JP2011040537A - Image forming apparatus, and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a spontaneous light emitting type image forming apparatus which is simple and compact, and can reduce speckle noise by using a random laser with low coherence. <P>SOLUTION: The image forming apparatus includes: an image formation section 10A including a laser medium 12 which is divided in a plurality of dot regions 11 and causes induced emission as the inside of each of the dot regions 11 is irradiated with excitation light L1, and particulate light scattering members 13 which are dispersed in the laser medium 12 to scatter the excitation light L1; a light source for irradiating the laser medium 12 with the excitation light L1; and a scanning means of scanning the top of the image formation section 10A with the excitation light L1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image forming apparatus and a projector.

  Conventionally, in a projector, a discharge lamp such as an ultra-high pressure mercury lamp is generally used as a light source. However, this type of discharge lamp has problems such as a relatively short life, difficult to light instantaneously, a narrow color reproducibility range, and ultraviolet light emitted from the lamp deteriorates the liquid crystal light bulb. Therefore, a projection-type image display apparatus using a laser light source that emits monochromatic light as a high-output light source to replace the discharge lamp has been proposed.

  Examples of laser light source devices that can obtain high-power laser light include laser light source devices having an external resonator structure. In such a laser light source device, the use of an external resonator enhances light of a specific wavelength and obtains high-power laser light.

  However, when such a laser light source is applied as a light source for a projector, it is possible to solve the problem of increasing the output of the light source. There is a case where a phenomenon called so-called speckle occurs in a pattern. Thus, in order to realize a projector that displays a clear image using a laser light source, it is necessary to take measures against speckle noise.

  Speckle noise is a phenomenon caused by the coherence of laser light. Therefore, a measure for reducing the coherence of laser light is effective for reducing speckle noise. The coherence is generally inversely proportional to the output spectrum width of the laser beam. Since the coherence decreases as the output spectrum width increases, speckle noise can be reduced by increasing the spectrum width. Alternatively, since the speckle noise pattern generated differs between laser beams having different wavelengths, the speckle noise can be reduced by spatially superimposing them.

  As a laser light source device that emits such laser light, specifically, in an arrayed light source in which a plurality of light emitting elements are arranged two-dimensionally, the entire spectral width is widened by shifting the output wavelength of each light emitting element, There has been proposed an apparatus that suppresses the occurrence of speckle noise by reducing the coherence between laser beams emitted from a plurality of light emitting elements (see, for example, Patent Document 1). However, the method disclosed in Patent Document 1 has problems such as complicated optical systems and increased light source costs.

  In addition, unlike the configuration in which low coherence is realized by the method of increasing the number of light sources as described above, a random laser has been proposed as laser light whose output light itself has low coherence (see, for example, Patent Document 2). ). A normal laser light source amplifies light by two resonant mirrors and outputs laser light as described above, so that light having a specific mode and a long coherence length is obtained as laser light, whereas a random laser is Does not have a resonator.

  As shown in Patent Document 2, a random laser can be obtained by irradiating a laser medium in which fine particles are scattered with excitation light. The random laser oscillation mechanism is a “non-resonant type” in which a specific wavelength is selectively amplified by repeating multiple scattering of incident light in the medium by fine particles, and a ring-shaped resonator is formed with specific fine particles and incident. Although it is considered that there is a “resonance type” in which light resonates, it has been found that the output laser light has low coherence in time and space.

  The oscillation spectrum width of the obtained light is said to hold the relationship of “normal laser” <“random laser” <“light emitted from the LED”. That is, the random laser has a wider spectrum width than that of a normal laser beam, but does not have a wider oscillation spectrum width than the light emitted from the LED, and can be used as a monochromatic light source.

JP-T-2004-503923 JP 2003-332664 A

  Conventionally, application development to reduce speckle has been carried out using a laser light source that emits laser light with a uniform polarization direction, so most of the currently used technologies have a uniform polarization direction. It is assumed that normal laser light is used. Therefore, the use of laser light having a low coherence and high output, such as a random laser, has not been developed, and an application utilizing characteristics not found in conventional laser light is expected.

  The present invention has been made in view of such circumstances, and a self-luminous image capable of reducing speckle noise with a simple and small configuration by using a random laser having low coherence. An object is to provide a forming apparatus. It is another object to provide a projector including such an image forming apparatus.

In order to solve the above problems, an image forming apparatus according to the present invention includes a laser medium that is divided into a plurality of dot areas, and that emits stimulated emission when each of the dot areas is irradiated with excitation light. An image forming unit having a particulate light scattering member that is dispersed in a medium and scatters the excitation light, a light source that irradiates the laser medium with excitation light, and scanning the excitation light on the image formation unit And a scanning means.
According to this configuration, when the image forming unit is irradiated with excitation light, the excitation light is irregularly scattered by the light scattering member dispersed in the laser medium, and is amplified by the laser medium in the process of scattering. appear. Such a random laser has a broad spectrum width and low coherence compared to a laser beam emitted from a laser light source having a normal resonator structure having a resonance mirror. Therefore, the image light obtained by scanning the image forming unit with excitation light is low in coherence, so that it is difficult to generate speckle, and it is possible to form an image in which generation of speckle is suppressed while being high-power laser light. A possible image forming apparatus can be obtained.

In the present invention, it is desirable that the light scattering members included in each of the plurality of dot regions have different particle diameters.
It is known that the oscillation wavelength of a random laser changes depending on the particle diameter of the light scattering member in the laser medium (see, for example, S. Gottarodo, et al., Nature Photonics, 2, 429 (2008)). . Therefore, by varying the particle diameter of the light scattering member for each dot region, it becomes possible to vary the oscillation wavelength of the output light emitted for each dot region, and using light having such a different oscillation wavelength. By forming an image in this way, it is possible to provide an image forming apparatus capable of forming an image in which the generation of speckles is further suppressed.

  Here, since the particle | grain shape of the light-scattering member used normally is irregular shape, it cannot express a particle diameter quantitatively like a sphere or a cube. Therefore, in the present invention, the “particle diameter” refers to the value of the particle diameter of the light scattering member measured based on various measurement methods (theories). For example, when the “particle diameter” of a light scattering member is measured using a laser diffraction scattering method, the diameter (effective diameter) of spherical particles calculated to show the same diffraction pattern is used as the particle diameter. The above-described effects can be obtained when the particle diameter obtained in this way is different for each dot region.

In the present invention, it is desirable that the particle diameters are different in adjacent dot regions.
According to this configuration, since the oscillation wavelengths emitted from adjacent dot regions are different, it is possible to reliably suppress speckle generation by superimposing different speckle patterns depending on the wavelengths emitted from adjacent dot regions. it can.

In the present invention, it is preferable that the light source temporally changes the energy of the excitation light while the scanning unit scans the image forming unit once.
It is known that random lasers have different oscillation spectrum widths depending on the energy of excitation light (see, for example, H. Cao, et al., Phys. Rev. Lett., 82, 2278 (1999)). For this reason, it is possible to change the oscillation spectrum width of the output light temporally by changing the energy of the excitation light temporally.

  Using this, when the energy of the excitation light is temporally changed while the image forming unit is scanned once by the scanning unit and an image for one screen is formed, the energy of the excitation light is changed according to the change in the energy of the excitation light. An image for one screen is formed using light having different spectral widths, and an image forming apparatus capable of forming an image in which speckle generation is further suppressed can be obtained.

In the present invention, it is desirable that the energy of the excitation light to be irradiated is different between adjacent dot regions.
According to this configuration, since the oscillation spectrum widths emitted from the adjacent dot regions are different, it is possible to reliably suppress the generation of speckles by superimposing different speckle patterns emitted from the adjacent dot regions.

In the present invention, it is desirable that a light-heat conversion layer that absorbs the light and converts it into heat overlaps with a part of the plurality of dot regions.
According to this configuration, in the dot region provided with the photothermal conversion layer, the photothermal conversion layer generates heat by absorbing excitation light, for example, and the laser medium is heated. Then, since the refractive index of the laser medium changes, the optical path length in the laser medium changes and the resonator length changes. As a result, the wavelength that can resonate in the resonator changes, and the oscillation wavelength of the output light shifts. By forming an image using light having such different oscillation wavelengths, an image forming apparatus capable of forming an image in which generation of speckles is further suppressed can be obtained.

In the present invention, it is desirable to have a plurality of the light-to-heat conversion layers, and the plurality of light-to-heat conversion layers are arranged so as to be provided on one side and not on the other in the adjacent dot regions. .
According to this configuration, since the laser medium temperatures of the adjacent dot regions are different, the oscillation wavelengths of the emitted light are different. Therefore, generation of speckles can be reliably suppressed by superimposing different speckle patterns depending on wavelengths emitted from adjacent dot regions.

In the present invention, it is desirable that a collimating optical system is disposed on the output side of the output light from the laser medium in the image forming unit.
Random laser (output light) is emitted with an isotropic emission direction because it is triggered by the scattering of excitation light by the light scattering member. Therefore, by transmitting the output light through the collimating optical system provided on the exit side, the output direction of the output light can be aligned in one direction, and speckle generation can be suppressed and high-quality image formation can be achieved. .

In the present invention, it is preferable that a collimating lens that overlaps each of the dot regions is provided on a surface on the emission side of the output light in the image forming unit.
According to this configuration, output light emitted from each dot region can be efficiently received and effectively used for image formation, so that speckle generation is suppressed and high-quality image formation is possible. An image forming apparatus can be obtained.

In the case where the image forming apparatus of the present invention is a transmissive image forming apparatus in which excitation light is incident from one surface of the image forming unit and output light is emitted from the other surface, the excitation in the image forming unit is performed. It is desirable that a wavelength selection layer that transmits the excitation light and reflects the output light from the laser medium is provided on a light incident side surface.
According to this configuration, since the wavelength selection layer transmits the excitation light, the laser medium can be reliably irradiated with the excitation light to generate a random laser. In addition, out of the isotropically emitted output light, the light emitted to one surface side of the image forming unit is reflected to the other surface side of the image forming unit, so that all of the generated output light is good. Can be ejected from the other surface. Therefore, it is possible to obtain a transmissive image forming apparatus that has high light utilization efficiency and suppresses speckle generation.

In the case where the image forming apparatus of the present invention is a reflection type image forming apparatus in which excitation light is incident from one surface of the image forming unit and output light is emitted from the other surface, the image forming unit It is desirable that a reflection member for reflecting the output light from the laser medium is provided on the surface opposite to the incident side of the excitation light.
According to this configuration, out of the isotropically emitted output light, the light emitted to the other surface side of the image forming unit is reflected to the one surface side of the image forming unit, and thus generated output light. All of the above can be satisfactorily emitted from one surface, and a reflective image forming apparatus with high light utilization efficiency and reduced speckle generation can be obtained.

In the present invention, the reflection member is preferably a wavelength selection layer that transmits the excitation light and reflects the output light.
According to this configuration, it is possible to suppress a problem that unnecessary excitation light is reflected after the output light is generated and is emitted from one surface or stimulated emission of a useless random laser.

In the present invention, it is desirable that the adjacent dot regions are divided by a light-shielding partition.
According to this configuration, it is possible to suppress a problem that the isotropically emitted output light is incident on an adjacent dot region and stimulated emission of a useless random laser is performed. The light shielding property may be achieved by either absorption or reflection of light.

In the present invention, it is desirable to arrange a laser medium having a different wavelength of output light for each dot region.
According to this configuration, the type and arrangement of the laser medium are selected as appropriate, and, for example, by arranging dot regions that emit light of red (R), green (G), and blue (B) wavelengths, full-color display is achieved. A possible image forming apparatus can be obtained.

According to another aspect of the invention, a projector includes the above-described image forming apparatus and a projection optical system that projects light formed by the image forming apparatus.
According to this configuration, by providing the light source device described above, it is possible to provide a projector that has high output and suppresses speckle generation.

1 is a schematic perspective view showing an image forming apparatus according to a first embodiment of the present invention. FIG. 3 is a partial cross-sectional view of an image forming unit provided in the image forming apparatus according to the first embodiment. It is a schematic perspective view which shows the image forming apparatus which concerns on 2nd Embodiment of this invention. It is a fragmentary sectional view of an image forming part with which an image forming device of a 2nd embodiment is provided. It is a schematic perspective view which shows the image forming apparatus which concerns on 3rd Embodiment of this invention. It is a fragmentary sectional view of the image forming part with which the image forming device of a 3rd embodiment is provided. It is a schematic perspective view which shows the image forming apparatus which concerns on 4th Embodiment of this invention. It is a schematic perspective view which shows the image forming apparatus which concerns on 5th Embodiment of this invention. It is a fragmentary sectional view of the image forming part with which the image forming device of a 5th embodiment is provided. It is a schematic perspective view which shows the modification of the image forming apparatus of 5th Embodiment. It is a schematic perspective view which shows the image forming apparatus which concerns on 6th Embodiment of this invention. It is a schematic perspective view which shows the modification of the image forming apparatus of 6th Embodiment. It is explanatory drawing which shows the projector which concerns on this invention. It is explanatory drawing which shows the projector which concerns on this invention. It is explanatory drawing which shows the projector which concerns on this invention. It is explanatory drawing which shows the projector which concerns on this invention.

[First Embodiment]
The image forming apparatus 1 according to the first embodiment of the present invention will be described below with reference to FIGS. In all the drawings below, the dimensions and ratios of the constituent elements are appropriately changed in order to make the drawings easy to see.

  FIG. 1 is a schematic perspective view showing an image forming apparatus 1 of the present embodiment. As shown in the figure, an image forming apparatus 1 includes an image forming unit 10, a laser light source 20 that emits excitation light L1 that is laser light, and a scanning optical system (scanning unit) that scans the laser beam on the image forming unit 10 to draw an image. ) 30.

  The image forming unit 10A has a plurality of dot regions 11 formed in a matrix. The laser medium irradiated with the excitation light L1 emits a random laser L2 by performing stimulated emission. It is the composition to do. The configuration of the image forming unit 10A will be described in detail later.

  Although the detailed structure of the laser light source 20 is not shown, the laser light source 20 is a laser light source 20 having a semiconductor laser element that emits the excitation light L1. As the laser light source 20, for example, a normal YAG (Yttrium Aluminum Garnet) laser can be used. The excitation light L1 is coherence light with high coherence, and is emitted as a substantially complete plane wave.

  The scanning optical system 30 includes a first deflection mirror 30a that changes the optical axis of the excitation light L1 in the sub-scanning direction on the surface of the image forming unit 10A, and the optical axis of the excitation light L1 on the surface of the image forming unit 10A. And a second deflecting mirror 30b that is changed in the scanning direction. For example, the main scanning direction is a horizontal direction in the image forming unit 10, and the sub-scanning direction is a vertical direction orthogonal to the horizontal direction in the image forming unit 10.

  As the scanning optical system 30, a configuration in which a micro mechanical mirror formed by a MEMS technique or the like is used for the first deflection mirror 30a and a galvano mirror or the like is used for the second deflection mirror 30b can be exemplified. Further, the figure shows a state in which the scanning optical system 30 is configured by two mirrors, but, for example, two drive shafts are set for one mirror, and a single MEMS can perform two-dimensional scanning. A mirror may be used. The scanning optical system 30 scans the excitation light L1 in the main scanning direction and the sub scanning direction to form a display image.

  Further, a collimating optical system and a relay optical system may be arranged on the optical path from the laser light source 20 to the scanning optical system 30 as necessary. The collimating optical system and the relay optical system may be composed of a single lens or a plurality of lenses.

  FIG. 2 is an explanatory diagram of the image forming unit 10A, and is a partial cross-sectional view taken along line A-A ′ of FIG. As shown in the figure, the image forming unit 10A has a plurality of dot regions 11 divided by a partition wall 19. In each dot region, a laser medium 12 sandwiched between a pair of substrates 14 and a laser medium 12 And a light scattering member 13 dispersed in the substrate. A wavelength selection layer 15 is provided on the surface of the substrate 14 on the incident side of the excitation light L1.

  As the laser medium 12, a generally known amplification medium that stimulates and emits laser light can be used. The laser medium that can be used may be a solid such as a semiconductor polymer or a liquid such as a solution of a laser dye.

As the light scattering member 13, for example, fine particles of titanium oxide (TiO ₂ ) or zinc oxide (ZnO), glass beads, or the like can be used. As the particle diameter of the light scattering member 13, a particle diameter of about several nm to several μm can be suitably used.

  Here, since the particle shape of the light-scattering member is usually irregular, the particle diameter cannot be expressed quantitatively. Therefore, in the present invention, the “particle diameter” means, for example, the diameter (effective diameter) of a spherical particle calculated as showing the same diffraction pattern as that of the light scattering member to be measured when measuring using a laser diffraction scattering method. The average value (average particle diameter) is defined as the particle diameter. In the figure, the light scattering member 13 is shown as a circular particle and is shown as a circle. A light scattering member having a large diameter is indicated by reference numeral 13A and a light scattering member having a small diameter is indicated by reference numeral 13B.

  Other methods for measuring the particle size include known methods such as dynamic light scattering and centrifugal sedimentation. When comparing the particle size, the particle size obtained by the same measurement method (measurement theory) is used for comparison.

  The laser medium 12 in which the light scattering member 13 is dispersed is formed to have a thickness of several tens to several hundreds of μm using a coating method or the like because the excitation light L1 is difficult to reach the deep part if formed too thick. .

  In the figure, the plurality of dot regions 11 are distinguished by the difference in the average particle diameter of the light scattering members 13 included in the dot regions (illustrated by the difference in the ratio of the light scattering members 13A and 13B). 11B and 11C.

  The substrate 14 is provided by a light-transmitting forming material, such as a film made of polyethylene terephthalate (PET), polyethylene naphthalate (PEN), polycarbonate (PC), or the like as a light-transmitting property and flexibility. It is formed with the material which has.

  The wavelength selection layer 15 has wavelength selectivity that transmits the excitation light L1 and reflects the output light L2 emitted from the laser medium 12. Therefore, of the output light L2 emitted isotropically in the laser medium 12, the light returning to the incident side of the excitation light L1 can be reflected and emitted to the side opposite to the incident side of the excitation light L1.

  Such a wavelength selection layer 15 is formed using, for example, a dielectric multilayer film, and a desired wavelength selection is performed by appropriately selecting the number of multilayer films stacked, the thickness of each layer, the refractive index of the material forming each layer, and the like. It is possible to form it as a layer having the property.

  The partition wall 19 has a function of increasing the resolution by preventing the excitation light L1 and the generated output light L2 from entering the adjacent dot regions. In addition, when the laser medium 12 is a liquid, the light scattering member 13 is intended to remain in each dot region 11 so that the light scattering member 13 is uniformly distributed over the entire surface of the image forming unit 10A.

  As a material for forming the partition wall 19, for example, a black light absorbing material made of a light absorbing filler and a binder resin can be used. The filler absorbs excitation light or output light, and examples thereof include pigments such as carbon black and black pigment particles. As the binder resin, for example, a photocurable resin can be used. Using such a forming material, the partition walls 19 that divide the dot regions 11 can be formed by a commonly known photolithography method. In the present embodiment, the interval between the partition walls 19 (that is, the width of the dot region 11) is set to be several μm.

  The operation of the image forming apparatus 1 having the image forming unit 10A having such a configuration will be described with reference to FIGS.

  First, the excitation light L1 emitted from the laser light source 20 is scanned by the scanning optical system 30 and enters the specific dot region 11 of the image forming unit 10A. The excitation light L1 incident on the dot region 11 is irregularly scattered by the light scattering member 13 dispersed in the laser medium 12, is amplified by the laser medium 12 in the process of scattering, and oscillates a random laser (output light).

  The spectral width of the generated random laser depends on the material and particle diameter of the laser medium 12 and the light scattering member 13, but the specific wavelength is selectively selected by repeating multiple scattering of the excitation light in the medium by a plurality of light scattering members. In the case of the “non-resonant type” amplified to 3 to 4 nm, the width is about 0.2 nm in the case of the “resonant type” in which a ring-shaped resonator is formed by a specific light scattering member and the excitation light resonates. . A plurality of random lasers having such a spectral width are generated in a close wavelength band of about several nm as a whole. Note that such a random laser has a wider spectrum width and lower coherence than a laser composed of an ordinary resonant mirror.

  Furthermore, it is known that the oscillation wavelength of a random laser changes according to the particle diameter of the light scattering member 13 in the laser medium (for example, S. Gottarodo, et al., Nature Photonics, 2, 429 (2008 See)). Therefore, the output light L2a, L2b, and L2c having different oscillation wavelengths for each dot region is emitted by changing the particle diameter of the light scattering member 13 for each dot region (for example, the dot regions 11A, 11B, and 11C). Since the figure is a sectional view, the particle size of the light scattering member 13 is different for the dot regions 11 arranged in one direction (longitudinal direction), but they are also adjacent in the lateral direction not shown in the sectional view. The particle diameter of the light scattering member 13 is made different for each dot region.

  In general, speckle occurs mainly in a scene in which coherent light is irradiated onto an uneven surface. Assuming that the screen is irradiated with laser light, which is coherent light, the laser light that has reached the screen is scattered by unevenness on the screen surface and reaches the retina of the observer.

  At this time, the unevenness of the screen has a sufficiently large amplitude with respect to the wavelength of the laser beam, and gives random phase modulation from −π to π in the laser beam. Although these lights form an image on the retina, the laser beams that have undergone random phase modulation interfere with each other, resulting in interference fringes with very high contrast. This interference fringe is a defect that is called speckle and is observed.

  On the other hand, each of the output lights L2a, L2b, and L2c described above is a laser beam and has a wide spectrum width and low coherence, and the oscillation wavelengths of the output lights emitted from adjacent dot regions are different from each other. Therefore, the speckles can be reduced by superimposing different speckle patterns depending on the wavelength. Accordingly, speckle of the formed image is reduced.

  According to the image forming apparatus 1 configured as described above, speckle suppression is realized and high-quality image formation is possible.

  In the present embodiment, three types of dot regions 11A, 11B, and 11C having different particle diameters of the light scattering member 13 are shown. However, if the particle sizes of the light scattering members 13 in the adjacent dot regions are different, this is used. Not exclusively. For example, as shown in FIG. 1, when the dot regions 11 are formed in a matrix, two types of dot regions 11A and 11B having different particle diameters are arranged in a checkered pattern, so that the adjacent dot regions 11 Since output light having different oscillation wavelengths can be emitted, speckle can be reduced by superimposing different speckle patterns depending on the wavelengths emitted from adjacent dot regions.

  In addition, even if the light scattering member 13 having a single particle diameter is used without changing the particle diameter of the light scattering member 13, speckles can be reduced due to the property of a random laser having low coherence.

  In the present embodiment, the wavelength selection layer 15 is formed. However, even if the wavelength selection layer 15 is not provided, the image formation can be performed while suppressing the speckles although the light use efficiency is reduced. Is possible.

  In the present embodiment, the partition wall 19 is formed of a black forming material that absorbs light. However, the present invention is not limited to this. For example, a configuration in which output light generated in the dot region 11 on the wall surface of the partition wall 19 is reflected. It may be. Moreover, you may be the partition 19 which does not have light-shielding property.

[Second Embodiment]
3 and 4 are explanatory views of the image forming apparatus 2 according to the second embodiment of the present invention. The image forming apparatus 2 of the present embodiment is partially in common with the image forming apparatus 1 of the first embodiment. The difference is that the image forming apparatus is a reflection type image forming apparatus that receives excitation light from one surface of the image forming unit and emits output light from the other surface. Therefore, in this embodiment, the same code | symbol is attached | subjected about the component which is common in 1st Embodiment, and detailed description is abbreviate | omitted.

  FIG. 3 is a schematic perspective view showing the image forming apparatus 2 of the second embodiment, and corresponds to FIG. 1 of the first embodiment. The image forming unit 10B included in the image forming apparatus 2 is provided with the reflecting member 16 on the opposite side of the surface on the incident side of the excitation light L1, and the output light L2 emitted from the dot region 11 is the excitation light L1. The light is emitted from the same surface as the incident side surface to form an image.

  FIG. 4 is an explanatory diagram of the image forming unit 10B, is a partial cross-sectional view taken along line B-B ′ of FIG. 3, and corresponds to FIG. 2 of the first embodiment. As shown in the drawing, in the image forming unit 10B, a reflecting member 16 is provided on the surface of the substrate 14 opposite to the incident side of the excitation light L1.

  The reflection member 16 is a wavelength selection layer having wavelength selectivity that transmits the excitation light L1 and reflects the output light L2 emitted from the laser medium 12. Such a wavelength selection layer can be formed similarly to the wavelength selection layer of the first embodiment.

  The operation of the image forming apparatus 2 having the image forming unit 10B having such a configuration will be described with reference to FIGS. First, in the image forming apparatus 2, when the excitation light L1 enters the dot region 11, the output light L2 generated in the laser medium 12 is emitted isotropically. Among these, the light emitted to the side opposite to the incident side of the excitation light L1 is reflected by the reflecting member 16 and emitted to the incident side of the excitation light L1.

  Here, in the image forming apparatus 2, the output of the laser light source 20 is controlled by a control device (not shown), and the energy of the excitation light L1 is changed with time, whereby different energy is respectively applied to the dot regions 11A, 11B, and 11C. Excitation light L1a, L1b, and L1c are incident.

  It is known that random lasers have different oscillation spectrum widths depending on the energy of excitation light (see, for example, H. Cao, et al., Phys. Rev. Lett., 82, 2278 (1999)). For this reason, by varying the energy of the excitation light L1 with respect to time and entering excitation light having different energy for each dot region (for example, the dot regions 11A, 11B, and 11C), output of oscillation spectrum widths that differ for each dot region. Lights L2d, L2e, and L2f are emitted. Since the drawing is a cross-sectional view, the energy of the excitation light L1 is different for the dot regions 11 arranged in one direction (longitudinal direction), but the adjacent dot regions also in the horizontal direction not shown in the cross-sectional view. The energy of the excitation light L1 is varied every time.

  By controlling in this way, the above-described output lights L2d, L2e, and L2f emitted from the adjacent dot regions have a wide spectrum width while being each laser light, and furthermore, the spectrum width is different, so that the coherence is low. is there. Therefore, it is difficult to form a speckle pattern. Accordingly, speckle of the formed image is reduced.

  According to the image forming apparatus 2 configured as described above, speckle suppression is realized and high-quality image formation is possible.

  In the present embodiment, the excitation lights L1a, L1b, and L1c, which are different in energy, are shown as the excitation light L1, but the present invention is not limited to this. For example, two types of excitation light are alternately emitted from the laser light source 20. In other words, the two types of excitation light may be alternately incident on the dot region by making the switching between the two types of excitation light correspond to the scanning speed.

  In the present embodiment, the reflection member 16 is a wavelength selection layer, but it may be a metal film having light reflectivity using aluminum or the like as a raw material.

[Third Embodiment]
5 and 6 are explanatory diagrams of the image forming apparatus 3 according to the third embodiment of the present invention. The image forming apparatus 3 of the present embodiment is partially in common with the image forming apparatus 1 of the first embodiment. The difference is that a photothermal conversion layer that absorbs a part of the output light and converts it into heat is provided on the surface of the image forming unit on the side from which the output light is emitted. Therefore, in this embodiment, the same code | symbol is attached | subjected about the component which is common in 1st Embodiment, and detailed description is abbreviate | omitted.

  FIG. 5 is a schematic perspective view showing the image forming apparatus 3 of the third embodiment, and corresponds to FIG. 1 of the first embodiment. The image forming unit 10 </ b> C included in the image forming apparatus 3 is provided with a photothermal conversion layer, which will be described later, overlapping the dot region 11. In the figure, the dot region provided with the photothermal conversion layer is denoted by reference numeral 17 and is distinguished from the dot region 11 provided with no photothermal conversion layer. The dot areas 17 are randomly arranged.

  FIG. 6 is an explanatory diagram of the image forming unit 10 </ b> C, is a partial cross-sectional view taken along line C-C ′ in FIG. 5, and corresponds to FIG. 2 of the first embodiment. As shown in the figure, in the image forming unit 10C, a photothermal conversion layer 18 is provided on the surface of the substrate 14 on the emission side of the output light L2.

  The photothermal conversion layer 18 is provided for the purpose of forming a temperature distribution in the plane of the image forming unit 10C. That is, when part of the excitation light L1 and the output light L2 is absorbed and converted into heat by the photothermal conversion layer 18, the laser medium 12 in the dot region 17 provided with the photothermal conversion layer 18 is heated. Then, since the refractive index of the laser medium 12 changes, the optical path length in the laser medium 12 changes, the oscillation wavelength of the output light shifts, and output lights L2g, L2h, and L2i having different oscillation wavelengths are emitted.

  According to the image forming apparatus 3 configured as described above, an image can be formed by forming an image using output light having different oscillation wavelengths, thereby suppressing the generation of speckle. It can be.

  In the present embodiment, the photothermal conversion layer 18 is provided so as to correspond to the dot region. However, the present invention is not limited to this as long as the temperature distribution can be formed in the plane of the image forming unit 10C. For example, the photothermal conversion layer 18 may be provided across a plurality of dot regions, and both the portion where the photothermal conversion layer 18 is formed and the portion where the photothermal conversion layer 18 is not formed are included in one dot region. Also good.

  In this embodiment, the dot areas 17 are randomly arranged. For example, when the dot areas are formed in a matrix, photothermal conversion is performed in a checkered pattern corresponding to each dot area. The layer 18 may be provided, and the dot area 11 and the dot area 17 may be arranged in a checkered pattern. In this way, the temperature of the laser medium is always different between adjacent dot regions, and output light having different oscillation wavelengths is emitted, so that it is easy to reduce speckle.

  In the present embodiment, the photothermal conversion layer 18 is disposed on the output side of the output light L2, but may be disposed on the surface on the incident side of the excitation light L1. In that case, a photothermal conversion layer that absorbs a part of the excitation light L1 and converts it into heat can be used.

[Fourth Embodiment]
FIG. 7 is an explanatory diagram of the image forming apparatus 4 according to the fourth embodiment of the present invention. The image forming apparatus 4 is partially in common with the image forming apparatus 1 of the first embodiment. The difference is that for each dot region of the image forming unit 10D, a laser medium that emits red (R) laser light, a laser medium that emits green (G) laser light, and a laser medium that emits blue (B) laser light, It is to select and arrange appropriately.

  In the figure, in a dot area formed in a matrix, the dot area 11r that emits red laser light, the dot area 11g that emits green laser light, and the dot area 11b that emits blue laser light, Repeatedly arranged horizontally. In addition, the same color is arranged in the vertical direction in the order of red, green, and blue, forming a so-called stripe arrangement.

  According to the image forming apparatus 4 having such a configuration, the type and arrangement of the laser medium are selected as appropriate, and, for example, dot regions that emit light of red (R), green (G), and blue (B) wavelengths are arranged. By doing so, an image forming apparatus capable of full color display can be obtained.

[Fifth Embodiment]
8 to 10 are explanatory diagrams of the image forming apparatus 5 according to the fifth embodiment of the present invention. As shown in FIG. 8, in addition to the image forming apparatus 1 of the first embodiment, the image forming apparatus 5 is provided with a plurality of collimating lenses 40 overlapping the dot region 11 on the output surface of the output light L2 of the image forming unit. ing.

  FIG. 9 is an explanatory diagram of the image forming unit 10E, is a partial cross-sectional view taken along line E-E ′ of FIG. 8, and corresponds to FIG. 2 of the first embodiment. As illustrated, the image forming unit 10E includes a plurality of collimating lenses 40 on the substrate 14 on the output light L2 emission side.

  Since the random laser (output light) is generated when the excitation light L1 is scattered by the light scattering member 13, it is emitted with an isotropic emission direction. Therefore, by transmitting the output light L2 through the collimating lens 40 provided on the emission side, the emission direction of the output light L2 can be aligned in one direction. The collimating lens 40 can be formed, for example, by using a light curable resin having a light transmitting property and curing it by irradiating light in a state where the lens shape is transferred by embossing.

  According to the image forming apparatus 5 configured as described above, speckle generation is suppressed, light use efficiency is increased, and high-quality image formation is possible.

  In the present embodiment, the plurality of collimating lenses 40 that overlap each of the dot areas are provided. However, the present invention is not limited to this, and the collimating optical system may be provided at spatially separated positions. As long as the emitted output light can be received, the collimating optical system may be formed by a single or a plurality of optical members, and even if provided corresponding to each of the dot areas, It may be a large collimating optical system that receives the output light.

  In the present embodiment, a transmissive image forming apparatus is illustrated and described as the image forming apparatus 5. However, in addition to the image forming apparatus 2 of the second embodiment, as shown in FIG. The reflective image forming apparatus 6 may include the image forming unit 10 </ b> F in which a plurality of collimating lenses 40 that overlap the dot region 11 are provided on the light emission surface of the light L <b> 2.

  According to this configuration, the excitation light L1 enters the dot region 11 via the collimator lens 40, but no difference occurs in the generated output light due to the difference in the incident angle with respect to the dot region 11. That is, if the excitation light is incident on the laser medium in which the light scattering member is dispersed in the dot region 11, the random laser is emitted while being scattered inside. As long as L1 is incident, it is possible to provide an image forming apparatus capable of suppressing speckle generation and forming a high-quality image.

[Sixth Embodiment]
11 and 12 are explanatory views of an image forming apparatus according to the sixth embodiment of the present invention. As shown in FIG. 11, the image forming apparatus 7 is partially in common with the image forming apparatus 5 of the fifth embodiment shown in FIG. The image forming apparatus 7 is a one-dimensional image forming apparatus that forms an image by swinging both the image forming unit 10G having a width corresponding to one line of the dot region and the scanning optical system 30 in different directions.

  In the image forming apparatus 7, the image forming unit 10 </ b> G is configured to have a width corresponding to one line of the dot region 11, and can swing around the drive shaft extending in the arrangement direction of the dot region 11, and the output light The optical axis of L2 is changed in the sub scanning direction. Further, the scanning optical system 30 has a drive axis in a direction orthogonal to the swing axis of the image forming unit 10G, and changes the optical axis of the excitation light L1 in the main scanning direction.

  According to the image forming apparatus 7 configured as described above, since the image forming unit 10G has a size having a width corresponding to one line of the dot region 11, it is possible to suppress the generation of speckles and reduce the size of the image forming apparatus. be able to.

  As in the fifth embodiment, in the present embodiment, as shown in FIG. 12, a plurality of image forming units 7 that overlap the dot region 11 on the incident surface of the excitation light L1 of the image forming unit are used. A reflective image forming apparatus 8 having an image forming unit 10H provided with a collimating lens 40 may also be used.

  Also in the image forming apparatus of the present embodiment, full-color display is possible by repeatedly arranging dot areas that emit red, green, and blue laser light in the dot area for one line.

[projector]
Next, an embodiment of the projector of the present invention will be described. 13 to 16 are explanatory diagrams of a projector having the above-described image forming apparatus.

  A projector 101 shown in FIG. 13 includes image forming apparatuses 1R, 1G, and 1B according to the first embodiment that form red, green, and blue images by including laser media that emit red, green, and blue laser beams, respectively. And a dichroic prism 50 that synthesizes the images formed by the image forming apparatuses, and a projection lens 60 (projection optical system) that enlarges and projects the synthesized image onto the screen 70.

  The projector 102 shown in FIG. 14 includes the image forming apparatus 4 according to the fourth embodiment capable of full color display, and a projection lens 60.

  The projector 103 shown in FIG. 15 includes laser media that emit red, green, and blue laser beams, thereby forming red, green, and blue images, respectively, and the one-dimensional image forming apparatuses 8R and 8G of the sixth embodiment. , 8B, a dichroic prism 50, and a projection lens 60.

  The projector 104 shown in FIG. 16 includes the image forming apparatus 8 according to the sixth embodiment capable of full-color display and the projection lens 60.

  Since these projectors all have the above-described light source device, an image is formed by a random laser having low coherence. Therefore, it is possible to obtain a projector with high output and suppressed speckle generation.

  The preferred embodiments of the present invention have been described above with reference to the accompanying drawings, but it goes without saying that the present invention is not limited to such examples. Various shapes, combinations, and the like of the constituent members shown in the above-described examples are examples, and various modifications can be made based on design requirements and the like without departing from the gist of the present invention.

  For example, in the above-described embodiment, the transmission type image forming apparatus or the reflection type image forming apparatus has been described. However, these can be interchanged by appropriately providing the wavelength selection layer 15 or the reflection member 16. .

DESCRIPTION OF SYMBOLS 1-8 ... Image forming apparatus 10, 10A-10H ... Image forming part, 11, 17 ... Dot area, 12 ... Laser medium, 13, 13A, 13B ... Light scattering member, 15 ... Wavelength selection layer, 16 ... Reflective member DESCRIPTION OF SYMBOLS 18 ... Photothermal conversion layer, 19 ... Partition, 20 ... Light source, 30 ... Scanning optical system (scanning means), 40 ... Collimating lens (collimating optical system), 60 ... Projection lens (projection optical system), 101-014 ... Projector L1, L1a to L1c ... excitation light, L2, L2a to L2i ... output light,

Claims (15)

A laser medium that is divided into a plurality of dot areas, and in which each of the dot areas generates stimulated emission when irradiated with excitation light, and particulate light scattering that is dispersed in the laser medium and scatters the excitation light An image forming unit having a member;
A light source for irradiating the laser medium with excitation light;
A scanning unit that scans the excitation light on the image forming unit.   The image forming apparatus according to claim 1, wherein the light scattering members included in each of the plurality of dot regions have different particle diameters.   The image forming apparatus according to claim 2, wherein the particle diameters of the adjacent dot regions are different.   4. The image according to claim 1, wherein the light source temporally changes the energy of the excitation light while the image forming unit is scanned once by the scanning unit. 5. Forming equipment.   The image forming apparatus according to claim 4, wherein the energy of the excitation light irradiated differs between the adjacent dot regions.   6. The image formation according to claim 1, further comprising a light-to-heat conversion layer that overlaps a part of the plurality of dot regions and absorbs the light and converts the light into heat. apparatus.   The plurality of light-to-heat conversion layers are provided, and the plurality of light-to-heat conversion layers are arranged so as to be provided on one side and not on the other in the adjacent dot regions. The image forming apparatus described in 1.   8. The image forming apparatus according to claim 1, wherein a collimating optical system is disposed on the output side of the output light from the laser medium in the image forming unit. 9.   The image forming apparatus according to claim 8, wherein a collimating lens that overlaps each of the dot regions is provided on a surface on the emission side of the output light in the image forming unit.   10. The wavelength selection layer that transmits the excitation light and reflects the output light from the laser medium is provided on a surface on the incident side of the excitation light in the image forming unit. The image forming apparatus according to claim 1.   10. The reflecting member for reflecting output light from the laser medium is provided on a surface opposite to the incident side of the excitation light in the image forming unit. The image forming apparatus described in the item.   The image forming apparatus according to claim 11, wherein the reflection member is a wavelength selection layer that transmits the excitation light and reflects the output light.   The image forming apparatus according to claim 1, wherein the adjacent dot regions are divided by a light-shielding partition.   The image forming apparatus according to claim 1, wherein a laser medium having a different wavelength of output light is arranged for each dot region.   15. A projector comprising: the image forming apparatus according to claim 1; and a projection optical system that projects light formed by the image forming apparatus.

Images