JP5621640B2 - Lighting device using a coherent light source - Google Patents

Description

  The present invention relates to an illumination device using a coherent light source. In particular, the present invention relates to a technique for reducing speckle noise in an illumination device that uses coherent light generated by a laser light source as illumination light.

  Incandescent bulbs and fluorescent lamps have long been used as light sources for lighting devices. For lighting devices that require illumination light with high luminance, mercury lamps, halogen lamps, xenon lamps, and the like are used as light sources. For example, Patent Document 1 below discloses an illumination device using an ultrahigh pressure mercury lamp and a projection type video display device using the same. Furthermore, recently, lighting devices using LEDs as light sources have begun to spread. The lifetime of LEDs is generally 10,000 hours or more, and is attracting attention as a new general-purpose light source that can replace incandescent bulbs and fluorescent lamps.

  On the other hand, laser light sources are widely used in various industrial fields as light sources for generating coherent light. Specifically, utilizing unique characteristics such as monochromaticity, directivity, and coherence, laser light is widely used in optical communication fields, semiconductor device manufacturing fields, optical fields such as holograms, and the like. In particular, the semiconductor laser has a sufficiently long life as a practical light source, and the energy utilization efficiency is extremely excellent. Despite having such an advantage, the reason why illumination devices using laser light sources have not been widely used so far is that there is a unique problem of generation of speckle noise.

  A speckle is a speckled pattern that appears when a diffused surface is irradiated with coherent light such as laser light. When a laser beam is irradiated on an object to be illuminated, speckles appear as uneven brightness on the irradiated surface. Observed. For example, when one point on the screen is indicated by the laser pointer, the spot of the laser beam appears to shine on the screen. This is because speckle noise is generated on the screen, which causes a physiological adverse effect on the observer. The reason that speckle is generated when coherent light is used is that coherent light reflected by each part of a diffuse reflection surface such as a screen interferes with each other due to its extremely high coherence. For example, in the following Non-Patent Document 1, detailed theoretical considerations regarding speckle generation are made.

  If it is an application like a laser pointer, the observer can only see a minute spot, so that no big problem occurs. However, when a laser light source is used as a light source of an illumination device and a certain wide area is illuminated with coherent light, the speckle noise generated in the illumination area has a physiological adverse effect on the observer and makes the patient feel unwell Appears. Due to such problems, conventionally, an illumination device using a laser light source has been considered unsuitable for general applications.

  Of course, several specific methods for reducing such speckle noise have been proposed. For example, Patent Document 2 discloses a technique for reducing speckles by irradiating a scattering plate with laser light, using the scattered light obtained therefrom as illumination light, and rotating the scattering plate with a motor. Has been. Patent Document 3 discloses a technique for reducing speckles by disposing a light diffusing element between a laser light source and an object to be illuminated and vibrating the light diffusing element.

JP 2004-264512 A Japanese Patent Laid-Open No. 6-208089 JP 2004-144936 A

Speckle Phenomena in Optics, Joseph W. Goodman, Roberts & Co., 2006

  However, in order to rotate the scattering plate or vibrate the light diffusing element, a large mechanical drive mechanism is required, which increases the overall size of the apparatus and increases the power consumption. In addition, such a method cannot always effectively remove speckles.

  Therefore, an object of the present invention is to provide a technique for efficiently and sufficiently suppressing speckle generation in an illumination device using a coherent light source.

Hereinafter, the first aspect to the twenty-seventh aspect of the invention disclosed in the present application will be listed, which corresponds to the inventions according to claims 1 to 3 described in “Claims” of the present application. Of these, the aspects are the 25th aspect and the 26th aspect.

(1) A first aspect of the present invention is an illumination device using a coherent light source,
A coherent light source that generates a coherent light beam;
A hologram recording medium on which an image of a scattering plate is recorded;
A light beam scanning device that irradiates the hologram recording medium with a light beam and performs scanning so that the irradiation position of the light beam with respect to the hologram recording medium changes with time;
Provided,
On the hologram recording medium, an image of the scattering plate is recorded as a hologram using reference light irradiated along a predetermined optical path,
The coherent light source generates a light beam with a wavelength that can reproduce the image of the scattering plate,
The light beam scanning device scans the light beam so that the irradiation direction of the light beam on the hologram recording medium is in a direction along the optical path of the reference light,
The reproduction light of the image of the scattering plate obtained from the hologram recording medium is used as illumination light.

(2) According to a second aspect of the present invention, in the illumination device using the coherent light source according to the first aspect described above,
The light beam scanning apparatus bends the light beam by bending the light beam at a predetermined scanning base point, irradiating the bent light beam onto the hologram recording medium, and temporally changing the bending mode of the light beam. Change the irradiation position of the beam on the hologram recording medium over time,
In the hologram recording medium, an image of a scattering plate is recorded as a hologram using reference light that converges at a specific convergence point or reference light that diverges from a specific convergence point,
The light beam scanning device scans the light beam with the convergence point as the scanning base point.

(3) According to a third aspect of the present invention, in the illumination device using the coherent light source according to the second aspect described above,
An image of the scattering plate is recorded on the hologram recording medium using reference light that converges or diverges three-dimensionally along the side surface of the cone having the convergence point as the apex.

(4) According to a fourth aspect of the present invention, in the illumination device using the coherent light source according to the third aspect described above,
The light beam scanning device has a function of bending the light beam so as to perform a swinging motion on a plane including the scanning base point, and scans the light beam on the hologram recording medium in a one-dimensional direction. .

(5) According to a fifth aspect of the present invention, in the illumination device using the coherent light source according to the third aspect described above,
The light beam scanning device bends the light beam so as to perform a swinging motion on the first plane including the scanning base point, and swings on the second plane including the scanning base point and orthogonal to the first plane. And a function of bending the light beam so as to move, and the light beam is scanned in a two-dimensional direction on the hologram recording medium.

(6) According to a sixth aspect of the present invention, in the illumination device using the coherent light source according to the second aspect described above,
An image of the scattering plate is recorded on the hologram recording medium using reference light that converges or diverges two-dimensionally along a plane including the convergence point.

(7) According to a seventh aspect of the present invention, in the illumination device using the coherent light source according to the sixth aspect described above,
The light beam scanning device has a function of bending the light beam so as to perform a swinging motion on a plane including the scanning base point, and scans the light beam on the hologram recording medium in a one-dimensional direction. .

(8) According to an eighth aspect of the present invention, in the illumination device using the coherent light source according to the first aspect described above,
The light beam scanning device irradiates the hologram recording medium while moving the light beam in parallel, thereby changing the irradiation position of the light beam with respect to the hologram recording medium over time,
In the hologram recording medium, an image of the scattering plate is recorded as a hologram using reference light composed of parallel light beams,
The light beam scanning device irradiates the hologram recording medium with a light beam from a direction parallel to the reference light to scan the light beam.

(9) According to a ninth aspect of the present invention, in the illumination device using the coherent light source according to the first to eighth aspects described above,
The coherent light source is a laser light source that generates a laser beam.

(10) According to a tenth aspect of the present invention, in the illumination device using the coherent light source according to the first to ninth aspects described above,
The hologram recording medium records a scattering plate image as a volume hologram.

(11) An eleventh aspect of the present invention is an illumination device using the coherent light source according to the first to ninth aspects described above.
The hologram recording medium records the image of the scattering plate as a surface relief hologram.

(12) According to a twelfth aspect of the present invention, in the illumination device using the coherent light source according to the first to ninth aspects described above,
The hologram recorded on the hologram recording medium is a computer-generated hologram.

(13) According to a thirteenth aspect of the present invention, in the illumination device using the coherent light source according to the first to ninth aspects described above,
The hologram recorded on the hologram recording medium is a Fourier transform hologram.

(14) According to a fourteenth aspect of the present invention, in the illumination device using the coherent light source according to the first to ninth aspects described above,
The hologram recorded on the hologram recording medium is a reflection hologram, and the reflected diffracted light of the light beam is used as illumination light.

(15) According to a fifteenth aspect of the present invention, in the illumination device using the coherent light source according to the first to ninth aspects described above,
The hologram recorded on the hologram recording medium is a transmission hologram, and transmitted diffraction light of a light beam is used as illumination light.

(16) According to a sixteenth aspect of the present invention, in the illumination device using the coherent light source according to the first to fifteenth aspects described above,
The light beam scanning device is a scanning mirror device, a total reflection prism, a refraction prism, or an electro-optic crystal.

(17) According to a seventeenth aspect of the present invention, in the illumination device using the coherent light source according to the first to sixteenth aspects described above,
The coherent light source includes a plurality of n laser light sources that generate monochromatic laser beams having different wavelengths, and a light combiner that combines the laser beams generated by the n laser light sources to generate a combined light beam. Have
A light beam scanning device scans the hologram recording medium with the combined light beam generated by the light combiner;
On the hologram recording medium, images of the scattering plate are recorded as n types of holograms so that reproduced images can be obtained by the respective laser beams generated by the n laser light sources.

(18) According to an eighteenth aspect of the present invention, there is provided an image by an illuminating device using the coherent light source according to the first to seventeenth aspects described above and a display medium having a light receiving surface that receives illumination by the illuminating device. Configure the display device,
The image of the scattering plate covered with a transmission film on which a predetermined image is drawn is recorded on the hologram recording medium,
The light receiving surface is arranged at a position where a reproduction image of the scattering plate is formed.

(19) A nineteenth aspect of the present invention is an illumination method using a coherent light source,
A preparation stage for creating a hologram recording medium by recording an image of a scattering plate on a recording medium as a hologram;
Illuminating the hologram recording medium with a coherent light beam and scanning the light beam on the hologram recording medium so that the irradiation position changes with time; and
And
In the preparation stage, the coherent illumination light is irradiated onto the scattering plate, the scattered light obtained from the scattering plate is used as the object light, the recording medium is irradiated along a predetermined optical path, and the coherent light having the same wavelength as the illumination light is emitted. Use as reference light, create a hologram recording medium by recording interference fringes formed by object light and reference light on a recording medium,
In the illumination stage, scanning is performed so that a light beam having a wavelength capable of reproducing the image of the scattering plate is directed to an irradiation position on the hologram recording medium through an optical path along the optical path of the reference light,
The reproduction light of the image of the scattering plate obtained from the hologram recording medium is used as illumination light.

(20) According to a twentieth aspect of the present invention, in the illumination method using the coherent light source according to the nineteenth aspect described above,
At the preparatory stage, by using a convex lens that has a focal point at the position of the predetermined convergence point, the light beam of almost parallel coherent light is condensed, so that the reference beam converges three-dimensionally at the convergence point or three-dimensionally from the convergence point. A reference beam that diverges in a normal manner is generated, and interference fringes are recorded using the generated reference beam.

(21) According to a twenty-first aspect of the present invention, in the illumination method using the coherent light source according to the nineteenth aspect described above,
At the preparatory stage, a cylindrical lens having a central axis parallel to the predetermined condensing axis is used to condense a light beam of substantially parallel coherent light onto the condensing axis, thereby two-dimensionally focusing on a point on the condensing axis. The reference light that converges automatically or the reference light that diverges two-dimensionally from a point on the condensing axis is generated, and interference fringes are recorded using the generated reference light.

(22) According to a twenty-second aspect of the present invention, in the illumination method using the coherent light source according to the nineteenth aspect described above,
In the preparation stage, interference fringes are recorded using reference light composed of parallel light beams.

(23) According to a twenty-third aspect of the present invention, in the illumination method using the coherent light source according to the nineteenth to twenty-second aspects described above,
The preparatory process is executed by a simulation calculation using a virtual scattering plate, and the computer-generated hologram is recorded on the hologram recording medium.

(24) According to a twenty-fourth aspect of the present invention, in the illumination method using the coherent light source according to the twenty-third aspect described above,
As the virtual scattering plate, a model in which a large number of point light sources are arranged in a grid on a plane is used.

(25) A twenty-fifth aspect of the present invention is an illumination device using a coherent light source,
A coherent light source that generates a coherent light beam;
A microlens array consisting of a collection of many individual lenses;
A light beam scanning device that irradiates a microlens array with a light beam and scans so that the irradiation position of the light beam with respect to the microlens array changes with time, and
Provided,
Each of the individual lenses constituting the microlens array has a function of refracting light irradiated from the light beam scanning device to form a predetermined irradiation area on a predetermined light receiving surface, and any individual lens. The irradiation region formed by the structure is also configured to be substantially the same common region on the light receiving surface ,
The light beam scanning device includes a reflecting mirror that reflects the light beam and a rotating mechanism that rotates the reflecting mirror with a scanning base point defined on the reflecting surface as a fixed point, and reflects the light beam. By reflecting and bending with a mirror and irradiating the microlens array, and changing the bending mode of the light beam with time, the irradiation position of the bent light beam with respect to the microlens array is changed with time,
Each of the individual lenses constituting the microlens array refracts the light reflected and bent by the reflecting mirror to form a common irradiation area on the light receiving surface.

(26) According to a twenty-sixth aspect of the present invention, in the illumination device using the coherent light source according to the twenty-fifth aspect,
In the microlens array, a large number of individual lenses are arranged two-dimensionally,
When the rotation mechanism of the light beam scanning device defines a V axis and a W axis that pass through the scanning base point and are orthogonal to each other on the reflecting surface, a mechanism for rotating the reflecting mirror around the V axis and a rotation around the W axis are provided. The light beam is scanned in the horizontal direction and the vertical direction on the microlens array, or the light beam scanning device rotates the light reflected by the reflecting mirror. The beam is scanned so as to draw a circle on the microlens array.

(27) According to a twenty-seventh aspect of the present invention, in a lighting device using a coherent light source,
A coherent light source that generates a coherent light beam;
A light beam scanning device that performs beam scanning by controlling the direction and / or position of the light beam;
A light diffusing element that diffuses and emits an incident light beam;
Provided,
The light beam scanning device emits the light beam generated by the coherent light source toward the light diffusing element, and scans so that the incident position of the light beam with respect to the light diffusing element changes with time.
The light diffusing element has a function of diffusing an incident light beam to form a predetermined irradiation area on a predetermined light receiving surface, and the formed irradiation area receives the light regardless of the incident position of the light beam. It is configured to be substantially the same common area on the surface.

  ADVANTAGE OF THE INVENTION According to this invention, generation | occurrence | production of a speckle can be suppressed efficiently and fully in the illuminating device using a coherent light source.

FIG. 3 is an arrangement diagram of an optical system showing a process of creating a hologram recording medium that is a component of the illumination device according to the present invention. FIG. 2 is a plan view showing a positional relationship between a cross section S1 of a reference light L23 and a hologram photosensitive medium 40 in the process shown in FIG. FIG. 6 is a plan view showing the positional relationship between another section S2 of the reference light L23 and the hologram photosensitive medium 40 in the process shown in FIG. FIG. 2 is a partially enlarged view around a scattering plate 30 and a hologram photosensitive medium 40 in the optical system shown in FIG. 1. It is a figure which shows the process of reproducing | regenerating the image 35 of a scattering plate using the hologram recording medium 45 produced by the process shown in FIG. It is a figure which shows the process which reproduces | regenerates the image 35 of a scattering plate by irradiating only one light beam with respect to the hologram recording medium 45 produced by the process shown in FIG. FIG. 6 is another diagram showing a process of reproducing the image 35 of the scattering plate by irradiating only one light beam to the hologram recording medium 45 created by the process shown in FIG. It is a top view which shows the irradiation position of the light beam in the reproduction | regeneration process shown in FIG. 6 and FIG. It is a side view which shows the structure of the illuminating device 100 which concerns on basic embodiment of this invention. It is a side view which shows the state which is illuminating the illumination target object 70 using the illuminating device 100 shown in FIG. It is a side view which shows the state which attached the illuminating device 100 shown in FIG. 9 to the ceiling, and is illuminating the upper surface of a table. FIG. 10 is a plan view showing a first example of a scanning mode of a light beam on a hologram recording medium 45 in the illumination device 100 shown in FIG. 9. FIG. 10 is a plan view showing a second example of the scanning mode of the light beam on the hologram recording medium 45 in the illumination device 100 shown in FIG. 9. FIG. 10 is a plan view showing a third example of the scanning mode of the light beam on the hologram recording medium 45 in the illumination device 100 shown in FIG. 9. FIG. 10 is a plan view showing a fourth example of the scanning mode of the light beam on the hologram recording medium 45 in the illumination device 100 shown in FIG. 9. FIG. 6 is a plan view showing a scanning mode of a light beam when a band-shaped hologram recording medium 85 is used. FIG. 17 is an arrangement diagram of an optical system showing a process of creating a strip-shaped hologram recording medium 85 shown in FIG. It is a side view which shows the principle which produces the hologram recording medium which is a component of the illuminating device which concerns on this invention by the method of CGH. FIG. 19 is a front view of a virtual scattering plate 30 ′ shown in FIG. 18. It is a table | surface which shows the experimental result by which the reduction effect of the speckle was acquired by this invention. It is a figure which shows the structural example of the light source in the case of performing white illumination with the illuminating device which concerns on this invention. It is a top view which shows the variation of the scattering plate used when producing the illuminating device which concerns on this invention. It is a top view which shows the transmissive film used when utilizing the illuminating device which concerns on this invention as an image display apparatus. It is a side view which shows the process which produces a reflection type hologram recording medium using convergent reference light. FIG. 25 is a side view showing a reproduction process of the reflection-type hologram recording medium 45 created by the method shown in FIG. 24. It is a side view which shows the process which produces a transmissive hologram recording medium using convergent reference light. FIG. 27 is a side view showing a reproduction process of a transmissive hologram recording medium 45 created by the method shown in FIG. 26. It is a side view which shows the preparation process in the case of producing a hologram recording medium using a divergent reference beam. It is a side view which shows the reproduction | regeneration process of the hologram recording medium 95 for preparation produced by the preparation process of FIG. It is a side view which shows the process of producing a reflection type hologram recording medium using divergent reference light. It is a side view which shows the process which produces a transmissive hologram recording medium using a divergent reference beam. It is a side view which shows another preparation process in the case of producing a hologram recording medium using a divergent reference beam. FIG. 33 is a side view showing a reproduction process of the preparation hologram recording medium 95 created by the preparation process of FIG. 32. FIG. 10 is an arrangement diagram of an optical system showing a process of creating a hologram recording medium that is a component of an illumination device according to a modification of the present invention. It is a side view which shows the basic composition of the illuminating device 110 which concerns on the modification of this invention. It is a side view which shows the basic composition of the illuminating device 120 which concerns on another modification of this invention. It is a side view which shows the principle of operation of the illuminating device 120 shown in FIG.

  Hereinafter, the present invention will be described based on the illustrated embodiments.

<<< §1. Hologram recording medium used in the present invention >>>
First, the characteristics of a hologram recording medium used as a constituent element of an illumination device according to an embodiment of the present invention will be described. FIG. 1 is an arrangement diagram of an optical system showing a process for producing this hologram recording medium. By this optical system, a hologram recording medium on which an image of the scattering plate is recorded is created.

  The coherent light source 10 shown in the upper right of the figure is a light source that generates a coherent light beam L10. In practice, a laser light source that generates monochromatic laser light having a circular cross section is used. The coherent light beam L10 generated by this laser light source is divided into two beams by the beam splitter 20. That is, a part of the light beam L10 is directly transmitted through the beam splitter 20 and guided downward in the figure, and the remaining part is reflected by the beam splitter 20 and guided to the left in the figure as the light beam L20. It is burned.

  The light beam L10 transmitted through the beam splitter 20 plays a role of generating object light Lobj of the scattering plate. That is, the light beam L10 traveling downward in the figure is reflected by the reflecting mirror 11 to become a light beam L11. Further, the diameter of the light beam L10 is expanded by the beam expander 12 to form a parallel light beam L12. The entire area of the surface is irradiated. The scattering plate 30 is a plate having a property of scattering irradiated light, and is generally called an optical diffusion plate. In the case of the embodiment shown here, a transmission type scattering plate (for example, an opal glass plate) in which fine particles (light scatterers) for scattering light are kneaded is used. Therefore, as illustrated, the parallel light beam L12 irradiated on the right side surface of the scattering plate 30 passes through the scattering plate 30 and is emitted as scattered light L30 from the left side surface. The scattered light L30 constitutes the object light Lobj of the scattering plate 30.

  On the other hand, the light beam L20 reflected by the beam splitter 20 plays a role of generating the reference light Lref. That is, the light beam L20 traveling from the beam splitter 20 to the left in the figure is reflected by the reflecting mirror 21 to become the light beam L21. Further, the diameter of the light beam L20 is expanded by the beam expander 22 to form a parallel light beam L22. After being refracted by the convex lens 23 having the focal point C, the hologram photosensitive medium 40 is irradiated. Note that the parallel light beam L22 is not necessarily a strict set of parallel rays, but if it is a set of substantially parallel rays, there is no practical problem. The hologram photosensitive medium 40 is a photosensitive medium used for recording a hologram image. The irradiation light L23 to the hologram photosensitive medium 40 constitutes the reference light Lref.

  Eventually, the hologram photosensitive medium 40 is irradiated with the object light Lobj of the scattering plate 30 and the reference light Lref. Here, since the object light Lobj and the reference light Lref are both coherent light having the same wavelength λ generated by the coherent light source 10 (laser light source), both interference fringes are recorded on the hologram photosensitive medium 40. Will be. In other words, the image of the scattering plate 30 is recorded on the hologram photosensitive medium 40 as a hologram.

  FIG. 2 is a plan view showing the positional relationship between the cross section S1 of the reference light L23 (Lref) shown in FIG. Since the parallel light beam L22 whose diameter is expanded by the beam expander 22 has a circular cross section, the reference light Lref collected by the convex lens 23 converges in a conical shape with the focal point C of the lens as the apex. However, in the example shown in FIG. 1, since the hologram photosensitive medium 40 is disposed obliquely with respect to the central axis of the cone, the cross section S1 obtained by cutting the reference light L23 (Lref) at the surface of the hologram photosensitive medium 40 is As shown in FIG.

  In this way, in the example shown in FIG. 2, the reference light Lref is irradiated only in the hatched area in the figure of the entire area of the hologram photosensitive medium 40, so that the hologram of the scattering plate 30 has this hatching. It will be recorded only within the given area. Of course, if the collimated light beam L22 having a larger diameter is generated by the beam expander 22 and the convex lens 23 having a larger diameter is used, the hologram photosensitive medium 40 is formed in the cross section S2 of the reference light Lref as shown in FIG. It can also be included exactly. In this case, the hologram of the scattering plate 30 is recorded on the entire surface of the hologram photosensitive medium 40 as hatched in the figure. In creating the hologram recording medium used in the present invention, recording may be performed in any of the forms shown in FIGS.

  Next, let us look at the optical process in which the image of the scattering plate 30 is recorded on the hologram photosensitive medium 40 in more detail. 4 is a partially enlarged view of the periphery of the scattering plate 30 and the hologram photosensitive medium 40 in the optical system shown in FIG. As described above, the reference light Lref is obtained by condensing the parallel light beam L22 having a circular cross section with the convex lens 23 having the focal point C, and converges into a conical shape having the focal point C as an apex. Therefore, hereinafter, this focal point C is referred to as a convergence point. The reference light L23 (Lref) irradiated to the hologram photosensitive medium 40 is light that converges to the convergence point C as shown in the figure.

  On the other hand, since the light (object light Lobj) emitted from the scattering plate 30 is scattered light, it goes in various directions. For example, as illustrated, when an object point Q1 is considered at the upper end of the left side surface of the scattering plate 30, scattered light is emitted in all directions from this object point Q1. Similarly, scattered light is emitted from any object point Q2 or Q3 in all directions. Therefore, focusing on an arbitrary point P1 in the hologram photosensitive medium 40, information on interference fringes between the object lights L31, L32, L33 from the object points Q1, Q2, Q3 and the reference light Lref toward the convergence point C is recorded. Will be. Of course, in reality, the object points on the scattering plate 30 are not limited to Q1, Q2, and Q3, so the information from all the object points on the scattering plate 30 is also the interference fringes with the reference light Lref. Recorded as information. In other words, all information of the scattering plate 30 is recorded at the illustrated point P1. In the same manner, all the information on the scattering plate 30 is recorded at the point P2 shown in the figure. Thus, all the information of the scattering plate 30 is recorded in any part in the hologram photosensitive medium 40. This is the essence of the hologram.

  Now, the hologram photosensitive medium 40 in which the information of the scattering plate 30 is recorded by such a method will be referred to as a hologram recording medium 45 hereinafter. In order to reproduce the hologram recording medium 45 and obtain a hologram reproduction image of the scattering plate 30, the coherent light having the same wavelength as the light used for recording is reproduced from the direction corresponding to the reference light Lref at the time of recording. What is necessary is just to irradiate as illumination light.

  FIG. 5 is a diagram showing a process of reproducing the image 35 of the scattering plate using the hologram recording medium 45 created by the process shown in FIG. As shown in the figure, the hologram recording medium 45 is irradiated with reproduction illumination light Lrep from below. The reproduction illumination light Lrep is coherent light that diverges as a spherical wave from a point light source located at the convergence point C, and a part of the illumination light Lrep irradiates the hologram recording medium 45 while spreading in a conical shape as shown in the figure. . Further, the wavelength of the reproduction illumination light Lrep is equal to the wavelength at the time of recording on the hologram recording medium 45 (that is, the wavelength of the coherent light generated by the coherent light source 10 shown in FIG. 1).

  Here, the positional relationship between the hologram recording medium 45 and the convergence point C shown in FIG. 5 is exactly the same as the positional relationship between the hologram photosensitive medium 40 and the convergence point C shown in FIG. Therefore, the reproduction illumination light Lrep shown in FIG. 5 corresponds to the light traveling backward in the optical path of the reference light Lref shown in FIG. When the hologram recording medium 45 is irradiated with reproduction illumination light Lrep satisfying such conditions, a hologram reproduction image 35 (indicated by a broken line in the figure) of the scattering plate 30 is obtained by the diffracted light L45 (Ldif). The positional relationship between the hologram recording medium 45 and the reproduced image 35 shown in FIG. 5 is exactly the same as the positional relationship between the hologram photosensitive medium 40 and the scattering plate 30 shown in FIG.

  As described above, a technique for recording an image of an arbitrary object as a hologram and reproducing it is a known technique that has been put into practical use for a long time. However, when creating a hologram recording medium used for general purposes, a parallel light beam is used as the reference light Lref. Holograms recorded using the reference light Lref consisting of a parallel light beam are excellent in convenience since the reproduction illumination light Lrep consisting of a parallel light beam may be used even during reproduction.

  On the other hand, as shown in FIG. 4, when the light that converges at the convergence point C is used as the reference light Lref, during reproduction, the light that diverges from the convergence point C is reproduced as shown in FIG. It is necessary to use as. Actually, in order to obtain the reproduction illumination light Lrep as shown in FIG. 5, it is necessary to arrange an optical system such as a lens at a specific position. Further, if the positional relationship between the hologram recording medium 45 and the convergence point C at the time of reproduction does not match the positional relationship between the hologram photosensitive medium 40 and the convergence point C at the time of recording, an accurate reproduced image 35 cannot be obtained. Therefore, the illumination conditions at the time of reproduction are limited (if reproduction is performed using a parallel light beam, the illumination conditions need only satisfy the irradiation angle).

  For these reasons, the hologram recording medium created using the reference light Lref that converges at the convergence point C is not suitable for general applications. Nevertheless, in the embodiment shown here, the reason why the light converged at the convergence point C is used as the reference light Lref is to facilitate the light beam scanning performed during reproduction. That is, in FIG. 5, for convenience of explanation, a method of generating the reproduction image 35 of the scattering plate 30 using the reproduction illumination light Lrep that diverges from the convergence point C is shown. Thus, the reproduction using the reproduction illumination light Lrep spreading in a conical shape is not performed. Instead, a method of scanning the light beam is adopted. Hereinafter, this method will be described in detail.

  FIG. 6 is a diagram showing a process of reproducing the image 35 of the scattering plate 30 by irradiating only one light beam to the hologram recording medium 45 created by the process shown in FIG. That is, in this example, only one light beam L61 directed from the convergence point C to one point P1 in the medium is provided as the reproduction illumination light Lrep. Of course, the light beam L61 is coherent light having the same wavelength as that of the recording light. As already described with reference to FIG. 4, information on the entire scattering plate 30 is recorded at an arbitrary point P <b> 1 in the hologram recording medium 45. Therefore, if the reproduction illumination light Lrep is irradiated on the position of the point P1 in FIG. 6 under the condition corresponding to the reference light Lref used at the time of recording, only the interference fringes recorded in the vicinity of the point P1 are used. Thus, a reproduced image 35 of the scattering plate 30 can be generated. FIG. 6 shows a state in which the reproduced image 35 is reproduced by the diffracted light L45 (Ldif) from the point P1.

  On the other hand, FIG. 7 shows an example in which only one light beam L62 directed from the convergence point C to another point P2 in the medium is given as the reproduction illumination light Lrep. Also in this case, since the information of the entire scattering plate 30 is recorded at the point P2, the reproduction illumination light Lrep is irradiated to the position of the point P2 under the conditions corresponding to the reference light Lref used at the time of recording. For example, it is possible to generate the reproduced image 35 of the scattering plate 30 using only the interference fringes recorded in the vicinity of the point P2. FIG. 7 shows a state in which the reproduced image 35 is reproduced by the diffracted light L45 (Ldif) from the point P2. Since the reproduced image 35 shown in FIG. 6 and the reproduced image 35 shown in FIG. 7 have the same scattering plate 30 as the original image, they are theoretically the same reproduced image generated at the same position. .

  FIG. 8 is a plan view showing the irradiation position of the light beam in the reproduction process shown in FIGS. A point P1 in FIG. 8 corresponds to the point P1 in FIG. 6, and a point P2 in FIG. 8 corresponds to the point P2 in FIG. A1 and A2 respectively indicate cross sections of the reproduction illumination light Lrep. The shapes and sizes of the cross sections A1 and A2 depend on the shapes and sizes of the cross sections of the light beams L61 and L62. Further, it also depends on the irradiation position on the hologram recording medium 45. Here, for the sake of convenience, circular cross sections A1 and A2 are shown, but actually, when the light beams L61 and L62 having a circular cross section are used, the cross sectional shape becomes a flat ellipse according to the irradiation position.

  As described above, the recorded interference fringes are completely different in the vicinity of the point P1 and in the vicinity of the point P2 shown in FIG. 8, but any point is irradiated with the light beam serving as the reproduction illumination light Lrep. Even in this case, the same reproduced image 35 is obtained at the same position. This is because the reproduction illumination light Lrep is a light beam directed from the convergence point C toward each of the points P1 and P2, and at any point, reproduction in a direction corresponding to the direction of the reference light Lref at the time of recording shown in FIG. This is because the illumination light Lrep is provided.

  Although only two points P1 and P2 are illustrated in FIG. 8, the same can be said of an arbitrary point on the hologram recording medium 45. Therefore, when a light beam is irradiated to an arbitrary point on the hologram recording medium 45, the same reproduced image 35 is obtained at the same position as long as the light beam is light from the convergence point C. However, as shown in FIG. 2, when a hologram is recorded only in a partial area of the hologram photosensitive medium 40 (area shown by hatching in the figure), a reproduced image 35 is obtained at a point in the area. Limited to light beam irradiation.

  Eventually, the hologram recording medium 45 described here is a medium in which the image of the scattering plate 30 is recorded as a hologram using the reference light Lref that converges to a specific convergence point C, and the light beam that passes through this convergence point C. Is irradiated as an illumination light Lrep for reproduction at any position, a reproduction image 35 of the scattering plate 30 is generated. Therefore, when the light beam passing through the convergence point C is scanned on the hologram recording medium 45 as the reproduction illumination light Lrep, the same reproduction image 35 is reproduced at the same position by the diffracted light Ldif obtained from each irradiation point. Will be.

<<< §2. Lighting device according to a basic embodiment of the present invention >>
Next, the configuration of the illumination device 100 according to the basic embodiment of the present invention will be described with reference to the side view of FIG. As shown in the figure, the illumination device 100 includes a hologram recording medium 45, a coherent light source 50, and a light beam scanning device 60.

  Here, the hologram recording medium 45 is a medium having the characteristics described in §1, and an image 35 of the scattering plate 30 is recorded thereon. The coherent light source 50 is a light source that generates a coherent light beam L50 having the same wavelength as that of the light (object light Lobj and reference light Lref) used when the hologram recording medium 45 is produced.

  On the other hand, the light beam scanning device 60 irradiates the hologram recording medium 45 with the light beam L50 generated by the coherent light source 50 bent at a predetermined scanning base point B, and changes the bending mode of the light beam L50 with time. By doing so, the apparatus scans so that the irradiation position of the bent light beam L60 on the hologram recording medium 45 changes with time. Such an apparatus is generally known as a scanning mirror device. In the figure, for convenience of explanation, the bending mode at time t1 is indicated by a one-dot chain line, and the bending mode at time t2 is indicated by a two-dot chain line. That is, at the time t1, the light beam L50 is bent at the scanning base point B and irradiated to the point P (t1) of the hologram recording medium 45 as the light beam L60 (t1), but at the time t2, the light beam L50 is scanned. Bending at the base point B and irradiating the point P (t2) of the hologram recording medium 45 as a light beam L60 (t2).

  For the sake of convenience, only the bending modes at two points in time t1 and t2 are shown in the figure, but actually, the bending direction of the light beam changes smoothly during the period from time t1 to time t2, and the light beam L60. The irradiation position with respect to the hologram recording medium 45 gradually moves to points P (t1) to P (t2) in the figure. That is, in the period from time t1 to time t2, the irradiation position of the light beam L60 is scanned on the hologram recording medium 45 to the points P (t1) to P (t2).

  Here, if the position of the scanning base point B coincides with the position of the convergence point C shown in FIG. 4 (in other words, the positional relationship between the hologram recording medium 45 and the scanning base point B in FIG. 4), the light beam L60 is directed in accordance with the reference light Lref shown in FIG. 4 (at each irradiation position of the hologram recording medium 45). In this case, the light beam is irradiated in the direction of reciprocating the optical path of the reference light Lref shown in FIG. Therefore, the light beam L60 functions as correct reproduction illumination light Lrep for reproducing the hologram recorded therein at each irradiation position of the hologram recording medium 45.

  For example, at time t1, a reproduced image 35 of the scattering plate 30 is generated by the diffracted light L45 (t1) from the point P (t1), and at time t2, by the diffracted light L45 (t2) from the point P (t2). A reproduced image 35 of the scattering plate 30 is generated. Of course, also during the period from time t1 to t2, the reproduced image 35 of the scattering plate 30 is similarly generated by the diffracted light from each position irradiated with the light beam L60. In other words, as long as the light beam L60 is directed toward the hologram recording medium 45 from the scanning base point B, the same light beam L60 is irradiated by the diffracted light from the irradiation position regardless of the position on the hologram recording medium 45. Are reproduced at the same position.

  Such a phenomenon occurs, as shown in FIG. 4, in the hologram recording medium 45, an image of the scattering plate 30 is recorded as a hologram using the reference light L23 that converges at a specific convergence point C. This is because the beam scanning device 60 scans the light beam L60 with the convergence point C as the scanning base point B. Of course, even if the scanning by the light beam scanning device 60 is stopped and the irradiation position of the light beam L60 is fixed at one point on the hologram recording medium 45, the same reproduced image 35 is continuously generated at the same position. Absent. Nevertheless, scanning the light beam L60 is none other than to suppress speckle noise.

  FIG. 10 is a side view illustrating a state where the illumination target object 70 is illuminated using the illumination device 100 illustrated in FIG. 9. The illumination device 100 is a device that uses the reproduction light of the image 35 of the scattering plate obtained from the hologram recording medium 45 as illumination light. Here, in order to illuminate the left side surface of the illumination target object 70 with the illumination device 100, as shown in the drawing, the left side surface of the illumination target object 70 coincides with the left side surface of the reproduced image 35 of the scattering plate. Consider the case where the illumination object 70 is arranged. In this case, the left side surface of the illumination object 70 becomes the light receiving surface R, and the diffracted light from the hologram recording medium 45 is irradiated onto the light receiving surface R.

  Accordingly, an arbitrary point of interest Q is set on the light receiving surface R, and the diffracted light reaching the point of interest Q is considered. First, at time t1, the light beam L50 emitted from the coherent light source 50 is bent at the scanning base point B as indicated by the alternate long and short dash line in the figure, and is irradiated to the point P (t1) as the light beam L60 (t1). Then, the diffracted light L45 (t1) from the point P (t1) reaches the point of interest Q. On the other hand, at time t2, the light beam L50 emitted from the coherent light source 50 is bent at the scanning base point B as indicated by a two-dot chain line in the drawing, and is irradiated to the point P (t2) as the light beam L60 (t2). Then, the diffracted light L45 (t2) from the point P (t2) reaches the point of interest Q.

  Eventually, such a diffracted light always generates a reproduced image corresponding to the position of the point of interest Q on the scattering plate 30 at the position of the point of interest Q. The corners are different at time t1 and time t2. In other words, when the light beam L60 is scanned, the reproduced image 35 formed on the light receiving surface R is not changed, but the incident angle of the diffracted light reaching each point on the light receiving surface R changes with time. Will do. Such a change in incident angle with time greatly contributes to reducing speckle.

  As described above, speckles are generated when coherent light is used because the coherent light reflected from each part of the light receiving surface R interferes with each other because of its extremely high coherence. However, in the present invention, since the incident angle of the diffracted light to each part of the light receiving surface R varies with time by scanning with the light beam L60, the mode of interference also varies with time and has multiplicity. . For this reason, speckle generation factors can be mitigated from the fact that speckled patterns that disperse in time and have physiological adverse effects are constantly observed. This is the basic principle of the present invention.

  FIG. 11 is a side view showing an example in which the lighting device 100 shown in FIG. 9 is used for room lighting. As shown in the figure, a table 75 and chairs 76 and 77 are arranged on the floor surface 200 in the room, and the upper surface of the table 75 (in this example, the surface of the table cloth) serves as an illumination object to form a light receiving surface R. doing. The illumination device 100 is attached to the ceiling 210 as illustrated. In the figure, for convenience, the illumination device 100 is drawn to be approximately the same size as the table 75. However, in practice, a semiconductor laser is used as the coherent light source 50, and a scanning mirror device is used as the light beam scanning device 60. The size can be reduced to the same level as a general lighting device for indoor lighting.

  If, for example, a green laser light source is used as the coherent light source 50, the upper surface (light receiving surface R) of the table 75 is illuminated with a green illumination spot. Such illumination using coherent light is different from conventional general indoor illumination, and has an extremely innovative illumination effect for the observer. That is, the light receiving surface R is illuminated with a very bright green color due to the monochromaticity of the laser beam. Further, an illumination spot having a clear contour can be formed by the directivity of the laser beam. Actually, the contour of the illumination spot formed on the light receiving surface R becomes the contour of the reproduced image 35. Therefore, if the light receiving surface R is arranged at the reproduction position of the reproduced image 35, a clear reproduced image of the scattering plate 30 is obtained. It is formed on the light receiving surface R. Furthermore, since the laser light source generally has high light conversion efficiency, illumination with high luminance can be achieved with low power consumption.

  Thus, according to the present invention, monochromatic surface illumination with extremely high color purity is possible. Moreover, in the illumination device according to the present invention, as described above, since the incident angles of the light applied to each part of the light receiving surface R are temporally multiplexed, the generation of speckle is suppressed. Therefore, glaring spot-like noise as seen with illumination by a laser pointer is reduced, and physiological discomfort is not given to humans. Thus, it is possible to realize a lighting device that can be used for indoor lighting.

  In addition, although the example which has arrange | positioned the illumination target object (upper surface of the table 75) in the position where the reproduction | regeneration image 35 of the scattering plate 30 is produced | generated was shown in FIG. 11, when utilizing as an illuminating device, The position is not particularly limited. That is, in the case of the example shown in FIG. 11, the reproduced image 35 of the scattering plate 30 is generated on the upper surface (light receiving surface R) of the table 75, so the light receiving surface R functions as a screen for displaying the reproduced image 35. As described above, an illumination spot having a clear contour is formed on the light receiving surface R. However, if it is used as a simple illumination device, it is not always necessary to form an illumination spot having a sharp outline.

  For example, in the arrangement shown in FIG. 11, when the table 75 is removed, the diffracted light from the hologram recording medium 45 is irradiated onto the floor surface 200. Even in this case, since the generation position of the reproduction image 35 is not changed, the reproduction image 35 cannot be seen by human eyes (since there is no object that scatters light at the position of the reproduction image 35, human The reproduced image 35 is not formed in the eyes. Still, the diffracted light reaching the floor surface 200 is scattered by the floor surface 200 and reaches the human eye, so that the lighting device 100 can perform an illumination function for the floor surface 200.

  Of course, it is also possible to adopt an illumination method that intentionally removes the position of the light receiving surface R from the generation position of the reproduced image 35. For example, if a table slightly lower than the table 75 shown in FIG. 11 is disposed, a reproduced image 35 slightly out of focus is formed on the upper surface of the table. However, for the purpose of illuminating the upper surface of the table, it may be preferable to form a defocused reproduced image 35 because a soft illumination effect can be obtained. As described above, when the illumination device according to the present invention is used, the position of the illumination object is a matter that should be appropriately determined according to preference, and is not particularly limited.

<<< §3. Detailed explanation of each part of lighting device >>>
The illumination device 100 shown in FIG. 9 includes the hologram recording medium 45, the coherent light source 50, and the light beam scanning device 60 as described in §2. Here, these components will be described in more detail.

<3-1> Coherent Light Source First, as the coherent light source 50, a coherent light beam L50 having the same wavelength as the light (object light Lobj and reference light Lref) used when the hologram recording medium 45 is produced is generated. The light source to be used may be used. However, the wavelength of the light beam L50 generated by the coherent light source 50 does not have to be exactly the same as the wavelength of the light used when the hologram recording medium 45 is produced. Can be obtained. In short, the coherent light source 50 used in the present invention may be a light source that generates a coherent light beam L50 having a wavelength capable of reproducing the image 35 of the scattering plate.

  Actually, the same light source as the coherent light source 10 shown in FIG. 5 can be used as the coherent light source 50 as it is. In the case of the embodiment shown here, a DPSS (Diode Pumped Solid State) laser device capable of emitting laser light having a wavelength λ = 532 nm (green) is used as the coherent light source 50. The DPSS laser is a coherent light source suitable for use in the illumination device according to the present invention because it can obtain a laser beam having a desired wavelength with a relatively high output while being small.

  Since this DPSS laser device has a longer coherence length than a general semiconductor laser, speckles are likely to occur, and it has been conventionally considered inappropriate for illumination applications. That is, conventionally, in order to reduce speckle, efforts have been made to increase the oscillation wavelength of laser light and shorten the coherent length as much as possible. On the other hand, in the present invention, even if a light source having a long coherent length is used, the generation of speckle can be effectively suppressed by the above-described principle, so even if a DPSS laser device is used as the light source. In practice, the generation of speckle is no longer a problem. In such a point, if the present invention is used, an effect of further expanding the selection range of the light source can be obtained.

<3-2> Light Beam Scanning Device The light beam scanning device 60 is a device having a function of scanning a light beam on the hologram recording medium 45. Here, a specific method of beam scanning by the light beam scanning device 60 will be described. FIG. 12 is a plan view showing a first example of the scanning mode of the light beam on the hologram recording medium 45 in the illumination device 100 shown in FIG. In this example, a medium having a horizontal width Da = 12 mm and a vertical width Db = 10 mm is used as the hologram recording medium 45, and a laser beam having a circular cross section with a diameter of 1 mm is used as the light beam L60 that scans the medium. . As shown, the irradiation position of the light beam L60 is scanned in the horizontal direction from the start area A1S to the end area A1E in the first row, and then the start of the second line is performed, as in the electron beam scanning in the CRT. Scan from the area A2S to the end area A2E in the horizontal direction, and finally, scan from the start area AnS of the nth row to the end area AnE in the horizontal direction, and again to the start area A1S of the first line. The method of returning and repeating the same work is adopted.

  In the scanning method shown in FIG. 12, the entire surface of the hologram recording medium 45 is scanned by the light beam. However, in the present invention, it is not always necessary to scan the entire surface of the hologram recording medium 45 without omission. For example, FIG. 13 shows an example in which only the odd-numbered rows in the scanning method shown in FIG. 12 are scanned and the even-numbered rows are omitted. As described above, when scanning is performed every other line, the hologram information recorded in a partial area of the hologram recording medium 45 does not contribute to the reproduction of the image at all. Absent. FIG. 14 shows an example of a more extreme scanning method, in which the operation of scanning only one line in the horizontal direction from the start area A1S to the end area A1E is repeated at the center position of the vertical width Db.

  Of course, the setting of the scanning direction is also arbitrary, and the scanning of the first row may be performed from left to right and then the scanning of the second row may be performed from right to left. Further, the scanning direction is not necessarily limited to a straight line, and it is also possible to perform scanning that draws a circle on the hologram recording medium 45.

  As shown in the example of FIG. 2, when recording is performed by irradiating only a partial area (hatched area) of the hologram photosensitive medium 40 with the reference light Lref, the other area (the white area outside) is recorded. No area is recorded with a hologram. In such a case, if the outer white area is scanned, the reproduced image 35 cannot be obtained, and the illumination temporarily becomes dark. Therefore, in practice, it is preferable to scan only the area where the hologram is recorded.

  As already described, the light beam scanning on the hologram recording medium 45 is performed by the light beam scanning device 60. This light beam scanning device 60 has a function of irradiating the hologram recording medium 45 with the light beam L50 from the coherent light source 50 bent at the scanning base point B (convergence point C at the time of hologram recording). In addition, scanning is performed so that the irradiation position of the bent light beam L60 on the hologram recording medium 45 changes with time by changing the bending mode (the direction of bending and the size of the bending angle) with time. An apparatus having such a function is used in various optical systems as a scanning mirror device.

  For example, in the example shown in FIG. 9, as a light beam scanning device 60, a simple reflecting mirror is drawn for the sake of convenience, but actually, a driving mechanism that rotates the reflecting mirror in two axial directions is provided. Yes. That is, when the scanning base point B is set at the center position of the reflecting surface of the reflecting mirror shown in the figure, and the V axis and the W axis that pass through the scanning base point B and are orthogonal to each other on the reflecting surface are defined, A mechanism for rotating around an axis (axis perpendicular to the paper surface in the figure) and a mechanism for rotating around a W axis (axis indicated by a broken line in the figure) are provided.

  In this way, by using a reflecting mirror that can be rotated independently about the V-axis and the W-axis, the reflected light beam L60 can be scanned on the hologram recording medium 45 in the horizontal and vertical directions. . For example, in the above-described mechanism, if the reflected light is rotated around the V axis, the irradiation position of the light beam L60 can be scanned in the horizontal direction on the hologram recording medium 45 shown in FIG. If it moves, it can scan in the vertical direction.

  In short, if the light beam scanning device 60 has a function of bending the light beam L60 so as to perform a swinging motion on a plane including the scanning base point B, the irradiation position of the light beam L60 on the hologram recording medium 45 Can be scanned in a one-dimensional direction. As in the example shown in FIG. 14, if the operation of scanning the light beam only in the horizontal direction is performed, the light beam scanning device 60 sets the irradiation position of the light beam on the hologram recording medium 45 in the one-dimensional direction. It is sufficient to have a scanning function.

  On the other hand, if the operation of scanning the irradiation position of the light beam L60 in the two-dimensional direction on the hologram recording medium 45 is performed, the light beam scanning device 60 is swung on the first plane including the scanning base point B. A function of bending the light beam L60 so as to perform a dynamic motion (in FIG. 9, if the reflecting mirror is rotated around the V axis, the light beam L60 performs a rocking motion on a plane included in the paper surface) And a function of bending the light beam L60 so as to perform a swinging motion on a second plane that includes the scanning base point B and is orthogonal to the first plane (in FIG. 9, the reflecting mirror can be rotated around the W axis). For example, the light beam L60 may perform a rocking motion on a plane perpendicular to the paper surface).

  A polygon mirror is widely used as a scanning mirror device for scanning the irradiation position of a light beam in a one-dimensional direction. As a scanning mirror device for scanning in a two-dimensional direction, a combination of two polygon mirrors can be used, and devices such as a gimbal mirror, a galvano mirror, and a MEMS mirror are known. In addition to a normal mirror device, a total reflection prism, a refraction prism, an electro-optic crystal (such as a KTN crystal), and the like can be used as the light beam scanning device 60.

  Note that when the diameter of the light beam L60 is close to the dimension of the hologram recording medium 45, the effect of suppressing speckles may be impaired. In the example shown in FIGS. 12 to 14, as described above, the hologram recording medium 45 has a horizontal width of Da = 12 mm, a vertical width of Db = 10 mm, and the light beam L60 is a laser beam having a circular cross section with a diameter of 1 mm. is there. With such dimensional conditions, the effect of suppressing speckles can be sufficiently obtained. This is because any region on the hologram recording medium 45 is only temporarily irradiated with the light beam L60, and diffracted light does not continue to be emitted from the same region.

  However, for example, as shown in the example shown in FIG. 15, when a light beam having a diameter close to the dimension of the hologram recording medium 45 is irradiated, a region (hatched portion in the figure) that continuously emits diffracted light is formed. Will be. That is, even if the irradiation position of the light beam L60 is scanned in the horizontal direction from the start area A1S to the end area A1E in the first row, the hatched area a1 is always irradiated with the light beam. Become. Similarly, even when scanning from the start area AnS to the end area AnE in the nth row in the horizontal direction, the area a2 is always irradiated with a light beam. Further, considering vertical scanning, the region a3 is overlapped with respect to the start region of each row and the region a4 is overlapped with respect to the end region of each row. Will receive irradiation.

  Eventually, these hatched areas cannot receive the benefits of light beam scanning, and diffracted light continues to be emitted. As a result, diffracted light emitted from such a region continues to be incident on the light receiving surface R of the illumination object at the same angle, which causes speckle generation. Therefore, the diameter of the light beam L60 should not be increased as it approaches the dimension of the hologram recording medium 45.

  Such an adverse effect also occurs when the scanning pitch is set smaller than the diameter of the light beam L60. For example, FIG. 12 is an example in which the vertical scanning pitch is set equal to the diameter of the light beam L60, and FIG. 13 is an example in which the vertical scanning pitch is set to twice the diameter of the light beam L60. Thus, if the scanning pitch in the vertical direction (sub-scanning direction) is set to be equal to or larger than the diameter of the light beam, the i-th scanning region and the (i + 1) -th scanning region overlap. However, if the scanning pitch is less than the diameter of the light beam, an overlapping region is generated, which may cause speckles as described above.

  Also, a slow scanning speed becomes a factor of speckle generation. For example, even if scanning is performed at such a slow speed that one hour is required for scanning one line, from the viewpoint of human visual time resolution, it is the same as not performing scanning, and speckle is recognized. It will be. The reason that speckle is reduced by scanning the light beam is that, as described above, the incident angles of the light applied to each part of the light receiving surface R are multiplexed in time. Therefore, in order to sufficiently obtain the effect of speckle reduction by beam scanning, the time during which the same interference condition that causes speckle is maintained is shorter than human visual time resolution. do it.

  In general, the limit of human visual temporal resolution is about 1/20 to 1/30 seconds, and if a still image of 20 to 30 frames or more is presented per second, a smooth video is displayed to humans. Be recognized. In consideration of such points, if the diameter of the light beam is d, scanning is performed at a scanning speed (speed of 20 d to 30 d per second) that travels a distance of d or more in 1/20 to 1/30 seconds. A sufficient speckle suppressing effect can be obtained.

<3-3> Hologram recording medium The hologram recording medium 45 has already been described in detail in §1. That is, the hologram recording medium 45 used in the present invention may be a medium having a feature that the image of the scattering plate 30 is recorded as a hologram using reference light that converges at a specific convergence point C. . Therefore, a specific form of a hologram recording medium suitable for use in the present invention will be described here.

  There are several physical forms of holograms. The inventor of the present application considers that a volume hologram is most preferable for use in the present invention. In particular, it is optimal to use a volume hologram using a photopolymer.

  In general, a hologram used as an anti-counterfeit seal for a cash card or a cash voucher is called a surface relief (emboss) type hologram, and hologram interference fringes are recorded by a concavo-convex structure on the surface. Of course, in carrying out the present invention, it is also possible to use a hologram recording medium 45 (generally called a holographic diffuser) in which an image of the scattering plate 30 is recorded as a surface relief hologram. is there. However, in the case of this surface relief hologram, scattering due to the uneven structure on the surface may become a new speckle generation factor, which is not preferable from the viewpoint of reducing speckle. Further, in the surface relief type hologram, since multi-order diffracted light is generated, the diffraction efficiency is lowered, and further, there is a limit to the diffraction performance (how much the diffraction angle can be increased).

  On the other hand, in the volume hologram, since hologram interference fringes are recorded as a refractive index distribution inside the medium, it is not affected by scattering due to the uneven structure on the surface. In general, the diffraction efficiency and the diffraction performance are also superior to the surface relief hologram. Therefore, when carrying out the present invention, it is optimal to use a medium in which the image of the scattering plate 30 is recorded as a volume hologram as the hologram recording medium 45.

  However, volume holograms that are recorded using a photosensitive medium containing a silver salt material are preferably avoided because scattering by silver salt particles may cause new speckle generation. . For these reasons, the present inventor believes that a volume hologram using a photopolymer is optimal as the hologram recording medium 45 used in the present invention. A specific chemical composition of a volume hologram using such a photopolymer is exemplified in, for example, Japanese Patent No. 2849021.

  However, the surface relief type hologram is superior to the volume type hologram in terms of mass productivity. The surface relief hologram can be mass-produced by producing an original plate having a concavo-convex structure on the surface and press working using the original plate. Therefore, when it is necessary to reduce the manufacturing cost, a surface relief hologram may be used.

  As a physical form of the hologram, an amplitude modulation type hologram in which interference fringes are recorded as a light and shade pattern on a plane is also widely used. However, since this amplitude modulation hologram has low diffraction efficiency and light is absorbed in a dark pattern portion, sufficient illumination efficiency cannot be secured when used in the present invention. However, in the manufacturing process, since a simple method of printing a shading pattern on a flat surface can be adopted, a merit can be obtained in terms of manufacturing cost. Therefore, depending on the application, it is also possible to employ an amplitude modulation hologram in the present invention.

  In the recording method shown in FIG. 1, a so-called Fresnel type hologram recording medium is produced, but even if a Fourier transform type hologram recording medium obtained by recording the scattering plate 30 through a lens is produced. It doesn't matter. In this case, if necessary, a lens may be provided on the optical path of the diffracted light L45 to condense it to improve the illumination efficiency. However, the function as an illumination device can be sufficiently achieved without a lens. Can do.

<<< §4. Modified example of lighting device according to the present invention >>
So far, the basic embodiment of the illumination device according to the present invention has been described. When implementing this basic embodiment, first, a preparatory stage for creating the hologram recording medium 45 is performed by recording the image 35 of the scattering plate 30 on the recording medium 40 as a hologram. The illumination device 100 is configured using the hologram recording medium 45, the coherent light beam L60 is irradiated onto the hologram recording medium 45, and the light beam L60 is applied to the hologram recording medium 45 so that the irradiation position changes with time. The illumination stage scanning above will be performed.

  In this case, in the preparation stage, as shown in FIG. 1, the coherent illumination light L12 is irradiated onto the scattering plate 30, and the scattered light L30 obtained from the scattering plate 30 is used as the object light Lobj. Further, the recording medium 40 is irradiated along the predetermined optical path, and the coherent light L23 having the same wavelength as the illumination light L12 is used as the reference light Lref. Then, the hologram recording medium 45 is created by recording the interference fringes formed by the object light Lobj and the reference light Lref on the recording medium 40. In the illumination stage, as shown in FIG. 9, a light beam L60 having the same wavelength as the reference light Lref (or an approximate wavelength capable of reproducing the hologram) passes through an optical path along the optical path of the reference light Lref. The scattering plate 30 is obtained from the hologram recording medium 45 by scanning toward the irradiation position on the recording medium 45 (in other words, applying the light beam L60 from a direction optically conjugate with the reference light Lref). The reproduction light of the image 35 is used as illumination light.

  Here, some modifications to the basic embodiment described above will be described.

<4-1> Hologram Recording Medium Premised on One-Dimensional Scanning In the hologram recording medium production process shown in FIG. 1, the parallel light beam L22 is condensed by a convex lens 23 (a lens having a focal point at the convergence point C). The medium 40 is irradiated as the reference light Lref. That is, scattering is performed using the reference light Lref that converges three-dimensionally to the convergence point C along the side surface of the cone having the convergence point C as a vertex (theoretically, cones having different radii exist infinitely). An image of the plate 30 will be recorded.

  The reference light Lref that converges three-dimensionally is used in the illumination device shown in FIG. This is because it is assumed that the beam is scanned in combination (the beam is scanned by combining the rotation of the reflecting mirror around the V axis and the rotation around the W axis). The reason why the light beam L60 is scanned three-dimensionally is that the irradiation position of the light beam on the hologram recording medium 45 is two-dimensionally scanned (in FIG. 12, horizontal scanning and vertical scanning are performed). To do).

  However, the scanning of the irradiation position of the light beam on the hologram recording medium 45 is not necessarily performed two-dimensionally. For example, FIG. 14 shows an example in which the light beam is scanned only in the horizontal direction. As described above, if it is assumed that the irradiation position of the light beam is scanned one-dimensionally, it is more reasonable to prepare the hologram recording medium on such a premise. Specifically, if one-dimensional scanning is assumed, it is sufficient to create a strip-shaped hologram recording medium 85 as shown in FIG. 16 instead of creating the hologram recording medium 45 as shown in FIG.

  When this hologram recording medium 85 is used, the scanning by the light beam scanning device 60 may be repeated for one line from the leftmost starting point area A1S to the rightmost end point area A1E. In this case, scanning for one line from left to right may be repeated, or after scanning from left to right, a reciprocating motion such as scanning from right to left may be performed. When the light beam L60 to be used is a laser beam having a circular cross section having a diameter of 1 mm, it is sufficient that the vertical width of the hologram recording medium 85 shown in FIG. 16 is Db = 1 mm. Therefore, space can be saved as compared with the case where the hologram recording medium 45 shown in FIG. 14 is used, and the entire apparatus can be downsized.

  The hologram recording medium 85 on the premise of such one-dimensional scanning can be created by using the optical system shown in FIG. 1, but instead by using the optical system shown in FIG. Is also possible. In the optical system shown in FIG. 17, the convex lens 23 in the optical system shown in FIG. 1 is replaced with a cylindrical lens 24, and the hologram photosensitive medium 40 having a rectangular plane is changed to a hologram photosensitive medium 80 having an elongated belt-like plane. It has been replaced and other components remain unchanged. The horizontal width Da of the hologram photosensitive medium 80 is the same as the horizontal width of the hologram photosensitive medium 40, but the vertical width Db (in FIG. 17, the width in the direction perpendicular to the paper surface) is about the diameter of the light beam (in the case of the above example). 1 mm).

  The cylindrical lens 24 is a lens having a cylindrical surface having a central axis perpendicular to the paper surface of FIG. 17, and in FIG. 17, when a condensing axis passing through the convergence point C and perpendicular to the paper surface is defined, the parallel light beam L22. Fulfills the function of condensing the light on the light collecting axis. However, due to the nature of the cylindrical lens, light refraction occurs only in a plane parallel to the paper surface and does not occur in a direction perpendicular to the paper surface. In other words, if attention is paid to a plane including the convergence point C and orthogonal to the central axis of the cylindrical lens cylinder (the paper surface of FIG. 17), the light L24 that converges two-dimensionally along the plane is referred to as the reference light It will be given as Lref.

  As described above, when “the light converges at the convergence point C” in the present application, not only the three-dimensional convergence by the convex lens 23 shown in the optical system of FIG. 1 but also the cylindrical lens 24 shown in the optical system of FIG. It also means two-dimensional convergence by. Then, when creating a hologram recording medium 85 based on one-dimensional scanning as exemplified in FIG. 16, as shown in the optical system of FIG. 17, a predetermined condensing axis (example in the figure) passing through the convergence point C is shown. In this case, a cylindrical lens 24 having a cylindrical surface having a central axis parallel to the convergence point C and an axis perpendicular to the paper surface is used to collect a substantially parallel coherent light beam L22 on the condensing axis. The hologram image of the scattering plate 30 may be recorded using the light L24 that converges two-dimensionally at the convergence point C as the reference light Lref.

<4-2> Hologram recording medium made of CGH The hologram recording medium production process described so far involves actually irradiating the hologram photosensitive medium with light and fixing the interference fringes generated there by the chemical change of the photosensitive medium. It takes a purely optical method. On the other hand, recently, there is a method of simulating such an optical process on a computer, calculating interference fringe information by calculation, and fixing the result on a medium by some physical method. Established. A hologram created by such a method is generally called a computer generated hologram (CGH).

  The hologram recorded on the hologram recording medium used in the present invention may be such a computer-generated hologram. That is, instead of creating a hologram recording medium by the optical process described in §1, a simulation calculation using virtual object light and virtual reference light from a virtual scattering plate is performed, and a virtual recording surface is displayed. What is necessary is just to obtain information on the interference fringes generated in the above, and record this information on the medium by a physical method to create a computer-generated hologram.

  FIG. 18 is a side view showing the principle of creating a hologram recording medium, which is a component of the illumination apparatus according to the present invention, by the CGH method, and simulates the optical phenomenon shown in FIG. 4 on a computer. The method is shown. 18 corresponds to the actual scattering plate 30 shown in FIG. 4, and the virtual recording surface 40 ′ shown in FIG. 18 corresponds to the actual hologram photosensitive medium 40 shown in FIG. Corresponding to The illustrated object light Lobj is virtual light emitted from the virtual scattering plate 30 ', and the illustrated reference light Lref is virtual light having the same wavelength as the object light Lobj. The point that the reference light Lref is light that converges at the convergence point C is exactly the same as the method described so far. At each point on the recording surface 40 ', information on interference fringes between the virtual object light Lobj and the reference light Lref is calculated.

  As the virtual scattering plate 30 ', for example, a fine three-dimensional model represented by polygons or the like can be used. Here, however, a large number of point light sources D are arranged in a grid on a plane. A simple model is used. FIG. 19 is a front view of the virtual scattering plate 30 ′ shown in FIG. 18, and small white circles indicate the point light sources D, respectively. As shown in the figure, a large number of point light sources D are arranged in a grid pattern with a horizontal pitch Pa and a vertical pitch Pb. The pitches Pa and Pb are parameters that determine the surface roughness of the scattering plate.

  The inventor of the present application calculates the information of interference fringes generated on the recording surface 40 ′ by setting the pitches Pa and Pb of the point light sources D to about 10 μm, respectively. A pattern was formed to produce a surface relief type CGH. And when the illuminating device 100 which used this CGH as the hologram recording medium 45 was comprised, the favorable illumination environment which suppressed the speckle was obtained.

  FIG. 20 is a table showing experimental results obtained by the speckle reduction effect according to the present invention. In general, a method has been proposed in which a numerical value called speckle contrast (unit%) is used as a parameter indicating the degree of speckle generated on the light receiving surface. The speckle contrast is an amount defined as a value obtained by dividing the standard deviation of the actually occurring luminance variation by the average luminance value under the condition that a uniform luminance distribution should be originally obtained. The larger the speckle contrast value is, the greater the degree of speckle generation on the light-receiving surface is, and the spotted luminance unevenness pattern is more prominently presented to the observer. .

  The table in FIG. 20 shows the speckle contrast on the light receiving surface R for four types of measurement systems that illuminate the illumination object 70 using the illumination device 100 shown in FIG. 10 or a conventional device for comparison. The measurement results are shown. Measurement examples 1 to 3 are all results of using the same DPSS laser apparatus capable of emitting green laser light as the coherent light source 50. The diffusion angle of the hologram recording medium used in Measurement Examples 2 and 3 (the maximum angle at which the reproduced image 35 is desired from a point on the hologram recording medium) is set to 20 ° in any case.

  First, instead of using the illumination device 100, the measurement result shown as measurement example 1 is that the light beam L50 from the coherent light source 50 is spread by a beam expander to be a parallel light beam, and this parallel light beam (laser parallel light) is directly received by the light receiving surface R. It is the result obtained using the measuring system which irradiates to. In this case, as shown in the table, a result of speckle contrast of 20.1% was obtained. This is a state in which a spot-like luminance unevenness pattern can be observed quite remarkably when observed with the naked eye, and is not suitable for practical indoor lighting.

  On the other hand, the measurement results shown as measurement examples 2 and 3 are the results of illumination using the illumination device 100 shown in FIG. Here, measurement example 2 is the result of using a volume hologram produced by an optical method as hologram recording medium 45, and measurement example 3 is the above-described surface relief type CGH as hologram recording medium 45. It is a result of using it. In all cases, speckle contrast of less than 4% was obtained, which is a very good state in which uneven brightness patterns are hardly observable with the naked eye (generally, speckle contrast value is 5% or less). It is said that there will be no discomfort for the observer). Therefore, a practically sufficient illumination device can be configured both when a volume hologram created by an optical method is used as the hologram recording medium 45 and when a surface relief type CGH is used. The reason why the result of measurement example 2 (3.0%) is better than the result of measurement example 3 (3.7%) is that the resolution of the actual scattering plate 30 that is the original image is a virtual scattering plate. This is considered to be because the resolution is higher than 30 '(a collection of point light sources shown in FIG. 19).

  The measurement result shown as the last measurement example 4 is a result obtained using a measurement system that directly irradiates the light receiving surface R with light from the green LED light source instead of using the illumination device 100. In the first place, since the LED light source is not a coherent light source, it is not necessary to consider the problem of speckle generation. As shown in the table, a good result of speckle contrast of 4.0% was obtained. The reason why the result of Measurement Example 4 using non-coherent light is inferior to the results of Measurement Examples 2 and 3 using coherent light is considered to be due to uneven brightness in the light emitted from the LED light source.

<4-3> Illumination of multiple colors The embodiments described so far are all examples of a monochromatic illumination device using a monochromatic laser light source as a coherent light source, and generate laser beams having different wavelengths. If a plurality of laser light sources are used, it is possible to configure an illuminating device capable of illumination by combining a plurality of colors.

  Specifically, in the illumination device 100 shown in FIG. 9, as the coherent light source 50, a plurality of n laser light sources that generate monochromatic light laser beams having different wavelengths and the n laser light sources are generated. A device having a light combiner that combines laser beams to generate a combined light beam may be used. Of course, on the hologram recording medium 45, the images 35 of the scattering plate 30 are recorded as n holograms in advance so that reproduced images can be obtained by the respective laser beams generated by the n laser light sources. To do.

  FIG. 21 is a block diagram showing an example of such an apparatus. This apparatus has a function of generating a white light beam by combining three primary colors of red, green, and blue. That is, the red laser beam L (R) generated by the red laser light source 50R and the green laser beam L (G) generated by the green laser light source 50G are synthesized by the dichroic prism 15, and further the blue laser light source 50B is generated. By synthesizing the blue laser beam L (B) to be generated by the dichroic prism 16, a white combined light beam L (R, G, B) can be generated. On the other hand, the light beam scanning device 60 may scan the hologram recording medium 45 by bending the combined light beam L (R, G, B) thus generated. From the hologram recording medium 45, diffracted light is obtained for each of the R, G, and B color components, and a reproduced image 35 for each of the R, G, and B color components is generated at the same position. An image is obtained.

  In order to create a hologram recording medium on which an image of the scattering plate 30 is recorded using light of three colors R, G, and B, for example, a dye sensitive to R light and a light sensitive to G light are used. A hologram recording medium using a hologram photosensitive medium in which a dye to be dyed and a dye sensitive to B-color light are uniformly distributed and the above-described combined light beam L (R, G, B) may be used. Further, a hologram photosensitive film having a three-layer structure in which a first photosensitive layer that is sensitive to R light, a second photosensitive layer that is sensitive to G light, and a third photosensitive layer that is sensitive to B light is laminated. A medium may be used. Alternatively, the above three photosensitive layers are prepared as separate media, respectively, and hologram recording is performed separately using light of the corresponding colors, and finally, the three layers are bonded to form a three-layer structure. You may comprise the hologram recording medium which has.

<4-4> Image Display Device So far, the embodiment in which the present invention is used as a lighting device has been described. However, the lighting device according to the present invention can also be used as an image display device. For example, FIG. 11 illustrates a usage form in which the upper surface of the table 75 is illuminated by the illumination device 100 installed on the ceiling. In this case, a reproduced image 35 of the scattering plate 30 is formed on the light receiving surface R, and an illumination spot is formed by the reproduced image 35.

  As described above, when the illumination device 100 is regarded as a device that generates the reproduced image 35 of the scattering plate 30, it is understood that the device has a function as an image display device. For example, when a rectangular plate is used as the scattering plate 30 to be recorded in the preparation stage, the outline of the illumination spot formed on the upper surface of the table 75 is rectangular. However, when a circular plate is used, the outline of the illumination spot is used. Becomes circular. Therefore, for example, as shown in FIG. 22, if a hologram recording medium 45 is created using a scattering plate 30A having a star-shaped outline or a scattering plate 30B having a heart-shaped outline, a star-shaped or heart-shaped outline shape can be obtained. A light spot with light will be obtained. This means that the illumination device 100 functions as an image display device that displays a star-shaped image or a heart-shaped image.

  By the way, the form of the image to be displayed is not determined solely by the contour shape of the scattering plate. For example, a general rectangular scattering plate 30 is prepared as shown in the upper part of FIG. 23, and a transmission film 33A on which a star-shaped image is drawn is prepared as shown in the lower part of the lower part of FIG. The transmission film 33A has a property that the inside of the star shape transmits light, but the outside of the star shape (hatched area) shields light. When such a transmission film 33A is overlaid on the upper surface of the scattering plate 30 and recording is performed using the optical system shown in FIG. 1, the contour shape shown in FIG. Similarly, since a star-shaped scattering plate is recorded, a star-shaped illumination spot is obtained during reproduction.

  Of course, as shown in the lower center of FIG. 23, if a transmission film 33B on which a character string “PAT” is drawn is used, an illumination spot having the shape of each character can be obtained. In the case of the usage form shown in FIG. 11, the character string “PAT” is raised on the upper surface of the table 75. Further, as shown in the lower right of FIG. 23, if a transparent film 33C printed with a gradation image (for example, a monochrome photograph) having light and shade information is used, the gradation image may be displayed on the upper surface of the table 75. it can.

  Thus, when using as an image display apparatus, in order to perform a clear image display, it is necessary to arrange | position the light-receiving surface R in the production | generation position of the reproduced image 35. FIG. Therefore, in order to configure an image display device capable of displaying an image as shown in the lower part of FIG. 23, the illumination device 100 described above and the light receiving surface R that receives illumination by the illumination device 100 are provided. The display medium 70 is prepared. On the hologram recording medium 45, an image 35 of the scattering plate 30 covered with a transmission film on which a predetermined image is drawn is recorded, and the light receiving surface R is set as the scattering plate 30. What is necessary is just to take the structure arrange | positioned in the position where the reproduced image 35 of this is formed.

<4-5> Geometric Variation of Hologram Recording Medium Creation In §1, the method of recording the hologram image of the scattering plate 30 on the hologram photosensitive medium 40 has been described with reference to FIG. This method is a method of creating a reflection type hologram recording medium using reference light that converges at a convergence point C, and the geometrical arrangement of necessary components is as shown in the side view of FIG. .

  In the case of the example shown in FIG. 24, the convergent reference light Lref toward the convergence point C is generated by the convex lens 23, and the medium 40 is disposed between the convex lens 23 and the convergence point C. Further, the medium 40 is disposed obliquely as shown in the figure, and the object light Lobj from the scattering plate 30 is irradiated on the lower surface side thereof. The hologram recording medium produced by such a method is a reflective medium. That is, at the time of reproduction, as shown in FIG. 25, a light beam that functions as reproduction illumination light Lrep is irradiated on the lower surface side of the medium 45, and a reproduced image 35 is generated by the reflected diffracted light Ldif from the point P. Become.

  As described above, the example described so far is an example in which the hologram recorded on the hologram recording medium 45 is a reflection hologram, and the reflected diffraction light of the light beam is used as illumination light. On the other hand, the hologram recorded on the hologram recording medium 45 may be a transmission hologram, and transmission diffraction light of a light beam may be used as illumination light.

  FIG. 26 is a side view showing a geometrical arrangement in producing such a transmission hologram. The difference from the arrangement shown in FIG. 24 is the direction of the medium 40. In the reflection hologram creating method shown in FIG. 24, the reference light Lref is irradiated from the upper surface of the medium, and the object light Lobj is irradiated from the lower surface of the medium. In this way, a reflection hologram can be recorded by irradiating the opposite surface with the reference light and the object light. On the other hand, in the method shown in FIG. 26, both the reference light Lref and the object light Lobj are irradiated on the upper surface of the medium 40. As described above, when the reference light and the object light are irradiated from the same side, a transmission hologram can be recorded. That is, at the time of reproduction, as shown in FIG. 27, a light beam that functions as reproduction illumination light Lrep is irradiated to the lower surface side of the medium 45, and a reproduced image 35 is generated by the transmitted diffracted light Ldif from the point P. Become.

  In addition, the examples described so far are all methods of creating a reflection type or transmission type hologram recording medium using reference light that converges at the convergence point C. Instead, the light diverges from the convergence point C. It is also possible to create a reflection type or transmission type hologram recording medium using reference light. However, for that purpose, it is necessary to prepare a hologram recording medium for preparation in advance. The process for performing this method will be described below in order.

  First, as shown in FIG. 28, the preparatory hologram photosensitive medium 90 and the scattering plate 30 are disposed, and the medium 90 is irradiated with parallel reference light Lref obliquely from the upper right as illustrated. Then, interference fringes generated by the object light Lobj and the reference light Lref from the scattering plate 30 are recorded on the medium 90. In this way, when the object light and the reference light are irradiated from the same side during recording, a transmission hologram is recorded. Here, the medium 90 on which such recording is performed is referred to as a preparation hologram recording medium 95.

  FIG. 29 is a side view showing a reproduction process of the preparation hologram recording medium 95. As shown in FIG. As shown in the figure, when the reproducing illumination light Lrep parallel to the obliquely lower left is irradiated onto the medium 95, a reproduced image 35 is generated on the right side of the figure by the transmitted diffracted light Ldif. Here, the direction of the reproduction illumination light Lrep is a direction whose extension line coincides with the direction of the reference light Lref shown in FIG. 28, and the generation position of the reproduction image 35 is the arrangement position of the scattering plate 30 shown in FIG. Matches.

  Subsequently, a process of recording the image of the scattering plate 30 on the hologram photosensitive medium 40 is performed by using the reproduced image 35 by the preparation hologram recording medium 95 as a substitute for the actual scattering plate 30. That is, as shown in FIG. 30, the hologram photosensitive medium 40 is arranged on the right side of the preparation hologram recording medium 95, and the reproducing light Lrep parallel to the medium 95 is irradiated obliquely from the lower left. A reproduced image 35 is generated on the right side. In this case, the light emitted rightward from the medium 95 is transmitted diffracted light Ldif for reproducing the reproduced image 35, and at the same time, functions as object light Lobj for the medium 40.

  On the other hand, the divergent reference light Lref is applied to the medium 40 from below in the figure. The divergent reference light Lref is light diverging from the convergence point C (light emitted from this point light source when a point light source is present at the convergence point C). A bundle will be irradiated. In the illustrated example, the divergent reference light Lref is generated by generating a point light source by condensing the parallel light beam L10 at the convergence point C by the convex lens 25 having a focal point at the position of the convergence point C. For example, if a microlens having a diameter of about 1 mm is used as the convex lens 25, a divergent reference beam Lref can be generated by using a laser beam having a cross-sectional diameter of about 1 mm emitted from a laser light source as a parallel light beam L10 as it is.

  In the method shown in FIG. 30, the object light Lobj is irradiated on the upper surface of the medium 40, and the reference light Lref is irradiated on the lower surface of the medium 40. In this way, a reflection hologram can be recorded by irradiating the opposite surface with the reference light and the object light. Therefore, the hologram recording medium 45 created by the method shown in FIG. 30 is substantially the same reflection type hologram as the hologram recording medium 45 created by the method shown in FIG. Therefore, the geometrical arrangement shown in FIG.

  On the other hand, FIG. 31 is a side view showing an example of creating a transmission hologram using the divergent reference light Lref. A difference from the arrangement shown in FIG. 30 is the direction of the medium 40. In the method for producing a reflection hologram shown in FIG. 30, the object light Lobj is irradiated from the upper surface of the medium, and the reference light Lref is irradiated from the lower surface of the medium. In contrast, in the method shown in FIG. 31, both the object light Lobj and the reference light Lref are irradiated on the lower surface of the medium 40. As described above, when the reference light and the object light are irradiated from the same side, a transmission hologram can be recorded. The hologram recording medium 45 created by the method shown in FIG. 31 is substantially the same transmission hologram as the hologram recording medium 45 created by the method shown in FIG. Therefore, the geometrical arrangement shown in FIG.

  In the recording process shown in FIGS. 30 and 31, the transmission hologram created by the method shown in FIG. 28 is used as the preparation hologram recording medium 95. However, the preparation hologram recording medium 95 is shown in FIG. It is also possible to use a reflection hologram created by the method. In the method shown in FIG. 32, since the reference beam Lref is irradiated from the left side of the preparation hologram photosensitive medium 90 and the object beam Lobj is irradiated from the right side, the prepared hologram recording medium 95 is a reflection hologram. .

  When reproduction is performed using the reflection-type preparation hologram recording medium 95, as shown in FIG. 33, the reproduction illumination light Lrep is irradiated from the right side of the medium 95, and the reproduced image 35 is obtained by the obtained reflected diffraction light Ldif. Will be generated. Therefore, in the process shown in FIGS. 30 and 31, the reproduction illumination light Lrep is irradiated from the right side instead of being irradiated from the left side.

<4-6> Translational Scanning of Light Beam In the embodiments described so far, the light beam scanning device 60 bends the light beam at a predetermined scanning base point B, and this bending mode (the bending direction and the bending angle are large). However, the scanning method of the light beam scanning device 60 is limited to the method of bending the light beam at the scanning base point B. It is not a thing.

  For example, it is possible to adopt a scanning method in which the light beam is translated. However, in that case, it is also necessary to change the recording method of the scattering plate 30 with respect to the hologram recording medium 45. That is, as in the example shown in FIG. 34, the hologram photosensitive medium 40 is irradiated with the reference light Lref consisting of a parallel light beam, and information on interference fringes with the object light Lobj from the scattering plate 30 is recorded. . In other words, the image 35 of the scattering plate 30 is recorded as a hologram on the hologram recording medium 46 thus created using the reference light Lref consisting of a parallel light beam.

  FIG. 35 is a side view of the illumination device 110 using the hologram recording medium 46 created by the method shown in FIG. As illustrated, the illumination device 110 includes a hologram recording medium 46, a coherent light source 50, and a light beam scanning device 65.

  Here, the hologram recording medium 46 is a medium created by the method shown in FIG. 34, and an image 35 of the scattering plate 30 is recorded as a hologram using reference light Lref consisting of parallel light fluxes. The coherent light source 50 is a coherent light having the same wavelength (or an approximate wavelength capable of reproducing the hologram) as the light (object light Lobj and reference light Lref) used when the hologram recording medium 46 is produced. It is a light source that generates a beam L50.

  On the other hand, the light beam scanning device 65 has a function of irradiating the hologram recording medium 46 with the light beam L50 generated by the coherent light source 50. At this time, the light beam scanning device 65 is parallel to the reference light Lref used in the creation process shown in FIG. Scanning is performed so that the light beam L65 is irradiated onto the hologram recording medium 46 from the direction. More specifically, by irradiating the hologram recording medium 46 while moving the light beam L65 in parallel, scanning is performed such that the irradiation position of the light beam L65 on the hologram recording medium 46 changes with time.

  The light beam scanning device 65 that performs such scanning can be constituted by, for example, a movable reflecting mirror 66 and a drive mechanism that drives the movable reflecting mirror 66. That is, as shown in FIG. 35, the movable reflecting mirror 66 is disposed at a position where the light beam L50 generated by the coherent light source 50 can be received, and the movable reflecting mirror 66 is slid along the optical axis of the light beam L50. A drive mechanism may be provided. In practice, the light beam scanning device 65 having a function equivalent to the above function can be configured by a micromirror device using MEMS. Alternatively, the light beam L60 bent at the position of the scanning base point B by the light beam scanning device 60 shown in FIG. 9 is passed through a convex lens having a focal point at the scanning base point B, thereby generating a light beam that moves in parallel. Can do.

  In the case of the example shown in FIG. 35, the hologram recording medium 46 that has been irradiated with the light beam L65 reflected by the movable reflecting mirror 66 generates diffracted light based on the recorded interference fringes. A reproduced image 35 is generated. The illumination device 110 performs illumination using the reproduction light of the reproduction image 35 thus obtained as illumination light.

  In FIG. 35, for convenience of explanation, the position of the light beam at time t1 is indicated by a one-dot chain line, and the position of the light beam at time t2 is indicated by a two-dot chain line. That is, at time t1, the light beam L50 is reflected at the position of the movable reflecting mirror 66 (t1), and is applied to the point P (t1) of the hologram recording medium 46 as the light beam L65 (t1), but at time t2. The light beam L50 is reflected at the position of the movable reflecting mirror 66 (t2) (the movable reflecting mirror 66 (t2) shown in FIG. 2 is the one in which the movable reflecting mirror 66 (t1) is moved), and the light beam L65 (t2). ) To the point P (t2) of the hologram recording medium 46.

  For the sake of convenience, only the scanning mode at two points in time t1 and t2 is shown in the figure, but in reality, the light beam L65 moves in parallel to the right and left in the figure during the period from time t1 to t2. The irradiation position of the L65 on the hologram recording medium 46 gradually moves from the point P (t1) to P (t2) in the figure. That is, in the period from time t1 to time t2, the irradiation position of the light beam L65 is scanned from the point P (t1) to P (t2) on the hologram recording medium 46. Here, an example has been described in which the light beam L65 is translated in the one-dimensional direction (the left-right direction in the figure), but of course, a mechanism (for example, an XY stage) that translates the light beam 65 in a direction perpendicular to the drawing sheet as well. If a mechanism (with a reflecting mirror disposed thereon) is provided, it can be translated in a two-dimensional direction.

  Here, since the light beam L65 is scanned so as to be always parallel to the reference light Lref used in the creation process shown in FIG. 34, the light beam L65 is recorded at each irradiation position of the hologram recording medium 46. It functions as the correct reproduction illumination light Lrep for reproducing the hologram being reproduced.

  For example, at time t1, a reproduced image 35 of the scattering plate 30 is generated by diffracted light L46 (t1) from point P (t1), and at time t2, diffracted light L46 (t2) from point P (t2) is generated. A reproduced image 35 of the scattering plate 30 is generated. Of course, also during the period from time t1 to t2, the reproduced image 35 of the scattering plate 30 is similarly generated by the diffracted light from each position irradiated with the light beam L65. That is, as long as the light beam L65 undergoes parallel scanning, no matter where the light beam L65 is irradiated on the hologram recording medium 46, the same reproduced image 35 is generated at the same position by the diffracted light from the irradiation position. Will be.

  Eventually, the illumination device 110 shown in FIG. 35 can perform illumination using the reproduction light of the reproduction image 35 as illumination light, similarly to the illumination device 100 shown in FIG. In short, in the present invention, an image of the scattering plate is recorded as a hologram on the hologram recording medium using reference light irradiated along a predetermined optical path, and the light beam scanning device applies a light beam to the hologram recording medium. The light beam may be scanned so that the irradiation direction is a direction along the optical path of the reference light (an optically conjugate direction).

<4-7> Utilization of Microlens Array In the embodiments described so far, a hologram recording medium on which a hologram image of the scattering plate 30 is recorded is prepared, and the hologram recording medium is scanned with coherent light. The diffracted light produced is used as illumination light. Here, a modified example using a microlens array instead of the hologram recording medium will be described.

  FIG. 36 is a side view of a modification using this microlens array. The illumination device 120 according to this modification includes a microlens array 48, a coherent light source 50, and a light beam scanning device 60. The coherent light source 50 is a light source that generates a coherent light beam L50 as in the above-described embodiments. Specifically, a laser light source can be used.

  The light beam scanning device 60 is a device that scans the light beam L50 generated by the coherent light source 50, as in the above-described embodiments. More specifically, it has a function of irradiating the microlens array 48 with the light beam bent at the scanning base point B. Further, by changing the bending mode of the light beam L50 with time, the microlens of the light beam L60 is changed. Scanning is performed so that the irradiation position on the lens array 48 changes with time.

  On the other hand, the microlens array 48 is an optical element composed of an assembly of a large number of individual lenses. Each of the individual lenses constituting the microlens array 48 has a function of refracting light incident from the scanning base point B and forming a predetermined irradiation region I on the light receiving surface R of the illumination target 70. . Moreover, the irradiation area I formed by any individual lens is configured to be the same common area on the light receiving surface R. As a microlens array having such a function, for example, a so-called “fly eye lens” is commercially available.

  FIG. 37 is a side view showing the operation principle of the illumination device 120 shown in FIG. Also here, for convenience of explanation, the bending mode at the time t1 of the light beam L60 is indicated by a one-dot chain line, and the bending mode at the time t2 is indicated by a two-dot chain line. That is, at time t1, the light beam L50 bends at the scanning base point B and enters the individual lens 48-1 positioned below the microlens array 48 as the light beam L60 (t1). The individual lens 48-1 has a function of expanding the light beam incident from the scanning base point B and irradiating the two-dimensional irradiation region I on the light receiving surface R of the illumination target 70. Therefore, an irradiation region I is formed on the light receiving surface R as shown in the figure.

  At time t2, the light beam L50 is bent at the scanning base point B, and enters the individual lens 48-2 positioned above the microlens array 48 as the light beam L60 (t2). The individual lens 48-2 has a function of expanding the light beam incident from the scanning base point B and irradiating the two-dimensional irradiation region I on the light receiving surface R of the illumination target 70. Therefore, the irradiation region I is formed on the light receiving surface R as shown in the figure at time t2.

  In the figure, for the sake of convenience, only the operating states at two points in time t1 and t2 are shown, but actually, the bending direction of the light beam changes smoothly during the period from time t1 to t2, and the light beam L60. The irradiation position with respect to the microlens array 48 gradually moves from the lower side to the upper side in the figure. That is, the irradiation position of the light beam L60 is scanned up and down on the microlens array 48 during the period from time t1 to time t2. Of course, when a microlens array 48 in which a large number of individual lenses are arranged two-dimensionally is used, the light beam can be scanned on the two-dimensional array by the light beam scanning device 60. Good.

  Due to the properties of the microlens array 48 described above, the two-dimensional irradiation region I formed on the light receiving surface R is common regardless of which individual lens the light beam L60 enters. That is, regardless of the scanning state of the light beam, the same irradiation area I is always formed on the light receiving surface R, and the same illumination spot is formed. However, in practice, even if the irradiation area I generated by the individual lenses is not completely the same and is slightly deviated, there is no problem as a lighting device. In this case, the position of the illumination spot varies with time. However, if the scanning speed by the light beam scanning device 60 is set to be somewhat high, the position of the illumination spot is not recognized by humans and the contour is It just feels somewhat blurred.

  After all, in the case of the illumination device 120 shown here, the light beam scanning device 60 irradiates the microlens array 48 with the light beam L60, and the irradiation position of the light beam L60 on the microlens array 48 changes with time. It has a function to scan. On the other hand, each of the individual lenses constituting the microlens array 48 has a function of refracting light irradiated from the light beam scanning device 60 to form a predetermined irradiation region I on a predetermined light receiving surface R. In addition, the irradiation region I formed by any of the individual lenses is configured to be substantially the same common region on the light receiving surface R.

  Also in the case of this illuminating device 120, since the coherent light source 50 is used, an extremely novel illumination effect is exhibited for the observer. That is, monochromatic surface illumination with extremely high color purity is possible due to the monochromaticity of coherent light. Further, due to the directivity, an illumination spot having a sharp outline can be formed. Furthermore, if a laser light source having high light conversion efficiency is used, illumination with high luminance can be achieved with low power consumption. In addition, similar to the illumination device according to the basic embodiment described so far, the incidence angle of light irradiated to each part of the light receiving surface R is temporally multiplexed, so speckle generation is suppressed. The

<4-8> Utilization of Light Diffusing Element As an example of the basic embodiment so far, an example in which an illumination device is configured using a hologram recording medium on which a hologram image of the scattering plate 30 is recorded will be described. 7>, an example in which an illumination device is configured using a microlens array instead of a hologram recording medium has been described. In these illumination devices, the hologram recording medium and the microlens array eventually serve as a light diffusing element having a function of diffusing an incident light beam to form a predetermined irradiation area on a predetermined light receiving surface. Will be. Moreover, the light diffusing element has a feature that the formed irradiation region becomes the same common region on the light receiving surface regardless of the incident position of the light beam. Therefore, in order to configure the illumination device according to the present invention, it is not always necessary to use the hologram recording medium or the microlens array described above, and in general, it can be configured using the light diffusing element having the above characteristics.

  In short, the illumination device according to the present invention essentially includes a coherent light source that generates a coherent light beam, and a light beam scanning device that performs beam scanning by controlling the direction and / or position of the light beam. And a light diffusing element that diffuses and emits an incident light beam.

  Here, the light beam scanning device emits the light beam generated by the coherent light source toward the light diffusing element, and scans so that the incident position of the light beam with respect to the light diffusing element changes with time. As long as it has. The light diffusing element has a function of diffusing an incident light beam to form a predetermined irradiation region on a predetermined light receiving surface, and the irradiation region to be formed is independent of the incident position of the light beam. The light receiving surface may be configured to have substantially the same common area.

  The illuminating device according to the present invention can be used for applications that provide illumination light in various environments, whether outdoors or indoors. In particular, since coherent light is used as illumination light, illumination with excellent monochromaticity and directivity is possible, and it is suitable for interior lighting in restaurants and hotels. Moreover, since it is excellent in monochromaticity, it is suitable for use as illumination for color evaluation. Furthermore, the present invention can be used not only for an apparatus that directly uses illumination, but also as illumination light providing means in various devices that require some illumination light. For example, the present invention can also be used for general image display devices, projectors, scanners, and the like.

10: Coherent light source 11: Reflector 12: Beam expander 15, 16: Light combiner 20: Beam splitter 21: Reflector 22: Beam expander 23: Convex lens 24: Cylindrical lens 25: Convex lenses 30, 30A, 30B: Scattering plate 30 ' : Virtual scattering plates 33A, 33B, 33C: Transmission film 35: Scattering plate image 40: Hologram photosensitive medium 40 ': Virtual recording surface 45, 46: Hologram recording medium 48: Microlens arrays 48-1, 48-2 : Individual lens 50: Coherent light source 50R, 50G, 50B: Laser light source 60, 65: Light beam scanning device 66: Movable reflector 70: Illumination object 75: Table 76, 77: Chair 80: Hologram photosensitive medium 85: Hologram recording Medium 90: Preparation hologram photosensitive medium 95: Preparation holog Recording medium 100: lighting device 110: lighting device 120: lighting device 200: indoor floor 210: ceiling A1, A2: cross sections A1S, A1E, A2S, A2E, A3S, A3E, AnS, AnE of the reproduction illumination light: Cross section a1 to a4 of reproduction illumination light: Area B: Scanning base point C: Convergence point D: Point light source Da: Horizontal width Db of hologram recording medium: Vertical width I of hologram recording medium I: Irradiation area L10: Light beam L11: Light beam L12: Parallel light beam L20: Light beam L21: Light beam L22: Parallel light beam L23: Reference light L30: Scattered light L31 to L33: Object light L45, L46: Diffracted light L50: Light beams L60, L61, L62, L65: Light beam Ldif: Diffracted light Lobj: Object light Lref: Reference light Lrep: Reproduction illumination light L (R): Red laser beam L (R, G): Synthetic light beam L (R, G, ): Composite light beams P, P1, P2: Irradiation points Pa, Pb: Pitch Q of point light source D: Points of interest Q1-Q3: Object points R: Light receiving surfaces S1, S2: Reference light sections t1, t2: Time V , W: Rotating shaft

Claims (3)

A coherent light source that generates a coherent light beam;
A microlens array consisting of a collection of many individual lenses;
A light beam scanning device that irradiates the microlens array with the light beam and scans so that an irradiation position of the light beam with respect to the microlens array changes with time;
With
Each of the individual lenses constituting the microlens array has a function of refracting light irradiated from the light beam scanning device to form a predetermined irradiation area on a predetermined light receiving surface, and The irradiation area formed by the individual lens is also configured to be substantially the same common area on the light receiving surface ,
The light beam scanning device includes a reflecting mirror that reflects the light beam, and a rotating mechanism that rotates the reflecting mirror with a scanning base point defined on the reflecting surface as a fixed point. Is reflected and bent by the reflecting mirror to irradiate the microlens array, and the bending position of the light beam is temporally changed, so that the irradiation position of the bent light beam to the microlens array is temporally changed. To change to
Each of the individual lenses constituting the microlens array refracts the light reflected and bent by the reflecting mirror to form a common irradiation area on the light receiving surface, and an illumination device using a coherent light source. The lighting device according to claim 1.
In the microlens array, a large number of individual lenses are two-dimensionally arranged.
When the rotation mechanism of the light beam scanning device defines a V axis and a W axis that pass through the scanning base point and are orthogonal to each other on the reflecting surface, a mechanism for rotating the reflecting mirror around the V axis and a rotation around the W axis are provided. An illumination device using a coherent light source, wherein the light beam is scanned in the horizontal direction and the vertical direction on the microlens array. The lighting device according to claim 1.
In the microlens array, a large number of individual lenses are two-dimensionally arranged.
  An illumination device using a coherent light source, wherein the rotation mechanism of the light beam scanning device performs scanning such that the light beam reflected by the reflecting mirror draws a circle on the microlens array.

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