JP7735720B2 - Light source optical system, light source unit, light source device and image display device - Google Patents

Description

The present invention relates to a light source optical system, a light source unit, a light source device, and an image display device.

Projectors (image display devices, image projection devices) that enlarge and project images are widely used. A projector focuses light emitted from a light source onto an image display element (spatial light modulation element) such as a digital micromirror device (DMD) or liquid crystal display element, and then displays the light emitted from the image display element modulated by a video signal as a color image on a screen, which is the projection surface.

Traditionally, high-intensity ultra-high pressure mercury lamps have been the main light source used in projectors, but they have a short lifespan and require frequent maintenance. For this reason, in recent years, an increasing number of projectors have been using lasers or LEDs as light sources instead of ultra-high pressure mercury lamps. Lasers and LEDs have the advantage of a longer lifespan than ultra-high pressure mercury lamps, and their monochromaticity allows for better color reproduction.

For example, when forming an image by irradiating an image display element with the three primary colors of red, green, and blue, it is possible to generate all three colors using a laser light source, but the problem is that the light-emitting efficiency of green and red lasers is lower than that of blue lasers. For this reason, a method is used in which a blue laser is used as excitation light to irradiate a phosphor, and red and green light are generated from the fluorescent light that has been wavelength-converted by the phosphor. Light source devices using such laser light sources and phosphors are disclosed in Patent Documents 1 and 2, among others.

Patent No. 6090875 Patent No. 6364916

This type of light source device is required to have as uniform an illuminance distribution on the illuminated surface as possible. However, the light source optical system in conventional light source devices leaves room for improvement in terms of uneven illuminance distribution on the illuminated surface.

In particular, with projectors, the illuminance distribution on the image display element, which is the surface illuminated by light from the light source optical system, can affect the illuminance distribution on the screen. Furthermore, in addition to the light source optical system, the projection optical system and other components also affect the illuminance distribution. In other words, the uneven illuminance on the screen, which is an issue with projectors, can be caused either by the light source device or by the projection optical system, which is located before the light source device. For example, in ultra-short-focus projectors that include a folding mirror in the projection optical system, the angle of incidence of the projected light on the screen varies greatly depending on the vertical height, making it easy for illuminance unevenness to occur above and below the screen.

The present invention was developed based on the above-mentioned awareness, and aims to provide a light source optical system, a light source unit, a light source device, and an image display device that can improve illuminance distribution with a simple configuration.

According to an aspect of the present invention, there is provided a light source optical system including a first optical system that causes a first light beam emitted from a light source to be incident on a wavelength conversion element, and a second optical system through which a second light beam wavelength-converted by the wavelength conversion element passes, the second optical system including a light guide member that separates a portion of the second light beam within the second optical system. The light guide member has a plane-parallel plate shape, and when viewed from the wavelength conversion element side along an optical axis of the second optical system, the light guide member has a first surface having a large projected area, a second surface having a small projected area, a third surface opposite the first surface, and a fourth surface opposite the second surface. The portion of the second light beam to be separated enters the second surface, is totally reflected multiple times by the first surface and the third surface inside the light guide member, and is then emitted from the fourth surface. When viewed along the optical axis of the second optical system, both the second surface and the fourth surface are located within a range of an optical path through which the second light beam passes.

In one aspect of the light source unit of the present invention, a first light beam emitted from a light source is incident on a wavelength conversion element by a first optical system, a second light beam wavelength-converted by the wavelength conversion element is emitted through a second optical system, and the second optical system includes a light guide member arranged in the second optical system to separate a portion of the second light beam within the second optical system. The light guide member has a plane-parallel plate shape, and when viewed from the wavelength conversion element side along an optical axis of the second optical system, the light guide member has a first surface having a large projected area, a second surface having a small projected area, a third surface opposite the first surface, and a fourth surface opposite the second surface. A portion of the separated second light beam enters the second surface, is totally reflected multiple times by the first surface and the third surface inside the light guide member, and is then emitted from the fourth surface. When viewed along the optical axis of the second optical system, both the second surface and the fourth surface are located within a range of an optical path through which the second light beam passes.

According to an aspect of the present invention, there is provided a light source device including a light source, a first optical system that causes a first light beam emitted from the light source to be incident on a wavelength conversion element, and a second optical system through which a second light beam wavelength-converted by the wavelength conversion element passes, the second optical system including a light guide member that separates a portion of the second light beam within the second optical system. The light guide member has a plane-parallel plate shape, and when viewed from the wavelength conversion element side along an optical axis of the second optical system, the light guide member has a first surface having a large projected area, a second surface having a small projected area, a third surface opposite to the first surface, and a fourth surface opposite to the second surface. The portion of the second light beam to be separated enters the second surface, is totally reflected multiple times by the first surface and the third surface inside the light guide member, and is then emitted from the fourth surface. When viewed along the optical axis of the second optical system, both the second surface and the fourth surface are located within a range of an optical path through which the second light beam passes.

An aspect of the image display device of the present invention has a light source device including a first optical system that forms an optical path along which a first light beam passes from a light source to a wavelength conversion element, and a second optical system that forms an optical path along which a second light beam that has been wavelength converted by the wavelength conversion element passes , an image display element that modulates light from the light source device to form an image, and a projection optical system that projects the image onto a projection surface, and a light-guiding member within the second optical system that separates a portion of the second light beam within the second optical system. The light-guiding member has a parallel plane plate shape, and has a first surface with a large projected area, a second surface with a small projected area, a third surface opposite to the first surface, and a fourth surface opposite to the second surface when viewed from the wavelength conversion element side along the optical axis of the second optical system, and a part of the separated second light beam is incident on the second surface, is totally reflected multiple times by the first surface and the third surface inside the light-guiding member, and is emitted from the fourth surface, and when viewed along the optical axis of the second optical system, both the second surface and the fourth surface are located within the range of the optical path through which the second light beam passes.

The light source optical system, light source unit, light source device, and image display device of the present invention can improve illuminance distribution with a simple configuration.

FIG. 1 is a schematic diagram illustrating the configuration of a projector (image display device). 1 is a schematic configuration diagram showing a light source device according to a first embodiment. 1A and 1B are diagrams showing the structure of a phosphor wheel that constitutes a light source device, in which FIG. 1A is a front view and FIG. 1B is a cross-sectional view. 4 is a side cross-sectional view showing the arrangement and function of the light guide member of the first embodiment. FIG. FIG. 2 is a front view showing the arrangement of the light guide member according to the first embodiment. 5A and 5B are diagrams illustrating an improvement in illuminance distribution achieved by the light source device of the first embodiment. FIG. 10 is a schematic configuration diagram showing a light source device according to a second embodiment. 10A and 10B are side cross-sectional views showing the arrangement and function of a light guide member according to a second embodiment. FIG. 10 is a front view showing the arrangement of the light guide member according to the second embodiment. 10A and 10B are diagrams illustrating the results of improving the illuminance distribution by the light source device of the second embodiment. FIG. 11 is a front view showing the arrangement of a light guide member in a light source device according to a third embodiment. FIG. 10 is a schematic configuration diagram showing a light source device according to a fourth embodiment. 10A and 10B are side cross-sectional views showing the arrangement and function of a light guide member according to a fourth embodiment. FIG. 10 is a front view showing the arrangement of the light guide member according to the fourth embodiment. 10A and 10B are diagrams illustrating the results of improving the illuminance distribution by the light source device of the fourth embodiment. FIG. 10 is a schematic configuration diagram showing a light source device according to a fifth embodiment.

Embodiments of the present invention will now be described with reference to the drawings. Fig. 1 shows the overall structure of a projector, which is an example of an image display device. Figures 2 and onward show embodiments of the light source device (light source optical system) that constitutes the projector, with Figs. 2 to 6 showing the first embodiment, Figs. 7 to 10 showing the second embodiment, Fig. 11 showing the third embodiment, Figs. 12 to 15 showing the fourth embodiment, and Fig. 16 showing the fifth embodiment.

The projector 10 shown in FIG. 1 has a housing 11, a light source device (light source unit) 12, a light homogenizing element 13, an illumination optical system 14, an image display element 15, and a projection optical system 16. Each component from the light source device 12 to the projection optical system 16 is housed inside the housing 11.

The light source device 12 emits light containing wavelengths corresponding to the colors red (R), green (G), and blue (B), for example. The internal configuration of the light source device 12 will be described in detail later.

The light homogenizing element 13 homogenizes the light emitted from the light source device 12 by mixing it. Examples of light homogenizing elements 13 include a light tunnel made up of four mirrors, a rod integrator made of cylindrical glass, and a fly's eye lens made up of multiple lenses arranged in a matrix.

The illumination optical system 14 illuminates the image display element 15 approximately uniformly with light homogenized by the light homogenizing element 13. The illumination optical system 14 includes, for example, one or more lenses and one or more reflective surfaces.

The image display element 15 has a light valve, such as a digital micromirror device (DMD), a transmissive liquid crystal panel, or a reflective liquid crystal panel. The image display element 15 forms an image by modulating the light illuminated by the illumination optical system 14 (light from the light source device 12).

The projection optical system 16 enlarges and projects the image formed by the image display element 15 onto a screen (projection surface) 17 outside the projector 10. The projection optical system 16 has, for example, one or more lenses.

Figure 2 is a schematic diagram showing the configuration of a light source device 12 according to the first embodiment. The light source device 12 includes, arranged in order in the light propagation direction, a laser light source (light source) 20, a collimator lens 21, a first lens group 22, a light-guiding member 23, a quarter-wave plate 24, a second lens group 25, a phosphor wheel (wavelength conversion element) 26, a third lens group 27, and a color wheel 28. For example, the light source optical system is configured by the components (optical elements) of the light source device 12 excluding the laser light source 20.

The laser light source 20 has multiple light sources (solid-state light sources). In Figure 2, six light sources are depicted lined up vertically on the drawing, but in reality, the six light sources are lined up in n rows (n is a number greater than or equal to 2) in the direction perpendicular to the plane of the paper (depth direction), with 6 x n light sources arranged in a two-dimensional array. The number of multiple laser light sources 20 can be set arbitrarily. It is also possible to use a single high-output laser light source instead of multiple laser light sources 20.

The multiple laser light sources 20 can be configured, for example, as a light source unit in which multiple light sources are arranged in an array on a substrate, but there is a degree of freedom in the specific form. Hereinafter, multiple light sources arranged in a two-dimensional array may be referred to as "multiple laser light sources 20."

The multiple laser light sources 20 emit, for example, light in the blue band (blue laser light) with a central wavelength of 455 nm in emission intensity as excitation light BL (first colored light) to excite the phosphors provided in the fluorescent region 26d (Figure 3), which is the wavelength conversion region of the phosphor wheel 26. The blue laser light emitted from the multiple laser light sources 20 is linearly polarized with a constant polarization state and is arranged so as to be S-polarized with respect to the incident surface of the light-guiding member 23 (surface 23a, described below). The blue laser light emitted from the multiple laser light sources 20 is coherent light. Note that the excitation light BL emitted from the multiple laser light sources 20 may be light of a wavelength capable of exciting the phosphors in the fluorescent region 26d of the phosphor wheel 26, and is not limited to light in the blue band.

A plurality of collimator lenses 21 are arranged in a two-dimensional array corresponding to the plurality of laser light sources 20. The plurality of collimator lenses 21 adjust the light beams (excitation light BL) emitted from the plurality of laser light sources 20 so that they become parallel or convergent light. The number of collimator lenses 21 only needs to correspond to the number of light sources of the laser light source 20, and can be increased or decreased according to an increase or decrease in the number of light sources of the laser light source 20.

The first lens group 22 has positive power overall, and includes a positive lens 22a and a negative lens 22b in that order in the direction of light propagation from the laser light source 20 toward the phosphor wheel 26. The first lens group 22 converges the excitation light BL that has entered as parallel or convergent light from the collimator lens 21 and guides it to the light-guiding member 23. Note that the first lens group 22 may have negative power instead of positive power.

The light-guiding member 23 is located on the optical path between the first lens group 22 and the second lens group 25. The light-guiding member 23 is a flat (plate-type) polarized beam splitter that is coated to reflect S-polarized light (first polarization component) in the wavelength band of the excitation light BL guided from the first lens group 22, while transmitting P-polarized light (second polarization component) in the wavelength band of the excitation light BL and the fluorescent light YL (second colored light) from the phosphor wheel 26.

In this embodiment, the light-guiding member 23 reflects S-polarized light in the wavelength band of the excitation light BL and transmits P-polarized light, but conversely, it may also reflect P-polarized light in the wavelength band of the excitation light BL and transmit S-polarized light.

The quarter-wave plate 24 is positioned with its optical axis tilted 45 degrees with respect to the linearly polarized light of the excitation light BL reflected by the light-guiding member 23. The quarter-wave plate 24 converts the excitation light BL reflected by the light-guiding member 23 from linearly polarized light to circularly polarized light.

The second lens group 25 has positive power overall and includes a positive lens 25a and a positive lens 25b in the direction of light propagation from the laser light source 20 toward the phosphor wheel 26. The second lens group 25 converges the excitation light BL that has been converted into circularly polarized light by the quarter-wave plate 24 and is incident thereon, and guides it to the phosphor wheel 26.

Excitation light BL guided from the second lens group 25 is incident on the phosphor wheel 26. Figure 3 shows the detailed structure of the phosphor wheel 26. The phosphor wheel 26 has a disk member 26a and a drive motor 26c that rotates the disk member 26a around a rotation axis 26b. The disk member 26a can be, for example, a transparent substrate or a metal substrate (such as an aluminum substrate), but is not limited to these.

The majority of the circumference of the disk member 26a of the phosphor wheel 26 (an angular range greater than 270° in this embodiment) is defined as a fluorescent region 26d, and a portion of the circumference excluding the range of the fluorescent region 26d (an angular range less than 90° in this embodiment) is defined as an excitation light reflection region 26e.

The fluorescent region 26d is composed of a reflective coating 26d1, a phosphor layer 26d2, and an anti-reflection coating 26d3 layered from bottom to top.

The reflective coating 26d1 has the property of reflecting light in the wavelength range of the fluorescent light YL emitted by the phosphor layer 26d2. If the disk member 26a is made of a metal substrate with high reflectivity, it is possible to omit the reflective coating 26d1 (by having the disk member 26a function as the reflective coating 26d1).

The phosphor layer 26d2 can be, for example, a phosphor material dispersed in an organic or inorganic binder, a directly formed crystal of a phosphor material, or a rare earth phosphor such as Ce:YAG. The wavelength band of the fluorescent light YL emitted by the phosphor layer 26dd2 can be, for example, yellow, blue, green, or red. In this embodiment, however, fluorescent light YL having a yellow wavelength band is used. Furthermore, although a phosphor is used as the wavelength conversion element in this embodiment, a phosphor, a nonlinear optical crystal, or the like may also be used.

The anti-reflection coating 26d3 has the property of preventing light reflection on the surface of the phosphor layer 26d2.

A reflective coating 26e1 is laminated on the excitation light reflection region 26e, and has the property of reflecting light in the wavelength range of the excitation light BL guided from the second lens group 25. If the disk member 26a is made of a metal substrate with high reflectivity, it is possible to omit the reflective coating 26e1 (i.e., the disk member 26a can be given the function of the reflective coating 26e1).

By rotating the disk member 26a using the drive motor 26c, the irradiation position of the excitation light BL on the phosphor wheel 26 moves over time. As a result, the excitation light BL incident on the phosphor wheel 26 is time-shared between a state in which it is converted into fluorescent light YL, which has a different wavelength from the excitation light BL, by the fluorescent region 26d and then emitted, and a state in which it is reflected as excitation light BL by the excitation light reflection region 26e and emitted.

The number and range of fluorescent regions 26d and excitation light reflecting regions 26e can be freely determined, allowing for various design modifications. For example, two fluorescent regions and two excitation light reflecting regions may be alternately arranged at 90° intervals around the circumference.

The light source device 12 will now be described again with reference to Figure 2. The excitation light BL reflected by the excitation light reflection region 26e of the phosphor wheel 26 becomes circularly polarized light in the reverse direction and travels from the phosphor wheel 26 toward the light-guiding member 23. The second lens group 25 converts the diffused light beam into a nearly parallel light beam, and the quarter-wave plate 24 converts it into P-polarized light. The P-polarized excitation light BL passes through the light-guiding member 23 and enters the color wheel 28 through the third lens group 27, which has a light-collecting effect. In this embodiment, the third lens group 27 is composed of a single lens.

The excitation light BL incident on the fluorescent region 26d of the phosphor wheel 26 is converted into fluorescent light YL and emitted. This fluorescent light YL is converted from a diffused beam into a nearly parallel beam by the second lens group 25, passes through the quarter-wave plate 24 and the light-guiding member 23, and enters the color wheel 28 through the third lens group 27.

The color wheel 28 has a disk member 28a and a drive motor 28c that rotates the disk member 28a around a rotation axis 28b. Although not shown, the disk member 28a has blue, yellow, red, and green regions that are partitioned circumferentially. The blue region corresponds to the excitation light reflection region 26e of the phosphor wheel 26, while the yellow, red, and green regions are synchronized to correspond to the fluorescent region 26d of the phosphor wheel 26. The yellow region transmits the yellow wavelength region emitted from the phosphor wheel 26 as is. The red and green regions each use a dichroic mirror to reflect unnecessary wavelengths from the yellow wavelength range, resulting in light of a highly pure color.

As shown in FIG. 1, the light of each color created in a time-division manner by the color wheel 28 is guided (irradiated) from the light uniformizing element 13 through the illumination optical system 14 to the image display element 15, where it forms an image corresponding to each color. The projection optical system 16 then enlarges and projects the image onto the screen 17, thereby producing a color image. That is, the image display element 15 modulates the light from the light source device 12 to form an image, and the projection optical system 16 enlarges and projects the image formed by the image display element 15 onto the screen 17.

In the light source optical system of the light source device 12 constituting the projector 10 described above, the first lens group 22 to the second lens group 25 form a first optical system for directing the first light beam emitted from the laser light source 20 onto the phosphor wheel 26 (forming an optical path through which the first light beam passes). Note that the collimator lens 21 may also be included in the first optical system.

In the light source optical system of the light source device 12, the second lens group 25 to the third lens group 27 form a second optical system through which the second light beam wavelength-converted by the phosphor wheel 26 passes (forming an optical path through which the second light beam passes). The optical axis LX and second light beam LF of the second optical system are shown in Figures 2, 4, and 5. Figure 5 is a front view of the light-guiding member 23 viewed along the optical axis LX from the phosphor wheel 26 side.

In the first optical system, the light-guiding member 23 functions as a reflecting element that reflects the first light beam incident from the first lens group 22 toward the phosphor wheel 26. In the second optical system, the light-guiding member 23 also functions as a light-guiding element that guides a portion of the second light beam traveling from the second lens group 25 toward the third lens group 27 and separates it within the second optical system. The configuration and function of the light-guiding member 23 are described below.

The light-guiding member 23 is a parallel-plane plate made of glass, transparent resin, or the like, and has a front surface 23a and a back surface 23b, which are parallel planes, on both sides. To enable the light-guiding member 23 to function as a polarizing beam splitter, a coating is formed on the front surface 23a side that reflects S-polarized light in the wavelength band of the excitation light BL and transmits P-polarized light in the wavelength band of the excitation light BL and fluorescent light YL.

The peripheral portion of the light-guiding member 23 is composed of a pair of parallel long-side end faces (first end faces) 23c and long-side end faces (second end faces) 23d extending in the longitudinal direction of the light-guiding member 23, and a pair of parallel short-side end faces 23e and short-side end faces 23f extending in the lateral direction of the light-guiding member 23. The long-side end faces 23c and 23d, and the short-side end faces 23e and 23f, are surfaces that are approximately perpendicular to the front surface 23a and the back surface 23b, respectively. The long-side end faces 23c and 23d are also surfaces that are approximately perpendicular to the short-side end faces 23e and 23f. The light-guiding member 23 is supported and fixed near the short-side end faces 23e and 23f by support means (not shown) outside the second light beam LF.

The direction in which the optical axis of the first lens group 22 extends is the M1 direction. The M1 direction is perpendicular to the optical axis LX of the second optical system. The light-guiding member 23 is arranged with its longitudinal direction oriented in the M2 direction, which is perpendicular to the M1 direction and the optical axis LX.

As shown in FIG. 4, the light-guiding member 23 is positioned so that the front surface 23a and back surface 23b form an intersection angle of approximately 45 degrees with the optical axis LX when viewed from the side in the M2 direction (the side of the short side end surface 23e or short side end surface 23f). In the direction along the optical axis LX, the front surface 23a is located on the phosphor wheel 26 (second lens group 25) side, and the back surface 23b is located on the color wheel 28 (third lens group 27) side.

5 , in a front view of light-guiding member 23 along optical axis LX, front surface 23a and long side end surface 23c face toward phosphor wheel 26. Front surface 23a, which has a larger projected area in this front view, is the first surface, long side end surface 23c, which has a smaller projected area, is the second surface, back surface 23b, which is the surface opposite front surface 23a, is the third surface, and long side end surface 23d, which is the surface opposite long side end surface 23c, is the fourth surface. The first light flux is reflected toward phosphor wheel 26 by front surface 23a, which is the first surface.

When the light-guiding member 23 is viewed from the rear along the optical axis LX from the opposite side to that shown in Figure 5, the rear surface 23b and the long side end surface 23d face toward the third lens group 27 (color wheel 28). The projected area of the rear surface 23b in rear view is larger than that of the long side end surface 23d.

The light-guiding member 23 is positioned so that the optical axis LX passes through the center of its outer shape in the front and rear views. More specifically, in the front view of the light-guiding member 23 shown in FIG. 5, the optical axis LX is located at the center of the short-side dimension from the long-side end face 23c to the long-side end face 23d, and the optical axis LX is located at the center of the long-side dimension from the short-side end face 23e to the short-side end face 23f. As shown in FIG. 5, if an imaginary plane S1 that includes the optical axis LX and runs along the M1 direction and an imaginary plane S2 that includes the optical axis LX and runs along the M2 direction are defined, the light-guiding member 23 in the front and rear views will have a symmetrical shape with respect to both the imaginary plane S1 and the imaginary plane S2 (the imaginary plane S1 passes through the longitudinal center of the light-guiding member 23, and the imaginary plane S2 passes through the lateral center).

In the M1 direction, the entire short-side dimension of the light-guiding member 23 in a front view is within the range of the second light beam LF. In other words, in the M1 direction, both the long side end surface 23c and the long side end surface 23d are located within the optical path through which the second light beam LF passes.

In the M2 direction, the longitudinal dimension of the light-guiding member 23 is slightly larger than the beam diameter of the second light beam LF, and portions of the light-guiding member 23 near both longitudinal ends are located outside the range of the second light beam LF.

Therefore, the front surface 23a and back surface 23b and the long side end surfaces 23c and 23d of the light-guiding member 23 are located within the range of the second light beam LF, except for portions near both ends in the M2 direction (longitudinal direction). In contrast, the short side end surfaces 23e and 23f are located outside the range of the second light beam LF.

The second light beam LF, which is composed of fluorescent light YL wavelength-converted by the fluorescent region 26d of the phosphor wheel 26 and excitation light BL reflected by the excitation light reflection region 26e, is converted from a diffused light beam into a substantially parallel light beam by the second lens group 25 and reaches the light-guiding member 23. As shown in FIG. 5, the majority of the area of the light-guiding member 23 that is located above the second light beam LF is the front surface 23a and back surface 23b, and in this area, the light-guiding member 23 transmits the second light beam LF directly toward the third lens group 27. The light-guiding member 23 further has a long side end surface 23c at a position where a portion of the second light beam LF is incident from the phosphor wheel 26 side.

As shown in FIG. 4 , a portion of the second light beam LF enters the light-guiding member 23 from the long side end face 23c, propagates within the light-guiding member 23 while undergoing multiple total reflections, and is emitted from the long side end face 23d. Specifically, the light that enters the light-guiding member 23 from the long side end face 23c is reflected multiple times by both the front surface 23a and the back surface 23b before being guided to the long side end face 23d. In this way, the light-guiding member 23 not only transmits the second light beam LF directly through the front surface 23a and the back surface 23b, but also separates a portion of the second light beam LF within the second optical system. As a result, in the second optical system, the light intensity distribution of the second light beam LF differs before and after the light-guiding member 23.

More specifically, the light-guiding member 23 has its incident-side long edge surface 23c located in one region in the M1 direction divided by the imaginary plane S2 shown in Figure 5, and its exit-side long edge surface 23d located in the other region in the M1 direction. Therefore, the light-guiding member 23 guides a portion of the second light beam LF from one region to the other region across the imaginary plane S2.

By including a light-guiding member 23 that functions as described above in the second optical system, it is possible to change the illuminance distribution on the irradiation surface (image display element 15) of the illumination light emitted from the light source device 12. Furthermore, by appropriately managing the direction and degree of light guiding by the light-guiding member 23, it is possible to improve the illuminance distribution on the irradiation surface (image display element 15).

The light-guiding member 23 reflects the first light beam emitted from the laser light source 20 toward the phosphor wheel 26 in the first optical system, and is provided in the second optical system to separate a portion of the second light beam LF. Therefore, an improved illuminance distribution can be achieved with a simple configuration that has a small number of parts.

The light-guiding member 23 guides a portion of the second light beam LF within the optical path of the second optical system (inside the beam diameter of the second light beam LF). This prevents light loss caused by guiding the light through the light-guiding member 23, and improves the illuminance distribution without reducing the light utilization efficiency of the light source device 12.

In addition, by causing multiple total reflections when guiding light through the light-guiding member 23, the range of change in illuminance distribution can be increased.

As shown in FIG. 5, the light-guiding member 23 has a longitudinal dimension that transverses the beam diameter of the second light beam LF. Therefore, the effect of the light-guiding member 23 can be obtained for the entire second light beam LF in the longitudinal direction (direction M2) of the light-guiding member 23.

In the projector 10, there is a correlation between the illuminance distribution of the illumination light at the image display element 15 and the illuminance distribution on the screen 17. By taking into account the influence of the projection optical system 16 and other components on the illuminance distribution and setting the light separation effect of the light-guiding member 23 in the second optical system, it is possible to improve the light distribution characteristics of not only the light source device 12 but the entire projector 10, and reduce uneven illuminance on the screen 17.

Figure 6 shows the results of experiments and measurements demonstrating the effect of the light-guiding member 23. Figure 6 shows the illuminance distribution on the screen 17 for an example in which a portion of the second light beam LF is separated (guided) using the light-guiding member 23, and a comparative example in which the second light beam LF is not separated (guided) by the light-guiding member 23. In the example, the long side end faces 23c and 23d of the light-guiding member 23 are configured as light-transmitting surfaces, allowing light to enter the light-guiding member 23 from the long side end face 23c and exit from the long side end face 23d. In the comparative example, the long side end faces 23c and 23d of the light-guiding member 23 are configured as light-absorbing surfaces, preventing light from entering the light-guiding member 23 from the long side end face 23c and light from exiting from the long side end face 23d. Projection onto the screen 17 under the same conditions resulted in the illuminance distribution shown in Figure 6.

As can be seen from Figure 6, the illuminance distribution in the Example is less variable than in the Comparative Example, and the illuminance unevenness on the screen 17 has been improved. In particular, the lack of light intensity that occurred in the Comparative Example in the area from the center to the upper left of the screen 17 has been improved in the Example.

As an example, the illuminance distribution on the screen 17 is evaluated as follows. First, the maximum illuminance on the screen 17 is normalized to 100%. Then, the area on the screen 17 onto which projection is performed by the projector 10 is equally divided into nine rectangular regions, and the average illuminance value for each region is calculated. Furthermore, the average illuminance value for the nine regions is calculated. By referring to the values calculated in this way, the unevenness of the illuminance on the screen 17 can be quantitatively evaluated.

Table 1 in Figure 6 shows the average illuminance values for each of the nine regions on the screen 17 in the example, and Table 2 shows the average illuminance values for each of the nine regions on the screen 17 in the comparative example. The average illuminance values calculated based on the data in Tables 1 and 2 were 88.0% for the example and 86.9% for the comparative example, demonstrating that the example has reduced unevenness in the illuminance distribution on the screen 17 compared to the comparative example.

In this embodiment, the angle between the normal to the second surface (long side end surface 23 c) of the light-guiding member 23 and the optical axis LX of the second optical system is 45 degrees, the average length W3 of the second surface (long side end surface 23 c) in a direction perpendicular to the ridge between the first surface (surface 23 a) and the second surface (long side end surface 23 c) of the light-guiding member ₂₃ is 0.9 mm, and the diameter _φL of the second light beam LF at the position of the ridge between the first surface (surface 23 a) and the second surface (long side end surface 23 c) of the light-guiding member 23 of the second optical system is 20 mm. Note that the diameter _φL of the second light beam LF is the diameter (light beam diameter) of the second light beam LF in a plane perpendicular to the optical axis LX at the end position of the light-guiding member 23 on the phosphor wheel 26 (wavelength conversion element) side.
where:
When the light guide member is projected onto a plane perpendicular to the optical axis of the second optical system, the average length of the second surface in a direction perpendicular to the ridge line between the first surface and the second surface is defined as W ₂ ,
The diameter of the second light flux on the optical surface immediately before the light guide member of the second optical system is φ _L ,
The distance between the optical axis of the second optical system and the center line of the long side of the incident side surface (23c) of the long side end surface of the light guide member is defined as H _i ,
The distance between the optical axis of the second optical system and the center line of the long side of the exit side surface (23d) of the long side end surface of the light guide member is H _o ,
When
_W2 = 0.64 mm
φ _L = 20 mm
H _i =7.07 mm
H _o =7.07 mm
Therefore,
W ₂ /φ _L =0.032
This becomes:

W ₂ /φ _L is a measure of the amount of light guided by the light guide member, and it is desirable that the following conditional expression (1) be satisfied.
(1) 0.018<W ₂ /φ _L <0.035

If W ₂ /φ _L is smaller than 0.018, the amount of guided light becomes too small to obtain the desired effect, whereas if _{W 2} /φ _L is larger than 0.032, the amount of guided light becomes too large, which increases the risk of adversely affecting the luminous flux.

It is more preferable to satisfy the following conditional expression (2):
(2) 0.022<W ₂ /φ _L <0.033

Note that the illuminance distribution on the screen 17 may be evaluated using methods other than those described above. For example, the number of regions on the screen 17 from which the average illuminance value is obtained may be set to a number other than nine. Furthermore, the shape of each region on the screen 17 may be a shape other than an equally divided rectangle.

Figure 7 is a schematic diagram showing the configuration of a light source device 12 according to the second embodiment. The light source device 12 of the second embodiment includes a light guide member 30 instead of the light guide member 23 of the first embodiment.

In the propagation direction (M1 direction) of the first light beam from the laser light source 20 toward the light-guiding member 30, the light-guiding member 30 is disposed eccentrically with respect to the optical axis LX. The light-guiding member 30 is not a polarizing beam splitter like the light-guiding member 23, but a dichroic mirror that reflects light in the wavelength band of the excitation light BL and transmits light in the wavelength band of the fluorescent light YL. No quarter-wave plate is provided between the light-guiding member 30 and the second lens group 25. These are the differences between the first and second embodiments. The rest of the configuration is the same as that of the light source device 12 of the first embodiment, and a description of the common parts will be omitted.

The light-guiding member 30 is a plane-parallel plate made of glass, transparent resin, or the like, and has a front surface 30a and a back surface 30b, which are parallel planes, on both sides. To enable the light-guiding member 30 to function as a dichroic mirror, the front surface 30a is coated with a coating that reflects light in the wavelength band of the excitation light BL and transmits light in the wavelength band of the fluorescent light YL.

As shown in Figure 9, when an imaginary plane S1 that includes the optical axis LX and extends along the M1 direction and an imaginary plane S2 that includes the optical axis LX and extends along the M2 direction are defined, the light-guiding member 30 in front and rear views along the optical axis LX has a shape that is symmetrical with respect to the imaginary plane S1 (the imaginary plane S1 passes through the longitudinal center of the light-guiding member 30). On the other hand, the light-guiding member 30 in front and rear views does not overlap with the imaginary plane S2 and is positioned offset from the optical axis LX in the M1 direction.

The first optical system, consisting of the first lens group 22 to the second lens group 25, causes the first light beam emitted from the laser light source 20 to be incident on the phosphor wheel 26. The second light beam, wavelength-converted by the phosphor wheel 26, passes through the second optical system, consisting of the second lens group 25 to the third lens group 27, and is incident on the color wheel 28. In the second optical system, only the fluorescent light YL passes through the light-guiding member 30 in the area where the light-guiding member 30 is located, while in the area where the light-guiding member 30 is not located, both the fluorescent light YL and the excitation light BL reach the color wheel 28. Because the light-guiding member 30 is positioned eccentrically in the M1 direction with respect to the optical axis LX, the excitation light BL can pass through a wide area of the second optical system, including the vicinity of the optical axis LX.

As shown in Figures 8 and 9, the peripheral portion of the light-guiding member 30 is composed of a pair of parallel long-side end faces (first end faces) 30c and 30d extending in the longitudinal direction, and a pair of parallel short-side end faces 30e and 30f extending in the lateral direction. Long-side end faces 30c and 30d, and short-side end faces 30e and 30f, are surfaces that are approximately perpendicular to the front surface 30a and back surface 30b, respectively. Long-side end faces 30c and 30d are also surfaces that are approximately perpendicular to the short-side end faces 30e and 30f. The light-guiding member 30 is supported and fixed near the short-side end faces 30e and 30f by support means (not shown) outside the second light beam LF.

As shown in Figure 8, the light-guiding member 30 is positioned so that the front surface 30a and back surface 30b are at an angle of approximately 45 degrees with respect to the optical axis LX when viewed from the side in the M2 direction (the side of the short side end surface 30e or short side end surface 30f). In the direction along the optical axis LX, the front surface 30a is positioned on the phosphor wheel 26 (second lens group 25) side, and the back surface 30b faces the color wheel 28 (third lens group 27) side.

9 , in a front view of light-guiding member 30 along optical axis LX, front surface 30a and long side end surface 30c face toward phosphor wheel 26. Front surface 30a, which has a larger projected area in this front view, is the first surface, long side end surface 30c, which has a smaller projected area, is the second surface, back surface 30b, which is the surface opposite front surface 30a, is the third surface, and long side end surface 30d, which is the surface opposite long side end surface 30c, is the fourth surface. The first light flux is reflected toward phosphor wheel 26 by front surface 30a, which is the first surface.

When the light-guiding member 30 is viewed from the rear along the optical axis LX from the opposite side to that shown in Figure 9, the rear surface 30b and the long side end surface 30d face toward the third lens group 27 (color wheel 28). The projected area of the rear surface 30b in rear view is larger than that of the long side end surface 30d.

In the M1 direction, the entire short-side dimension of the light-guiding member 30 in a front view is within the range of the second light beam LF. In other words, in the M1 direction, both the long side end surface 30c and the long side end surface 30d are located within the optical path through which the second light beam LF passes.

In the M2 direction, the longitudinal dimension of the light-guiding member 30 is slightly larger than the beam diameter of the second beam LF, and portions of the light-guiding member 30 near both longitudinal ends are located outside the range of the second beam LF.

Therefore, the front surface 30a and back surface 30b and the long side end surfaces 30c and 30d of the light-guiding member 30 are located within the range of the second light beam LF, except for portions near both ends in the M2 direction (longitudinal direction). In contrast, the short side end surfaces 30e and 30f are located outside the range of the second light beam LF.

As shown in FIG. 8 , a portion of the second light beam LF enters the light-guiding member 30 from the long side end surface 30c, propagates within the light-guiding member 30 while undergoing multiple total reflections, and is emitted from the long side end surface 30d. In other words, the light-guiding member 30 separates a portion of the second light beam LF within the second optical system. As a result, in the second optical system, the light intensity distribution of the second light beam LF differs before and after the light-guiding member 30.

Unlike the light-guiding member 23 of the first embodiment, the light-guiding member 30 is disposed eccentrically in the M1 direction without intersecting the optical axis LX. The long side end surface 30c, onto which a portion of the second light beam LF is incident, is located closer to the periphery of the second light beam LF. The long side end surface 30d, from which light propagated within the light-guiding member 30 emerges, is located closer to the center, closer to the optical axis LX. Therefore, the light-guiding member 30 functions to move the portion of the second light beam LF that passes through the periphery closer to the optical axis LX in the M1 direction. In other words, the light-guiding member 30 in the second optical system adjusts the illuminance distribution so as to brighten the central area of the image display element 15 or the screen 17.

The light-guiding member 30 has a longitudinal dimension that transverses the beam diameter of the second light beam LF. Therefore, the effect of the light-guiding member 30 can be obtained for the entire second light beam LF in the longitudinal direction (direction M2) of the light-guiding member 30.

Figure 10 shows the results of experiments and measurements demonstrating the effect of the light-guiding member 30. Figure 10 shows the illuminance distribution on the screen 17 for an example in which a portion of the second light beam LF is separated (guided) using the light-guiding member 30, and a comparative example in which the image display element 15 is not separated (guided) by the light-guiding member 30. In the example, the long side end faces 30c and 30d of the light-guiding member 30 are configured as light-transmitting surfaces, allowing light to enter the light-guiding member 30 from the long side end face 30c and exit from the long side end face 30d. In the comparative example, the long side end faces 30c and 30d of the light-guiding member 30 are configured as light-absorbing surfaces, preventing light from entering the light-guiding member 30 from the long side end face 30c and light from exiting from the long side end face 30d. Projection onto the screen 17 under the same conditions resulted in the illuminance distribution shown in Figure 10.

As can be seen from Figure 10, the illuminance distribution in the Example is less variable than in the Comparative Example, and the illuminance unevenness on the screen 17 has been improved. In particular, in the region near the top center of the screen 17, the Example has a wider range where a higher light intensity can be obtained than in the Comparative Example.

The unevenness of the illuminance on the screen 17 was evaluated using the same evaluation criteria as in the first embodiment. Table 3 in Figure 10 shows the average illuminance values for each of the nine regions on the screen 17 in the example, and Table 4 shows the average illuminance values for each of the nine regions on the screen 17 in the comparative example. In the second embodiment, the average illuminance calculated based on the data in Tables 3 and 4 was 90.8% for the example and 90.0% for the comparative example, indicating that the unevenness of the illuminance distribution on the screen 17 is reduced in the example compared to the comparative example.

In this embodiment, the angle between the normal to the second surface (long side end surface 30 c) of the light-guiding member 30 and the optical axis LX is 45 degrees, the average length W3 of the second surface (long side end surface 30 c) in a direction perpendicular to the ridge between the first surface (surface 30 a) and the second surface (long side end surface 30 c) of the light-guiding member ₃₀ is 0.7 mm, and the diameter φL of the second light beam _LF at the position of the ridge between the first surface (surface 30 a) and the second surface (long side end surface 30 c) of the light-guiding member 30 of the second optical system is 20 mm. Note that the diameter _φL of the second light beam LF is the diameter (light beam diameter) of the second light beam LF in a plane perpendicular to the optical axis LX at the end position of the light-guiding member 30 on the phosphor wheel 26 (wavelength conversion element) side.
Therefore,
_W2 = 0.49 mm
φ _L = 20 mm
H _i =8.04 mm
H _o =0.96 mm
Therefore,
W ₂ /φ _L =0.025
This satisfies the above conditional expressions (1) and (2).

The third embodiment of the light source device 12 shown in Figure 11 only shows the arrangement of the light-guiding member 31 when viewed from the front (and rear) along the optical axis LX. The configuration other than the light-guiding member 31 is the same as in the second embodiment, and illustrations and descriptions of common parts are omitted.

The light-guiding member 31 has the shape of a parallel flat plate made of glass, transparent resin, or the like, and its front surface 31a (first surface) , back surface 31b (third surface) , long side end surface ( second surface, first end surface) 31c, long side end surface ( fourth surface, second end surface) 31d, short side end surface 31e, and short side end surface 31f are surfaces corresponding to each of the surfaces 30a to 30f in the light-guiding member 30 of the second embodiment.

The light-guiding member 31 has an asymmetric shape with respect to both an imaginary plane S1 that includes the optical axis LX and runs along the M1 direction, and an imaginary plane S2 that includes the optical axis LX and runs along the M2 direction. More specifically, like the light-guiding member 30 of the second embodiment, the light-guiding member 31 is positioned eccentrically with respect to the optical axis LX in the M1 direction (without overlapping with the imaginary plane S2). Furthermore, the short-side end face 31e of the light-guiding member 31 is positioned closer to the imaginary plane S2 than the short-side end face 31f, and the short-side end face 31e is located within the range of the second light beam LF. In other words, the light-guiding member 31 has an asymmetric shape with respect to the position of the optical axis LX of the second optical system (imaginary plane S1) in the direction in which the long-side end faces 31c and 31d extend (the M2 direction). In the M2 direction, there are areas where the light-guiding member 31 is located within the second light beam LF and can guide light, and areas where the light-guiding member 31 does not overlap with the second light beam LF and does not guide light. The light-guiding member 31 is supported and fixed near its short side end face 31f, which is outside the range of the second light beam LF, by support means (not shown).

The imaginary plane S1 is a plane (cutting longitudinally through both long side end faces 31c and 31d) that includes the optical axis LX of the second optical system and the light beams before and after being separated (guided) by the light-guiding member 31. By including this asymmetry with respect to the imaginary plane S1 (asymmetry with respect to the optical axis LX in the M2 direction) in the requirements for setting the position of the light-guiding member 31, the degree of freedom in changing the illuminance distribution on the image display element 15 and the screen 17 is improved.

Note that while the light-guiding member 31 shown in Figure 11 has an asymmetric shape with respect to both the imaginary plane S1 and the imaginary plane S2, it is also possible to use a light-guiding member that is symmetric with respect to the imaginary plane S2 and asymmetric with respect to only the imaginary plane S1.

Figure 12 is a schematic diagram showing the configuration of a light source device 12 according to the fourth embodiment. The light source device 12 of the fourth embodiment differs from the third embodiment only in the arrangement of the light-guiding member 32. Other than the arrangement of the light-guiding member 32, the light source device 12 is the same as the third embodiment, and a description of the common parts will be omitted.

13 and 14 are diagrams illustrating the arrangement of the light-guiding member 32 of the fourth embodiment. The front surface 32a (first surface), back surface 32b (third surface) , long-side end surface 32c (second surface, first end surface) , long-side end surface 32d (fourth surface, second end surface) , short-side end surface 32e, and short-side end surface 32f of the light-guiding member 32 shown in FIGS. 13 and 14 correspond to the surfaces 31a to 31f of the light-guiding member 31. The arrangement of the light-guiding member 32 of the fourth embodiment differs from that of the third embodiment in that the light-guiding member 32 is disposed closer to the first optical system than an imaginary plane S2 that includes the optical axis LX and extends along the M2 direction. Other configurations are the same as those of the light source device 12 of the third embodiment, and a description of the common parts will be omitted. The light guide member 32 is supported and fixed by a support means (not shown) near a short side end surface 32f that is outside the range of the second light beam LF.

As shown in FIG. 13, a portion of the second light beam LF enters the light-guiding member 32 from the long side end surface 32c, propagates within the light-guiding member 32 while undergoing multiple total reflections, and is emitted from the long side end surface 32d. In other words, the light-guiding member 32 separates a portion of the second light beam LF within the second optical system. As a result, in the second optical system, the light intensity distribution of the second light beam LF differs before and after the light-guiding member 32.

As shown in FIG. 13, in the light-guiding member 32, the long side end surface 32c, onto which a portion of the second light beam LF is incident, is located toward the center, close to the optical axis LX. Furthermore, the long side end surface 32d, from which the light propagating within the light-guiding member 32 emerges, is located toward the periphery of the second light beam LF. Therefore, the light-guiding member 32 functions to redirect the portion of the second light beam LF that passes through the center away from the optical axis LX in the direction M1. In other words, the light-guiding member 32 in the second optical system adjusts the illuminance distribution to brighten the peripheral areas of the image display element 15 and the screen 17.

Figure 15 shows the results of experiments and measurements demonstrating the effect of the light-guiding member 32 of the fourth embodiment. Figure 15 shows the illuminance distribution on the screen 17 for an example in which a portion of the second light beam LF is separated (guided) using the light-guiding member 32, and a comparative example in which the image display element 15 is not separated (guided) by the light-guiding member 32. In the example, the long side end faces 32c and 32d of the light-guiding member 32 are configured as light-transmitting surfaces, allowing light to enter the light-guiding member 32 from the long side end face 32c and exit from the long side end face 32d. In the comparative example, the long side end faces 32c and 32d of the light-guiding member 32 are configured as light-absorbing surfaces, preventing light from entering the light-guiding member 32 from the long side end face 32c and exiting from the long side end face 32d. Projection onto the screen 17 under the same conditions resulted in the illuminance distribution shown in Figure 15.

As can be seen from Figure 15, the illuminance distribution in the Example is less variable than in the Comparative Example, and the illuminance unevenness on the screen 17 has been improved. In particular, in the region near the top center of the screen 17, the Example has a wider range where a higher light intensity can be obtained than in the Comparative Example.

The unevenness of the illuminance on the screen 17 was evaluated using the same evaluation criteria as in the first embodiment. Table 5 in Figure 15 shows the average illuminance values for each of the nine regions on the screen 17 in the example, and Table 6 shows the average illuminance values for each of the nine regions on the screen 17 in the comparative example. In the fourth embodiment, the average illuminance calculated based on the data in Tables 5 and 6 was 89.4% for the example and 89.1% for the comparative example, indicating that the unevenness of the illuminance distribution on the screen 17 is reduced in the example compared to the comparative example.

In this embodiment, the angle between the normal to the second surface (long side end surface 32c) of the light-guiding member 32 and the optical axis (LX) of the second optical system is 45 degrees, the average length W3 of the second surface (long side end surface 32c) in a direction perpendicular to the ridge between the first surface (surface 32a) and the second surface (long side end surface 32c) of the light-guiding member ₃₂ is 0.7 mm, and the diameter φL of the second light beam (LF) at the position of the ridge between the first surface (surface 32a) and the second surface (long side end surface 32c) of the light-guiding member 32 of the second optical system is 21 _mm . Note that the diameter _φL of the second light beam LF is the diameter (light beam diameter) of the second light beam LF in a plane perpendicular to the optical axis LX at the end position of the light-guiding member 32 on the phosphor wheel 26 (wavelength conversion element) side.
Therefore,
_W2 = 0.49 mm
φ _L = 21 mm
H _i =0.96 mm
H _o =8.04 mm
Therefore,
W ₂ /φ _L =0.024
This satisfies the above conditional expressions (1) and (2).
Furthermore, H _i /φ _L =0.046
This becomes:

H _i /φ _L is an index that represents the position within the light beam through which the area separated within the second light beam by the light-guiding member passes, and when the light is guided away from the optical axis by the light-guiding member, it is desirable to satisfy the following conditional expression (3):
(3) H _i /φ _L <0.1

Generally, the second light beam LF has a large amount of light near the optical axis LX, so when using a light-guiding member to guide the light away from the optical axis LX, guiding the light from near the optical axis LX makes it easier to adjust to reduce illuminance unevenness. If the value is greater than 0.1, the light will be farther away from the optical axis LX, making it difficult to reduce illuminance unevenness.

In the fourth embodiment, the arrangement of the light-guiding member 32 guides the light from the central portion (the portion close to the optical axis LX) of the second light beam LF to the peripheral portion (the portion farther from the optical axis LX), making it possible to adjust the distribution of the light beam LF when the light intensity in the central portion of the light beam LF is strong. This makes it possible to uniformly adjust the illuminance distribution of the image display element 15 and the screen 17.

16 is a schematic diagram showing a light source device 12 according to a fifth embodiment. The light source device 12 of the fifth embodiment is similar to the fourth embodiment in that the arrangement of the light guide member 33 guides light from the central portion (portion close to the optical axis LX) of the second light flux LF to the peripheral portion (portion farther from the optical axis LX). The front surface 33a (first surface) , the back surface 33b (third surface) , the long side end surface 33c (second surface, first end surface) , and the long side end surface 33d (fourth surface, second end surface) of the light guide member 33 correspond to the surfaces 32a to 32d of the light guide member 32, respectively.

The fifth embodiment differs from the fourth embodiment in that the angle between the optical axis LX and the normal to the second surface (long side end surface 33c) of the light-guiding member 33 is set to 35 degrees, and the optical axis of the first optical system is tilted by 20 degrees (the angle of incidence of the first surface (surface 33a) of the light-guiding member 33 is tilted to 55 degrees) so that the first light beam reflected by the first surface (surface 33a) of the light-guiding member 33 is incident on the wavelength conversion element (phosphor wheel 26). That is, the normal to the second surface (long side end surface 33c) of the light-guiding member 33 is closer to the direction of the optical axis LX of the second optical system than in the fourth embodiment. Furthermore, the normal to the first surface (surface 33a) of the light-guiding member 33 is farther from the direction of the optical axis LX of the second optical system. That is, the angle between the normal to the second surface (long side end surface 33c) and the optical axis LX of the second optical system is 35 degrees, and the angle between the normal to the first surface (surface 33a) and the second optical axis LX is 55 degrees. Therefore, the angle between the normal to the second surface (long side end surface 33c) and the optical axis LX of the second optical system is smaller than the angle between the normal to the first surface (surface 33a) and the optical axis LX of the second optical system. Other configurations are the same as those of the light source device 12 of the fourth embodiment, and a description of the common parts will be omitted.

As shown in Figure 16, the arrangement of the laser light source 20, collimator lens 21, and first lens group 22 is adjusted to match the arrangement of the light-guiding member 33. The excitation light BL emitted from the first lens group 22 is reflected by the first surface (surface 33a) of the light-guiding member 33 and enters the second lens group 25 along the optical axis LX.

In the light source device 12 of the fifth embodiment, the angle between the normal to the second surface (long side end surface 33 c) of the light guiding member 33 and the optical axis LX is 35 degrees, the average length W3 of the second surface (long side end surface 33 c) of the light guiding member (33) in a direction perpendicular to the ridge line between the first surface (surface 33 a) and the second surface (long side end surface 33 c) is 0.7 mm, and the diameter _φL of the second light beam _LF at the position of the ridge line between the first surface (surface 33 a) and the second surface (long side end surface 33 c) of the light guiding member 33 of the second optical system is 20 mm. Note that the diameter _φL of the second light beam LF is the diameter (light beam diameter) of the second light beam LF in a plane perpendicular to the optical axis LX at the end position of the light guiding member 33 on the phosphor wheel 26 (wavelength conversion element) side.
Therefore,
_W2 = 0.57 mm
φ _L = 20 mm
H _i =1.63 mm
H _o =7.37 mm
Therefore,
W ₂ /φ _L =0.029
This satisfies the above conditional expressions (1) and (2).

Furthermore, H _i /φ _L =0.082
This satisfies the above conditional expression (3).

In the light source device 12 of the fifth embodiment, the angle between the normal to the second surface (long side end surface 33 c) of the light guiding member 33 and the optical axis LX of the second optical system is made smaller than the angle between the normal to the first surface (surface 33 a) and the optical axis LX of the second optical system, thereby increasing the amount of light that is incident on the second surface (long side end surface 33 c) and guided by the light guiding member 33 out of the total amount of light in the second light flux LF. This makes it possible to increase _W2 / _φL . Therefore, the light source device 12 of the fifth embodiment can more efficiently adjust the light amount distribution of the light flux LF by the light guiding member 33.

In each of the above embodiments, the long side end faces 23c (30c, 31c, 32c, 33c) and the long side end faces 23d (30d, 31d, 32d, 33d) of the light-guiding member 23 (30, 31, 32, 33) are parallel to each other. This configuration is preferable because the incident and exit directions of light separated by the light-guiding member 23 (30, 31, 32, 33) in the second optical system are aligned. However, it is also possible to make the first end faces (second surfaces) corresponding to the long side end faces 23c (30c, 31c, 32c, 33c) and the second end faces (fourth surfaces) corresponding to the long side end faces 23d (30d, 31d, 32d, 33d) non-parallel to each other.

In each of the above embodiments, the long side end faces 23c (30c, 31c, 32c, 33c) and the long side end faces 23d (30d, 31d, 32d, 33d) of the light-guiding member 23 (30, 31, 32, 33) are surfaces perpendicular to the front surface 23a (30a, 31a, 32a, 33a) and the back surface 23b (30b, 31b, 32b, 33b). In the first to fourth embodiments, the long side end faces 23c (30c, 31c, 32c) and the long side end faces 23d (30d, 31d, 32d) are disposed at approximately 45 degrees with respect to the optical axis LX of the second optical system. Alternatively, the angle of the first end face (second surface) and the second end face (fourth surface) of the light-guiding member may be an angle other than 45 degrees with respect to the optical axis LX. For example, as in the fifth embodiment, by setting the angle of the first end face (second surface) and the second end face (fourth surface) relative to the optical axis LX to be greater than 45 degrees (a steeper angle), the projection area when viewed along the optical axis LX becomes larger, and the proportion of the second light beam LF that is separated by the light-guiding member can be increased.

The present invention is particularly useful in image display devices (projectors) that project images onto a projection surface, but can also be applied to devices other than image display devices as long as improved illuminance distribution is required. In other words, the present invention can be applied to light source optical systems, light source units, light source devices, etc. that do not include projection optical systems as components. Furthermore, in the light source optical systems, light source units, and light source devices of the present invention, the light emitted from the light source may be used for purposes other than image projection.

The above embodiments are examples of application to projectors, and the evaluation criteria are the illuminance distribution on a screen onto which an image is projected by a projector, as shown in Figures 6 and 10. However, improvement in illuminance distribution may also be determined at locations other than the screen. For example, performance evaluation of the light source optical system, light source unit, and light source device can also be performed by measuring the illuminance distribution at the image display element 15 (the irradiation surface irradiated with light from the light source device 12) in the above embodiments.

The light source device 12 in the above embodiment emits multiple colors of light in a time-division manner, but the light source device and light source unit of the present invention are not limited to types that emit multiple colors of light in a time-division manner.

The present invention has been described above using embodiments and modifications based on the attached drawings. However, the present invention is not limited to the above-described embodiments and modifications, and various modifications and applications are possible without departing from the spirit of the invention. In the above-described embodiments, the configurations illustrated in the attached drawings are not limited to these, and can be modified as appropriate within the scope of the effects of the present invention. In addition, the present invention can be modified as appropriate without departing from the spirit of the invention.

10. Projector (image display device)
12 Light source device (light source unit)
13 Light uniformizing element 14 Illumination optical system 15 Image display element 16 Projection optical system 17 Screen (projection surface)
20 laser light source (light source)
21 Collimator lens 22 First lens group (first optical system)
23 Light guide member (first optical system, second optical system)
23a: Surface (first surface)
23b Back surface (third surface)
23c Long side end surface (second surface, first end surface)
23d Long side end surface ( fourth surface, second end surface)
24 Quarter wave plate (first optical system, second optical system)
25 Second lens group (first optical system, second optical system)
26 Phosphor wheel (wavelength conversion element)
27 Third lens group (second optical system)
28 Color wheel 30 Light guide member (first optical system, second optical system)
30a: Surface (first surface)
30b Back surface (third surface)
30c Long side end surface (second surface, first end surface)
30d Long side end surface ( fourth surface, second end surface)
31 Light guide member (first optical system, second optical system)
31a: Surface (first surface)
31b Back surface (third surface)
31c Long side end surface (second surface, first end surface)
31d Long side end surface ( fourth surface, second end surface)
32 Light guide member (first optical system, second optical system)
32a: Surface (first surface)
32b Back surface (third surface)
32c Long side end surface (second surface, first end surface)
32d Long side end surface ( fourth surface, second end surface)
33 Light guide member (first optical system, second optical system)
33a Surface (first surface)
33b Back surface (third surface)
33c Long side end surface (second surface, first end surface)
33d Long side end surface ( fourth surface, second end surface)
LF: second light beam LX: optical axis of the second optical system

Claims (11)

a first optical system that causes a first light flux emitted from the light source to be incident on a wavelength conversion element;
a second optical system through which the second light flux wavelength-converted by the wavelength conversion element passes;
A light source optical system having:
a light guiding member that separates a part of the second light flux within the second optical system is provided in the second optical system ;
the light guiding member has a parallel plane plate shape, and when the light guiding member is viewed from the wavelength conversion element side along the optical axis of the second optical system, the light guiding member has a first surface having a large projected area, a second surface having a small projected area, a third surface opposite to the first surface, and a fourth surface opposite to the second surface;
a part of the separated second light flux is incident on the second surface, is totally reflected by the first surface and the third surface inside the light-guiding member multiple times, and is emitted from the fourth surface;
a light source optical system, characterized in that, when viewed along an optical axis of the second optical system, the second surface and the fourth surface are both located within a range of an optical path through which the second light flux passes . 2. The light source optical system according to claim 1 , wherein the following condition is satisfied:
0.018< _W2 / _φL <0.035
where:
_W2 represents an average value of the length of the second surface in a direction perpendicular to the ridge line between the first surface and the second surface when the light guiding member is projected onto a plane perpendicular to the optical axis of the second optical system,
_φL represents the beam diameter of the second beam on a plane perpendicular to the optical axis of the second optical system at the end position of the light guiding member on the wavelength conversion element side. 3. The light-source optical system according to claim 1 , wherein the first surface of the light-guiding member reflects the first light flux toward the wavelength conversion element. 4. The light source optical system according to claim 1, wherein the light guiding member is arranged at a position intersecting an optical axis of the second optical system, and guides a portion of the second light flux from one region to another region on either side of a plane including the optical axis. 4. The light-source optical system according to claim 1 , wherein the light guide member directs a part of the second light beam toward an optical axis of the second optical system. 4. The light-source optical system according to claim 1 , wherein the light-guiding member directs a part of the second light beam away from the optical axis of the second optical system. The light source optical system according to claim 1 , wherein the light guide member has an asymmetric shape with respect to the position of the optical axis of the second optical system in the direction in which the second surface and the fourth surface extend. The angle between the normal to the second surface and the optical axis of the second optical system is
2. The light source optical system according to claim 1 , wherein the angle is smaller than the angle formed between the normal to the first surface and the optical axis of the second optical system. A light source unit that causes a first light beam emitted from a light source to be incident on a wavelength conversion element by a first optical system, and emits a second light beam that has been wavelength-converted by the wavelength conversion element through a second optical system,
a light guiding member that separates a part of the second light flux within the second optical system is provided in the second optical system ;
the light guiding member has a parallel plane plate shape, and when the light guiding member is viewed from the wavelength conversion element side along the optical axis of the second optical system, the light guiding member has a first surface having a large projected area, a second surface having a small projected area, a third surface opposite to the first surface, and a fourth surface opposite to the second surface;
a part of the separated second light flux is incident on the second surface, is totally reflected by the first surface and the third surface inside the light-guiding member multiple times, and is emitted from the fourth surface;
A light source unit characterized in that, when viewed along the optical axis of the second optical system, both the second surface and the fourth surface are located within a range of an optical path through which the second light beam passes . A light source and
a first optical system that causes a first light flux emitted from the light source to be incident on a wavelength conversion element;
a second optical system through which the second light flux wavelength-converted by the wavelength conversion element passes;
A light source device having
a light guiding member that separates a part of the second light flux within the second optical system is provided in the second optical system ;
the light guiding member has a parallel plane plate shape, and when the light guiding member is viewed from the wavelength conversion element side along the optical axis of the second optical system, the light guiding member has a first surface having a large projected area, a second surface having a small projected area, a third surface opposite to the first surface, and a fourth surface opposite to the second surface;
a part of the separated second light flux is incident on the second surface, is totally reflected by the first surface and the third surface inside the light-guiding member multiple times, and is emitted from the fourth surface;
a light source device characterized in that, when viewed along the optical axis of the second optical system, the second surface and the fourth surface are both located within a range of an optical path through which the second light beam passes . a light source device including a first optical system that forms an optical path along which a first light beam passes from a light source to a wavelength conversion element, and a second optical system that forms an optical path along which a second light beam that has been wavelength-converted by the wavelength conversion element passes;
an image display element that modulates the light from the light source device to form an image;
a projection optical system that projects the image onto a projection surface;
An image display device having
a light guiding member that separates a part of the second light flux within the second optical system is provided in the second optical system ;
the light guiding member has a parallel plane plate shape, and when the light guiding member is viewed from the wavelength conversion element side along the optical axis of the second optical system, the light guiding member has a first surface having a large projected area, a second surface having a small projected area, a third surface opposite to the first surface, and a fourth surface opposite to the second surface;
a part of the separated second light flux is incident on the second surface, is totally reflected by the first surface and the third surface inside the light-guiding member multiple times, and is emitted from the fourth surface;
an optical axis of the second optical system, the second surface and the fourth surface being located within a range of an optical path through which the second light beam passes .