Patent ID: 12222636

DETAILED DESCRIPTION

An example of an embodiment of a technique of the disclosure will be described below with reference to the drawings. Terms, such as “first”, “second”, and “third”, used in this specification are added to avoid the confusion of components and do not limit the number of components present in a projection device or a projection lens.

As shown inFIG.1, a projector10is an example of “projection device” according to the technique of the disclosure, and comprises a projection lens11and a body part12. The body part12is an example of “housing” according to the technique of the disclosure. One end portion of the projection lens11is mounted on the body part12. The body part12houses main components, such as an image forming unit13and a control board.

The image forming unit13forms an image that is to be projected on a screen14through the projection lens11. The image forming unit13comprises an image forming panel15, a light source16, a light guide member (not shown), and the like. The light source16applies light to the image forming panel15. The light guide member guides light, which is applied from the light source16, to the image forming panel15.

The image forming unit13is, for example, a reflective type image forming unit that uses a digital micromirror device (DMD: registered trademark) as the image forming panel15. As well known, the DMD is an image display element which includes a plurality of micromirrors capable of changing the reflection direction of light applied from the light source16and in which the respective micromirrors are two-dimensionally arranged in pixels. The DMD performs optical modulation corresponding to an image by changing the direction of each micromirror according to the image to switch the ON/OFF of reflected light of light applied from the light source16. The image forming panel15is an example of “electro-optical element” according to the technique of the disclosure.

Examples of the light source16include a white light source. The white light source emits white light. The white light source is, for example, a light source that is realized from the combination of a laser light source and a phosphor. The laser light source emits blue light to the phosphor as excitation light. The phosphor emits yellow light in a case where the phosphor is excited by blue light emitted from the laser light source. The white light source emits white light by combining blue light that is emitted from the laser light source with yellow light that is emitted from the phosphor. The image forming unit13is further provided with a rotary color filter that selectively converts white light emitted from the light source16into each of blue light B (Blue), green light G (Green), and red light R (Red) in a time-sharing manner. Each of blue light B, green light G, and red light R is selectively applied to the image forming panel15, so that image light where image information about each of blue light B, green light G, and red light R is carried and supported is obtained. Each color image light obtained in this way is selectively incident on the projection lens11, so that each color image light is projected toward the screen14. The respective color image lights are integrated with each other on the screen14. Accordingly, a full color image P is displayed on the screen14.

Luminous flux representing an image formed by the image forming unit13is incident on the projection lens11from the body part12. The projection lens11enlarges image light, which is based on the incident luminous flux, by an optical system and forms an image. Accordingly, the projection lens11projects the image P, which is the enlarged image of the image formed by the image forming unit13, on the screen14.

As shown inFIG.2, the projection lens11comprises a bending optical system. The bending optical system has a first optical axis A1, a second optical axis A2, and a third optical axis A3. The first optical axis A1is an optical axis along which light emitted from the body part12passes. The second optical axis A2is an optical axis that is bent at an angle of 90° from the first optical axis A1. The third optical axis A3is an optical axis that is bent at an angle of 90° from the second optical axis A2.FIG.2shows the projection lens11from which an exterior cover is removed.

The projection lens11includes a first holding part20, a second holding part21, and a third holding part22. The respective holding parts20to22hold lenses, respectively. The lenses held by the first holding part20are arranged on the first optical axis A1, the lenses held by the second holding part21are arranged on the second optical axis A2, and the lenses held by the third holding part22are arranged on the third optical axis A3. A central axis of the first holding part20substantially coincides with the first optical axis A1, a central axis of the second holding part21substantially coincides with the second optical axis A2, and a central axis of the third holding part22substantially coincides with the third optical axis A3. In this embodiment, in order to simplify description, the detailed configuration of the respective lenses will be omitted and each of the lenses will be represented as one lens. However, each lens may be a plurality of lenses.

The first holding part20is positioned to be closest to an incident side, and the third holding part22is positioned to be closest to an emission side. The second holding part21is positioned between the first holding part20and the third holding part22. In the following description, the incident side may be referred to as a reduction side, and the emission side may be referred to as an enlargement side.

The first holding part20holds a first optical system L1. The first optical system L1is composed of, for example, a lens L11, a lens L12, a lens L13, a lens L14, a lens L15, and a lens L16, and is disposed along the first optical axis A1. Further, a stationary stop25is provided between the lenses L13and L14in the first holding part20. The stationary stop25narrows luminous flux incident from the body part12.

The lens L11is disposed to be closest to the reduction side in the first optical system L1. That is, the lens L11is an example of “first lens” according to the technique of the disclosure.

The first optical system L1forms an intermediate image MI of an optical image of the image forming panel15. For this reason, the lens L16, which is disposed immediately behind the imaging position of the intermediate image MI on the reduction side and is disposed to be closest to the enlargement side in the first optical system L1, is an example of “second lens” according to the technique of the disclosure.

The lenses L15and L16are adjacent to each other. The lens L15is an aspherical lens that is disposed to be closer to the reduction side than the lens L16and is made of a resin material. That is, the lens L15is an example of “third lens” according to the technique of the disclosure. The lens L15functions as a correction lens for correcting a field curvature and the like. Lenses, which include lenses of second and third optical systems L2and L3to be described later other than the lens L15, are lenses made of glass.

The second holding part21includes a holding frame28and a cover29. As shown also inFIG.3showing a state where the cover29is removed, the holding frame28integrally holds a first mirror30and a second mirror31. The cover29has a light shielding property and covers the back side of the holding frame28.

Each of the first and second mirrors30and31is one of optical elements composing the bending optical system and bends an optical axis. The first mirror30bends light parallel to the first optical axis A1to form light parallel to the second optical axis A2. The second mirror31bends light parallel to the second optical axis A2to form light parallel to the third optical axis A3. That is, the first mirror30is an example of “first reflective part” according to the technique of the disclosure, and the second mirror31is an example of “second reflective part” according to the technique of the disclosure.

The first mirror30is held in an attitude where a reflective surface forms an angle of 45° with respect to each of the first optical axis A1and the second optical axis A2. Likewise, the second mirror31is held in an attitude where a reflective surface forms an angle of 45° with respect to each of the second optical axis A2and the third optical axis A3. Each of the first and second mirrors30and31is a specular reflective type mirror of which a transparent member, such as glass, is coated with a reflective film.

The intermediate image MI is formed to be closer to the reduction side than a second optical system L2, for example, to be closer to the reduction side than the first mirror30. In other words, the intermediate image MI is formed at a position between the lens L16and the first mirror30.

The second holding part21holds a second optical system L2. The second optical system L2is composed of, for example, a lens L21and a lens L22and is disposed along the second optical axis A2. In this example, the second optical system L2functions as a relay lens. More specifically, the second optical system L2uses the intermediate image MI, which is formed by the first optical system L1, as a subject and relays the luminous flux representing the intermediate image MI to the third holding part22.

The third holding part22holds a third optical system L3. The third optical system L3is an emission optical system, is composed of, for example, a lens L31, a lens L32, and a lens L33, and is disposed along the third optical axis A3. The lens L33is a lens that is disposed to be closest to the enlargement side in the third optical system L3, and is a so-called emission lens.

A distance D1along the first optical axis A1between the lens L11and the first mirror30is longer than a distance D2along the second optical axis A2between the first mirror30and the second mirror31(D1>D2; see a balloon35). The distance D1is, more exactly, an interval along the first optical axis A1between the incident surface of the lens L11and the reflective surface of the first mirror30. Likewise, the distance D2is, more exactly, an interval along the second optical axis A2between the reflective surface of the first mirror30and the reflective surface of the second mirror31.

InFIG.4, a distance D3between the stationary stop25and the lens L15is longer than a distance D4between the stationary stop25and the lens L11(D4<D3; see a balloon40). The distance D3is, more exactly, an interval along the first optical axis A1between the stationary stop25and the incident surface of the lens L15. Likewise, the distance D4is, more exactly, an interval along the first optical axis A1between the stationary stop25and the emission surface of the lens L11.

A diameter Φ15of the optical surface of the lens L15is larger than a diameter Φ11of the optical surface of the lens L11and is smaller than a diameter Φ16of the optical surface of the lens L16(Φ11<Φ15<Φ16; see a balloon41). Further, the diameter Φ15of the optical surface of the lens L15is 1.3 to 2 times the diameter Φ11of the optical surface of the lens L11(Φ15=1.3×Φ11to 2×Φ11; see the balloon41). The diameter of the optical surface is a diameter of a circular region of each lens through which a ray can pass in a state where the optical system is held by each holding part.

Further, the diameter Φ16of the optical surface of the lens L16is largest among the diameters of the optical surfaces of the respective lenses composing the first optical system L1.

A diameter Φ21of the optical surface of the lens L21composing the second optical system L2and a diameter Φ22of the optical surface of the lens L22are smaller than the diameter Φ16of the optical surface of the lens L16(Φ21<Φ16and Φ22<Φ16; see a balloon42).

As shown inFIG.5, in a case where a focal length of the lens L15is denoted by f3, |1/f3| is 0.03 or less (|1/f3|≤0.03). More preferably, |1/f3| is smaller than 0.025 (|1/f3|<0.025). Further, as shown inFIG.6, in a case where a focal length of the lens L16is denoted by f2, |1/f3| is smaller than |1/f2| (|1/f3|<|1/f2|).

Furthermore, although not shown, |1/f2| is 0.025 or more and 0.1 or less (0.025≤|1/f2|≤0.1). More preferably, |1/f2| is larger than 0.03 and 0.1 or less (0.03<|1/f2|≤0.1).

InFIG.7, a lower portion of the holding frame28forming the second holding part21is fixed to the first holding part20by a second holding part-fixing mechanism50. The second holding part-fixing mechanism50includes male screws51, female screws52that engage with the male screws51, and circular screw insertion holes53into which the male screws51are inserted. Sets of the male screw51, the female screw52, and the screw insertion hole53are provided at the positions of the respective corner of a substantially square shape one by one, that is, a total of four sets thereof are provided. The female screws52are formed in the first holding part20, and the screw insertion holes53are formed in the holding frame28. An inner diameter of the screw insertion hole53is larger than the outer diameter of a screw portion of the male screw51.

Four protrusions54are formed on the first holding part20at positions symmetrical with each other. Four circular protrusion insertion holes55are formed in the holding frame28at positions facing the protrusions54. The inner diameter of the protrusion insertion hole55is larger than the outer diameter of the protrusion54.

In a case where the holding frame28is to be fixed to the first holding part20, the holding frame28is united with the first holding part20first such that the protrusions54are inserted into the protrusion insertion holes55. After that, the male screws51are inserted into the screw insertion holes53, engage with the female screws52, and are tightened.

In a state where the fastening between the male screws51and the female screws52is loosened, that is, a state where a fixing force of the second holding part-fixing mechanism50is reduced, the holding frame28can be shifted relative to the first holding part20by a difference in dimension between the inner diameter of the screw insertion hole53and the outer diameter of the screw portion of the male screw51and a difference in dimension between the inner diameter of the protrusion insertion hole55and the outer diameter of the protrusion54. A state where the cover29, the first mirror30, and the second mirror31are removed is shown inFIG.7.

Next, the action obtained from the above-mentioned configuration will be described. First, luminous flux representing an image formed by the image forming unit13is incident on the lens L11of the first optical system L1of the projection lens11. Subsequently, the luminous flux passes through the lenses L12and L13and passes through the stationary stop25, so that the amount of light is adjusted. The luminous flux of which the amount of light is adjusted by the stationary stop25passes through the lens L14and further passes through the lens L15, so that a field curvature and the like is corrected.

The lens L15is an aspherical lens made of a resin material. For this reason, the lens L15is still more inexpensive than an aspherical lens made of glass. Further, a plurality of lenses, such as a combination of positive and negative lenses, is necessary to correct a field curvature and the like by a spherical lens made of glass. For this reason, it is not possible to avoid an increase in the distance D1along the first optical axis A1, that is, an increase in the size of the first holding part20. However, since a field curvature and the like are corrected by the aspherical lens L15made of a resin material in this example, an increase in the size of the first holding part20is suppressed.

As shown inFIG.4, the distance D3between the stationary stop25and the lens L15is set to be larger than the distance D4between the stationary stop25and the lens L11. As described above, the lens L15is disposed at a position relatively away from the stationary stop25where a temperature rises due to the collection of light. Accordingly, the lens L15is less likely to be affected by the heat of the stationary stop25. Therefore, it is possible to avoid a disadvantage that the projection lens11is out of focus due to the thermal deformation of the lens L15. Further, since the lens L15is disposed relatively away from the stationary stop25, an image height is increased in comparison with a case where the lens L15is disposed to be relatively close to the stationary stop25. Accordingly, since on-axis rays and off-axis rays are more dispersed, it is easy to appropriately correct a field curvature and the like.

Furthermore, as shown inFIG.4, the diameter Φ15of the optical surface of the lens L15is set to be larger than the diameter Φ11of the optical surface of the lens L11and is set to be smaller than the diameter Φ16of the optical surface of the lens L16. Moreover, the diameter Φ15of the optical surface of the lens L15is set to be 1.3 to 2 times the diameter Φ11of the optical surface of the lens L11. Accordingly, it is possible to avoid an unnecessary increase in the size of the first holding part20while appropriately correcting a field curvature and the like.

As shown inFIG.5, in a case where the focal length of the lens L15is denoted by f3, |1/f3| is set to be 0.03 or less. Further, as shown inFIG.6, in a case where the focal length of the lens L16is denoted by f2, |1/f3| is set to be smaller than |1/f2|. In a case where the optical power of the lens L15is set to be very low in this way, the out-of-focus can be minimized even if the lens L15is deformed due to heat or the like.

Luminous flux having passed through the lens L15is incident on the lens L16. Then, the intermediate image MI is formed to be closer to the reduction side than the first mirror30, that is, at a position between the lens L16and the first mirror30.

As shown inFIG.2, the distance D1along the first optical axis A1between the lens L11and the first mirror30is set to be longer than the distance D2along the second optical axis A2between the first mirror30and the second mirror31. For this reason, the intermediate image MI can be formed not on the second optical axis A2but on the first optical axis A1. Accordingly, the second optical system L2can be adapted to be more compact than the first optical system L1, and the length of the second optical axis A2, that is, the second holding part21can be shortened. As a result, the size of the projection lens11and eventually the projector10can be reduced.

Luminous flux having passed through the lens L16is bent at an angle of 90° by the first mirror30to form light parallel to the second optical axis A2, and passes through the second optical system L2.

As shown inFIG.4, the diameter Φ21of the optical surface of the lens L21composing the second optical system L2and the diameter Φ22of the optical surface of the lens L22are set to be smaller than the diameter Φ16of the optical surface of the lens L16. The reason for this is that the diameter Φ16of the optical surface of the lens L16is set to be maximum among the diameters of the optical surfaces of the respective lenses composing the first optical system L1and the intermediate image MI is formed on the first optical axis A1by the first optical system L1. Accordingly, even though the diameter Φ21of the optical surface of the lens L21and the diameter Φ22of the optical surface of the lens L22are not increased, an enlarged image having a desired size is obtained. Since the diameter Φ21of the optical surface of the lens L21and the diameter Φ22of the optical surface of the lens L22are set to be smaller than the diameter Φ16of the optical surface of the lens L16, the second holding part21can be further reduced in size.

Luminous flux having passed through the second optical system L2is bent at an angle of 90° again by the second mirror31to form light parallel to the third optical axis A3. Then, the light passes through the third optical system L3and is projected on the screen14as the image P.

As shown inFIGS.2and3, the second holding part21includes one holding frame28that integrally holds the first mirror30and second mirror31. For this reason, component costs and assembly man-hours can be reduced in comparison with a case where the second holding part21includes two holding frames separately holding the first mirror30and the second mirror31.

The projection lens includes the second holding part-fixing mechanism50for fixing the holding frame28(second holding part21) to the first holding part20as shown inFIG.7, and the holding frame28(second holding part21) can be shifted relative to the first holding part20in a case where the fixing force of the second holding part-fixing mechanism50is reduced. Accordingly, after a relative positional relationship between the first optical system L1and the first mirror30is finely adjusted, the second holding part21can be fixed to the first holding part20.

Further, since the second holding part-fixing mechanism50includes the male screws51, the female screws52that engage with the male screws51, and the screw insertion holes53into which the male screws51are inserted, the second holding part21can be easily assembled with the first holding part20.

In the embodiment, the female screws52are formed in the first holding part20and the screw insertion holes53are formed in the holding frame28. However, on the contrary, the screw insertion holes53may be formed in the first holding part20and the female screws52may be formed in the second holding part21. Furthermore, a method of fixing the second holding part21to the first holding part20is not limited to fastening using screws described in the embodiment, and well-known other fixing methods, such as rivets and adhesives, may be employed.

A transmission type image forming panel, which uses a liquid crystal display (LCD) instead of a DMD, may be used as the image forming panel15. Alternatively, a panel using a self light-emitting element, such as a light emitting diode (LED) or organic electro luminescence (EL), instead of a DMD may be used. Alternatively, total reflective type mirrors may be used as the first and second reflective parts instead of specular reflective type first and second mirrors30and31of the embodiment.

An example where a laser light source is used as the light source16has been described in the embodiment, but the disclosure is not limited thereto. A mercury lamp, an LED, and the like may be used as the light source16. Further, the blue laser light source and the yellow phosphor have been used in the embodiment, but the disclosure is not limited thereto. A green phosphor and a red phosphor may be used instead of the yellow phosphor. Furthermore, a green laser light source and a red laser light source may be used instead of the yellow phosphor.

In the technique of the disclosure, the above-mentioned various embodiments and various modification examples can also be appropriately combined. Further, it goes without saying that the disclosure is not limited to the embodiments and can employ various configurations without depart from a gist.

The description contents and shown contents having been described above are the detailed description of portions according to the technique of the disclosure, and are merely an example of the technique of the disclosure. For example, the description of the configuration, functions, actions, and effects having been described above is the description of examples of the configuration, functions, actions, and effects of the portions according to the technique of the disclosure. Accordingly, it goes without saying that unnecessary portions may be deleted or new elements may be added or replaced in the description contents and shown contents described above without departing from the scope of the technique of the disclosure. Further, the description of common technical knowledge and the like, which allow the technique of the disclosure to be embodied and do not need to be particularly described, is omitted in the description contents and shown contents, which have been described above, to avoid complication and to facilitate the understanding of portions according to the technique of the disclosure.

All documents, patent applications, and technical standards disclosed in this specification are incorporated in this specification by reference such that the incorporation of each of the documents, the patent applications, and the technical standards by reference is specific and is as detailed as that in a case where the documents, the patent applications, and the technical standards are described individually.