JP2010281904A - Image display - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To display images without any color unevenness or bleeding. <P>SOLUTION: The image display includes N light sources for emitting light beams of wavelengths λ<SB>n</SB>(where n=1, ..., N; N is an integer of 3 or more; and λ<SB>1</SB>...>λ<SB>n</SB>...>λ<SB>N</SB>...); coupling lenses for coupling light beams from the light sources; and rotating mirrors for reflecting and scanning light fluxes from the coupling lenses. The image display includes projection lenses, projecting on the projection face, light fluxes by emitting the light fluxes reflected on the light mirrors as projection light beams being substantially in parallel, and forms beam waists concerning the light fluxes emitted from the projection lenses, and the beam diameter w<SB>n</SB>of the beam waist is such that w<SB>1</SB>...>w<SB>n</SB>...>w<SB>N</SB>holds. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an image display device that projects an image on a projection surface.

In recent years, there has been a lot of development of projection type image display devices (for example, “projectors”) using LEDs, lasers, and the like, and they are expected as small and portable projectors. In particular, scanning type small projectors combining three primary color (RGB) lasers and MEMS (Micro Electro Mechanical Systems) mirrors have few components, and many developments are progressing because they can be miniaturized. It has been. (For example, refer to Patent Document 1).
FIG. 1 shows a conventional example of a scanning projector comprising such three primary color lasers and a MEMS mirror. A conventional scanning projector will be briefly described. The light sources 505-R, 505-G, and 505-B emit R (red), G (green), and B (blue) laser beams A _R , A _G , and A _B , respectively. The lenses 506-R, 506-G, and 506-B collect the laser beams A _R , A _G , and A _B. The dichroic mirrors 507-R, 507-G, and 507-B reflect only red light, green light, and blue light, respectively, and transmit other light. The MEMS mirror 501 has a variable tilt angle by being rotated in the horizontal direction and the vertical direction. The MEMS mirror 501 projects an image on the projection surface 503 by reflecting red light, green light, and blue light from the dichroic mirrors 507-R, 507-G, and 507-B. The control circuit 502 rotates the MEMS mirror 501 in the horizontal direction and the vertical direction, and emits laser light whose light intensity is modulated from the light sources 505-R, 505-G, and 505-B in accordance with the input video signal VIN. .
Other image display devices are described in Patent Document 2 or 3 or the like.

  In a projector using a laser beam as a light source (Patent Documents 1, 2, and 3), in order to obtain a color image without blur on the screen, the beam diameters of the three colors on the screen must be equivalent. is there. Since the distance from the projector to the screen is determined by the size of the image projected on the screen, the beam diameters of the three colors on the screen are within the usable range regardless of the distance from the projector to the screen. It must be the same size.

In order to solve the above problems, each of the image display apparatuses according to the present embodiment has a wavelength λ _n (where n = 1... N, N is an integer of 3 or more, and λ _1. > Λ _n ...> Λ _N ) N light sources, a coupling lens for coupling the laser light, optical path synthesis means for synthesizing the optical paths of the laser light, and A rotating mirror that scans the laser beam combined in one optical path; and a projection lens that projects the reflected light from the rotating mirror onto a projection surface. A beam waist forms a light beam emitted from the projection lens. and, the beam diameter _{w n} at the beam _waist, characterized in that it is a _{w 1 ···> w n ···>} w n.

  With the image display device of the present invention, an image without color unevenness or color blur is projected onto the projection surface.

It is a figure which shows the function structural example of the conventional image display apparatus. It is a figure which shows the function structural example of the image display apparatus of a present Example. It is a perspective view of a MEMS mirror. It is the figure which showed the optical path of the reflective surface of a mirror, and a projection lens. FIG. 10 is a diagram illustrating a functional configuration example of an image display device according to a third embodiment. It is the figure which showed the front of the restriction | limiting part. It is the figure which showed the surface of the diffraction grating. It is the figure which showed the optical path of the coupling lens. FIG. 10 is a diagram illustrating a functional configuration example of an image display device according to a fifth embodiment. It is the figure which showed the optical path of the condensing lens. FIG. 10 is a diagram illustrating a functional configuration example of an image display device according to a sixth embodiment. It is the figure which showed the optical path of the restriction | limiting part. It is a figure which shows a mode that a beam diameter increases as it distances from a beam waist. FIG. 14A is a diagram showing the beam diameter when the conventional image display device is used in Comparative Experiment 1, and FIG. 14B is the beam when the image display device of this embodiment is used. It is the figure which showed the diameter. FIG. 15A is a diagram showing the beam diameter when the conventional image display device is used in Comparative Experiment 2, and FIG. 15B is the beam when the image display device of this embodiment is used. It is the figure which showed the diameter. It is a figure which shows that the light beam from a restriction | limiting part is reflected by the reflective surface of a MEMS mirror.

  DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments for carrying out the present invention will be described with reference to the drawings. In addition, the same number is attached | subjected to the process which performs the structure part which has the same function, and the same process, and duplication description is abbreviate | omitted.

FIG. 2 shows a functional configuration example of the image display apparatus 200 according to the first embodiment. The image display apparatus 200 according to the first embodiment includes a control circuit 100, a light source 1 that emits red light (wavelength λ ₁ ), a light source 2 that emits green light (wavelength λ ₂ ), and blue light (wavelength). λ ₃ ), a light source 3, coupling lenses 4, 5, 6, an optical path synthesis unit 7, a rotating mirror 11, and a projection lens 12. The image display device 200 displays the light emitted from the three light sources 1, 2, and 3 on the projection plane 13. The image display device 200 is, for example, a laser scanning projector. In the following embodiment, a case where there are three light sources (RGB) will be described, but the same can be applied to a case where there are four or more light sources. Moreover, the rotation mirror 11 is the MEMS mirror 11, for example.
The control circuit 100 performs at least mirror control means for controlling the rotation of the MEMS mirror 11 and intensity modulation of the laser light projected on the projection surface 13. When the control circuit 100 receives the video signal VIN, the laser light whose light intensity is modulated in accordance with the video signal of each color of the video signal VIN (for example, the red video signal, the blue video signal, and the green video signal) 3 is emitted.

  The coupling lenses 4, 5, 6 are arranged so as to correspond to the light sources 1, 2, 3. Light emitted from the light sources 1, 2, and 3 is divergent light and is incident on the corresponding coupling lenses 4, 5, and 6, respectively. The coupling lenses 4, 5, 6 convert the incident diverging light into convergent light and emit it. The light beam converted into convergent light is incident on the optical path synthesis means 7. The optical path synthesizing unit 7 converts a plurality of optical paths into one optical path, and is, for example, an optical path synthesizing prism. The optical path combining means 7 has three reflecting surfaces 8, 9, and 10.

The junction 8 is formed with a dichroic film that reflects a red light beam and transmits a green light beam and a blue light beam. The junction 9 is formed with a dichroic film that reflects the green light beam and transmits the blue light beam. The reflecting surface 10 reflects the blue light beam. In this way, the optical path combining unit 7 combines the three optical paths into one optical path. The light beam combined into one optical path by the optical path combining unit 7 is reflected by the reflection surface 14 of the MEMS mirror 11. The MEMS mirror will be briefly described.
FIG. 3 shows a perspective view of a configuration example of the MEMS mirror 11. The MEMS mirror 11 has a structure in which a minute mirror 101 having a reflecting surface is supported by torsion bars 102 and 103. By the mirror control of the control circuit 100, the micro mirror 101 is rotated in two axial directions orthogonal to each other. More specifically, when the torsion bar 102 is twisted, the reciprocating motion is performed in the rotational direction (α direction) about the shaft 104. Further, when the torsion bar 103 is twisted, reciprocating motion is performed in the rotation direction (β direction) about the shaft 105. By the reciprocating motion about both the axes 104 and 105, the normal direction of the reflecting surface of the micromirror 101 changes two-dimensionally.

  For this reason, the reflection direction of the light beam incident on the micromirror 101 changes, and the light beam can be scanned in a two-dimensional direction. In the example of FIG. 2, the rotation is performed in the rotation direction (α direction) about the axis 104 penetrating from the front of the paper to the back side (α direction) and in the rotation direction (β direction) about the axis 105 perpendicular to the shaft 104. The image is displayed two-dimensionally on the projection surface 13. Then, the combined light beam reflected by the mirror 11 is incident on the projection lens 12.

The projection lens 12 emits the combined light beam as substantially parallel light and projects it onto the projection surface 13.
Here, if the projection light emitted from the projection lens 12 is completely parallel light, the beam diameter on the projection surface 13 becomes constant even if the distance D between the projection lens 12 and the projection surface 13 changes, and color unevenness or An image without blur can be displayed. However, the light is diffracted when propagating, and the beam spreads in the direction orthogonal to the traveling direction, and it is impossible to make perfect parallel light by the projection lens 12. That is, as the distance D increases, the beam diameter on the projection surface 13 increases. The distance D is not fixed, but the distance D is increased when a large image is desired, and the distance D is decreased when an image is projected most recently. When the projection light from the projection lens 12 is convergent light or divergent light, the change in the beam diameter on the projection surface 13 increases due to the change in the distance D, and the change in the distance on the projection surface 13 with respect to the propagation distance D. In order to suppress the change in the beam diameter, it is desirable that the projection lens 12 is a concave lens and the projection light is substantially parallel light.

In general, a beam (light) used in a projector such as the image display apparatus of this embodiment is a Gaussian beam. The Gaussian beam has a Gaussian distribution of radiation intensity in the cross section, and at the beam waist, it becomes a completely parallel plane wave, and the beam diameter is minimized.
Even if the wavefront of the Gaussian beam is a perfect plane at a certain position, the wavefront diverges with the curvature given by the following equation (1). That is, the following equation (1) represents the beam radius w (z) at 1 / e ² intensity at the propagation distance z.

ただし、ｚはビームウエストからの距離であり、ｗ_０は波面が平面である位置（ビームウエスト）でのビーム半径であり、λは波長である。ここで、ビーム径（ビームの直径）とは、ビームの放射強度が、光軸上の値の１／ｅ^２（＝約１３．５％）になる直径とする。ｅは自然対数である。また、プロジェクタ光学系では、ｚ＞＞ｗ_０であるから式（１）は、以下の式（２）に近似できる。
ｗ（ｚ）＝λｚ／πｗ₀ （２）
本発明の凹レンズ１２を出射した、波長λ_１、λ_２、λ_３（λ_１＞λ_２＞λ_３）の光の波面が平面である位置での１／ｅ^２強度のビーム半径をそれぞれ、ｗ_１、ｗ_２、ｗ_３とすれば、式（２）より、伝播距離ｚの位置で各波長のビーム径の差を小さくするためには、λ_１＞λ_２＞λ_３であるから、
ｗ_１＞ｗ_２＞ｗ_３ （３）
である必要がある。
上記式（３）を満たすような画像表示装置１００であれば、色むらやにじみの少ない画像が投影面１３上で投影される。
また、以下の実施例２〜７では、上記式（３）を満たすための様々な実施例を説明する。

Where z is the distance from the beam waist, w ₀ is the beam radius at the position (beam waist) where the wavefront is a plane, and λ is the wavelength. Here, the beam diameter (beam diameter) is a diameter at which the radiation intensity of the beam is 1 / e ² (= about 13.5%) of the value on the optical axis. e is a natural logarithm. In the projector optical system, since z >> w ₀ , the equation (1) can be approximated to the following equation (2).
w (z) = λz / πw ₀ (2)
The beam radii of 1 / e ² intensity at the position where the wavefront of the light having the wavelengths λ ₁ , λ ₂ , λ ₃ (λ ₁ > λ ₂ > λ ₃ ) emitted from the concave lens 12 of the present invention is a plane, respectively, Assuming w ₁ , w ₂ , and w ₃ , λ ₁ > λ ₂ > λ ₃ from Equation (2), in order to reduce the difference in beam diameter of each wavelength at the position of the propagation distance z,
w ₁ > w ₂ > w ₃ (3)
Need to be.
If the image display device 100 satisfies the above formula (3), an image with little color unevenness and blurring is projected on the projection surface 13.
In Examples 2 to 7 below, various examples for satisfying the above formula (3) will be described.

In the second embodiment, a configuration in which the beam diameter on the reflecting surface 14 of the MEMS mirror 11 is focused in order to satisfy the above formula (3) will be described. Since the image display apparatus of Example 2 is the same as that shown in FIG.
FIG. 4 shows the beam radius of the emitted light from the concave lens 12 and the state of the light beam on the reflecting surface 14 of the MEMS mirror 11. In order to satisfy w1>w2> w3, assuming that the beam radii of the converged light of wavelengths λ1, λ2, and λ3 incident on the reflecting surface 14 of the MEMS mirror 11 are φ ₁ , φ ₂ , and φ ₃ , It is necessary to satisfy.
φ ₁ > φ ₂ > φ ₃ (4)
If the beam radii φ ₁ , φ ₂ , and φ ₃ incident on the reflecting surface 14 are set so as to satisfy this formula (4), the beam diameters of the respective colors on the projection surface 13 become equal, and as a result, color unevenness and blurring occur. It is possible to display an image with little.

  In the description of FIG. 4, the beam diameters of the light emitted from the projection lens 12 do not coincide with each other. However, as can be understood from FIGS. 14B and 15B, which will be described later, a certain propagation distance. Then, the beam diameters of the respective colors coincide.

In the first embodiment, the user needs to adjust the beam radii φ ₁ , φ ₂ , and φ ₃ on the reflecting surface 14 in order to satisfy the above formula (4). In the third embodiment, an image display apparatus 300 that does not require the user himself to adjust the beam radii φ ₁ , φ ₂ , and φ ₃ by providing a limiting unit will be described. FIG. 5 shows a functional configuration example of the image expression apparatus 300. The image display device 300 is different from the image display device 100 in that a limiting unit 19 is provided between the optical path synthesis unit 7 and the mirror 11. Similarly to the second embodiment, the coupling lenses 4, 5, and 6 of the third embodiment use diverging light from the laser light source as convergent light.
As shown in FIG. 16, the converging light 50 of wavelengths λ1, λ2, and λ3 synthesized into one optical path by the optical path synthesizing unit 7 is transmitted through the limiting unit 19 and is incident on the reflecting surface 14 of the MEMS mirror 11. radius, the λ1 to [psi _1, the lambda ₂ in [psi _2, in which the λ3 with _{ψ 3 (ψ 1> ψ 2} > ψ 3). FIG. 6 shows a view of the limiting unit 19 viewed from the xy plane. The region 54 consisting of four regions 54, 55, 56 and 57, and the region 54 outside the diameter γ1 is a region coated with a reflection coating or covered with a non-transparent material so as not to transmit light of wavelengths λ1, λ2, and λ3. The region 55 surrounded by the diameters γ1 and γ2 is subjected to dichroic coating that transmits only light of λ1 and reflects the light of λ2 and λ3, and the region surrounded by the diameters γ2 and γ3 is λ1 A dichroic coat that transmits light of λ2 and reflects light of λ3 is applied, and an antireflection coat is applied to the inside of the diameter γ3 so as to transmit light of λ1, λ2, and λ3. By setting the diameters of γ1, γ2, and γ3 of the limiting unit 19 to predetermined values, the beam diameters incident on the reflecting surface 14 of the MEMS mirror 11 can be set to predetermined values ψ ₁ , ψ ₂ , and ψ ₃ .
Further, in the limiting unit 19, a diffraction grating may be used instead of the dichroic coat. Specifically, in FIG. 6, the region 54 outside the diameter γ1 is a region coated with a reflection coating or covered with a non-transparent material so that light of wavelengths λ1, λ2, and λ3 is not transmitted. A diffraction structure for transmitting only light of λ1 and diffracting light of λ2 and λ3 is formed in a region 55 surrounded by γ1 and diameter γ2, and a region 56 surrounded by the diameters γ2 and γ3 is formed of λ1 and λ2. By forming a diffractive structure that transmits light and diffracts light of λ3, the diameters of γ1, γ2, and γ3 of the limiting portion 19 are set to predetermined values, and are incident on the reflecting surface 14 of the MEMS mirror 11. The beam diameter can be set to a predetermined value ψ ₁ , ψ ₂ , ψ ₃ . FIG. 7 shows the surface of the limiting portion 19 when the diffraction grating 190 is used. As shown in FIG. 7, a groove 190a having a depth d is formed. This depth d is different for each of the regions 55 and 56. The refractive index of the material forming the diffractive structure is n1, n2, and n3 with respect to the wavelengths λ1, λ2, and λ3, respectively. Note that the region 57 does not need to form a diffraction grating because it transmits light of all wavelengths.
The depths d ₁ and d ₂ of the regions 55 and 56 may be determined as follows.
Regarding the depth d ₁ of the region 55,
n ₁ (d ₁ −1) / λ ₁ = P ₁ (5)
n ₂ (d ₁ −1) / λ ₂ ≠ P ₂ (6)
n ₃ (d ₁ −1) / λ ₃ ≠ P ₃ (7)
However, P ₁ , P ₂ , and P ₃ are natural numbers. The depth d ₁ may be set so as to satisfy the expressions (5) to (7) and increase the diffraction efficiency of the light beams having the wavelengths λ 2 and λ 3.
Similarly, the depth _{d 2} of the region 56,
n ₁ (d ₂ −1) / λ ₁ = P ₄ (8)
n ₂ (d ₂ −1) / λ ₂ = P ₅ (9)
n ₃ (d ₂ −1) / λ ₃ ≠ P ₆ (10)
However, P ₄ , P ₅ , and P ₆ are natural numbers. As the diffraction efficiency of the light flux of the wavelength λ3 satisfies the equation (8) to (10) is increased, it may be set the depth d _2.
By using the limiting unit 19 in this way, it is possible to easily obtain a light beam that satisfies the above formula (4). Further, the surface shown in FIG. 6 and the diffraction structure shown in FIG. 7 may be provided on either the entrance surface or the exit surface of the limiting portion 19. Further, the limiting unit 19 using a diffraction grating is less expensive than the limiting unit 19 using a dichroic coat.

In Example 4, attention is paid to the distances L ₁ , L ₂ , and L ₃ between the coupling lenses 4, 5, and 6 and the reflecting surface 14 in order to satisfy the above formula (3). The functional configuration example of the image display apparatus according to the fourth embodiment is the same as that shown in FIG.

FIG. 8 shows an optical path when the reflecting surface 14 is arranged at the positions E, F, and G. Further, the distances from the coupling lens 4 to the positions E, F, and G are H, I, and J, respectively. However, H <I <J. Let τ ₁ , τ ₂ , and τ ₃ be the beam radii of the reflected light when the reflecting surface 14 is disposed at the positions E, F, and G, respectively.
In general, as shown in FIG. 8, the distance between the coupling lens 4 and the reflecting surface 14 is inversely related to the beam diameter of the light reflected by the reflecting surface 14. That is, when H <I <J, τ ₁ <τ ₂ <τ ₃ (hereinafter referred to as “Principle A”).
In order to satisfy the above formula (4), when this principle A is used, the same effect as in the first embodiment can be obtained if the following formula (11) is satisfied.
L ₁ <L ₂ <L ₃ (11)
Naturally, the above formula (3) is satisfied.

  FIG. 9 shows an image display apparatus 400 according to the fifth embodiment. The image display device 400 is different from the image display device 100 in that the condenser lens 18 is provided. In the example of FIG. 9, the condenser lens 18 is provided between the optical path synthesis unit 7 and the mirror 11. The coupling lenses 21, 22, and 23 emit diverging light from the light sources 1, 2, and 3 as parallel light.

The parallel light flux that has been made one optical path by the optical path synthesizing unit 7 is converted into convergent light by the condenser lens 18 and projected onto the projection surface 13 through the projection lens 12.
FIG. 10 shows the condenser lens 18 and the reflecting surface 14 of the MEMS mirror 11. The beam radii on the reflecting surface 14 of the light beams having wavelengths λ ₁ , λ ₂ , and λ ₃ are ρ ₁ , ρ ₂ , and ρ ₃ , respectively, and the beam diameters on the incident surface of the condenser lens 18 are ψ ₁ , ψ ₂ , and ψ _3. However, it is assumed that ρ ₁ > ρ ₂ > ρ ₃ . As shown in FIG. 10, the beam diameters ψ ₁ , ψ ₂ , ψ ₃ of the parallel light incident on the condenser lens 18 and the beam radii ρ ₁ , ρ ₂ , ρ ₃ on the MEMS mirror 11 reflecting surface 14 are larger or smaller. Match.
To make the beam diameter on the projection plane 13 the same regardless of the projection distance D when projected onto the projection plane 13,
ρ ₁ > ρ ₂ > ρ ₃
It is necessary to satisfy the following expression (12) as a result.
ψ ₁ > ψ ₂ > ψ ₃ (12)
The coupling lenses 21, 22, and 23 use divergent light as parallel light. Therefore, the distance from the coupling lenses 21, 22, 23 to the condenser lens 18 can be set freely. Further, since the condensing lens 18 condenses parallel light, the beam radii ρ ₁ , ρ ₂ , and ρ ₃ on the reflection surface of the MEMS mirror 11 can be set only by the design of the condensing lens 18.

FIG. 11 shows a functional configuration example of the image display apparatus 500 of the sixth embodiment. The image display device 500 is different from the image display device 400 in that the limiting unit 19 described in the third embodiment is provided between the optical path synthesis unit 7 and the condenser lens 18.
FIG. 12 shows an optical path for the limiting unit 19 and the condenser lens 18. As shown in FIG. 12, the restricting unit 19 allows the beam diameters of the parallel light 60 from the optical path synthesizing unit 7 to pass through as ψ ₁ , ψ ₂ , and ψ ₃ that satisfy the above formula (12), respectively.
By providing the limiting unit 19 in this way, the user can easily set the beam diameters ψ ₁ , ψ ₂ , ψ ₃ of the parallel light on the incident surface of the condenser lens 18.

  In the seventh embodiment, a principle for eliminating further color unevenness and blurring of the image projected by the image display device described in the first to fifth embodiments will be described.

FIG. 13 shows how the beam radius w (z) increases as the distance from the beam waist increases. The vertical axis is w (z) / w ₀ and the horizontal axis is z / w ₀ . Alternatively, the solid line indicates the 1 / e ² radiation intensity plane, and the broken line indicates the half apex cone where w (z) / w ₀ is asymptotic.
In the case of a projection type projector, the propagation distance z to the projection surface is sufficiently larger than πw ² / λ, and therefore asymptotically approaches a cone indicated by a broken line in FIG. Further, for each projection light of wavelengths λ ₁ , λ ₂ , and λ ₃ , the half apex angle (beam divergence angle) ε of this cone is small, so tan ε≈ε, and ε is expressed by the equation (3). It is represented by (13).
ε = w (z) / z = λ / πw (13)
If the spread angles ε with respect to the propagation distance z of the projection light are set to be substantially the same, the beam diameter of the projection light on the projection surface 13 can be made substantially the same at any propagation distance z. Therefore, the following equation should be satisfied from equation (13).

λ ₁ / w ₁ ≈λ ₂ / w ₂ ≈λ ₃ / w ₃ (14)
If the image display devices described in Examples 1 to 6 are configured so as to satisfy the above formula (14), an image with less blur and uneven color can be displayed.
[simulation result]
14A and 14B show the results of comparison simulation 1 between the conventional image display device and the image display device 100 (see Example 1) set to satisfy the above formula (14). 15A and 15B show the results of the comparison simulation 2 between the conventional image display device and the image display device 400 (see Example 4) set to satisfy the above equation (14). 14A shows the result of the conventional image display device, and FIG. 15A shows the result of the conventional image display device using the condensing lens 18, and FIG. 14B shows the above formula (14). ) And FIG. 15B shows the result of the image display device 400 using the condenser lens 18 set to satisfy the above formula (14).
In both comparative simulations, the light used is red, green, and blue, and the respective wavelengths are λ1 = 640 nm, λ2 = 530 nm, and λ3 = 445 nm. As shown in FIG. 2, the emission surface 12 a of the projection lens 12 is set to the origin 0, and the distance f from the origin 0 is set. 14A and 14B and 15A and 15B, the vertical axis is the beam diameter w (f), and the horizontal axis is the propagation distance f.
FIG. 14A shows the result of a conventional image display device designed to satisfy φ ₁ <φ ₂ <φ ₃ (that is, the above equation (4) is not satisfied). As can be understood from FIG. 14A, since the above formula (4) is not satisfied, the beam diameters on the projection surface 13 cannot be made coincident with each other, and the beam diameter is determined with respect to the propagation distance f. The way of spreading will also be different.
FIG. 14B satisfies the above formula (4) φ1>φ2> φ3, and satisfies the above formula (13), λ1 / w1≈λ2 / w2≈λ3 / w3≈4.3 × 1e−3. This is a result of the image display device 100 designed as described above. As can be understood from FIG. 14B, since the above equations (4) and (14) are satisfied, the beam diameters on the projection surface 13 are made substantially coincident, and the beam with respect to the propagation distance f. The method of expanding the diameter can be made substantially the same. Therefore, the image projected on the projection surface 13 can be an image with little color unevenness and blurring.
FIG. 15A shows the result of a conventional image display device designed so that φ ₁ = φ ₂ = φ ₃ (that is, the above equation (4) is not satisfied). Figure 15 As can be understood from (A), in the case where the diameter of the parallel light light A _n be the same, because it does not satisfy the above expression (4), to match the beam diameter on the projection plane 13 In addition, the beam diameter spreads differently with respect to the propagation distance f.
FIG. 15B satisfies the above formula (4) φ1>φ2> φ3, and satisfies the above formula (14), λ1 / w1≈λ2 / w2≈λ3 / w3≈4.3 × 1e−3. This is a result of the image display device 400 designed as described above. As can be understood from FIG. 14B, since the above formulas (5) and (14) are satisfied, the beam diameters on the projection surface 13 are substantially matched, and the beam with respect to the propagation distance f. The method of expanding the diameter can be made substantially the same. Therefore, the image projected on the projection surface 13 can be an image with little color unevenness and blurring.

1, 2, 3 Light source 4, 5, 6, 21, 22, 23 Coupling lens 7 Optical path synthesizing means 11 MEMS mirror 12 Projection lens 13 Projection surface 14 Mirror reflection surface 18 Condensing lens 19 Limiting unit

Japanese Patent No. 4031481 JP 2008-304726 A JP 2008-164955 A

Claims (10)

Each emits a laser beam having a wavelength λ _n (where n = 1,..., N, N is an integer of 3 or more, and λ ₁ ...> Λ _n ... Λ _N ). N light sources to
A coupling lens for coupling laser light from the laser light source;
Optical path combining means for combining the optical paths of the laser light into one;
A rotating mirror that scans the laser beam synthesized in one optical path;
In an image display device comprising a projection lens that projects the reflected light of the rotating mirror onto a projection surface,
The diameter of the beam waist of the light beam emitted from the projection lens, when the beam waist diameter of the laser beam having a wavelength lambda _n was w _n,
w ₁ ...> w _n ...> w _N
An image display device characterized by that. The coupling for coupling the light of wavelength λ _n and the optical path length L _{n to} the reflecting surface of the rotating mirror are:
L ₁ ... <L _n , ... <L _N
The image display device according to claim 1, wherein: The beam diameter φ _n of the wavelength λ _n incident on the reflecting surface of the rotating mirror is:
_{φ 1 ···> φ n ···>} φ N
The image display device according to claim 1, wherein the image display device is an image display device. The beam diameter φ _n of the wavelength λ _n incident on the reflecting surface of the rotating mirror is
_{φ 1 ···> φ n ···>} φ N
The image display apparatus according to claim 1, further comprising a limiting unit. Each emits a laser beam having a wavelength λ _n (where n = 1,..., N, N is an integer of 3 or more, and λ ₁ ...> Λ _n ... Λ _N ). N light sources to
A coupling lens that couples the laser light from the laser light source into parallel light;
Optical path combining means for combining the optical paths of the laser light into one;
A condenser lens that uses the parallel light combined in one optical path as convergent light;
A rotating mirror that scans the convergent light;
In an image display device comprising a projection lens that projects the reflected light of the rotating mirror onto a projection surface,
The diameter of the beam waist of the light beam emitted from the projection lens, when the beam waist diameter of the laser beam having a wavelength lambda _n was w _n,
w ₁ ...> w _n ...> w _N
An image display device characterized by that. The beam diameter ψ _n of the parallel light having the wavelength λ _n incident on the condenser lens,
ψ ₁ ...> ψ _n ...> ψ _N
The image display apparatus according to claim 6, further comprising a limiting unit. The beam diameter ψ _n of the parallel light having the wavelength λ _n incident on the condenser lens is:
includes a limiting portion, the to _{ψ 1 ···> ψ n ···>} ψ N,
A beam waist is formed for the luminous flux B _n emitted from the projection lens, and a beam diameter w _n at the beam waist is w ₁ ...> W _n ...> W _N. The image display device according to claim 5 or 6. The beam diameter w _n at the beam waist of the projection light,
The image display device according to claim 1, wherein λ ₁ / w ₁ ... ≈λ _n / w _n ... ≈λ _N / w _N.   The image display device according to claim 4, wherein the restriction unit is formed by a dichroic filter including a plurality of regions.   The image display device according to claim 4, wherein the limiting portion is formed by a diffraction grating composed of a plurality of regions.

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