JP2006072220A - Illuminating device and image generation device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain illuminating light of high uniformity in an illuminating device using a plurality of laser light sources, and an image generation device. <P>SOLUTION: An illuminating device 1A includes collimator lenses 3a provided for a plurality of laser light sources 2a respectively and optical systems 3b disposed in succeeding stages of respective collimator lenses and superposes near field images of respective laser light sources to illuminate a linear radiation object (a linear optical modulator or the like) 4. they are configured so as to satisfy ¾Δθ¾<(w/fc) wherein; fc is the focal length of each collimator lens 3a; w is the width of a near field image relating to each laser light source 2a; and Δθ is a relative angular displacement of adjacent emitted light beams of an emitted luminous flux transmitted through collimator lenses from respective laser light sources. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a technique for overcoming an adverse effect caused by unevenness of illumination light in application to an illumination device using a laser light source and an image generation device (projector, printer, etc.) using the illumination device.

  An optical system for realizing illumination with a uniform light intensity distribution using a plurality of laser light sources or a plurality of laser beams is known. For example, in application to a projection-type image display device or the like, a primary beam obtained by irradiating a linear beam to a one-dimensional spatial modulation type light modulation element and modulating light using the light modulation element A two-dimensional image can be formed by projecting the original image on a screen while scanning the original image along a direction orthogonal to the one-dimensional direction by an optical scanning unit such as a galvanometer. An example of the one-dimensional spatial modulation type light modulation element is a grating light valve (hereinafter referred to as “GLV”) developed by Silicon Light Machine (SLM). This GLV element is composed of a reflective diffraction grating, and a plurality of movable ribbons are arranged at predetermined intervals, and a fixed ribbon is arranged between adjacent movable ribbons. Then, by applying a drive voltage between the common electrode and the movable ribbon, the movable ribbon moves, and a diffraction grating for incident light is configured.

  In such illumination of the one-dimensional light modulation element, the light intensity needs to be substantially constant within a predetermined range (a so-called “top hat” shape distribution), for example, using a laser array light source and a fly-eye lens. In order to improve the uniformity of intensity distribution even when the number of divisions of the fly-eye lens is a divisor of the number of laser arrays when performing uniform illumination, the laser array light incident on each lens array A design method is known in which the spatial phases of the profiles are different from each other (see, for example, Patent Document 1).

  Also, in an illumination device using a parallel light source, a lens array, and an imaging lens, the light intensity is obtained by using the eccentricity of each element constituting the lens array to superimpose the parallel light source images while being spatially shifted. An example of the configuration is one in which the distribution is made uniform (see, for example, Patent Document 2).

Japanese Patent Laid-Open No. 2003-218017 JP 2003-121777 A

  By the way, in the conventional illumination optical system, the near-field image (near field pattern) of the laser light source is enlarged and superimposed on the irradiated part (one-dimensional light modulation element). The irradiated portion is irradiated with the averaged intensity distribution.

  In the optical design, it is assumed that the characteristics of each laser light source and the individual emitters of the laser array are in an ideal state, that is, there is no individual difference or characteristic variation, and an ideal Gaussian beam is output. There are various characteristics of actual lasers, and sufficient consideration must be given to the existence of individual differences.

  For example, when one-dimensional illumination light obtained by superimposing a plurality of laser beams is applied to the light modulation element, the characteristics of the individual lasers are reflected as they are in the intensity distribution. In order to obtain the characteristics, it is necessary to realize the “top hat shape” intensity distribution for the near-field image of the laser (generally, it has a mountain-like intensity distribution shape like a Gaussian distribution). There is.

  When a uniform intensity distribution of one-dimensional illumination light required in application to a laser projection system or the like cannot be obtained, the light use efficiency becomes low and the influence on image quality becomes a problem.

  Accordingly, an object of the present invention is to obtain highly uniform illumination light in an illumination device and an image generation device using a plurality of laser light sources.

  In order to solve the above-described problems, the present invention includes a collimator lens provided for each of a plurality of laser light sources, and an optical system disposed at the subsequent stage of each collimator lens, and a near-field image of each laser light source. Is used to illuminate a linear irradiation target (such as a one-dimensional light modulation element). The focal length of the collimator lens is denoted as “fc”, and the width of the near-field image associated with each laser light source is denoted as “w” (for example, defined as a width equal to or greater than the threshold when a predetermined intensity threshold is used as a reference) When the relative angular displacement of the adjacent light beams among the light beams emitted toward the optical system is denoted as “Δθ”, the output light flux that has passed through the collimator lens from each laser light source is expressed as Δθ The absolute value | Δθ | is configured to satisfy “| Δθ | <(w / fc)”.

  Therefore, in the present invention, it is possible to impose a condition on the angular displacement Δθ relating to the emitted light beam after collimation and to uniformize the light intensity distribution on the irradiated portion (that is, “| Δθ | ≧ (w / In “fc)”, the ratio of spatially overlapping portions is reduced, and it is difficult to ensure sufficient uniformity.)

  According to the present invention, the uniformity of illumination light can be improved, which is effective for mitigating optical effects and guaranteeing performance.

  When “Δθ = α · (w / fc)”, the α value is preferably in the range of “α ≦ 0.25”. The reason is that when the value of α is larger than 0.25, the ratio of the spatial overlap portion decreases, and the decrease in uniformity becomes noticeable due to the output variation of each laser light source and the influence of output fluctuation. Depends.

  By changing the postures of the laser light source and the collimator lens, the configuration in which the adjacent light beams are inclined at the angle of Δθ is simple, and an optical element for angle adjustment and setting is unnecessary.

  In addition, a reflection member for reflecting the laser light emitted from the laser light source and transmitted through the collimator lens is provided, and in the form in which the posture of each reflection member is relatively inclined by an angle of Δθ / 2, The degree of freedom in arrangement is high, and it is sufficient to set the angle of the reflecting member, and adjustment is easy.

  In the configuration in which the laser light source is shifted by the amount of displacement of “fc · Δθ” with respect to the collimator lens in the direction perpendicular to the optical axis, the beam incident position on the collimator lens can be individually set for each laser light source. It has a simple configuration and is effective in reducing loss.

  And a plurality of laser light sources, an optical system including a collimator lens and a Fourier transform lens, and a one-dimensional light modulation element used for modulating light from the optical system, and expanding a near-field image of each laser light source. In application to an image generation device that illuminates a one-dimensional light modulation element by superimposing and generates an image by light modulation, the light intensity distribution is made uniform to achieve higher performance and improved image quality. Is possible.

  It is an object of the present invention to obtain highly uniform illumination light using a plurality of laser light sources, and to increase the luminous flux utilization rate in application to a laser projector apparatus or the like. In the present invention, for example, a two-dimensional image is formed by scanning a one-dimensional image formed by a one-dimensional spatial modulation type light modulation element with an optical scanning means such as a galvanometer, and this is projected and displayed. The present invention can be applied to a front projection type or rear projection type image display device, or an image output device such as a printer.

  FIG. 1 shows a basic configuration of an illumination device 1 according to the present invention, which includes a light source unit 2 and an optical system 3.

  The light source unit 2 is configured using a plurality of laser light sources 2a, 2a,. Examples of the laser light source 2a include a form using a parallel light source such as a semiconductor laser array in which a plurality of emitters (radiation sources) are arranged in a fixed direction, and a form using a plurality of individual laser light sources. Since the type and arrangement of the laser light source are not limited to a specific form in the application of the present invention, the degree of freedom in design is high.

  After the laser beam from the light source unit 2 is sent to the optical system 3, illumination light with high uniformity can be obtained on the image plane (see “S” in the figure). This imaging plane corresponds to, for example, the irradiated surface of the one-dimensional light modulation element, and is within a predetermined range in the one-dimensional direction (major axis direction of the element) as shown by a one-dot chain line “G” in FIG. Illumination with a uniform intensity distribution is performed throughout.

  The optical system 3 may be a single lens or a lens group. For example, in a configuration including a collimator lens (or a collimator lens) provided for each laser light source 2a and an imaging lens disposed at the subsequent stage of each collimator lens, the near-field image of each laser light source 2a is enlarged. Then, after spatially superimposing, the linear irradiation target (irradiated part) is illuminated.

  FIG. 2 shows an example of the embodiment of the present invention.

  In the illuminating device 1A shown in this example, the light source unit 2 includes a plurality (three in the figure) of laser emitters (laser light sources 2a), and each emitter has a near-field image (see “NFP” in the figure). ) Have substantially equal widths (this is referred to as “w”).

The luminous flux of each emitter is collimated by a collimator lens (whose focal length is denoted as “fc”) 3a, and further, a Fourier transform lens (whose focal length is denoted as “f _FT ”) 3b. A near-field image of each emitter is re-imaged with a width (denoted as “D”) in an irradiated portion 4 arranged on the focal point, for example, a one-dimensional spatial modulator. Here, the relationship “D = w · (f _FT / fc)” is established.

  Three collimation units 5U, 5C, and 5D each including an emitter and a collimator lens are disposed. Each unit is mounted on a support member (not shown) and the posture of each unit can be changed by a known adjustment mechanism. it can.

  In this example, the laser light emitted from the collimation unit 5C located at the center in the vertical direction of the figure propagates in a direction parallel to the optical axis of the Fourier transform lens 3b. On the other hand, with respect to the collimation units 5U and 5D positioned above and below the figure, the angular displacements of “−Δθ” and “+ Δθ” are respectively positive with respect to the central collimation unit 5C. And tilted. That is, with respect to each outgoing light beam, the propagation direction of the outgoing light beam forms an angle of Δθ with respect to the propagation direction of the outgoing light beam from the central collimation unit 5C. In this example, the light emitted from the collimation units 5U and 5D propagates in a direction away from the light emitted from the collimation unit 5C and enters the Fourier transform lens 3b.

As a result, as shown in FIG. 3, on the one-dimensional spatial modulator, the light beams from the collimation units 5U and 5D are shifted by “+ Δx” and “−Δx” respectively from the light beams from the collimation unit 5C. An image is formed (see the curve indicated by the broken line in the figure). Note that “Δx = Δθ · f _FT ”.

  When the parameter “α” is introduced and expressed as “Δθ = α · (w / fc)”, the following equation is obtained.

Δx = Δθ · f _FT = α · (w / fc) · f _FT = α · D

  For example, when “α = 0.25” is selected and the angular displacement Δθ is selected to be “Δθ = 0.25 · (w / fc)”, “Δx = 0.25 · D”. That is, the light beams from each collimation unit are imaged in a state where they are shifted in the length direction (major axis direction) of the one-dimensional spatial light modulator by a value of a quarter of each width D.

  In this manner, on the one-dimensional spatial modulator, the near-field images are formed in a shifted relationship with each other, and a combined light intensity distribution obtained by superimposing the respective distributions is obtained. As shown in FIG. 3, the distribution shape has increased uniformity in the length direction of the one-dimensional spatial modulator, thereby increasing the light utilization efficiency.

Further, if the width in the length direction of the one-dimensional spatial modulator related to the combined light intensity distribution is “D _ttl ”, this width is a value close to “2 · Δx + D” (= (2 · α + 1) · D). However, when the length of the one-dimensional spatial modulator (effective length in the long axis direction) is “L”, the range of “L ≦ D _ttl ≦ 1.2 · L” is preferable. In other words, when the D _ttl value is less than L, the pixel array in the one-dimensional spatial modulator cannot be illuminated over a sufficient irradiation range, and the D _ttl value is “1.2 · If it is larger than “L”, the ratio of the substantial irradiation range is reduced, so that the light use efficiency is lowered.

In the above description, the case where the number of light sources is three is shown, but a similar configuration can be realized by generalizing when the number of light sources is n (in this case, D _ttl is “( n−1) · Δx + D ”.

  Since the application of the present invention is not limited to “α = 0.25”, when “0 <α <1,” the absolute displacement Δθ of each outgoing ray with respect to the optical axis of the Fourier transform lens 3b is used. The value | Δθ | satisfies “0 ≦ | Δθ | <(w / fc)”.

  The practical α value is preferably in the range of “α ≦ 0.25”. That is, when the α value exceeds the upper limit “0.25”, there is a demerit that the uniformity of the light intensity distribution is significantly reduced due to the output variation and output fluctuation of each laser light source. .

  In the above description, the collimation unit (including the laser light source and the collimator lens) is rotated so that the light emitted from the unit is tilted (the posture of the unit is changed with respect to the reference axis). In other words, in the application of the present invention, various forms shown below are included.

(I) A configuration in which the postures of adjacent collimation units are relatively inclined by an angle of Δθ. (II) A reflection member for reflecting the laser light transmitted through the collimator lens is provided, and the postures of the reflection members are mutually Δθ. (III) Configuration in which the laser light source is shifted by a displacement of “fc · Δθ” with respect to the collimator lens in a direction perpendicular to the optical axis. (IV) Above (I) to (III) Configuration form combining two or more

  FIG. 4 illustrates the illuminating device 1B according to the embodiment (II), and is provided with reflecting members (6U, 6C, 6D) for reflecting the laser light transmitted through each collimator lens. That is, the light emitted from each collimation unit is reflected by each reflecting member, and the angle of each reflecting member is set to be different by Δθ / 2.

  In this example, the laser beam emitted from the collimation unit 5C located in the center in the vertical direction in the figure is reflected by the reflecting member 6C, thereby undergoing an optical path change at an angle of 90 °, and the optical axis of the Fourier transform lens 3b. Propagates in a direction parallel to On the other hand, with respect to the collimation units 5U and 5D positioned above and below in the drawing, the emitted light is reflected by the reflecting members 6U and 6D, respectively, but the posture of the reflecting member 6U is “−Δθ / The angle of the reflection member 6D is inclined by an angle of “+ Δθ / 2” with respect to the reference direction. That is, the light beams reflected by the respective reflecting members form angles of “−Δθ” and “+ Δθ”, respectively, with respect to the propagation direction of the reflected light by the reflecting member 6C. In this example, the light whose optical path has been changed by the reflecting members 6U and 6D propagates in the direction away from the light whose optical path has been changed by the reflecting member 6C, and enters the Fourier transform lens 3b.

  FIG. 5 illustrates the illuminating device 1C according to the embodiment (III), and the emission from the collimation unit is performed by shifting the relative position of the emitter center with respect to the collimator lens in the collimation unit by “fc · Δθ”. The light beam is tilted with respect to the reference optical axis. For each emitter, a laser diode can be used as a discrete form. Alternatively, a configuration in which the optical axis of the collimator lens is displaced relative to the outgoing optical axis of the emitters arranged at a predetermined interval is also possible.

  In this example, the laser light emitted from the collimation unit 5C located at the center in the vertical direction of the figure propagates in a direction parallel to the optical axis of the Fourier transform lens 3b. That is, the center of the emitter is set on the optical axis of the collimator lens 3a constituting the collimation unit 5C. On the other hand, for the collimation units 5U and 5D positioned in the upper and lower directions in the figure, the center of the emitter is set at a position shifted from the optical axis of the collimator lens 3a constituting each unit. With respect to the optical axis of the collimator lens 3a of the collimation unit 5U, the positional displacement of the emitter in the direction orthogonal to the optical axis is set to “−fc · Δθ” (displacement downward in the figure), and the collimation unit 5D The positional displacement of the emitter in the direction orthogonal to the optical axis of the collimator lens 3a is set to “+ fc · Δθ” (displacement upward in the figure). As a result, the outgoing rays of the collimation units 5U and 5D form angles of “−Δθ” and “+ Δθ”, respectively, with respect to the propagation direction of the outgoing rays of the collimation unit 5C. In this example, the emitted light of each of the collimation units 5U and 5D propagates in a direction away from the emitted light of the collimation unit 5C and enters the Fourier transform lens 3b.

  In the above form (IV), it is possible to design in various aspects by combining the above (I) to (III). However, it is easy to adjust and set Δθ rather than making the structure complicated. In addition, a configuration that is hardly affected by aging, temperature change, and the like is preferable.

  6 and 7 show a configuration example of the image generation apparatus according to the present invention. When the optical axis of the illumination optical system is taken as the x-axis, and the two axes orthogonal thereto are the y-axis and z-axis, respectively, FIG. 6 shows the configuration in the xz plane, and FIG. An in-plane configuration is shown.

  The image generation apparatus 7 shown in this example is applied to an image display apparatus such as a projection apparatus, and includes a light source unit 8, an illumination optical system 9, a one-dimensional light modulation element 10, a projection optical system 11, and an optical scanning system 12. I have.

  The light source unit 8 is configured using a plurality of laser light sources 2a, 2a,... Such as LD (laser diode) emitters, and collimator lenses 3a, 3a,.

  The illumination optical system 9 has an imaging optical system including a Fourier transform lens 3b and a condensing lens 3c arranged at the subsequent stage of each collimator lens 3a. The Fourier transform lens 3b has a positive power in the xz plane, but has no power in the xy plane. The condensing lens 3c has positive power in the xy plane, but does not have power in the xz plane. The present invention is not limited to this example, and a form in which a beam expander optical system or the like is further provided in the illumination optical system and enlarged illumination is performed at a predetermined lateral magnification on the irradiated surface of the one-dimensional light modulation element.

  The light that has passed through the illumination optical system 9 is applied to the one-dimensional light modulation element 10, and the laser light is modulated using the element. Although the figure shows a transmissive configuration for the one-dimensional light modulation element, a reflective configuration is also possible. For example, in an application example using a GLV element, in the case of a reflective diffraction grating, a plurality of movable ribbons and fixed ribbons are alternately arranged along a predetermined direction. When six ribbon elements constituting one pixel are provided and every three movable ribbons and every other fixed ribbon are arranged, 6480 ribbons for 1080 pixels for one line. Elements are arranged along a one-dimensional direction (major axis direction). On the irradiation surface of the laser beam from the illumination optical system 9, the first surface that is the surface of the movable ribbon and the second surface that is the surface of the fixed ribbon are alternately arranged, and the movable ribbon is received by receiving a drive signal. The position of the first surface is controlled in the direction along the irradiation direction of the laser beam. That is, when a driving voltage corresponding to an image signal is applied, the movable ribbon moves with a displacement corresponding to the driving voltage value, and in this state (so-called pixel on), a reflective diffraction grating for incident light is configured (primary Generation of diffracted light). Further, in a state where the displacement amount is made uniform with the fixed ribbon without moving the movable ribbon (so-called pixel off), the first-order diffracted light is not generated (only regular reflection with respect to the incident light).

  The light modulated using the one-dimensional light modulation element 10 reaches the optical scanning system 12 via the projection optical system 11. In addition to the projection lens, the projection optical system 11 includes, for example, a spatial filter (Schlieren filter), a diffuser, and the like for selecting a diffracted light component of a specific order.

  For example, a galvanometer or the like is used as the optical scanning system 12 and receives a one-dimensional image of incident light to form a two-dimensional image. That is, when the formation direction of the one-dimensional image is the “first direction”, the direction corresponds to the major axis direction of the one-dimensional light modulation element, and the “second direction” is orthogonal to the first direction. A two-dimensional image is formed by performing optical scanning along the “direction of”. Note that the scanning method includes a unidirectional scanning method and a bidirectional scanning method. In the former method, for example, the left edge of the display screen is set as the scanning start position, the right edge is set as the scanning end position, and the vertical line extending in the first direction from the left edge is started. After scanning along the second direction, when the right edge is reached, the light returns to the left edge again and the optical scanning is repeated. In the latter method, the left edge and the right edge of the display screen are set as the scanning start position and the scanning end position. For example, optical scanning is started from the left edge, and the vertical line extending in the first direction is the first line. After scanning along the two directions, when the right edge is reached, light scanning is performed in the opposite direction, and when the original left edge is reached, the light scanning is started again from the left edge.

  In the projector device, an image is displayed by projecting a two-dimensional image obtained by optical scanning onto a screen (not shown). In this example, a configuration in which a one-dimensional image is optically scanned through the projection optical system 11 is shown. However, the present invention is not limited thereto, and a two-dimensional intermediate image is formed by optical scanning of a one-dimensional image. A configuration in which an image is projected through a projection optical system may be adopted.

  In the image generation device 7, the near-field images of the respective laser light sources are enlarged and superimposed to illuminate the one-dimensional light modulation element 10, and an image is generated by light modulation using the one-dimensional light modulation element. Although possible, in the optical system including the laser light source 2a, the collimator lens 3a, and the Fourier transform lens 3b, by applying the above-described forms (I) to (IV), the major axis direction of the one-dimensional light modulation element 11 ( A light intensity distribution shape with high uniformity is obtained along the pixel array direction (that is, corresponding to the z direction in FIG. 6), and as a result, the light utilization efficiency increases.

  According to the configuration described above, a highly uniform illumination light can be obtained using a plurality of laser light sources, and an image is generated by modulating light from an irradiation optical system using a light modulation element. This is effective for improving the image quality.

It is explanatory drawing which shows the basic composition of the illuminating device which concerns on this invention. It is explanatory drawing which shows an example about embodiment of this invention. It is a figure for demonstrating light intensity distribution on a to-be-irradiated part. It is explanatory drawing which shows another structural example which concerns on this invention. It is explanatory drawing which shows another structural example which concerns on this invention. It is a figure which shows the structural example of the image generation apparatus which concerns on this invention with FIG. It is a figure which shows the structure at the time of seeing from the direction different from FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1, 1A, 1B, 1C ... Illuminating device, 2 ... Light source part, 2a ... Laser light source, 3 ... Optical system, 3a ... Collimator lens, 3b ... Fourier transform lens, 6U, 6C, 6D ... Reflective member, 7 ... Image generation Apparatus, 8 ... light source unit, 10 ... one-dimensional light modulation element

Claims (10)

Equipped with a plurality of laser light sources, a collimator lens provided for each laser light source, and an optical system arranged at the subsequent stage of the collimator lens, and enlarges the near-field image of each laser light source to form a linear shape In the lighting device that illuminates the irradiation target,
The focal length of the collimator lens is denoted as “fc”, the width of the near-field image associated with each laser light source is denoted as “w”, and the emitted light beams transmitted from the laser light sources through the collimator lens are adjacent to each other. The absolute value | Δθ | of Δθ satisfies “| Δθ | <(w / fc)” when the relative angular displacement of is expressed as “Δθ”. The lighting device according to claim 1,
The above-mentioned Δθ is “Δθ = α · (w / fc)” (where α ≦ 0.25). The lighting device according to claim 1,
The illuminating device, wherein the laser light sources adjacent to each other and the postures of the collimator lenses corresponding to the laser light sources are relatively inclined by the angle Δθ. The lighting device according to claim 1,
A reflecting member for reflecting the laser light emitted from the laser light source and transmitted through the collimator lens corresponding to the laser light source is provided, and the posture of each reflecting member is relatively inclined by an angle of Δθ / 2. A lighting device characterized by the above. The lighting device according to claim 1,
The illuminating apparatus characterized in that the laser light sources are shifted from each other by a displacement amount of “fc · Δθ” along a direction perpendicular to the optical axis with respect to the collimator lens. An optical system including a plurality of laser light sources, a collimator lens provided for each of the laser light sources, and a Fourier transform lens disposed at the subsequent stage of the collimator lens, and one-dimensional light used for modulation of light from the optical system An image generating apparatus comprising: a modulation element; illuminating the one-dimensional light modulation element by magnifying and superimposing a near-field image of each laser light source; and generating an image by light modulation using the one-dimensional light modulation element In
The focal length of the collimator lens is denoted as “fc”, the width of the near-field image associated with each laser light source is denoted as “w”, and the emitted light beams transmitted from the laser light sources through the collimator lens are adjacent to each other. An absolute value | Δθ | of Δθ satisfies “| Δθ | <(w / fc)” when the relative angular displacement of is expressed as “Δθ”. The image generation apparatus according to claim 6,
The image generation apparatus, wherein Δθ is “Δθ = α · (w / fc)” (where α ≦ 0.25). The image generation apparatus according to claim 6,
An image generating apparatus, wherein the laser light sources adjacent to each other and the postures of the collimator lenses corresponding to the laser light sources are relatively inclined by the angle Δθ. The image generation apparatus according to claim 6,
A reflecting member for reflecting the laser light emitted from the laser light source and transmitted through the collimator lens corresponding to the laser light source is provided, and the posture of each reflecting member is relatively inclined by an angle of Δθ / 2. An image generation apparatus characterized by the above. The image generation apparatus according to claim 1,
An image generating apparatus, wherein the laser light source is shifted by a displacement amount of “fc · Δθ” from each other along a direction orthogonal to the optical axis with respect to the collimator lens.

Images