JP2021033072A - projector - Google Patents

Abstract

To provide a projector that reduces the back focus of a superposition lens and can be easily reduced in size.SOLUTION: A projector 1 comprises: a light source 102; a collimator optical system 110 that collimates illumination light LW emitted from the light source 102; a pair of multi-lens arrays 121, 122 that uniform the illumination light LW emitted from the collimator optical system 110; a concave lens 151 on which the illumination light LW emitted from the pair of multi-lens arrays 121, 122 is incident, and has a negative power; a convex lens 152a on which light emitted from the convex lens 151 is incident, and has a positive power; a liquid crystal device 400B that modulates light emitted from the convex lens 152a according to image information to form image light; and a projection optical device 600 that projects the image light.SELECTED DRAWING: Figure 1

Description

The present invention relates to a projector.

Conventionally, a projector in which a collimator optical system, a multi-lens array, a superposed lens, a liquid crystal device, and the like are arranged with respect to the light emitted from a light source has been known. For example, Patent Document 1 discloses a projection display device using a condenser lens composed of a concave lens and a convex lens, a so-called retrofocus type optical system, as a collimator optical system.

Japanese Unexamined Patent Publication No. 2000-221585

However, the projection type display device described in Patent Document 1 has a problem that it is difficult to miniaturize the device. Specifically, in order to reduce the size of the device, it is desirable to shorten the focal length of the lens on the fly-eye lens side, that is, the superposed lens, which is a multi-lens array. On the other hand, if the focal length of the superimposing lens is simply shortened, the light emitted from the superimposing lens is focused at a large incident angle, so that it is necessary to reduce the curvature of the field lens on the transmission display element side. Therefore, there is a case that the aberration is enlarged and the contrast in the transmission display element is lowered. That is, it was difficult to shorten the focal length of the superposed lens.

Further, if the size of the light source to the fly-eye lens is reduced, the size of the light source is also reduced, and it becomes difficult to secure the brightness of the light source. In order to reduce the size of the light source to the fly-eye lens while maintaining the size of the light source, it is necessary to shorten the focal length of the superposed lens as well. That is, there has been a demand for a projector that can be easily miniaturized by shortening the focal length of the superposed lens and shortening the back focus of the superposed lens.

The projector includes a light source, a first optical system that parallelizes the light emitted from the light source, a second optical system that homogenizes the light emitted from the first optical system, and light emitted from the second optical system. Is incident and the light emitted from the first optical element having negative power and the light emitted from the first optical element is incident and the light emitted from the second optical element having positive power and the light emitted from the second optical element are imaged. It includes an optical modulator that modulates according to information to form image light, and a projection optical device that projects image light.

In the above projector, the light source preferably has a light emitting element.

In the above projector, the light source preferably has a phosphor.

In the above projector, it is preferable that the first optical element has a concave surface, and the concave surface is an aspherical surface.

In the above projector, it is preferable that the second optical element has a convex surface, and the convex surface is an aspherical surface.

In the above projector, the second optical element is a concave mirror, and it is preferable that a polarization conversion element and a 1/4 retardation plate are provided between the first optical element and the second optical element.

In the above projector, the concave surface of the concave mirror is preferably aspherical.

The schematic diagram which shows the structure of the projector which concerns on 1st Embodiment. The schematic which shows the structure of the light source. The schematic diagram which shows the structure from a light source to a liquid crystal apparatus including a superimposing lens. The schematic diagram which shows the structure from a light source to a liquid crystal apparatus including a conventional superimposing lens. The schematic diagram which shows the structure of the projector which concerns on 2nd Embodiment. The figure which shows the incident angle characteristic in the liquid crystal apparatus as a comparative example. The figure which shows the incident angle characteristic in the liquid crystal apparatus as an Example. The figure which shows the illuminance distribution in the liquid crystal apparatus as a comparative example. The figure which shows the illuminance distribution in the liquid crystal apparatus as an Example. The schematic diagram which shows the structure of the projector which concerns on 3rd Embodiment. The schematic diagram which shows the structure of the projector which concerns on 4th Embodiment.

1. 1. First Embodiment 1.1. Projector Configuration In this embodiment, a projector provided with three liquid crystal devices, which are optical modulation devices, will be illustrated. The projector 1 according to the present embodiment is a projection type that modulates the light emitted from the light source to form an image according to the image information, and magnifies and projects the formed image of each color onto a projected surface such as a screen. It is an image display device.

The configuration of the optical system of the projector 1 according to the first embodiment will be described with reference to FIG. FIG. 1 is a schematic view showing the configuration of the projector 1 according to the first embodiment.

As shown in FIG. 1, the projector 1 includes a light source 102, a collimeter optical system 110 as a first optical system, a pair of multi-lens arrays 121 and 122 as a second optical system, a polarization conversion element 140, and a first optical element. Concave lens 151 as a second optical element, convex lenses 152a and 152b as a second optical element, a color separation light guide optical system 20, three liquid crystal devices 400B, 400G, 400R as an optical modulator, a color synthesis element 500, and a projection optical device 600. It has. Although not shown, the projector 1 includes a control device for controlling the operation of the projector 1, a power supply device for supplying electric power to electronic components of the projector 1, and a cooling device for cooling a light source and the like.

The projector 1 is set with an illumination optical axis Ax, which is an optical axis of the collimator optical system 110 and the pair of multi-lens arrays 121 and 122. In the projector 1, the collimator optical system 110 to the projection optical device 600 are arranged at predetermined positions corresponding to the illumination optical axis Ax.

The light source 102 emits white illumination light LW toward the collimator optical system 110. The light source 102 has a light emitting element and a phosphor (not shown). Details of the light source 102 will be described later.

The collimator optical system 110 parallelizes the illumination light LW emitted from the light source 102 and emits the illumination light LW toward the pair of multi-lens arrays 121 and 122. The collimator optical system 110 includes a first lens 111 that suppresses the spread of the illumination light LW from the light source 102, and a second lens 112 that substantially parallelizes the illumination light LW from the first lens 111.

The pair of multi-lens arrays 121 and 122, together with the superimposed lens 150 described later, equalize the illumination light LW emitted from the collimator optical system 110. The multi-lens array 121 has a plurality of small lenses 121a. The plurality of small lenses 121a divide the illumination light LW incident from the collimator optical system 110 into a plurality of partial luminous fluxes and emit the illumination light LW toward the multi-lens array 122. The plurality of small lenses 121a are arranged in a matrix of a plurality of rows and a plurality of columns in a plane orthogonal to the illumination optical axis Ax. Although not shown, the outer shape of the small lens 121a is substantially similar to the outer shape of the image forming region of the liquid crystal devices 400B, 400G, 400R.

The multi-lens array 122 has a plurality of small lenses 122a corresponding to the plurality of small lenses 121a of the multi-lens array 121. The multi-lens array 122, together with the concave lens 151 and the convex lenses 152a and 152b, forms the surfaces of the plurality of small lenses 121a in the multi-lens array 121 in the vicinity of the image forming region of the liquid crystal devices 400B, 400G and 400R. The plurality of small lenses 122a are arranged in a matrix of a plurality of rows and a plurality of columns in a plane orthogonal to the illumination optical axis Ax. The illumination light LW emitted from the pair of multi-lens arrays 121 and 122 is incident on the polarization conversion element 140.

The polarization conversion element 140 converts each partial luminous flux of the illumination light LW divided by the multi-lens array 121 into linearly polarized light having the same polarization direction, and emits the light flux toward the concave lens 151. Although not shown, the polarization conversion element 140 has a polarization separation layer, a reflection layer, and a retardation plate. The polarization separation layer transmits one of the polarization components contained in the illumination light LW as it is, and reflects the other linear polarization component in the direction perpendicular to the illumination optical axis Ax. The reflection layer reflects the other linearly polarized light component reflected by the polarization separation layer in a direction parallel to the illumination optical axis Ax. The retardation plate converts the other linearly polarized light component reflected by the reflective layer into one linearly polarized light component.

In the projector 1, a retrofocus type superimposing lens 150 is formed by a concave lens 151 and convex lenses 152a and 152b. The superimposing lens 150 collects each partial luminous flux of the illumination light LW emitted from the polarization conversion element 140 and superimposes it on the vicinity of the image forming region of the liquid crystal devices 400B, 400G, 400R. The superimposing lens 150 is arranged so that the optical axis of the superimposing lens 150 and the illumination optical axis Ax substantially coincide with each other. Among the superimposed lenses 150, a dichroic mirror 21 described later of the color separation light guide optical system 20 is arranged between the concave lens 151 and the convex lenses 152a and 152b. Therefore, each partial luminous flux of the illumination light LW transmitted through the concave lens 151 is emitted toward the dichroic mirror 21. Details of the superimposing lens 150 will be described later.

The color-separated light guide optical system 20 includes dichroic mirrors 21 and 22, reflection mirrors 23, 24, 25, and relay lenses 26, 27. The color separation light guide optical system 20 separates the illumination light LW emitted from the light source 102 into red light LR, green light LG, and blue light LB into liquid crystal devices 400R, 400G, and 400B corresponding to each color light. Guide.

The dichroic mirror 21 transmits a red light component and reflects a green light component and a blue light component in each partial luminous flux of the illumination light LW. Then, the red light component, that is, the red light LR, is incident on the convex lens 152b of the superimposing lens 150 and emitted toward the reflection mirror 23. The green light component and the blue light component are incident on the convex lens 152a of the superimposing lens 150 and emitted toward the dichroic mirror 22. That is, the concave lens 151 and the convex lens 152b form a superimposing lens 150 for a red light component. The concave lens 151 and the convex lens 152a constitute a superimposing lens 150 for a green light component and a blue light component.

The red light LR emitted from the convex lens 152b is reflected by the reflection mirror 23 and emitted toward the field lens 300R. The red light LR is not particularly limited, but is, for example, light belonging to a wavelength band of approximately 590 nm to 700 nm.

The dichroic mirror 22 reflects a green light component, that is, a green light LG, and transmits a blue light component, that is, a blue light LB. The green light LG is not particularly limited, but is, for example, light belonging to a wavelength band of approximately 500 nm to 590 nm. The blue light LB is not particularly limited, but is, for example, light belonging to a wavelength band of approximately 400 nm to 500 nm.

The green light LG reflected by the dichroic mirror 22 is emitted toward the field lens 300G. The blue light LB transmitted through the dichroic mirror 22 is reflected by the reflection mirror 24 via the relay lens 26, reflected by the reflection mirror 25 via the relay lens 27, and emitted toward the field lens 300B. Since the blue light LB has a longer optical path than the red light LR and the green light LG, the luminous flux tends to spread. Therefore, the relay lenses 26 and 27 are used to suppress the expansion of the luminous flux so that the illumination distribution is the same as that of the red light LR and the green light LG.

The field lens 300R is arranged between the color separation light guide optical system 20 and the liquid crystal device 400R, and substantially parallelizes the red light LR incident on the liquid crystal device 400R. The field lens 300G is arranged between the color separation light guide optical system 20 and the liquid crystal device 400G, and substantially parallelizes the green light LG incident on the liquid crystal device 400G. The field lens 300B is arranged between the color-separated light guide optical system 20 and the liquid crystal device 400B, and substantially parallelizes the main light beam of the blue light LB incident on the liquid crystal device 400B to make it telecentric.

Each of the liquid crystal devices 400R, 400G, and 400B modulates each incident color light according to the image information to form the image light. The image light of each color is emitted toward the color synthesis element 500. A transmissive liquid crystal panel is adopted for each of the liquid crystal devices 400R, 400G, and 400B. Although not shown, each of the liquid crystal devices 400R, 400G, and 400B is provided with an incident side polarizing plate on the light incident side and an emitting side polarizing plate on the light emitting side to form a transmissive liquid crystal light bulb. ing. The optical modulation device is not limited to the transmissive liquid crystal panel, and may be a reflective liquid crystal panel, a DMD (Digital Micromirror Device), or the like. Further, the number of optical modulation devices is not limited to three.

The color synthesis element 500 synthesizes the image light of each color emitted from the liquid crystal devices 400R, 400G, and 400B, forms the color image light, and emits the image light toward the projection optical device 600. The color synthesis element 500 is composed of a cross-dichroic prism having a substantially square shape in a plan view, in which four right-angle prisms are bonded together. A dielectric multilayer film is formed at a substantially X-shaped interface in which four right-angled prisms are bonded to each other. In the present embodiment, a cross dichroic prism is used as the color synthesis element 500, but the present embodiment is not limited to this. The color synthesis element 500 may be configured to include, for example, a plurality of dichroic mirrors.

The color image light emitted from the color synthesis element 500 is magnified and projected by the projection optical device 600, and a color image is formed on a projected surface such as a screen (not shown). The projection optical device 600 includes, for example, a set lens in which a plurality of lenses are housed in a tubular lens barrel.

1.2. Configuration of Light Source The configuration of the light source 102 of the present embodiment will be described with reference to FIG. FIG. 2 is a schematic view showing the configuration of a light source.

As shown in FIG. 2, the light source 102 includes a light source housing CA, a light source unit 41 housed in the light source housing CA, an afocal optical element 42, a homogenizer optical element 43, a polarization separating element 44, and a third. It includes 1 light source 45, a wavelength conversion element 46, a first phase difference element 47, a second light source element 48, a diffuse reflection device 49, and a second phase difference element RP. The light source housing CA is a sealed housing in which dust and the like do not easily enter the inside.

The light source unit 41, the afocal optical element 42, the homogenizer optical element 43 and the polarization separating element 44, and the first retardation element 47, the second condensing element 48 and the diffuse reflection device 49 are illuminated by the light source 102. It is arranged on the optical axis Ax1. The wavelength conversion element 46, the first condensing element 45, the polarization separating element 44, and the second retardation element RP are orthogonal to the illumination optical axis Ax1 and are arranged on the illumination optical axis Ax2 set in the light source 102. .. The illumination optical axis Ax2 set in the light source 102 and the illumination optical axis Ax set in the projector 1 are not limited to coincide with each other.

The light source unit 41 includes a plurality of first semiconductor lasers 412, a plurality of second semiconductor lasers 413, a support member 414, and a collimator lens 415 as light emitting elements that emit light. The first semiconductor laser 412 emits s-polarized blue light L1s, which is excitation light. The blue light L1s is, for example, laser light having a peak wavelength of 440 nm. The blue light L1s emitted from the first semiconductor laser 412 is incident on the wavelength conversion element 46. The second semiconductor laser 413 emits p-polarized blue light L2p. The blue light L2p is, for example, laser light having a peak wavelength of 460 nm. The blue light L2p emitted from the second semiconductor laser 413 is incident on the diffuse reflector 49.

Since the light source 102 has a light emitting element, the time required for the light source 102 to light up is shortened as compared with the discharge type light source, and the waiting time until the projector 1 projects an image or the like can be shortened.

The support member 414 supports a plurality of first semiconductor lasers 412 and a plurality of second semiconductor lasers 413 arranged in an array on a plane orthogonal to the illumination optical axis Ax1. The support member 414 is a metal member having thermal conductivity. The support member 414 may be connected to a cooling device (not shown) for cooling the plurality of first semiconductor lasers 412 and the plurality of second semiconductor lasers 413.

The blue light L1s emitted from the first semiconductor laser 412 and the blue light L2p emitted from the second semiconductor laser 413 are converted into parallel light beams by the collimator lens 415 and incident on the afocal optical element 42. In the present embodiment, the plurality of first semiconductor lasers 412 and the plurality of second semiconductor lasers 413 are configured to emit s-polarized blue light L1s and p-polarized blue light L2p, but the present invention is limited to this. However, it may be configured to emit blue light which is linearly polarized light having the same polarization direction. In this case, a phase difference element that converts one type of incident linearly polarized light into light including s-polarized light and p-polarized light may be arranged between the light source unit 41 and the polarization separating element 44.

The afocal optical element 42 adjusts the luminous flux diameters of the blue light L1s and L2p incident from the light source unit 41 so that the blue light L1s and L2p are incident on the homogenizer optical element 43. The afocal optical element 42 is composed of a lens 421 that collects incident light and a lens 422 that parallelizes the light flux collected by the lens 421. The homogenizer optical element 43 equalizes the illuminance distribution of blue light L1s and L2p. The homogenizer optical element 43 is composed of a pair of array-shaped multilenses 431 and 432. The blue light L1s and L2p that have passed through the homogenizer optical element 43 are incident on the polarization separating element 44.

The polarization separation element 44 is, for example, a prism-type polarization beam splitter, which separates the s-polarization component and the p-polarization component contained in the incident light. Specifically, the polarization separating element 44 reflects the s polarization component and transmits the p polarization component. Further, the polarization separating element 44 has a color separation characteristic of transmitting light having a predetermined wavelength or more regardless of the polarization component of the s polarization component and the p polarization component. Therefore, the s-polarized blue light L1s is reflected by the polarization separating element 44 and incident on the first condensing element 45. On the other hand, the p-polarized blue light L2p is transmitted through the polarization separating element 44 and emitted toward the first retardation element 47.

The first condensing element 45 condenses the blue light L1s reflected by the polarization separating element 44 on the wavelength conversion element 46. Further, the first condensing element 45 parallelizes the fluorescence YL incident from the wavelength conversion element 46. In the present embodiment, the first condensing element 45 is composed of two lenses 451 and 452, but is not limited thereto.

The wavelength conversion element 46 is excited by the incident blue light L1s to generate a fluorescent YL having a wavelength longer than that of the blue light L1s, and emits the fluorescence YL toward the first condensing element 45. In other words, the wavelength conversion element 46 converts the wavelength of the incident light and emits the converted light. The fluorescent YL generated by the wavelength conversion element 46 includes, for example, light having a wavelength of 500 nm to 700 nm. The wavelength conversion element 46 includes a wavelength conversion unit 461 and a heat dissipation unit 462.

The wavelength conversion unit 461 has a wavelength conversion layer 461a and a reflection layer 461b. The wavelength conversion layer 461a is a phosphor layer containing a phosphor, and wavelength-converts the incident blue light L1s to diffuse and emit fluorescent YL which is unpolarized light. The reflection layer 461b reflects the fluorescence YL incident from the wavelength conversion layer 461a toward the first condensing element 45. The heat radiating unit 462 is provided on the surface of the wavelength conversion unit 461 opposite to the light incident side, and releases the heat generated by the wavelength conversion unit 461.

The phosphor of the wavelength conversion layer 461a converts blue light L1s having a peak wavelength of 440 nm into a fluorescent YL having a peak wavelength in the range of 500 nm to 700 nm. As a result, the wavelengths of the blue light L1s emitted from the plurality of first semiconductor lasers 412 and the second semiconductor laser 413 can be converted and used.

The fluorescent YL emitted from the wavelength conversion element 46 passes through the first condensing element 45 along the illumination optical axis Ax2, and then is incident on the polarization separation element 44 having the color separation characteristic. Then, the fluorescence YL passes through the polarization separation element 44 along the illumination optical axis Ax2 and is incident on the second retardation element RP. The wavelength conversion element 46 may be configured to be rotated about a rotation axis parallel to the illumination optical axis Ax2 by a rotating device such as a motor.

The first retardation element 47 is arranged between the polarization separating element 44 and the second condensing element 48. The first retardation element 47 is a 1/4 retardation plate that converts blue light L2p that has passed through the polarization separation element 44 into circularly polarized blue light L2c. The blue light L2c is incident on the second condensing element 48. The second condensing element 48 condenses the blue light L2c incident from the first retardation element 47 on the diffuse reflector 49. Further, the second condensing element 48 parallelizes the blue light L2c incident from the diffuse reflection device 49. The number of lenses constituting the second condensing element 48 is not limited to one.

The diffuse reflection device 49 diffusely reflects the incident blue light L2c at a diffusion angle similar to that of the fluorescence YL generated and emitted by the wavelength conversion element 46. Examples of the diffuse reflector 49 include a configuration including a reflector for Lambertian reflecting the incident blue light L2c and a rotating device for rotating the reflector around a rotating axis parallel to the illumination optical axis Ax1.

The blue light L2c diffusely reflected by the diffuse reflector 49 passes through the second condensing element 48 and then is incident on the first retardation element 47. When the blue light L2c is reflected by the diffuse reflector 49, it is converted into circularly polarized light whose rotation direction is opposite. Therefore, the blue light L2c incident on the first retardation element 47 via the second condensing element 48 is the p-polarized blue light L2c when it is incident on the first retardation element 47 from the polarization separation element 44. Instead, it is converted into s-polarized blue light L2s. Then, the blue light L2s is reflected by the polarization separating element 44 and incident on the second retardation element RP. With the above configuration, the light incident on the second retardation element RP from the polarization separating element 44 becomes white light in which blue light L2s and fluorescent YL are mixed.

The second phase difference element RP converts the white light incident from the polarization separating element 44 into light in which s-polarized light and p-polarized light are mixed, that is, white illumination light LW. The illumination light LW is emitted toward the collimator optical system 110 described above.

In this embodiment, a configuration using a semiconductor laser as the light source 102 has been illustrated, but the present invention is not limited to this. As the light source of the projector 1, a discharge type lamp, a light emitting diode as a light emitting element, or the like may be used. When a light emitting diode is used, the above-mentioned phosphor may be provided.

1.3. Configuration of Superimposed Lens The configuration of the superimposition lens 150 according to the present embodiment will be described with reference to FIGS. 3 and 4. FIG. 3 is a schematic view showing a configuration from the light source 102 to the liquid crystal device 400B including the superimposing lens 150. FIG. 4 is a schematic view showing a configuration from a light source 902 to a liquid crystal device 490B, including a conventional superimposing lens 950. In FIGS. 3 and 4, the color-separated light guide optical system is omitted, and the illumination optical axis Ax is schematically arranged on a straight line. Further, in FIG. 3, among the superimposed lenses 150, the combination of the concave lens 151 and the convex lens 152a is illustrated, but the combination of the concave lens 151 and the convex lens 152b also has the same effect. The virtual image P in FIG. 3 will be described in the second embodiment.

First, the configuration of the optical system including the conventional superimposition lens 950 will be described. As shown in FIG. 4, conventionally, the number of superimposed lenses 950 is one. Specifically, the conventional optical system includes a collimator optical system 910 composed of a light source 902, a first lens 911 and a second lens 912, a pair of multi-lens arrays 921, 922, a polarization conversion element 940, a superposed lens 950, and a field lens 390B. , And a liquid crystal device 490B.

The configuration from the light source 902 to the liquid crystal device 490B is the same as that of the optical system including the superimposing lens 150 of the present embodiment, except that the superimposing lens 950 is a single convex lens. Each configuration from the light source 902 to the liquid crystal device 490B has the same function as the configuration from the light source 102 to the liquid crystal device 400B of the present embodiment. Therefore, the description of each conventional configuration will be omitted.

Since there is only one superimposing lens 950, the main plane Fd of the superimposing lens 950 overlaps with the superimposing lens 950. Therefore, the conventional superposed lens 950 has a longer focal length than the back focus, and it is necessary to shorten the focal length of the superposed lens 950 in order to shorten the back focus for miniaturization.

When the focal length of the superimposing lens 950 is shortened, the angle range of the light rays illuminating the liquid crystal device 400B becomes large, and the contrast may decrease. Further, when the focal length of the superimposing lens 950 is shortened, the brightness of the projected image may be lowered due to the generation of unusable light in the optical system in the subsequent stage of the liquid crystal device 400B.

On the other hand, as shown in FIG. 3, the superimposing lens 150 of the present embodiment is composed of two lenses, a concave lens 151 and a convex lens 152a. Specifically, the concave lens 151 as the first optical element has a negative power, and the illumination light LW emitted from the pair of multi-lens arrays 121 and 122 is incident on the concave lens 151. The convex lens 152a as the second optical element has a positive power, and the blue light component and the green light component of the illumination light LW emitted from the concave lens 151 are incident on the convex lens 152a.

In the superimposing lens 150, a concave lens 151 and then a convex lens 152a are arranged in the traveling direction of the illumination light LW, and a retrofocus type optical system is adopted. Therefore, in the superimposed lens 150, the main plane Fc is located in the space on the light emitting side of the convex lens 152a, that is, on the liquid crystal device 400B side. Therefore, in the superposed lens 150 of the present embodiment, the focal length is shorter than that of the back focus.

In addition to this, the concave lens 151 has a function of expanding the luminous flux of the illumination light LW because it has a negative power. That is, even if the light source 102 to the polarization conversion element 140 is smaller than the conventional light source 902 to the polarization conversion element 940, the spread of the luminous flux of the illumination light LW can be kept within the same range as the configuration of FIG. Become.

Further, since the focal length of the superimposed lens 150 is shorter than that of the configuration of FIG. 4, the focal lengths of the multi-lens arrays 121 and 122 are set short in order to maintain the size of the illumination region. When the focal lengths of the multi-lens arrays 121 and 122 are shortened, the light source image on the multi-lens array 122 becomes smaller. Even if the focal length of the collimator optical system 110 is shortened by downsizing the collimator optical system 110, the light source image on the multi-lens array 122 passes through each lens of the multi-lens array 122, so that the light source 102 is used. The required light source is secured without miniaturization.

As a result, when the focal length of the collimator optical system 110 is shortened, the brightness of the projector 1 is maintained, and when the focal length is not changed, the brightness of the projector 1 can be improved.

The above-mentioned actions and effects of the combination of the concave lens 151 and the convex lens 152a are similarly exhibited in the combination of the concave lens 151 and the convex lens 152b. Therefore, the description of the action and effect of the combination of the concave lens 151 and the convex lens 152b will be omitted.

According to this embodiment, the following effects can be obtained.

The back focus of the superimposing lens 150 can be shortened. Specifically, conventionally, the superimposition lens 950 was composed of one lens. Therefore, the main plane Fd of the superimposing lens 950 overlaps with the superimposing lens 950, and the focal length is longer than that of the back focus. On the other hand, in the projector 1, the concave lens 151 and the convex lenses 152a and 152b are used as the superimposing lens 150. That is, the superimposing lens 150 constitutes a retrofocus type optical system. Therefore, in the combination of the concave lens 151 and the convex lens 152a of the superimposed lens 150, the main plane Fc is located in the space on the light emitting side of the convex lens 152a. Similarly, in the combination of the concave lens 151 and the convex lens 152b, the main plane is located in the space on the light emitting side of the convex lens 152b. Therefore, the focal length is shorter than that of the back focus, and the back focus can be significantly shortened as compared with the conventional superposed lens having the same focal length.

Further, since the concave lens 151 has a negative power, it has a function of magnifying the light emitted from the convex lenses 152a and 152b. Therefore, the size from the collimator optical system 110 to the polarization conversion element 140 can be reduced as compared with the conventional case. As described above, it is possible to provide the projector 1 which shortens the back focus of the superimposing lens 150 and is easy to miniaturize.

2. Second Embodiment 2.1. Projector Configuration In this embodiment, a projector provided with three liquid crystal devices, which are optical modulation devices, will be illustrated. The projector 2 according to the present embodiment is provided with two light sources as compared with the projector 1 of the first embodiment, and adopts a retrofocus type optical system only for a superposed lens arranged in one optical path of the light source. Is different. Therefore, the same reference numerals are used for the same components as those in the first embodiment, and duplicate description will be omitted.

The configuration of the optical system of the projector 2 according to the second embodiment will be described with reference to FIG. FIG. 5 is a schematic view showing the configuration of the projector 2 according to the second embodiment.

As shown in FIG. 5, the projector 2 includes two independent light sources 802 and 202. The light source 802 includes a semiconductor laser, a phosphor, a wavelength conversion unit, and the like (not shown) that emits excitation light, and emits fluorescent YL. The light source 202 includes a semiconductor laser and a phosphor that emit blue light (not shown), and emits blue light LB. The blue light LB is, for example, the above-mentioned s-polarized blue light L2s. In the projector 2, a conventional optical system including a conventional superimposing lens 950 is adopted in the optical path of the fluorescent YL, and a retrofocus type superimposing lens 150 similar to that in the first embodiment is adopted in the optical path of the blue light LB.

The fluorescent YL emitted from the light source 802 is incident on the collimator optical system 910 including the first lens 911 and the second lens 912. The collimator optical system 910 parallelizes the fluorescent YL and emits the fluorescence YL toward the pair of multi-lens arrays 921 and 922. The fluorescent YL divided into a plurality of partial luminous fluxes by the pair of multi-lens arrays 921 and 922 is emitted toward the conventional superposed lens 950 via the polarization conversion element 940. The superimposing lens 950 is a single convex lens as described above.

The fluorescent YL is incident on the color-separated light guide optical system including the dichroic mirror 28 and the reflection mirrors 23 and 29 from the superimposing lens 950. The dichroic mirror 28 transmits the red light component of each partial luminous flux of the fluorescent YL and reflects the green light component. Then, the red light component, that is, the red light LR, is reflected by the reflection mirror 23 and then illuminates the liquid crystal device 400R via the field lens 300R.

The green light component reflected by the dichroic mirror 28, that is, the green light LG, is reflected by the reflection mirror 29 and then illuminates the liquid crystal device 400G via the field lens 300G.

The blue light LB emitted from the light source 202 is incident on the collimator optical system 110 including the first lens 111 and the second lens 112. The collimator optical system 110 parallelizes the blue light LB and emits the blue light LB toward the pair of multi-lens arrays 121 and 122. The blue light LB divided into a plurality of partial luminous fluxes by the pair of multi-lens arrays 121 and 122 is emitted toward the superimposing lens 150 via the polarization conversion element 140.

The superimposing lens 150 collects each partial luminous flux of the blue light LB and superimposes it on the vicinity of the image forming region of the liquid crystal apparatus 400B. In the superimposing lens 150, a retrofocus type optical system including a concave lens 151 and a convex lens 152a is formed. The blue light LB emitted from the superimposing lens 150 is reflected by the reflection mirror 25 and then illuminates the liquid crystal device 400B through the field lens 300B.

Here, in the present embodiment, the retrofocus type superimposition lens 150 is arranged on the optical path of the blue light LB, but the present invention is not limited to this. The superimposing lens 150 may be arranged on the optical path of the fluorescent YL, and the conventional superimposing lens 950 may be arranged on the optical path of the blue light LB. Further, the light sources 802 and 202 are not limited to including the semiconductor laser, and may include a discharge type lamp, a light emitting diode, a phosphor, and the like.

2.2. Incident angle characteristics and illuminance distribution in a liquid crystal device Next, FIGS. 6 to 9 show an optical path of a fluorescent YL using a superposed lens 950 as a comparative example and an optical path of a blue light LB using a superposed lens 150 as an example. It will be explained with reference to. Further, in the following description, FIG. 3 of the first embodiment is also referred to. In the following description, the optical system using the superimposing lens 150 may be referred to as the optical system of the embodiment, and the optical system using the superimposing lens 950 may be referred to as the optical system of the comparative example.

FIG. 6 is a diagram showing incident angle characteristics in a liquid crystal device as a comparative example. FIG. 7 is a diagram showing incident angle characteristics in a liquid crystal device as an example. FIG. 8 is a diagram showing an illuminance distribution in a liquid crystal device as a comparative example. FIG. 9 is a diagram showing an illuminance distribution in a liquid crystal apparatus as an example.

Here, the examples and comparative examples are based on simulation. As a premise of the simulation, the positions and curvatures of the concave lens 151 and the convex lens 152a are adjusted with respect to the fluorescent YL optical system. Specifically, in FIG. 3, the virtual image P of the multi-lens array 122 or the polarization conversion element 140 viewed from the exit side of the optical path of the superimposed lens 150 has the same size and position as the optical path of the fluorescent YL. .. The simulation was carried out with a configuration in which the fluorescent YL was directly incident on the liquid crystal device without using a polarization separating element or the like.

FIG. 6 shows the incident angle of the fluorescent YL with respect to the liquid crystal device, and FIG. 7 shows the incident angle of the blue light LB with respect to the liquid crystal device in shades of gradation. FIG. 8 shows the illuminance of the fluorescent YL with respect to the liquid crystal device, and FIG. 9 shows the illuminance of the blue light LB with respect to the liquid crystal device in shades of gradation.

As shown in FIGS. 6 and 7, it was found that in the optical system of the example, a distribution of incident angles substantially similar to that of the optical system of the comparative example can be obtained. Further, in the optical system of the comparative example shown in FIG. 8, a substantially uniform illuminance distribution is obtained over the entire display area of the substantially rectangular liquid crystal device. On the other hand, in the optical system of the example shown in FIG. 9, it was found that a substantially uniform illuminance distribution can be obtained in the display region Q of the liquid crystal device shown by the broken line.

By adopting the superimposing lens 150 in the optical path of the blue light LB, the distance from the pair of multi-lens arrays 121 to the field lens 300B is shortened by about 35% as compared with the optical path of the fluorescent YL adopting the conventional superimposing lens 950. Was done. Further, the above distance is shortened to facilitate miniaturization of the projector 2, and in the optical system of the embodiment, an incident angle distribution and an illuminance distribution equivalent to those of the optical system of the comparative example, in other words, an illumination state can be obtained. It turned out.

According to this embodiment, the following effects can be obtained in addition to the effects in the first embodiment.

Even if the two light sources 202 and 802 are used, it is possible to make the illumination states of the liquid crystal device uniform. Therefore, it is possible to provide the projector 2 capable of projecting a color image having high display quality with less unevenness.

3. 3. Third Embodiment In the present embodiment, a projector provided with three liquid crystal devices, which are optical modulation devices, will be illustrated. The projector 3 according to the present embodiment is different from the projector 1 of the first embodiment in that it is provided with three light sources and a retrofocus type superimposing lens 150 is adopted for each of the three light sources. Therefore, the same reference numerals are used for the same components as those in the first embodiment, and duplicate description will be omitted.

The configuration of the optical system of the projector 3 according to the third embodiment will be described with reference to FIG. FIG. 10 is a schematic view showing the configuration of the projector 3 according to the third embodiment.

As shown in FIG. 10, the projector 3 includes three independent light sources 202, 302, and 402, respectively. The light source 202 emits blue light LB. The light source 302 emits green light LG. The light source 402 emits red light LR. The light sources 202, 302, and 402 include a light emitting element such as a semiconductor laser or a light emitting diode and a phosphor. Further, a discharge type lamp or the like may be used as the light sources 202, 302, 402.

In the projector 3, the retrofocus type superimposition lens 150 similar to that of the first embodiment is adopted in each of the optical paths corresponding to the three light sources 202, 302, and 402. That is, on each optical path of blue light LB, green light LG, and red light LR, a collimator optical system 110, a pair of multi-lens arrays 121, 122, a polarization conversion element 140, and a concave lens 151 and a convex lens 152a are superimposed. The lens 150 is arranged.

The blue light LB is emitted from the convex lens 152a, reflected by the reflection mirror 25, and then illuminates the liquid crystal device 400B through the field lens 300B. After being emitted from the convex lens 152a, the green light LG illuminates the liquid crystal device 400G via the field lens 300G. The red light LR is emitted from the convex lens 152a, reflected by the reflection mirror 23, and then illuminates the liquid crystal device 400R via the field lens 300R.

According to this embodiment, in addition to the effect in the first embodiment, the dichroic mirror can be omitted.

4. Fourth Embodiment In the present embodiment, a projector provided with three liquid crystal devices which are optical modulation devices will be exemplified. The projector 4 according to the present embodiment is obtained by changing the configuration of the superimposing lens 150 and the like with respect to the projector 2 of the second embodiment. Therefore, the same reference numerals are used for the same components as those in the second embodiment, and duplicate description will be omitted.

The configuration of the optical system of the projector 4 according to the fourth embodiment will be described with reference to FIG. FIG. 11 is a schematic view showing the configuration of the projector 4 according to the fourth embodiment.

As shown in FIG. 11, the projector 4 includes two independent light sources 802 and 202. The configuration from the light source 802 to the liquid crystal devices 400R and 400G and the configuration from the light source 202 to the polarization conversion element 140 are the same as those of the projector 2 of the second embodiment.

The projector 4 includes a superimposing lens 160, a polarization beam splitter 30 as a polarization conversion element, and a 1/4 retardation plate 171 on the optical path of the blue light LB emitted from the light source 202. Specifically, the superimposing lens 160 has a concave lens 161 as a first optical element having a negative power and a concave mirror 162 having a positive power as a second optical element. That is, the concave lens 161 and the concave mirror 162 form a retrofocus type superimposing lens 160.

A polarizing beam splitter 30 and a 1/4 retardation plate 171 are provided between the concave lens 161 and the concave mirror 162.

The p-polarized blue light LB emitted from the light source 202 is incident on the polarization conversion element 140 via the collimator optical system 110 and the pair of multi-lens arrays 121 and 122. The polarization conversion element 140 converts each partial luminous flux of the blue light LB divided by the multi-lens array 121 into p-polarized light which is linearly polarized light having the same polarization direction, and emits the light flux toward the concave lens 161 of the superimposing lens 160.

The superimposing lens 160 collects each partial luminous flux of the blue light LB emitted from the polarization conversion element 140 by the concave lens 161 and the concave mirror 162, and superimposes the light flux on the vicinity of the image forming region of the liquid crystal apparatus 400B. The blue light LB transmitted through the concave lens 161 is emitted toward the polarizing beam splitter 30.

The polarization beam splitter 30 is, for example, a prism type, and reflects the s-polarized light component and transmits the p-polarized light component. Since the blue light LB incident on the polarizing beam splitter 30 is p-polarized, it is transmitted by the polarizing beam splitter 30 and emitted toward the 1/4 retardation plate 171.

The 1/4 retardation plate 171 converts the blue light LB incident from the polarization beam splitter 30 into circular polarization and emits it toward the concave mirror 162. The concave mirror 162 collects and reflects the circularly polarized blue light LB and emits it toward the 1/4 retardation plate 171.

The circularly polarized blue light LB reflected by the concave mirror 162 is rotated in the polarization direction by 90 ° by the 1/4 retardation plate 171 to become s-polarized blue light LB. The s-polarized blue light LB is emitted from the 1/4 retardation plate 171 toward the polarization beam splitter 30. The polarization beam splitter 30 reflects the s-polarized blue light LB and emits it toward the field lens 300B.

In the present embodiment, the concave mirror 162 is provided as the second optical element having a positive power, but the present invention is not limited to this. A convex lens and a reflector may be used instead of the concave mirror 162.

According to this embodiment, the following effects can be obtained in addition to the effects in the second embodiment.

The distance between the concave lens 161 and the liquid crystal device 400B can be further shortened. Specifically, by aligning the polarization direction of the blue light LB emitted from the light source 202 with p-polarized light, the blue light LB emitted from the concave lens 161 is transmitted to the polarization beam splitter 30. The blue light LB transmitted through the polarizing beam splitter 30 is incident on the 1/4 retardation plate 171. Then, it is transmitted through the 1/4 retardation plate 171 to become circularly polarized light, is reflected by the concave mirror 162, and is incident on the 1/4 retardation plate 171 again. At this time, by passing through the 1/4 retardation plate 171, s-polarized light whose polarization direction is rotated by 90 ° with respect to the blue light LB emitted from the concave lens 161 is obtained. Therefore, the polarized light is reflected without being transmitted by the polarization beam splitter 30 to illuminate the liquid crystal device 400B. Therefore, as compared with the case where the second optical element is a convex lens, the distance between the concave lens 161 and the liquid crystal device 400B is shortened, and the projector 4 can be further miniaturized.

5. First Modification Example In the projector according to this modification, the concave surface of the concave lens as the first optical element is an aspherical surface, and the convex surface of the convex lens as the second optical element is the convex surface of the projector 1 of the first embodiment. It is an aspherical surface. An aspherical surface may be adopted for either of the first optical element and the second optical element, but from the viewpoint of the effect described later, an aspherical surface is adopted for both the first optical element and the second optical element. Is preferable.

In the same manner as this, in the superposed lens 150 of the second embodiment or the third embodiment, aspherical surfaces may be adopted for the concave surface of the concave lens 151 and the convex surface of the convex lens 152a, respectively.

According to this modification, since the aspherical surface is adopted for the first optical element and the second optical element, the aberration in the first optical element and the second optical element is reduced. Therefore, the imaging performance of the superposed lens is improved, and the light is easily focused in the display area of the liquid crystal device. As a result, the illuminance distribution of the light that illuminates the liquid crystal device can be made more uniform.

6. Second Modified Example In the projector according to this modified example, the concave surface provided on the concave lens as the first optical element is an aspherical surface, and the concave surface provided on the concave mirror as the second optical element is provided with respect to the projector 4 of the fourth embodiment. Is an aspherical surface. From the viewpoint of the effect described later, it is preferable to adopt an aspherical surface for both the concave surface of the second optical element and the concave surface of the first optical element.

According to this modification, since the aspherical surface is adopted for the first optical element and the second optical element, the aberration in the first optical element and the second optical element is reduced. Therefore, the imaging performance of the superposed lens is improved, and the light is easily focused in the display area of the liquid crystal device. As a result, the illuminance distribution of the light that illuminates the liquid crystal device can be made more uniform.

The contents derived from the embodiment are described below.

The projector includes a light source, a first optical system that parallelizes the light emitted from the light source, a second optical system that homogenizes the light emitted from the first optical system, and light emitted from the second optical system. Is incident and the light emitted from the first optical element having negative power and the light emitted from the first optical element is incident and the light emitted from the second optical element having positive power and the light emitted from the second optical element are imaged. It includes an optical modulator that modulates according to information to form image light, and a projection optical device that projects image light.

According to this configuration, the focal length of the superposed lens can be shortened. Specifically, conventionally, a relay lens on the fly-eye lens side, which is a multi-lens array, that is, a superposed lens has been composed of one lens. Therefore, the main plane of the superposed lens overlaps with the superposed lens, and the focal length is longer than that of the back focus. On the other hand, in the present invention, the first optical element and the second optical element are used as superimposing lenses. Since the first optical element and the second optical element constitute a retrofocus type optical system, the main plane of the optical system is located in the space on the light emitting side of the second optical element. Therefore, the focal length is shorter than that of the back focus, and the focal length of the superposed lens can be remarkably shortened as compared with the conventional case.

Further, since the first optical element has a negative power, it has a function of enlarging the light emitted from the second optical system. Therefore, the size from the light source to the second optical system can be reduced as compared with the conventional case. As described above, it is possible to provide a projector in which the focal length of the superposed lens is shortened and the size of the projector can be easily reduced. Further, it is possible to provide a projector in which the back focus of the superposed lens is shortened and the size of the projector can be easily reduced.

In the above projector, the light source preferably has a light emitting element.

According to this configuration, the time required for lighting is shortened as compared with the discharge type light source, and the waiting time until the projector projects an image or the like can be shortened.

In the above projector, the light source preferably has a phosphor.

According to this configuration, the phosphor converts light of a specific wavelength into fluorescence. That is, the wavelength of the light emitted from the light emitting element can be converted and used.

In the above projector, it is preferable that the first optical element has a concave surface, and the concave surface is an aspherical surface.

According to this configuration, the aberration in the first optical element is reduced as compared with the case where the concave surface provided in the first optical element is a spherical surface. Therefore, it is possible to illuminate the light modulation device while suppressing the variation in the illuminance distribution.

In the above projector, it is preferable that the second optical element has a convex surface, and the convex surface is an aspherical surface.

According to this configuration, the aberration in the second optical element can be suppressed as compared with the case where the convex surface provided in the second optical element is a spherical surface. Therefore, it is possible to illuminate the light modulation device while suppressing the variation in the illuminance distribution.

In the above projector, the second optical element is a concave mirror, and it is preferable that a polarization conversion element and a 1/4 retardation plate are provided between the first optical element and the second optical element.

According to this configuration, the distance between the first optical element and the optical modulation device can be shortened. Specifically, by aligning the polarization directions of the light emitted from the light source, the light emitted from the first optical element is transmitted to the polarization conversion element. The light transmitted through the polarization conversion element is incident on the 1/4 retardation plate. Then, it becomes circularly polarized light by being transmitted through the 1/4 retardation plate, is reflected by the concave mirror, and is incident on the 1/4 retardation plate again. At this time, by passing through the 1/4 retardation plate, the polarized light is polarized by rotating the polarization direction by 90 ° with respect to the light emitted from the first optical element. Therefore, the polarized light is reflected without being transmitted to the polarization conversion element to illuminate the light modulation device. Therefore, as compared with the case where the second optical element is a convex lens, the distance between the first optical element and the optical modulation device can be shortened, and the projector can be further miniaturized.

In the above projector, the concave surface of the concave mirror is preferably aspherical.

According to this configuration, the aberration in the second optical element can be suppressed as compared with the case where the concave surface of the concave mirror is spherical. Therefore, it is possible to illuminate the light modulation device while suppressing the variation in the illuminance distribution.

1,2,3,4 ... Projector, 30 ... Polarized beam splitter as polarization conversion element, 102, 202, 302, 402 ... Light source, 110 ... Corimeter optical system as first optical system, 121, 122 ... Second A pair of multi-lens arrays as an optical system, 151 ... a concave lens as a first optical element, 152a, 152b ... a convex lens as a second optical element, 162 ... a concave mirror as a second optical element, 171 ... 1/4 phase difference Plate, 400B, 400G, 400R ... Liquid crystal device as an optical modulator, 412 ... First semiconductor laser as a light emitting element, 413 ... Second semiconductor laser as a light emitting element, 600 ... Projection optical device, LW ... Illumination light, YL …fluorescence.

Claims (7)

Light source and
A first optical system that parallelizes the light emitted from the light source,
A second optical system that homogenizes the light emitted from the first optical system, and
The light emitted from the second optical system is incident, and the first optical element having a negative power and
The light emitted from the first optical element is incident, and the second optical element having a positive power and
An optical modulator that modulates the light emitted from the second optical element according to image information to form image light, and
The projection optical device that projects the image light and
Projector equipped with. The projector according to claim 1, wherein the light source has a light emitting element. The projector according to claim 2, wherein the light source has a phosphor. The first optical element has a concave surface and has a concave surface.
The projector according to any one of claims 1 to 3, wherein the concave surface is an aspherical surface. The second optical element has a convex surface and has a convex surface.
The projector according to any one of claims 1 to 4, wherein the convex surface is an aspherical surface. The second optical element is a concave mirror.
The projector according to any one of claims 1 to 4, wherein a polarization conversion element and a 1/4 retardation plate are provided between the first optical element and the second optical element. The projector according to claim 6, wherein the concave surface of the concave mirror is an aspherical surface.

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