JP4670876B2 - Illumination optical system and image display device - Google Patents

Description

  The present invention relates to an illumination optical system and an image display apparatus using a laser array light source.

  In recent years, many examples using lasers as light sources of optical image display devices have been reported. In general, light emitted from a laser has high directivity, so that the light use efficiency is expected to be improved. Further, the monochromaticity can realize a wide color reproduction region required in an image display device. Therefore, it is considered useful as a light source for illumination.

  However, since laser light has high coherence, a problem arises in that a spotted pattern caused by light interference called speckle noise occurs on the irradiated surface. This is because the phase of each light beam that passes through different points in the element plane is shifted according to the amount of unevenness due to the minute unevenness present on the element in the illumination optical system, light valve, projection optical system, or screen. The light beams that are coherent with each other form interference fringes on the irradiated surface. Since the surface accuracy of these elements is finite, the influence of speckle noise is always a problem when a light source with high coherence is used.

  With regard to such speckle noise, an illumination device that reduces speckle noise by arranging a plurality of light emitting points made of laser emitters in an array and superimposing light beams from the respective light emitting points via different optical distances. Has been proposed (see, for example, Patent Document 1).

  On the other hand, since the spatial light intensity distribution of the light emitted from the laser has a Gaussian shape or a substantially Gaussian shape, the light intensity at the center of the light beam is the highest, and the light intensity decreases exponentially as the distance from the center increases. Since the light emitted from each light emitting point has the same spatial intensity distribution, it is not improved only by superimposing the light fluxes out of phase. Therefore, when the light from the illumination device as described above is used as illumination light, the light intensity at the image display surface edge position is very low with respect to the light intensity at the image display surface center position, and the illuminance distribution on the image display surface Is not preferable in an image display device that is required to be uniform.

  Therefore, a fly-eye lens having a microlens corresponding to each light emitting point of the laser array light source is disposed close to the laser array light source, and the parallel light beams emitted from each light emitting point are split from the light emitting points. An illuminating device having a fly-eye inclinator optical system that converts a spatial light intensity distribution into a rectangular shape by superimposing them has been proposed (for example, see Patent Document 2).

JP 2004-206004 A (paragraphs 0014 to 0016, FIG. 2) Japanese Patent Laying-Open No. 2003-131165 (paragraphs 0036 and 0041, FIG. 4)

  However, in general, in an arrayed semiconductor laser light source, the interval between the light emitting points is very small, about several hundred μm, and a fine fly-eye lens having a microlens corresponding to each light emitting point is manufactured at low cost and with high accuracy. It is difficult to do. Also in the illumination device of Patent Document 1, it is necessary to provide a collimating lens cell corresponding to each light emitting point at the emission end of the laser array light source in order to allow the light beams from each light emitting point to pass through transparent plates having different optical distances. Therefore, it has been difficult to manufacture at low cost and with high accuracy.

  The present invention has been made to solve the above-described problems, and can be easily manufactured, and illumination optics that can emit illumination light suitable for image display by improving speckle noise and spatial light intensity distribution. It is an object to obtain a system and a projection display apparatus.

The illumination optical system according to the present invention includes: a laser array light source in which a plurality of light emitting points are arranged in an array; and a surface defined by an optical axis and an array direction of the laser array light source as an array surface. An array direction collimating optical element that emits light incident from a light source as parallel light within the array plane, and a direction defined by the array vertical direction is defined as a direction perpendicular to the array plane, and a plane defined by the array vertical direction Then, an array vertical collimating optical element that emits light incident from the laser array light source as parallel light within the array vertical plane, and light incident through the array direction collimating optical element and the array vertical collimating optical element Is divided into a plurality of light beams in a matrix in a plane perpendicular to the optical axis, and the divided plurality of light beams An integrator optical element that irradiates to overlap on the irradiation surface, the array direction collimating optical element from the laser array light source so that the divergent light emitted from the plurality of light emitting points is overlapped and incident The array vertical collimating optical element is disposed at a predetermined interval, and the array vertical collimating optical element converts the incident light into parallel light in the array vertical plane and emits the light, and light incident from the laser array light source An array vertical direction beam shaping optical element that irradiates the divided light beams so as to be superimposed on the array vertical direction collimating lens, and the array vertical direction beam shaping optical element comprises: A plurality of cylindrical lenses are arranged in parallel on an arc centering on the light emitting point in the vertical plane of the array. It is characterized in that a one-dimensional multi-stage lens.

  An image display apparatus according to the present invention includes the above-described illumination optical system, a light modulation element that forms an image by controlling illumination light incident from the illumination optical system, and enlarges image light from the light modulation element. A projection optical system for projecting; and an image display unit for displaying the enlarged and projected image light.

  According to the present invention, the array direction collimating optical element is configured to be arranged at a predetermined interval from the laser array light source. Therefore, each of the array direction collimating optical elements is applied to the array direction collimating optical element using the divergence of the light emitted from the light emitting point. Light from the light emitting point is overlapped and incident, and can be emitted as a beam with a beam diameter wider than the beam diameter of the entire laser array light source, making it easy to manufacture integrator optical systems and improving speckle noise and spatial light intensity distribution Thus, an illumination optical system that can emit illumination light suitable for image display and a projection display apparatus can be obtained.

Embodiment. 1
FIG. 1 conceptually shows the overall configuration of the illumination optical system 1 according to the first embodiment, and FIG. 2 conceptually shows the configuration of a one-dimensional array semiconductor laser 2 portion that is a laser array light source in the illumination optical system 1. Hereinafter, the x-axis direction shown in FIG. 1 is the array direction, the z-direction is the optical axis C direction, and based on the xyz-axis, the surface composed of the axis in the array direction and the optical axis C is the xz plane (array surface). A plane composed of an axis perpendicular to the plane (y axis) and the optical axis C is called a yz plane (array vertical plane).

  In the figure, an illumination optical system 1 includes a one-dimensional array semiconductor laser 2 and a one-dimensional array semiconductor which are laser array light sources in which a plurality of light emitting points 3 that are laser emitters that emit light having a divergence are arranged in an array. If the plane defined by the optical axis C of the laser 2 and the array direction is the array plane (xz plane in the figure), the collimator in the array direction emits the light incident from the one-dimensional array semiconductor laser 2 as parallel light in the array plane. Assuming that the collimating lens 4 as an optical element and the direction perpendicular to the array surface (y direction) are the array vertical direction and the surface defined by the array vertical direction and the optical axis C is the array vertical surface, a one-dimensional array semiconductor laser Array collimating optical element 5 that emits light incident from 2 as parallel light in the array vertical plane, collimating lens 4 and array vertical The light incident through the directional collimating optical element 5 is longitudinally and laterally (in a direction perpendicular to the array direction in the xy plane (hereinafter referred to as array vertical direction) and array direction) in a plane perpendicular to the optical axis C (xy plane). And an integrator optical element 6 for irradiating the divided plurality of light beams so as to overlap each other on the irradiated surface of the light valve 7, and the collimating lens 4 includes a plurality of light emitting points 3. The divergent lights emitted from the laser beams are overlapped and incident, and are wider than the beam diameter B of the whole light source of the one-dimensional array semiconductor laser 2 in the array direction, that is, the combined beam from each light emitting point 3 at the emission end 2a. A one-dimensional array semiconductor laser 2 is arranged at a predetermined interval Lx so as to be emitted as a beam having a beam diameter.

  Further, the array vertical collimating optical element 5 divides the light incident from the one-dimensional array semiconductor laser 2 in the array vertical direction and the array vertical collimating lens 5b for converting the light beam in the divergence direction into parallel light in the array vertical plane. And an array vertical direction beam shaping optical element 5a for irradiating the divided light beams so as to be superimposed on the array vertical direction collimating lens 5b.

  The light emitted from the illumination optical system 1 illuminates a light valve 7 such as a liquid crystal panel or DMD (digital micromirror device) as a modulation element that spatially modulates the illuminated light and gives an image signal. . A projection optical system (not shown) for enlarging and projecting the light emitted from the light valve 7 on the image display unit, and an image display unit (not shown) such as a screen on which the light from the projection optical system is projected Further, an image display device (not shown) such as an image projection device is configured. Details are shown below.

  A one-dimensional array semiconductor laser 2 which is a laser array light source has a plurality of (20 (only 10 are simply shown in FIG. 2)) light emitting points 3 arranged in a straight line at an interval d of 200 μm. The coherent light emitted from the divergence has a divergence, and the half-value half angle α of the divergence angle on the yz plane is 30 degrees, and the half-value half angle β of the divergence angle on the xz plane is 10 degrees. The beam diameter of each light emitting point 3 is 0.01 mm (a in FIG. 2) in the array vertical direction and 0.04 mm (b in FIG. 2) in the array direction, and the beam diameter B at the emission end 2a of the laser array light source 2 as a whole. Is 3.84 mm (about 4 mm). In addition, laser light emitted from each light emitting point 3 in the one-dimensional array semiconductor laser 2 is light having very high coherence when viewed individually, but a plurality of light emitting points 3 in the one-dimensional array semiconductor laser 2 are respectively Since the laser beams emitted from the respective light emitting points 3 are generated from different resonators, the phases are not aligned and are incoherent with each other.

  The collimating lens 4 that is an array direction collimating optical element is a collimating lens that collimates the light beam from the one-dimensional array semiconductor laser 2 in the array direction. The size is 50 mm in the array direction × 40 mm in the vertical direction of the array, and the optical distance Lx is arranged at an interval of 100 mm in the optical axis C direction from the emission end 2 a of the one-dimensional array semiconductor laser 2. As a result, the beam diameter defined by the half-value half angle β from each light emitting point 3 incident on the collimating lens 4 in the array direction is the beam diameter at the emission end 2a of the one-dimensional array semiconductor laser 2 due to the divergence of the laser beam. 36 mm, which is approximately 900 times b (0.04 mm). This beam diameter is larger than the distance from one end of the light emitting point 3 to the other end, and light is emitted in the same direction from each light emitting point 3, so that almost all light emitting points are formed in the incident surface of the collimating lens 4. The beams from 3 will overlap. Further, the diameter of light incident on the collimating lens 4 is 40 mm (36 mm + 4 mm), which is 10 times the beam diameter B (about 4 mm) of the entire emission end 2a of the one-dimensional array semiconductor laser 2, that is, the entire laser array light source. . Note that the width of the collimating lens 4 in the array direction is 50 mm, and actually, light rays outside the half-value half angle β from each light emitting point 3 (range from the optical axis to about 13 degrees) are also used. The collimating lens 4 superimposes light from each light emitting point 3 and emits parallel light having a width of 50 mm in the array direction.

  The array vertical direction collimating optical element 5 makes the laser light emitted from each light emitting point 3 parallel to the optical axis C in the array vertical direction and makes the light intensity distribution in the array vertical direction uniform. . As shown in FIG. 3, a one-dimensional multistage lens 5a in which three plano-concave cylindrical lenses 5aa, 5ab, and 5ac that are array vertical direction beam shaping optical elements are arranged in parallel, and a plano-convex cylindrical lens 5b that is an array vertical direction collimating lens. Consists of. In the figure, the one-dimensional multi-stage lens 5a has three plano-concave cylindrical lenses 5aa, 5ab, 5ac having a curvature in the array vertical direction in the array vertical plane at a position spaced by an optical distance Ly of 20 mm from the emission end 2a. Specifically, they are arranged in parallel so as to draw an arc centered on the light emitting point 3. Beam in the vertical direction of the array (In the description of the vertical direction of the array, the light beams from the light emitting points 3 overlap each other and can be regarded as one beam. )) Is incident in a state where it is expanded to 23 mm in the range of half-value half-angle α due to the diffusibility of the beam. In the first embodiment, the opening height (array vertical direction) of the incident surfaces of the plano-concave cylindrical lenses 5aa, 5ab, and 5ac is 9 mm, and the expanded beam is perpendicular to the array including the region outside the half-value half angle α. Divided into three in the direction. Each of the three divided light beams is further enlarged so as to be superimposed on the incident surface of the plano-convex cylindrical lens 5b having an array direction of 50 mm and an array vertical direction of 40 mm, and the width is parallel to the optical axis C by the plano-convex cylindrical lens 5b. A light beam of about 40 mm is emitted toward the fly-eye integrator 6 (in the vertical direction of the array).

  The integrator optical system 6 is a fly in which lens cells are arranged in a matrix (50 array directions, 40 array vertical directions) on a 50 mm (array direction) × 40 mm (array vertical direction) substrate with an arrangement period of 1.0 mm. The fly eye integrator 6 includes a pair of eye lenses (6a, 6b) and a spherical lens 6c that is rotationally symmetric with respect to the optical axis C.

Next, the operation will be described.
In the array direction, the light emitted from the 20 light emitting points 3 of the one-dimensional array semiconductor laser 2 travels straight in the direction parallel to the optical axis C. Then, while traveling through the optical distance Lx (100 mm), the beam diameter widens due to the divergence, and light in the range of an effective angle of 13 degrees centering on the optical axis C is overlapped on the entire incident surface of the collimating lens 4. Incident at. At this stage, the beams from the 20 light emitting points 3 are superimposed, and the speckle noise is reduced to ¼ or less (details will be described later). Further, the light emitted from the light emitting point 3 has a high intensity of light at the center, and the intensity of the light decreases toward the periphery. However, in the present embodiment, the beams from the light emitting points 3 are overlapped while shifting the center position of the beam little by little (by 0.2 mm according to the arrangement interval d) according to the arrangement position, and the spatial light intensity Distribution is also improved. That is, by collimating the light from each light emitting point 3 arranged in an array at a position at an optical distance Lx from the emission end 2a, in addition to the effect of reducing speckle noise by superimposing incoherent light, the light intensity The effect of improving the spatial light intensity distribution in the array direction can also be obtained by shifting and superimposing the center position of the strong beam.

  Further, since the beam from each light emitting point 3 is expanded and superposed without using an optical member such as a lens by utilizing the property that laser light diverges, the beam from each light emitting point 3 is Make equal spreads. Accordingly, the beam tilt and spread do not change for each light emitting point 3, so that collimation can be easily performed. Furthermore, since the beam from each light emitting point 3 is expanded without using an optical member such as a lens, damage due to heat generation can be suppressed even when a high-power laser is used.

  On the other hand, also in the vertical direction of the array, each light emitted from each light emitting point 3 of the one-dimensional array semiconductor laser 2 goes straight in a direction parallel to the optical axis C. The beam diameter is widened by the divergence while traveling the optical distance Ly (20 mm), and three luminous fluxes are obtained every 9 mm in the vertical direction of the array by the plano-concave cylindrical lenses 5aa, 5ab, and 5ac of the one-dimensional multistage lens 5a. Divided and superimposed on the incident surface (50 mm × 40 mm) of the plano-convex cylindrical lens 5b in the subsequent stage, becomes a light beam parallel to the optical axis C and having a width (in the vertical direction of the array) of about 40 mm toward the fly eye integrator 6. Emitted.

  At this time, even when the beam emitted from the light emitting point 3 is in the vertical direction of the array, the intensity of light at the center is strong, and the intensity of light becomes weaker toward the periphery. However, in the present embodiment, the spatial light intensity distribution is made uniform by dividing the light beam spreading from one light emitting point (described as being considered) into a plurality of light beams in the array vertical direction and superimposing the divided light beams. The In other words, the array vertical direction collimating optical element 5 not only has a collimating function in the array vertical direction for emitting light incident from the laser array light source as parallel light in the array vertical plane, but also the spatial light intensity distribution in the array vertical direction. It also has a beam shaping function. In particular, since the plano-concave cylindrical lenses 5aa, 5ab, and 5ac are arranged in parallel so as to draw an arc centered on the light emitting point 3 so that the apertures thereof face the center of the light emitting point 3, the direction of the divergent beam The divergence angle can be accurately converted and can be easily collimated by the plano-convex cylindrical lens 5b.

  Further, in the first embodiment, by utilizing the fact that the half-value half angle α in the array vertical direction is larger than the half-value half angle β in the array direction, an optical distance that is 1/5 of the optical distance Lx between the collimating lens 4 and the emission end 2a. Even if the one-dimensional multistage lens 5a is arranged in Ly, the beam diameter in the array vertical plane can be sufficiently expanded. Therefore, each of the plano-concave cylindrical lenses 5aa, 5ab, and 5ac can be set to a size that can be easily manufactured with a pitch of 10 mm. Then, the collimating lens 4 and the array vertical direction collimating optical element 5 can be installed with a spatial likelihood, and positioning for dividing the beam in an appropriate direction in the array vertical direction is also easily performed. be able to.

  In this manner, the light emitted from each light emitting point 3 of the one-dimensional array semiconductor laser 2 is expanded to a width of 40 mm in the array vertical direction by the array vertical direction collimating optical element 5, and is parallel to the optical axis C and spatial light intensity. The light is incident on the fly-eye integrator 6 which is an integrator optical system as a beam having a substantially uniform distribution, that is, a shaped beam.

Note that the beam diameter in the x direction emitted from the collimating lens 4 described above is a value calculated according to Equation 1 from the half value half angle β and the optical distance Lx. In the case of the beam defined by this equation, the edge portion of the beam diameter However, it has a light intensity that is ½ of the light intensity at the center, and can be used as illumination light even at a portion outside the beam diameter.
Beam diameter = 2 × Lx × Tan (β) + b (1)

  Therefore, in the present embodiment, a light flux in the range of 13 degrees centering on the optical axis C in the array direction from the light emitting point 3 and 34 degrees centering on the optical axis C in the array vertical direction is used as illumination light. The parallel light was 50 mm in the array direction and 40 mm in the array vertical direction.

  Even when the half-value half-angle α in the vertical direction of the array is small and the beam is emitted as substantially parallel light in the vertical direction of the array, an optical lens system for expanding the beam is provided in front of the one-dimensional multi-stage lens 5a. As described above, the array vertical collimating optical element 5 can be arranged. Even when an optical lens system for expanding the beam is not installed, the one-dimensional multistage lens 15a having a fine plano-concave cylindrical lens as shown in FIG. 4 is used to divide the beam in an appropriate direction in the array vertical direction. If it can be accurately positioned, the array vertical collimating optical element 15 can be formed by combining with the plano-convex cylindrical lens 15b.

  The light that has passed through the array direction collimating optical element 4 and the array vertical direction collimating optical element 5 becomes a parallel light beam of 50 mm in the array direction and 40 mm in the array vertical direction as shown in FIG. Is incident on. The incident light is divided into a total of 2000 light beams in a two-dimensional direction by the microlenses of the fly-eye lens 6a arranged in a matrix form in the array direction 50 × 40 array vertical directions and in the xy plane. Each of the divided light beams enters the lens cell of the corresponding fly-eye lens 6b, and the light beam that has entered each lens cell of the fly-eye lens 6b passes through the spherical lens 6c, so that the irradiated surface of the light valve 7 is irradiated. Is superimposed on the entire surface. That is, the fly eye integrator 6 spatially divides the incident parallel light and superimposes the divided light beams, thereby uniformly converting the spatial light intensity distribution until it becomes a rectangular shape and irradiating the light valve 7.

  That is, the integrator optical system divides the light beam parallel to the optical axis C two-dimensionally (spatially) in a plane perpendicular to the optical axis C, and superimposes the divided light beams. The spatial light intensity distribution in the array direction and the array vertical direction, that is, in the cross section perpendicular to the optical axis C, is converted into a rectangular shape and irradiated to the light valve 7.

  Here, laser light and speckle noise will be described. Since the laser light emitted from the one-dimensional array semiconductor laser 2 has a narrow wavelength band and is excellent in monochromaticity and has high directivity, application to an image display device is very preferable. However, on the other hand, light emitted from a single light emitting point has very high coherence, and there is a concern about speckle problems when used in an image display device.

Two light fluxes having a relationship of phase difference Δφa (r) expressed by a function of the position r as shown by the equations (2) and (3) at the spatial position r of the irradiated surface, which is irradiated with light, A ₁ , A ₂ has a coherent relationship, the intensity I _co (r) of the combined light of the two light beams on the irradiated surface can be expressed as an equation related to the spatial coordinates of the irradiated surface as shown in Equation (4). Is done. On the other hand, _assuming that the two light beams have an incoherent relationship, the light intensity I _{inco on the} irradiated surface of the combined light is expressed by the following equation (5).
A ₁ (r, t) = u · exp (iφa (r, t)) (2)
A ₂ (r, t) = u · exp [i (φa (r, t) + Δφa (r))] (3)
I _co (r) ∝ | A ₁ + A ₂ | ² = 2u ² + 2u ² cos Δφa (r) (4)
I _inco (r) ∝ | A ₁ | ² + | A ₂ | ² = 2u ² (5)

FIG. 5 shows a graph of these equations (4) and (5). As is clear from FIG. 5, the light intensity I _inco when two light beams having an incoherent relationship are superimposed is _constant regardless of the spatial position, that is, regardless of the amount of phase shift caused by the unevenness of the element. On the other hand, the light intensity I _co in the case where two light beams having a coherent relationship are superimposed shows light and dark due to the difference in phase shift amount at different spatial positions. The bright and dark stripes resulting from the coherence of the light source are called speckles.

In the present invention, since the laser light emitted from each light emitting point 3 in the one-dimensional array semiconductor laser 2 which is an array laser light source is generated from an independent resonator, it is utilized that they are incoherent with each other. In addition, the speckle contrast is lowered by spatially superposing these laser beams and the influence of speckle noise is suppressed. This is because when a plurality of incoherent lights are superimposed on each other, the total light intensity is simply the sum of the light intensities of each light. Even if there is a non-uniform spatial light intensity distribution, the entire spatial light intensity distribution is averaged and uniformed when a plurality of lights having incoherent and random spatial light intensity distributions are spatially superimposed on each other. By becoming. As is clear from statistics, the standard deviation of the mean value of the random distribution is inversely proportional to the square root of the number of samples, so that when coherent light emitted from n light emitting points in an incoherent relationship is superimposed, The speckle contrast is proportional to the reciprocal of the square root of the number of light sources to be superimposed on the speckle contrast generated by the coherent light emitted from one light emitting point as shown in Equation (6). As the number increases, the speckle contrast decreases.
Speckle contrast = 1 / (n) ^1/2 ... (6)

  In the present invention, in order to obtain the effect of uniforming the spatial light intensity distribution by superimposing the random distribution as described above, a predetermined optical distance Lx is opened with respect to the one-dimensional array semiconductor laser 2 having a divergence angle in the array plane. By providing the collimating lens 4 installed in this manner, the beam from each light emitting point 3 is naturally expanded so that a plurality of lights having an incoherent relationship with each other can be superimposed. In the first embodiment, the beams from the 20 light emitting points 3 of the one-dimensional array semiconductor laser 2 are overlapped, so that the speckle contrast is reduced to ¼ or less according to the equation (6).

  Furthermore, after the light superimposed in this way is divided into a plurality of light beams by the fly eye integrator 6, the irradiated surface of the light valve 7 is illuminated for each light beam. As shown in FIG. 1, each light beam divided by the fly-eye lens 6a is irradiated onto the light valve 7 via different optical distances. That is, even when the emission end 2a is regarded as a single light emitting point, the beam diameter of the laser light emitted from the light emitting point is enlarged so that the lens cell in the fly eye integrator 6 can be used to the maximum extent. Become. The light beams that have passed through different lens cells propagate through different optical distances to the irradiated portion of the light valve 7 and have an optical path difference that is greater than or equal to the coherence distance, so that the light becomes light with low coherence. In particular, by providing the collimating lens 4 installed with a predetermined optical distance Lx, the size of the plane perpendicular to the optical axis C of the fly-eye integrator 6 is the size of the entire emission end 2 a of the one-dimensional array semiconductor laser 2. The optical path difference for each lens cell becomes larger.

  Therefore, even if the light incident on the fly eye integrator 6 has a single phase, the light beams from the lens cells superimposed on the light valve 7 by the fly eye integrator 6 irradiate the light valve 7 with different phases. Will be. That is, on the irradiated surface of the light valve 7, a plurality of incoherent 2000 lights overlap each other, and the speckle contrast is further reduced to 1/40 or less according to the equation (6). Therefore, as in the first embodiment of the present invention, the configuration in which the diameter of the light emitted from each light emitting point 3 is enlarged and then incident on the fly eye integrator 6 is effective for speckle reduction.

  As described above, it is effective to superimpose the light flux to reduce speckles. In the first embodiment, the collimating lens 4 is disposed away from the one-dimensional array semiconductor laser 2 so that the integrator optical element is provided. The light from all the light emitting points 3 is superposed before entering. However, in order to exhibit the speckle reduction effect in the integrator optical element, the interval Lx may be set so that at least the light from the adjacent light emitting points 3 is incident on the collimating lens 4. In this case, since incident light does not break in the array direction on the incident surface of the integrator optical element 6, speckle noise can be efficiently reduced by dividing and superimposing continuous light. Further, if the distance Lx is set so that at least the beam diameter represented by Formula 1 is larger than the beam diameter B as the array light source, light from all the light emitting points 3 can be superimposed, and the array direction collimating optical system Speckle reduction effect can be maximized. However, in the present embodiment, by further increasing the distance, the width of the light beam is increased, and the fly-eye lens pair 6a, 6b of the integrator optical system to be installed in the subsequent stage can be easily manufactured, which is effective in the integrator optical system. The beam can be split and superimposed.

Next, the spatial light intensity distribution will be described.
The laser light emitted from each light emitting point 3 of the one-dimensional array laser light source 2 has a Gaussian-shaped spatial light intensity distribution, the light intensity at the center of the light beam is the highest, and the light intensity increases exponentially with distance from the center. To drop. In order to make such a distribution sufficiently uniform by the fly-eye integrator 6, the laser light having a Gaussian distribution is divided by as many lens cells as possible in the fly-eye lenses 6a and 6b, and the light beam is written for each divided light beam. It is necessary to make the spatial light intensity distribution uniform by projecting onto the irradiated portion of the bulb 7. When the light emitting points 3 are arranged at high density as in the one-dimensional array semiconductor laser 2, a plurality of minute lens cells are arranged in parallel in order to provide lens cells corresponding to the light emitted from each light emitting point 3. It is necessary to let For example, the one-dimensional array semiconductor laser 2 used in the present embodiment is a light emitting point that emits light having a half-width of 10 degrees as a divergence angle in the array direction with a size that can be regarded as a point light source (b = 0.04 mm). Are arranged at intervals of 200 μm, and it is not technically easy to manufacture a fly-eye lens in which a plurality of lens cells can be arranged for light emitted from each light emitting point in such a light source.

  However, in the present invention, the laser beam emitted from each light emitting point 3 is incident on the fly-eye lens 6a in an enlarged state by utilizing the beam diffusibility which is a property of the light source itself. For this reason, even when fly eye lens pairs 6a and 6b having a lens cell diameter in the unit of mm and a pitch of the lens cell arrangement as used in the first embodiment are provided, light is emitted from each light emitting point 3. The laser beam is divided into a number of luminous fluxes by using each lens cell provided in the fly-eye lens pair 6a, 6b to the maximum, so that the spatial light on the irradiated surface of the light valve 7 is superimposed. The intensity distribution is uniform enough to be regarded as a rectangle. Furthermore, since the laser beam is incident on an optical member such as a lens in an enlarged state, the energy density of the incident light is reduced, the amount of heat generated by the optical member is suppressed, and the laser output can be easily increased.

  On the other hand, the light intensity distribution in the vertical direction of the array also has a Gaussian-shaped spatial light intensity distribution, and even if the light of each light emitting point 3 having the same spatial light intensity is simply superimposed, the spatial light intensity Distribution improvement is difficult. However, by dividing and superimposing the beam in the array vertical direction by the array vertical direction collimating optical element 5, the light intensity distribution can be made close to a rectangle, and at the same time, the beam diameter is expanded. By expanding the beam diameter, the lens cell can be utilized to the maximum extent even if a fly-eye lens having a lens cell diameter in the unit of mm and the pitch of the lens cell arrangement is used as in the array direction. Can be made uniform so that the spatial light intensity distribution on the irradiated surface of the light valve 7 can be regarded as a rectangle.

  The light intensity distribution generated by the two light beams coherent with each other is as shown in Expression (4). As is clear from Expression (4), the vibration component (the second term part on the right side in Expression (4)). ) Is multiplied by the light intensity (the square of the light amplitude), the speckle contrast generated in the light beam with a high light intensity is large, and conversely the speckle contrast generated in the light beam with a low light intensity is small. The light incident on the fly-eye integrator 6 is transmitted through different lens cells depending on the spatial position, splits into a plurality of incoherent light beams with an optical path difference longer than the coherent distance, and then the entire irradiated portion for each light beam. Therefore, speckle contrast can be reduced. However, when light enters the fly-eye integrator 6 while having a Gaussian-shaped spatial light intensity distribution, the light transmitted through the central lens cell having a high light intensity and the light transmitted through the peripheral lens cell having a low light intensity. Therefore, the effect of speckle having a high contrast caused by light having a high light intensity remains.

  Therefore, in the one-dimensional array semiconductor laser 2, when light that spreads in the vertical direction of the array while having a Gaussian-shaped spatial light intensity distribution is input to the fly eye integrator 6, speckle noise due to division / superimposition in the vertical direction of the array The reduction effect is reduced. However, in the first embodiment, the spatial light intensity distribution of the light incident on the fly-eye integrator 6 is substantially uniformed by the array vertical direction beam shaping optical system 5, so that the division / superimposition in the array vertical direction is superimposed. The speckle reduction effect corresponding to the number can be obtained. That is, the total cell number (n) including not only the number of lens cells in the array direction (n = 50, speckle reduction 1/7) but also the number of lens cells (40) in the array vertical direction as the number of cells in Equation (6). = 2000, speckle reduction 1/40), the speckle reduction effect can be expected.

  As described above, according to the illumination optical system 1 according to the first embodiment of the present invention, the one-dimensional array semiconductor laser 2 which is a laser array light source in which a plurality of light emitting points 3 are arranged in an array, and the laser array light source When the surface defined by the optical axis C (z direction) 2 and the array direction (x direction) is an array surface (xz surface), the light incident from the laser array light source 2 is emitted as parallel light within the array surface. When a collimating lens 4 that is an array direction collimating optical element, a direction perpendicular to the array surface is an array vertical direction (y direction), and a surface defined by the array vertical direction and the optical axis C is an array vertical surface, a laser array The array vertical collimating optical element 5 that emits the light incident from the light source as parallel light in the array vertical plane, the array direction collimating optical element 4 and the array vertical collimating An integrator that divides the light incident through the optical element 5 into a plurality of light beams in a matrix in a plane perpendicular to the optical axis C, and irradiates the divided light beams so as to overlap on the irradiated surface of the light valve 7. A fly-eye integrator 6 that is an optical element, and the array-direction collimating optical element 4 has a predetermined distance from the laser array light source 2 so that divergent light emitted from a plurality of light-emitting points 3 overlaps and enters. Since Lx is arranged so as to be arranged, the light from each light emitting point 3 is overlapped and incident on the array direction collimating optical element 4 by utilizing the divergence of the light emitted from the light emitting point 3 and the laser. Since the beam can be emitted as a beam having a beam diameter wider than the beam diameter B of the entire array light source 2, an integrator optical system can be easily manufactured, and speckle noise and sky It can be emitted to improve the light intensity distribution illumination light suitable for image display.

  In particular, the array vertical collimating optical element 5 divides the light incident from the laser array light source 2 in the array vertical direction by converting the incident light into parallel light in the array vertical plane and emitting the parallel light. And the array vertical direction beam shaping optical element 5a for irradiating the divided light beams so as to be superimposed on the array vertical direction collimating lens 5b. In addition to the collimating effect in the vertical direction of the array, which is emitted as parallel light, the effect of making the spatial light intensity distribution in the vertical direction of the array uniform can be achieved. Therefore, in the integrator optical element, the lens cell in the array vertical direction can also be effectively used for speckle reduction.

  Further, the array vertical direction beam shaping optical element 5a is composed of a one-dimensional multi-stage lens in which a plurality of cylindrical lenses are arranged in parallel on an arc centering on the light emitting point 3 in the array vertical plane. Efficiently divides and superimposes to facilitate collimation in the vertical direction of the array.

  The integrator optical element 6 includes fly-eye lens pairs 6a and 6b in which a plurality of lens cells are arranged in a matrix in a plane perpendicular to the optical axis C, and a lens 6b that is rotationally symmetric with respect to the optical axis C. Since the fly-eye integrator 6 is used, a pair of fly-eye lenses can be easily manufactured, the incident light beam can be reliably divided and superimposed, the spatial light intensity distribution can be made uniform efficiently, and the optical path difference between each divided light beam The phase is shifted and speckle noise can be reduced efficiently.

  The image display apparatus according to the first embodiment of the present invention includes the illumination optical system 1 described above, and a light valve 7 that is a light modulation element that controls the illumination light incident from the illumination optical system 1 to form an image. Since it is configured to include a projection optical system for enlarging and projecting image light from the light modulation element 7 and an image display unit for displaying the enlarged projected image light, it has a bias in spatial light intensity and coherence. Even if a laser light source is used, the illumination optical system 1 that can be easily manufactured enables image display with improved speckle noise and spatial light intensity distribution.

  In the first embodiment, a one-dimensional array semiconductor laser in which light emission points are arranged one-dimensionally is given as an example of a laser array light source in which a plurality of light emission points 3 are arranged in an array. However, the present invention is not limited to this. For example, a solid laser or a surface emitting laser that emits a beam in an array may be used. A two-dimensional laser array in which one-dimensional laser arrays are stacked in the array vertical direction may be used.

  The distance Lx necessary for the present invention is not limited to that shown in the first embodiment, and the beam diameter incident on the collimating lens 4 is sufficiently enlarged so that the integrator optical element 6 can be easily formed. If the distance is an optical distance (optical distance), the distance may be set to have another optical distance. The integrator optical element 6 may have a different configuration depending on conditions such as the specifications of the light source, the size of the irradiated surface, and the focal length.

  Further, as the configuration of the array vertical direction collimating optical element 5, other configurations may be adopted as long as the same action can be achieved. Specifically, instead of the one-dimensional multi-stage lens 5a in which three plano-concave cylindrical lenses are arranged in parallel, for example, three plano-convex cylindrical lenses, a multi-lens in which many plano-convex cylindrical lenses are arranged in parallel, and many A multilens, a gradient index microlens, a holographic element, or the like in which the plano-concave cylindrical lenses are arranged in parallel may be employed. Further, instead of the plano-convex cylindrical lens 5b, for example, a configuration using a spherical lens designed for the spread angles of the xz and yz planes of all light, or the light spread angle by the multi-lens can be absorbed. A configuration in which no element is used may be employed by providing a possible condensing optical system.

  Further, in the present invention, the case where the illumination optical system 1 is applied to an image display device has been described. However, examples of equipment that can use illumination light with improved speckle noise and spatial light intensity distribution include an exposure device and a laser processing device. Application to is also possible. In particular, since the laser beam is configured to be incident on the optical member in an enlarged state using the properties of the laser light source, it is easy to increase the laser output when applied to a laser processing apparatus or the like. .

It is a block diagram which shows the illumination optical system concerning Embodiment 1 of this invention. It is a figure which shows the structure of the one-dimensional array semiconductor laser which is a part of the illumination optical system concerning Embodiment 1 of this invention. It is a figure which shows the structure of the array vertical direction beam shaping optical element which is a part of the illumination optical system concerning Embodiment 1 of this invention. It is a figure which shows the structure of the array vertical direction beam shaping optical element which is a part of the illumination optical system concerning another form of Embodiment 1 of this invention. It is a figure which shows the light intensity distribution with respect to the spatial position when two light beams are superimposed in order to explain speckle noise.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Illumination optical system, 2 One-dimensional array semiconductor laser (laser array light source), 2a Emission end, 3 Light emission point, 4 Collimate lens (array direction collimating optical element),
5, 15 Array vertical direction collimating optical element, 5a, 15a One-dimensional multistage lens ((array vertical direction beam shaping optical element), 5b, 15b Plano-convex cylindrical lens (array vertical direction collimating lens),
6 fly eye integrator (integrator optical element), 6a, 6b fly eye lens (pair), 6c spherical lens,
7 Light valve, Lx, Ly interval (optical distance)

Claims (3)

A laser array light source in which a plurality of light emitting points are arranged in an array; and
When the surface defined by the optical axis and the array direction of the laser array light source is an array surface, an array direction collimating optical element that emits light incident from the laser array light source as parallel light in the array surface;
When the direction perpendicular to the array plane is the array vertical direction and the plane defined by the array vertical direction and the optical axis is the array vertical plane, the light incident from the laser array light source is parallel in the array vertical plane. An array vertical collimating optical element that emits as light,
The light incident through the array direction collimating optical element and the array vertical direction collimating optical element is divided into a plurality of light beams in a matrix in a plane perpendicular to the optical axis, and the divided light beams are irradiated on the irradiated surface. And an integrator optical element that irradiates so as to overlap with each other,
The array direction collimating optical element is disposed at a predetermined interval from the laser array light source so that divergent light emitted from the plurality of light emitting points is overlapped and incident .
The array vertical collimating optical element is
An array vertical collimating lens that converts incident light into parallel light in the array vertical plane and emits the parallel light; and
An array vertical direction beam shaping optical element that divides the light incident from the laser array light source in the array vertical direction, and irradiates the divided light beams so as to be superimposed on the array vertical direction collimating lens;
2. The illumination optical system according to claim 1, wherein the array vertical direction beam shaping optical element is a one-dimensional multistage lens in which a plurality of cylindrical lenses are arranged in parallel on an arc centered on the light emitting point in the array vertical plane . The integrator optical element is a fly eye integrator comprising a pair of fly eye lenses in which a plurality of lens cells are arranged in a matrix in a plane perpendicular to the optical axis, and a lens rotationally symmetric with respect to the optical axis. The illumination optical system according to claim 1 . The illumination optical system according to claim 1 or 2 ,
A light modulation element for controlling the illumination light incident from the illumination optical system to form an image;
A projection optical system for enlarging and projecting image light from the light modulation element;
An image display unit for displaying the enlarged projected image light;
An image display device comprising:

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