JP2008026864A - Projection lens unit - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To effectively correct a change in the focal point of a projection lens system due to an increase in temperature with a comparatively easy constitution. <P>SOLUTION: A projection lens system 1A enlarges and projects onto a screen 8, via a plurality of lenses G1 to G16, image light emitted from a light source 4 and modulated by DMDs 3r to 3b. A movable lens barrel 25 holds a lens G16 having positive power, which is positioned closest to the DMDs 3r to 3b. An outer tube 24 holds the movable lens barrel 25 to enable movement in the optical axis direction. Through thermal deformation at the time of an increase in temperature, the bimetal member 27 moves the movable lens barrel 25 in the optical axis direction so as to recede from the image formation devices which are the DMDs 3r to 3b. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a projection lens unit that includes a projection lens system that enlarges and projects image light from an image forming element onto a screen, and a lens barrel that holds a lens of the projection lens system. In particular, the present invention relates to the correction of the focal position of the projection lens system when the temperature rises in the projection lens unit.

  As a projection-type image display device, a projector that includes a reflection-type image forming element such as a DMD (digital micromirror device) and enlarges and projects an image on the image-forming element onto a screen by a projection lens system including a plurality of lenses is known. It has been. In a large projector for a cinema that projects an image on a large screen, a high output light source is used for illumination of the reflective image forming element, and thus the temperature rise of the projection lens system is remarkable. In particular, the temperature rise on the side close to the image forming element in the projection lens system is remarkable. This temperature rise causes a change in the refractive index of the material composing the lens and thermal expansion of the components including the lens, and as a result, the focal position of the projection lens system changes and the image quality of the image projected on the screen may deteriorate. Are known.

  Patent Document 1 discloses a configuration for correcting a change in the focal position of a projection lens system caused by a temperature rise. Specifically, it is disclosed that one lens is held movably in the optical axis direction with respect to the lens barrel, and the focal position is corrected by moving the lens as the temperature rises. Patent Document 1 generally discloses two aspects. In the first aspect, a flange is provided on the outer peripheral edge of the lens, and the lens is moved in the optical axis direction by thermal expansion of the flange. In the second aspect, the lens is moved in the optical axis direction by the thermal expansion member interposed between the flange and the lens barrel.

  However, the configuration disclosed in Patent Document 1 has the following problems. First, since the lens expands in the radial direction as the temperature rises, if there is a difference in the thermal expansion coefficient between the lens and the lens barrel, the lens bites into the lens barrel and the desired amount of movement cannot be obtained. There is also a risk of deformation. In addition, if the gap between the lens barrel and the lens is set large in order to prevent biting, the tilt eccentricity of the lens increases. Further, a complicated atypical lens having a flange on the outer edge is difficult and expensive to manufacture. In particular, in the case of a glass lens, it is difficult to provide a flange. Furthermore, in the configuration of Patent Document 1, only one lens among a plurality of lenses constituting the projection lens system can be moved. As described above, the one disclosed in Patent Document 1 is difficult to effectively correct and has a complicated structure.

  Since the cinema projector described above is required to have high image quality, it has an anomalous dispersion lens having a positive power superior in the correction characteristic of lateral chromatic aberration on the image forming element side than the aperture of the projection lens system. This anomalous dispersion lens having a positive power has a large expansion and a change in refractive index as the temperature rises. However, Patent Document 1 relates to a projection lens system of a projection type image display apparatus having an anomalous dispersion lens having a positive power on the image forming element side with respect to the stop, for optimizing the correction of the focal position as the temperature rises. No teaching is given about the configuration.

Japanese Patent Laid-Open No. 7-209609 (FIGS. 7 and 9)

  It is an object of the present invention to effectively correct a change in the focal position of a projection lens system accompanying a temperature rise with a relatively simple configuration.

  The present invention provides a projection lens unit that includes a projection lens system that enlarges and projects image light from an image forming element onto a screen, and a lens barrel that holds a lens of the projection lens system. A movable barrel that holds one or a plurality of positively arranged lenses arranged on the image forming element side among the lenses of the lens system, and holds the movable barrel movably in the optical axis direction. A projection lens unit comprising: a holding cylinder; and a thermal deformation member made of a bimetal that moves the movable lens barrel in the optical axis direction away from the image forming element by thermal deformation when temperature rises. provide.

  The temperature rise of the projection lens system acts to extend the lens back. The lens back is a distance in the optical axis direction from a lens closest to the image forming element to a focal point of the projection lens system among a plurality of lenses constituting the projection lens system. In other words, the increase in temperature of the projection lens system acts to shift the focus of the projection lens system to the back side of the image forming element. On the other hand, the lens held by the movable barrel moves in the optical axis direction away from the image forming element due to thermal deformation of the thermal deformation member. The movement of the lens held by the movable lens barrel caused by the thermal deformation of the thermal deformation member acts to shift the focal point of the projection lens system to the surface side of the image forming element. Therefore, the shift of the focal position of the projection lens system when the temperature rises can be corrected by moving the movable barrel holding the lens arranged closest to the image forming element by the thermal deformation of the thermal deformation member.

  A lens that is closest to the image forming element in the projection lens system and is likely to increase in temperature is moved by thermal deformation of the thermal deformation member. Further, since the heat deformation member is disposed at a position close to the image forming element, the displacement amount when the temperature rises is large. Accordingly, it is possible to effectively correct the deviation of the focal position of the projection lens system when the temperature rises.

  Since the movable lens barrel holding the lens is moved instead of the lens itself, and the thermal deformation of the heat deformable member made of bimetal is used instead of the thermal expansion of the lens itself, the lens can be caught in the lens barrel or the lens when the temperature rises. No deformation occurs. Further, the lens can be maintained in a state where the lens is tilted with respect to the lens barrel and the eccentricity is small. Furthermore, the lens itself does not need to be an atypical lens provided with a flange or the like, and the structure is simple.

  As described above, according to the present invention, it is possible to effectively correct the shift of the focal position of the projection lens system accompanying the temperature rise with a relatively simple configuration.

  In order to correct lateral chromatic aberration, the projection lens system preferably includes a lens having a positive power and an Abbe number with a large anomalous dispersibility exceeding 70 on the image forming element side of the stop. When the Abbe number of a lens having a positive power is 70 or less, anomalous dispersion is insufficient and correction of lateral chromatic aberration is insufficient. Since the position of the on-axis light and the off-axis light is separated on the image forming element side from the stop to ensure telecentricity as compared with the screen side from the stop, it is suitable for correcting off-axis aberrations. Accordingly, the chromatic aberration of magnification can be effectively corrected by disposing a positive power lens having anomalous dispersion closer to the image forming element than the stop. A lens having anomalous dispersion has a large expansion and refractive index change with a rise in temperature, which is a major cause of fluctuations in the focal position due to a rise in temperature. By moving the lens or the lens group located in the position when the temperature rises, it is possible to effectively correct the shift of the focal position of the projection lens system when the temperature rises.

  The lens or lens group located closest to the image forming element in the projection lens system has positive power, and on-axis light and off-axis light that are approximately parallel to ensure a sufficiently long lens back and telecentricity. Has a function of condensing light mainly on the image forming element. Therefore, if the lens or the lens group located closest to the image forming element is moved, the shift of the focal position can be corrected without changing other aberrations.

  The focal length of the one or more lenses held by the movable lens barrel is preferably set so as to have the following relationship with the air-converted lens back.

  If the power of the lens to be displaced when the temperature rises is excessively small, it is necessary to set a large amount of movement of the lens (movable lens barrel) necessary to correct the focus shift when the temperature rises. The mechanism for correcting the displacement is increased in size. Therefore, it is preferable to set the ratio (f / LBair) of the focal length f of one or more lenses held by the movable lens barrel to the lens back LBair in terms of air is less than 5. On the other hand, if the power of the lens that is displaced when the temperature rises is excessively large, it becomes difficult to ensure the telecentricity of the optical path from the projection lens system to the image forming element, and the lens is displaced to correct the focal position. When this is done, the aberration variation increases. Therefore, the ratio (f / LBair) is preferably set to be larger than 1.

  By setting the number of lenses held by the movable lens barrel to two or less, it is possible to reduce the force required to generate the heat deformation member for displacing the movable lens barrel, and to move the movable lens barrel smoothly.

  When the projection lens system is a zoom lens system, it is preferable that the movable lens barrel is fixed during zooming. By fixing the movable barrel during zooming, the lens closest to the image forming element fixed to the movable barrel is in the same position in any zoom range. Accordingly, it is possible to suppress the effect of the focus position correction at the time of temperature rise from fluctuating depending on the zoom position. In addition, the structure of the projection lens unit can be simplified in that it does not need to be linked with a lens moving mechanism for zooming and a holding tube or a movable lens barrel.

  The projection lens system is preferably a telecentric optical system having an air-converted lens back that is at least twice the diagonal length of the image forming element. The projection lens system has a sufficiently long lens back, that is, a lens back that is at least twice the diagonal length of the image forming element in terms of air. Space can be secured. In addition, by ensuring the telecentricity of the projection lens system, it is possible to prevent a decrease in contrast and color unevenness from occurring in the image light modulated by the image forming element by taking in the illumination light.

  It is preferable that the inner peripheral surface or the outer peripheral surface of the movable barrel is slidably in contact with the holding barrel, and the length in the optical axis direction of the contact portion between the movable barrel and the holding barrel is 15 mm or more. . By providing a sufficient length at the contact portion between the movable barrel and the holding barrel, it is possible to prevent the occurrence of tilt eccentricity due to the fitting between the movable barrel and the holding barrel.

  A heat-deformable member made of bimetal has high heat resistance and is suitable for applications in which a projection lens system such as a large, high-brightness projector becomes hot. In general, since the bimetal is a thin plate metal, the heat capacity can be set small, so that the response speed of the deformation of the heat deformable member to the temperature rise can be increased. Furthermore, the correction amount, that is, the displacement amount when the temperature rises, can be easily set to a desired value by changing the thickness, material, shape, etc. of the bimetal.

  Specifically, the movable barrel and the holding barrel are connected by the bimetal. More specifically, even if the holding cylinder is a lens barrel mounted with a lens positioned on the enlargement side with respect to the lens held by the movable lens barrel, the lens barrel is disposed outside the movable lens barrel. It may be. If the movable lens barrel and the holding tube are connected to the bimetal, the temperature of the movable lens barrel is reduced to the original temperature due to the deformation of the bimetal itself. Return to position. In other words, an urging member such as a spring for returning to the position based on the movable lens barrel is not necessary.

  More specifically, there are a plurality of the bimetals, and each of the bimetals has one end fixed to the movable lens barrel and the other end fixed to the holding tube. Alternatively, there are a plurality of the bimetals, and each of the bimetals has both ends fixed to one of the movable lens barrel and the holding tube, and a central portion fixed to the other of the movable lens barrel and the holding tube. The

  For example, the bimetal has a flat plate shape or a ring shape with a low expansion side. By setting it as this shape, the space required in order to arrange | position a bimetal can be reduced. Moreover, since it is ring-shaped, uniform displacement is generated throughout, and the movable lens barrel holding the lens can be moved without causing tilting eccentricity. Further, if the ring shape is recessed on the low expansion side, the movable lens barrel holding the lens can be moved in the direction approaching the image forming element when the temperature is lowered, so that the focus shift when the temperature is lowered can be corrected.

  Specifically, the lens barrel has an elastic member that presses the movable barrel toward the image forming element side in the optical axis direction, and a reference surface that is integrated with the holding barrel and is perpendicular to the optical axis. The movable lens barrel has a flange portion, the bimetal is disposed between the reference surface and the flange portion, and the elastic member attaches the movable lens barrel to the reference surface via the bimetal. Press.

  The bimetal may have a ring shape with a recessed high expansion side. In this case, the lens barrel is mounted with a lens positioned closer to the enlargement side than the lens held by the holding barrel, and is fixed to the holding barrel, and the movable barrel is connected to the optical axis. An elastic member that presses the screen toward the screen, a reference surface that is integrated with the fixed barrel and is perpendicular to the optical axis, the movable barrel has a flange portion, and the bimetal is the reference The elastic member is disposed between a surface and the flange portion, and presses the movable barrel against the reference surface via the bimetal.

  A rotation stop mechanism that prevents rotation of the movable barrel with respect to the holding cylinder around the optical axis, and is capable of setting a plurality of rotational positions of the movable barrel with respect to the holding cylinder around the optical axis; Is preferred. By changing the rotation position of the movable lens barrel with the rotation stop mechanism, the eccentricity performance of the lens held in the movable lens barrel can be corrected.

  The projection lens unit of the present invention includes a movable lens barrel that holds one or a plurality of lenses having a positive power that is disposed closest to the image forming element, and is a thermal deformation member made of a bimetal at the time of temperature rise. Since the movable barrel is moved in the optical axis direction with respect to the holding barrel by thermal deformation, it is possible to effectively correct the deviation of the focal position of the projection lens system accompanying the temperature rise with a relatively simple configuration. Further, since the heat-deformable member is made of bimetal, it has excellent heat resistance, has a high deformation response speed, and can easily set the correction amount to a desired value by changing the plate thickness, material, shape, and the like.

  Next, embodiments of the present invention will be described in detail with reference to the accompanying drawings.

(First embodiment)
FIG. 1 shows a projection lens system 1A according to a first embodiment of the present invention. The projection lens system 1A constitutes a part of the front projection type projector 2 shown in FIGS. The projection lens system 1A and the lens barrels (the fixed barrel 21, the main barrel 22, and the movable barrel 25) described later that hold the lenses G1 to G16 of the projection lens system 1A constitute a projection lens unit. In addition to the projection lens system 1A, the projector 2 includes DMDs 3r, 3g, and 3b that are reflective image forming elements, a light source 4, an illumination optical system 5, a color separation / combination prism 6, an internal total reflection prism 7, and a screen 8 (FIG. 1).

  In the present embodiment, the light source 4 includes an arc tube 11 and an elliptic reflector 12 which are, for example, xenon lamps. The illumination optical system 5 includes a rod integrator 13 and a relay lens group 14, and light emitted from the light source 4 is irradiated to the DMDs 3 r to 3 b through the illumination optical system 5, the inner surface total reflection prism 7, and the color separation / synthesis prism 6. The image light modulated by the individual DMDs 3r to 3b is incident on the screen 8 through the color separation / synthesis prism 6, the internal total reflection prism 7, and the projection lens system 1A.

  The total internal reflection prism 7 separates the illumination light to the DMDs 3r to 3b and the image light modulated by the DMDs 3r to 3b. The internal total reflection prism 7 is composed of two prisms 7a and 7b, and the illumination light incident from the illumination optical system 5 is totally reflected by an air gap existing at the boundary surface between the two prisms 7a and 7b and guided to the DMDs 3r to 3b. The color separation / combination prism 6 separates the light from the internal total reflection prism 7 into three color (red, green, and blue) color lights and guides them to the DMDs 3r to 3b, and also synthesizes the image light modulated by each DMD 3r to 3b. To do. The image light combined by the color separation / combination prism 6 passes through the air gap of the internal total reflection prism 7 and is enlarged and projected onto the screen 8 by the projection lens system 1A. As described above, in the projector 8, the light beam travels from the DMD 3r to 3b side toward the screen 8, but in the following description, the light beam travels from the screen 8 toward the DMD 3r to 3b side to facilitate understanding. explain.

  The overall configuration of the projection lens system 1A of the first embodiment will be described. As shown in FIG. 1, the projection lens system 1A includes 16 lenses G1 to G16 and a diaphragm 15, and has telecentricity. Between the lens G16 closest to the DMDs 3r to 3b and the DMDs 3r to 3b, an internal total reflection prism 7, a prism 16 which is a color separation / combination prism 6, and a cover glass 17 are interposed. The curvature radii of the lenses G1 to G16, the distance between the upper surfaces of the lens surfaces r1 to r37 of each lens G1 to G16, the refractive indexes N1 to N18, and the Abbe numbers ν1 to ν18 are as shown in Tables 1 and 2 below. is there. In Tables 1 and 2, the positions where a plurality of numerical values are entered in the distance between the top surfaces of the shafts are intervals that change due to zooming, and are in the wide-angle end and the middle region in order (intermediate focal length between the wide-angle end and the telephoto end). The value at the telephoto end is shown.

  The projection lens system 1A includes, in order from the screen 8 side (enlargement side), an optical element group Gr1 having a positive power, an optical element group Gr2 having a negative power, an optical element group Gr3 having a negative power, and a positive power. The optical element group Gr4 is provided. Nine lenses G1 to G9 are arranged on the screen 8 side of the diaphragm 15. Among these lenses G1 to G9, G2, G3, G6 and G9 have positive power, and lenses G1, G4, G5, G7 and G8 have negative power. In particular, the lenses G4, G5, and G7 having negative power are lenses having an Abbe number exceeding 70 with large anomalous dispersion. Seven lenses G10 to G16 are arranged on the DMD 3r to 3b side (reduction side) from the stop 15. Of these lenses, G10, G12, G13, G15 and G16 have positive power, and lenses G11 and G14 have negative power. In particular, the lenses G12, G13, G15, and G16 are lenses having an Abbe number with a large anomalous dispersibility exceeding 70.

  The optical element group Gr1 including the three lenses G1 to G3 closest to the screen 8 is fixed even when the magnification is changed (zooming). The optical element group Gr2 including the three lenses G4 to G6 on the rear side of the optical element group Gr1 is movable in the optical axis direction for changing the magnification. The optical element group Gr3 including the two lenses G7 and G8 on the rear side of the optical element group Gr2 is movable, and in the optical axis direction in order to correct a lens back that varies when the optical element group Gr2 moves. Moving. The optical element group Gr4 including the remaining lenses Gr9 to Gr16, the diaphragm 15, the prism 16, and the cover glass 17 is fixed even when the magnification is changed.

  As shown in Table 3 below, the lens back LB of the projection lens system 1A of the present embodiment is 108.8 mm, and the lens back LBair in terms of air is 78.8 mm. The lens back is the optical axis direction from the lens (lens G16 in this embodiment) closest to the image forming element (DMD in this embodiment) to the focal point of the projection lens system among a plurality of lenses constituting the projection lens system. Distance.

  As described above, the projection lens system 1A of the present embodiment has the lens G12 having positive power closer to the DMDs 3r to 3b than the stop 15 and an Abbe number having a large anomalous dispersibility exceeds 70, and anomalous dispersibility. G13, G15, and G16 are provided. When the Abbe number of these lenses G12, G13, G15, and G16 having positive power is 70 or less, the anomalous dispersion is insufficient, and the correction of the lateral chromatic aberration is insufficient. Further, the lenses G12, G13, G15, and G16 having anomalous dispersion having a positive power are arranged on the DMDs 3r to 3b side from the stop 15 because the DMDs 3r to 3b side from the stop 15 are more than the stop 15. This is because, compared with the screen 8 side, the positions of the on-axis light and the off-axis light are separated in order to ensure telecentricity, which is suitable for correcting off-axis aberrations. In other words, by arranging a positive power lens having anomalous dispersion in the DMDs 3r to 3b from the diaphragm 15, the lateral chromatic aberration can be effectively corrected. FIG. 2 shows the effectiveness of the lenses G1 to G16 of the projection lens system 1A of the present embodiment with respect to lateral chromatic aberration. FIG. 2 also shows that the lenses G12, G13, G15, and G16 having positive power disposed behind the stop 15 contribute particularly to the correction of lateral chromatic aberration.

  However, a lens having anomalous dispersion generally has a larger expansion and refractive index change due to a temperature rise than a lens having a small Abbe number, and this is a major cause of fluctuations in the focal position of the projection lens system due to the temperature rise. . FIG. 3 shows the effectiveness of the lenses G1 to G16 with respect to the fluctuation amount of the lens back LB when the temperature rises by 30 degrees. Also from FIG. 3, it can be seen that the lenses G4, G5, G7, G12, G13, G15, and G16 having anomalous dispersion greatly affect the variation of the focal position at the time of temperature rise. In general, an increase in the temperature of the projection lens system acts to extend the lens back. In other words, the temperature rise of the projection lens system acts to shift the focus of the projection lens system to the back side of the image forming element (DMD in this embodiment).

  As described above, the configuration in which the anomalous dispersion lens having a positive power is arranged behind the diaphragm 15 can effectively correct the lateral chromatic aberration, but the focal position shift (extension of the lens back) when the temperature rises. Inevitable. In the present embodiment, when the temperature rises, the lens G16 located closest to the DMD 3r to 3b among the lenses G1 to G16 constituting the projection lens system 1A is DMD3r to DMD3r through a mechanism that will be described in detail later with reference to FIGS. By moving in a direction away from 3b (a direction in which the focal point of the projection lens system 1A is shifted to the surface side of the DMDs 3r to 3b), the shift of the focal position of the projection lens system 1A when the temperature rises is corrected.

  The reason why the lens G16 located closest to the DMDs 3r to 3b is selected as the lens to be moved when the temperature rises will be described. As apparent from FIG. 1, the lens G16 located closest to the DMD 3r-3b among the lenses constituting the projection lens system 1A has a positive power, and ensures a sufficiently long lens back and telecentricity. In order to achieve this, it has a function of concentrating substantially parallel on-axis light and off-axis light mainly on the DMDs 3r to 3b. Accordingly, by displacing the lens G16, it is possible to correct the deviation of the focal position without changing other aberrations.

  Table 4 shows the design values of the lens back and various aberrations at the telephoto end of the projection lens system 1A, and the focal position and the amount of aberration change when the lenses G14 to G16 are displaced by 0.1 mm to the screen 8 side. Show. When the lens G15 is displaced, the sensitivity of the focal position change amount is low, and the aberration variation is large. Further, when the lens G14 is displaced, the sensitivity of the focal position change amount is high, but the aberration fluctuation is large. On the other hand, when the lens G16 is displaced, the sensitivity of the focal position change amount is high and the aberration variation is relatively small. Table 4 also shows that it is preferable to correct the variation of the focal position when the temperature rises by displacing the lens G16 located closest to the DMDs 3r to 3b.

  As shown in Table 3 above, in the projection lens system 1A of the present embodiment, the air converted lens back LBair is 78.8 mm, whereas the focal length f of the lens G16 is 164.7. The ratio (f / LBair) to the former is set to 2.09 that satisfies the following formula (1).

  If the power of the lens (lens G16 in the present embodiment) that is displaced when the temperature rises is excessively small, it is necessary to set a large amount of lens movement necessary to correct the focus shift when the temperature rises. The mechanism of the projection lens unit including the heat deformation member such as 27 is increased in size. Therefore, it is preferable to set the ratio (f / LBair) of the focal length f of the lens to be moved when the temperature rises to the lens back LBair in terms of air (less than 5). On the other hand, if the power of the lens displaced when the temperature rises is excessively large, it becomes difficult to ensure the telecentricity of the optical path from the projection lens system to the image forming element (DMD 3r to 3b in this embodiment), and the focal position Aberration variation when the lens is displaced to correct for this increases. Therefore, the ratio (f / LBair) is preferably set to be larger than 1. When the lens on the most DMD 3r-3b side of the projection lens system 1A has a function of concentrating substantially parallel on-axis light and off-axis light mainly on the DMD 3r-3b, the type of the projection lens system 1A ( Regardless of power arrangement, group configuration, lens surface shape, etc., it is possible to correct the deviation of the focal position with almost no variation in aberration.

  As shown in Table 3 above, in the projection lens system 1A of the present embodiment, the ratio of the lens back LBair converted to air with respect to the diagonal length of the DMDs 3r to 3b is set to 3.2 that satisfies the following expression (2). is doing.

  Between the rearmost lens G16 of the projection lens system 1A and the DMDs 3r to 3b, a color separation / combination prism 6 and an internal total reflection prism 7 are disposed. Since the projection lens system 1A has a lens back having a sufficient length that is at least twice the diagonal length of the DMDs 3r to 3b as shown in the expression (2), the color separation / synthesis prism 6 and the internal total reflection prism 7 are arranged. Thus, it is possible to secure a sufficient space necessary for capturing the illumination light from the illumination optical system 5 for each of the DMDs 3r to 3b. Moreover, since the projection lens system 1A has telecentricity as described above, it is possible to prevent a decrease in contrast and color unevenness in the image light modulated by the DMDs 3r to 3b by taking in the illumination light from the illumination optical system 5. .

  Next, a mechanism for displacing the lens G16 toward the screen 8 when the temperature rises will be specifically described with reference to FIGS.

  FIG. 7 shows the periphery of four lenses G13 to G16 on the DMD 3r to 3b side among the lenses G1 to G16 of the projection lens system 1A. The fixed lens barrel 21 that holds the lenses G13 to G15, which are lenses positioned on the enlargement side with respect to the lens G16 held by the movable lens barrel 25, includes a flange portion 21a on the front end side, and the flange portion 21a is provided on the main lens barrel 22. It is fixed with screws. Although not shown in FIG. 7, the remaining lenses G <b> 1 to G <b> 12 and the diaphragm 15 are mounted on the main barrel 22. The periphery of the main barrel 22 is covered with a cover 23.

  A flange portion 24 a provided on the front end side of the outer cylinder (holding cylinder) 24 is fixed to the main barrel 22 with screws. A fixed barrel 21 is accommodated in the outer cylinder 24. As described above, since the fixed barrel 21 is fixed to the main barrel 22, the fixed barrel 21 is fixed to the outer cylinder 24 via the main barrel 22. The outer cylinder 24 is interposed between a large diameter portion 24b having a first inner diameter, a small diameter portion 24c having a second inner diameter smaller than the first inner diameter, and an inner surface of the large diameter portion 24b and an inner surface of the small diameter portion 24c. And a reference surface 24d which is a ring-shaped surface perpendicular to the optical axis.

  The movable lens barrel 25 that holds the anomalous dispersion lens G16 having the positive power disposed closest to the DMDs 3r to 3b is fitted in the outer tube 24. The movable lens barrel 25 includes a main body 25a that is open at both ends, a flange portion 25b formed on the front end side of the main body 25a, and a lens holding portion 25c that extends radially inward on the rear end side of the main body 25a. Prepare. The flange portion 25 b is disposed in a cylindrical space defined by the inner peripheral surface of the large diameter portion 24 b of the outer cylinder 24 and the outer peripheral surface of the fixed barrel 21. The main body 25 a of the movable barrel 25 extends between the inner peripheral surface of the small diameter portion 24 c of the outer tube 24 and the outer peripheral surface of the fixed barrel 21 and extends to the rear end side of the outer tube 24. The outer peripheral surface of the main body 25 a of the movable lens barrel 25 is slidably in contact with the inner peripheral surface of the small diameter portion 24 c of the outer tube 24, whereby the movable lens tube 25 is in the optical axis direction with respect to the outer tube 24. Is held movable. There is a gap between the inner peripheral surface of the main body 25a of the movable lens barrel 25 and the outer peripheral surface of the fixed lens barrel 21, and they are not in contact with each other.

  The length in the optical axis direction of the contact portion between the movable lens barrel 25 and the outer tube 24 is preferably 15 mm or more at room temperature. By providing the contact portion between the movable lens barrel 25 and the outer tube 24 with a sufficient length, it is possible to prevent the occurrence of tilt eccentricity caused by fitting the movable lens barrel 25 into the outer tube 24.

  A flat ring-shaped bimetal 27 as shown in FIGS. 8A and 8B is disposed between the reference surface 24 d of the outer cylinder 24 and the flange portion 25 b of the movable lens barrel 25. The bimetal 27 is disposed such that the low expansion side 27a faces the front side (screen 8 side) and the high expansion side 27b faces the rear side (DMDs 3r to 3b). A coil spring 28 is disposed in a compressed state between the flange portion 25 b of the movable lens barrel 25 and the flange portion 21 a of the fixed lens barrel 21. The coil spring 28 elastically biases the movable lens barrel 25 holding the lens G16 to the rear side (DMD 3r to 3b side in the optical axis direction), and the movable lens barrel 25 with respect to the reference surface 24d via the bimetal 27. And has a function of elastically pressing. The movable lens barrel 25 may be biased by elastic means other than the coil spring 28.

  7 and 9, the main body 25a of the movable lens barrel 25 is provided with four slots 25d extending in the optical axis direction at equal angular intervals (90 degree intervals) when viewed from the optical axis direction. The ends of screws 29 screwed into the outer cylinder 24 are inserted into the grooves 25d. The slot 25d and the screw 29 constitute a rotation stop mechanism in the present invention. Since the screw 29 interferes with the side wall of the groove hole 25d, the rotation of the movable lens barrel 25 around the optical axis with respect to the outer cylinder 24 is prevented. Further, if the four screws 29 are loosened and the tip is extracted from the groove 25d, the movable lens barrel 25 can be rotated around the optical axis with respect to the main body 25a. The rotational position of the movable lens barrel 25 around the optical axis relative to the outer cylinder 24 can be set at four locations corresponding to the number of slots 25d. By adjusting the rotational position of the movable lens barrel 25 around the optical axis, the eccentricity performance of the lens G16 held by the movable lens barrel 25 can be corrected. By increasing the number of slots 25d, the settable rotational positions of the movable lens barrel 25 can be increased.

  Due to the temperature rise of the projection lens system 1A due to heat generated by the light source 4 (see FIG. 5), the lens back extends and the focus of the projection lens system 1A shifts to the back side of the DMDs 3r to 3b. On the other hand, when the temperature rises, as shown in FIG. 8C, the ring-shaped bimetal 27 is deformed to increase the thickness. As shown in FIG. 10, when the thickness of the bimetal 27 increases, the flange portion 25 b of the movable lens barrel 25 is pushed forward by the bimetal 27. As a result, the movable lens barrel 25 moves in a direction away from the DMDs 3r to 3b (direction approaching the screen 8) against the elastic biasing force of the coil spring 28, and the lens G16 held by the movable lens barrel 25 also moves in this direction. Move to. This movement of the lens G16 acts to shift the focal point to the surface side of the DMDs 3r to 3b. Therefore, by moving the movable lens barrel 25 (lens G16) by thermal deformation of the bimetal 27, it is possible to correct the shift of the focal position of the projection lens system 1A when the temperature rises. When the temperature drops and the bimetal 27 returns to a flat shape, the movable barrel 25 (lens G16) returns to the initial position shown in FIG. 7 by the elastic biasing force of the coil spring 28.

  Among the plurality of lenses G1 to G16 of the projection lens system 1A, the lens G16 that is closest to the DMD 3r to 3b, that is, at a position close to the light source 4 and is likely to rise in temperature, is moved by thermal deformation of the bimetal 27. Moreover, since the bimetal 27 is disposed at a position close to the light source 4, the displacement amount when the temperature rises is large. Therefore, it is possible to effectively correct the shift of the focal position of the projection lens system 1A when the temperature rises.

  Since the movable lens barrel 25 holding the lens G16 is moved instead of the lens G16 itself, the lens G16 does not bite into the outer tube 24 and other lens barrels when the temperature rises, and the lens G16 is not deformed. The tilt eccentricity with respect to the lens barrel can be kept small. Further, the lens G16 itself does not need to be an atypical lens provided with a flange or the like, and the structure is simple.

  Since the movable lens barrel 25 for moving the lens G16 when the temperature rises is fixed during zooming as described above (see FIG. 1), the lens G16 held by the movable lens barrel 25 is in any zoom range. In the same position. Accordingly, it is possible to reduce the fluctuation of the focus position correction effect due to the temperature rise due to the zoom position. Further, the structure of the projection lens system can be simplified in that it is not necessary to interlock the lens moving mechanism (optical element groups Gr2, Gr3) for zooming with the outer cylinder 24 or the movable lens barrel 25.

  In the present embodiment, the bimetal 27 is used as the heat deformation member as described above. The bimetal 27 has high heat resistance and is suitable for applications in which a projection lens system such as a large and high brightness projector is heated. Further, if the bimetal 27 is employed, the heat capacity can generally be set small, so that the deformation response speed with respect to the temperature rise can be increased.

  As described above, according to the present embodiment, the shift of the focal position of the projection lens system accompanying a temperature rise can be effectively corrected with a relatively simple configuration.

  11 to 14 show alternative mechanisms for moving the lens G16 closest to the DMD 3r-3b to the screen 8 side when the temperature rises.

  In the alternative shown in FIG. 11, the movable lens barrel 25 is fitted on the fixed lens barrel 21. In other words, the fixed barrel 21 functions as a holding cylinder. Specifically, the inner peripheral surface of the main body 25 a of the movable lens barrel 25 is slidably in contact with the outer peripheral surface of the fixed lens barrel 21, whereby the movable lens barrel 25 is in contact with the fixed lens barrel 21. It is held so as to be movable in the optical axis direction. There is a gap between the outer peripheral surface of the main body 25a of the movable barrel 25 and the inner peripheral surface of the outer tube 24, and they are not in contact with each other.

  The alternatives shown in FIGS. 12 to 14 are different from the first embodiment in the form of the bimetal. In this alternative, the surface of the high expansion side 32 a of three arc-shaped bimetals 32 is fixed to a thin ring-shaped base 31. The three arc-shaped bimetals 32 are arranged at equiangular intervals (120 degree intervals) when viewed from the optical axis direction. The surface of each bimetal 32 on the low expansion side 32 b is located on the side opposite to the base 31. A bimetal 32 is disposed between the outer cylinder 24 and the flange portion 25 b of the movable lens barrel 25 with the pedestal 31 in contact with the reference surface 24 d of the outer cylinder 24. As shown in FIG. 14, when the temperature rises, each bimetal 32 is deformed to increase its thickness, so that the movable lens barrel 25 moves away from the DMDs 3 r to 3 b against the urging force of the coil spring 28. In this alternative, the amount of bimetal used can be reduced and the cost can be suppressed as compared with the first embodiment. Further, when the temperature rises, the movable lens barrel 25 can be smoothly moved while reliably preventing the tilt eccentricity. In addition, the shape of the bimetal on a base is not restricted to circular arc shape. For example, a rectangular bimetal may be fixed to the base by welding, caulking, or the like. Further, the number of bimetals on the pedestal is not limited to three, and may be six or eight, for example.

  The bimetal 27 of the first embodiment has a flat ring shape, but the bimetal has a ring shape in which the low expansion side 27a is depressed at room temperature (the bimetal 27 of the first embodiment shown in FIG. 8C is deformed due to temperature rise). It may be the same shape as when). With this shape, not only can the movable lens barrel 25 be moved away from the DMDs 3r-3b when the temperature rises, but also the movable lens barrel 25 can be moved closer to the DMDs 3r-3b when the temperature drops. It is possible to correct the focus shift at the time of decrease.

  15 and 16 show a comparative example different from the present invention in that the thermally deformable member is made of a resin material instead of a bimetal.

In the comparative example of FIG. 15, for example, ultrahigh molecular weight polyethylene (linear expansion coefficient: 17.0 × 10 ⁻⁵ (1 / K)) that reversibly thermally expands as the heat deformable member instead of the combination of the bimetal and the elastic means. ) And the like (thermal expansion member 35) made of a resin material. In the example of FIG. 15, the thermal expansion member 35 has a cylindrical shape, the front end is fixed to the flange portion 25 b of the movable lens barrel 25 by screwing, and the rear end is fixed to the outer tube 24 by screwing. The movable lens barrel 25 is fitted in the outer tube 24 and is held so as to be movable in the optical axis direction. The shape of the thermal expansion member 35 is not limited to a cylindrical shape. For example, the flange of the movable barrel 25 and the outer cylinder 24 may be connected by a plurality of thermal expansion members having an arcuate cross section. When the temperature rises, the thermal expansion member 35 extends to move the movable lens barrel 25 (lens G16) away from the DMDs 3r to 3b, and corrects the deviation of the focal position of the projection lens system 1A. When the temperature returns to room temperature, the thermal expansion member 35 contracts, and the movable lens barrel 25 (lens G16) returns to the initial position shown in FIG. The thermal expansion member 35 is preferably made of a material having a linear expansion coefficient of 10 × 10 ⁻⁵ (1 / K) or more. By using a material having a large linear expansion coefficient, a sufficient amount of movement of the movable lens barrel 25 when the temperature rises can be secured even if the overall length of the thermal expansion member 35 is set to be relatively short. As a result, the thermal expansion member 35 can be reduced in size and the cost can be reduced. The movable lens barrel 25 and the outer cylinder 24 are made of aluminum having a linear expansion coefficient of 2.3 × 10 ⁻⁵ (1 / K), and the temperature of the thermal expansion member 35 is higher than that of the movable lens barrel 25 and the outer cylinder 24. The extension of is sufficiently large.

  In the comparative example of FIG. 16, instead of the combination of the bimetal and the elastic means, a member (heat shrinkable member 36) that reversibly heat shrinks is provided. The heat shrink member 36 has a front end fixed to the outer cylinder 24 by a spring stopper and a rear end fixed to the flange portion 25b of the movable lens barrel 25 by screws. When the temperature rises, the heat shrinkable member 36 contracts to move the movable lens barrel 25 (lens G16) away from the DMDs 3r to 3b, and corrects the focal position shift of the projection lens system 1A. When the temperature returns to room temperature, the heat shrinkable member 36 expands, and the movable lens barrel 25 (lens G16) returns to the initial position shown in FIG.

  The configuration using a bimetal as the heat-deformable member as in the present embodiment is preferable from the configuration described in FIGS. 15 and 16 in the following points. First, a larger displacement can be obtained in a small space. Further, in the configurations of FIGS. 15 and 16, a resin material having a relatively low thermal conductivity must be used. However, in the configuration using the bimetal, in addition to the small heat capacity of the bimetal itself, the thermal conductivity is good. Since a metal lens barrel can be used, heat dissipation is excellent, and the temperature rise of the projection lens unit is relatively suppressed.

(Second Embodiment)
17 and 18 show a projection lens system 1B according to a second embodiment of the present invention. The projection lens system 1B also constitutes a part of the projector 2 similar to the first embodiment, and the light source 4, the illumination optical system 5, the color separation / synthesis prism 6, the internal total reflection prism 7, and the screen 8 are the first embodiment. (See FIGS. 4 to 6).

  The projection lens system 1B includes 16 lenses G1 to G16 and a diaphragm 15, and has telecentricity. The curvature radii of the lenses G1 to G16, the distances between the shaft upper surfaces of the lens surfaces r1 to r39 of each of the lenses G1 to G16, the refractive indexes N1 to N20, and the Abbe numbers ν1 to ν20 are as shown in Tables 5 and 6 below. is there.

  The projection lens system 1A includes, in order from the screen 8 side (enlargement side), an optical element group Gr1 having negative power, an optical element group Gr2 having positive power, an optical element group Gr3 having negative power, and a positive power. The optical element group Gr4 includes a stop 15, an optical element group Gr5 having negative power, and an optical element group Gr6 having positive power. Eight lenses G1 to G8 are arranged on the screen 8 side of the diaphragm 15. Among these lenses G1 to G8, G1, G5, G6, and G8 have positive power, and lenses G2, G3, G4, and G7 have negative power. In particular, the lens G2 having negative power is a lens having an Abbe number with a large anomalous dispersibility exceeding 70. Eight lenses G9 to G16 are arranged on the DMD 3r to 3b side (reduction side) from the stop 15. Of these lenses, G9, G10, G14, and G15 have positive power, and lenses G11 and G12 have negative power. In particular, the lenses G9, G10, G14, and G15 are lenses having an Abbe number with a large anomalous dispersibility exceeding 70.

  The optical element group Gr1 including the five lenses G1 to G5 closest to the screen 8 is fixed during zooming. One lens G6 (optical element group Gr2) on the rear side of the optical element group Gr1 is movable in the optical axis direction for zooming. The optical element group Gr3 including the two lenses G7 and G8 on the rear side of the lens G6 is fixed during zooming. The rear lens G9 (optical element group Gr4) of the optical element group Gr3 and the optical element group Gr5 including the five rear lenses G10 to G14 change when the lens G6 (optical element group Gr2) moves. Move in the direction of the optical axis to adjust the lens back. The optical element group Gr6 including the remaining two lenses G15 and G16, the prism 16, and the cover glass 17 is fixed during zooming.

  FIG. 19 shows the effectiveness of the lenses G1 to G16 of the projection lens system 1B of this embodiment with respect to the chromatic aberration of magnification. FIG. 20 shows the variation of the lens back LB of the lenses G1 to G16 when the temperature rises by 30 degrees. Indicates the effectiveness. From FIGS. 19 and 20, the anomalous dispersion lenses G10, G13, and G14 having a positive power arranged behind the stop 15 contribute to the correction of the chromatic aberration of magnification, while the focal position at the time of the temperature rise. It can be seen that the fluctuation is greatly affected. In the present embodiment, of the lenses G1 to G16 constituting the projection lens system 1B, the two lenses G15 and G16 located closest to the DMDs 3r to 3b are separated from the DMDs 3r to 3b when the temperature rises (in the projection lens system 1A). The shift of the focal position of the projection lens system 1B when the temperature rises is corrected by moving the focal point in the direction in which the focal point is shifted to the surface side of the DMDs 3r to 3b.

  As shown in Table 3 above, the lens back LB of the projection lens system 1B of the present embodiment is 63.5 mm and the lens back LBair converted to air is 49.5 mm, whereas the focal points of the lenses G15 and G16 are 77. .2, which is set to 1.56 that satisfies the above-described equation (1).

  Further, as shown in Table 3 above, in the projection lens system 1B of the present embodiment, the ratio of the lens back LBair converted to air with respect to the diagonal lengths of the DMDs 3r to 3b is 2.0 which satisfies the above-described formula (2). Is set.

  FIG. 18 shows an example of a mechanism for displacing the lenses G15 and G16 toward the screen 8 when the temperature rises. In this example, the outer cylinder 24 includes an annular lid member 37 at the rear end, and the inner surface of the lid member 37 forms a reference surface 37a. The movable lens barrel 25 is fitted in the outer tube 24 so as to be movable in the optical axis direction. Further, the movable lens barrel 25 is provided with a flange portion 25b on the rear end side, and a ring-shaped bimetal 27 similar to that of the first embodiment (see FIG. 7) is disposed between the reference surface 37a and the flange portion 25b. Yes. The coil spring 28 that elastically biases the movable lens barrel 25 is disposed in a compressed state between the front end of the movable lens barrel 25 and the receiving portion 24e provided on the front end side of the outer tube 24. In order to prevent tilting eccentricity, the length in the optical axis direction of the contact portion between the movable lens barrel 25 and the outer tube 24 is preferably 15 mm or more at room temperature.

  Due to the temperature rise of the projection lens system 1B caused by heat generated by the light source 4 (see FIG. 5), the lens back extends and the focus of the projection lens system 1B shifts to the back side of the DMDs 3r to 3b. On the other hand, when the temperature rises, the bimetal 27 is deformed to increase the thickness, so that the movable lens barrel 25 moves away from the DMDs 3r to 3b, and the lenses G15 and G16 held by the movable lens barrel 25 also move in this direction. Move to. The movement of the lenses G15 and G16 acts to shift the focal point of the projection lens system 1B to the surface side of the DMDs 3r to 3b. Therefore, by moving the movable lens barrel 25 (lenses G15 and G16) by thermal deformation of the bimetal 27, it is possible to correct the deviation of the focal position of the projection lens system 1A when the temperature rises.

  Since other configurations and operations of the second embodiment are the same as those of the first embodiment described above, the same elements are denoted by the same reference numerals and description thereof is omitted. The alternative described with reference to FIGS. 11 to 16 can also be applied to the second embodiment.

(Third embodiment)
FIG. 21 shows a projection lens system 1C according to the third embodiment of the present invention. The projection lens system 1C also constitutes a part of the projector 2 similar to the first embodiment, and the light source 4, the illumination optical system 5, the color separation / synthesis prism 6, the internal total reflection prism 7, and the screen 8 are the first embodiment. (See FIGS. 4 to 6).

  The projection lens system 1C includes 17 lenses G1 to G17 and a diaphragm 15, and has telecentricity. The curvature radii of the lenses G1 to G17, the distances between the upper surfaces of the lens surfaces r1 to r39 of each lens G1 to G17, the refractive indexes N1 to N19, and the Abbe numbers ν1 to ν19 are as shown in Tables 7 and 8 below. is there.

  The projection lens system 1A includes, in order from the screen 8 side (enlargement side), an optical element group Gr1 having a positive power, an optical element group Gr2 having a negative power, an optical element group Gr3 having a positive power, and a positive power. The optical element group Gr4 has an optical element group Gr5 having positive power. Eight lenses G1 to G8 are arranged on the screen 8 side of the diaphragm 15. Among these lenses G1 to G8, G2, G3, G6 and G7 have positive power, and lenses G1, G4, G5 and G8 have negative power. In particular, the lens G3 having a positive power and the lenses G4 and G5 having a negative power are lenses having an Abbe number with a large anomalous dispersion exceeding 70. Nine lenses G9 to G17 are arranged on the DMD 3r to 3b side (reduction side) from the stop 15. Among these lenses, G10, G11, G12, G15, G16 and G17 have positive power, and lenses G9, G13 and G14 have negative power. In particular, the lenses G10, G11, G12, G15, G16, and G17 are lenses having an Abbe number with a large anomalous dispersibility exceeding 70.

  The optical element group Gr1 including the three lenses G1 to G3 closest to the screen 8 is fixed during zooming. The optical element group Gr2 including the three lenses G4 to G6 on the rear side of the optical element group Gr1 is movable in the optical axis direction for zooming. The optical element group Gr3 (lenses G7, G8) and the optical element group Gr5 (lenses G9 to G16) on the rear side of the optical element group Gr2 are lens backs that change when the optical element group Gr2 (lenses G4 to G6) moves. In order to correct this, it moves in the optical axis direction. The diaphragm 15 also moves during zooming. The optical element group Gr5 including the remaining lens G17 is fixed during zooming.

  FIG. 22 shows the effectiveness of the lenses G1 to G17 of the projection lens system 1C of this embodiment with respect to the chromatic aberration of magnification. FIG. 23 shows the variation of the lens back LB of the lenses G1 to G16 when the temperature rises by 30 degrees. Indicates the effectiveness. From FIGS. 22 and 23, the anomalous dispersion lenses G10 to G12 and G15 to G17 having a positive power arranged behind the stop 15 contribute to the correction of the lateral chromatic aberration, while increasing the temperature. It can be seen that this greatly affects the variation of the focal position. In this embodiment, among the lenses G1 to G17 constituting the projection lens system 1C, one lens G17 located closest to the DMDs 3r to 3b is oriented away from the DMDs 3r to 3b (the projection lens system 1A is focused on the DMDs 3r to 3b). The shift of the focal position of the projection lens system 1A at the time of temperature rise is corrected by moving in the direction of shifting to the surface side). A specific mechanism for moving the lens G17 when the temperature rises is the same as in the first embodiment (see FIGS. 7 to 10).

  As shown in Table 3 above, the lens back LB of the projection lens system 1C of the present embodiment is 63.5 mm and the lens back LBair converted to air is 49.5 mm, whereas the focal point of the lens G17 is 155.7. And is set to 3.15 that satisfies the above-described equation (1).

  Further, as shown in Table 3 above, in the projection lens system 1C of the present embodiment, the ratio of the lens back LBair converted to air with respect to the diagonal lengths of the DMDs 3r to 3b is 2.0 which satisfies the above formula (2). Is set.

  Since other configurations and operations of the third embodiment are the same as those of the first embodiment described above, the same elements are denoted by the same reference numerals and description thereof is omitted. The alternative described with reference to FIGS. 11 to 16 can also be applied to the third embodiment.

(Fourth embodiment)
FIG. 24 shows a projection lens system 1D according to the fourth embodiment of the present invention. The projection lens system 1D also constitutes a part of the projector 2 similar to the first embodiment, and the light source 4, the illumination optical system 5, the color separation / synthesis prism 6, the internal total reflection prism 7, and the screen 8 are the first embodiment. (See FIGS. 4 to 6). A movable lens barrel 25 that holds a lens G16 that is to be corrected by displacing the position is externally fitted to the fixed lens barrel 21 so as to be movable in the optical axis direction.

  The end surface on the DMD 3r-3b side of the fixed barrel 21 screwed to the main barrel 22 constitutes a reference plane 21b perpendicular to the optical axis. A bimetal 41 is disposed between the reference surface 21 b and the screen side surface of the flange portion 25 b of the movable lens barrel 25. Referring to FIGS. 25A to 25C together, the bimetal 41 has a ring shape in which the high expansion side 41b is recessed from the low expansion side 27a, the low expansion side 27a is the front side (screen 8 side), and high expansion. The side 27b is arranged in a posture facing the rear side (DMD 3r to 3b).

  A coil spring 28 is disposed in a compressed state between a ring-shaped receiving portion 24e projecting inwardly from a surface on the DMD 3r-3b side of the flange portion 25b of the movable barrel 25 and an inner surface of the small diameter portion 24c of the outer tube 24. Has been. The coil spring 28 elastically biases the movable lens barrel 25 holding the lens G16 toward the front side (the screen side in the optical axis direction), and the flange-like portion 25b of the movable lens barrel 25 via the bimetal 41 is a reference surface. It has a function of elastically pressing against 21b. The movable lens barrel 25 may be biased by elastic means other than the coil spring 28.

  When the temperature rises, as shown in FIG. 25C, the bimetal 41 tends to bend to the low expansion side 41a, so that the thickness of the bimetal 41 in the optical axis direction decreases (see symbol t in FIG. 25C). . Since the movable lens barrel 25 is biased to the screen side by the coil spring 28, the movable lens barrel 25 moves to the screen side by an amount corresponding to the thickness reduction amount t of the bimetal 41. As a result, since the lens G16 held in the movable lens barrel 25 also moves in the same direction, it is possible to correct the shift of the focal position when the temperature rises. As the temperature decreases, the bimetal 41 is deformed in a direction in which the thickness increases against the urging force of the coil spring 28, so that the movable lens barrel 25 returns to the initial position.

  In the present embodiment, the structure is simple in that the reference surface 21 b is provided not on the outer cylinder 24 but on the fixed barrel 21. In addition, in order to correct various aberrations such as curvature of field and spherical aberration caused by a manufacturing error of the lens and the lens barrel, when the interval correction washer 42 is inserted between the main lens barrel 22 and the fixed lens barrel 21, it is fixed. In conjunction with the displacement of the lens barrel 21, the movable lens barrel 25 is also displaced in the DMD 3b-3r direction, and the interval between the movable lens barrel 25 and the fixed lens barrel 21 is not changed by the insertion of the interval correction washer 42.

  Since other configurations and operations of the fourth embodiment are the same as those of the first embodiment described above, the same elements are denoted by the same reference numerals and description thereof is omitted.

(Fifth embodiment)
FIG. 26 shows a projection lens system 1E according to the fifth embodiment of the present invention. The projection lens system 1E also constitutes a part of the projector 2 similar to the first embodiment, and the light source 4, the illumination optical system 5, the color separation / synthesis prism 6, the inner surface total reflection prism 7, and the screen 8 are the first embodiment. (See FIGS. 4 to 6). The movable lens barrel 25 that holds the lens G16 that is to be corrected by displacing the position is externally fitted to the fixed lens barrel 21 so as to be movable in the optical axis direction. A gap is provided between the inner peripheral surface of the outer cylinder 24.

  The end surface on the DMD 3r-3b side of the fixed barrel 21 screwed to the main barrel 22 constitutes a reference plane 21b perpendicular to the optical axis. The reference surface 21b and the front side (screen 8 side) surface of the flange portion 25b of the movable lens barrel 25 are connected to each other by three bimetals 61A, 61B, 61C.

  27 and 28 together, the three bimetals 61A to 61C are arranged at equiangular intervals (120 degree intervals) when viewed from the optical axis direction. Each of the bimetals 61A to 61C has the same shape (strip shape when viewed from the optical axis direction), and includes fixing portions 61b and 61c provided with screw holes at both ends of the main body 61a. One fixing portion 61b is fixed to the fixed barrel 21 side by a fixing screw 62A by screwing, and the other fixing portion 61c is fixed to the movable lens barrel 25 side by screwing by a fixing screw 62B. In other words, the bimetals 61A to 61C connect the movable lens barrel 25 and the fixed lens barrel 21 in a manner like a cantilever. The bimetals 61A to 61C are arranged such that the low expansion side 61d faces the front side (the fixed barrel 21 side or the screen 8 side) and the high expansion side 61e faces the rear side (the movable barrel 25 side or the DMDs 3r to 3b). Yes. Unlike the first to fourth embodiments, no elastic means such as a spring for urging the movable lens barrel 25 is provided.

  Due to the temperature rise of the projection lens system 1A caused by heat generated by the light source 4 (see FIG. 5), the lens back extends and the focus of the projection lens system 1E shifts to the back side of the DMDs 3r to 3b. On the other hand, referring to FIGS. 28A and 28B, when the temperature rises, the bimetals 61A to 61B are deformed to reduce the thickness. As a result, as indicated by reference numeral δ in FIG. 28 (B), the movable lens barrel 25 moves to the front side, that is, away from the DMDs 3r to 3b (screen 8), and the lens G16 held by the movable lens barrel 25 is also this. Move in the direction. This movement of the lens G16 acts to shift the focal point to the surface side of the DMDs 3r to 3b. Accordingly, the shift of the focal position of the projection lens system 1A when the temperature rises can be corrected by moving the movable lens barrel 25 (lens G16) by thermal deformation of the bimetals 61A to 61B. When the temperature drops and returns to room temperature, the bimetals 61A to 61B return to their original thickness, so the movable lens barrel 25 moves from the position shown in FIG. Then, the position returns to the position shown in FIG. As a result, the lens G16 held by the movable lens barrel 25 returns to the initial position.

  The alternative of the fifth embodiment shown in FIGS. 29 and 30 is different from the fifth embodiment only in the bimetals 65A, 65B, and 65C. The three bimetals 65A to 65C in this alternative are arranged at equiangular intervals (120 degree intervals) when viewed from the optical axis direction. Each of the bimetals 65A to 65C has the same shape (strip shape when viewed from the optical axis direction), and arm portions 65b and 65c extend obliquely in the same direction from both ends of the central portion 65a provided with the screw holes. Fixing portions 65d and 65e provided with screw holes are provided at the tips of the arm portions 65b and 65c. The central portion 65a is fixed to the movable mirror 25 side by a fixing screw 66A, and the fixing portions 65d and 65e at the ends of the two arm portions 65b and 65c are screwed to the fixed barrel 21 side by fixing screws 66B and 66C, respectively. It is fixed with. In other words, the bimetals 65 </ b> A to 65 </ b> C connect the movable barrel 25 and the fixed barrel 21 in a manner like a doubly supported beam. The bimetals 65A to 65C are arranged such that the low expansion side 65f faces the rear side (the movable lens barrel 25 or DMD 3r to 3b) and the high expansion side 65g faces the front side (the fixed lens barrel 21 side or the screen 8 side). ing.

  When the temperature rises, the bimetals 66A to 66B are deformed and the thickness is reduced. Therefore, as shown in FIG. 30B, the movable barrel 25 holding the lens G16 is away from the front side, that is, away from the DMDs 3r to 3b (screen 8). Moving. As a result, the defocus of the projection lens system 1E due to the extension of the lens back when the temperature rises is corrected. When the temperature drops and returns to room temperature, the bimetals 61A to 61B return to their original thickness, and the movable lens barrel holding the lens G16 returns to the initial position shown in FIG.

  Since the other configuration and operation of the fifth embodiment are the same as those of the fourth embodiment, the same elements are denoted by the same reference numerals and description thereof is omitted.

(Sixth embodiment)
FIG. 31 shows a projection lens system 1F according to the sixth embodiment of the present invention. The projection lens system 1F also constitutes a part of the projector 2 similar to the first embodiment, and the light source 4, the illumination optical system 5, the color separation / synthesis prism 6, the inner surface total reflection prism 7, and the screen 8 are the first embodiment. (See FIGS. 4 to 6). The movable lens barrel 25 that holds the lens G16 that is to be corrected by displacing the position is fitted into the outer tube 24 so as to be movable in the optical axis direction. A gap is provided between the outer peripheral surface of the fixed barrel 25.

  A ring-shaped surface perpendicular to the optical axis that is interposed between the inner surface of the large-diameter portion 24b and the inner surface of the small-diameter portion 24c of the outer cylinder 24 forms a reference surface 24d. The reference surface 24b and the rear surface (DMD 3r-3b side) of the flange portion 25b of the movable lens barrel 25 are connected to each other by three bimetals 161A-161B.

  Referring to FIGS. 32 and 33 together, the bimetals 161A to 161B are the same as those of the fourth embodiment, and one of the fixing parts 161b and 161c at both ends of the main body 161a is fixed to the fixing screw 62A. Thus, the other fixing portion 161c is fixed to the outer cylinder 24 side by a screw with a fixing screw 62B. Contrary to the fourth embodiment, in the bimetals 161A to 161C, the low expansion side 161d is the rear side (the outer cylinder 24 side or DMD 3r to 3b), and the high expansion side 161e is the front side (the movable lens barrel 25 side or the screen 8 side). It is.

  When the temperature rises, the bimetals 161A to 161B are deformed to increase the thickness. Therefore, as shown in FIG. 33B, the movable lens barrel 25 that holds the lens G16 is in the direction away from the front side, that is, the DMDs 3r to 3b (screen 8). Moving. As a result, the defocus of the projection lens system 1E due to the extension of the lens back when the temperature rises is corrected. When the temperature drops and returns to room temperature, the bimetals 161A to 161B return to their original thickness, and the movable lens barrel holding the lens G16 returns to the initial position shown in FIG.

  Since the other configuration and operation of the sixth embodiment are the same as those of the first embodiment, the same elements are denoted by the same reference numerals and description thereof is omitted.

  The alternative of the sixth embodiment of the present invention shown in FIGS. 34 and 35 employs bimetals 165A to 165C similar to the alternative bimetals 65A to 65C of the fifth embodiment described with reference to FIGS. 29 and 30. Only the difference is from the sixth embodiment. Each of the bimetals 165A to 165C includes arm portions 165b and 165c that obliquely extend in the same direction from both ends of the central portion 165a provided with screw holes, and fixed with screw holes provided at the tips of these arm portions 165b and 165c. Portions 165d and 165e are provided. The central portion 165a is fixed to the outer tube 24 side by a fixing screw 66A, and the fixing portions 165d and 165e at the tips of the two arm portions 165b and 165c are screwed to the movable lens barrel 25 side by fixing screws 66B and 66C, respectively. It is fixed with. Contrary to the bimetals 65A to 65C of FIGS. 29 and 30, the low expansion side 165f is the front side (the movable lens barrel 25 side or the screen 8 side), and the high expansion side 165g is the rear side (the outer cylinder 24 or DMC 3r to 3b side). ).

  When the temperature rises, the bimetals 165A to 165B are deformed to increase the thickness. Therefore, as shown in FIG. 35B, the movable lens barrel 25 holding the lens G16 is in the direction away from the front side, that is, the DMDs 3r to 3b (screen 8). Moving. As a result, the defocus of the projection lens system 1E due to the extension of the lens back when the temperature rises is corrected. When the temperature drops and returns to room temperature, the bimetals 165A to 165B return to their original thicknesses, and the movable barrel holding the lens G16 returns to the initial position shown in FIG.

  In the fifth and sixth embodiments and their alternatives, the movable lens barrel 25 and the fixed holding tube (the fixed lens barrel 21 in the fifth embodiment and the outer tube 24 in the sixth embodiment) are bimetals 61A to 61C, 65A to 65C, 161A to 161C, and 165A to 165C are connected, and the movable lens barrel 25 is moved by thermal deformation of these bimetals to correct the focal position when the temperature rises. Therefore, the structure of the projection lens system can be simplified in that it is not necessary to provide an elastic means such as a spring for biasing the movable lens barrel 25 as in the first to fourth embodiments. When resin is used as the thermal expansion member (see FIGS. 15 and 16), the change in the thermal expansion coefficient due to material selection is limited to a certain range, so the correction amount is mainly a correction amount that depends on the length of the thermal expansion member. It is necessary to ensure. On the other hand, when a bimetal is adopted as the thermal expansion member, the displacement amount of the movable lens barrel 25 can be easily changed by changing the plate thickness, material, shape, and the like. Therefore, even when the distance between the movable barrel 25 and the fixed holding barrel is narrow, a relatively large correction amount can be obtained. Even when the present invention is applied to an existing projection lens system, Design changes can be minimized. Furthermore, since the bimetal is a metal, it is significantly superior in terms of heat resistance when used in a high-temperature environment such as a high-brightness projector as compared with a resin material.

Although the present invention has been described by taking a front projection type projector as an example, the present invention can also be applied to a projection lens system of another projection type image display apparatus including a rear projection type projector. The image forming element is not limited to a reflective type such as DMD, and may be a light emitting type such as a CRT or EL element.

1 is a schematic diagram showing a projection lens system of a projector according to a first embodiment of the invention. The graph which shows the effectiveness with respect to the magnification chromatic aberration of each lens which comprises the projection lens system of 1st Embodiment. The graph which shows the effectiveness with respect to the temperature characteristic of each lens which comprises the projection lens system of 1st Embodiment. The schematic diagram which shows the projection lens system of a projector, a color separation prism, an internal total reflection prism, and DMD. The schematic diagram which shows the light source and illumination optical system of a projector. The schematic diagram which shows the projection lens system of a projector, a color separation prism, an internal total reflection prism, and DMD. Sectional drawing which shows the projection lens system (at the time of normal temperature) of 1st Embodiment. 2A shows a bimetal, FIG. 3A is a front view, FIG. 3B is a side view at normal temperature, and FIG. Sectional drawing in the IX-IX line of FIG. Sectional drawing which shows the projection lens system (at the time of a temperature rise) of 1st Embodiment. Sectional drawing which shows the 1st alternative of a projection lens system. Sectional drawing which shows the 2nd alternative (at the time of normal temperature) of a projection lens system. The bimetal in a 2nd alternative is shown, (A) is a front view, (B) is a side view at the time of normal temperature, (C) is a side view at the time of temperature rise. Sectional drawing which shows the 2nd alternative (at the time of a temperature rise) of a projection lens system. Sectional drawing which shows the 1st comparative example of a projection lens system. Sectional drawing which shows the 2nd comparative example of a projection lens system. The schematic diagram which shows the projection lens system of the projector which concerns on 2nd Embodiment of this invention. Sectional drawing which shows the projection lens system of 2nd Embodiment. The graph which shows the effectiveness with respect to the magnification chromatic aberration of each lens which comprises the projection lens system of 2nd Embodiment. The graph which shows the effectiveness with respect to the temperature characteristic of each lens which comprises the projection lens system of 2nd Embodiment. Sectional drawing which shows the projection lens system of the projector of 3rd Embodiment of this invention. The graph which shows the effectiveness with respect to the magnification chromatic aberration of each lens which comprises the projection lens system of 3rd Embodiment. The graph which shows the effectiveness with respect to the temperature characteristic of each lens which comprises the projection lens system of 3rd Embodiment. Sectional drawing which shows the projection lens system of the projector of 4th Embodiment of this invention. The bimetal in 4th Embodiment is shown, (A) is a front view, (B) is a side view at the time of normal temperature, (C) is a side view at the time of temperature rise. Sectional drawing which shows the projection lens system of the projector of 5th Embodiment of this invention. Sectional drawing in the XXVII-XXVII line of FIG. It is an arrow XXVIII view of Drawing 27, (A) shows the time of normal temperature, and (B) shows the time of temperature rise. Sectional drawing similar to FIG. 27 which shows the alternative of 5th Embodiment. It is an arrow XXX figure of FIG. 29, (A) shows the time of normal temperature, (B) shows the time of temperature rise. Sectional drawing which shows the projection lens system of the projector of 6th Embodiment of this invention. Sectional drawing in the XXXII-XXXII line | wire of FIG. It is an arrow XXXIII view of FIG. 32, (A) shows the time of normal temperature, (B) shows the time of temperature rise. Sectional drawing similar to FIG. 27 which shows the alternative of 6th Embodiment. It is an arrow XXXV figure of FIG. 35, (A) shows the time of normal temperature, (B) shows the time of temperature rise.

Explanation of symbols

1A, 1B, 1C, 1D, 1E, 1F Projection lens system 2 Projector 3r, 3g, 3b DMD
4 Light source 5 Illumination optical system 6 Color separation / synthesis prism 7 Internal total reflection prism 8 Screen 11 Arc tube 12 Elliptic reflector 13 Rod integrator 14 Relay lens group 15 Aperture 16 Prism 17 Cover glass 21 Fixed lens barrel 21a Flange portion 21b Reference surface 22 Main Lens barrel 23 Cover 24 Outer cylinder 24a Flange portion 24b Large diameter portion 24c Small diameter portion 24d Reference surface 24e Receiving portion 25 Movable lens barrel 25a Main body 25b Flange portion 25c Lens holding portion 25d Groove holes 27, 32, 41, 61A to 61C, 65A -65C, 161A-161C, 165A-165C Bimetal 27a, 41a Low expansion side 27b, 41b High expansion side 28 Coil spring 29 Screw 31 Base 32a High expansion side 32b Low expansion side 35 Thermal expansion member 36 Thermal contraction member 37 Lid member 3 a Reference surface 61a, 161a Body 61b, 61c, 161b, 161c, Fixing part 61d, 161d Low expansion side 61e, 161e High expansion side 62A, 62B Fixing screw 65a, 165a Central part 65b, 65c, 165b, 165c Arm part 65d, 65e, 165d, 165e Fixing part 65f, 165f Low expansion side 65g, 165g High expansion side 66A, 66B, 66C Fixing screw

Claims (17)

In a projection lens unit that includes a projection lens system that magnifies and projects image light from an image forming element on a screen, and a lens barrel that holds a lens of the projection lens system,
The lens barrel is
A movable lens barrel that holds one or a plurality of lenses having positive power, which is arranged closest to the image forming element among the lenses of the projection lens system;
A holding cylinder that holds the movable barrel movably in the optical axis direction;
A projection lens unit comprising: a thermally deformable member made of a bimetal that moves the movable barrel in the optical axis direction away from the image forming element by thermal deformation when temperature rises. The projection lens system is
Aperture,
2. The projection lens according to claim 1, further comprising: one or a plurality of lenses that are disposed closer to the image forming element than the diaphragm, have a positive power, and have an Abbe number exceeding 70. unit. 2. The focal length of the one or more lenses held by the movable lens barrel is set to have the following relationship with respect to an air-converted lens back: 2. The projection lens unit described.

  The projection lens unit according to claim 1, wherein the movable lens barrel holds two or less lenses.   The projection lens unit according to claim 1, wherein the projection lens system is a zoom lens system, and the movable lens barrel is fixed during zooming.   The projection lens unit according to claim 1, wherein the projection lens unit is a telecentric optical system having an air-converted lens back that is at least twice the diagonal length of the image forming element. An inner peripheral surface or an outer peripheral surface of the movable barrel is slidably in contact with the holding barrel, and a length in the optical axis direction of a contact portion between the movable barrel and the holding barrel is 15 mm or more. The projection lens unit according to claim 1.   The projection lens unit according to claim 1, wherein the movable barrel and the holding barrel are connected by the bimetal.   The projection lens unit according to claim 8, wherein the holding cylinder is a lens barrel on which a lens positioned closer to an enlargement side than a lens held by the movable lens barrel is mounted.   The projection lens unit according to claim 8, wherein the holding cylinder is a lens barrel arranged outside the movable lens barrel.   11. The bimetal according to claim 9, wherein each of the bimetals has one end fixed to the movable lens barrel and the other end fixed to the holding tube. Projection lens unit.   There are a plurality of the bimetals, and each of the bimetals has both ends fixed to one of the movable lens barrel and the holding tube, and a central part fixed to the other of the movable lens barrel and the holding tube. The projection lens unit according to claim 9, wherein the projection lens unit is a projection lens unit.   2. The projection lens unit according to claim 1, wherein the bimetal is a ring shape having a flat or low expansion side. The lens barrel includes an elastic member that presses the movable barrel toward the image forming element side in the optical axis direction, and a reference surface that is integrated with the holding cylinder and is perpendicular to the optical axis.
The movable lens barrel has a flange portion;
The projection according to claim 13, wherein the bimetal is disposed between the reference surface and the flange portion, and the elastic member presses the movable barrel against the reference surface through the bimetal. Lens unit. The projection lens unit according to claim 15, wherein the bimetal has a ring shape in which a high expansion side is recessed.
The projection lens unit according to claim 1, wherein: The lens barrel is mounted with a lens positioned on an enlargement side with respect to a lens held by the movable barrel, and fixed to the holding barrel, and the movable barrel is moved in the optical axis direction. An elastic member that presses toward the screen, a reference surface that is integrated with the fixed barrel and is perpendicular to the optical axis,
The movable lens barrel has a flange portion;
The projection according to claim 15, wherein the bimetal is disposed between the reference surface and the flange portion, and the elastic member presses the movable barrel against the reference surface via the bimetal. Lens unit.   A rotation stop mechanism capable of preventing rotation of the movable barrel around the optical axis relative to the holding barrel and setting a plurality of rotational positions of the movable barrel around the optical axis relative to the holding barrel; The projection lens unit according to any one of claims 1 to 16.

Images