Prism and light source device

Abstract

Provided are a prism capable of adjusting the interval, shape and filling rate of beams with a simple structure, and a light source device. The prism has: a first surface including an incident region in which substantially parallel light from a collimating means that converts beams from a laser light source into substantially parallel light is refracted, and the substantially parallel light enters the incidence region, and an emission region in which the substantially parallel light is refracted and emitted; and a second surface facing the first surface and including a reflection region that reflects, toward the emission region, the substantially parallel light entering through the incident region. The substantially parallel light incident on the prism has a beam width in a first direction larger than the beam width in a second direction orthogonal to the first direction, and is arranged at least in the first direction.

Description

Prism, light source device

[0001] The present disclosure relates to a prism and a light source device.

[0002] Patent Document 1 discloses a light source unit. The light source unit in Patent Document 1 includes a light source group in which a plurality of light sources are arranged in a plane in rows and columns, and a first reflecting mirror group arranged on the optical axis of the light source group and reflecting light beams emitted from the light sources constituting each row of the light source group as light beams with a reduced cross-sectional area in the column direction by narrowing the row spacing of the light beams. The first reflecting mirror group is configured by different strip-shaped reflecting mirrors arranged in a stepped pattern on the optical axis of the light beams emitted from each row of the light source group. The reflecting mirrors are arranged to eliminate spacing between the light beams reflected from each reflecting mirror, thereby reducing the cross-sectional area of ​​the light beams.

[0003] JP 2011-13317 A

[0004] In the light source unit of Patent Document 1, the group of reflecting mirrors can narrow the spacing between beams from multiple laser light sources. However, the group of reflecting mirrors has a complex structure in which multiple reflecting mirrors are arranged to eliminate spacing between the beams reflected from each reflecting mirror. To configure the group of reflecting mirrors, it is necessary to adjust the positions and angles of the multiple reflecting mirrors, which is a complex and difficult task.

[0005] In recent years, there has been an increasing use of laser light sources, such as tens to hundreds of semiconductor lasers, as light sources. The beams of laser light sources are generally elliptical, and it is desirable to correct the beam shape so that they approach a perfect circle. The light source unit of Patent Document 1 can narrow the beam spacing, but cannot change the beam shape from an elliptical shape to a perfect circle. Therefore, the light source unit of Patent Document 1 requires the use of an anamorphic optical system, such as an anamorphic lens, which changes the aspect ratio. As a result, a large number of optical components are required, further complicating the structure.

[0006] The present disclosure provides a prism and a light source device that allows adjustment of beam spacing, shape, and fill factor with a simple structure.

[0007] A prism according to one aspect of the present disclosure has a first surface onto which a plurality of substantially parallel beams are incident from a plurality of collimating means that convert a plurality of beams emitted from a plurality of laser light sources into a plurality of substantially parallel beams, and a second surface opposite the first surface. For each of the plurality of substantially parallel beams incident on the prism, the beam width in a first direction is greater than the beam width in a second direction perpendicular to the first direction. The plurality of substantially parallel beams incident on the prism are aligned at least in the first direction. For each of the plurality of substantially parallel beams, the first surface includes an entrance region where the substantially parallel beam is refracted to enter the prism and enter the prism, and an exit region where the substantially parallel beam is refracted to exit the prism, and the second surface includes a reflection region that reflects the substantially parallel beam that entered the prism through the entrance region toward the exit region.

[0008] A light source device according to one aspect of the present disclosure includes a plurality of laser light sources, a plurality of collimating means for converting a plurality of beams emitted from the plurality of laser light sources into a plurality of substantially parallel beams, and a prism having a first surface onto which the plurality of substantially parallel beams from the plurality of collimating means are incident and a second surface facing the first surface. Each of the plurality of substantially parallel beams incident on the prism has a beam width in a first direction greater than a beam width in a second direction perpendicular to the first direction. The plurality of substantially parallel beams incident on the prism are aligned at least in the first direction. For each of the plurality of substantially parallel beams, the first surface includes an entrance region where the substantially parallel beam is refracted to enter the prism and an exit region where the substantially parallel beam is refracted to exit the prism, and the second surface includes a reflection region that reflects the substantially parallel beam that entered the prism through the entrance region toward the exit region.

[0009] Aspects of the present disclosure provide a prism and light source device that allows adjustment of beam spacing, shape, and fill factor with a simple structure.

[0010] a graph showing a relationship between the angle of the first surface of the prism according to the first embodiment and a rate of change of substantially parallel light in a first direction, the rate of change being proportional to the angle of the optical axis of the substantially parallel light emitted from the prism relative to the optical axis of the substantially parallel light incident on the prism; a graph showing a relationship between the angle of the first surface of the prism according to the first embodiment and a filling factor being proportional to the angle of the optical axis of the substantially parallel light emitted from the prism relative to the optical axis of the substantially parallel light incident on the prism; a graph showing a relationship between the angle of the first surface of the prism according to the first embodiment and a rate of change of substantially parallel light in the first direction, the rate of change being proportional to the refractive index of the prism; a graph showing a relationship between the angle of the first surface of the prism according to the first embodiment and a filling factor being proportional to the refractive index of the prism; Graph showing transmittance for light. Image showing the shape of approximately parallel light incident on the prism according to the first embodiment. Image showing the shape of approximately parallel light emitted from the prism according to the first embodiment. Image showing the shape of approximately parallel light reflected by the group of reflecting mirrors according to the first embodiment. Schematic front view of the light source device according to the second embodiment. Graph showing the transmittance for S-polarized light of the first surface of the prism according to the second embodiment. Schematic front view of the light source device according to the third embodiment. Graph showing the transmittance for S-polarized light of the first surface of the prism according to the third embodiment. Schematic front view of the light source device according to the fourth embodiment. Schematic front view of the light source device according to the fifth embodiment. Graph showing the transmittance for P-polarized light of the first surface of the prism according to the fifth embodiment. Schematic front view of the light source device according to the sixth embodiment. Graph showing the transmittance for S-polarized light of the first surface of the prism according to the sixth embodiment.

[0011] [1. Embodiments] Hereinafter, embodiments will be described in detail, with reference to the drawings as appropriate. However, more detailed description than necessary may be omitted. For example, detailed description of already well-known matters or redundant description of substantially identical configurations may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art. Note that the inventor(s) provide the accompanying drawings and the following description to enable those skilled in the art to fully understand the present disclosure, and are not intended to limit the subject matter described in the claims.

[0012] Unless otherwise specified, the positional relationships such as up, down, left, and right are based on the positional relationships shown in the drawings. Each drawing described in the following embodiments is a schematic drawing, and the ratios of the size and thickness of each component in each drawing do not necessarily reflect the actual dimensional ratios. Furthermore, the dimensional ratios of each component are not limited to the ratios shown in the drawings.

[0013] In the following description, when it is necessary to distinguish between multiple components, prefixes such as "first" and "second" are added to the names of the components. However, when the components can be distinguished from each other by the symbols attached to them, the prefixes such as "first" and "second" may be omitted in consideration of readability of the text.

[0014] In the following description, when it is necessary to distinguish between multiple components, suffixes such as "-1" and "-2" are added to the symbols of the components. However, when it is not necessary to distinguish between multiple components, the suffixes "-1" and "-2" may be omitted to improve readability.

[0015] 1 is a schematic diagram of a light source device 1 according to embodiment 1. The light source device 1 is used in, for example, a projector. The light source device 1 includes a plurality of laser light sources 2 and an optical system 3.

[0016] Each of the multiple laser light sources 2 emits a beam B. The beam B is a so-called elliptical beam, in which the intensity distribution at a distance from the laser light source 2, i.e., the far-field pattern, is elliptical. The laser light source 2 is, for example, a semiconductor laser. In this embodiment, the major axis direction, minor axis direction, and optical axis direction of each beam B are aligned along the X direction, Y direction, and Z direction, respectively. The multiple laser light sources 2 are aligned in both the X direction corresponding to the major axis direction of the beam B, and the Y direction corresponding to the minor axis direction of the beam B. In this embodiment, the number of laser light sources 2 is 24. The 24 laser light sources 2 are aligned in four rows X1 to X4 in the X direction and six rows Y1 to Y6 in the Y direction.

[0017] The optical system 3 includes a plurality of collimating means 4 , a prism 5 , and a group of reflecting mirrors 6 .

[0018] The plurality of collimating means 4 collimates the plurality of beams B emitted from the plurality of laser light sources 2, respectively, to form a plurality of substantially parallel light beams L. In each of the plurality of substantially parallel light beams L incident on the prism 5, the beam width in a first direction is larger than the beam width in a second direction perpendicular to the first direction. The beam width of the substantially parallel light beam L in the first direction or the second direction is, for example, 1 / e of the peak radiation intensity of the substantially parallel light beam. ２ The beam width of the substantially parallel light L in the first direction or the second direction may be defined as the distance between two points such that: ∇ ...

[0019] The prism 5 is provided to circularize the beam B (approximately parallel light L) and improve the filling rate of the beam B (approximately parallel light L). The prism 5 has a first surface 51 onto which the plurality of approximately parallel light beams L from the plurality of collimating means 4 are incident, and a second surface 52 opposite to the first surface 51.

[0020] 2 is a partially enlarged view of the prism 5. The prism 5 has, for each of the plurality of substantially parallel light beams L, an entrance region R1 where the substantially parallel light beam L is refracted and enters the prism 5 and an exit region R2 where the substantially parallel light beam L is refracted and exits the prism 5 on the first surface 51, and a reflection region R3 on the second surface 52 that reflects the substantially parallel light beam L that entered the prism 5 through the entrance region R1 toward the exit region R2.

[0021] The light source device 1, and in particular the prism 5, will be further described with reference to Figures 3 and 4. Figure 3 is a schematic front view of the light source device 1, particularly as seen from the -Y direction. Figure 4 is another schematic side view of the light source device 1, particularly as seen from the -X direction. Note that the reflective mirror group 6 is omitted in Figures 3 and 4.

[0022] The first surface 51 is a flat surface. The incident region R1 and the exit region R2 for each of the substantially parallel light beams L are located on the same plane. In this embodiment, the incident regions R1 and the exit regions R2 for the plurality of substantially parallel light beams L are located on the same plane. The incident region R1 is a portion of the first surface 51 where the substantially parallel light beams L are incident. The center of the incident region R1 is the position where the central luminous flux L1 of the substantially parallel light beams L passes. The size of the incident region R1 is determined so that the radiation intensity of the substantially parallel light beams L is 1 / e of the radiation intensity of the substantially parallel light beams L at the center of the incident region R1. ２ The exit region R2 is a portion of the first surface 51 from which the substantially parallel light L is emitted. The center of the exit region R2 is a position where the central luminous flux L1 of the substantially parallel light L passes through. The size of the exit region R2 is determined so that the radiation intensity of the substantially parallel light L is 1 / e of the radiation intensity of the substantially parallel light L at the center of the exit region R2. ２ The range may be as follows.

[0023] The first surface 51 includes an incident region R1 and an exit region R2 corresponding to each of the multiple laser light sources 2. In FIG. 3, if the laser light sources 2 adjacent to each other in the first direction are the first laser light source 2-1 and the second laser light source 2-2, the first surface 51 includes a first incident region R1-1 and a first exit region R2-1 corresponding to the first laser light source 2-1, and a second incident region R1-2 and a second exit region R2-2 corresponding to the second laser light source 2-2. The first exit region R2-1 is located between the first incident region R1-1 and the second incident region R1-2. This reduces the overlapping portion of the first surface 51 between the exit region R2 and the incident region R1. This reduces partial thermal expansion of the first surface 51. In FIG. 3, the first exit region R2-1 partially overlaps with the first entrance region R1-1, but it is more preferable that it does not overlap with either the first entrance region R1 or the second entrance region R1.

[0024] Here, the distance on the first surface 51 between the centers of the incident regions R1 (first incident region R1-1 and second incident region R1-2) of the plurality of substantially parallel light beams L that are adjacent in the first direction is defined as s [mm]. The distance on the first surface 51 between the midpoint m between the centers of the incident regions R1 (first incident region R1-1 and second incident region R1-2) and the exit region R2 (first exit region R2-1) of the adjacent substantially parallel light beams L that is closest to the midpoint m is defined as t [mm]. The distances s and t vary depending on the refractive index n, the angles α, β, and γ, and the thickness d [mm] of the prism 5 in the direction of the optical axis of the substantially parallel light beams L that are incident on the prism 5. It is preferable that the prism 5 satisfy |2t / s|<0.3. In particular, it is preferable that |2t / s| = 0 be satisfied (i.e., t = 0). This allows the substantially parallel light L adjacent in the first direction from the laser light source 2 to exit the first surface 51 of the prism 5 so as to avoid overlapping as much as possible between the entrance regions R1 where the substantially parallel light L enters the first surface 51 of the prism 5. This makes it possible to reduce the area where the entrance region R1 and exit region R2 of the substantially parallel light L overlap, thereby suppressing the effects of temperature rise and the resulting changes in the refractive index and shape of the prism 5.

[0025] The second surface 52 is a stepped surface in which a plurality of parallel first inclined surfaces 52a and a plurality of parallel second inclined surfaces 52b are alternately arranged when viewed from the second direction (±Y direction) of the substantially parallel light L incident on the first surface 51. Therefore, the plurality of first inclined surfaces 52a are not located on the same plane.

[0026] The plurality of first inclined surfaces 52a include the reflective region R3. The plurality of second inclined surfaces 52b are surfaces that connect adjacent first inclined surfaces 52a. The second inclined surfaces 52b are not used as the reflective region R3.

[0027] The center of the reflection region R3 is a position where the central luminous flux L1 of the substantially parallel light L passes. The size of the reflection region R3 is determined such that the radiation intensity of the substantially parallel light L is 1 / e ２ The range may be as follows.

[0028] In this embodiment, the second surface 52 includes four first inclined surfaces 52a-1 to 52a-4. The first inclined surface 52a-1 defines the reflection region R3 of the six laser light sources 2 in row X1. Similarly, the first inclined surfaces 52a-2 to 52a-4 correspond to rows X2 to X4. In each of rows X1 to X4, the reflection regions R3 are located on the same plane. In each of rows Y1 to Y6, the reflection regions R3 are not located on the same plane.

[0029] In the prism 5, the distances between the centers of the multiple first inclined surfaces 52a and the first surface 51 are equal to each other. As a result, for each of the multiple substantially parallel light beams L, the distances between the centers of the incident region R1 and the reflection region R3 are equal, and the distances between the centers of the exit region R3 and the reflection region R1 are equal.

[0030] 3, the first surface 51 is inclined with respect to a first direction (±X direction) of the substantially parallel light L incident on the first surface 51, and the first inclined surface 52a and the second inclined surface 52b are inclined with respect to the first direction (±X direction) of the substantially parallel light L incident on the first surface 51. As shown in Fig. 4, the first surface 51 is not inclined but is parallel with the second direction (±Y direction) of the substantially parallel light L incident on the first surface 51, and the first inclined surface 52a and the second inclined surface 52b are not inclined but are parallel with the second direction (±Y direction) of the substantially parallel light L incident on the first surface 51.

[0031] In the prism 5, the angle of the first surface 51 with respect to the first direction (the ±X direction in FIG. 3 ) is defined as α [°], and the angle of the first inclined surface 52a of the second surface 52 is defined as β [°]. The angle α is the angle between the incident region R1 and the exit region R2, and the angle β is the angle of the reflection region R3. The prism 5 satisfies β > α. The angle α is equal to the angle of incidence of the substantially parallel light L with respect to the incident region R1.

[0032] In this embodiment, the first surface 51 faces the side (right side in FIG. 3 ) from which the plurality of substantially parallel light beams L enter the prism 5 and exit the prism 5. In this case, the angles α and β are defined as positive in the rotation direction (counterclockwise direction in FIG. 3 ) in which the first surface 51 approaches the second surface 52 around a rotation axis A1 along a second direction (±Y direction in FIG. 3 ) on the opposite side (left side in FIG. 3 ) from the side (right side in FIG. 3 ) from which the plurality of substantially parallel light beams L enter the prism 5 and exit the prism 5. That is, in FIG. 3 , the +X direction is defined as 0°, and the counterclockwise direction is defined as positive. In FIG. 3 , the rotation axis A1 is illustrated at the end of the first surface 51 on the opposite side (left side in FIG. 3 ) from the side (right side in FIG. 3 ) from which the plurality of substantially parallel light beams L enter the prism 5 and exit the prism 5. The rotation axis A1 is used solely to determine the positive and negative of the angles α and β, and does not necessarily refer to the rotation axis of the first surface 51 and the second surface 52. When the first surface 51 is parallel to the first direction, the angle α = 0. In Figure 3, when the first surface 51 rotates counterclockwise from a position parallel to the first direction, the angle α is positive, and when the first surface 51 rotates clockwise from a position parallel to the first direction, the angle α is negative. The same is true for the angle β.

[0033] 3, the refraction angle of the substantially parallel light L with respect to the emission region R2 is θ [°]. If the refractive index of the prism 5 is n, the prism 5 satisfies the following formula (1).

[0034]

[0035] If the angle of the optical axis of the approximately parallel light L emitted from the prism 5 with respect to the optical axis of the approximately parallel light L incident on the prism 5 is γ, the following equation (2) is satisfied.

[0036]

[0037] 3, the substantially parallel light L is incident on the entrance region R1 of the first surface 51, is refracted by the entrance region R1, enters the prism 5, and travels inside the prism 5 toward the first inclined surface 52a. The substantially parallel light L is reflected by the reflection region R3 of the first inclined surface 52a and travels inside the prism 5 toward the first surface 51. The substantially parallel light L is refracted at the exit region R2 of the first surface 51 and is emitted from the exit region R2 to the outside of the prism 5. This narrows the beam width of the substantially parallel light L in the first direction and the spacing between the multiple substantially parallel light beams L in the first direction.

[0038] Here, the spacing in the first direction of the substantially parallel light L incident on the prism 5 is a1, and the beam width in the first direction is b1. The spacing in the third direction corresponding to the first direction of the substantially parallel light L emitted from the prism 5 is a2, and the beam width in the third direction is b2. The prism 5 satisfies a2<a1 and b2<b1.

[0039] FIG. 5 is a graph showing the relationship between the angle α of the first surface 51 of the prism 5 and the rate of change of the substantially parallel light L in the first direction, as a function of the angle γ.

[0040] The rate of change of the substantially parallel light L in the first direction is expressed as a percentage of b2 / b1. Therefore, a rate of change of 100% means that the beam width in the first direction does not change. A rate of change exceeding 100% means that the beam width in the first direction increases. In this case, the rate of change corresponds to an expansion rate. A rate of change less than 100% means that the beam width in the first direction decreases. In this case, the rate of change corresponds to a reduction rate. An increase in the rate of change means an improvement in the expansion rate, and a decrease in the rate of change means an improvement in the reduction rate. A rate of change of 50% means that the beam width in the first direction is reduced by half.

[0041] It can be seen from Fig. 5 that the rate of change tends to increase as the angle α of the first surface 51 increases. It can also be seen from Fig. 5 that even if the angle α is the same, the rate of change tends to decrease as the angle γ increases. It can be seen from Fig. 5 that a desired rate of change can be obtained by appropriately setting the angles α and γ.

[0042] FIG. 6 is a graph showing the relationship between the angle α of the first surface 51 of the prism 5 and the filling rate of the substantially parallel light L in the first direction, as a function of the angle γ.

[0043] The filling factor of the substantially parallel light L in the first direction is expressed as the ratio of the beam width of the substantially parallel light L in the first direction to the distance between the same portions of the substantially parallel light L adjacent to each other in the first direction. If the distance between the same portions of the substantially parallel light L adjacent to each other in the first direction of the substantially parallel light L incident on the prism 5 is c1, the filling factor of the substantially parallel light L incident on the prism 5 is expressed as b1 / c1. Since the distance c1 is equal to the interval a1, b1 / c1 = b1 / a1. If the distance between the same portions of the substantially parallel light L adjacent to each other in a third direction corresponding to the first direction of the substantially parallel light L emitted from the prism 5 is c2, the filling factor of the substantially parallel light L emitted from the prism 5 is expressed as b2 / c2. Since the distance c2 is equal to the interval a2, b2 / c2 = b2 / a2.

[0044] FIG. 6 shows the filling rate of the approximately parallel light L emitted from the prism 5 when the filling rate of the approximately parallel light L incident on the prism 5 is 50%.

[0045] A higher filling rate means that the beam can be more integrated. A higher filling rate of the substantially parallel light L emitted from the prism 5 than the filling rate of the substantially parallel light L incident on the prism 5 means that the beam can be more integrated. In Figure 6, the filling rate of the substantially parallel light L incident on the prism 5 is 50%, so if the filling rate in Figure 6 exceeds 50%, the filling rate has improved, which means that more integration has been achieved.

[0046] Therefore, the prism 5 is set so as to satisfy the following formula (3).

[0047]

[0048] That is, in the prism 5 , the filling rate of the approximately parallel light L emitted from the prism 5 is greater than the filling rate of the approximately parallel light L incident on the prism 5 .

[0049] 6, in order to increase the filling rate after emission, it is desirable to decrease the angle α or increase the angle γ. It can also be seen that when the angle γ is less than 90°, it is advantageous to make the angle α a negative value.

[0050] Considering the rate of change of the substantially parallel light L in the first direction and the filling rate, it is preferable that the prism 5 satisfies the following formula (4).

[0051]

[0052] If α≦γ−90, there is a possibility that the substantially parallel light L reflected by the reflection region R3 will be totally reflected by the emission region R2 of the first surface 51. If α≧γ / 2, there is a possibility that the rate of change will be 100% or more.

[0053] Generally, the ellipticity of a semiconductor laser (the ratio of the beam width in the minor axis direction to the beam width in the major axis direction) is approximately 0.2 to 0.5. Therefore, in order to bring the ellipticity closer to 1, it is preferable that the prism 5 satisfy the following expressions (5) and (6).

[0054]

[0055]

[0056] When γ≦50, the substantially parallel light L emitted from the emission region R2 approaches the laser light source 2, which may make it difficult to configure the optical system 3. When γ≧100, the substantially parallel light L is more likely to be totally reflected in the emission region R2, and wasted space may be generated in the optical system 3. When α≦1.1γ−90, the effect of compressing the beam width of the substantially parallel light L in the first direction decreases, and when α≧0.95γ−60, the effect of compressing the substantially parallel light L in the first direction becomes too great, and the shape of the substantially parallel light L may become elliptical rather than circular, in which the beam width in the first direction is smaller than the beam width in the second direction.

[0057] FIG. 7 is a graph showing the relationship between the angle α of the first surface 51 of the prism 5 and the rate of change of the substantially parallel light L in the first direction, with respect to the refractive index n.

[0058] 7, the refractive index n is changed to 1.4, 1.5, and 1.7 when the angle γ is 60° and when the angle γ is 90°. From FIG. 7, it can be seen that the relationship between the angle α and the rate of change is little dependent on the refractive index n of the prism 5.

[0059] FIG. 8 is a graph showing the relationship between the angle α of the first surface 51 of the prism 5 and the filling rate of the substantially parallel light L in the first direction, as a function of the refractive index n.

[0060] 8, the refractive index n is changed to 1.4, 1.5, and 1.7 when the angle γ is 60° and when the angle γ is 90°. The filling factor in Fig. 8 indicates the filling factor of the approximately parallel light L emitted from the prism 5, and here, the filling factor of the approximately parallel light L incident on the prism 5 is 50%.

[0061] 8, it can be seen that in order to increase the filling rate to 50% or more, it is effective to lower the refractive index n of the prism 5. It can also be seen that in order to obtain the highest filling rate by selecting the angle α, it is effective to increase the angle γ.

[0062] Table 1 below shows an example of parameters of the light source device 1 according to this embodiment.

[0063]

[0064] The prism 5 compresses the beam width of the substantially parallel light L in the first direction. The beam width of the substantially parallel light L in the first direction is larger than the beam width in the second direction. Therefore, by compressing the beam width of the substantially parallel light L in the first direction, the substantially parallel light L changes from an elliptical shape to a shape closer to a perfect circle. Furthermore, the prism 5 makes it possible to improve the filling rate of the substantially parallel light L in the first direction.

[0065] In consideration of the light utilization efficiency of the prism 5, an anti-reflection film is formed on the first surface 51. When the laser light source 2 is a general semiconductor laser, the beam B is linearly polarized light. Since the first surface 51 includes an entrance region R1 and an exit region R2, the transmittance T of the entrance region R1 for a predetermined linearly polarized light is α , the transmittance T of the output region R2 for a predetermined linearly polarized light θThen, it is preferable that an anti-reflection film is formed on the first surface 51 so as to satisfy the following formula (7). In this embodiment, the beam B is S-polarized in the major axis direction and P-polarized in the minor axis direction. In this embodiment, the first direction of the approximately parallel light L corresponds to the major axis direction of the beam B. Therefore, in the first direction of the approximately parallel light L, the transmittance for S-polarized light is taken into consideration. In other words, the specified linearly polarized light is S-polarized.

[0066]

[0067] 9 is a graph showing the transmittance of the first surface 51 of the prism 5 for S-polarized light. G11 and G12 correspond to the anti-reflection coating of the first example. G21 and G22 correspond to the anti-reflection coating of the second example. G11 and G21 are the transmittance T α G12 and G22 show the change in transmittance T for S-polarized light of the output region R2 with respect to wavelength. θ The change in the transmittance T for S-polarized light in the incident region R1 is shown. α indicates the transmittance for light incident on the first surface 51 at an angle α. The transmittance T θ denotes the transmittance for light incident on the first surface 51 at an angle equal to the refraction angle θ.

[0068] The reference wavelength of the prism 5 and the anti-reflection coatings of the first and second examples is 450 nm. The material of the prism 5 is glass, and the refractive index for the reference wavelength is 1.52532. The anti-reflection coating of the first example is a conventionally known MgF ２ The antireflection film of the second example is a multilayer film in which layers made of materials with different refractive indices at the reference wavelength are alternately stacked. Table 2 below shows the configuration of the antireflection film of the second example.

[0069]

[0070] From G11 and G12, the transmittance T α is 98% or more over a wide wavelength range, but the transmittance T θThe transmittance is 12% or less over a wide wavelength range. This means that the single-layer coatings that have been commonly used so far have low transmittance. Therefore, an improvement in transmittance is desired.

[0071] From G21 and G22, in the antireflection coating of the second example, the transmittance T α , T θ are all high, and in the range of W11 to W12, T α ・T θ ≧90%. W11 is 437 nm, and W12 is 467 nm. Therefore, in the case of the anti-reflection film of the second example, even if light passes through the first surface 51 of the prism 5 twice, the total transmittance (=T α ・T θ ) can ensure a high transmittance of 90% or more.

[0072] In this way, with one prism 5, the substantially parallel light L can be changed from an elliptical shape to a shape closer to a perfect circle, the spacing of the substantially parallel light L in the first direction can be narrowed, and the filling rate of the substantially parallel light L can be improved. Therefore, the optical system 3 can be made more compact.

[0073] The reflecting mirror group 6 is provided to improve the filling rate of the substantially parallel light beams L. The reflecting mirror group 6 includes a plurality of reflecting mirrors 6a-1 to 6a-6 that reflect the plurality of substantially parallel light beams L emitted from the prism 5. The plurality of reflecting mirrors 6a-1 to 6a-6 are arranged such that the intervals in the second direction between the plurality of substantially parallel light beams L after being reflected by the reflecting mirror group 6 are smaller than the intervals in the second direction between the plurality of substantially parallel light beams L before being reflected by the reflecting mirror group 6.

[0074] [1.1.2 Evaluation, etc.] In order to confirm the effects of the light source device 1 according to this embodiment, the shape of the substantially parallel light L was evaluated.

[0075] Fig. 10 is an image showing the shape of the approximately parallel light L entering the prism 5 from the collimating means 4. Fig. 11 is an image showing the shape of the approximately parallel light L emitted from the prism 5. Fig. 12 is an image showing the shape of the approximately parallel light L reflected by the group of reflecting mirrors 6. In Figs. 10 to 12, whiter colors indicate higher radiation intensity. X1 to X4 and Y1 to Y6 in Figs. 10 to 12 correspond to X1 to X4 and Y1 to Y6 in Fig. 1.

[0076] As can be seen from Figure 10, after the approximately parallel light L is emitted from the collimating means 4 and before it enters the prism 5, the beam width in the first direction (the ±X direction in Figure 10) is larger than the beam width in the second direction (the ±Y direction in Figure 10), and the approximately parallel light L has an elliptical shape.

[0077] 11, after the substantially parallel light L is emitted from the prism 5 and before it is incident on the group of reflecting mirrors 6, the beam width in the first direction (the ±Z direction in FIG. 11) is small to the same extent as the beam width in the second direction (the ±Y direction in FIG. 11), and the substantially parallel light L is closer to a perfect circle than an ellipse. Furthermore, the interval of the substantially parallel light L in the first direction is narrow.

[0078] As can be seen from FIG. 12, after being emitted from the group of reflecting mirrors 6, the intervals of the substantially parallel light L in the second direction (the ±X direction in FIG. 12) become narrower.

[0079] In the light source device 1 described above, it was confirmed that the spacing between the approximately parallel light beams L narrows in both the first and second directions, and the shape of the approximately parallel light beams L changes from an elliptical shape to one closer to a perfect circle, resulting in an improvement in the degree of beam concentration.

[0080] [1.1.3 Effects, etc.] The prism 5 described above has a first surface 51 onto which the plurality of substantially parallel light beams L are incident from the plurality of collimating means 4 that convert the plurality of beams B emitted from the plurality of laser light sources 2 into a plurality of substantially parallel light beams L, and a second surface 52 facing the first surface 51. For each of the plurality of substantially parallel light beams L incident on the prism 5, the beam width in the first direction is greater than the beam width in a second direction perpendicular to the first direction. The plurality of substantially parallel light beams L incident on the prism 5 are aligned at least in the first direction. For each of the plurality of substantially parallel light beams L, the first surface 51 includes an entrance region R1 where the substantially parallel light beam L is refracted and enters the prism 5, and an exit region R2 where the substantially parallel light beam L is refracted and exits the prism 5, and the second surface 52 includes a reflection region R3 that reflects the substantially parallel light beam L that entered the prism 5 through the entrance region R1 toward the exit region R2. This configuration allows adjustment of the beam spacing, shape, and filling rate with a simple structure.

[0081] In the prism 5, when the angle of the incident region R1 and the exit region R2 with respect to the first direction is α [°] and the angle of the reflection region R3 is β [°], the relationship β > α is satisfied. This configuration can narrow the interval of the beams (approximately parallel light L) with a simple structure, and further enables the beams (approximately parallel light L) to be made perfectly circular and the filling rate to be improved.

[0082] In the prism 5, if the spacing in the first direction of the plurality of substantially parallel light beams L incident on the prism 5 is a1, the beam width in the first direction is b1, and the spacing in the third direction corresponding to the first direction of the plurality of substantially parallel light beams L emitted from the prism 5 is a2, and the beam width in the third direction is b2, then b2 / a2>b1 / a1 is satisfied. This configuration not only compresses the beam spacing in the first direction, but also improves the beam filling rate.

[0083] In the prism 5, when the refractive index of the prism 5 is n and the refraction angle of the plurality of substantially parallel light beams L with respect to the emission region R2 is θ [°], θ=sin －１ (n・sin(sin －１ (sin α / n)+2(β-α))) is satisfied. The transmittance T α [%], transmittance T for a predetermined straight line (S-polarized light) in the exit region R2 θ [%], T α ・Tθ ≧90%. This configuration can achieve high transmittance even when there are two refractions at different angles in the incident region R1 and the exit region R2.

[0084] In the prism 5, the entrance region R1 and the exit region R2 are located on the same plane in the first direction. This configuration allows the structure of the prism 5 to be simplified.

[0085] In the prism 5, the reflective regions R2 are arranged so as not to be positioned on the same plane in the first direction. This configuration enables the prism 5 to be made thinner.

[0086] In the prism 5, the distance between the center of the incident region R1 and the center of the reflection region R3 is equal, and the distance between the center of the exit region R2 and the center of the reflection region R3 is equal for each of the plurality of substantially parallel light beams L. This configuration enables the prism 5 to be made thinner.

[0087] In the prism 5, if the distance on the first surface 51 between the centers of the incident regions R1 of adjacent substantially parallel light beams L in the first direction among the plurality of substantially parallel light beams L is s [mm], and the distance on the first surface 51 between the midpoint m between the centers and the exit region R2 closest to the midpoint m among the exit regions R2 of adjacent substantially parallel light beams L is t [mm], then |2t / s|<0.3 is satisfied. This configuration can reduce the overlapping portion between the incident region R1 and the exit region R2, thereby reducing partial thermal expansion of the first surface 51.

[0088] In the prism 5, when the angle of the optical axis of the plurality of substantially parallel light beams L emitted from the prism 5 with respect to the optical axis of the plurality of substantially parallel light beams L incident on the prism 5 is γ [°], the relationship γ-90<α<γ / 2 is satisfied. This configuration enables improvement of the reduction ratio and filling rate of the substantially parallel light beams L in the first direction.

[0089] The prism 5 further satisfies 50<γ<100 and 1.1γ-90<α<0.95γ-60. This configuration enables further improvement in the reduction ratio and filling ratio of the substantially parallel light L in the first direction.

[0090] The light source device 1 described above includes a plurality of laser light sources 2, a plurality of collimating means 4 that convert a plurality of beams B emitted from the plurality of laser light sources 2 into a plurality of substantially parallel light beams L, and a prism 5 having a first surface 51 onto which the plurality of substantially parallel light beams L are incident from the plurality of collimating means 4 and a second surface 52 facing the first surface 51. For each of the plurality of substantially parallel light beams L incident on the prism 5, the beam width in the first direction is greater than the beam width in a second direction perpendicular to the first direction. The plurality of substantially parallel light beams L are aligned at least in the first direction. For each of the plurality of substantially parallel light beams L, the first surface 51 includes an entrance region R1 where the substantially parallel light beam L is refracted and enters the prism 5, and an exit region R2 where the substantially parallel light beam L is refracted and exits the prism 5. The second surface 52 includes a reflection region R3 that reflects the substantially parallel light beam L that entered the prism 5 through the entrance region R1 toward the exit region R2. This configuration enables adjustment of the beam spacing, shape, and filling rate with a simple structure.

[0091] In the light source device 1, the plurality of substantially parallel light beams L incident on the prism 5 are aligned in both the first and second directions. In this configuration, the laser light source 2 is arranged on a plane, making it possible to achieve high output.

[0092] The light source device 1 further includes a reflecting mirror group 6 that reflects the plurality of substantially parallel light beams L emitted from the prism 5. The reflecting mirror group 6 includes a plurality of reflecting mirrors 6a that are arranged such that the intervals in the second direction between the plurality of substantially parallel light beams L after being reflected by the reflecting mirror group 6 are smaller than the intervals in the second direction between the plurality of substantially parallel light beams L before being reflected by the reflecting mirror group 6. This configuration can also compress the intervals between the beams in the second direction.

[0093] 13 is a schematic side view of a light source device 1A according to a second embodiment, particularly as viewed from the -Y direction. The light source device 1A includes a plurality of laser light sources 2 and an optical system 3A. The optical system 3A includes a plurality of collimating means 4 and a prism 5A.

[0094] The prism 5A has a first surface 51 and a second surface 52, similar to the prism 5, but differs from the prism 5 mainly in the refractive index n, the angles α, β, γ, and the thickness d.

[0095] Table 3 below shows an example of parameters of the light source device 1A according to this embodiment.

[0096]

[0097] From a comparison between Tables 1 and 3, it can be seen that the filling rate can be improved by lowering the refractive index of the prism.

[0098] 14 is a graph showing the transmittance of the first surface 51 of the prism 5A for S-polarized light. G31 is the transmittance T α G32 indicates the change in transmittance T θ The change in transmittance T α indicates the transmittance for light incident on the first surface 51 at an angle α (=5°). θ indicates the transmittance for light incident on the first surface 51 at an angle equal to the refraction angle θ (=80°).

[0099] The reference wavelength of the prism 5A and the anti-reflection coating is 450 nm. The material of the prism 5A is glass, and the refractive index for the reference wavelength is 1.4391. The anti-reflection coating of the prism 5A is a multilayer coating in which layers made of materials with different refractive indices for the reference wavelength are alternately stacked. Table 4 below shows the configuration of the anti-reflection coating.

[0100]

[0101] From G41 and G42, in the anti-reflection coating having the configuration of Table 4, in the wavelength range of W21 to W22 including the reference wavelength, T α ・T θ ≧90%. W21 is 442 nm, and W22 is 460 nm. Therefore, with the anti-reflection film having the configuration shown in Table 4, even if light passes through the first surface 51 of the prism 5A twice, the total transmittance (=T α ・T θ ) can ensure a high transmittance of 90% or more.

[0102] In this way, the prism 5A makes it possible to adjust the beam spacing, shape, and filling rate. In particular, a single prism 5A can change the shape of the substantially parallel light L from an elliptical shape to one closer to a perfect circle, thereby narrowing the spacing of the substantially parallel light L in the first direction and improving the filling rate of the substantially parallel light L. This allows the optical system to be made more compact.

[0103] [1.2.2 Effects, etc.] The prism 5A described above satisfies β>α. This configuration can narrow the interval between beams (approximately parallel light L) with a simple structure, and further enables the beams (approximately parallel light L) to be made perfectly circular and the filling rate to be improved.

[0104] The prism 5A satisfies b2 / a2>b1 / a1. This configuration can not only compress the spacing between the beams in the first direction but also improve the beam filling rate.

[0105] The prism 5A has a θ=sin －１ (n・sin(sin －１ (sin α / n)+2(β-α))) and T α ・T θ ≧90%. This configuration can achieve high transmittance even when there are two refractions at different angles in the incident region R1 and the exit region R2.

[0106] The prism 5A satisfies γ-90<α<γ / 2. This configuration makes it possible to improve the reduction ratio and filling ratio of the substantially parallel light L in the first direction.

[0107] The prism 5A further satisfies 50<γ<100 and 1.1γ-90<α<0.95γ-60. This configuration enables further improvement in the reduction ratio and filling ratio of the substantially parallel light L in the first direction.

[0108] 15 is a schematic side view of a light source device 1B according to a third embodiment, particularly as viewed from the -Y direction. The light source device 1B includes a plurality of laser light sources 2 and an optical system 3B. The optical system 3B includes a plurality of collimating means 4 and a prism 5B.

[0109] The prism 5B has a first surface 51 and a second surface 52, similar to the prism 5, but differs from the prism 5 mainly in the refractive index n, the angles α, β, γ, and the thickness d.

[0110] Table 5 below shows an example of parameters of the light source device 1B according to this embodiment.

[0111]

[0112] A comparison of Tables 1 and 5 reveals that increasing the refractive index of the prism reduces the apex angle of prism 5B, which is defined by the difference between angle α and angle β. This makes second surface 52 of prism 5B closer to a flat surface, making it easier to achieve shape precision when manufacturing prism 5B by glass molding or the like.

[0113] 16 is a graph showing the transmittance of the first surface 51 of the prism 5B for S-polarized light. G41 is the transmittance T α G42 indicates the change in transmittance T θ The change in transmittance T α indicates the transmittance for light incident on the first surface 51 at an angle α (=25°). θ indicates the transmittance for light incident on the first surface 51 at an angle equal to the refraction angle θ (=65°).

[0114] The reference wavelength of prism 5B and the anti-reflection coating is 500 nm. Prism 5B is made of glass, and its refractive index for the reference wavelength is 1.62904. The anti-reflection coating of prism 5B is a multilayer coating in which layers made of materials with different refractive indices for the reference wavelength are alternately stacked. Table 6 below shows the configuration of the anti-reflection coating.

[0115]

[0116] From G41 and G42, in the anti-reflection coating having the configuration of Table 6, in the wavelength range of W31 to W32 including the reference wavelength, T α ・T θ ≧90%. W31 is 487 nm, and W32 is 656 nm. Therefore, in the case of the anti-reflection film having the configuration in Table 6, even if light passes through the first surface 51 of the prism 5B twice within the very wide wavelength range of approximately 170 nm, the total transmittance (=Tα ・T θ ) can ensure a high transmittance of 90% or more. Therefore, even when semiconductor lasers with two wavelength bands, green and red, are used, it is possible to improve the transmittance of both bands with only the antireflection film having the configuration shown in Table 6. Furthermore, unlike the antireflection films having the configurations shown in Table 2 or Table 4b, the antireflection film having the configuration shown in Table 6 can be simply a two-layer structure.

[0117] In this way, the prism 5B makes it possible to adjust the beam spacing, shape, and filling rate. In particular, a single prism 5B can change the shape of the substantially parallel light L from an elliptical shape to one closer to a perfect circle, thereby narrowing the spacing of the substantially parallel light L in the first direction and improving the filling rate of the substantially parallel light L. This allows the optical system to be made more compact.

[0118] [1.3.2 Effects, etc.] The prism 5B described above satisfies β>α. This configuration can narrow the interval between beams (approximately parallel light L) with a simple structure, and further enables the beams (approximately parallel light L) to be made perfectly circular and the filling rate to be improved.

[0119] The prism 5B satisfies b2 / a2>b1 / a1. This configuration can not only compress the spacing between the beams in the first direction but also improve the beam filling rate.

[0120] The prism 5B has a θ=sin －１ (n・sin(sin －１ (sin α / n)+2(β-α))) and T α ・T θ ≧90%. This configuration can achieve high transmittance even when there are two refractions at different angles in the incident region R1 and the exit region R2.

[0121] The prism 5B satisfies γ-90<α<γ / 2. This configuration makes it possible to improve the reduction ratio and filling ratio of the substantially parallel light L in the first direction.

[0122] Prism 5B further satisfies 50<γ<100 and 1.1γ-90<α<0.95γ-60. This configuration enables further improvement in the reduction ratio and filling ratio of the substantially parallel light L in the first direction.

[0123] 17 is a schematic side view of a light source device 1C according to a fourth embodiment, particularly as viewed from the -Y direction. The light source device 1C includes a plurality of laser light sources 2 and an optical system 3C. The optical system 3C includes a plurality of collimating means 4 and a prism 5C.

[0124] The prism 5B has a first surface 51 and a second surface 52, similar to the prism 5, but differs from the prism 5 mainly in the refractive index n, the angles α, β, γ, and the thickness d.

[0125] In this embodiment, the first surface 51 faces the opposite side from the side from which the plurality of substantially parallel light beams L enter the prism 5 (the right side in FIG. 17 ) exit the prism 5. In this case, the angles α and β are defined as positive in the rotation direction (clockwise direction in FIG. 17 ) in which the first surface 51 moves away from the second surface 52 around a rotation axis A1 along a second direction (the ±Y direction in FIG. 17 ) on the opposite side (the left side in FIG. 17 ) from the side from which the plurality of substantially parallel light beams L enter the prism 5 (the right side in FIG. 17 ). That is, in FIG. 17 , the −X direction is defined as 0°, and the clockwise direction is defined as positive. Note that in FIG. 17 , the rotation axis A1 is illustrated at the end of the first surface 51 on the opposite side (the left side in FIG. 17 ) from the side from which the plurality of substantially parallel light beams L exit the prism 5 (the right side in FIG. 17 ) from the plurality of substantially parallel light beams L enter the prism 5.

[0126] Table 7 below shows an example of parameters of the light source device 1C according to this embodiment.

[0127]

[0128] Thus, even if the first surface 51 faces the opposite side of the plurality of substantially parallel light beams L incident on the prism 5 rather than the side from which the plurality of substantially parallel light beams L exit the prism 5 (the right side in FIG. 17 ), the substantially parallel light beams L can still pass through the incident region R1 and enter the prism 5C. A comparison of Tables 1 and 7 reveals that the fill factor is significantly higher when the first surface 51 faces the opposite side of the plurality of substantially parallel light beams L incident on the prism 5 from the side from which the plurality of substantially parallel light beams L exit the prism 5. In particular, while the fill factor of the substantially parallel light beams L incident on the prism 5C is 50.0%, the fill factor of the substantially parallel light beams L exiting the prism 5C is a very high 84.1%, which significantly improves the beam integration of the prism 5C and allows the beam to be focused within a narrower range. This allows the optical system 3C to be more compact. 17 is set to 0° and the counterclockwise direction is set to positive, the angle α is −20.000 and the angle β is 6.604, and in this case too, β>α is satisfied. From this point of view, the angle α being negative can be said to mean that the first surface 51 faces in the direction opposite to the side from which the plurality of substantially parallel light beams L enter the prism 5 and exit the prism 5.

[0129] In this way, the prism 5C makes it possible to adjust the beam spacing, shape, and filling rate. In particular, a single prism 5C can change the shape of the substantially parallel light L from an elliptical shape to one closer to a perfect circle, thereby narrowing the spacing of the substantially parallel light L in the first direction and improving the filling rate of the substantially parallel light L. This allows the optical system to be made more compact.

[0130] [1.4.2 Effects, etc.] The prism 5C described above satisfies β>α. This configuration can narrow the interval between beams (approximately parallel light L) with a simple structure, and further enables the beams (approximately parallel light L) to be made perfectly circular and the filling rate to be improved.

[0131] Prism 5C satisfies b2 / a2>b1 / a1. This configuration can not only reduce the beam spacing in the first direction but also improve the beam filling rate.

[0132] The prism 5C has a θ=sin －１ (n・sin(sin －１(sin α / n)+2(β-α))) and T α ・T θ ≧90%. This configuration can achieve high transmittance even when there are two refractions at different angles in the incident region R1 and the exit region R2.

[0133] The prism 5C satisfies γ-90<α<γ / 2. This configuration makes it possible to improve the reduction ratio and filling ratio of the substantially parallel light L in the first direction.

[0134] Prism 5C further satisfies 50<γ<100 and 1.1γ-90<α<0.95γ-60. This configuration enables further improvement in the reduction ratio and filling ratio of the substantially parallel light L in the first direction.

[0135] 18 is a schematic side view of a light source device 1D according to a fifth embodiment, particularly as viewed from the -Y direction. The light source device 1D includes a plurality of laser light sources 2 and an optical system 3D. The optical system 3D includes a plurality of collimating means 4 and a prism 5D.

[0136] Prism 5D has a first surface 51 and a second surface 52, similar to prism 5, but differs from prism 5 mainly in refractive index n, angle α, angle β, angle γ, and thickness d.

[0137] Table 8 below shows an example of parameters of the light source device 1D according to this embodiment.

[0138]

[0139] Prism 5D compresses the beam width of the substantially parallel light L in the first direction. The beam width of the substantially parallel light L in the first direction is larger than the beam width in the second direction. Therefore, by compressing the beam width of the substantially parallel light L in the first direction, the substantially parallel light L changes from an elliptical shape to a shape closer to a perfect circle. Furthermore, prism 5D makes it possible to improve the filling rate of the substantially parallel light L in the first direction.

[0140] In consideration of the light utilization efficiency of the prism 5D, an anti-reflection film is formed on the first surface 51. When the laser light source 2 is a general semiconductor laser, the beam B is linearly polarized light. The transmittance T of the incident region R1 for a predetermined linearly polarized light is α, the transmittance T of the output region R2 for a predetermined linearly polarized light θ Then, it is preferable that an anti-reflection coating is formed on the first surface 51 so as to satisfy the above formula (7). In this embodiment, the beam B is P-polarized in the major axis direction and S-polarized in the minor axis direction. In this embodiment, the first direction of the approximately parallel light L corresponds to the major axis direction of the beam B. Therefore, in the first direction of the approximately parallel light L, the transmittance for P-polarized light is taken into consideration. In other words, the specified linearly polarized light is P-polarized.

[0141] 19 is a graph showing the transmittance of the first surface 51 of the prism 5D for P-polarized light. G51 is the transmittance T α G52 indicates the change in transmittance T θ The change in transmittance T α indicates the transmittance for light incident on the first surface 51 at an angle α (=10°). θ indicates the transmittance for light incident on the first surface 51 at an angle equal to the refraction angle θ (=80°).

[0142] The reference wavelength of the prism 5D and the anti-reflection coating is 635 nm. The material of the prism 5D is glass, and the refractive index for the reference wavelength is 1.456954. The anti-reflection coating of the prism 5D is a multilayer coating in which layers made of materials with different refractive indices for the reference wavelength are alternately stacked. Table 9 below shows the configuration of the anti-reflection coating.

[0143]

[0144] From G51 and G52, in the anti-reflection film having the configuration of Table 9, in the wavelength range of W41 to W42 including the reference wavelength, T α ・T θ ≧90%. W41 is 629 nm, and W42 is 654 nm. Therefore, in the case of the antireflection film having the configuration in Table 9, even if light passes through the first surface 51 of the prism 5D twice, the total transmittance (=T α ・T θ ) can ensure a high transmittance of 90% or more.

[0145] In this way, the prism 5D makes it possible to adjust the beam spacing, shape, and fill factor. In particular, a single prism 5D can change the shape of the substantially parallel light L from an elliptical shape to one closer to a perfect circle, thereby narrowing the spacing of the substantially parallel light L in the first direction and improving the fill factor of the substantially parallel light L. This allows the optical system to be made more compact.

[0146] [1.5.2 Effects, etc.] The prism 5D described above satisfies β>α. This configuration can narrow the interval between beams (approximately parallel light L) with a simple structure, and further enables the beams (approximately parallel light L) to be made perfectly circular and the filling rate to be improved.

[0147] The prism 5D satisfies b2 / a2>b1 / a1. This configuration can not only reduce the beam spacing in the first direction but also improve the beam filling rate.

[0148] In the prism 5D, when the refractive index of the prism 5D is n and the refraction angle of the plurality of substantially parallel light beams L with respect to the emission region R2 is θ [°], θ=sin －１ (n・sin(sin －１ (sin α / n)+2(β-α))) The transmittance T for a predetermined straight line (P-polarized light) in the incident region R1 is α [%], transmittance T for a predetermined straight line (P-polarized light) in the exit region R2 θ [%], T α ・T θ ≧90%. This configuration can achieve high transmittance even when there are two refractions at different angles in the incident region R1 and the exit region R2.

[0149] The prism 5D satisfies γ-90<α<γ / 2. This configuration makes it possible to improve the reduction ratio and filling ratio of the substantially parallel light L in the first direction.

[0150] Prism 5D further satisfies 50<γ<100 and 1.1γ-90<α<0.95γ-60. This configuration enables further improvement in the reduction ratio and filling ratio of the substantially parallel light L in the first direction.

[0151] 20 is a schematic side view of a light source device 1E according to a sixth embodiment, particularly as viewed from the -Y direction. The light source device 1E includes a plurality of laser light sources 2 and an optical system 3E. The optical system 3E includes a plurality of collimating means 4 and a prism 5E.

[0152] The prism 5E has a first surface 51 and a second surface 52, similar to the prism 5, but differs from the prism 5 mainly in the refractive index n, the angles α, β, γ, and the thickness d.

[0153] Table 10 below shows an example of parameters of the light source device 1E according to this embodiment.

[0154]

[0155] In the prism 5E, the rate of change of the substantially parallel light L in the first direction is 222%, which exceeds 100%. Therefore, the prism 5E expands the beam width of the substantially parallel light L in the first direction. In the substantially parallel light L, the beam width in the first direction is smaller than the beam width in the second direction. Therefore, by expanding the beam width of the substantially parallel light in the first direction, the substantially parallel light L changes from an elliptical shape to one closer to a perfect circle. Furthermore, the prism 5E makes it possible to reduce the filling rate of the substantially parallel light L in the first direction.

[0156] 21 is a graph showing the transmittance of the first surface 51 of the prism 5E for S-polarized light. G61 is the transmittance T α G62 represents the change in transmittance T θ The change in transmittance T α indicates the transmittance for light incident on the first surface 51 at an angle α (=70°). θ indicates the transmittance for light incident on the first surface 51 at an angle equal to the refraction angle θ (=20°).

[0157] The reference wavelength of the prism 5E and the anti-reflection coating is 455 nm. The material of the prism 5E is glass, and the refractive index for the reference wavelength is 1.524396. The anti-reflection coating of the prism 5E is a multilayer coating in which layers made of materials with different refractive indices for the reference wavelength are alternately stacked. Table 11 below shows the configuration of the anti-reflection coating.

[0158]

[0159] From G61 and G62, the anti-reflection coating having the configuration of Table 11 shows that in the wavelength range of W51 to W52 including the reference wavelength, T α ・T θ ≧90%. W51 is 424 nm, and W52 is 502 nm. Therefore, in the case of the antireflection film having the configuration of Table 11, even if light passes through the first surface 51 of the prism 5E twice, the total transmittance (=T α ・T θ ) can ensure a high transmittance of 90% or more.

[0160] In this way, the prism 5E makes it possible to adjust the beam spacing, shape, and fill factor. In particular, a single prism 5E can change the substantially parallel light L from an elliptical shape to one closer to a perfect circle, widen the spacing between the substantially parallel light L in the first direction, and reduce the fill factor of the substantially parallel light L. This allows for a more compact optical system. For example, in cases where it is desired to separate the beams B from the individual laser light sources 2 for various purposes, or where the density of the laser light sources 2 is too high, the prism 5E can widen the distance between the beams B while correcting the shape of the beams B, making it easier to configure the optical system.

[0161] [1.6.2 Effects, etc.] In the prism 5E described above, when the angle of the incident region R1 and the exit region R2 with respect to the first direction is α [°] and the angle of the reflective region R3 is β [°], the relationship β < α is satisfied. This configuration can widen the spacing between the beams (approximately parallel light L) with a simple structure, and further enables the circularity of the beams (approximately parallel light L) to be improved and the filling rate to be reduced.

[0162] [2. Modifications] The embodiments of the present disclosure are not limited to the above-described embodiments. The above-described embodiments can be modified in various ways depending on the design, etc., as long as the object of the present disclosure can be achieved. Modifications of the above-described embodiments are listed below. The modifications described below can be applied in appropriate combinations.

[0163] In the following, reference will be made to the symbols used in embodiment 1, even though they are applicable to any of the above embodiments 1 to 6. However, this is merely to simplify the description and is not intended to exclude application to embodiments 2 to 6.

[0164] 22 is a partial front view of the prism 5 according to the first embodiment. In the prism 5, the substantially parallel light beam L is refracted at the entrance region R1 of the first surface 51 and enters the prism 5. Inside the prism 5, it is reflected at the reflection region R3 of the second surface 52, and refracted at the exit region R2 of the first surface 51 before exiting the prism 5. The prism 5 has portions that have very little effect on the refraction and reflection of the substantially parallel light beams L. In particular, portions of the second surface 52 other than the reflection region R3, primarily the second inclined surface 52b and the boundary between the second inclined surface 52b and the first inclined surface 52a, have very little effect on the reflection of the substantially parallel light beam L. Depending on the position of the reflection region R3, the peripheral edge of the substantially parallel light beam L may be present at the second inclined surface 52b and the boundary between the second inclined surface 52b and the first inclined surface 52a. However, the peripheral edge of the substantially parallel light beam L is a portion where the radiation intensity of a semiconductor laser, which typically has a Gaussian distribution, is almost nonexistent. Therefore, the portions other than the reflective region R3, such as the second inclined surface 52 b and the boundary between the second inclined surface 52 b and the first inclined surface 52 a, are ineffective portions R4 that have very little effect on the light utilization efficiency. Therefore, the shape of such ineffective portions R4 may be any shape.

[0165] FIG. 23 is a partial front view of a prism 5 according to a modified example. In FIG. 23, the second inclined surface 52b of the second surface 52 is a surface along the ±Z direction. FIG. 24 is a partial front view of a prism 5 according to another modified example. In FIG. 24, the ridge line between the first inclined surface 52a and the second inclined surface 52b of the second surface 52 is rounded. The prism 5 can be manufactured by polishing, glass molding, resin molding, or the like. When manufacturing the prism 5 by glass molding, the shape of FIG. 22 or FIG. 240 has a smaller aspect ratio than the shape of FIG. 23, and is therefore preferable because it is easier to suppress shape deformation during molding and allows for easy removal from the mold.

[0166] The ineffective portion R4 of the prism 5 is not limited to the shapes shown in FIGS. 22 to 24, and may be set to a shape suitable for the manufacturing method of the prism 5 by using the degree of freedom of the ineffective portion R4.

[0167] In one modified example, the plurality of laser light sources 2 may be individually mounted in a can package, or may be integrated.

[0168] In one variant, the plurality of collimating means 4 may be integrated into one optical component. The plurality of collimating means 4 may be provided as a light source unit together with the plurality of laser light sources 2. In this case, the optical system 3 does not need to include the plurality of collimating means 4.

[0169] In one modified example, the first surface 51 may not be a flat surface but may be a stepped surface like the second surface 52. In this case, the incident region R1 and the exit region R2 may not be located on the same plane in the first direction. The incident region R1 or the exit region R2 may be arranged so as not to be located on the same plane in the first direction. Note that when the first surface 51 is a stepped surface like the second surface 52, the second surface 52 may be a flat surface.

[0170] In one modified example, a reflective film may be formed on the second surface 52 of the prism 5, particularly on the first inclined surface 52a. The reflective film may be a dielectric multilayer film or a metal coating film, as long as it has high reflectivity in a desired wavelength range that includes the wavelength of the substantially parallel light L.

[0171] In one variant, the optical system 3 may not include the group of reflecting mirrors 6. On the other hand, the optical systems 3A, 3B, 3C, 3D, and 3E may include the group of reflecting mirrors 6.

[0172] [3. Aspects] As is clear from the above-described embodiment and modifications, the present disclosure includes the following aspects.

[0173] [Aspect 1] A prism having a first surface onto which a plurality of substantially parallel light beams are incident from a plurality of collimating means that convert a plurality of beams emitted from a plurality of laser light sources into a plurality of substantially parallel light beams, and a second surface opposite the first surface, wherein each of the plurality of substantially parallel light beams incident on the prism has a beam width in a first direction greater than a beam width in a second direction perpendicular to the first direction, and the plurality of substantially parallel light beams incident on the prism are aligned at least in the first direction, and for each of the plurality of substantially parallel light beams, the first surface includes an entrance region where the substantially parallel light beam is refracted to enter the prism and an exit region where the substantially parallel light beam is refracted to exit the prism, and the second surface includes a reflection region that reflects the substantially parallel light that entered the prism through the entrance region toward the exit region.

[0174] [Aspect 2] The prism of Aspect 1, wherein, when the angle of the incident area and the exit area with respect to the first direction is α [°] and the angle of the reflection area is β [°], the following relationship is satisfied: β≠α.

[0175] [Embodiment 3] The prism of embodiment 2, which satisfies β>α.

[0176] [Aspect 4] The prism of Aspect 3, wherein b2 / a2>b1 / a1 is satisfied, where a1 is the interval in the first direction between the plurality of substantially parallel light beams incident on the prism, b1 is the beam width in the first direction, a2 is the interval in a third direction corresponding to the first direction between the plurality of substantially parallel light beams emitted from the prism, and b2 is the beam width in the third direction.

[0177] [Embodiment 5] The prism of embodiment 2, which satisfies β<α.

[0178] [Aspect 6] When the refractive index of the prism is n and the refraction angle of the plurality of substantially parallel beams with respect to the emission region is θ [°], θ=sin －１ (n・sin(sin －１ (sin α / n)+2(β−α))), and the transmittance T α [%], the transmittance T of the output region for the predetermined linearly polarized light θ If it is expressed as [%], T α・T θ 6. The prism according to any one of Aspects 1 to 5, wherein the prism satisfies the condition ≧90%.

[0179] [Aspect 7] The prism according to any one of Aspects 1 to 6, wherein the entrance region and the exit region are located on the same plane in the first direction.

[0180] [Aspect 8] The prism according to any one of Aspects 1 to 7, wherein the reflective regions are arranged so as not to be located on the same plane in the first direction.

[0181] [Aspect 9] The prism of aspect 8, wherein the distance between the center of the incident region and the center of the reflecting region is equal, and the distance between the center of the exit region and the center of the reflecting region is equal, for each of the plurality of substantially parallel beams of light.

[0182] [Aspect 10] The prism according to any one of Aspects 1 to 9, wherein |2t / s|<0.3 is satisfied, where s [mm] is the distance on the first surface between the centers of the incident regions of adjacent substantially parallel light beams in the first direction among the plurality of substantially parallel light beams, and t [mm] is the distance on the first surface between the midpoint between the centers and the exit region of the adjacent substantially parallel light beams that is closest to the midpoint.

[0183] [Embodiment 11] The prism of embodiment 10, wherein t=0 is satisfied.

[0184] [Aspect 12] The prism according to any one of Aspects 1 to 11, wherein the angle of the optical axes of the plurality of substantially parallel light beams exiting the prism relative to the optical axes of the plurality of substantially parallel light beams incident on the prism is γ [°], and the following relationship is satisfied: γ - 90 < α < γ / 2.

[0185] [Embodiment 13] The prism of embodiment 12, further satisfying 50<γ<100, and 1.1γ-90<α<0.95γ-60.

[0186] [Aspect 14] A light source device comprising: a plurality of laser light sources; a plurality of collimating means for converting a plurality of beams emitted from the plurality of laser light sources into a plurality of substantially parallel beams; and a prism having a first surface onto which the plurality of substantially parallel beams are incident from the plurality of collimating means and a second surface opposite the first surface, wherein each of the plurality of substantially parallel beams incident on the prism has a larger beam width in a first direction than a beam width in a second direction perpendicular to the first direction, and the plurality of substantially parallel beams incident on the prism are aligned at least in the first direction, and for each of the plurality of substantially parallel beams, the first surface includes an entrance region where the substantially parallel beam is refracted to enter the prism and an exit region where the substantially parallel beam is refracted to exit the prism, and the second surface includes a reflection region that reflects the substantially parallel beam that entered the prism through the entrance region toward the exit region.

[0187] [Aspect 15] The light source device of Aspect 14, wherein the plurality of substantially parallel beams are aligned in both the first direction and the second direction.

[0188] [Aspect 16] The light source device of Aspect 15, further comprising a group of reflecting mirrors that reflect the plurality of substantially parallel beams of light emitted from the prism, the group of reflecting mirrors including a plurality of reflecting mirrors arranged such that the spacing in the second direction of the plurality of substantially parallel beams of light after being reflected by the group of reflecting mirrors is smaller than the spacing in the second direction of the plurality of substantially parallel beams of light before being reflected by the group of reflecting mirrors.

[0189] Aspects 2 to 13, 15, and 16 are optional elements and are not essential. Aspects 2 to 13 can be appropriately combined with Aspects 14 to 16.

[0190] The present disclosure is applicable to a prism and a light source device, specifically to a prism for integrating beams from a plurality of laser light sources, and a light source device including the prism.

[0191] 1, 1A, 1B, 1C, 1D, 1E Light source device 2 Ray light source 3, 3A, 3B, 3C, 3D, 3E Optical system 4 Correlation means 5, 5A, 5B, 5C, 5D, 5E Filter 51 1st surface 52 2nd surface R1 Incident area R2 Outgoing area R3 Reflection area 6 Reflection mirror group 6a Reflection mirror L Substantially parallel light

Claims

1. A prism, a first surface onto which a plurality of substantially parallel light beams are incident, the beam width in the first direction being greater than the beam width in a second direction orthogonal to the first direction; a second surface opposite to the first surface; and the first surface includes a plurality of entrance regions where the plurality of substantially parallel light beams are refracted and enter the prism, and a plurality of exit regions where the plurality of substantially parallel light beams are refracted and exit the prism, the second surface includes a plurality of reflective regions that reflect the plurality of substantially parallel light beams that have passed through the plurality of incident regions and entered the prism toward the plurality of exit regions; prism.

2. The plurality of incident regions and the plurality of exit regions are located on the same plane of the first surface, the plurality of reflective regions are located on a plurality of inclined surfaces inclined with respect to the first surface within the second surface, The plurality of inclined surfaces are parallel to each other and arranged in a stepped pattern. The prism of claim 1.

3. When the angle of the incident area and the emission area with respect to the first direction is α [°] and the angle of the reflection area is β [°], β>α is satisfied. The prism of claim 2.

4. Let a1 be the interval between the plurality of substantially parallel beams incident on the prism in the first direction, b1 be the beam width in the first direction, a2 be the interval between the plurality of substantially parallel beams emitted from the prism in a third direction corresponding to the first direction, and b2 be the beam width in the third direction. b2 / a2>b1 / a1 is satisfied. The prism of claim 3.

5. When the angle of the incident area and the emission area with respect to the first direction is α [°] and the angle of the reflection area is β [°], β < α is satisfied. The prism of claim 2.

6. When the refractive index of the prism is n and the refraction angle of the plurality of substantially parallel beams with respect to the emission region is θ [°], θ=sin －１ (n・sin(sin －１ (sina / n) + 2 (β-α)) Fulfilling The transmittance T of the incident region for a predetermined linearly polarized light α [%], the transmittance T of the output region for the predetermined linearly polarized light θ If expressed as [%], T α ・T θ ≧90% fulfill, The prism of claim 2.

7. the incident region and the exit region are located on the same plane in the first direction; The prism of claim 1.

8. the reflective areas are arranged so as not to be located on the same plane in the first direction; The prism of claim 1.

9. For each of the plurality of substantially parallel beams of light, the distance between the center of the incident region and the center of the reflective region is equal, and the distance between the center of the exit region and the center of the reflective region is equal. The prism of claim 6.

10. The distance on the first surface between the centers of the incident regions of adjacent substantially parallel light beams in the first direction among the plurality of substantially parallel light beams is s [mm]; The distance on the first surface between the midpoint between the centers and the exit region closest to the midpoint among the exit regions of the adjacent substantially parallel light beams is t [mm]; Then, |2t / s|<0.3 fulfill, The prism of claim 2.

11. t=0 fulfill, The prism of claim 10.

12. When the angle of the optical axes of the plurality of substantially parallel light beams exiting the prism with respect to the optical axes of the plurality of substantially parallel light beams incident on the prism is γ [°], γ-90<α<γ / 2 fulfill, The prism of claim 2.

13. 50<γ<100, and 1.1γ-90<α<0.95γ-60 Further satisfying The prism of claim 12.

14. a plurality of laser light sources; a plurality of collimating means for converting the plurality of beams emitted from the plurality of laser light sources into a plurality of substantially parallel beams; a prism having a first surface onto which the plurality of substantially parallel light beams from the plurality of collimating means are incident and a second surface opposite to the first surface; Equipped with In each of the plurality of substantially parallel beams incident on the prism, a beam width in a first direction is larger than a beam width in a second direction perpendicular to the first direction, the plurality of substantially parallel light beams incident on the prism are aligned at least in the first direction, the first surface includes a plurality of entrance regions where the plurality of substantially parallel light beams are refracted and enter the prism, and a plurality of exit regions where the plurality of substantially parallel light beams are refracted and exit the prism, the second surface includes a plurality of reflective regions that reflect the plurality of substantially parallel light beams that have passed through the plurality of incident regions and entered the prism toward the plurality of exit regions; Light source device.

15. The plurality of incident regions and the plurality of exit regions are located on the same plane of the first surface, the plurality of reflective regions are located on a plurality of inclined surfaces inclined with respect to the first surface within the second surface, The plurality of inclined surfaces are parallel to each other and arranged in a stepped pattern. The light source device of claim 14.

16. the plurality of substantially parallel light beams incident on the prism are aligned in both the first direction and the second direction; The light source device of claim 15.

17. a group of reflecting mirrors that reflect the plurality of substantially parallel light beams emitted from the prism; the reflection mirror group includes a plurality of reflection mirrors arranged such that an interval in the second direction between the plurality of substantially parallel beams of light after being reflected by the reflection mirror group is smaller than an interval in the second direction between the plurality of substantially parallel beams of light before being reflected by the reflection mirror group, The light source device of claim 16.