JP2014016396A - Hologram reproduction device, hologram reproduction method, projection type video display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a hologram reproduction device (regeneration method) with no conspicuous bright spot, and a projection type video display device using the hologram reproduction device.SOLUTION: A hologram reproduction device includes: a hologram composed of element holograms periodically arranged; and a light source for illuminating illumination light onto the hologram. A predetermined conditional expression (1) is satisfied by a line segment formed by half value and half width of illumination light that illuminates a certain point on the hologram and an angle Δθ formed with a reproduction incidence direction of the hologram.

Description

  The present invention relates to a hologram reproducing method and apparatus configured by periodically arranging elementary holograms, and a projection display apparatus using the hologram reproducing apparatus.

  2. Description of the Related Art A hologram reproduction apparatus that emits reproduction light including an image by irradiating a hologram on which an image has been recorded in advance with illumination light is well known. As a method for manufacturing a hologram used in such a hologram reproducing apparatus, there is known a method of recording interference fringes on a hologram by simultaneously irradiating the hologram with reference light and object light from an image.

  In addition to such a manufacturing method, a method of manufacturing interference fringes generated by reference light and object light by a computer is also known. Holograms manufactured by such a method are called computer generated holograms and occupy an important position in various application fields such as interference measurement, optical information processing, security or holographic display.

  In such a computer-generated hologram manufacturing method, a pattern is formed based on the interference fringes calculated by calculation, and the hologram is shaped with the formed mold, whereby the interference fringes are recorded as irregularities on the surface of the hologram. Thus, in the computer generated hologram, the unevenness can be easily duplicated by using a mold, which is suitable for mass production.

  However, calculation of interference fringes by a computer requires an enormous amount of calculation, and a long calculation is required for one computer hologram. Therefore, an interference fringe relating to a relatively small computer hologram is obtained by calculation, and the computer hologram is formed by periodically arranging the computer generated hologram.

  Patent Document 1 discloses a beam homogenizer in which sub-holograms (facets 12) formed by computer-formed holograms (corresponding to the above-described computer generated holograms) are arranged as an M × N linear matrix. The light emitted from each sub-hologram overlaps on the output plane, and the light that has passed through each sub-hologram can be uniformly mixed.

JP-T-2001-507139 Japanese Patent Laid-Open No. 6-208089

  By the way, in the hologram configured by arranging small-sized holograms (hereinafter referred to as “element holograms”) as described above, the diameter of the illumination light beam for reproducing the hologram is larger than the element hologram, that is, the illumination light beams are adjacent to each other at the same time. When the element hologram is illuminated, the reproduced image of the hologram is not uniform and a periodic structure appears. Such a periodic structure of the hologram deteriorates the reproduced image. In addition, when the reproduction light from the hologram is used as illumination light for a projection display apparatus or the like, it should be illuminated with uniform illuminance, and such a periodic structure is manifested and displayed as illuminance unevenness. The quality of the video will be degraded.

FIG. 1 shows how a periodic structure appears in a reproduced image in a hologram reproducing apparatus. The hologram reproducing apparatus 1 includes a hologram 10 and a Fourier transform lens 20. In the drawing, the X axis and the Y axis are defined so that the plane forming the entrance (exit) surface of the hologram 10 is the XY plane, and the direction on the side where the illumination light L ₁ travels is orthogonal to the XY plane. It is defined as the Z axis.

  FIG. 2 shows a configuration (a part) of the hologram 10 as viewed from the Z-axis side. As shown in the figure, the hologram 10 is composed of a plurality of element holograms 11 adjacent to each other. Each element hologram 11 has a square shape with one side having a pitch p. In this manner, the element holograms 11 are arranged adjacent to each other so that the element holograms 11 are periodically arranged.

When such a hologram 10 is irradiated with illumination light L ₁ as shown by a broken line, that is, illumination light of a size that illuminates across a plurality of element holograms 11, the periodic structure in the reproduced image described above Is a problem.

Returning to FIG. 1, the illumination light L ₁ is incident on the hologram 10 from a predetermined incident direction (reproduction incident direction) for reproducing a reproduction image. The illumination light L ₁ is coherent light emitted from a laser light source unit is used. The illumination light L1 incident on the hologram 10 is a light beam parallel to the reproduction incident direction. The reproduction incident direction is an incident angle to the hologram 10 that is determined when the hologram 10 is designed. By irradiating the illumination light L ₁ along the reproduction incident direction, the reproduction image 21i at the time of design can be obtained. Played. Each element hologram 11 constituting the hologram 10 emits reproduction light L ₂ based on the incident illumination light L ₁ . The reproduction light L ₂ emitted from each element hologram 11 passes through the Fourier transform lens 20 (the front focal length and the rear focal length are both f), thereby forming a reproduction image at the same position.

Here, an image having a uniform illuminance is recorded on the hologram 10 at any location of the reproduced image 21i. Therefore, the ideal illuminance distribution of the reproduced image 21i is uniform. However, as described above, when the illumination light L ₁ is simultaneously illuminated across the plurality of element holograms 11, the reproduction light L ₂ from each element hologram 11 interferes,
Irradiance unevenness will occur. This illuminance unevenness has a periodic structure, and as shown in FIG. 1, the bright spot centers 22 are periodically arranged, and the reproduced image is deteriorated.

  On the other hand, in a projection display apparatus, when coherent laser light is used as a light source, speckle noise is generated due to interference of light scattered from minute irregularities on the surface of the irradiation target, which deteriorates the reproduced image. Or it is known to make it difficult to see.

  Patent Document 2 discloses a non-speckle display device that reduces speckle noise by rotating a diffusion element through which coherent light passes. However, in the speckle noise reduction method disclosed in Patent Document 2, speckle noise (interference pattern) generated before reaching the diffusing element can be averaged, but the incident ray angle from the diffusion center to the screen is on the screen. Since it is invariant at any point, the light scattering characteristic of each point on the screen is also constant, and as a result, there is a problem that the effect of removing speckles generated on the screen is hardly obtained.

  Such speckle caused by coherent light is a problem not only in projectors (projection-type image display devices) that use coherent light as a light source, but also in various illumination devices that use coherent light.

  The present invention solves such a problem, and is characterized by having the following constituent elements.

The hologram reproduction method according to the present invention includes:
In a hologram reproducing method for reproducing a hologram configured by periodically arranging element holograms,
An angle Δθ formed by a line segment formed by a half-width of illumination light incident on a certain point on the hologram and a reproduction incident direction of the hologram satisfies the following conditional expression (1).
Δθ ≧ λ / 2p (1)
However,
λ is the wavelength of the illumination light,
p is the size of one side of the element hologram

Furthermore, in the hologram reproduction method according to the present invention,
The angle Δθ satisfies the following conditional expression (2).
Δθ ≦ 5λ / p (2)

Moreover, the hologram reproducing apparatus according to the present invention includes:
A hologram constructed by periodically arranging element holograms;
A light source for illuminating the hologram with illumination light,
An angle Δθ formed by a line segment formed by a half-width of illumination light incident on a certain point on the hologram and a reproduction incident direction of the hologram satisfies the following conditional expression (1).
Δθ ≧ λ / 2p (1)
However,
λ is the wavelength of the illumination light,
p is the size of one side of the element hologram

Furthermore, in the hologram reproducing apparatus according to the present invention,
The angle Δθ satisfies the following conditional expression (2).
Δθ ≦ 5λ / p (2)

Furthermore, in the hologram reproducing apparatus according to the present invention,
The light source has a laser light source part and a scattering element,
The scattering element provides angular distribution to coherent light emitted from the laser light source unit and emits the illumination light as illumination light.

Furthermore, in the hologram reproducing apparatus according to the present invention,
The light source has a laser light source unit and a plurality of optical fibers,
The optical fiber is characterized in that it gives an angular distribution to coherent light emitted from the laser light source unit and emits it as illumination light.

Furthermore, in the hologram reproducing apparatus according to the present invention,
The light source has a laser light source unit and a lens array,
The lens array is characterized in that the coherent light emitted from the laser light source unit is given an angular distribution and emitted as illumination light.

A projection display apparatus according to the present invention is also provided:
A light source that emits illumination light;
The optical scanning unit that scans illumination light emitted from the light source; and
A light modulation element having an image forming region on which an image is formed;
Comprising element holograms arranged periodically, diffusing illumination light scanned by the optical scanning unit, and reproducing light emitted from each point to illuminate the image forming region in an overlapping manner,
An angle Δθ formed by a line segment formed by a half-width of illumination light incident on a certain point on the hologram and a reproduction incident direction of the hologram satisfies the following conditional expression (1).
Δθ ≧ λ / 2p (1)
However,
λ is the wavelength of the illumination light,
p is the size of one side of the element hologram

Furthermore, in the projection display apparatus according to the present invention,
The angle Δθ satisfies the following conditional expression (2).
Δθ ≦ 5λ / p (2)

Furthermore, in the projection display apparatus according to the present invention,
The angle Δθ satisfies the following conditional expression (3).
Δθ ≦ θ ₀ (3)
However,
θ ₀ is the angular width for viewing the short side of the image forming area from one point on the hologram

  According to the present invention, when reproducing a hologram configured by periodically arranging element holograms, it is possible to suppress a periodic structure such as a bright spot generated in a reproduced image and to suppress degradation of the reproduced image. . By adopting such a hologram reproducing device (method) in a projection-type image display device, it is possible to suppress unevenness of the reproducing light that illuminates the light modulation element and improve the image projected on the screen. It becomes.

  Furthermore, the projection display apparatus of the present invention uses a hologram that diffuses the illumination light scanned by the optical scanning unit and illuminates the reproduction light emitted from each point by overlapping the image forming area of the light modulation element. ing. With such a configuration, the reproduction light from the hologram is irradiated at different angles with respect to the screen, and speckles generated on the screen can be effectively suppressed.

The figure for demonstrating the structure of a hologram reproduction apparatus The figure for demonstrating the hologram comprised by the several element hologram The figure for demonstrating the structure of the hologram reproducing apparatus which concerns on embodiment of this invention. The figure for demonstrating the reproduction image reproduced | regenerated with a hologram Schematic diagram for explaining illumination light L ₁ and illuminance distribution of a reproduced image of a hologram The figure which shows the reproduction image of a hologram when illuminating a light modulation element The figure which shows the structure of the projection type video display apparatus concerning embodiment of this invention. The figure which shows the structure of the projection type video display apparatus concerning embodiment of this invention. The figure which shows the structure of the light source used with the projection type video display apparatus (or hologram reproduction apparatus) which concerns on embodiment of this invention.

  The hologram apparatus according to the embodiment of the present invention will be described with reference to the drawings. FIG. 3 is a diagram showing a configuration of the hologram reproducing apparatus 1 according to the embodiment of the present invention. The drawings described below are schematic views, and may differ from actual shapes, dimensions, and arrangements.

3 has the same configuration as the configuration described in FIGS. 1 and 2 except for the illumination of the illumination light L ₁ , and a plurality of element holograms 11 are periodically arranged. , The hologram 10 arranged in a matrix, the Fourier transform lens 31, and the illumination light L ₁
The light source (not shown) which radiates | emits is comprised.

  A computer generated hologram is adopted as the element hologram 11 constituting the hologram 10. A computer generated hologram is a hologram in which interference fringes calculated by a computer are recorded as surface irregularities. Such a computer generated hologram can be mass-produced by forming a concavo-convex shape using a printing technique or the like. Further, by duplicating and using the plurality of element holograms 11 constituting the hologram 10, it is possible to suppress the calculation amount necessary for calculating the interference fringes.

In FIG. 3, a point A having an incident surface of the hologram 10 will be described with respect to the illumination light L ₁ incident on the hologram 10. When the hologram 10 is actually reproduced, the illumination light L ₁ is incident over a wide area of the incident surface of the hologram 10. This hologram 10
The incident light L ₁ incident on the point A is configured to satisfy the following incident angle conditions. That is, the reproduction incident direction L _1C of the hologram 10 indicated by the alternate long and short dash line, that is, when reproducing the hologram 10 (element hologram 11), the angle Δθ with respect to the reproduction incident direction set in advance in the hologram 10 (element hologram 11). It is made to enter so as to form.

At this time, since the light beam forming the illumination light L ₁ has an intensity distribution, the angle Δθ is set at a certain point A.
Is defined by a line segment formed with a half width at half maximum of the illumination light L ₁ incident on the beam. That is, the angle formed by the line segment formed at the half-width at half maximum of the illumination light L ₁ incident on the predetermined position on the hologram 10 with the reproduction incident direction L _1C of the hologram 10 is defined as Δθ. In FIG. 5 (a), in Figure 3, the orthogonal for between B-B of the illumination light L _1, the illuminance distribution of the illumination light L ₁ is shown.

In this manner, the illumination light L ₁ is made incident at an angle Δθ to the playback incidence direction L _1C, the illumination light L ₁ incident on the (point A in the figure) any point of the hologram 10 is reproduced It is converted into light L ₂ and converted into a reproduced image 21 i having a half-value half-width ΔXB. The half-value half width ΔXB formed on the reproduced image 21i eliminates the uneven illuminance in which the center points are periodically arranged. FIG. 5B shows the illuminance distribution formed on the reproduced image 21 i of the hologram 10. When the illumination light L ₁ having the illuminance distribution described with reference to FIG. 5A is used, the reproduced image 21 i also has an illuminance distribution with the bright spot center 22 as the center. Here, the half width at half maximum of each bright spot generated around the bright spot center 22 is defined as ΔXB.

In FIG. 3, the angle Δθ with respect to the reproduction incident direction of the hologram 10 and the half-value half width ΔXB on the reproduction image 21 i can be approximated by the following equations.
ΔXB = f × Δθ (a)
f is the focal length of the Fourier transform lens 20

FIG. 4 schematically shows a reproduced image 21i on the XY plane. Due to the periodic arrangement of the element holograms 11, bright spots generated on the reproduced image 21i are generated with an interval of ΔX. That is, the bright spot interval ΔX corresponds to the center distance of the bright spot and can be approximated by the following equation.
ΔX = f × λ / p (b)
However,
λ is the wavelength of the illumination light L ₁ , p is the size of one side of the element hologram 11.

In the present embodiment, the incident light L ₁ is given an angle Δθ with respect to the reproduction incident direction, so that the illumination range of each bright spot generated by the reproduction light L ₂ is changed as shown in FIG. Duplicate
It suppresses (averages) the occurrence of bright spots. Specifically, the following formula (c) is used, and it is preferable that the center interval ΔX of the bright spots and the half width ΔXB of the reproduction light L ₂ have the following relationship.
ΔXB ≧ ΔX / 2 (c)

  This equation (c) shows the condition when the half-value half width ΔXB touches or overlaps in FIG. 4. By satisfying this equation (c), the illuminance is averaged between a plurality of bright spots. This makes it possible to suppress bright spot unevenness.

By substituting the above-described expressions (a) and (b) into this expression (c), the focal length f of the Fourier transform lens 20 is deleted, and the following conditional expression (1) is obtained.
Δθ ≧ λ / 2p (1)
However,
λ is the wavelength of the illumination light L ₁ ,
p is the size of one side of the element hologram 11

Conditional expression (1) defines the lower limit of the angle Δθ with respect to the reproduction incident direction of the incident light L ₁ . By increasing the angle Δθ, it is possible to suppress bright spots generated in the reproduced image 21i. On the other hand, the half value half width ΔXB in the reproduced image 21i increases as the angle Δθ increases. Therefore, when the reproduced image 21i such as an object is reproduced by the hologram 10, the outline of the reproduced object becomes blurred. In order to suppress such blurring, when an object image is reproduced with the hologram 10, the upper limit value of the angle Δθ should be suppressed to 10 times or less the lower limit value defined by the conditional expression (1). preferable. That is, it is preferable to satisfy the conditional expression (2) in which a value obtained by multiplying the right side of the conditional expression (1) by 10 is an upper limit value of Δθ.
Δθ ≦ 5λ / p (2)

Thus, by defining the lower limit of the angle Δθ of the illumination light L ₁ so as to satisfy the conditional expression (1), it is possible to suppress the generation of bright spots. Further, by defining the angle Δθ of the illumination light L ₁ so as to satisfy the conditional expression (2), it is possible to provide a reproduced image 21i with a clear outline.

An embodiment performed for the hologram reproducing apparatus 1 described above will be described. In this embodiment, in the hologram reproducing apparatus 1 described with reference to FIG. 3, an angle Δθ is given to the illumination light L ₁ .
This is a comparison of the occurrence of bright spots when not applied. In order to clearly observe the generation of bright spots, the hologram 10 (element hologram 11) uses a recorded reproduction image having a constant illuminance distribution. Further, the angle Δθ is given by transmitting the illumination light emitted from the light source through the diffusion plate. The specifications of the hologram 10 used in the present embodiment and the reproduction conditions of the hologram reproduction apparatus 1 are shown below.

In the present embodiment using the diffusion plate, the angle Δθ formed by the illumination light incident on the hologram 10 is converted using the optical system until the scattering angle φ of the diffusion plate reaches the hologram 10. It was confirmed in. Here, the scattering angle φ of the diffusing plate is an angle formed by a line segment formed by the half width at half maximum of scattered light diffused by the diffusing plate and the optical axis. The confirmation of the angle Δθ can also be performed by directly observing the incident light incident on the hologram 10 in addition to the form calculated using the scattering angle φ from the light source. For example, it is possible to confirm Δθ formed by the illumination light by installing a pinhole in front of the hologram 10 and detecting the intensity distribution of the illumination light that has passed through the pinhole with a CCD sensor or the like.

(Example)
(Specifications of hologram (CGH: computer generated hologram))
Reproduced image size 10 × 10mm
Element hologram pixel 0.1μm square
Score 2000 × 2000
Dimensions 200μm × 200μm
Calculation method Use IFTA (iterative Fourier transform) Form Binary relief type with etched glass Size of hologram 6000μm × 6000μm
Consists of 30 element x 30 element holograms

(Playback conditions)
Wavelength 532nm laser Illumination beam width 4mmφ
Optical system Use Fourier transform lens with focal length of 100mm Angle Δθ No diffuser plate Δθ = ± 0 ° (Parallel light)
With diffusion plate Δθ = ± 0.1 °

Below, it shows about evaluation of conditional expression (1) with the result of a present Example.
(result)
No diffuser plate Vertical 38 x horizontal 38 bright spot generation, illumination unevenness diffusion plate exist Bright spot cannot be confirmed, no illumination unevenness When using a diffuser plate, that is, when the angle Δθ ± 0.1 deg, conditional expression (1) is evaluated. The values on the left and right sides of conditional expression (1) are calculated as follows.
(Left side) = Δθ = 0.1 [deg]
(Right side) = λ / 2p
= 0.532 / (2 * 200)
= 0.00133 [rad]
= 0.076 [deg]
(Left side)> (Right side), and it is understood that the conditional expression (1) is satisfied. That is, by providing an angle Δθ that satisfies the conditional expression (1) (with a diffuser), it can be confirmed that the generation of bright spots can be suppressed during the reproduction of a hologram composed of periodically arranged element holograms. It was.

On the other hand, a form in which the reproduction light L ₂ of the hologram 10 is used as an illumination device such as a projection display device is conceivable. In such a case, the reproduced image 21i emitted from the hologram 10 needs to be illuminated uniformly so as not to cause uneven illumination. That is, even when the hologram 10 composed of the element hologram 11 is used, it is possible to suppress the occurrence of bright spots in the reproduced image 21i by satisfying the above-described formula (1).

In the form in which the hologram 10 is used as such an illuminating device, the sharpness of the outline of the reproduced image 21i is not required, and therefore the upper limit of the angle Δθ can be relaxed. FIG. 6 is a diagram showing a form in the case where the hologram 10 is used as an illuminating device used in a projection video display device or the like, and is a diagram on the XY plane of the optical modulation element 40 to be illuminated. . The coordinate system is the same as in FIG. The hologram 10 illuminates the image forming area 41 in the light modulation element 40 as an illuminated area.

The image forming region 41 in the light modulation element 40 has a size of vertical X ₀ and horizontal Y ₀ . When the image forming area 41 is illuminated by the conventional hologram reproducing apparatus 1 described with reference to FIG. 1, a bright spot centered on the bright spot center 22 indicated by a black spot is generated. In the present embodiment, the incident light L ₁ has an angle Δθ with respect to the reproduction incident direction, thereby forming a half-value half-width ΔXB in the reproduced image 21 i of the hologram 10 and suppressing the bright spot. When the hologram reproducing device 1 is used as an illumination device that illuminates the light modulation element 40 as in the present embodiment, it is preferable that the upper limit value of the angle Δθ satisfies the following conditions.

That is, the angle Δθ is such that the half widths ΔXB located at both ends are not in contact with each other on the short side (the length X ₀ in the X-axis direction in the case of FIG. 6) of the image forming region 41 of the light modulation element 40. It is preferable that That is, it is preferable that the following formula (d) is satisfied.
ΔXB ≦ X ₀ (d)

Here, X ₀ can be rewritten by the following equation (e).
X ₀ = f × θ ₀ (e)
f is the focal length of the Fourier transform lens 20 θ ₀ is the angular width of the short side of the image forming region 41 from one point on the hologram 10

Therefore, when the hologram reproducing device 1 is used as an illumination device such as a projection video display device, the upper limit value of the angle Δθ is shown below by substituting the equations (a) and (e) into the equation (d). It can be expressed by conditional expression (3).
Δθ ≦ Δθ ₀ (3)
However,
θ ₀ is an angular width in which the short side of the image forming region is seen from one point on the hologram 10

  By satisfying the conditional expression (3), it is possible to suppress unnecessary illumination, that is, illumination of portions other than the image forming area 41 as an illuminated area while suppressing generation of bright spots. Even when used as a lighting device, the upper limit value of the angle Δθ may be defined by the conditional expression (2).

7 and 8 show an embodiment in which the hologram reproducing device is used as an illumination device for the projection video apparatus 2 in this way. The projection display apparatus 2 according to this embodiment includes a light source 30, a first lens 51, an optical scanning unit 60, a second lens 52, a hologram 10, a light modulation element 40, and a projection optical system 53. 7 shows a configuration from the light source 20 to the hologram 10, and in FIG. 8, the reproduction light L ₂ emitted from the hologram 10 passes through the light modulation element 40 and becomes the image reproduction light L ₃ . The configuration until projected onto the screen 54 is shown.

The light source 30 shown in FIG. 7 includes a laser light source unit 31 that emits coherent light, and a scattering plate 3 that imparts a scattering angle φ (angle distribution) to the emitted coherent light and converts it into scattered light L _0.
2 (“scattering element” in the present invention). The scattering angle φ given by the scattering plate 32 forms an angle Δθ formed with respect to the reproduction incident direction L _1C of the hologram 10 described later.

In this embodiment, the scattering plate 32 is used in order to give the scattering angle φ to the coherent light. However, other forms may be adopted to give the scattering angle φ to the parallel coherent light. . FIG. 9 shows another form in which the scattering angle φ is given to the coherent light from the laser light source unit 31. FIG. 9A shows a form using a plurality of optical fibers 33, and the coherent light emitted from the laser light source unit 31 passes through the plurality of optical fibers 33 and is scattered at the end of each optical fiber 33. Is converted into scattered light L ₀ . On the other hand, FIG. 9B shows a form using the lens array 34. The lens array 34 is composed of a plurality of element lenses. The coherent light emitted from the laser light source unit 31 is converted into scattered light L ₀ having a scattering angle φ by passing through each element lens.

In the projection display apparatus 2, the scattered light L ₀ passes through the first lens 51 and the second lens 52 and is converted into illumination light L ₁ to illuminate the hologram 10. In this embodiment, in the route,
An optical scanning unit 60 is provided, and the illumination position of the illumination light L ₁ is moved (scanned) over time. The optical scanning unit 60 is a mirror device that can rotate the reflection surface around the rotation center Ra, and mechanically rotates a movable mirror such as a polygon mirror, a galvano scanner, or a MEMS scanner. Is used. As the optical scanning unit 60 that scans the scattered light L ₀ , various forms such as those that modulate the refractive index, such as an acousto-optic effect scanner, can be adopted in addition to such forms.

The scattered light L ₀ scanned by the light scanning unit 60 moves on the hologram 10 with time as illumination light L ₁ . At this time, the illumination light L ₁ incident on the hologram 10 as described in FIG.
Is set so as to form an angle Δθ with respect to the reproduction incident direction L _1C set in the hologram 10. This angle Δθ is set so as to satisfy at least the above-described conditional expression (1), so that bright spots generated in the illumination area can be suppressed. Furthermore, by satisfying conditional expression (3), the illuminated area by the hologram 10 is prevented from significantly exceeding the image forming area 41 in the light modulation element 40, and the illumination light L ₁ is used efficiently. Making it possible.

FIG. 7 shows the optical paths of the two scattered lights L ₀ emitted from the scattering plate 32 at the outermost position. For each scattered light L ₀ , the optical path at the rotation position of the optical scanning unit 60 at time t1 (solid line) and time t2 (dashed line) is shown. At both time t1 and time t2, the half value half width of the incident light L ₁ illuminates the hologram 10 so as to form an angle Δθ with respect to the reproduction incident direction L _1c . The illumination light L ₁ illuminates the hologram 10 while moving over time between the optical path at time t1 indicated by a solid line and the optical path at time t2 indicated by a broken line.

As shown in FIG. 8, the reproduced image reproduced by the hologram 10 is positioned so as to illuminate the entire image forming region 41 of the light modulation element 40 via the Fourier transform lens 31. In FIG. 8, the image forming area 41 of the light modulation element 40 is two-dimensionally located in the XY plane. Further, the reproduced image reproduced by the hologram 10 is illuminated by overlapping the image forming region 41 of the light modulation element 40 by scanning the illumination light L ₁ by the light scanning unit 60. Therefore, the reproduction image by the hologram 10 is formed by the reproduction light L ₂ that is illuminated at different angles in time.

The light modulation element 40 such as a micro display is illuminated by the reproduction light L ₂ from the hologram 10 and transmits the reproduction light for each pixel to form an image. The reproduction light L ₂ modulated by the light modulation element 40 is magnified by the projection optical system 53 (configured by the projection lens 53 a and the diaphragm 53 _b in the present embodiment), projected onto the screen 54 as the video reproduction light L ₃ , reflected, Alternatively, the viewer is allowed to observe the transmitted image. At this time, the coherent light projected on the surface of the screen 54 interferes with each other to cause speckle. However, in this embodiment, since the scattered light L ₀ is scanned by the light scanning unit 60, the image reproduction light L ₃ projected on the screen 54 is changed as a result, and this speckle is very effectively conspicuous. It is lost.

For example, at point P1 on the screen 54 shown in FIG. 8, the video reproduction light L ₃ at time t1 (t1), the image reproducing light L ₃ (t2) is at time t2, it is illuminated at a different angle of incidence It becomes. In the figure, the angular difference between the video reproduction light L ₃ at time t1 and time t2 is indicated by C. It is the same in other respects without other point P2 and shown as shown in FIG, video playback light L ₃ projects the image onto the screen 54 while temporally changing the incident angle. Therefore, the speckles formed on the screen 54 in an extremely short time are averaged by the image reproduction light L ₃ being irradiated at different incident angles depending on the time, and an observer who observes the image projected on the screen 54 It becomes inconspicuous enough.

The projection type image display apparatus 2 according to the embodiment of the present invention has been described above. The scanning by the optical scanning unit 60 used in the projection type image display apparatus 2 is either one-dimensional or two-dimensional scanning. May be used. In the case of one-dimensional scanning, the optical scanning unit 60 is periodically rotated around one rotation center Ra to form an irradiation area on the line on the hologram 10. On the other hand, when scanning two-dimensionally, the optical scanning unit 60 is periodically rotated about two rotation centers Ra, and a planar irradiation region is formed on the hologram 10. In either case, the reproduction light L ₂ emitted from the hologram 10 irradiates the image forming region 41 of the light modulation element 40 in a planar shape.

  As described above, according to the projection display apparatus 2 of the present embodiment, it is possible to obtain illumination light with reduced illuminance unevenness and speckle noise even when using a hologram configured by periodically arranging element holograms. It is possible to display an image in which is not conspicuous.

  Note that the present invention is not limited to these embodiments, and embodiments configured by appropriately combining the configurations of the respective embodiments also fall within the scope of the present invention.

DESCRIPTION OF SYMBOLS 1 ... Hologram reproduction apparatus 2 ... Projection type image display apparatus 10 ... Hologram 11 ... Element hologram 20 ... Fourier transform lens 21i ... Reconstructed image 22 ... Bright point center 30 ... Light source 31 ... Laser light source part 32 ... Scattering plate 33 ... Optical fiber 34 ... Lens array 40 ... Light modulation element 41 ... Image forming area 51 ... First lens 52 ... Second lens 53 ... Projection optical system 54 ... Screen 60 ... Optical scanning unit

Claims (10)

In a hologram reproducing method for reproducing a hologram configured by periodically arranging element holograms,
An angle Δθ formed by a line segment formed with a half width at half maximum of illumination light incident on a certain point on the hologram and a reproduction incident direction of the hologram satisfies the following conditional expression (1): Yes Hologram playback method.
Δθ ≧ λ / 2p (1)
However,
λ is the wavelength of the illumination light,
p is the size of one side of the element hologram The hologram reproduction method according to claim 1, wherein the angle Δθ satisfies the following conditional expression (2).
Δθ ≦ 5λ / p (2) A hologram constructed by periodically arranging element holograms;
A light source for illuminating the hologram with illumination light,
An angle Δθ formed by a line segment formed with a half width at half maximum of illumination light incident on a certain point on the hologram and a reproduction incident direction of the hologram satisfies the following conditional expression (1): Hologram playback device.
Δθ ≧ λ / 2p (1)
However,
λ is the wavelength of the illumination light,
p is the size of one side of the element hologram The hologram reproducing apparatus according to claim 3, wherein the angle Δθ satisfies the following conditional expression (2).
Δθ ≦ 5λ / p (2) The light source has a laser light source part and a scattering element,
The hologram reproducing apparatus according to claim 3, wherein the scattering element imparts an angular distribution to the coherent light emitted from the laser light source unit and emits the illumination light as illumination light. The light source has a laser light source unit and a plurality of optical fibers,
The hologram reproducing apparatus according to claim 3, wherein the optical fiber gives an angular distribution to coherent light emitted from the laser light source unit and emits the illumination light as illumination light. The light source has a laser light source unit and a lens array,
The hologram reproducing apparatus according to claim 3, wherein the lens array imparts an angular distribution to coherent light emitted from a laser light source unit and emits the illumination light as illumination light. A light source that emits illumination light;
The optical scanning unit that scans illumination light emitted from the light source; and
A light modulation element having an image forming region on which an image is formed;
Comprising element holograms arranged periodically, diffusing illumination light scanned by the optical scanning unit, and reproducing light emitted from each point to illuminate the image forming region in an overlapping manner,
An angle Δθ formed by a line segment formed with a half width at half maximum of illumination light incident on a certain point on the hologram and a reproduction incident direction of the hologram satisfies the following conditional expression (1): Yes Projection display device.
Δθ ≧ λ / 2p (1)
However,
λ is the wavelength of the illumination light,
p is the size of one side of the element hologram The projection display apparatus according to claim 8, wherein the angle Δθ satisfies the following conditional expression (2).
Δθ ≦ 5λ / p (2) The projection display apparatus according to claim 8, wherein the angle Δθ satisfies the following conditional expression (3).
Δθ ≦ θ ₀ (3)
However,
θ ₀ is the angular width for viewing the short side of the image forming area from one point on the hologram

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