element according to claim 1, wherein the two light beams are incident on a hologram photosensitive material after being subjected to optical path synthesis by an optical path synthesis unit. As the optical path combining means, a polarizing beam splitter that transmits or reflects incident light according to the polarization state is used.
In the optical path of the optical system that generates the divergent light, a condenser lens, the polarization beam splitter, and a polarization state conversion unit are disposed,
The polarization state converting means includes
A first region that maintains the polarization state of the incident light;
A second region for converting the polarization state of the incident light,
One of the first and second regions is located at the condensing position of the condenser lens, and the other is formed so as to surround one around the optical axis,
One light beam is applied to the hologram photosensitive material through a region located at a condensing position of the condensing lens among the first and second regions of the condensing lens, the polarizing beam splitter, and the polarization state converting means. Incident,
3. The hologram optical element according to claim 2, wherein the other light beam is incident on the hologram photosensitive material through both the polarization beam splitter and the first and second regions of the polarization state converting means. Method. The first region of the polarization state conversion means is located at the condensing position of the condensing lens, and the second region is formed so as to surround the first region around the optical axis,
The second region is composed of a half-wave plate,
4. The method for manufacturing a hologram optical element according to claim 3, wherein the first region is formed by a hole formed in the half-wave plate. The second region of the polarization state converting means is located at the condensing position of the condensing lens, and the first region is formed so as to surround the second region around the optical axis,
The first region is composed of a transparent substrate,
4. The method of manufacturing a hologram optical element according to claim 3, wherein the second region is constituted by a half-wave plate. As the optical path synthesis means, using a pinhole mirror in which a reflective film having a hole is formed on a transparent substrate,
The condensing lens and the pinhole mirror are arranged in the optical path of the optical system that generates the divergent light, and the pinhole is arranged such that the hole of the reflecting film is positioned at the condensing position of the condensing lens. Place the mirror,
One light beam is incident on the hologram photosensitive material through the condenser lens and the hole in the reflection film of the pinhole mirror,
The other light beam is incident on a region including the hole of the reflection film with a larger beam diameter than the hole of the reflection film with respect to the pinhole mirror, and the light beam reflected by the reflection film is incident on the hologram photosensitive material. A method for manufacturing a hologram optical element according to claim 2.   7. The optical axis of an optical system that respectively generates two light beams incident on a hologram photosensitive material is coaxial with the optical system in use of the produced hologram optical element. Manufacturing method of the hologram optical element.   3. The method of manufacturing a hologram optical element according to claim 1, wherein a light beam that becomes divergent light when incident on the hologram photosensitive material is used as both of the two light beams used for exposure of the hologram photosensitive material.   Of the two light beams used for exposure of the hologram photosensitive material, a light beam that becomes divergent light when incident on the hologram photosensitive material is used as one light beam, and a light beam that becomes convergent light when incident on the hologram photosensitive material is used as the other light beam. A method for manufacturing a hologram optical element according to claim 1 or 2. A volume phase transmission hologram optical element,
A hologram optical element manufactured by the manufacturing method according to claim 1. A volume phase transmission hologram optical element,
A hologram non-configuration region where the hologram is not configured; and
A hologram composition region in which the hologram is configured,
The hologram optical element, wherein the hologram constituent area is formed so as to surround the hologram non-constituent area. Of the angles formed by the light rays incident on the hologram constituent area and the extension lines of the outgoing light rays when the light rays are diffracted, deflected and emitted in the hologram constituent area, the acute angle is defined as the deflection angle.
12. The hologram optical element according to claim 11, wherein the absolute value of the deflection angle in the hologram constituent area is 5 [deg.] Or more.   The hologram optical element according to claim 12, wherein the hologram photosensitive material that forms the hologram constituent region is made of a photopolymer. Of the angles formed by the light rays incident on the hologram constituent area and the extension lines of the outgoing light rays when the light rays are diffracted, deflected and emitted in the hologram constituent area, the acute angle is defined as the deflection angle.
12. The hologram optical element according to claim 11, wherein the absolute value of the deflection angle in the hologram constituent area is an angle at which the diffraction efficiency of the primary light in the hologram constituent area is 50% or more of the maximum diffraction efficiency.   The hologram optical element according to claim 10, wherein the hologram optical element is rotationally symmetric. The hologram optical element is produced by exposing a hologram photosensitive material formed on a transparent substrate with two light beams,
The transparent substrate is a substrate with a lens in which a lens portion is formed on a part of the substrate,
The hologram optical element according to claim 10, wherein the lens unit is positioned corresponding to a hologram non-formation region. A light source;
A volume phase transmission hologram optical element disposed in front of the light source,
The light source unit, wherein the hologram optical element is constituted by the hologram optical element according to any one of claims 10 to 16.   18. The wavelength of the two light beams used at the time of exposure of the hologram photosensitive material that is a source for producing the hologram optical element is within ± 20 nm of the peak wavelength of the light emitted from the light source at the time of use. The light source unit described in 1.

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