WO2020194850A1 - Speckle noise reduction optical system - Google Patents

Speckle noise reduction optical system Download PDF

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Publication number
WO2020194850A1
WO2020194850A1 PCT/JP2019/044685 JP2019044685W WO2020194850A1 WO 2020194850 A1 WO2020194850 A1 WO 2020194850A1 JP 2019044685 W JP2019044685 W JP 2019044685W WO 2020194850 A1 WO2020194850 A1 WO 2020194850A1
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Prior art keywords
speckle noise
optical system
noise reduction
reduction optical
integrator
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PCT/JP2019/044685
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French (fr)
Japanese (ja)
Inventor
弘充 森
川村　友人
寿行 高岩
駿 檜山
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日立化成株式会社
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Publication of WO2020194850A1 publication Critical patent/WO2020194850A1/en

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    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B27/00—Optical systems or apparatus not provided for by any of the groups G02B1/00 - G02B26/00, G02B30/00
    • G02B27/48—Laser speckle optics
    • G—PHYSICS
    • G02—OPTICS
    • G02B—OPTICAL ELEMENTS, SYSTEMS OR APPARATUS
    • G02B5/00—Optical elements other than lenses
    • G02B5/02—Diffusing elements; Afocal elements

Definitions

  • the present invention relates to a technique for reducing speckle noise of laser light.
  • Patent Document 1 As a method for reducing speckle noise, a method using a polygonal rod is proposed in Patent Document 1, and a method using Mie scattering is proposed in Patent Document 2.
  • Patent Document 1 describes a method of spatially multiplexing speckle noise patterns by utilizing the fact that the reflection angle of laser light changes with rotation on the inner surface of a polygonal rod.
  • Patent Document 2 describes a method of spatially multiplexing speckle noise patterns by perturbing a light reflection chamber and a light source that cause Mie scattering.
  • Patent Document 2 does not describe the point of using Mie scattering or the specific description of perturbing.
  • the light reflection chamber In order to make the light reflection chamber a mirror surface, it is necessary to polish the necessary surface if it is glass, which cannot be realized at low cost.
  • the necessary surface when injection molding is performed with resin, scratches remain on the side surface when it is taken out, so a complicated mechanism is required to make it mirror-finished, and it is not possible to perform inexpensive molding such as taking a large number of pieces at once, which is a cost issue.
  • one-dimensional random modulation is possible with a cantilever, microspring, etc. used for perturbation, but one-dimensional random modulation can approximate a sine wave and a time occurs when the movement of the laser beam stops.
  • An object of the present invention is to provide a low-cost, compact and quiet speckle noise reduction optical system in view of the above problems.
  • a preferred aspect of the present invention is a light source that emits a laser beam, an integrator that is at least partially filled with particles and is transparent to the laser beam, and a laser beam relative to the integrator at a speed greater than zero.
  • the speckle noise reduction optical system is characterized in that the laser beam travels inside the integrator and reduces the speckle noise of the laser beam emitted from the integrator.
  • FIG. 1 The perspective view of the speckle noise reduction optical system of Example 1.
  • Notations such as “first”, “second”, and “third” in the present specification and the like are attached to identify the components, and do not necessarily limit the number, order, or contents thereof. is not.
  • numbers for identifying components are used for each context, and numbers used in one context do not always indicate the same composition in other contexts. Further, it does not prevent the component identified by a certain number from having the function of the component identified by another number.
  • a light source that emits laser light, an integrator that is at least a transparent rod filled with particles, and the integrator or light source are always operated at a speed greater than zero. It is equipped with a vibrating part that vibrates minutely, and the laser light travels inside the integrator, and speckle noise is reduced by at least the particles colliding with the laser light multiple times.
  • FIG. 1 is a schematic view illustrating a speckle noise reduction optical system 100.
  • the speckle noise reduction optical system 100 includes a light source 1, an integrator 2, and vibration units 4 and 5.
  • the light source 1 is a light source that emits laser light, and emits laser light having a wavelength having a predetermined spectral width in the z direction.
  • an existing light source such as a laser diode can be used.
  • the integrator 2 is a polygonal column, for example, a quadrangular prism that is transparent to a laser beam, and particles 3 are dispersed therein at a predetermined density.
  • the particle 3 is a scattered particle that scatters the laser beam.
  • the vibrating units 4 and 5 have a function of vibrating the integrator 2.
  • the vibrating unit 4 has a function of vibrating in the x-axis direction
  • the vibrating unit 5 has a function of vibrating in the y-axis direction. Further, by making the phases of the vibration cycles of the vibrating units 4 and 5 different, the moving speed of the integrator 2 is set so as not to be zero at all times.
  • As the vibrating unit 4 and the vibrating unit 5 existing piezoelectric linear vibrating actuators and the like can be used.
  • the laser beam emitted from the light source 1 enters the integrator 2 from the left side in the figure, travels inside, and is emitted from the right side in the figure.
  • the incident surface is referred to as an incident surface
  • the exit surface is referred to as an exit surface
  • the other surfaces are referred to as side surfaces.
  • the laser beam traveling inside the integrator 2 collides with the particles 3 at a predetermined frequency and is scattered. Further, since the integrator 2 is operating in the vibrating units 4 and 5, when focusing on one ray of the emitted laser beam, the one ray of interest always emits at a different angle in a time of 50 msec or less. .. Therefore, the pattern due to speckle noise can be multiplexed.
  • the integrator of this embodiment is particularly limited as long as it has a structure in which a quadrangular prism is composed of a medium 1, has a refractive index different from that of the medium 1, and is filled with particles (medium 2) that scatter propagating light. There is no. It can be easily obtained by using the materials and manufacturing methods described below.
  • a material having high transparency is selected from the viewpoint of propagating light.
  • an acrylic photocurable resin is used, but the material is not particularly limited as long as it is a highly transparent material.
  • a photocurable resin When a photocurable resin is used, it is easy to mix with the solid medium 2 when it is used, and from the viewpoint of improving work efficiency because steps such as cooling and drying are not required after curing. It is more preferable from the viewpoint that it is easy to obtain an integrator having the shape of. Further, it is more preferable to use an acrylic material because the transmittance is high and the efficiency of light utilization can be improved.
  • the medium 2 can be efficiently obtained by mixing particles having a refractive index different from that of the medium 1 in the medium 1.
  • crosslinked polystyrene fine particles are used as the material of the medium 2, but other materials such as plastic particles and glass particles of other materials may be used as long as they are highly transparent materials.
  • the difference in refractive index between medium 1 and medium 2 is 0.025 or more.
  • the specific gravities of the medium 1 and the medium 2 can be easily brought close to each other, and the medium 2 can be easily mixed with the medium 1, and the decrease in efficiency can be suppressed. It is more preferable from the viewpoint that the effect of scattering can be easily obtained.
  • either of the refractive indexes may be larger.
  • the difference in refractive index in this embodiment is the difference between the refractive index of medium 1 or medium 2 having a high refractive index and the refractive index of medium 2 or medium 1 having a low refractive index among the medium 1 or medium 2. The value is calculated from.
  • the particle size of the medium 2 is preferably 1 ⁇ m or more and 5 ⁇ m or less. This is because, as described above, when the particle size is small, the light is scattered too much and the light extraction efficiency is lowered, and when the particle size is large, the light is hard to be scattered. Further, it is desirable that the particle size is substantially uniform, but there is no problem because the effect can be obtained if 90% or more of the particles are contained within the above particle size range.
  • a method of integrating the medium 1 and the medium 2 for example, there is a method of preparing a liquid medium 1, then mixing the medium 1 and the medium 2, and photocuring the medium 1 to a predetermined shape. It can also be manufactured by other methods such as pressing, injection molding, and shaving. Of these, a liquid medium 1 is more preferable because the medium 2 can be easily mixed, and a liquid medium 1 mixed with the medium 2 is more preferable because it can be easily processed into a predetermined shape. ..
  • a plate with the height of the product may be manufactured and then the outer circumference may be cut to make the product size, or a mold with a space of the product size may be manufactured, and resin may be poured into the mold and cured. You may.
  • the surface roughness (Ra; arithmetic mean roughness) of the integrator of this embodiment be reduced in the length direction of the side surface. This is because if the surface is rough in the length direction of the side surface when the light hits the side surface, the light exceeds the critical angle and escapes from the side surface. In the direction perpendicular to the length direction, the surface may be rough as long as the light propagation is not adversely affected. Further, since the light incident surface and the light emitting surface can be expected to have an effect of increasing the diffusion of light, the surfaces may be rough as long as the light emitting surface is not adversely affected.
  • the surface roughness of the side surface in the optical axis direction is preferably more than 0 ⁇ m to 2.0 ⁇ m, better if it is more than 0 ⁇ m to 1.0 ⁇ m, and even better if it is more than 0 ⁇ m to 0.5 ⁇ m.
  • the surface roughness of the light incident surface and the light emitting surface is equal to or higher than the surface roughness of the above side surface, and is preferably 0.01 ⁇ m to 10 ⁇ m, better is 0.5 ⁇ m to 5 ⁇ m, and is 0.5 ⁇ m to 3 ⁇ m. It is even better if it is.
  • the surface roughness in the direction perpendicular to the optical axis of the side surface is more than 0 ⁇ m, and the upper limit is equal to or less than the values listed in the above-mentioned surface roughness of the light incident surface and the light emitting surface.
  • the surface roughness in the direction perpendicular to the optical axis of the side surface is preferably small within the above range, but it may be arbitrarily selected from the viewpoint of processing efficiency.
  • the surface roughness in the cutting direction and the surface roughness in the direction substantially perpendicular to the cutting direction tend to be smaller than the surface roughness in the former cutting direction.
  • the cutting speed or the like is changed in order to improve the machining efficiency, the surface roughness in the direction substantially perpendicular to the cutting direction becomes rough. In this case, by setting the cutting direction to the optical axis direction, it is possible to maintain the light propagation efficiency while maintaining the work efficiency.
  • the surface roughness is transferred to the integrator.
  • the optical axis direction to the direction in which the surface roughness is small, it is possible to maintain good light propagation efficiency.
  • the unevenness formed by the convex portion due to the scattered particles made of the medium 2 protruding from the side surface and the concave portion formed by the trace of the scattered particles falling off from the side surface contributes to the surface roughness. If present, it contributes to the leakage of light from the side surface as described above.
  • the surface roughness (Ra) of the side surface is preferably 1/2 or less of the average particle size of the scattered particles introduced as the medium 2. This can be achieved by not projecting the scattered particles from the side surface of the integrator, or by cutting and smoothing the scattered particles projecting from the side surface.
  • FIG. 2 is a diagram showing the functions of the integrator 2.
  • the incident laser beam is scattered by the particles 3.
  • the collision between the laser beam and the particles occurs at a frequency of mean free path ⁇ L.
  • the laser beam traveling to the side surface is totally reflected by the difference in the refractive index and is confined inside the integrator 2.
  • a leakage loss occurs to the outside of the integrator 2.
  • the speckle noise reduction optical system 100 three indexes are important for averaging the speckle noise pattern.
  • the first is the declination ( ⁇ ) of an index indicating how much the emitted laser beam is bent by particle scattering.
  • the second is the mean free path ( ⁇ L), which is an index indicating the frequency of causing particle scattering.
  • the third is the efficiency (I out / I in ) that indicates how much the incident laser beam can be emitted.
  • FIG. 3 is a graph obtained by geometrically calculating the amount of eccentricity between the particles and the laser beam (horizontal axis) and the angle at which the particles and the laser beam are bent after they collide (vertical axis).
  • the left and right graphs are the same graphs with different scales on the vertical axis.
  • the four examples of the refractive index difference ( ⁇ N) between the medium 1 and the medium 2 are 0.01, 0.025, 0.05, and 0.1 are shown. The particles were calculated assuming that the diameter was 2 ⁇ m and the wavelength of the laser beam was 550 nm.
  • the average human pupil diameter is 7 mm, and if the light moves from one end to the other, the angle is set so that it can be recognized as a sufficiently different state. If the distance between the human and the image is set to 500 mm as a general condition, the angle is about 0.8 degrees, and if there is an angle of at least 1 degree or more, it can be considered that the person recognizes it as another pattern.
  • the eccentricity amount of 0.5 ⁇ m indicates a half value of the vibration width, and corresponds to the vibration amplitude of 1.0 ⁇ m. This amplitude corresponds to 50% of the particle diameter of ⁇ 2 ⁇ m.
  • vibration of 0.5 ⁇ m or less is assumed. It should be noted that a difference in refractive index of about 0.025 or more is required to give an argument of 1 degree with an eccentricity of 0.3 ⁇ m.
  • FIG. 4 is an example of calculating the density (horizontal axis) and the mean free path (vertical axis) of the particles 3 in the integrator 2.
  • the difference in refractive index four examples are shown as in FIG.
  • the mean free path decreases as the particle density increases. It can also be seen that the larger the difference in refractive index, the smaller the mean free path.
  • the mean free path requires at least one collision, so 5 mm or less is required.
  • the number of scatterings is preferably 10 or less, and the mean free path is preferably between 0.5 mm and 5 mm.
  • FIG. 5 shows the results of simulating the mean free path (horizontal axis) and efficiency (vertical axis).
  • the particle diameter is 2 ⁇ m
  • the refractive index difference is 0.05
  • the wavelength of the laser light is 550 nm
  • the emission farfield pattern (FFP) of the laser light is 15 degrees
  • the distance between the light source and the integrator is 0.5 mm
  • the incident surface of the integrator 2 is used.
  • the size of the exit surface was 1 ⁇ 1 mm and the length was 5 mm.
  • the mean free path is realized by changing the particle density. The Fresnel loss is not considered here.
  • the mean free path is 0.5 mm or more.
  • FIG. 6 illustrates the trajectory when the integrator 2 is vibrated by the vibrating units 4 and 5.
  • a circular orbit can be formed as shown in FIG. 6A.
  • the phase may be shifted by 45 degrees to 90 degrees to form an elliptical orbit as shown in FIG. 6 (b).
  • the orbits are made straight by synchronizing the phases as shown in FIG. 6C, the movement stops at the end, so that a speckle noise pattern is generated.
  • the amplitudes of the x-axis and the y-axis are 1 ⁇ m each, the particle 3 can be vibrated at 50% of the diameter of 2 ⁇ m.
  • the laser beam may be declinated 10 times or more and 1 degree or more within a time of 50 msec or less. In other words, it means that an argument of 1 degree or more should be given at least once at intervals of 5 msec or less.
  • the mean free path is 0.5 ⁇ m and the length of the integrator 2 is 5 mm, 10 collisions will occur. Therefore, it is sufficient that an argument of 1 degree or more can be obtained by 10 collisions. In other words, it suffices to obtain an argument of 0.1 degree each time.
  • the average free path should be 0.5 mm when the particle diameter is 2 ⁇ m and the refractive index difference is 0.025 or more and the length of the integrator is 5 mm. Therefore, the speckle noise pattern can be averaged 10 times, and an efficiency of 90% or more can be achieved. It can be said that the speckle noise reduction optical system 100 can efficiently reduce speckle by vibration outside the human audible range.
  • the particle size is 1 ⁇ m or more even if it is small. This is because the smaller the size, the higher the manufacturing difficulty, and the more expensive the particles. Further, when the particle diameter is increased, the emission angle accompanying the amount of eccentricity becomes smaller, so it is desirable to set the particle diameter to 5 ⁇ m or less.
  • the integrator 2 can always be operated. For this reason, it is possible to eliminate the residual speckle noise, which is a problem when the device is paused during slow operation.
  • the vibrating part may vibrate the laser beam and the integrator 2 relatively. Therefore, the vibrating unit may vibrate at least one of the laser beam and the integrator by at least one of the light source 1, the integrator 2, and the optical element inserted in the optical path between the light source and the integrator.
  • the optical element for example, an existing acoustic optical element can be used.
  • Example 2 will be described with reference to the drawings.
  • the speckle noise reduction optical system 200 which is a modification of the speckle noise reduction optical system 100, will be described.
  • FIG. 7 shows a schematic diagram of the speckle noise reduction optical system 200.
  • the speckle noise reduction optical system 200 is different in that the integrator 10 is provided in place of the integrator 2 of the speckle noise reduction optical system 100, and the vibration unit 11 is provided in place of the vibration units 4 and 5.
  • a cylinder such as the integrator 10 may be used instead of a polygonal prism.
  • the cylindrical integrator 10 is rotated by eccentricity of 0.5 ⁇ m or more in the x direction or the y direction. By doing so, the center of the integrator 10 can also be circularly moved as shown in FIG. 6A. If there is no eccentricity, the center of the integrator 10 will stop, and speckle noise will remain near the central axis.
  • the cylindrical integrator 10 is efficient because there is almost no time when the laser beam is not emitted. It can be said that the vibrating unit 11 can be easily realized by a small motor and gears, a belt or the like.
  • Example 3 will be described with reference to the drawings.
  • the speckle noise reduction optical system 300 which is a modification of the speckle noise reduction optical system 100, will be described.
  • FIG. 8 shows a schematic diagram of the speckle noise reduction optical system 300.
  • the speckle noise reduction optical system 300 is different in that light sources 21 to 23 are provided instead of the light source 1 of the speckle noise reduction optical system 100.
  • the light sources 21, 22, and 23 emit laser light having wavelengths corresponding to red, green, and blue.
  • the speckle noise reduction optical system 300 not only reduces the speckle noise of the laser beam, but also has the effect of making the laser beam emitted from the light sources 21, 22, and 23 uniform by scattering.
  • the speckle noise reduction optical system 300 can also be used as a light source for display devices such as projectors and televisions.
  • Example 4 will be described with reference to the drawings.
  • the speckle noise reduction optical system 400 which is a modification of the speckle noise reduction optical system 300, will be described.
  • FIG. 9 shows a schematic diagram of the speckle noise reduction optical system 400.
  • FIG. 10 shows a block diagram of the speckle noise reduction optical system 400.
  • the speckle noise reduction optical system 400 has a holder 6 on the outside of the integrator 2 of the speckle noise reduction optical system 300 and vibration portions 4 and 5 on the side surface of the holder 6. different.
  • the vibrating units 4 and 5 have a function of vibrating the integrator 2 together with the holder 6 in order to reduce the speckle noise of the laser beam incident on the integrator 2.
  • the efficiency can be improved by reflecting the laser beam scattered from the integrator 2 by the holder 6 and recycling the laser beam.
  • the efficiency decreases as the mean free path becomes smaller.
  • the distances of the light sources 21, 22, and 23 in the x and y directions For example, if the distance is large, the uniformity of the exit surface may be insufficient. In that case, it can be improved by reducing the mean free path, but the efficiency is reduced. Therefore, the provision of the holder 6 has a great effect on the efficiency improvement.
  • Example 5 will be described with reference to the drawings.
  • the speckle noise reduction optical system 500 which is a modification of the speckle noise reduction optical system 400, will be described.
  • FIG. 11 shows a schematic diagram of the speckle noise reduction optical system 500.
  • the speckle noise reduction optical system 500 is different in that the integrator 31 is provided instead of the integrator 2 of the speckle noise reduction optical system 400.
  • the integrator 31 has different densities of the particles 3 in the z direction, and the integrator 31 is divided into a transparent portion 32 without particles and a particle portion 33 with particles.
  • the particle density can be increased to improve the uniformity of the exit surface, but even if the holder 6 is provided, the return light returning to the incident surface side can be recycled. I can't.
  • Ordinary polygonal rods have the advantage of being able to achieve laser beam uniformity with an efficiency of almost 100% by utilizing internal reflection. Therefore, the transparent portion 32 improves the uniformity by utilizing the merit of efficiently improving the uniformity of the polygonal rod, and then the particle portion 33 reduces the uniformity and speckle noise to achieve efficiency and uniformity. It can solve all the reduction of sex and speckle noise.
  • Example 6 will be described with reference to the drawings. Here, the speckle noise reduction optical system 600 and the result of evaluating speckle noise with an actual machine will be described.
  • the speckle noise reduction optical system 600 is different in that the vibration unit 11 is provided instead of the vibration units 4 and 5 of the speckle noise reduction optical system 400. Further, the light sources 21, 22 and 23 were replaced with the light source 1.
  • the vibrating unit 11 has a holder 6 attached to a bearing, and the bearing is composed of a DC motor and a belt. The rotation speed of the motor was controlled by the voltage value.
  • a white screen (general copy paper) was placed on the emission surface side of the laser beam, and speckle noise was measured with a speckle contrast measuring device.
  • speckle construct measuring device SM01VS09 manufactured by OXIDE was used.
  • the light source was a green laser beam of SLM-RGB-T20-F manufactured by Sumitomo Electric Industries, Ltd., and a wavelength of 515 nm was oscillated at a drive current of 40 mA.
  • the integrator 2 used had an incident surface size of 0.8 ⁇ 0.6 mm, a length of 5.0 mm, a volume density of particles 3 of 0.3%, and a refractive index difference of 0.1.
  • the integrator 2 was adjusted and attached to about 50 ⁇ m with respect to the center of rotation of the bearing.
  • FIG. 13 shows the measurement result of speckle noise.
  • the horizontal axis shows the number of revolutions, and the vertical axis shows the speckle contrast corresponding to speckle noise. It was confirmed that the speckle contrast exceeding 50% in the stopped state (rotation speed 0) was reduced to about 3% under all conditions when the rotation speed was given in the range of 6 rpm to 23 rpm.
  • FIG. 14 is an image of speckle noise, where FIG. 14 (a) is the condition when stopped and FIG. 14 (b) is the condition when rotating (6 rpm). It can be seen that the speckle noise is reduced. Moreover, when the LED (light emission diode) was measured by this device, the speckle contrast value was about 3%.
  • this speckle noise reduction optical system can reduce the speckle noise to the same level as an LED without coherency. Further, the rotation speed of 6 rpm is 10 Hz, and it can be said that speckle noise can be reduced by vibration slower than the human audible range of 20 Hz.
  • the speckle noise reduction optical system always emits a light source 1 that emits a laser beam, an integrator 2 that is a transparent rod filled with at least particles 3, and an integrator 2 or a light source 1 at a speed higher than zero.
  • a vibrating unit 4, 5 or a vibrating unit 11 that vibrates minutely is provided, and the laser light travels inside the integrator 2, and speckle noise can be reduced by at least the particles 3 colliding with the laser light a plurality of times. By not moving in a straight line, zero speed can be avoided.
  • the integrator shall be a rectangular parallelepiped (integrator 2) or a cylinder (integrator 10).
  • the vibrating parts 4 and 5 are arranged on the incident side of the laser beam. By fixing the emission side and vibrating only the entrance surface side, it is possible to prevent the influence on the optical system in the subsequent stage of the speckle noise reduction optical system.
  • the vibrating parts 4 and 5 are preferably set to have a vibrating width so that an angle change of at least 1 degree occurs when the laser beam collides with the particles 3.
  • the vibration width is achieved at 1 ⁇ m.
  • the vibrating parts 4, 5 and 11 vibrate at a speed slower than 20 Hz. This makes it possible to realize a quiet device.
  • the integrator has a length of 5 mm or less in the traveling direction of the laser beam. This makes it possible to provide a small device.
  • Particle 3 is a transparent particle, and the refractive index difference between the transparent particle and the transparent rod of the integrator is 0.025 or more. As a result, speckle noise can be reduced.
  • the particle 3 has a diameter in the range of 1 ⁇ m to 5 ⁇ m.
  • a speckle noise reduction optical system can be realized at low cost.
  • the integrator 2 includes an incident surface on which the laser beam is incident and an emitting surface on which the laser beam is emitted, and the incident surface and the emitting surface are 1 mm square or less. By doing so, it is possible to easily design the optical system in the subsequent stage of the speckle noise reduction optical system.
  • the LED chip size is 1 mm square, so the effect of easy replacement of the LED can be obtained. If it is larger than 1 mm square, the etendue becomes large and the efficiency loss becomes large when designing the subsequent optical system.
  • the volume density of the particles 3 filled in the integrator shall be in the range of 0.1% to 5%.
  • a reflective surface (corresponding to the holder 6) for recycling the leaked laser beam to the integrator 2 is provided.
  • the light sources 21, 22, and 23 emit at least a plurality of laser beams having different wavelengths. As a result, it can be used as a small light source device for a display device.
  • the emission points of multiple laser beams are different. This means that they are not the same exit point as the light sources 21, 22, and 23.
  • the particle density may be different in the traveling direction of the laser beam as in the integrator 31. This can improve efficiency.
  • the laser beam is directly incident on the integrator from the light source. For example, even if a lens or a mirror is arranged between the light source 1 and the integrator 2. I don't care.
  • It can be used for display devices such as TVs and projectors.

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Abstract

Provided is a speckle noise reduction optical system that is low-cost, compact in size, and quiet. One preferable aspect of the present invention pertains to a speckle noise reduction optical system characterized by being provided with: a light source for emitting a laser beam; an integrator which is transparent to the laser beam and has particles filled in a part thereof; and an oscillation unit which oscillates the laser beam relative to the integrator at a speed greater than zero, wherein the laser beam progresses inside the integrator, resulting in the laser beam emitted from the integrator to have a reduced level of speckle noise.

Description

スペックルノイズ低減光学系Speckle noise reduction optics
　本発明は、レーザ光のスペックルノイズを低減する技術に関するものである。 The present invention relates to a technique for reducing speckle noise of laser light.
　スペックルノイズを低減する手法として、多角形ロッドを用いた手法が特許文献１、ミー散乱を用いた手法が特許文献２で提案されている。 As a method for reducing speckle noise, a method using a polygonal rod is proposed in Patent Document 1, and a method using Mie scattering is proposed in Patent Document 2.
特開平１１－６４７８９号公報Japanese Unexamined Patent Publication No. 11-64789 国際公開ＷＯ２０１２／１００６４５号公報International Publication WO2012 / 100645
　テレビやプロジェクタなどの表示装置では、色再現範囲を拡大するためスペクトル幅の狭いレーザ光が用いられている。しかしながらレーザ光はコヒーレント光であることと、画面表面の光学的粗さに起因して、人の眼にはスペックルノイズが観察される。スペックルノイズは画像の品質に深刻な影響を与えるため、スペックルノイズを低減する方法が色々と提案されている。人が認識可能な５０ｍｓｅｃ以下の時間範囲で空間的にスペックルノイズのパターンを多重することでスペックルノイズを低減する手法が一般的である。 In display devices such as televisions and projectors, laser light with a narrow spectrum width is used to expand the color reproduction range. However, due to the fact that the laser beam is coherent light and the optical roughness of the screen surface, speckle noise is observed in the human eye. Since speckle noise has a serious effect on image quality, various methods for reducing speckle noise have been proposed. A method of reducing speckle noise by spatially multiplexing speckle noise patterns within a time range of 50 msec or less that can be recognized by humans is common.
　例えば特許文献１では、多角形ロッド内面でレーザ光の反射角度が回転により変化することを利用して空間的にスペックルノイズのパターンを多重する手法が記載されている。 For example, Patent Document 1 describes a method of spatially multiplexing speckle noise patterns by utilizing the fact that the reflection angle of laser light changes with rotation on the inner surface of a polygonal rod.
　また特許文献２では、ミー散乱を起こす光反射室と光源を摂動することで空間的にスペックルノイズのパターンを多重する手法が記載されている。 Further, Patent Document 2 describes a method of spatially multiplexing speckle noise patterns by perturbing a light reflection chamber and a light source that cause Mie scattering.
　特許文献１のように透明な多角形ロッドを用いると、入射したレーザ光が多角形ロッドと平行な場合、内面反射することなく多角形ロッドから出射するため、スペックルノイズのパターンの多重化ができず、スペックルノイズが残留する。また、例えば多角形内部に入射したレーザ光が１度の場合、多角形ロッドの幅１ｍｍ、屈折率を１．５として計算すると、約５８ｍｍの長さが必要になり、小型化にも課題がある。また時間５０ｍｓｅｃ以下で空間的にスペックルノイズのパターンを１０回多重するためには、２００Ｈｚ（１／５０ｍｓｅｃ×１０回）で回転させる必要がある。２００Ｈｚは人間の可聴域（２０Ｈｚから２０ｋＨｚ）の範囲であり、防音対策も必要となる。 When a transparent polygonal rod as in Patent Document 1 is used, when the incident laser beam is parallel to the polygonal rod, it is emitted from the polygonal rod without internal reflection, so that the speckle noise pattern can be multiplexed. It cannot be done, and speckle noise remains. Further, for example, when the laser beam incident on the inside of the polygon is 1 degree, if the width of the polygon rod is 1 mm and the refractive index is 1.5, a length of about 58 mm is required, which is a problem for miniaturization. is there. Further, in order to spatially multiplex the speckle noise pattern 10 times in a time of 50 msec or less, it is necessary to rotate at 200 Hz (1/50 msec × 10 times). 200Hz is in the human audible range (20Hz to 20kHz), and soundproofing measures are also required.
　特許文献２では、ミー散乱を用いる点や摂動させる具体的な記述が無い。光反射室を鏡面にするには、硝子であれば必要な面を研磨する必要があり安価に実現できない。また樹脂で射出成形する場合、側面は取り出し時にひっかき傷が残留するため、鏡面化するには複雑な仕掛けが必要になり、一度に多数個取りするような安価な成形ができない等コスト面の課題もある。また摂動に用いるカンチレバー、マイクロバネ等では１次元でのランダム変調は可能であるが、１次元のランダム変調は、サイン波に近似できレーザ光の動きが停止する時間が発生する。この停止時間を考慮して５０ｍｓｅｃ以下で空間的にスペックルノイズのパターンを１０回多重するためには、やはり２００Ｈｚ（１／５０ｍｓｅｃ×１０回）の変調が必要になり、特許文献１同様に防音対策も必要となる。 Patent Document 2 does not describe the point of using Mie scattering or the specific description of perturbing. In order to make the light reflection chamber a mirror surface, it is necessary to polish the necessary surface if it is glass, which cannot be realized at low cost. In addition, when injection molding is performed with resin, scratches remain on the side surface when it is taken out, so a complicated mechanism is required to make it mirror-finished, and it is not possible to perform inexpensive molding such as taking a large number of pieces at once, which is a cost issue. There is also. In addition, one-dimensional random modulation is possible with a cantilever, microspring, etc. used for perturbation, but one-dimensional random modulation can approximate a sine wave and a time occurs when the movement of the laser beam stops. In consideration of this stop time, in order to spatially multiplex the speckle noise pattern 10 times at 50 msec or less, modulation of 200 Hz (1/50 msec × 10 times) is still required, and soundproofing is performed as in Patent Document 1. Measures are also required.
　本発明の目的は、上記の課題を鑑み、低コストで小型かつ静かなスペックルノイズ低減光学系を提供することである。 An object of the present invention is to provide a low-cost, compact and quiet speckle noise reduction optical system in view of the above problems.
　本発明の好ましい一側面は、レーザ光を出射する光源と、粒子が少なくとも一部に充填された、レーザ光に対して透明なインテグレータと、レーザ光をインテグレータに対して、ゼロより大きい速度で相対的に振動させる振動部と、を備え、レーザ光はインテグレータの内部を進行し、インテグレータから射出するレーザ光のスペックルノイズを低減することを特徴とする、スペックルノイズ低減光学系である。 A preferred aspect of the present invention is a light source that emits a laser beam, an integrator that is at least partially filled with particles and is transparent to the laser beam, and a laser beam relative to the integrator at a speed greater than zero. The speckle noise reduction optical system is characterized in that the laser beam travels inside the integrator and reduces the speckle noise of the laser beam emitted from the integrator.
　低コストで小型かつ静かなスペックルノイズ低減光学系を提供できる。 We can provide a compact and quiet speckle noise reduction optical system at low cost.
実施例１のスペックルノイズ低減光学系の斜視図。The perspective view of the speckle noise reduction optical system of Example 1. FIG. 実施例１のインテグレータの機能を示した概略図。The schematic diagram which showed the function of the integrator of Example 1. FIG. 実施例１のレーザ光と粒子の偏芯量とレーザ光の偏角を計算したグラフ。The graph which calculated the amount of eccentricity of a laser beam and a particle of Example 1 and the declination angle of a laser beam. 実施例１の粒子密度と平均自由行程を計算したグラフ。The graph which calculated the particle density and the mean free path of Example 1. 実施例１の平均自由行程と効率を計算したグラフ。The graph which calculated the mean free path and efficiency of Example 1. 実施例１のインテグレータの振動の軌跡を示した概略図。The schematic diagram which showed the vibration locus of the integrator of Example 1. FIG. 実施例２のスペックルノイズ低減光学系の斜視図。The perspective view of the speckle noise reduction optical system of Example 2. FIG. 実施例３のスペックルノイズ低減光学系の斜視図。The perspective view of the speckle noise reduction optical system of Example 3. FIG. 実施例４のスペックルノイズ低減光学系の斜視図。The perspective view of the speckle noise reduction optical system of Example 4. FIG. 実施例４のスペックルノイズ低減光学系のシステムブロック図。The system block diagram of the speckle noise reduction optical system of Example 4. 実施例５のスペックルノイズ低減光学系の斜視図。The perspective view of the speckle noise reduction optical system of Example 5. 実施例６のスペックルノイズ低減光学系を示した斜視図。The perspective view which showed the speckle noise reduction optical system of Example 6. 実施例６のスペックルノイズを計測した実測結果のグラフ。The graph of the actual measurement result which measured the speckle noise of Example 6. スペックルノイズを観測した画像。Image of observing speckle noise.
　以下、図に示す実施例に基づいて本発明を実施するための形態を説明するが、これにより本発明が限定されるものではない。 Hereinafter, a mode for carrying out the present invention will be described based on the examples shown in the figure, but the present invention is not limited thereto.
　以下に説明する発明の構成において、同一部分又は同様な機能を有する部分には同一の符号を異なる図面間で共通して用い、重複する説明は省略することがある。 In the configuration of the invention described below, the same reference numerals may be used in common between different drawings for the same parts or parts having similar functions, and duplicate description may be omitted.
　同一あるいは同様な機能を有する要素が複数ある場合には、同一の符号に異なる添字を付して説明する場合がある。ただし、複数の要素を区別する必要がない場合には、添字を省略して説明する場合がある。 When there are multiple elements with the same or similar functions, the same code may be explained with different subscripts. However, if it is not necessary to distinguish between a plurality of elements, the subscript may be omitted for explanation.
　本明細書等における「第１」、「第２」、「第３」などの表記は、構成要素を識別するために付するものであり、必ずしも、数、順序、もしくはその内容を限定するものではない。また、構成要素の識別のための番号は文脈毎に用いられ、一つの文脈で用いた番号が、他の文脈で必ずしも同一の構成を示すとは限らない。また、ある番号で識別された構成要素が、他の番号で識別された構成要素の機能を兼ねることを妨げるものではない。 Notations such as "first", "second", and "third" in the present specification and the like are attached to identify the components, and do not necessarily limit the number, order, or contents thereof. is not. In addition, numbers for identifying components are used for each context, and numbers used in one context do not always indicate the same composition in other contexts. Further, it does not prevent the component identified by a certain number from having the function of the component identified by another number.
　図面等において示す各構成の位置、大きさ、形状、範囲などは、発明の理解を容易にするため、実際の位置、大きさ、形状、範囲などを表していない場合がある。このため、本発明は、必ずしも、図面等に開示された位置、大きさ、形状、範囲などに限定されない。 The position, size, shape, range, etc. of each configuration shown in the drawings, etc. may not represent the actual position, size, shape, range, etc. in order to facilitate understanding of the invention. Therefore, the present invention is not necessarily limited to the position, size, shape, range, etc. disclosed in the drawings and the like.
　以下の実施例で説明されるスペックルノイズ低減光学系の一例では、レーザ光を出射する光源と、少なくとも粒子が充填された透明ロッドであるインテグレータと、そのインテグレータまたは光源を常にゼロより大きい速度で微小に振動させる振動部とを備え、レーザ光はインテグレータ内部を進行し、少なくとも粒子とレーザ光が複数回衝突することでスペックルノイズを低減する。 In an example of a speckle noise reduction optical system described in the following examples, a light source that emits laser light, an integrator that is at least a transparent rod filled with particles, and the integrator or light source are always operated at a speed greater than zero. It is equipped with a vibrating part that vibrates minutely, and the laser light travels inside the integrator, and speckle noise is reduced by at least the particles colliding with the laser light multiple times.
　本発明における実施例１について図を用い説明する。
  図１はスペックルノイズ低減光学系１００を図示した概略図である。スペックルノイズ低減光学系１００は、光源１、インテグレータ２、振動部４，５から構成されている。 Example 1 in the present invention will be described with reference to the drawings.
FIG. 1 is a schematic view illustrating a speckle noise reduction optical system 100. The speckle noise reduction optical system 100 includes a light source 1, an integrator 2, and vibration units 4 and 5.
　光源１はレーザ光を出射する光源であり、所定のスペクトル幅の波長のレーザ光をｚ方向に出射する。光源１としては、既存のレーザダイオード等の光源を使用できる。インテグレータ２は、レーザ光に対して透明な多角柱たとえば四角柱体であり、内部には粒子３が所定の密度で分散されている。粒子３はレーザ光を散乱させる散乱粒子である。 The light source 1 is a light source that emits laser light, and emits laser light having a wavelength having a predetermined spectral width in the z direction. As the light source 1, an existing light source such as a laser diode can be used. The integrator 2 is a polygonal column, for example, a quadrangular prism that is transparent to a laser beam, and particles 3 are dispersed therein at a predetermined density. The particle 3 is a scattered particle that scatters the laser beam.
　振動部４、５はインテグレータ２を振動させる機能を有している。振動部４はｘ軸方向を振動させ、振動部５はｙ軸方向を振動させる機能がある。また振動部４、５の振動周期の位相を異ならせることで、常にインテグレータ２の動く速度がゼロとならないように設定される。振動部４、振動部５としては、既存の圧電式リニア振動アクチュエータ等を使用できる。 The vibrating units 4 and 5 have a function of vibrating the integrator 2. The vibrating unit 4 has a function of vibrating in the x-axis direction, and the vibrating unit 5 has a function of vibrating in the y-axis direction. Further, by making the phases of the vibration cycles of the vibrating units 4 and 5 different, the moving speed of the integrator 2 is set so as not to be zero at all times. As the vibrating unit 4 and the vibrating unit 5, existing piezoelectric linear vibrating actuators and the like can be used.
　光源１から出射したレーザ光はインテグレータ２に図中左側から入射し、内部を進行して図中右側から出射する。以降入射する面を入射面、出射する面を出射面、それ以外の面を側面と記す。インテグレータ２の内部を進行するレーザ光は所定の頻度で粒子３と衝突して散乱される。また、振動部４、５でインテグレータ２は動作しているため、出射するレーザ光の一本の光線に着目すると、着目した一本の光線は５０ｍｓｅｃ以下の時間で常に異なる角度で出射している。このため、スペックルノイズによるパターンを多重化することができる。 The laser beam emitted from the light source 1 enters the integrator 2 from the left side in the figure, travels inside, and is emitted from the right side in the figure. Hereinafter, the incident surface is referred to as an incident surface, the exit surface is referred to as an exit surface, and the other surfaces are referred to as side surfaces. The laser beam traveling inside the integrator 2 collides with the particles 3 at a predetermined frequency and is scattered. Further, since the integrator 2 is operating in the vibrating units 4 and 5, when focusing on one ray of the emitted laser beam, the one ray of interest always emits at a different angle in a time of 50 msec or less. .. Therefore, the pattern due to speckle noise can be multiplexed.
　入射面と出射面は、表面荒さを大きくしても問題ない。入射面と出射面が荒れていることによって表面散乱による効果により、スペックルノイズを低減する機能として利用しても良い。 There is no problem even if the surface roughness of the entrance surface and the exit surface is increased. It may be used as a function of reducing speckle noise due to the effect of surface scattering due to the roughness of the entrance surface and the exit surface.
　本実施例のインテグレータは、四角柱体を媒質１で構成し、該媒質１とは異なる屈折率を有し、伝搬する光を散乱せしめる粒子（媒質２）が充填された構造であれば特に限定はない。以下に説明する材料及び製造方法を用いることによって容易に得ることができる。 The integrator of this embodiment is particularly limited as long as it has a structure in which a quadrangular prism is composed of a medium 1, has a refractive index different from that of the medium 1, and is filled with particles (medium 2) that scatter propagating light. There is no. It can be easily obtained by using the materials and manufacturing methods described below.
　＜媒質１＞
　まず、媒質１の材質として、光を伝搬する観点から透明性の高い材料が選択される。本実施例ではアクリル系の光硬化樹脂を使用するが、透明度の高い材料であれば特に限定はなく、例えば、エポキシ系の熱硬化性の樹脂やアクリルやポリカーボネイト等の熱可塑性樹脂や、ガラス等を使用してもよい。 <Medium 1>
First, as the material of the medium 1, a material having high transparency is selected from the viewpoint of propagating light. In this embodiment, an acrylic photocurable resin is used, but the material is not particularly limited as long as it is a highly transparent material. For example, an epoxy-based thermosetting resin, a thermoplastic resin such as acrylic or polycarbonate, glass, or the like. May be used.
　光硬化性樹脂を用いると固形の媒質２を使用する際に該媒質２との混合が容易である観点、また硬化後に冷却や乾燥等の工程を必要としないため作業効率が向上する観点、所定の形状のインテグレータを得られやすい観点、からより好ましい。また、アクリル系の材料を使用すると透過率が高く、光の利用効率を高めることが可能となるため、より好ましい。 When a photocurable resin is used, it is easy to mix with the solid medium 2 when it is used, and from the viewpoint of improving work efficiency because steps such as cooling and drying are not required after curing. It is more preferable from the viewpoint that it is easy to obtain an integrator having the shape of. Further, it is more preferable to use an acrylic material because the transmittance is high and the efficiency of light utilization can be improved.
　＜媒質２＞
　媒質２は、媒質１中に、媒質１と異なる屈折率の粒子を混合させることによって効率良く得ることができる。媒質２の材質として、本実施例では、架橋ポリスチレン微粒子を使用するが、透明度の高い材料であれば、その他の材質のプラスチック粒子やガラス粒子等、他の材料を使用してもよい。 <Medium 2>
The medium 2 can be efficiently obtained by mixing particles having a refractive index different from that of the medium 1 in the medium 1. In this embodiment, crosslinked polystyrene fine particles are used as the material of the medium 2, but other materials such as plastic particles and glass particles of other materials may be used as long as they are highly transparent materials.
　ただし、光を散乱させるためには屈折率差があることが重要であるため、媒質１と媒質２との間で屈折率差は０．０２５以上あることが望ましい。０．００２５以上０．１５以下であると、媒質１と媒質２の比重を近接させやすくなり媒質２を媒質１に混合させるのが容易である観点、及び、効率の低下を抑えたうえで、散乱の効果も得られやすいという観点、からより好ましい。ここで、媒質１と媒質２の屈折率を比較したときに、どちらの屈折率が大きくてもよい。なお、本実施例における屈折率差とは、媒質１又は媒質２のうち、高屈折率である媒質１又は媒質２の屈折率と、低屈折率である媒質２又は媒質１の屈折率の差分から算出される値とする。 However, since it is important that there is a difference in refractive index in order to scatter light, it is desirable that the difference in refractive index between medium 1 and medium 2 is 0.025 or more. When it is 0.0025 or more and 0.15 or less, the specific gravities of the medium 1 and the medium 2 can be easily brought close to each other, and the medium 2 can be easily mixed with the medium 1, and the decrease in efficiency can be suppressed. It is more preferable from the viewpoint that the effect of scattering can be easily obtained. Here, when the refractive indexes of the medium 1 and the medium 2 are compared, either of the refractive indexes may be larger. The difference in refractive index in this embodiment is the difference between the refractive index of medium 1 or medium 2 having a high refractive index and the refractive index of medium 2 or medium 1 having a low refractive index among the medium 1 or medium 2. The value is calculated from.
　＜粒径＞
　媒質２の粒径は、１μｍ以上、５μｍ以下であることが望ましい。これは、前述のように、粒径が小さいと光が散乱しすぎて光の取り出し効率が低下してしまい、粒径が大きいと光が散乱しにくいためである。また、粒径は略均一である方が望ましいが、９０％以上の粒子が上記粒径範囲内に含まれていれば効果は得られるため問題ない。 <Grain size>
The particle size of the medium 2 is preferably 1 μm or more and 5 μm or less. This is because, as described above, when the particle size is small, the light is scattered too much and the light extraction efficiency is lowered, and when the particle size is large, the light is hard to be scattered. Further, it is desirable that the particle size is substantially uniform, but there is no problem because the effect can be obtained if 90% or more of the particles are contained within the above particle size range.
　＜製造方法＞
　媒質１と媒質２を一体化する工法としては、例えば液状の媒質１を用意し、次いで媒質１と媒質２を混合させ、それを所定の形状に光硬化させて製作する方法があるが、熱プレス、射出成形、削りだし等、他の工法でも製作可能である。中でも液状の媒質１を用いると、媒質２を容易に混合させることができるため、より好ましく、媒質１に媒質２を混合させた状態も液状であると、所定の形状に加工しやすいためさらに好ましい。 <Manufacturing method>
As a method of integrating the medium 1 and the medium 2, for example, there is a method of preparing a liquid medium 1, then mixing the medium 1 and the medium 2, and photocuring the medium 1 to a predetermined shape. It can also be manufactured by other methods such as pressing, injection molding, and shaving. Of these, a liquid medium 1 is more preferable because the medium 2 can be easily mixed, and a liquid medium 1 mixed with the medium 2 is more preferable because it can be easily processed into a predetermined shape. ..
　製品形状作成時には、製品の高さの板を製作後に外周を切断して製品サイズにしてもよいし、製品サイズの空間を持つ型を製作して、型に樹脂を流し込んで硬化させて製作してもよい。 When creating the product shape, a plate with the height of the product may be manufactured and then the outer circumference may be cut to make the product size, or a mold with a space of the product size may be manufactured, and resin may be poured into the mold and cured. You may.
　＜表面粗さ＞
　本実施例のインテグレータの表面粗さ（Ｒａ；算術平均粗さ）は、側面の長さ方向では小さくすることが望ましい。これは光が側面にあたったときに側面の長さ方向で面が荒れていると、臨界角を超えて光が側面から抜けてしまうためである。長さ方向に垂直な方向では、光の伝搬に悪影響のない範囲で面が荒れていてもよい。また光入射面や光出射面については、光の拡散が高まる効果が見込めるため、光の出射に悪影響のない範囲で面が荒れていてもよい。 <Surface roughness>
It is desirable that the surface roughness (Ra; arithmetic mean roughness) of the integrator of this embodiment be reduced in the length direction of the side surface. This is because if the surface is rough in the length direction of the side surface when the light hits the side surface, the light exceeds the critical angle and escapes from the side surface. In the direction perpendicular to the length direction, the surface may be rough as long as the light propagation is not adversely affected. Further, since the light incident surface and the light emitting surface can be expected to have an effect of increasing the diffusion of light, the surfaces may be rough as long as the light emitting surface is not adversely affected.
　以上の観点から側面の光軸方向の表面粗さは０μｍ超～２．０μｍであると良く、０μｍ超～１．０μｍであるとより良く、０μｍ超～０．５μｍであるとさらに良い。光入射面及び光出射面の表面粗さは、上記側面の表面粗さ以上であって、０．０１μｍ～１０μｍであると良く、０．５μｍ～５μｍであるとより良く、０．５μｍ～３μｍであるとさらに良い。尚、側面の光軸に対して垂直方向の表面粗さは０μｍ超であって、上限は上述した光入射面及び光出射面の表面粗さで列挙した値以下であると良い。 From the above viewpoint, the surface roughness of the side surface in the optical axis direction is preferably more than 0 μm to 2.0 μm, better if it is more than 0 μm to 1.0 μm, and even better if it is more than 0 μm to 0.5 μm. The surface roughness of the light incident surface and the light emitting surface is equal to or higher than the surface roughness of the above side surface, and is preferably 0.01 μm to 10 μm, better is 0.5 μm to 5 μm, and is 0.5 μm to 3 μm. It is even better if it is. It is preferable that the surface roughness in the direction perpendicular to the optical axis of the side surface is more than 0 μm, and the upper limit is equal to or less than the values listed in the above-mentioned surface roughness of the light incident surface and the light emitting surface.
　側面の光軸（図１中左から右方向）に対して垂直方向の表面粗さは上述の範囲内で小さい方が好ましいが、加工効率の観点から任意に選択して構わない。具体的には、例えば切削加工によって側面を形成する場合、切削方向の表面粗さと、切削方向と略垂直方向の表面粗さは、前者の切削方向の表面粗さの方が小さくなる傾向にあり、加工効率の向上のために切削速度等を変化させると、特に、切削方向と略垂直方向の表面粗さが荒くなる。この場合、切削方向を光軸方向とすることによって、作業効率を維持しつつ、光の伝搬効率を保持させることが可能となる。また、成形等を利用する場合であって、かつ成形鋳型側に切削痕等の表面粗さの方向性を有する場合、該表面粗さは、インテグレータに転写される。この場合も同様に、光軸方向を表面粗さの小さい方向とすることによって、良好な光の伝搬効率を保持させることが可能となる。 The surface roughness in the direction perpendicular to the optical axis of the side surface (from left to right in FIG. 1) is preferably small within the above range, but it may be arbitrarily selected from the viewpoint of processing efficiency. Specifically, for example, when a side surface is formed by cutting, the surface roughness in the cutting direction and the surface roughness in the direction substantially perpendicular to the cutting direction tend to be smaller than the surface roughness in the former cutting direction. When the cutting speed or the like is changed in order to improve the machining efficiency, the surface roughness in the direction substantially perpendicular to the cutting direction becomes rough. In this case, by setting the cutting direction to the optical axis direction, it is possible to maintain the light propagation efficiency while maintaining the work efficiency. Further, when molding or the like is used and the molding mold side has a directionality of surface roughness such as cutting marks, the surface roughness is transferred to the integrator. Similarly, in this case as well, by setting the optical axis direction to the direction in which the surface roughness is small, it is possible to maintain good light propagation efficiency.
　また、媒質２に固形の粒子を用いる場合、媒質２からなる散乱粒子が側面から突出することによる凸部や、散乱粒子が側面から脱落した跡による凹部からなる凹凸が表面荒さに寄与する程度に存在すると、上述したように側面からの光の漏れが発生する一因となる。以上のことから、さらに側面の表面粗さ（Ｒａ）は、媒質２として導入する散乱粒子の平均粒径の１／２以下であると良い。これは、インテグレータの側面から散乱粒子を突出させない状態又は、側面から突出する散乱粒子を切断し、平滑化しておくことによって実現できる。 Further, when solid particles are used for the medium 2, the unevenness formed by the convex portion due to the scattered particles made of the medium 2 protruding from the side surface and the concave portion formed by the trace of the scattered particles falling off from the side surface contributes to the surface roughness. If present, it contributes to the leakage of light from the side surface as described above. From the above, the surface roughness (Ra) of the side surface is preferably 1/2 or less of the average particle size of the scattered particles introduced as the medium 2. This can be achieved by not projecting the scattered particles from the side surface of the integrator, or by cutting and smoothing the scattered particles projecting from the side surface.
　図２は、インテグレータ２の機能を示した図である。入射したレーザ光は粒子３により散乱する。そのレーザ光と粒子の衝突は平均自由行程δＬの頻度で発生する。側面に進行するレーザ光は屈折率の差で全反射して、インテグレータ２内部に閉じ込められる。臨界角を超えたレーザ光が側面に進行すると、インテグレータ２の外部に漏れロス（loss）となる。 FIG. 2 is a diagram showing the functions of the integrator 2. The incident laser beam is scattered by the particles 3. The collision between the laser beam and the particles occurs at a frequency of mean free path δL. The laser beam traveling to the side surface is totally reflected by the difference in the refractive index and is confined inside the integrator 2. When the laser beam exceeding the critical angle travels to the side surface, a leakage loss occurs to the outside of the integrator 2.
　スペックルノイズ低減光学系１００では、スペックルノイズのパターンを平均化するため、３個の指標が重要である。１個目は、出射するレーザ光が粒子散乱でどれだけ曲げられるかを示す指標の偏角（Δθ）である。２個目は、粒子散乱を引き起こす頻度を示す指標の平均自由行程（δＬ）である。３個目は入射するレーザ光がどれだけ出射できるかを示す効率（Ｉｏｕｔ／Ｉｉｎ）である。 In the speckle noise reduction optical system 100, three indexes are important for averaging the speckle noise pattern. The first is the declination (Δθ) of an index indicating how much the emitted laser beam is bent by particle scattering. The second is the mean free path (δL), which is an index indicating the frequency of causing particle scattering. The third is the efficiency (I out / I in ) that indicates how much the incident laser beam can be emitted.
　図３は粒子とレーザ光の偏芯量（横軸）と、粒子とレーザ光が衝突した後に曲げられる角度（縦軸）を幾何計算したグラフである。左右のグラフは縦軸のスケールを変えた同じグラフである。媒質１と媒質２の屈折率差（ΔＮ）は０．０１、０．０２５、０．０５、０．１の４例を示す。また粒子は直径２μｍ、レーザ光の波長は５５０ｎｍとして計算した。 FIG. 3 is a graph obtained by geometrically calculating the amount of eccentricity between the particles and the laser beam (horizontal axis) and the angle at which the particles and the laser beam are bent after they collide (vertical axis). The left and right graphs are the same graphs with different scales on the vertical axis. The four examples of the refractive index difference (ΔN) between the medium 1 and the medium 2 are 0.01, 0.025, 0.05, and 0.1 are shown. The particles were calculated assuming that the diameter was 2 μm and the wavelength of the laser beam was 550 nm.
　偏芯量が大きくなると出射する角度も大きくなり、屈折率差が大きいと出射する角度が大きくなる。平均的な人間の瞳径が７ｍｍであり、その端から端に光が動いたならば十分異なる状態と認識できる角度とする。人間と画像の距離を一般的な条件として５００ｍｍに設定すると、角度は約０．８度であり、少なくとも１度以上の角度があれば人が別のパターンと認識すると考えて良い。 The larger the amount of eccentricity, the larger the exit angle, and the larger the difference in refractive index, the larger the exit angle. The average human pupil diameter is 7 mm, and if the light moves from one end to the other, the angle is set so that it can be recognized as a sufficiently different state. If the distance between the human and the image is set to 500 mm as a general condition, the angle is about 0.8 degrees, and if there is an angle of at least 1 degree or more, it can be considered that the person recognizes it as another pattern.
　図３のグラフからは、屈折率差が０．０１のとき偏芯量が０．５μｍ（直径の２５％）でも１度に満たず十分な角度を与えることが出来ない。屈折率差が０．０２５もあると、偏芯量が０．５μｍで１．６度と十分な角度を与えられる。ここで、偏芯量０．５μｍは振動幅の半値を示しており、振動の振幅１．０μｍに相当する。この振幅は粒子径Φ２μｍの５０％に相当する。振動量を大きくすると、さらに大きな角度を与えられるが、振動量を小さくして、後段の光学系への影響を小さくすることを目的に０．５μｍ以下の振動を想定している。なお、偏芯量０．３μｍで１度の偏角を与えるには、屈折率差が約０．０２５以上必要である。 From the graph of FIG. 3, when the difference in refractive index is 0.01, even if the amount of eccentricity is 0.5 μm (25% of the diameter), it is less than 1 degree and a sufficient angle cannot be given. If the difference in refractive index is as much as 0.025, a sufficient angle of 1.6 degrees can be given when the amount of eccentricity is 0.5 μm. Here, the eccentricity amount of 0.5 μm indicates a half value of the vibration width, and corresponds to the vibration amplitude of 1.0 μm. This amplitude corresponds to 50% of the particle diameter of Φ2 μm. If the amount of vibration is increased, a larger angle can be given, but for the purpose of reducing the amount of vibration and reducing the influence on the optical system in the subsequent stage, vibration of 0.5 μm or less is assumed. It should be noted that a difference in refractive index of about 0.025 or more is required to give an argument of 1 degree with an eccentricity of 0.3 μm.
　図４は、インテグレータ２内の粒子３の密度（横軸）と平均自由行程（縦軸）を計算した例である。屈折率差は図３同様に４例を示している。粒子の密度が大きくなると平均自由行程は小さくなる。また屈折率差が大きいほど平均自由行程が小さいことがわかる。 FIG. 4 is an example of calculating the density (horizontal axis) and the mean free path (vertical axis) of the particles 3 in the integrator 2. As for the difference in refractive index, four examples are shown as in FIG. The mean free path decreases as the particle density increases. It can also be seen that the larger the difference in refractive index, the smaller the mean free path.
　装置の小型化の観点から、インテグレータの長さは５ｍｍ以下にすることを想定すると、平均自由行程は少なくとも１回以上の衝突を起こすため、５ｍｍ以下が必要である。粒子で光が散乱されると、効率が落ちる要因になる。後述するが、散乱回数は１０回以下が望ましく、平均自由行程は０．５ｍｍ～５ｍｍの間が良いといえる。 From the viewpoint of miniaturization of the device, assuming that the length of the integrator is 5 mm or less, the mean free path requires at least one collision, so 5 mm or less is required. When light is scattered by particles, it causes a decrease in efficiency. As will be described later, the number of scatterings is preferably 10 or less, and the mean free path is preferably between 0.5 mm and 5 mm.
　図５は、平均自由行程（横軸）と効率（縦軸）をシミュレーションした結果である。ここでは、粒子直径２μｍ、屈折率差０．０５、レーザ光の波長５５０ｎｍ、レーザ光の出射ファーフィールドパターン（ＦＦＰ）を１５度、光源とインテグレータの間隔を０．５ｍｍ、インテグレータ２の入射面と出射面のサイズを１×１ｍｍ、長さ５ｍｍとした。平均自由行程は粒子密度を変えたことで実現している。なお、ここでは、フレネル損失は考慮していない。 FIG. 5 shows the results of simulating the mean free path (horizontal axis) and efficiency (vertical axis). Here, the particle diameter is 2 μm, the refractive index difference is 0.05, the wavelength of the laser light is 550 nm, the emission farfield pattern (FFP) of the laser light is 15 degrees, the distance between the light source and the integrator is 0.5 mm, and the incident surface of the integrator 2 is used. The size of the exit surface was 1 × 1 mm and the length was 5 mm. The mean free path is realized by changing the particle density. The Fresnel loss is not considered here.
　図５に示すとおり、平均自由行程が小さくなるほど効率が低下する。９０％以上の効率を確保したい場合、平均自由行程は０．５ｍｍ以上とすることが望ましい。 As shown in FIG. 5, the smaller the mean free path, the lower the efficiency. When it is desired to secure an efficiency of 90% or more, it is desirable that the mean free path is 0.5 mm or more.
　図６は、振動部４、５でインテグレータ２を振動させたときの軌道を図示したものである。振動部４、５の位相を９０度ずらして振動させると図６（ａ）のように円軌道にできる。また位相は４５度ないし９０度でずらすことで図６（ｂ）のように楕円軌道になっても良い。図６（ｃ）のように位相を同期させて軌道を直線にすると、端で動きが停止するためスペックルノイズパターンが発生する。ここでｘ軸とｙ軸の振幅をそれぞれ１μｍとすると粒子３の直径２μｍの５０％で振動させることができる。 FIG. 6 illustrates the trajectory when the integrator 2 is vibrated by the vibrating units 4 and 5. When the vibrating parts 4 and 5 are vibrated with the phases shifted by 90 degrees, a circular orbit can be formed as shown in FIG. 6A. Further, the phase may be shifted by 45 degrees to 90 degrees to form an elliptical orbit as shown in FIG. 6 (b). When the orbits are made straight by synchronizing the phases as shown in FIG. 6C, the movement stops at the end, so that a speckle noise pattern is generated. Here, assuming that the amplitudes of the x-axis and the y-axis are 1 μm each, the particle 3 can be vibrated at 50% of the diameter of 2 μm.
　可聴周波数下限の２０Ｈｚよりゆっくりとした振動でスペックルノイズパターンを低減するには、認識不能な５０ｍｓｅｃ以下で少なくとも１０回平均化すると良い。すなわち５０ｍｓｅｃ以下の時間内に、レーザ光に１０回以上１度以上の偏角を与えれば良いという意味である。言い換えると５ｍｓｅｃ以下の間隔で、少なくとも１回１度以上の偏角を与えれば良いという意味である。 In order to reduce the speckle noise pattern with vibration slower than the lower limit of the audible frequency of 20 Hz, it is better to average at least 10 times at an unrecognizable 50 msec or less. That is, it means that the laser beam may be declinated 10 times or more and 1 degree or more within a time of 50 msec or less. In other words, it means that an argument of 1 degree or more should be given at least once at intervals of 5 msec or less.
　２０Ｈｚ（１周期５０ｍｓｅｃ）で１μｍの振幅で変化させると、５ｍｓｅｃで０．１ｕｍの振幅変化が発生する。振幅の半値が０．０５μｍである。 When the amplitude is changed by 1 μm at 20 Hz (50 msec per cycle), an amplitude change of 0.1 um occurs at 5 msec. The half value of the amplitude is 0.05 μm.
　図３から分かるように偏芯量０．０５μｍでは、屈折率差を大きくしても１回の散乱で１度以上の偏角を与えることができない。 As can be seen from FIG. 3, when the eccentricity amount is 0.05 μm, even if the difference in refractive index is increased, it is not possible to give an declination of 1 degree or more by one scattering.
　平均自由行程が０．５μｍで、インテグレータ２の長さが５ｍｍとすると１０回衝突が起こるため、１０回の衝突で１度以上の偏角が得られれば良い。言い換えると１回当たり０．１度の偏角が得られればよい。 If the mean free path is 0.5 μm and the length of the integrator 2 is 5 mm, 10 collisions will occur. Therefore, it is sufficient that an argument of 1 degree or more can be obtained by 10 collisions. In other words, it suffices to obtain an argument of 0.1 degree each time.
　図３から分かるように屈折率差０．０２５の時、０．１度の偏角が十分得られるといえる。 As can be seen from FIG. 3, when the refractive index difference is 0.025, it can be said that an argument of 0.1 degree can be sufficiently obtained.
　以上のように２０Ｈｚよりゆっくりとした１μｍの振動であっても、粒子直径２μｍで屈折率差０．０２５以上持たせ、インテグレータの長さを５ｍｍとしたとき平均自由行程を０．５ｍｍとすることで、スペックルノイズのパターンを１０回平均化することができ、効率９０％以上達成できる。スペックルノイズ低減光学系１００は人の可聴域外の振動で効率良くスペックルを低減できるといえる。 Even if the vibration is 1 μm slower than 20 Hz as described above, the average free path should be 0.5 mm when the particle diameter is 2 μm and the refractive index difference is 0.025 or more and the length of the integrator is 5 mm. Therefore, the speckle noise pattern can be averaged 10 times, and an efficiency of 90% or more can be achieved. It can be said that the speckle noise reduction optical system 100 can efficiently reduce speckle by vibration outside the human audible range.
　なお、平均自由行程０．５ｍｍとなる粒子密度は、屈折率差が０．０２５のとき、１Ｅ７ｐｃｓ／ｍｍ３、０．０５のとき２Ｅ６ｐｃｓ／ｍｍ３、０．１のとき、８Ｅ５ｐｃｓ／ｍｍ３である。インテグレータの透明樹脂と粒子の体積密度に置き換えると１Ｅ７ｐｃｓ／ｍｍ３のとき４．１９％、２Ｅ６ｐｃｓ／ｍｍ３のとき０．８４％、８Ｅ５ｐｃｓ／ｍｍ３のとき０．３４％である。 The particle density of the mean free path 0.5mm, when the difference in refractive index is 0.025, 1E7pcs / mm 3, 2E6pcs / mm 3 when 0.05, when 0.1, at 8E5pcs / mm 3 is there. Replacing the volume density of the transparent resin and particles of the integrator 4.19% when 1E7pcs / mm 3, 0.84% when 2E6pcs / mm 3, 0.34% when the 8E5pcs / mm 3.
　なお粒子径は小さくしても１μｍ以上とすることが望ましい。小さくなると製造難度が高くなるため、粒子が高価になるためである。また粒子径を大きくすると、偏芯量に伴う出射角度が小さくなるため、５μｍ以下とするのが望ましい。 It is desirable that the particle size is 1 μm or more even if it is small. This is because the smaller the size, the higher the manufacturing difficulty, and the more expensive the particles. Further, when the particle diameter is increased, the emission angle accompanying the amount of eccentricity becomes smaller, so it is desirable to set the particle diameter to 5 μm or less.
　また、振動部４、５は位相を変えて楕円軌道とすることで、常にインテグレータ２を動作させ続けられる。このため、ゆっくり動作させるときの一時停止した場合に問題となるスペックルノイズの残留を無くせる。 Also, by changing the phase of the vibrating parts 4 and 5 to form an elliptical orbit, the integrator 2 can always be operated. For this reason, it is possible to eliminate the residual speckle noise, which is a problem when the device is paused during slow operation.
　なお、多角柱を回転させると、出射面の多角柱の頂点部からレーザ光が出射しない時間が発生する。スペックルノイズ低減光学系１００では、インテグレータ２の中心を楕円運動させるため、レーザ光が出射しないエリアを無視できるほど小さくでき、効率が良い効果も得られる。 Note that when the polygonal prism is rotated, there is a time when the laser beam is not emitted from the apex of the polygonal prism on the exit surface. In the speckle noise reduction optical system 100, since the center of the integrator 2 is elliptical, the area where the laser beam is not emitted can be made small enough to be ignored, and an efficient effect can be obtained.
　なお、振動部は、レーザ光とインテグレータ２を相対的に振動させればよい。よって、振動部は、光源１、インテグレータ２、および光源とインテグレータの間の光路に挿入された光学素子の少なくとも一つにより、レーザ光とインテグレータの少なくとも一つを振動させればよい。光学素子として、例えば既存の音響光学素子が使用できる。 The vibrating part may vibrate the laser beam and the integrator 2 relatively. Therefore, the vibrating unit may vibrate at least one of the laser beam and the integrator by at least one of the light source 1, the integrator 2, and the optical element inserted in the optical path between the light source and the integrator. As the optical element, for example, an existing acoustic optical element can be used.
　光源１を振動させる場合は耐久性に、光路に光学素子を挿入してレーザ光を振動させる場合はコストに配慮が必要である。インテグレータ２を振動させる場合、全体を振動させる必要はなく、例えば図１に示すように光源１に近い部分（インテグレータのレーザ光の出射面より入射面に近い位置）を振動させることで、効率よくレーザ光とインテグレータの変位が可能となる。 It is necessary to consider durability when vibrating the light source 1 and cost when vibrating the laser beam by inserting an optical element into the optical path. When vibrating the integrator 2, it is not necessary to vibrate the whole, for example, by vibrating the part close to the light source 1 (the position closer to the incident surface than the emission surface of the laser beam of the integrator) as shown in FIG. 1, it is efficient. The laser beam and the integrator can be displaced.
　実施例２について図を用い説明する。ここでは、スペックルノイズ低減光学系１００の変形例であるスペックルノイズ低減光学系２００について説明する。 Example 2 will be described with reference to the drawings. Here, the speckle noise reduction optical system 200, which is a modification of the speckle noise reduction optical system 100, will be described.
　図７はスペックルノイズ低減光学系２００の概略図を示したものである。スペックルノイズ低減光学系２００はスペックルノイズ低減光学系１００のインテグレータ２の代わりにインテグレータ１０を、振動部４、５の代わりに振動部１１を配備した点が異なる。 FIG. 7 shows a schematic diagram of the speckle noise reduction optical system 200. The speckle noise reduction optical system 200 is different in that the integrator 10 is provided in place of the integrator 2 of the speckle noise reduction optical system 100, and the vibration unit 11 is provided in place of the vibration units 4 and 5.
　特許文献１記載のような通常の多角柱ロッドでは、内面反射を利用しているため、出射面の均一性を実現するには多角柱である必要がある。本実施例のインテグレータは粒子散乱で出射面の均一性を実現できるため、多角柱でなくインテグレータ１０のように円柱でも良い。円柱のインテグレータ１０では、ｘ方向またはｙ方向に０．５μｍ以上偏芯させて回転させる。そうすることで、図６（ａ）のようにインテグレータ１０の中心も円運動させることができる。偏芯が無いとインテグレータ１０の中心が停止することになるため中心軸付近にスペックルノイズが残留してしまう。 Since a normal polygonal prism rod as described in Patent Document 1 uses internal reflection, it is necessary to have a polygonal prism in order to realize uniformity of the exit surface. Since the integrator of this embodiment can realize the uniformity of the exit surface by particle scattering, a cylinder such as the integrator 10 may be used instead of a polygonal prism. The cylindrical integrator 10 is rotated by eccentricity of 0.5 μm or more in the x direction or the y direction. By doing so, the center of the integrator 10 can also be circularly moved as shown in FIG. 6A. If there is no eccentricity, the center of the integrator 10 will stop, and speckle noise will remain near the central axis.
　多角柱を回転させるとき、出射面の多角柱の頂点部からレーザ光が出射しない時間が発生する問題に対し。円柱のインテグレータ１０はレーザ光が出射しない時間がほぼ発生しないため、効率が良いといえる。振動部１１は、小型モータと歯車、またはベルトなどで簡易に実現できるといえる。 For the problem that the laser beam does not emit from the apex of the polygonal prism on the exit surface when rotating the polygonal prism. It can be said that the cylindrical integrator 10 is efficient because there is almost no time when the laser beam is not emitted. It can be said that the vibrating unit 11 can be easily realized by a small motor and gears, a belt or the like.
　実施例１で説明したように、スペックルノイズ低減光学系２００の構成でも低コストに小型、高効率、静かさを達成できる。 As described in Example 1, even with the configuration of the speckle noise reduction optical system 200, small size, high efficiency, and quietness can be achieved at low cost.
　実施例３について図を用い説明する。ここでは、スペックルノイズ低減光学系１００の変形例であるスペックルノイズ低減光学系３００、について説明する。 Example 3 will be described with reference to the drawings. Here, the speckle noise reduction optical system 300, which is a modification of the speckle noise reduction optical system 100, will be described.
　図８はスペックルノイズ低減光学系３００の概略図を示したものである。スペックルノイズ低減光学系３００はスペックルノイズ低減光学系１００の光源１の代わりに光源２１ないし２３を配備した点が異なる。 FIG. 8 shows a schematic diagram of the speckle noise reduction optical system 300. The speckle noise reduction optical system 300 is different in that light sources 21 to 23 are provided instead of the light source 1 of the speckle noise reduction optical system 100.
　光源２１、２２、２３は、赤、緑、青に相当する波長のレーザ光を出射する。スペックルノイズ低減光学系３００は、レーザ光のスペックルノイズを低減するだけでなく、光源２１、２２、２３から出射するレーザ光を散乱により均一にする効果も得られる。 The light sources 21, 22, and 23 emit laser light having wavelengths corresponding to red, green, and blue. The speckle noise reduction optical system 300 not only reduces the speckle noise of the laser beam, but also has the effect of making the laser beam emitted from the light sources 21, 22, and 23 uniform by scattering.
　スペックルノイズ低減光学系３００は、プロジェクタやテレビなどの表示装置用の光源としても利用できる。 The speckle noise reduction optical system 300 can also be used as a light source for display devices such as projectors and televisions.
　実施例４について図を用い説明する。ここでは、スペックルノイズ低減光学系３００の変形例であるスペックルノイズ低減光学系４００、について説明する。 Example 4 will be described with reference to the drawings. Here, the speckle noise reduction optical system 400, which is a modification of the speckle noise reduction optical system 300, will be described.
　図９はスペックルノイズ低減光学系４００の概略図を示したものである。図１０はスペックルノイズ低減光学系４００のブロック図を示したものである。 FIG. 9 shows a schematic diagram of the speckle noise reduction optical system 400. FIG. 10 shows a block diagram of the speckle noise reduction optical system 400.
　図９および図１０に示すように、スペックルノイズ低減光学系４００はスペックルノイズ低減光学系３００のインテグレータ２の外側にホルダ６を、ホルダ６の側面に振動部４、５を配備した点が異なる。 As shown in FIGS. 9 and 10, the speckle noise reduction optical system 400 has a holder 6 on the outside of the integrator 2 of the speckle noise reduction optical system 300 and vibration portions 4 and 5 on the side surface of the holder 6. different.
　図１０に示すように、振動部４、５は、インテグレータ２に入射するレーザ光のスペックルノイズを低減するため、インテグレータ２をホルダ６と一緒に振動させる機能を有している。 As shown in FIG. 10, the vibrating units 4 and 5 have a function of vibrating the integrator 2 together with the holder 6 in order to reduce the speckle noise of the laser beam incident on the integrator 2.
　ホルダ６は、利用するレーザ光に対して反射率の高い白色のプラスチック樹脂を適用すると良い。図１０に示すように、インテグレータ２から散乱で漏れたレーザ光をホルダ６で反射してレーザ光をリサイクルすることで効率を改善できる。図５で説明したように平均自由行程が小さくなると効率が減る。複数の光源から出射したレーザ光の均一性を確保するには、光源２１、２２、２３のｘやｙ方向の距離に強く依存する。例えば、距離が大きいと出射面の均一性が不足する可能性がある。その場合は、平均自由行程を小さくすると改善できるが効率が低減するため、ホルダ６を設けると効率改善に大きな効果が得られる。 It is preferable to apply a white plastic resin having high reflectance to the laser beam to be used for the holder 6. As shown in FIG. 10, the efficiency can be improved by reflecting the laser beam scattered from the integrator 2 by the holder 6 and recycling the laser beam. As explained in FIG. 5, the efficiency decreases as the mean free path becomes smaller. In order to ensure the uniformity of the laser light emitted from the plurality of light sources, it strongly depends on the distances of the light sources 21, 22, and 23 in the x and y directions. For example, if the distance is large, the uniformity of the exit surface may be insufficient. In that case, it can be improved by reducing the mean free path, but the efficiency is reduced. Therefore, the provision of the holder 6 has a great effect on the efficiency improvement.
　実施例５について図を用い説明する。ここでは、スペックルノイズ低減光学系４００の変形例であるスペックルノイズ低減光学系５００、について説明する。 Example 5 will be described with reference to the drawings. Here, the speckle noise reduction optical system 500, which is a modification of the speckle noise reduction optical system 400, will be described.
　図１１はスペックルノイズ低減光学系５００の概略図を示したものである。スペックルノイズ低減光学系５００はスペックルノイズ低減光学系４００のインテグレータ２の代わりにインテグレータ３１を配備した点が異なる。 FIG. 11 shows a schematic diagram of the speckle noise reduction optical system 500. The speckle noise reduction optical system 500 is different in that the integrator 31 is provided instead of the integrator 2 of the speckle noise reduction optical system 400.
　インテグレータ３１は粒子３の密度をｚ方向に異ならせており、インテグレータ３１は粒子が無い透明部３２と粒子が有る粒子部３３に分けている。 The integrator 31 has different densities of the particles 3 in the z direction, and the integrator 31 is divided into a transparent portion 32 without particles and a particle portion 33 with particles.
　光源２１ないし２３のｘやｙ方向の距離が大きい場合、粒子密度を高めて出射面の均一性を向上することが出来るが、ホルダ６を設けても入射面側に戻る戻り光をリサイクルすることができない。 When the distance between the light sources 21 to 23 in the x and y directions is large, the particle density can be increased to improve the uniformity of the exit surface, but even if the holder 6 is provided, the return light returning to the incident surface side can be recycled. I can't.
　通常の多角形ロッドは内面反射を利用してレーザ光の均一度をほぼ１００％の効率で実現できるメリットを有している。そこで透明部３２は、多角形ロッドの効率良く均一性を向上するメリットを利用して、均一度を向上したのち、粒子部３３で、均一性とスペックルノイズを低減することで、効率と均一性とスペックルノイズの低減を全て解決できる。 Ordinary polygonal rods have the advantage of being able to achieve laser beam uniformity with an efficiency of almost 100% by utilizing internal reflection. Therefore, the transparent portion 32 improves the uniformity by utilizing the merit of efficiently improving the uniformity of the polygonal rod, and then the particle portion 33 reduces the uniformity and speckle noise to achieve efficiency and uniformity. It can solve all the reduction of sex and speckle noise.
　実施例６について図を用い説明する。ここでは、スペックルノイズ低減光学系６００と、実機でスペックルノイズを評価した結果について説明する。 Example 6 will be described with reference to the drawings. Here, the speckle noise reduction optical system 600 and the result of evaluating speckle noise with an actual machine will be described.
　図１２に示すように、スペックルノイズ低減光学系６００は、スペックルノイズ低減光学系４００の振動部４、５の代わりに振動部１１を配備した点が異なる。また、光源２１、２２、２３は、光源１に置き換えた。 As shown in FIG. 12, the speckle noise reduction optical system 600 is different in that the vibration unit 11 is provided instead of the vibration units 4 and 5 of the speckle noise reduction optical system 400. Further, the light sources 21, 22 and 23 were replaced with the light source 1.
　振動部１１は、ホルダ６をベアリングに取り付け、ベアリングをＤＣモータとベルトで構成した。モータの回転数は電圧値で制御した。 The vibrating unit 11 has a holder 6 attached to a bearing, and the bearing is composed of a DC motor and a belt. The rotation speed of the motor was controlled by the voltage value.
　レーザ光の出射面側に白いスクリーン（一般的なコピー用紙）を配備し、スペックルコントラスト測定装置でスペックルノイズを計測した。スペックルコンストラスト測定装置はＯＸＩＤＥ社のＳＭ０１ＶＳ０９を用いた。光源には住友電工社のＳＬＭ－ＲＧＢ－Ｔ２０－Ｆの緑のレーザ光、波長５１５ｎｍを駆動電流は４０ｍＡで発振させた。 A white screen (general copy paper) was placed on the emission surface side of the laser beam, and speckle noise was measured with a speckle contrast measuring device. As the speckle construct measuring device, SM01VS09 manufactured by OXIDE was used. The light source was a green laser beam of SLM-RGB-T20-F manufactured by Sumitomo Electric Industries, Ltd., and a wavelength of 515 nm was oscillated at a drive current of 40 mA.
　インテグレータ２は、入射面サイズが０．８×０．６ｍｍ、長さが５．０ｍｍで、粒子３の体積密度は０．３％で、屈折率差は０．１のものを用いた。インテグレータ２は、ベアリングの回転中心に対して、約５０μｍ程度に調整して取り付けた。 The integrator 2 used had an incident surface size of 0.8 × 0.6 mm, a length of 5.0 mm, a volume density of particles 3 of 0.3%, and a refractive index difference of 0.1. The integrator 2 was adjusted and attached to about 50 μm with respect to the center of rotation of the bearing.
　図１３にスペックルノイズの計測結果を示す。横軸が回転数で、縦軸がスペックルノイズに相当するスペックルコントラストを示している。停止状態（回転数０）では、５０％を超えているスペックルコントラストが、回転数を６ｒｐｍ～２３ｒｐｍの範囲で与えたところ、全ての条件で約３％に低減したことを確認した。 FIG. 13 shows the measurement result of speckle noise. The horizontal axis shows the number of revolutions, and the vertical axis shows the speckle contrast corresponding to speckle noise. It was confirmed that the speckle contrast exceeding 50% in the stopped state (rotation speed 0) was reduced to about 3% under all conditions when the rotation speed was given in the range of 6 rpm to 23 rpm.
　図１４はスペックルノイズの画像であり、図１４（ａ）が停止時で、図１４（ｂ）が回転時（６ｒｐｍ）の条件である。スペックルノイズが低減していることが分かる。また本装置でＬＥＤ（light emitting diode）を計測するとスペックルコントラスト値が約３％であった。 FIG. 14 is an image of speckle noise, where FIG. 14 (a) is the condition when stopped and FIG. 14 (b) is the condition when rotating (6 rpm). It can be seen that the speckle noise is reduced. Moreover, when the LED (light emission diode) was measured by this device, the speckle contrast value was about 3%.
　以上より、本スペックルノイズ低減光学系では、コヒーレンシのないＬＥＤと同等のスペックルノイズに低減できているといえる。また、回転数６ｒｐｍは１０Ｈｚであり、人の可聴域２０Ｈｚよりゆっくりとした振動でスペックルノイズを低減できているといえる。 From the above, it can be said that this speckle noise reduction optical system can reduce the speckle noise to the same level as an LED without coherency. Further, the rotation speed of 6 rpm is 10 Hz, and it can be said that speckle noise can be reduced by vibration slower than the human audible range of 20 Hz.
　以上説明したように、スペックルノイズ低減光学系は、レーザ光を出射する光源１と、少なくとも粒子３が充填された透明ロッドであるインテグレータ２と、インテグレータ２または光源１を常にゼロより大きい速度で微小に振動させる振動部４、５または振動部１１とを備え、レーザ光はインテグレータ２内部を進行し、少なくとも粒子３とレーザ光が複数回衝突することでスペックルノイズを低減することができる。直線状に動かさないことで、速度ゼロを回避できる。 As described above, the speckle noise reduction optical system always emits a light source 1 that emits a laser beam, an integrator 2 that is a transparent rod filled with at least particles 3, and an integrator 2 or a light source 1 at a speed higher than zero. A vibrating unit 4, 5 or a vibrating unit 11 that vibrates minutely is provided, and the laser light travels inside the integrator 2, and speckle noise can be reduced by at least the particles 3 colliding with the laser light a plurality of times. By not moving in a straight line, zero speed can be avoided.
　また、インテグレータは直方体（インテグレータ２）または円柱（インテグレータ１０）とする。 Also, the integrator shall be a rectangular parallelepiped (integrator 2) or a cylinder (integrator 10).
　また、振動部４、５は、レーザ光の入射側に配備させている。出射側を固定して入射面側だけ振動させることで、スペックルノイズ低減光学系の後段の光学系に影響を及ぼさないようにすることが可能となる。 Further, the vibrating parts 4 and 5 are arranged on the incident side of the laser beam. By fixing the emission side and vibrating only the entrance surface side, it is possible to prevent the influence on the optical system in the subsequent stage of the speckle noise reduction optical system.
　また、振動部４，５は、少なくともレーザ光が粒子３と衝突した際に１度以上の角度変化が発生するよう振動幅とすると良い。例えば偏芯量０．５μｍで屈折率差が０．０２５時の振動幅は１μｍで達成される。 Further, the vibrating parts 4 and 5 are preferably set to have a vibrating width so that an angle change of at least 1 degree occurs when the laser beam collides with the particles 3. For example, when the eccentricity is 0.5 μm and the refractive index difference is 0.025, the vibration width is achieved at 1 μm.
　また、振動部４、５、１１は２０Ｈｚよりゆっくりとした速度で振動させる。これにより静かな装置を実現できる。 Also, the vibrating parts 4, 5 and 11 vibrate at a speed slower than 20 Hz. This makes it possible to realize a quiet device.
　また、インテグレータは前記レーザ光の進行方向の長さが５ｍｍ以下とする。
これにより小型な装置を提供できる。 Further, the integrator has a length of 5 mm or less in the traveling direction of the laser beam.
This makes it possible to provide a small device.
　粒子３は透明粒子であり、透明粒子とインテグレータの透明ロッドとは屈折率差０．０２５以上とする。これによりスペックルノイズを低減することができる。 Particle 3 is a transparent particle, and the refractive index difference between the transparent particle and the transparent rod of the integrator is 0.025 or more. As a result, speckle noise can be reduced.
　また粒子３は直径１μｍないし５μｍの範囲とする。スペックルノイズ低減光学系を安価に実現できる。 The particle 3 has a diameter in the range of 1 μm to 5 μm. A speckle noise reduction optical system can be realized at low cost.
　またインテグレータ２は、レーザ光が入射する入射面とレーザ光が出射する出射面とを備え、入射面と出射面は１ｍｍ角以下とする。このようにすることで、スペックルノイズ低減光学系の後段の光学系を設計しやすく出来る。 Further, the integrator 2 includes an incident surface on which the laser beam is incident and an emitting surface on which the laser beam is emitted, and the incident surface and the emitting surface are 1 mm square or less. By doing so, it is possible to easily design the optical system in the subsequent stage of the speckle noise reduction optical system.
　通常ＬＥＤのチップサイズは１ｍｍ角であるので、ＬＥＤの置き換えし易い効果も得られる。１ｍｍ角より大きくなるとエタンデューが大きくなり後段光学系を設計で効率のロスが大きくなる。 Normally, the LED chip size is 1 mm square, so the effect of easy replacement of the LED can be obtained. If it is larger than 1 mm square, the etendue becomes large and the efficiency loss becomes large when designing the subsequent optical system.
　また、インテグレータに充填された粒子３の体積密度は、０．１％ないし５％の範囲とする。 The volume density of the particles 3 filled in the integrator shall be in the range of 0.1% to 5%.
　また、インテグレータ２のレーザ光の進行する方向の側面は、漏れ出たレーザ光をインテグレータ２にリサイクルする反射面（ホルダ６に相当）を配備させる。 Further, on the side surface of the integrator 2 in the direction in which the laser beam travels, a reflective surface (corresponding to the holder 6) for recycling the leaked laser beam to the integrator 2 is provided.
　また、光源２１、２２、２３は、少なくとも波長の異なる複数のレーザ光を出射する。これにより表示装置用の小型光源装置として利用できる。 Further, the light sources 21, 22, and 23 emit at least a plurality of laser beams having different wavelengths. As a result, it can be used as a small light source device for a display device.
　また、複数のレーザ光の出射点を異ならせている。これは、光源２１、２２、２３のように同じ出射点ではないことである。 Also, the emission points of multiple laser beams are different. This means that they are not the same exit point as the light sources 21, 22, and 23.
　また、インテグレータ３１のように粒子密度は、レーザ光の進行方向に、異ならせてもよい。これにより、効率を改善できる。 Further, the particle density may be different in the traveling direction of the laser beam as in the integrator 31. This can improve efficiency.
　なお、本実施例のスペックルノイズ低減光学系では、光源から直接インテグレータにレーザ光が入射することを想定しているが、例えば、光源１とインテグレータ２の間にレンズやミラーを配置してもなんら構わない。 In the speckle noise reduction optical system of this embodiment, it is assumed that the laser beam is directly incident on the integrator from the light source. For example, even if a lens or a mirror is arranged between the light source 1 and the integrator 2. I don't care.
　テレビやプロジェクタなどの表示装置に利用が可能である。 It can be used for display devices such as TVs and projectors.
　１、２１、２２、２３：光源
　２、１０、３１：インテグレータ
　３：粒子
　４、５、１１：振動部
　６：ホルダ
　１００、２００、３００、４００、５００、６００：スペックルノイズ低減光学系
　３２：透明部
　３３：粒子部 1, 21, 22, 23: Light source 2, 10, 31: Integrator 3: Particles 4, 5, 11: Vibrating part 6: Holder 100, 200, 300, 400, 500, 600: Speckle noise reduction optical system 32: Transparent part 33: Particle part

Claims (15)

  1. 　レーザ光を出射する光源と、
    　粒子が少なくとも一部に充填された、前記レーザ光に対して透明なインテグレータと、
    　前記レーザ光を前記インテグレータに対して、ゼロより大きい速度で相対的に振動させる振動部と、を備え、
    　前記レーザ光は前記インテグレータの内部を進行し、
    　前記インテグレータから射出するレーザ光のスペックルノイズを低減することを特徴とする、スペックルノイズ低減光学系。     A light source that emits laser light and
    An integrator that is transparent to the laser beam and is filled with particles at least in part.
    A vibrating portion that vibrates the laser beam relative to the integrator at a speed greater than zero.
    The laser beam travels inside the integrator and
    A speckle noise reduction optical system characterized by reducing speckle noise of laser light emitted from the integrator.
  2. 　請求項１記載のスペックルノイズ低減光学系であって、
    　前記インテグレータは直方体または円柱であることを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to claim 1.
    The speckle noise reduction optical system, wherein the integrator is a rectangular parallelepiped or a cylinder.
  3. 　請求項１記載のスペックルノイズ低減光学系であって、
    　前記振動部は、前記光源、前記インテグレータ、および前記光源と前記インテグレータの間の光路中のレーザ光の少なくとも一つを振動させることを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to claim 1.
    The speckle noise reduction optical system, characterized in that the vibrating portion vibrates at least one of the light source, the integrator, and a laser beam in an optical path between the light source and the integrator.
  4. 　請求項３記載のスペックルノイズ低減光学系であって、
    　前記振動部は、前記インテグレータの前記レーザ光の出射側よりも前記レーザ光の入射側に近い位置に配備されたことを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to claim 3.
    The speckle noise reduction optical system is characterized in that the vibrating portion is arranged at a position closer to the incident side of the laser beam than the emitting side of the laser beam of the integrator.
  5. 　請求項１～４のいずれかに記載のスペックルノイズ低減光学系であって、
    　前記振動部は、少なくとも前記レーザ光が前記粒子と衝突した際に１度以上の角度変化が発生するような振動幅を与えることを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to any one of claims 1 to 4.
    The speckle noise reduction optical system is characterized in that the vibrating portion provides a vibrating width such that an angle change of at least one degree occurs when the laser beam collides with the particles.
  6. 　請求項１～５のいずれかに記載のスペックルノイズ低減光学系であって、
    　前記振動部は２０Ｈｚより低い周波数で振動させることを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to any one of claims 1 to 5.
    A speckle noise reduction optical system characterized in that the vibrating portion vibrates at a frequency lower than 20 Hz.
  7. 　請求項１～６のいずれかに記載のスペックルノイズ低減光学系であって、
    　前記インテグレータは、前記レーザ光の進行方向の長さが５ｍｍ以下であることを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to any one of claims 1 to 6.
    The integrator is a speckle noise reduction optical system characterized in that the length of the laser beam in the traveling direction is 5 mm or less.
  8. 　請求項１～７のいずれかに記載のスペックルノイズ低減光学系であって、
    　前記粒子は透明粒子であり、該透明粒子と前記インテグレータとは屈折率差が０．０２５以上あることを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to any one of claims 1 to 7.
    A speckle noise reduction optical system, wherein the particles are transparent particles, and the difference in refractive index between the transparent particles and the integrator is 0.025 or more.
  9. 　請求項１～８のいずれかに記載のスペックルノイズ低減光学系であって、
    　前記粒子の直径は１μｍないし５μｍの範囲であることを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to any one of claims 1 to 8.
    A speckle noise reduction optical system characterized in that the diameter of the particles is in the range of 1 μm to 5 μm.
  10. 　請求項１～９のいずれかに記載のスペックルノイズ低減光学系であって、
    　前記インテグレータは、
    　前記レーザ光が入射する入射面と、
    　前記レーザ光が出射する出射面とを備え、
    　前記入射面と出射面は１ｍｍ角以下としたことを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to any one of claims 1 to 9.
    The integrator
    The incident surface on which the laser beam is incident and
    It is provided with an exit surface from which the laser beam is emitted.
    A speckle noise reduction optical system characterized in that the entrance surface and the exit surface are 1 mm square or less.
  11. 　請求項１～１０のいずれかに記載のスペックルノイズ低減光学系であって、
    　前記インテグレータに充填された粒子密度は、体積密度換算で０．１％ないし５％の範囲であることを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to any one of claims 1 to 10.
    A speckle noise reduction optical system characterized in that the particle density filled in the integrator is in the range of 0.1% to 5% in terms of volume density.
  12. 　請求項１～１１のいずれかに記載のスペックルノイズ低減光学系であって、
    　前記インテグレータの前記レーザ光の進行する方向の側面は、
    　漏れ出た前記レーザ光を前記インテグレータにリサイクルする反射面を配備したことを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to any one of claims 1 to 11.
    The side surface of the integrator in the direction in which the laser beam travels is
    A speckle noise reduction optical system characterized in that a reflecting surface for recycling the leaked laser beam to the integrator is provided.
  13. 　請求項１～１２のいずれかに記載のスペックルノイズ低減光学系であって、
    　前記光源は、少なくとも波長の異なる複数のレーザ光を出射することを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to any one of claims 1 to 12.
    The light source is a speckle noise reduction optical system characterized by emitting a plurality of laser beams having at least different wavelengths.
  14. 　請求項１３記載のスペックルノイズ低減光学系であって、
    　前記複数のレーザ光の出射点を異ならせたことを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to claim 13.
    A speckle noise reduction optical system characterized in that the emission points of the plurality of laser beams are different.
  15. 　請求項１～１４のいずれかに記載のスペックルノイズ低減光学系であって、
    　前記粒子の前記インテグレータ内の密度を、前記レーザ光の進行方向に異ならせたことを特徴とする、スペックルノイズ低減光学系。     The speckle noise reduction optical system according to any one of claims 1 to 14.
    A speckle noise reduction optical system characterized in that the density of the particles in the integrator is made different in the traveling direction of the laser beam.
PCT/JP2019/044685 2019-03-26 2019-11-14 Speckle noise reduction optical system WO2020194850A1 (en)

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Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007013221A1 (en) * 2005-07-28 2007-02-01 Matsushita Electric Industrial Co., Ltd. Laser image display, and optical integrator and laser light source package used in such laser image display
WO2007032216A1 (en) * 2005-09-14 2007-03-22 Matsushita Electric Industrial Co., Ltd. Image forming device
WO2008041559A1 (en) * 2006-10-02 2008-04-10 Panasonic Corporation Flat panel lighting system and liquid crystal display device using the same
CN102053384A (en) * 2011-01-29 2011-05-11 中北大学 Speckle elimination device based on field emission deformation polymer
CN102213839A (en) * 2011-06-21 2011-10-12 西安邮电学院 Laser speckle eliminating device with dodging function
JP2012145804A (en) * 2011-01-13 2012-08-02 Seiko Epson Corp Projector

Patent Citations (6)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
WO2007013221A1 (en) * 2005-07-28 2007-02-01 Matsushita Electric Industrial Co., Ltd. Laser image display, and optical integrator and laser light source package used in such laser image display
WO2007032216A1 (en) * 2005-09-14 2007-03-22 Matsushita Electric Industrial Co., Ltd. Image forming device
WO2008041559A1 (en) * 2006-10-02 2008-04-10 Panasonic Corporation Flat panel lighting system and liquid crystal display device using the same
JP2012145804A (en) * 2011-01-13 2012-08-02 Seiko Epson Corp Projector
CN102053384A (en) * 2011-01-29 2011-05-11 中北大学 Speckle elimination device based on field emission deformation polymer
CN102213839A (en) * 2011-06-21 2011-10-12 西安邮电学院 Laser speckle eliminating device with dodging function

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