JP2018031932A - Optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a projection type image display device having high performance and high quality, which is always in focus in the whole area of an image even when temperature elevation occurs in an optical element and an optical element holding member of a lens unit and even when a projected image moves by a shift mechanism.SOLUTION: Temperature detection means is disposed in a projection type image display device; and the image display device has a focus position correction mechanism that interlocks with changes in the curvature of an image plane caused by temperature elevation in an optical element and an optical element holding member of a lens unit and that automatically moves a focus group in such a manner that the whole area of a projected image is always within the depth of focus. The device also includes a shift mechanism that moves a projected image; and the shift mechanism has shift position detection means. In this configuration, a correction amount by the focus position correction mechanism is changed in accordance with information from the temperature detection means and the shift position detection means.SELECTED DRAWING: Figure 6

Description

  The present invention relates to an optical apparatus having a lens unit having a mechanism for correcting a focal position variation caused by a field curvature variation.

  As an optical device, light from a light source is converted into an image by various modulation devices such as a liquid crystal panel and a DMD, and the image is enlarged and projected by focusing on a projection surface such as a screen by a lens unit composed of a plurality of optical elements. Projection-type image display devices such as projectors are known. Since the lens unit always has a curvature of field, the focal position of the image is displaced between the optical axis of the lens unit and the peripheral portion. If the shift of the focal position exceeds the depth, a part of the image is out of focus, which is a problem.

  In order to avoid this problem, the precision of the parts is strictly controlled and the deviation of the focal position does not exceed the depth by adjustment during assembly. However, many projection-type image display devices that have a shift mechanism and can move a projected image use almost the entire image circle of the lens unit. For this reason, in order to prevent the deviation of the focal position from exceeding the depth, it is necessary to cope with the depth not exceeding the entire depth of the image circle.

  However, strict control of component accuracy and adjustment during assembly so that the depth does not exceed almost the entire image circle of the lens unit is required compared to the case where there is no shift mechanism and only a part of the image circle is used. It becomes very difficult to realize. For this reason, the projection type image display apparatus having the shift mechanism cannot cope with the deviation of the focal position so as not to exceed the depth, which sometimes causes a problem. In order to solve this problem, a technique is known in which the image deterioration is avoided by moving at least one optical element held by the lens unit in accordance with the movement of the projected image by the shift mechanism.

  For example, in Patent Document 1, when at least one optical element of the lens unit is moved in parallel to the image plane by a shift operation, the other optical elements move differently from the at least one optical element in conjunction with the shift. A technique for improving the imaging performance is known.

  The lens unit includes a plurality of optical elements and an optical element holding member that holds the optical element, and moves the focal position of the image by moving at least one of the optical element holding members. I can do it. Since the optical element and the optical element holding member of the lens unit always receive light while the light source of the projection type image display apparatus is lit, the temperature rises in the optical element and the optical element holding member. The optical element changes in optical characteristics such as refractive index due to the temperature rise, and the optical element holding member undergoes linear expansion due to the temperature rise, and the interval between the optical elements changes.

  The focal position moves from the projection surface such as a screen by the change in the characteristics and the interval of the optical element. If the movement of the focal position exceeds the depth, it causes a problem as image degradation. To solve this problem, a technique is known in which the focal position is corrected in accordance with the movement of the focal position to avoid deterioration of the projected image.

  For example, in Patent Document 2, temperature detection means is arranged in a projection type image display device, and the focus position is corrected based on a predetermined focus position adjustment algorithm and the detection result of the temperature detection means to avoid deterioration of the projected image. Technology is disclosed.

Japanese Patent Publication No. 60-2645 JP 2000-19648 A

  A change in the field curvature of the lens unit is also caused by a change in the characteristics and spacing of the optical element as the temperature of the optical element and the optical element holding member increases. Due to the change in the curvature of field, a shift in the focal position between the optical axis of the projected image and the peripheral portion occurs. If the shift of the focal position exceeds the depth due to the change of the shift of the focal position, a part of the image is out of focus, which is a problem.

  However, Patent Document 1 is a technique in which a part of the optical element moves so as to improve the imaging performance in conjunction with the shift operation, and the curvature of field due to the temperature rise of the optical element and the optical element holding member. The change cannot be corrected.

  Further, Patent Document 2 is a technique for determining the correction amount from the information of the temperature detection means, and the movement amount of the focal position that differs depending on the shift position cannot be corrected. In recent projection type image display devices, since the brightness has increased and the characteristics of the optical element and the change in the spacing due to the temperature rise are remarkable, the amount of deviation between the optical axis and the focal position of the peripheral part is significant, and therefore one of the images The part easily goes out of depth. In addition, if the depth becomes shallow due to high resolution and miniaturization of various modulation devices, if the optical axis and the focal position shift due to changes in the characteristics of the optical element due to temperature rise and the focal position of the periphery, part of the image Can easily get out of depth.

  Because of these requirements, measures against field curvature fluctuations are essential. Further, in the wide-angle type lens unit, generally, the change in the curvature of field due to the change in the characteristics of the preschool element and the change in the distance is more remarkable, and the countermeasure is further important.

  Accordingly, in the present invention, when the optical element of the lens unit and the optical element holding member change in curvature of field due to a temperature rise, a projection type image display that can always provide a good image at any shift position. An object is to provide an apparatus.

To achieve the above objective,
In the present invention, the temperature detecting means is arranged in the projection type image display device, and the entire projected image is focused so that the entire depth is within the depth in conjunction with the change in field curvature due to the temperature rise of the optical element of the lens unit and the optical element holding member. It has a focal position correction mechanism that automatically moves the group. In addition, it has a shift mechanism for moving the projected image, and the shift mechanism has a shift position detecting means. In this configuration, the correction amount of the focal position correction mechanism is changed according to the information of the temperature detection means and the shift position detection means.

  According to the present invention, regardless of the type of the lens unit, when the temperature rises in the optical element and the optical element holding member of the lens unit and when the projected image is moved by the shift mechanism, the entire image is always in focus. It becomes possible to be in a state. As a result, it is possible to always provide a high-performance and high-quality projection image display apparatus.

1 is an external view of a liquid crystal projector that is Embodiment 1 of the present invention. FIG. FIG. 3 is a side view showing an optical configuration of the liquid crystal projector of Example 1. FIG. 3 is an exploded perspective view of the lens unit according to the first embodiment. FIG. 3 is an exploded external view of the motor unit according to the first embodiment. FIG. 3 is an external view of a shift unit according to the first embodiment. FIG. 3 is a block diagram of a focal position correction mechanism according to the first embodiment. FIG. 3 is a focus position correction algorithm according to the first embodiment. FIG.

[Example 1]
FIG. 1 shows an appearance of a projector 500 that includes a lens unit 100, a shift unit 300, a temperature sensor, a color separation / combination unit 200, and an illumination optical system 203 according to the first embodiment of the present invention.

  An optical box containing a light source lamp 209, a color separation / combination unit 200, an illumination optical system 201, and light modulation elements 206R, 206G, and 206B such as a liquid crystal panel is housed in the housing of the projector 500. A lens unit 100 and a shift unit 300 are attached to the light emitting portion of the optical box. The lens unit 100 projects an image onto a projection surface (not shown) such as a screen or a wall through an opening formed on the front surface of the housing. The shift unit 300 holds the lens unit 100 so as to shift in a plane orthogonal to the optical axis of the lens unit 100.

  By shifting the lens unit 100 with respect to the light emitting portion of the optical box by the shift unit 300, the projection light projected from the lens unit 100 can be shifted. The temperature sensor is arranged so that the temperature of the optical element of the lens unit 100 or the color separation / synthesis unit 200 can be measured.

  FIG. 2 shows the optical configuration of the projector 500 as viewed from the side. FIG. 2 shows a configuration (side view) when a portion of the projector 500 other than the light source lamp 209, the illumination optical system 201, and the dichroic mirror 204 is viewed from the short side of the liquid crystal panel. The light source lamp 209, the illumination optical system 201, and the dichroic mirror 204 are actually arranged in a horizontal plane perpendicular to the paper surface of FIG.

  FIG. 2 shows a state in which the optical axis 100a of the lens unit 100 is shifted upward with respect to a third polarizing beam splitter 205c described later, that is, an emission optical axis 210 of the color separation / synthesis optical system, that is, the projection light is upward. The shifted state is shown. The projection light can be shifted by shifting the optical axis 100a of the lens unit 100 with respect to the emission optical axis 210 of the color separation / synthesis optical system by the shift unit 300 as described above. When the optical axis 100a of the lens unit 100 is shifted in the depth direction of FIG. 2, the projection light is shifted to the left and right.

  The illumination optical system 201 divides the illumination light from the light source lamp 209 into a plurality of light beams, and then performs a lens element that performs an operation for superimposing on the liquid crystal panel, or the illumination light is polarized light having a predetermined polarization direction. Including a polarization conversion element. The illumination optical system 201 also includes a mirror that bends the optical path.

  Next, the optical action of the illumination optical system 201 will be described. A light beam emitted from the light source lamp 209 in all directions is emitted as substantially parallel light by a parabolic reflector. The parallel light beam enters the IR cut filter, is divided into a plurality of partial light beams by the first lens array, and each partial light beam is collected. Each divided light beam is condensed near the second lens array, and each partial light beam forms a light source image (secondary light source image). The split luminous flux emitted from the second lens array is condensed by the condenser lens and illuminates the reflective liquid crystal panel in a superimposed manner.

  The color separation / combination unit 200 includes a dichroic mirror 204 and first to third polarization beam splitters 205a to 205c. The dichroic mirror 204 transmits blue (B) and red (R) color light, and reflects green (G) color light. Reference numeral 205a denotes a first polarization beam splitter that transmits P-polarized light and reflects S-polarized light, and has a polarization separation surface.

  Reference numerals 206R, 206G, and 206B denote a reflective liquid crystal display element for red, a reflective liquid crystal display element for green, and a reflective liquid crystal display element for blue that reflect incident light and modulate the image, respectively. Each of 206R, 206G, and 206B is attached with a quarter wavelength plate for red, a quarter wavelength plate for green, and a quarter wavelength plate for blue. An exit side polarizing plate G for G that transmits S-polarized light is disposed between 205a and 205c.

  Between the dichroic mirrors 204 and 205b, an incident-side polarizing plate having a polarizing element attached to a transparent substrate and transmitting only the P-polarized light, the polarization direction of the R light is converted by 90 degrees, and the polarization direction of the B light is converted. A color-selective retardation plate that is not used is arranged. 205b is a second polarization beam splitter that transmits P-polarized light and reflects S-polarized light, and has a polarization separation surface.

  Between 205b and 205c, there is an exit side polarization plate for B, and B color light has a characteristic of transmitting only S-polarized light and red color light is transmitted regardless of the polarization direction. The third polarization beam splitter 205c is a prism having characteristics of transmitting dichroic mirrors for B and G color light, and transmitting P-polarized light and reflecting S-polarized light for R color light.

The dichroic mirror 204 and the third polarizing beam splitter 205c constitute a color separation / synthesis unit 200.
Next, the optical action after passing through the illumination optical system will be described. First, the G optical path will be described.

  The G color light transmitted through the dichroic mirror 204 is incident on the first polarization beam splitter 205a, and P-polarized light is transmitted through the polarization separation surface to reach the G reflective liquid crystal display element 206G. In the reflective liquid crystal display element 206G for G, the G light is image-modulated and reflected. The P-polarized component of the image-modulated G reflected light is transmitted again through the polarization separation surface of the first polarization beam splitter 205a, returned to the light source side, and removed from the projection light. On the other hand, the S-polarized component of the image-modulated G reflected light is reflected by the polarization separation surface of the first polarizing beam splitter 205a and is transmitted through the output-side polarizing plate G that transmits S-polarized light. Toward the polarizing beam splitter 205c.

  At this time, in a state where all the polarization components are converted to P-polarized light (a state in which black is displayed), 1/4 provided between the first polarizing beam splitter 205a and the G-use reflective liquid crystal display element 206G. By adjusting the slow axis of the wave plate in a predetermined direction, it is possible to suppress the influence of the disturbance of the polarization state generated in the first polarizing beam splitter 205a and the reflective liquid crystal display element 206G for G. The G color light emitted from the first polarizing beam splitter 205a is transmitted through the output-side polarizing plate, reflected by the third polarizing beam splitter 205c, and reaches the projection lens 100.

  On the other hand, the R and B color lights reflected by the dichroic mirror 204 are incident on the incident side polarizing plate that transmits the P-polarized light. The R and B lights are emitted from the incident-side polarizing plate and then enter the color selective phase difference plate A. The color-selective phase difference plate has a function of rotating only the R color light by 90 degrees in the polarization direction, so that the R color light is converted to S-polarized light and the B color light is converted to P-polarized light to the second polarizing beam splitter 205b. Incident. The R color light incident on the second polarization beam splitter 25b as S-polarized light is reflected by the polarization separation surface of the second polarization beam splitter 205b and reaches the R reflective liquid crystal display element 206R.

  The B color light incident on the second polarization beam splitter 205b as P-polarized light is transmitted through the polarization separation surface of the second polarization beam splitter 205b and reaches the B reflective liquid crystal display element 206B.

  The R color light incident on the R reflective liquid crystal display element 206R is image-modulated and reflected. The S-polarized light component of the R light reflected by the image modulation is reflected again by the polarization separation surface of the second polarization beam splitter 205b, returned to the light source side, and removed from the projection light. On the other hand, the P-polarized component of the image-modulated reflected R light passes through the polarization separation surface of the second polarization beam splitter 205b and travels toward the exit-side polarizing plate as projection light.

  The B color light incident on the B reflective liquid crystal display element 206B is image-modulated and reflected. The P-polarized component of the image-modulated B reflected light is again transmitted through the polarization separation surface of the second polarization beam splitter 206b, returned to the light source side, and removed from the projection light. On the other hand, the S-polarized component of the image-modulated B reflected light is reflected by the polarization separation surface of the second polarizing beam splitter 205b and travels toward the exit-side polarizing plate as projection light.

  At this time, by adjusting the slow axis of the quarter wavelength plate provided between the second polarizing beam splitter 205b and the R and B reflective liquid crystal display elements 206R and 206B, Similarly, the black display of each of R and B can be adjusted.

  Thus, the R and B color lights synthesized into one light flux and emitted from the second polarization beam splitter 205b are P polarization for R color light, S polarization for B color light, and an output side polarization plate, a third polarization beam splitter. Incident at 205c. The R and B projection light passes through the third polarization beam splitter 205 c and is combined with the G color light to reach the projection lens 100. The combined R, G, and B projection light is enlarged and projected onto a projection surface such as a screen by the projection lens 100.

  An image supply device such as a personal computer, a DVD player, or a TV tuner is connected to the liquid crystal driving circuit disposed on the substrate inside the projector 500 via an image input terminal disposed on the outer peripheral surface of the projector 500. The liquid crystal driving circuit drives the reflective liquid crystal display elements 206R, 206G, and 206B based on the image (video) information input from the image supply device, and forms an original image for each color. Thereby, the light incident on each reflective liquid crystal panel is reflected and modulated (image modulation) according to the original image.

  FIG. 3 is an exploded perspective view of the lens unit 100 of the present embodiment. Reference numeral 101 denotes a first lens barrel that holds the first lens group. Reference numeral 102 denotes a second group barrel that holds the second lens group. Reference numeral 103 denotes a third lens barrel that holds the third lens group. Reference numeral 104 denotes a fourth lens barrel that holds the fourth lens group, and reference numeral 105 denotes a fifth lens barrel that holds the fifth lens group. Reference numeral 106 denotes a sixth lens barrel that holds the sixth lens group.

  Reference numeral 107 denotes a fixed cylinder as a lens barrel body. A mount portion (flange portion) 107B that is screwed to the optical box described above is formed at the position of the rear end portion in the optical axis direction of the fixed tube 107 (end portion on the sixth lens barrel side). Reference numeral 108 denotes a cam ring as a first rotating ring which is arranged in a region on the front side (first lens barrel side) of the inner periphery of the fixed cylinder 107 and rotates around the optical axis. Reference numeral 110 denotes a focus ring as a second rotary ring that is arranged in the region on the front side (first lens barrel side) of the outer periphery of the fixed cylinder 107 and rotates around the optical axis. Reference numeral 109 denotes a cam follower attached to the first to fifth lens barrels 101 to 105 with screws.

  The first lens barrel 101 to which the cam follower 109 is attached is fixed to the end portion (first lens barrel side) of the fixed tube 107 via the cam follower 109. The second lens barrel 102 to which the cam follower 109 is attached engages with a cam groove formed in the focus ring 110. The third to fifth lens barrels 103 to 105 to which the cam follower 109 is attached engage with cam grooves formed in the cam ring 108, respectively. A zoom ring 111 has a gear portion and is attached to the first lens barrel side of the cam ring 108.

  Reference numeral 112 denotes a motor unit as an actuator. The motor unit includes a motor body such as a stepping motor, a DC motor, and a vibration motor, a reduction gear box that decelerates and outputs the rotation of the motor body, a pulse plate for expressing the motor drive as a rotation angle, And a substrate holding a photo interrupter for outputting a rotation angle detection result as a pulse signal. The motor unit 112 is a focus drive source and a zoom drive source. Reference numeral 114 denotes a switch for detecting a reference of a focal position when the focus ring 110 rotates around the optical axis.

  A holding member 113 holds the motor 112 and the switch 114. The motor 112 and the switch 114 are fixed to the holding member 113 with screws. The holding member 113 is fixed to the fixed cylinder 107 with screws.

  The second lens barrel 102 is a focus lens. Here, the focus drive mechanism will be described. Cam followers 109 are attached to three locations on the outer periphery of the second lens barrel 102 every 120 ° in the circumferential direction. The cam follower 109 provided in the second lens barrel 102 engages with a rectilinear groove 107A formed in the fixed cylinder 107 so as to extend in the optical axis direction. Further, it engages with a cam groove formed in the focus ring 110.

  Further, the focus ring 110 is rotatable around the optical axis in a state where movement in the optical axis direction is prevented with respect to the fixed cylinder 107 by a bayonet coupling structure or the like. When the motor unit 112 engaged with the focus ring 110 is driven, the focus ring 110 is rotationally driven. When the focus ring 110 rotates, the second lens barrel 102 moves in the optical axis direction due to the engaging action between the cam groove portion and the cam follower 109. Thereby, electric focus drive is performed.

  The sixth lens barrel 106 holds a relay lens as a sixth lens group, and is fixed to the rear end portion of the fixed cylinder 107 with a screw (not shown) from the thrust direction. The second lens barrel 102, the third lens barrel 103, the fourth lens barrel 104, and the fifth lens barrel 105 each hold a variable power lens as the second to fifth lens groups. The second lens barrel 102, the third lens barrel 103, the fourth lens barrel 104, and the fifth lens barrel 105 move in the direction of the optical axis, whereby zooming is performed.

  Here, the zoom drive mechanism will be described. Cam followers 109 are attached to the outer periphery of the second lens barrel 102, the third lens barrel 103, the fourth lens barrel 104, and the fifth lens barrel 105 at three positions every 120 ° in the circumferential direction. The cam followers 109 provided in the lens barrels 102 to 104 engage with a rectilinear groove 107A formed in the fixed cylinder 107 so as to extend in the optical axis direction. Further, it engages with the second, third and fourth cam groove portions 108A, 108B and 108C formed in the cam ring 108.

  A zoom ring 111 is attached to the end of the cam ring 108 (on the first lens barrel side) so as to be rotatable integrally therewith. The cam ring 108 is rotatable around the optical axis in a state where movement in the optical axis direction is prevented with respect to the fixed cylinder 107 by a bayonet coupling structure or the like.

  When the motor unit 112 engaged with the zoom ring 111 is driven, the zoom ring 111 is rotationally driven. When the zoom ring 111 rotates, the cam ring 108 rotates in a fixed position around the optical axis with respect to the fixed cylinder 107 integrally therewith. When the cam ring 108 rotates, the second, third, and fourth lens barrels 102 to 104 move in the optical axis direction by the engaging action of the cam groove portions 108A, 108B, and 108C and the cam follower 109. Thereby, electric zoom drive is performed.

Next, the motor unit 112 will be described with reference to FIG. The motor unit 112
A motor main body 112A, a reduction gear box 112B that decelerates and outputs the rotation of the motor main body, a pulse plate 112C for representing the drive of the motor as a rotation angle, and a photo interrupter for detecting the rotation angle as a pulse signal A holding substrate 112D is included.

  The output gear of the motor main body 112A and the input gear of the reduction gear box 112B are meshed with each other. As a result, the output torque and rotation speed of the motor main body 112A are converted into the intended output torque and rotation speed in the reduction gear box 112B and transmitted to the output gear of the reduction gear box 112B engaged with the focus ring 110 and the zoom ring 111. The Further, a pulse plate 112C having a disc shape and having a notch for each constant phase in the circumferential direction is attached to the output shaft of the motor body 112A. When the motor body 112A is driven, the pulse plate 112C also rotates.

  For this reason, when one arbitrary point of the diameter having the notch of the pulse plate 112C is viewed, the rotation angle of the motor body 112A can be detected without the notch. The reduction gear box 112B is provided with a substrate 112D to which a photo interrupter is attached so that the presence or absence of the notch can be read, and the substrate 112D to which the photo interrupter is attached outputs the presence or absence of the notch as a pulse signal.

  The lens unit 100 of this embodiment detects the relative value of the focal position from the output of the substrate 112D to which the photo interrupter is attached, and moves the focal position until the switch 114 is activated each time the lamp is turned on, thereby setting the reference of the focal position. To detect. The focal position can be detected as a substantially absolute value by combining the focal position reference and the relative value of the focal position. In addition, since the focus position reference is detected each time the lamp is turned on, and the focus position adjustment error such as backlash is reset, the focus position does not go out of depth even if the absolute value of the focus position cannot be detected.

  The volume encoder 115 is engaged with a cam follower 109 held by the fourth group barrel 104, and can detect the absolute position of the fourth group barrel 104 by zooming.

  In FIG. 5, the external view of the shift unit 300 of a present Example is shown. The shift unit 300 is fixed to the liquid crystal projector main body, a fixed plate 370, a first shift plate 371 that shifts up and down (Y direction) with respect to the fixed plate 370, and a left and right direction (X direction). The second shift plate 372 is configured. The first shift plate 371 and the second shift plate 372 are respectively provided with openings 373 and 374 into which the lens unit 100 is inserted, and the lens unit 100 is attached to the second shift plate 372.

  The first shift plate 371 has a vertical hole 376 formed at a position where the first shift plate 371 is inserted into a shaft 375 formed on the fixed plate 370, and the first shift plate 371 extends in the vertical direction with respect to the fixed plate 370. It is held so that it can be shifted. The second shift plate 372 has a left and right elongated hole 378 formed at a position where the second shift plate 372 is inserted into a shaft 377 provided in the first shift plate 71. The second shift plate 372 is formed on the fixed plate 370. On the other hand, it is held so that it can be shifted in the left-right direction.

By configuring the shift unit 300 as described above, the lens unit 100 is held so that it can be shifted on a plane orthogonal to the optical axis 100a of the lens unit.
Next, shift driving of the shift unit 300 of this embodiment will be described.

  A first motor 379 for shifting the first shift plate 371 up and down is attached to the fixed plate 370 by a motor holding plate (not shown). The rotation of the first motor 379 is decelerated to a predetermined rotation speed via the first gear mechanism 380 and transmitted to the first feed screw shaft 381. A thread portion is formed on the first feed screw shaft 381, and a first nut member 382 is screwed into the thread portion. The first nut member 382 is fitted into a first seat 383 provided on the shift plate 371.

  When the first motor 379 is driven, the first feed screw shaft 381 is rotated, and the first nut member 382 is shifted in the vertical direction in contact with the first seat portion 383. Accordingly, the first shift plate 371 is shifted in the same direction as the moving direction of the first nut member 382.

  A second motor 384 for shifting the second shift plate 372 to the left and right is attached to the first shift plate 371 by a motor holding plate (not shown). The rotation of the second motor 384 is reduced to a predetermined number of rotations via the second gear mechanism 385 and transmitted to the second feed screw shaft 386. A thread portion is formed on the second feed screw shaft 386, and a second nut member 387 is screwed into the thread portion. The second nut member 387 is fitted into a second seat 388 provided on the shift plate 372.

  When the second motor 384 is driven, the second feed screw shaft 386 is rotated, and the second nut member 387 is shifted in the left-right direction in contact with the second seat portion 388. Therefore, the second shift plate 372 is shifted in the same direction as the moving direction of the second nut member 387.

  Next, end detection of the shift unit 300 according to the present invention will be described. A first volume encoder 389 is attached to the fixed plate 370 by a first encoder holding plate 390 and detects the absolute position of the first shift plate 371 in the vertical direction. A second volume encoder 391 is attached to the first shift plate 371 by a second encoder holding plate 392, and detects the absolute position of the second shift plate 372 in the left-right direction.

  FIG. 6 is a block diagram of focal position correction according to the present embodiment, and FIG. 7 shows an algorithm for focal position correction according to the present embodiment. The focus position correction amount is determined from the temperature from the temperature sensor, the focus position from the substrate 112D to which the photo interrupter is attached and the switch 114, the zoom position from the volume encoder 115, and the shift position from the volume encoder 389 and the volume encoder 391. The focal position correction amount is selected from a measured value of the focal position movement amount or a table obtained from a simulation, or a value obtained from a function using a measured value of each sensor as a parameter.

  The focal position correction amount is set as a target focal position, and the target focal position is converted into the number of pulses. Further, the number of pulses is converted into a current application time. At this time, a coefficient at the time of conversion is determined using the output of the temperature sensor, and the number of pulses is converted into a current application time using this coefficient. This is because the focus operating torque changes due to a temperature change, and the amount of rotation of the motor unit 112 changes depending on the temperature even when a current of a certain time is applied to the motor unit 112. As the coefficient, a measured value of a motor unit rotation amount at a temperature change or a value obtained from a simulation is used. Next, by applying a current to the converted time motor unit 112, the second lens barrel 102, which is a focus lens, moves to the target focal position via the focus ring 110.

  Further, by detecting the rotation amount of the motor unit 112 by the substrate 112D to which the photo interrupter is attached, an error from the target value can be fed back and corrected. With this configuration, the second lens barrel 102, which is a focus lens, can be reliably moved to the target focal position. The curvature of field is continuously generated by the temperature rise of the optical element and the optical element holding member of the lens unit 100 after the projector 500 is turned on. For this reason, the focal position correction is performed continuously over time or intermittently with an interval shorter than the time from the depth to the defocus.

  With the above configuration and algorithm, it is possible to provide a projector that always provides a good image even when the optical element of the lens unit and the optical element holding member change in curvature of field due to a temperature rise and when the projected image moves due to the shift mechanism. It becomes like.

  As mentioned above, although the preferable Example of this invention was described, this invention is not limited to the said Example, A various deformation | transformation is possible within the range as described in a claim. For example, in the above embodiment, a reflective liquid crystal panel or a transmissive liquid crystal panel is used as the light modulation element, but a digital micromirror device (DMD) may be used instead. Further, a volume encoder may be used for measuring the driving time for focusing, and a pulse plate and a photo interrupter may be used for measuring the driving time for zooming and shifting.

100 Projection lenses 101 to 106 First to sixth lens barrel 107 Fixed barrel 107A Lens barrel guide groove 108 Cam ring 108A, 108B, 108C Cam groove 109 1, 2, 3, 4, 5 group cam follower 110 Focus ring 111 Zoom ring 112 Motor 113 Motor holding member 114 Switch 115 Volume encoder 200 Color separation / combination unit 201 Illumination optical system 204 Dichroic mirrors 205a, 205b, 205c Polarization beam splitters 206R, 206G, 206B Reflective display element 207 Image detection means 208 Holding member 209 Light source lamp 210 Emission optical axis 300 of color separation / synthesis optical system Shift unit 370 Fixed plate 371 First shift plate 372 Second shift plate 373, 374 Opening 375, 377 Shaft 376, 378 Long hole 379 First Motor 380 First gear mechanism 381 First feed screw shaft 382 First nut member 383 First seat portion 384 Second motor 385 Second gear mechanism 386 Second feed screw shaft 387 Second nut member 388 Second seat portion 389 First volume encoder 390 First volume encoder holding sheet metal 391 Second volume linear encoder 392 First volume encoder holding sheet metal 393T, 393B, 393R, 393L Rubber members 394T, 394B, 394R, 394L abutment section 500 projector

Claims (5)

A color separation / synthesis unit using a liquid crystal panel and two or more prisms;
A lens unit that performs focusing by moving at least one optical element;
Temperature measuring means for measuring the temperature of at least one of the color separation / synthesis unit and the lens unit;
A shift unit that shifts the projected image by moving the lens unit on a plane perpendicular to the optical axis of the lens unit;
Shift position detecting means for detecting the shift position of the shift unit;
In a projection image display device that projects an image on a screen,
A projection type image display apparatus, wherein a focal position correction amount is determined from information of the temperature detection means and the shift position detection means. The projection type image display apparatus according to claim 1 comprises:
Zoom position detecting means for detecting the zoom position of the lens unit;
A projection type image display apparatus, wherein a focal position correction amount is determined from information of the zoom position detecting means. The projection type image display device according to claim 1 or 2,
A focus position detecting means for detecting a focus position of the lens unit;
A projection type image display apparatus, wherein a focus position correction amount is determined from information of the focus position detecting means. The projection type image display apparatus according to claim 1 is a projector that changes light from a light source into an image by a modulation element, and magnifies and projects the image by a lens unit. The projection type image display device according to any one of claims 1 to 4,
A projection-type image display device characterized by electric focus, electric zoom, and electric shift.