JP2013228725A - Illumination device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve the field curvature of light illuminating an illumination area.SOLUTION: An illumination device includes: a bar laser in which a plurality of emitters are arrayed; a lens array comprising a plurality of lens units arrayed in a first direction in which the emitters are arrayed; a first lens which projects a far-field image of a laser beam emitted from the bar laser, on the lens array; a second lens which projects far-field images of the laser beam divided by the lens array, over an illumination area; and a pair of lenses which form near-field images in a second direction orthogonal to the first direction, of the emitted laser beam, on the illumination area. The pair of lenses includes a third lens, and the number of the plurality of lens units is set on the basis of a prescribed relation between a maximum angle which light resultant from incidence on the third lens and emission from the third lens of the emitted laser beam forms with an optical axis on a plane including the second direction and the optical axis, and the field curvature of light projected over the illumination area.

Description

  The present invention relates to an illumination device for illuminating a linear illumination area with a laser beam emitted from a bar laser.

  For example, when an image is recorded by irradiating a recording medium such as a thermal material with a laser beam, it is necessary to use a high-power laser light source. In such a case, a bar laser (broad area semiconductor laser) is used in which a plurality of emitters (light emitting points) are formed in a straight line, and a large number of laser beams whose chief rays are substantially parallel are emitted from these emitters. The

  In Patent Document 1, such a bar laser and a spatial light modulator are used, and a laser beam emitted from the bar laser is converted into a microlens composed of a plurality of microlenses arranged in an array direction of individual emitters in the bar laser. An illuminating device that illuminates a spatial light modulator in an overlapping manner through an array is disclosed. In the illumination device, a laser beam with a uniform light amount can be illuminated on the illumination area.

JP 2002-72132 A

  However, in the illumination device of Patent Document 1, even when the amount of light to be illuminated is made uniform, the field curvature of the light illuminated on the illumination area becomes large, which may cause uneven exposure on the recording medium. There's a problem.

  The present invention has been made to solve these problems, and in an illuminating device for illuminating a linear illumination area with a laser beam emitted from a bar laser, the field curvature of light illuminated in the illumination area is improved. The purpose is to provide technology that can be used.

  An illumination device according to a first aspect is an illumination device that illuminates a line-shaped illumination area with a laser beam emitted from a bar laser, and a bar laser in which a plurality of emitters that emit laser beams are arranged in a straight line, The plurality of lens units arranged in a direction parallel to the first direction in which the emitters are arranged, and a laser beam incident parallel to the plurality of lens units is at least on the final surface of the plurality of lens units A lens array configured to converge in a plane including the first direction and the optical axis, and a first far-field image in the first direction of the laser beam emitted from the bar laser is projected onto the lens array. A lens, a second lens that projects a far-field image of the laser beam divided by the lens array so as to be superimposed on the illumination area, and the bar A pair of lenses that form a near-field image in a second direction orthogonal to the first direction in the laser beam emitted from the laser on the illumination area, and the pair of lenses is a laser emitted from the bar laser A third lens that suppresses divergence of the beam in the second direction by parallelization, and the number of the plurality of lens units is caused by divergence of the laser beam emitted from the bar laser in the first direction. Since the laser beam is incident on the third lens and the light emitted from the third lens is not completely collimated, the light emitted from the third lens is changed in the second direction and the optical axis. And a far-field image of the divided laser beam projected by being superimposed on the illumination area by the second lens. It is set based on a predetermined relationship with a predetermined curvature.

  The illumination device according to a second aspect is the illumination device according to the first aspect, wherein the maximum angle is a divergence angle in the first direction of the laser beam emitted from the bar laser, and the third lens. If at least one of the height of the light emitted from the optical axis in the second direction increases, the maximum angle also increases, the focal length of the third lens, and the number of the plurality of lens units If at least one of these increases, the maximum angle is specified based on a predetermined relationship.

  The illumination device according to the third aspect is the illumination device according to the first or second aspect, wherein the number of the plurality of lens units is 25 or more.

  According to the present invention, the laser beam emitted from the bar laser is incident on the third lens, and the light emitted from the third lens is in the second direction perpendicular to the first direction, which is the emitter arrangement direction, and the optical axis. The number of lens units is set based on a predetermined relationship between a maximum angle formed by the optical axis in a plane including the predetermined curvature of field. The maximum angle has a relationship of decreasing as the number of the plurality of lens units increases. Therefore, according to the present invention, by setting the number of lens units that can suppress the field curvature to a desired level or less, the field curvature of the light illuminated in the illumination area can be improved. Further, the SAC lens, which has been conventionally required for making the illuminance distribution of the laser beam incident on the lens array uniform, becomes unnecessary.

It is the top view which looked at the illuminating device which concerns on embodiment of this invention from the slow axis direction. It is the side view which looked at the illuminating device of FIG. 1 from the fast axis direction. It is a figure which illustrates a bow tie aberration. It is a figure which illustrates the field curvature generate | occur | produced by bowtie aberration. It is a figure which illustrates the field curvature generate | occur | produced by bowtie aberration. FIG. 3 is an enlarged view of the vicinity of a fac lens (third lens) in FIG. 2. It is a figure which shows the relationship between the division | segmentation number of a lens array, and the largest curvature of field with a graph. It is a figure which shows the luminance distribution of the laser beam superimposed in the spatial light modulator by a graph. It is a figure which shows the luminance distribution of the laser beam superimposed in the spatial light modulator by a graph. It is a figure which shows the luminance distribution of the laser beam superimposed in the spatial light modulator by a graph. It is a figure which shows the luminance distribution of the laser beam superimposed in the spatial light modulator by a graph. It is a figure which shows the luminance distribution of the laser beam superimposed in the spatial light modulator by a graph. It is a figure which shows the luminance distribution of the laser beam superimposed in the spatial light modulator by a graph. It is a figure which shows the luminance distribution of the laser beam superimposed in the spatial light modulator by a graph. It is a figure which shows the luminance distribution of the laser beam superimposed in the spatial light modulator by a graph.

  Hereinafter, an embodiment of the present invention will be described with reference to the drawings. In the drawings, parts having the same configuration and function are denoted by the same reference numerals, and redundant description is omitted in the following description. Each drawing is schematically shown. For example, the size and positional relationship of display objects in each drawing are not necessarily shown accurately. In the drawings, an XYZ orthogonal coordinate system is described as appropriate for explanation of directions. The Z axis is a direction parallel to the optical axis, the X axis is parallel to a slow axis direction described later, and the Y axis is parallel to a fast axis direction described later.

<Embodiment>
<1. Configuration of lighting device>
FIG. 1 is a plan view of an illuminating device according to an embodiment of the present invention viewed from the fast axis direction, and FIG. 2 is a side view of the illuminating device shown in FIG. 1 viewed from the slow axis direction.

  The fast axis direction refers to a direction in which a laser beam emitted from each emitter (light emitting point) 11 in the bar laser 12 described later spreads quickly, and the slow axis direction refers to a laser emitted from each emitter 11 in the bar laser 12. The direction in which the beam spreads slowly. In FIG. 1, the direction perpendicular to the paper surface (Y-axis direction) is the fast axis direction, the vertical direction (X-axis direction) is the slow axis direction, and the left-right direction (Z-axis direction) is the optical axis direction. Similarly, in FIG. 2, the direction perpendicular to the paper surface (X-axis direction) is the slow axis direction, the vertical direction (Y-axis direction) is the fast axis direction, and the left-right direction (Z-axis direction) is the optical axis direction. It is.

  This illumination device is for irradiating a laser beam emitted from the bar laser 12 onto a linear illumination area on the surface of the spatial light modulator 13, and includes a lens array 15 having power in the slow axis direction, and a slow axis direction. A pair of cylindrical lenses 16 and 17 having power in a pair, and a pair of cylindrical lenses 18 and 19 having power in the fast axis direction. This illuminating device is used, for example, in an image recording device for recording an image on a thermal material.

  The bar laser 12 is a kind of semiconductor laser, and has a configuration in which a plurality of emitters 11 emitting a laser beam are arranged in a straight line. As such a bar laser 12, for example, B1-83-40C-19-30-A or B1-830-60C-49-50-B manufactured by COHERENT can be used. In FIG. 1, for convenience of explanation, only five emitters 11 are shown, but in reality, about several tens of emitters 11 are arranged in a row.

  Each laser beam emitted from each emitter 11 diverges at a divergence angle α (FIG. 2) in the fast axis direction, and diverges at a divergence angle β (FIG. 1) in the slow axis direction. The divergence angle α is larger than the divergence angle β.

  The lens array 15 (also simply referred to as “lens array”) has a configuration in which two lens arrays 14 are combined. This lens array 15 is composed of a plurality of lens units arranged in a direction parallel to the arrangement direction of the emitters 11 in the bar laser 12, and a laser beam incident in parallel to the plurality of lens units is arranged on the final surface of the emitter 11. It is comprised so that it may converge in the surface containing an arrangement direction and an optical axis. In this embodiment, the lens array 15 (that is, each lens array 14) is configured by five lens units of lens units 1 to 5.

  The cylindrical lens 16 (“first lens”) having power in the slow axis direction is also referred to as the arrangement direction (slow axis direction, “first direction”) of the emitters 11 of the laser beam emitted from each emitter 11 in the bar laser 12. The far field image (Far Field Pattern) is superimposed on the lens array 15 and projected onto the lens array 15. The cylindrical laser 16 has a front focal position of the bar laser 12 and a rear focal position of the lens array 15. The first surface of is arranged.

  The cylindrical lens 17 (“second lens”) having power in the slow axis direction converts the far-field image of each laser beam divided by the lens array 15 into a linear illumination area on the surface of the spatial light modulator 13. The final surface of the lens array 15 is disposed at the front focal position of the cylindrical lens 17 and the surface of the spatial light modulator 13 is disposed at the rear focal position.

  The pair of cylindrical lenses 18 and 19 having power in the fast axis direction is a direction (fast axis direction, “second direction”) orthogonal to the arrangement direction of the emitters 11 of the laser beams emitted from the emitters 11 in the bar laser 12. A near-field image (referred to as “Near Field Pattern”) is formed on a linear illumination area on the surface of the spatial light modulator 13.

  The cylindrical lens 18 (“third lens”) is also referred to as a fast axis collimator (FAC) lens. The cylindrical lens 18 is a lens that suppresses the divergence of the laser beam emitted from each emitter 11 of the bar laser 12 in the fast axis direction (second direction) by parallelization.

  The spatial light modulator 13 divides the laser beam applied to the line-shaped illumination area on the surface thereof into a plurality of laser beams, and modulates each of the plurality of laser beams independently. is there. The laser beam modulated by the spatial light modulator 13 is irradiated onto the recording medium via an imaging optical system (not shown). As such a spatial light modulator 13, for example, GLV (registered trademark) (Grating Light Valve) manufactured by Silicon Light Machines, Inc. of the United States can be used.

  In the illumination device configured as described above, the laser beam emitted from each emitter 11 in the bar laser 12 is incident on the lens array 15 in a state of being substantially parallel light by the action of the cylindrical lenses 16 and 18. Then, each laser beam is divided by the lens array 15 and then irradiated with being superimposed on a linear illumination area on the surface of the spatial light modulator 13.

<2. Bowtie aberration>
FIG. 3 shows a bow tie on the surface 102 (FIGS. 1 and 2) of laser light that is emitted from a plurality of emitters 11 and is deflected by the cylindrical lens 18 and the cylindrical lens 16 and projected onto the lens array 15. It is a figure which illustrates an aberration. FIG. 3 shows a cross-sectional shape of the laser beam on the surface 102 when the surface 102 is viewed in the + Z direction. The surface 102 is a plane located at a position moved in the −Z direction from the lens array 15, and is a plane parallel to the XY plane (a plane formed by fast axis and slow axis). As shown in FIG. 3, the cross-sectional shape of the laser light irradiated onto the surface 102 is wide at the central portion (portion in the vicinity of the optical axis in the slow axis direction) and at the end portion (portion far from the optical axis in the slow axis direction). Has a narrow bow tie aberration. This aberration is caused by the fact that the laser light applied to the central portion has not yet converged on the surface 102 in the optical axis direction near the lens array 15, whereas the laser light applied to the end portion is In the surface 102, it has shown that it has converged rather than the laser beam irradiated to the center part. Since the laser beam emitted from the emitter 11 diverges at a divergence angle β in the slow axis direction, the cylindrical lens 18 has an apparent radius of curvature in the slow axis direction. Due to the apparent radius of curvature, the laser light emitted from the cylindrical lens 18 diverges in the fast axis direction in response to the divergence of the laser light incident on the cylindrical lens 18 in the slow axis direction. As a result, bow tie aberration is generated. As shown in FIG. 3, the bow tie aberration at the surface 102 is large at the center and small at the end, but the bow tie aberration at the first surface of the lens array 15 is conversely small at the center and large at the end. Become.

  In FIG. 2, the broken line is a plane (YZ plane) including the optical axis and the fast axis direction of the laser light emitted from the emitter 11 and diverging in the slow axis direction at the maximum divergence angle β and entering the cylindrical lens 18. The optical path in is shown. 2 indicates the optical path in the YZ plane of the laser light that is emitted from the emitter 11 and travels along the optical axis without divergence and enters the cylindrical lens 18. The laser light traveling along the optical axis forms an image on the surface (image plane) of the spatial light modulator 13, whereas the laser light diverging in the slow axis direction with a divergence angle β is spatial light modulation. The image is formed on the front side (−Z side) of the laser beam in the traveling direction from the surface (image plane) of the vessel 13. This difference in image formation position causes field curvature described later.

<3. Field curvature>
FIG. 4 illustrates field curvatures 31 to 35 in the surface portion of the spatial light modulator 13 generated by bow-tie aberration when the lens array 15 is configured by five lens units 1 to 5. It is a figure to do. Field curvatures 31 to 35 indicate field curvatures of the respective laser beams respectively emitted from the lens units 1 to 5. In FIG. 4, the direction in which the convergence position increases (upward on the paper surface) is the −Z direction opposite to the traveling direction of the laser direction.

  The laser light incident on the first surface of the lens array 15 is divided and incident on the lens units 1 to 5, exits from the final surfaces of the lens units 1 to 5, passes through the cylindrical lenses 17 and 19, and is spatial light. The surface of the modulator 13 is irradiated with being superimposed on each other. Among the field curvatures 31 to 35, the field curvature 33 of the laser light emitted from the lens unit 1 is the smallest, and the laser light emitted from the lens units 1 and 5 at both ends of the lens units 1 to 5 respectively. The corresponding field curvatures 31 and 35 are the maximum field curvature b1.

  The laser light incident on the lens array 15 is divided into five lens sizes of the lens units 1 to 5 in the slow axis direction by the lens units 1 to 5. By this division, the field curvature of the laser light emitted from the lens array 15 and illuminated on the surface of the spatial light modulator 13 is also divided into five. Each divided field curvature is reduced as compared with the case where the division is not performed. Specifically, the maximum field curvature b1 occurs about 2 mm. However, for example, in a CTP (computer to plate) exposure system, in order to have sufficient focus latitude, it is necessary to set the field curvature to 100 μm or less. Therefore, when the cylindrical lens array is composed of five lens units, the number of lens units is not sufficient.

<4. Improvement of curvature of field>
FIG. 5 is a diagram illustrating the field curvature at the surface portion of the spatial light modulator 13 generated by the bow-tie aberration when the number of lens units constituting the lens array 15 is increased to 11, similar to FIG. is there. In the example of FIG. 5, the field curvature of the laser beam emitted from the lens units at both ends of the plurality of lens units constituting the lens array 15 is the maximum field curvature b2, but the field curvature b2 This is smaller than the field curvature b1 in FIG.

  If the k lens units constituting the lens array 15 are inserted into the optical path together with the cylindrical lens 17 (condenser lens) in the same manner as in the examples of FIGS. 1 and 2, the laser light incident on the lens array 15 is in the slow axis direction. Is divided into k and incident on individual lens units. Therefore, the divergence angle in the slow axis direction incident on the lens unit is β / k. The bow tie aberration generated on the first surface of the lens array 15 is also divided into k in the slow axis direction. Accordingly, if the number of lens units constituting the lens array 15 is increased, the bow tie aberration per individual lens unit for the laser light incident on the first surface of the lens array 15 is reduced, and the spatial light modulator 13. It is possible to reduce and improve the damage surface curvature in the surface portion of the film.

  FIG. 6 is an enlarged view of the vicinity of the cylindrical lens 18 (third lens) of FIG. The difference between the solid line and the broken line shown in FIG. 2 is exaggerated in FIG. The angle Δε shown in FIG. 6 is the light emitted from the fac lens after being emitted from the emitter 11, diverging in the slow axis direction at a divergence angle β and entering the cylindrical lens 18 (third lens). The maximum angle formed with the optical axis in a plane including the direction (second direction) and the optical axis is shown. The direction of the coordinate axes in FIG. 6 is the same as the direction of the coordinate axes in FIG.

As shown in FIG. 1 and FIG. 2, each laser beam emitted from each emitter 11 of the bar laser 12 diverges in the fast axis direction and the slow axis direction at divergence angles α and β, respectively. In this case, the height h ₁ ′ of the laser light incident on the cylindrical lens 18 (third lens) becomes h1 / cos β due to the divergence of the laser light incident on the cylindrical lens 18 toward the slow axis direction. As a result, the apparent focal length f ₁ ′ of the cylindrical lens 18 having a focal length of f1 is expressed by equation (1). Here, n is the refractive index of the cylindrical lens 18.

As a result, light emitted from each emitter 11 diverges in the slow axis direction at a divergence angle β, enters the cylindrical lens 18 (third lens), and then the light emitted from the cylindrical lens 18 (third lens) is fast axis. The maximum angle Δε formed with the optical axis in a plane including the direction (second direction) and the optical axis is expressed by equation (2). The maximum angle Δε is caused by the divergence of the laser beam emitted from the bar laser 12 in the slow axis direction (first direction), and the laser beam is incident on the cylindrical lens 18 (third lens). This is an angle generated when the light emitted from the lens 18 (third lens) is not completely collimated. Equation (2) is expressed by the divergence angle β of the laser beam emitted from the bar laser 12 in the slow axis direction and the height h of the laser beam emitted from the cylindrical lens 18 (third lens) from the optical axis in the fast axis direction. If at least one of ₁ increases, the maximum angle Δε also increases, and at least one of the focal length f ₁ of the cylindrical lens 18 (third lens) and the number k of the plurality of lens units increases. For example, a predetermined relationship in which the maximum angle Δε decreases is shown.

Further, the field curvature Δs due to the bow tie aberration is expressed by equation (3). However, the focal length f ₂ is the focal length of the cylindrical lens 19 that is a condensing lens in the fast axis direction, the image height h ₂ is the image height of the collimated light incident on the cylindrical lens 19, and the image height Δh ₂ is divergent. The image height is changed by the angle β.

From equations (2) and (3), it can be seen that the amount of field curvature of the surface portion of the spatial light modulator 13 due to bow-tie aberration depends on the focal length f ₂ , the image height h ₂ , and the divergence angle β. It can also be seen that the field curvature does not depend on the focal length of the cylindrical lens 16. On the other hand, the focal length f ₂ and the image height h ₂ are restricted by the numerical aperture in design. Therefore, in reality, reducing the angle Δε is a solution for reducing the field curvature Δs. The solution for reducing the maximum angle Δε is the angle Δε and the far-field image of each divided laser beam projected onto the illumination area in the spatial light modulator 13 by the cylindrical lens 17 (second lens). This is a method of setting the number of a plurality of lens units constituting the lens array 15 based on a predetermined relationship with the predetermined curvature of field.

FIG. 7 shows the number of divisions of the lens array 15, that is, the number of lens units constituting the lens array 15, and the respective laser beams emitted from the respective lens units and superimposed on the surface portion of the spatial light modulator 13. It is a figure which shows the relationship with the largest curvature of field in a graph. Note that the focal length f ₁ for this graph is 0.909 mm and the focal length f ₂ is 21.9 mm. Further, the heights h ₁ , h ₁ ′, h ₂ , and h ₂ ′ are each obtained by the equation (4). A high power type bar laser usually has a divergence angle β of 5 degrees or less. In this case, as shown in the graph of FIG. 7, it is necessary to use the lens array 15 divided into 25 or more in order to obtain the desired field curvature of 100 μm or less.

  8 to 15 show the width direction (fast axis direction) of the line-shaped laser beam emitted from each lens unit of the lens array 15 of the illumination device and superimposed on the surface of the spatial light modulator 13. It is a figure which shows luminance distribution with a graph. The luminance distribution shown in each graph is obtained by simulating the luminance distribution in the width direction of the center portion and the end portion in the longitudinal direction (slow axis direction) of the superimposed line-shaped laser beam. The luminance distribution at the center is indicated by a solid line, and the luminance distribution at the end is indicated by a one-dot chain line.

  More specifically, the focal lengths of the cylindrical lenses 16, 17, and 19 are set to 60 mm, 150 mm, and 74 mm, respectively, in each of the lighting devices corresponding to the graphs of FIGS. Further, the number of divisions of the lens array 15 of each lighting device corresponding to each graph of FIGS. 8 to 11, that is, the number of lens units constituting the lens array 15 is set to 5, 20, 25, and 40, respectively. Has been.

  In any of the lighting devices corresponding to the graphs of FIGS. 12 to 15, the focal lengths of the cylindrical lenses 16, 17, and 19 are set to 120 mm, 150 mm, and 60 mm, respectively. Moreover, the division | segmentation number of the lens array 15 of each illuminating device corresponding to each graph of FIGS. 12-15 is set to 5, 20, 25, 40, respectively.

  In any of the simulations corresponding to the graphs of FIGS. 8 to 15, lenses other than the cylindrical lens 18 that generates bow-tie aberration among the lenses included in the illumination device are treated as ideal lenses. .

  The line-shaped laser beam irradiated with being superimposed on the surface of the spatial light modulator 13 is irradiated from the surface toward the recording medium, and the width direction of the laser beam relative to the recording medium on the recording medium. Scanned. For this reason, it is preferable that the brightness | luminance (light quantity) of the laser beam in the longitudinal direction of a line-shaped laser beam is uniform. That is, it is preferable that the luminance distribution (light quantity distribution) in the width direction of the laser beam in each part in the longitudinal direction of the laser beam is substantially equal to each other.

  As shown in FIGS. 8 and 12, when the number of divisions of the lens array 15 is 5, the width direction of the laser beam at each of the center portion and the end portion in the longitudinal direction of the superimposed line-shaped laser beam. The luminance distributions of are significantly different from each other. Specifically, the luminance sum in the width direction of the laser beam is larger at the center than at the end. The shape of the luminance distribution is also wider at the center than at the end. That is, the laser beam is brighter at the center in the longitudinal direction and wider than the end. In addition, although illustration is abbreviate | omitted about the luminance distribution in the part other than the said center part and the said edge part, beam width is narrower compared with a center part, so that it is a part away from the center part of a laser beam, Simulation results have been obtained with lower brightness.

  On the other hand, as shown in FIGS. 9 to 11 and 13 to 15, the brightness in the width direction of the laser beam at each of the center portion and the end portion in the longitudinal direction of the superimposed line-shaped laser beam. The distribution (distribution width, distribution shape, and luminance sum in the width direction) becomes closer to each other as the number of lens units constituting the lens array 15 increases. That is, the width of the laser beam at each of the central portion and the end portion and the luminance sum in the width direction are closer to each other as the number of divisions of the lens array 15 is increased. Note that although the illustration of the luminance distribution in the width direction of the laser beam in the portion excluding the central portion and the end portion is omitted, the luminance distribution also increases as the number of divisions of the lens array 15 increases. A simulation result closer to the luminance distribution in the width direction of the laser beam in the part is obtained.

  More specifically, when the number of divisions of the lens array 15 is 20, the luminance distribution in the width direction of the laser beam at each of the center portion and the end portion in the longitudinal direction of the laser beam is when the division number is 5. Although they are extremely close to each other, the difference between them is slightly larger than when the number of divisions of the lens array 15 is 25 or more.

  When the number of divisions of the lens array 15 is 25 or more, the luminance distributions in the width direction of the center portion and the end portion in the longitudinal direction of the laser beam are substantially equal to each other. That is, the luminance distribution in the longitudinal direction of the laser beam is substantially uniform. Here, as shown in FIG. 7, if the number of lens units constituting the lens array 15 is 25 or more, each laser beam is divided by each lens unit and irradiated to the spatial light modulator 13. The maximum field curvature is 100 μm or less. Therefore, if the lens array 15 is divided into 25 or more lens units so that the maximum field curvature of each laser beam divided and irradiated on the surface of the spatial light modulator 13 is 100 μm or less. The brightness distribution in the width direction of the laser beam at each part in the longitudinal direction of the line-shaped laser beam superimposed on the surface of the spatial light modulator 13 becomes a preferable brightness distribution, and thereby the brightness in the longitudinal direction of the laser beam. It can be seen that the distribution is a preferable substantially uniform luminance distribution.

  In addition, when the luminance distribution in the longitudinal direction of the superimposed line-shaped laser beam varies greatly as in the case where the number of divisions of the lens array 15 shown in FIGS. 8 and 12 is 5, For example, it is necessary to correct the curvature of field of each laser beam divided by the lens array 15 by adopting a toric lens as the cylindrical lens 19. For this reason, the manufacturing cost of an illuminating device rises. However, if the number of lens units constituting the lens array 15 is set to 25 or more, the curvature of field of each laser beam divided and irradiated on the surface of the spatial light modulator 13 can be suppressed to 100 μm or less. There is no need to use a toric lens. Thereby, the manufacturing cost of an illuminating device can be suppressed.

  According to the illuminating device according to the present embodiment configured as described above, the laser beam emitted from the bar laser 12 is incident on the cylindrical lens 18 (third lens), and the laser light emitted from the cylindrical lens 18 is Based on a predetermined relationship between a maximum angle Δε made with the optical axis in a plane including a fast axis direction (second direction) orthogonal to the arrangement direction of the emitters 11 and the optical axis, and a predetermined curvature of field, The number of lens units constituting the lens array 15 is set. Further, the maximum angle Δε decreases as the number of the plurality of lens units increases. Therefore, according to the illuminating device according to the present embodiment, the number of lens units capable of suppressing the curvature of field at the surface portion of the spatial light modulator 13 to a desired level or less is set, so that the spatial light modulator 13 is set. The field curvature of the light illuminated in the illumination area can be improved.

  In general, the light amount distribution emitted from the bar laser is not uniform, but since the light incident on the lens array is divided by each lens unit, the light amount distribution of the laser light projected on the image plane from one lens unit is Converted to an angular spectrum. According to the illuminating device according to the present embodiment, the number of the plurality of lens units constituting the lens array 15 is set to an appropriate number based on a predetermined relationship between the maximum angle Δε and a predetermined curvature of field. Therefore, the difference in the light amount distribution of the laser light taken into one lens unit becomes very small, and the uniformity of the angle spectrum in the slow axis direction on the surface (image plane) of the spatial light modulator 13 is improved.

  Although the invention has been shown and described in detail, the above description is illustrative in all aspects and not restrictive. Therefore, embodiments of the present invention can be modified or omitted as appropriate within the scope of the invention.

1 to 5 Lens unit 11 Emitter 12 Bar laser 13 Spatial light modulator 14, 15 Lens array 16 Cylindrical lens (first lens)
17 Cylindrical lens (second lens)
18 Cylindrical lens (third lens)
19 Cylindrical lens

Claims (3)

An illumination device that illuminates a linear illumination area with a laser beam emitted from a bar laser,
A bar laser in which a plurality of emitters emitting laser beams are arranged in a straight line;
The plurality of lens units arranged in a direction parallel to the first direction in which the emitters are arranged, and a laser beam incident parallel to the plurality of lens units is at least on the final surface of the plurality of lens units A lens array configured to converge in a plane including the first direction and the optical axis;
A first lens that projects a far-field image of the laser beam emitted from the bar laser in the first direction onto the lens array;
A second lens that projects a far-field image of the laser beam divided by the lens array so as to be superimposed on the illumination area;
A pair of lenses that image a near-field image in a second direction orthogonal to the first direction in the laser beam emitted from the bar laser in the illumination area;
With
The pair of lenses is
A third lens that suppresses divergence of the laser beam emitted from the bar laser in the second direction by parallelization;
The number of the plurality of lens units is
Due to the divergence of the laser beam emitted from the bar laser in the first direction, the laser beam is incident on the third lens and the light emitted from the third lens is not completely collimated. Thus, the maximum angle that the light emitted from the third lens forms with the optical axis in a plane including the second direction and the optical axis,
A predetermined curvature of field about a far-field image of the divided laser beam projected on the illumination area by the second lens;
The lighting device set based on the predetermined relationship. The lighting device according to claim 1,
The maximum angle is
If at least one of the divergence angle in the first direction of the laser beam emitted from the bar laser and the height from the optical axis in the second direction of the light emitted from the third lens increases, the maximum And the angle specified by the predetermined relationship in which the maximum angle decreases if at least one of the focal length of the third lens and the number of the plurality of lens units increases. apparatus. The lighting device according to claim 2,
The illumination device in which the number of the plurality of lens units is 25 or more.

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