JP2008145580A - Optical system for projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an optical system for projectors which, even if the integrated lighting time of its discharge lump is comparatively short, can provide high-quality video, by preventing flicker phenomenon from occurring. <P>SOLUTION: In the optical system for projectors is provided with a color wheel 3, which color-separates the light from a reflecting mirror 12, which reflects the light radiated from the pair of electrodes 112 of a discharge lump 11, a light source 1 and the color wheel 3 are arranged to have a positional relation, for which Equation 0.30≤θ3/θ1≤1.31 is satisfied, where θ1 represents angle ABC; θ3 represents angle DBE, A represents the center position between the electrodes; B represents an intersection point at which a straight line drawn from the center position A, in the direction of orthogonally crossing the optical axis crosses the reflecting mirror 12; C represents the first focus of the reflecting mirror 12, D represents the second focus of the reflecting mirror 12; and E represents an intersection point, at which the optical axis crosses the vapor-deposition surface of the color wheel 3. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an optical system for a projection apparatus including a color wheel that separates the color of light incident from a light source into light having wavelengths of at least R (red), G (green), and B (blue).

  For example, projection apparatuses represented by projection type projectors are widely used for screening in movie theaters and for presentations in conferences. In recent years, there has been a demand for enjoying cinema viewing on a large screen in each home, and there is a demand for utilizing a projector in a small meeting with a small number of people. There is a strong demand.

  If a digital light processor (DLP: DLP is a registered trademark of Texas Instruments Inc.) system using a digital micromirror device (DMD) is adopted, the illumination optical system can be configured simply, so that the projector can be miniaturized. Can do. Therefore, in recent years, projectors adopting the DLP method are increasing. A projector adopting the DLP method using a DMD element can digitally express images by sequentially rotating the color filter at a high speed by a color wheel.

  FIG. 7 is a diagram schematically showing a conventional projection apparatus provided with a color wheel. FIG. 8 is a front view of the color wheel shown in FIG.

  As shown in FIG. 7, the conventional projector 100 includes a light source 1 including a discharge lamp 11 and an ellipsoidal reflecting mirror 12 that emits radiated light L1 from the discharge lamp 11 as condensed light L2, and a light source. A light guide including a color wheel 3 that separates light incident from 1 into transmitted light L3 having wavelengths of R, G, and B, and a light incident surface 41 on which transmitted light L3 of each color transmitted through the color wheel is incident. 4 and an optical system 60 for a projection apparatus.

  In the conventional projection apparatus 100, the light L1 emitted from the discharge lamp 11 of the light source 1 is reflected by the ellipsoidal reflecting mirror 12 to become the condensed light L2, and the condensed light L2 transmitted through the explosion-proof glass 2 rotates. Through the color filters R, G, and B in the color wheel 3, transmitted light L 3 of red, green, and blue colors is emitted in order at predetermined time intervals, and is emitted onto the light incident surface 41 of the light guide 4. Condensate. The light incident on the inside of the light guide 4 is repeatedly reflected on the side wall 43 inside the light guide 4 to make the cross-sectional illuminance distribution uniform, and is emitted from the light emitting surface 42. The light L4 transmitted through the light guide 4 is refracted by the relay lens 5 (51, 52, 53) and reflected by the relay mirror 6 to illuminate the reflective video device 7. The reflective video device 7 modulates or switches light according to the input video signal of the projection type image display device and reflects the video light L5. The image light L5 is projected onto a screen (not shown) through the projection lens 8, and an enlarged image is projected on the screen.

In the conventional projector 100, the light separated into the R, G, and B colors is sequentially illuminated on the reflective image element 7 by the rotation of the color wheel 3. In synchronization with the color of the color wheel, a video signal corresponding to the color is input to the reflective image element 7. In this way, R, G, and B images are sequentially displayed on the screen. If the color modulation period is sufficiently fast, the observer will recognize it as a full-color image.
JP 2003-222822 A

  However, according to the conventional projection apparatus 100 as described above, it has been found that a so-called flicker phenomenon that causes flickering in an image projected on a screen occurs. Such a flicker phenomenon usually occurs when the discharge lamp 11 as the light source 1 reaches the end of its life, and is caused by the unstable discharge arc formed between the electrodes. Is. Thus, the conventional projector 100 has a problem that the above-described flicker phenomenon occurs although the integrated lighting time of the discharge lamp 11 as the light source 1 is relatively short.

  As described above, although the cumulative lighting time of the discharge lamp 11 of the light source 1 is relatively short, the cause of the flicker phenomenon is not clear, but can be considered as follows.

  FIG. 9 schematically shows a configuration of a projection apparatus optical system mounted on a conventional projection apparatus and conceptually shows an optical path along which light reflected by a color wheel travels. FIG. 9B is an enlarged view of the main part of FIG. In FIG. 9, the solid line indicates the condensed light L2 emitted by the ellipsoidal reflecting mirror, and the broken line indicates the reflected light L6 from the color wheel. FIG. 10 shows the relationship between the spectral intensity and the wavelength of the radiated light L1 from the discharge lamp used in the light source of the conventional optical system for the projection apparatus, and the relationship between the transmittance and the wavelength in the color filter. In FIG. 10, the left side of the vertical axis represents transmittance (unit: percent (%)), the right side of the vertical axis represents the relative value of spectral intensity, the horizontal axis represents wavelength (unit: nanometer (nm)), and the broken line represents radiation from the discharge lamp. The relationship between the spectral intensity of the light L1 and the wavelength, and the solid line indicate the relationship between the light transmittance and the wavelength in the color filter.

As shown in FIG. 9A, the light source 1 of the conventional optical system 60 for a projection apparatus is arranged so as to surround the discharge lamp 11 and the discharge lamp 11, and emits light emitted from the discharge lamp 11. It consists of the ellipsoidal reflecting mirror 12 which condenses. As shown in FIG. 9B, in the discharge lamp 11, a pair of electrodes 112 are arranged opposite to each other inside the arc tube 111, and 0.15 mg / mm ³ or more of mercury as a luminescent substance is enclosed. As shown in FIG. 10, the radiation intensity in the visible wavelength region of 370 nm to 600 nm is large. As shown in FIG. 9B, the pair of electrodes 112 includes a shaft portion 112A and an electrode main body portion 112B formed to have a larger diameter than the shaft portion 112A continuously from the tip of the shaft portion 112A. Each has. At the tip of each electrode main body 112B, a protrusion 112C extending toward the other electrode main body 112B facing each other is formed. The protrusion 112C formed on each electrode body 112B is an essential configuration for forming a discharge arc between the electrode bodies 112B satisfactorily.

  As shown in FIG. 9A, in the projection apparatus optical system 60 mounted on the conventional projection apparatus, the condensed light L2 collected by the ellipsoidal reflecting mirror 12 is incident on the color wheel 3, The R, G, and B colors are incident on the light incident surface 41 of the light guide 4 as transmitted light by the color filter. As shown in FIG. 10, the color filter B that separates blue light transmits light having a wavelength of 400 to 500 nm but does not transmit light in other wavelength regions, and the color filter G that separates green light is The color filter R that separates red light transmits light having a wavelength of 600 nm or more, but does not transmit light in other wavelength regions, but transmits light having a wavelength of 500 to 600 nm but does not transmit light in other wavelength regions. Is.

  Therefore, for example, a part of the light having a wavelength range of 500 nm or more emitted from the discharge lamp is reflected by the color filter B that separates the blue light, so that the reflected light L6 passes through the optical path as shown in FIG. Then, the light source 1 (discharge lamp 11) is irradiated. Then, as shown in FIG. 9B, in the electrode 112 of the discharge lamp 11, the protrusion 112C formed on the distal end side of the electrode main body 112B is irradiated with the reflected light L6, whereby the protrusion 112C becomes hot and melts and deforms. As described above, in order to satisfactorily form a discharge arc between the opposing electrode main body portions 112B, the protruding portion 112C of the electrode main body portion 112B is an essential configuration. Therefore, when the protrusion 112C is melted and deformed, it is considered that the discharge arc formed between the electrode main body portions 112B becomes unstable and the above-described flicker phenomenon is caused.

  As described above, according to the present invention, the flicker phenomenon occurs in the projection apparatus due to the arc becoming unstable although the integrated lighting time of the discharge lamp mounted in the optical system for the projection apparatus is relatively short. Accordingly, it is an object of the present invention to provide an optical system for a projection apparatus that can provide a high-quality image by preventing this.

In order to solve the above-described problems, an optical system for a projection apparatus according to the present invention includes a pair of electrodes arranged in an arc tube, each of an electrode main body and a protrusion provided on the distal end side of the electrode main body. A light source comprising a discharge lamp comprising: a reflector that reflects light emitted from the discharge lamp; and a color of incident light having wavelengths of at least R (red), G (green), and B (blue) An optical system for a projection apparatus, each having a color wheel that separates light;
In the cross-section cut along the plane including the optical axis, the center position between the electrodes is (A), and the intersection point where the straight line drawn from the center position (A) between the electrodes in the direction perpendicular to the optical axis and the reflecting mirror intersect. (B), the first focal point of the reflecting mirror is (C), the second focal point of the reflecting mirror is (D), the intersection point of the optical axis and the color filter of the color wheel is (E), and An angle ABC formed by two straight lines connecting a straight line (AB) connecting (A) and (B) and a straight line (BC) connecting (B) and (C) is θ1, and (B) and (D ) And a straight line (BD) connecting the straight line (BE) connecting (B) and (E), and an angle DBE formed by two straight lines (BE) is θ3,
The light source and the color wheel are arranged to have a positional relationship that satisfies a relationship of 0.30 ≦ θ3 / θ1 ≦ 1.31.

  Furthermore, the optical system for the projection apparatus is characterized in that the θ1 and the θ3 are equal.

  According to the optical system for a projection device of the present invention, since the configuration as described above is provided, the amount of the reflected light beam applied to each of the pair of electrodes is approximately equal. Even though the integrated lighting time is relatively short, it is possible to prevent each projection from melting and deforming, and even if the cumulative lighting time of the discharge lamp is relatively long, the projection continues to maintain the desired shape. This stabilizes the discharge arc. Therefore, in the projection apparatus equipped with the optical system for the projection apparatus of the present invention, the problem that the flicker phenomenon occurs can be solved.

  FIG. 1 is a diagram schematically showing a configuration of an optical system for a projection apparatus according to the present invention. Illustration of the same configuration as that shown in FIG. 7 is omitted. FIG. 2 is a diagram schematically showing the configuration of the electrodes of the discharge lamp among the light sources mounted on the projection apparatus shown in FIG.

  As shown in FIG. 1, the optical system 10 for a projection apparatus according to the present invention includes a light source 1 that emits condensed light L2, and an explosion-proof member 2 that is disposed in a direction in which the condensed light L2 from the light source 1 travels. The light that has passed through the explosion-proof member 2 is incident, and the color wheel 3 that sequentially transmits one of the three colors of red, green, and blue, and the light that is incident on the transmitted light L3 of each color that has passed through the color wheel 3 A light guide 4 having an incident surface 41.

  The light source 1 includes a discharge lamp 11 that emits radiation light L1 and an elliptical reflecting mirror 12 that emits radiation light L1 emitted from the discharge lamp 11 as condensed light L2. The discharge lamp 11 includes a light-emitting tube 111 made of quartz glass or the like, and a pair of electrodes 112 made of tungsten are disposed facing each other in the internal space of the light-emitting tube 111. As shown in FIG. 2, each electrode 112 has a columnar shaft portion 112A and a circle formed so as to have a larger outer diameter than the outer diameter of the shaft portion 112A continuously from the distal end side of the shaft portion 112A. And a columnar electrode body 112B. Projection portions 112C having an outer diameter smaller than the outer diameter of the electrode main body portion 112B and extending toward the other electrode main body portion 112B are formed at the distal end portion of each electrode main body portion 112B. Further, a coil portion 112D is formed on the outer periphery near the rear end of each electrode body portion 112B by winding a tungsten wire.

The ellipsoidal reflecting mirror 12 is made of quartz glass, has a front opening 121 and a rear opening 122 and has a bowl shape as a whole, and a light reflecting surface having a spheroidal shape centered on the optical axis X. It has. On the light reflecting surface 123, for example, a dielectric multilayer film formed by laminating multiple layers of titania (TiO ₂ ) and silica (SiO ₂ ) is formed so as to reflect visible light emitted from the discharge lamp. . A base member 13 made of ceramic having excellent thermal shock resistance and electrical insulation is attached to the neck portion 124 having the rear opening 122 of the ellipsoidal reflecting mirror 12, and one sealing portion 113 of the discharge lamp 11 is attached. A metal base 14 attached to the base member 13 protrudes from the base member 13 to the outside of the ellipsoidal reflecting mirror 12. The material of the ellipsoidal reflecting mirror 12 is not limited to quartz glass, and other glass materials can be used, and metals such as aluminum can also be used.

  The explosion-proof member 2 prevents the fragments of the arc tube 111 or the ellipsoidal reflecting mirror 12 from scattering toward other optical members located in the light emitting direction of the light source in the unlikely event that the discharge lamp 11 is ruptured when the discharge lamp 11 is turned on. For example, it is a plate-like structure made of quartz glass. The explosion-proof member 2 is disposed so as to be inclined with respect to a straight line orthogonal to the optical axis X in order to avoid reflecting the condensed light L2 emitted from the light source toward the discharge lamp.

  As shown in FIG. 8, the color wheel 3 is arranged so that the color filter R that transmits red light, the color filter G that transmits green light, and the color filter B that transmits blue light are sequentially arranged in the circumferential direction. Has been. As will be described later, the color wheel 3 is disposed closer to the light source 1 than the second focal position D of the ellipsoidal reflecting mirror 12. When the color wheel 3 is rotated at a high speed by a predetermined rotation driving means, the color of the transmitted light L3 is sequentially switched to red, green, and blue in synchronization with the rotation of the color filter, and the light incident surface 41 of the light guide 4 is changed. On the other hand, light of each color of red, green and blue is sent.

  The light guide 4 includes an opening serving as a light incident surface 41 on which the transmitted light L3 of each color transmitted through the color wheel 3 is incident, and an opening serving as a light emitting surface 42 that emits light having a uniform cross-sectional illuminance distribution. It has a rectangular cylindrical structure, and an opening serving as a light incident surface 41 is disposed at the second focal position of the ellipsoidal reflecting mirror. The transmitted light L3 of each color transmitted through the color wheel is incident from the light incident surface 41 of the light guide 4, is repeatedly reflected on the inner surface of the side wall 43 of the light guide 4, and is emitted as a light beam L4 having a uniform sectional illuminance distribution. 42.

  FIG. 3 conceptually shows the positional relationship between the light source and the color wheel in the optical system for a projector according to the present invention, and the optical system for a projector 10 is cut by a plane that is orthogonal to the ground and includes the optical axis X. A cross section is shown. In FIG. 3, the discharge lamp and the light guide are not shown.

  In the optical system 10 for a projection apparatus according to the present invention, the center position A between the electrodes of the discharge lamp 11 is arranged closer to the color wheel 3 than the first focal position C of the ellipsoidal reflecting mirror 12, and the color wheel 3 is ellipsoidally reflected. It is arranged closer to the light source 1 than the second focal position D of the mirror 12. The color wheel 3 is disposed closer to the light source 1 than the second focal position D of the ellipsoidal reflecting mirror 12 in order to reduce the light incident surface 41 of the light guide 4 and the second focal position D of the ellipsoidal reflecting mirror 12. This is because it is preferable to dispose the light incident surface 41 of the light guide 4. Note that the color wheel 3 may be disposed closer to the light guide 4 than the second focal position of the ellipsoidal reflecting mirror 12.

  As shown in the cross section of FIG. 3, the optical system 10 for a projection apparatus according to the present invention has a center position between the electrodes of the discharge lamp 11 as A, and is drawn from the center position A between the electrodes in a direction perpendicular to the optical axis X. The intersection point between the straight line and the ellipsoidal reflecting mirror 12 is B, the first focal position of the ellipsoidal reflecting mirror 12 is C, the second focal position of the ellipsoidal reflecting mirror is D, and the optical axis X and color Assuming that an intersection point where the color filter of the wheel 3 intersects is E, an angle ABC (θ1) formed by two straight lines connecting a straight line connecting A and B and a straight line connecting B and C is a straight line connecting B and D, The discharge lamp 11, the ellipsoidal reflecting mirror 12, and the color wheel 3 are arranged so as to be approximately equal to an angle DBE (θ3) formed by two straight lines with a straight line connecting E.

  Here, the center position A between the electrodes of the discharge lamp is determined as follows. As shown in FIG. 2, the shortest straight line K connecting each of the protrusions 112C included in each of the pair of electrodes 112 facing each other is drawn, and the midpoint of the shortest straight line K is set as a center position A between the electrodes.

Further, as shown in FIG. 1, an explosion-proof member 2 made of quartz glass is disposed on the optical path of the light beam L <b> 2 emitted from the light source 1 (between the ellipsoidal reflecting mirror 12 and the color wheel 3). Although not shown in the figure, when the vapor deposition surface is formed on the surface of the color wheel 3 facing the light guide 4, the optical path length is generally longer than in the case where the vapor deposition surface is not formed. Are known. Specifically, when the explosion-proof member 2 is not disposed on the optical path of the light beam L2 emitted from the light source 1 (or when a vapor deposition surface is formed on the surface of the color wheel 3 facing the light source 1). On the contrary, when the explosion-proof member 2 is disposed on the optical path of the light beam L2 emitted from the light source 1 (or the surface of the color wheel 3 facing the light guide 4) It is generally known that ΔR satisfies the relationship of Equation 1 below, where R2 is the optical path length (when a vapor deposition surface is formed) and ΔR (= R2−R1) is the optical path length difference. t is the thickness of the explosion-proof member 2 or the color wheel 3, and n is the refractive index of the explosion-proof member 2 or the color wheel 3.
(Formula 1)
ΔR = (1-1 / n) × t [unit: millimeter (mm)]

That is, when the explosion-proof member 2 is disposed on the optical path of the light beam L2 emitted from the light source 1, the second focal position of the ellipsoidal reflecting mirror 12 is D ', and the optical axis X and the color wheel 3 intersect. On the contrary, when the explosion-proof member 2 is not disposed on the optical path of the light beam L2 emitted from the light source 1, the second focal position of the ellipsoidal reflecting mirror 12 is defined as D and the optical axis is defined as E ′. Assuming that an intersection where X and the color wheel 3 intersect is E, the positions of D and E are determined based on the relationships shown in the following equations 2 and 3.
(Formula 2)
D = D′−ΔR
(Formula 3)
E = E′−ΔR
Further, in the case where the vapor deposition surface of the color wheel is formed on the side facing the light guide, the optical path length elongation due to the thickness of the color wheel is included in ΔR in Equations 2 and 3.

  Specific numerical examples of the positional relationship between the light source 1 and the color wheel 3 in the optical system 10 for a projector according to the present invention are shown below. The distance AC between the center position A between the electrodes of the discharge lamp 11 and the first focal position C of the ellipsoidal reflecting mirror 12 is in the range of 0.01 mm to 0.3 mm. The distance DE between the intersection E where the optical axis X and the color wheel 3 intersect with the second focal position D of the ellipsoidal reflecting mirror 12 is in the range of 0.1 mm to 5 mm.

In addition, the ellipsoidal reflecting mirror 12 of the optical system 10 for a projector according to the present invention is manufactured by molding quartz glass or metal with a mold or the like so as to have a predetermined shape. However, the actually manufactured ellipsoidal reflector may be slightly different from the designed ellipsoidal reflector 12 in, for example, the first focal position C. Therefore, the above θ1 and θ3 are not only in the case where the values of both angles completely match in consideration of the production error in the ellipsoidal reflecting mirror 12, but also in the case where the condition of the following Expression 4 is satisfied. Including. The inventors of the present invention have confirmed that it is possible to avoid melting and deformation of the protrusion 112C provided on the electrode main body by satisfying the numerical value range of Expression 4 by performing an experiment described later.
(Formula 4)
0.30 ≦ θ3 / θ1 ≦ 1.31

  FIG. 4 conceptually shows an optical path in which light reflected by the color filter travels toward the light source without passing through the color filter in the optical system for a projection apparatus of the present invention. In FIG. 4, the solid line indicates the condensed light L2 emitted from the ellipsoidal reflecting mirror 12, and the broken line indicates the reflected light L6 from the color wheel.

  According to the optical system 10 for a projection apparatus of the present invention, the light source 1 and the color wheel 3 are arranged so as to satisfy the positional relationship in which the above θ1 and θ3 are substantially equal, so as shown in FIG. The reflected light L6 reflected by the color filters R, G, and B returns to the discharge arc formed between the pair of electrodes 112 facing each other in the arc tube 111 of the discharge lamp 11, and is provided in each electrode main body 112B. The projections 112C thus formed are not irradiated. Therefore, it is possible to suppress the occurrence of a problem that the protrusion 112C provided on each electrode main body 112B is melted and deformed even though the integrated lighting time of the discharge lamp 11 is relatively short. As a result, even when the cumulative lighting time of the discharge lamp 11 is relatively long, the discharge arc is stabilized by keeping the respective projections 112C maintaining their intended shapes, and thus the problem of causing a flicker phenomenon in the projection apparatus. Can be resolved. The reason is considered as follows.

  FIG. 5 conceptually shows the reason why the effect of the optical system for a projection apparatus of the present invention is obtained. The solid line indicates the path of the light beam emitted from A when the center position A between the electrodes of the discharge lamp 11 coincides with the first focal point C of the ellipsoidal reflecting mirror 12, and the broken line indicates the electrode of the discharge lamp 11. In the case where the center position A is spaced from the first focal point C of the ellipsoidal reflecting mirror 12, the path of the light beam emitted from A is shown. M is a tangent drawn so as to contact the ellipsoidal reflecting mirror 12 at point B on the ellipsoidal reflecting mirror 12, and N is a normal line orthogonal to the tangent M.

  As indicated by the solid line in FIG. 5, when the center position A between the electrodes of the discharge lamp 11 coincides with the first focal position C, the light beam L1 emitted from the first focal position C is reflected on the ellipsoid. The condensed light L2 that is incident on the mirror 12 so that the incident angle is CBN and is reflected by the ellipsoidal reflecting mirror 12 so as to have a reflection angle NBD equal to the incident angle CBN is condensed at the second focal position D. .

  On the other hand, when the center position A between the electrodes of the discharge lamp 11 is arranged closer to the color wheel 3 than the first focal position C as shown by the broken line in FIG. The incident light ray L1 ′ is incident on the ellipsoidal reflector 12 so that the incident angle is ABN, and the condensed light L2 ′ reflected by the ellipsoidal reflector 12 so as to have a reflection angle NBE equal to the incident angle ABN is emitted. Is done. Here, the condensed light L2 ′ indicated by a broken line has a smaller incident angle ABN by an amount corresponding to the angle ABC than the incident angle CBN. Therefore, the reflected angle NBE also has the reflected angle NBD. Is smaller by an amount corresponding to the angle ABC, and is condensed at a position E closer to the light source 1 than the second focal position D of the ellipsoidal reflecting mirror 12.

Therefore, in the optical system for a projector according to the present invention, the angle ABC is larger than the position E where the condensed light L2 ′ is collected (that is, the second focal position D of the ellipsoidal reflecting mirror 12). By disposing the vapor deposition surface of the color wheel 3 at a position corresponding to the light source 1 by a corresponding amount, the condensed light L2 ′ emitted from the ellipsoidal reflecting mirror 12 is incident on the color wheel 3 at an incident angle BEX. In addition, the light beam L6 reflected by the color wheel 3 so as to have a reflection angle FEX equal to the incident angle BEX is collected at the center position A between the electrodes. As a result, in the optical system for a projection apparatus according to the present invention, one of the protrusions 112C provided on the pair of electrodes 112 is not irradiated with the light beam L6 in a biased manner, and each of the protrusions 112C. It is considered that the risk of melting and deformation can be eliminated.
As described above, in the optical system for a projection apparatus according to the present invention, each projection 112C continues to maintain the desired shape and the discharge arc is stabilized, so that the problem of flicker phenomenon occurring in the projection apparatus can be solved. It is considered possible.

<Experimental example 1>
Below, the 1st experiment example performed in order to confirm the effect of this invention is demonstrated.
An optical system for a projection apparatus according to an example of the present invention was produced according to the configuration shown in FIG. In this optical system for a projection apparatus, the center position between the electrodes of the discharge lamp is A, and the intersection point where the straight line drawn in the direction orthogonal to the optical axis X from the center position A between the electrodes and the ellipsoidal reflector intersects B. Where the first focal point of the ellipsoidal reflector is C, the second focal point of the ellipsoidal reflector is D, and the intersection point of the optical axis X and the color wheel is E, and the straight line connecting A and B and B And the value of the angle ABC (θ1) formed by two straight lines connecting the straight lines connecting C and C and the value of the angle DBE (θ3) formed by two straight lines connecting the straight lines connecting B and D and B and E substantially coincide with each other. The discharge lamp 11, the ellipsoidal reflecting mirror 12, and the color wheel 3 are arranged so as to do so.

The optical system for a projection apparatus according to the example has the following specifications.
The ellipsoidal reflecting mirror 12 has a first focal length of 8.1 mm and a second focal length of 64.1 mm. In the discharge lamp 11, 0.16 mg / mm ³ of mercury is enclosed in the arc tube 111, and the distance between the electrodes is 1.0 mm. The explosion-proof glass 2 intersects with the optical axis X in a state where the explosion-proof glass 2 is inclined by 10 ° with respect to a straight line orthogonal to the optical axis X at a position 15.8 mm away from the front opening 121 of the ellipsoidal reflecting mirror 12 with a thickness of 2.8 mm. It is arranged as follows. The color wheel 3 is disposed so that the vapor deposition surface is perpendicular to the optical axis X on the light source side at a position 26.6 mm away from the front opening 121 of the ellipsoidal reflecting mirror 12. The distance AC between the center position A between the electrodes of the discharge lamp 11 and the first focal position C of the ellipsoidal reflecting mirror 12 is 0.1 mm. The distance DE between the intersection point E where the optical axis X and the color wheel 3 intersect with the second focal position D of the ellipsoidal reflector is 1.3 mm. In the optical system for the projection apparatus of the example, the angle ABC (θ1) is 0.396 ° and the angle DBE (θ3) is 0.304 °, and the value of θ1 and the value of θ3 are almost the same.

  Three types of optical systems for the projection apparatus according to the comparative example having the same configuration and specifications as those of the optical system for the projection apparatus according to the above-described example are manufactured except that the value of the angle DBE (θ3) is different. In the optical system for the projection apparatus of Comparative Example 1, θ3 is 0.05 °. In the optical system for a projection apparatus of Comparative Example 2, θ3 is 0.57 °. In the optical system for the projection apparatus of Comparative Example 3, θ3 is 0.84. That is, the optical system for the projection apparatus of Comparative Examples 1 to 3 is different from the optical system for the projection apparatus in the example in which the value of θ1 and the value of θ3 substantially match, and the value of θ1 and the value of θ3 are greatly different. ing.

  Regarding the optical system for the projection apparatus of the above-described embodiment and the optical system for the projection apparatus of Comparative Examples 1 to 3, a light receiving device using an optical fiber is disposed outside the discharge lamp so as to receive the light incident on the electrode, Of the reflected light L6 reflected in the direction of the discharge lamp 11 by the color filters R, G, and B, an electrode (front electrode) located on the front opening 121 side of the elliptical reflecting mirror 12 and the ellipsoidal reflecting mirror 12 The amount of light beam applied to the electrode located on the rear opening 122 side (rear electrode) was measured. The result is shown in FIG.

  FIG. 6 is a diagram illustrating the relationship between the relative value of the amount of light beam applied to the electrode 112 and the angle DBE (θ3) when the total amount of light beam L1 from the discharge lamp 11 is 1. In FIG. 6, the vertical axis represents the relative value of the amount of light beam applied to the electrode 112, and the horizontal axis represents the value of the angle DBE (θ3) (unit: ° (degrees)). In FIG. 6, the solid line indicates the relative value of the light flux applied to the front electrode, and the broken line indicates the relative value of the light flux applied to the rear electrode.

  As shown in FIG. 6, in the optical system for the projection apparatus of Comparative Example 1, the relative value of the amount of light beam applied to the front electrode was 0.024, whereas the rear electrode was irradiated. The relative value of the luminous flux was 0.107. Further, in the optical system for the projection apparatus of Comparative Example 2, the relative value of the luminous flux irradiated to the front electrode was 0.108, whereas the relative value of the luminous flux irradiated to the rear electrode. Was 0.031. Furthermore, in the optical system for the projection apparatus of Comparative Example 3, the relative value of the light flux irradiated to the front electrode was 0.160, whereas the relative value of the light flux irradiated to the rear electrode. Was 0.013.

  As shown in the experimental results, according to the optical system for the projection apparatus of Comparative Examples 1 to 3 in which the value of θ1 and the value of θ3 are greatly different, either the front electrode or the rear electrode is irradiated. Since the amount of reflected light L6 is large, there is a risk that the protrusions provided on any of the opposing electrode main body portions melt and deform, and the discharge arc formed between the electrodes of the discharge lamp is unstable. It is considered that the risk of becoming a problem cannot be resolved. Therefore, it is considered that the problem that the flicker phenomenon occurs cannot be solved in the projection apparatus equipped with the optical system for the projection apparatus of Comparative Examples 1 to 3.

  On the other hand, in the optical system for a projection apparatus according to the example, the relative values of the light flux applied to the front electrode and the light flux applied to the rear electrode were both about 0.05. As shown in the experimental results, according to the optical system for the projection apparatus of the example in which the value of θ1 and the value of θ3 substantially coincide with each other, the reflected light is applied to either the front side electrode or the rear side electrode. Since L6 is not irradiated unevenly and the amount of light beam irradiated to each electrode is uniform, there is a possibility that the protrusion provided on one of the opposing electrode main body portions melts and deforms. It is considered that the possibility that the discharge arc formed between the electrodes of the discharge lamp becomes unstable can be eliminated. Therefore, it is considered that the problem that causes the flicker phenomenon can be solved in the projection apparatus equipped with the optical system for the projection apparatus of the embodiment.

<Experimental example 2>
Below, the 2nd experiment example performed in order to confirm the effect of this invention is demonstrated. Except for the numerical value of the angle DBE (θ3), six types of optical systems for projectors (referred to as Examples 1 to 6) having the same configuration and specifications as those of Experimental Example 1 were produced, 60 in total, 60 in total. As shown in Table 1 below, each of the optical systems for the projection apparatus of Examples 1 to 6 has a common value of θ1 of 0.396, but the value of θ3 is 0.05, 0.12, 0. .30, 0.52, 0.57, and 0.84, respectively.

  For each of the optical systems for the projection apparatus of Examples 1 to 6, the discharge lamp 11 was turned on for a predetermined time, and then it was visually confirmed whether or not the protrusion 112C provided on the electrode 112 was melted and deformed. The results are shown in Table 1.

  In Table 1, “◯” indicates that the protrusion 112C was not melted and deformed, and “X” indicates that the protrusion 112C was melted and deformed. As shown in Table 1, in the projection apparatus optical systems of Examples 2 to 4 in which the value of θ3 / θ1 is within the range of the above-described Expression 4, the protrusion 112C provided on the electrode 112 is melt-deformed. There was no. On the other hand, in the optical systems for projection apparatuses of Examples 1, 5, and 6 in which the value of θ3 / θ1 is outside the range of Expression 4, the projection 112C provided on the electrode 112 is melted and deformed. From this experimental result, in the optical system for a projection apparatus in which the value of θ3 / θ1 is within the range of Equation 4, the amount of the reflected light beam L6 irradiated to each of the pair of electrodes 112 is approximately equal. It is considered that the protrusion 112C did not melt and deform. On the other hand, in the optical system for a projection apparatus in which the value of θ3 / θ1 is outside the range of Expression 4, the amount of the reflected light beam L6 irradiated to any one of the electrodes is biased, so that the projection 112C is It is thought to have melted and deformed.

  The configuration that is not essential in the optical system for a projection apparatus according to the present invention is not limited to the configuration described above, and can be changed as appropriate. For example, the reflecting mirror provided in the light source is not limited to the ellipsoidal reflecting mirror, and a parabolic reflecting mirror that reflects the emitted light from the discharge lamp as light parallel to the optical axis of the reflecting mirror can also be used. When a parabolic reflector is used as the light source, an optical member such as a lens is placed on the optical path along which the reflected light emitted from the parabolic reflector travels, and is emitted from the parabolic reflector. The parallel light is condensed on the light incident surface of the light guide.

It is a figure which shows schematically the structure of the optical system for projectors of this invention. It is a figure which shows schematically the structure of the electrode of a discharge lamp among the light sources of the optical system for projectors shown by FIG. It is a figure which shows notionally the positional relationship of the light source and color wheel in the optical system for projectors of this invention. It is a figure which shows notionally the optical path which the light reflected by the color filter travels toward a light source in the optical system for projectors of this invention. It is a figure which shows notionally the reason why the effect which concerns on the optical system for projectors of this invention is acquired. It is a figure which shows the result of the experiment conducted in order to confirm the effect of this invention. It is a figure which shows schematically the structure of the conventional projection apparatus. It is a front view of the color wheel with which the optical system for projectors shown by FIG. 7 is provided. It is a figure which shows notionally the optical path which the light reflected by the color wheel travels while showing a structure schematically about the optical system for projectors mounted in the conventional projector. It is a figure which shows about the relationship of the light transmittance and wavelength in a color filter, and the light transmittance from a discharge lamp about the discharge lamp and color filter with which the conventional optical system for projectors is provided.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Light source 11 Discharge lamp 111 Light-emitting tube 112 Electrode 112A Shaft part 112B Electrode main body part 112C Protrusion part 112D Coil part 12 Elliptical reflector 121 Front side opening 122 Rear side opening 2 Explosion-proof glass 3 Color wheel R Color filter G Color filter B Color Filter 4 Light guide 41 Light incident surface 42 Light exit surface 43 Side wall 5 Relay lens 6 Relay mirror 7 Reflective image element 8 Projection type image display device A Center position between electrodes of discharge lamp B From center position between electrodes to optical axis Intersection C where the straight line drawn in the orthogonal direction intersects with the ellipsoidal reflecting mirror C First focal position D of the elliptical reflecting mirror Second focal position E of the ellipsoidal reflecting mirror Intersection X where the optical axis and the color wheel intersect

Claims (2)

Each of the pair of electrodes arranged in the arc tube includes a discharge lamp including an electrode main body portion and a protrusion provided on the tip side of the electrode main body portion, and a reflecting mirror that reflects light emitted from the discharge lamp. An optical system for a projection apparatus, comprising: a light source comprising: a color wheel that separates the color of incident light into light having wavelengths of at least R (red), G (green), and B (blue). ,
In the cross-section cut along the plane including the optical axis, the center position between the electrodes is (A), and the intersection point where the straight line drawn from the center position (A) between the electrodes in the direction perpendicular to the optical axis and the reflecting mirror intersect. (B), the first focal point of the reflecting mirror is (C), the second focal point of the reflecting mirror is (D), the intersection point of the optical axis and the color filter of the color wheel is (E), and An angle ABC formed by two straight lines connecting a straight line (AB) connecting (A) and (B) and a straight line (BC) connecting (B) and (C) is θ1, and (B) and (D ) And a straight line (BD) connecting the straight line (BE) connecting (B) and (E), and an angle DBE formed by two straight lines (BE) is θ3,
An optical system for a projection apparatus, wherein the light source and the color wheel are arranged so as to satisfy a relationship of 0.30 ≦ θ3 / θ1 ≦ 1.31.   The optical system for a projection apparatus according to claim 1, wherein the optical system for the projection apparatus has the same θ1 and θ3.

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