JP4774224B2 - Projection device - Google Patents

Description

  The present invention relates to a projection apparatus, and more particularly to a projection apparatus that includes a projection lens that enlarges and projects an image displayed on a display element such as a liquid crystal display element on a screen and a lens barrel that holds the projection lens. It is.

  The projector includes a projection device and an image light generation unit. The image light generator generates image light by receiving and optically modulating the illumination light in which the energy distribution of the illumination light emitted from the light source is made uniform by a light guide means such as a rod integrator. The projection device projects the image light generated by the image light generation unit on the screen. The lens barrel incorporates a focus adjustment mechanism that adjusts the focus of the projection lens to a predetermined finite distance. This focus adjustment is performed at a factory that manufactures the projection apparatus.

  There are two types of image light generation units, a transmission type and a reflection type, depending on the difference in the light modulation method. In the case of the transmissive type, a transmissive liquid crystal panel is used, and light is modulated by driving each liquid crystal cell of the liquid crystal element according to a video signal.

  A reflective display panel is used as the reflective image light generator. The reflective display panel includes a digital micromirror device (DMD), a liquid crystal on silicon (LCOS) element, and the like. DMD has a large number of variable light reflection angle variable mirror elements in a matrix shape that can be varied between an on position where reflected illumination light is reflected toward the projection lens and an off position where the illumination light is reflected toward the direction away from the projection lens. It is an arrangement. When the pixel is displayed brightly, the mirror element is moved to the on position, and when the pixel is darkly displayed, the mirror element is moved to the off position. By controlling the reflection direction of the illumination light in this way, light modulation according to the video signal is performed.

  Generally, the projector is placed on a table or the like below the screen so as to project toward the upper screen. For this reason, the projection lens is attached at an angle so that the optical axis is inclined upward with respect to the horizontal. However, in this case, since the image display surface and the image projection surface are not parallel, there is a problem that the image is distorted into a trapezoid. Therefore, a launch projection type projector is known (Patent Document 1). This type of projector forms an image so that the center of the image projection surface is higher than the optical axis of the projection lens by shifting the optical axis of the projection lens upward from the center of the image display surface. In the projection lens used in this type, the projected light beam passes through a position shifted from the center of the optical axis.

In recent years, with the progress of higher definition of projected images, the demand for downsizing and cost reduction of the whole projection apparatus has increased, and a projection lens having a small size, low cost and high performance is desired. Thus, a projection lens using a plastic lens is known (Patent Document 2).
Japanese Patent Laid-Open No. 11-327047 JP 2001-42211 A

  When adjusting the focus of the projection apparatus, it is common to change the distance (interval) between the lens group for adjusting the focus and the other lens group. In this modified structure, a holding frame that holds the lens group and a fixed cylinder that supports the lens group are coupled by a helicoid (screw groove), and the holding frame is rotated with respect to the fixed cylinder that holds the remaining lens group. In general, the lens group moves in the optical axis direction together with the holding frame with respect to the fixed cylinder. In this way, the lens group is rotated to move in the optical axis direction for focus adjustment, and after the adjustment, the holding frame is screwed to the fixed cylinder to prevent rotation.

  The plastic lens can achieve low cost of the projection device only when stable mass production can be performed by mold molding using the injection device. However, in recent years, in order to improve optical performance, it has become complicated with a high degree of freedom, such as a rotationally symmetric aspherical lens and a rotationally asymmetric aspherical lens with respect to the optical axis. For this reason, in the conventional injection molding method, pressure distribution is generated in the mold due to, for example, non-uniform cooling, deterioration of both shape accuracy and internal distortion, and jetting due to the gate, flow mark phenomenon, etc. It happens. In response to this situation, an injection molding method that can ensure stability has been developed, but even in the case of acceptable molded products, the shape collapses locally, for example, around the gate due to differences in molds or differences in the molding environment. It has been found that when the projected portion is generated and the projected light beam enters the local area, the performance of the projected image may be deteriorated.

  Also, if such a plastic lens is incorporated in a lens group that moves during focus adjustment, the lens group moves in the optical axis direction while rotating, and the focus adjustment is performed. What happens. This is because the focus position of the lens group differs somewhat depending on the projector, and thus the rotation position of the lens group, that is, the local position differs. Therefore, in one projection lens, the projection light flux does not pass through the local area, so that the image performance is satisfied. On the other hand, in the other projection lens, the projection light flux passes through the local area and the performance is not satisfied. Lens groups used in projectors that do not satisfy the performance are counted as defective, and therefore, it was considered in the factory that the quality of the molded product was poor or poor.

  The projection lens is commonly used for projectors having different screen sizes (screen aspect ratios). In this case, even if the projector with the previous screen size satisfies the performance of the projected image, the projector with a different screen size may cause the projection light beam to pass through the local area and deteriorate the performance. If the performance of the projection lens is checked in all of the screen sizes in the manufacturing process, it is very time consuming and increases the cost. Furthermore, considering that it is commonly used for launch projection type projectors, in this type, the projected light flux is deviated from the center of the optical axis, that is, the optical axis of the optical surface and the periphery radially away from the optical axis. This causes a further problem with the front lens focus adjustment type projection lens.

  The present invention is for solving the above-mentioned problems, and is used in any type of projector such as a projector whose focus position varies, a projector whose screen size is different, or a projector whose light flux passes through a range deviated from the center of the optical axis. Another object of the present invention is to provide a projection device devised so that focus adjustment can be performed by moving a plastic lens so that a projection light beam does not pass through a local portion of the optical surface of the plastic lens caused by mold molding. .

In order to solve the above problems, the present invention provides an image synthesized through the color synthesizing means image information of a plurality of color light based on the plurality of display elements, in the projection device for enlarging and projecting on a screen through a projection lens, one A plastic lens having projections formed by injection molding on a part of the outer periphery is used for some or all of the lenses, and the focus of the projection lens is changed by moving in the optical axis direction, and the optical surface of the plastic lens is A focusing lens group through which a projected light beam passes only in a specific area, and the lens group in a fixed posture where the projection is located either above or below the specific area when viewed from the screen. a holding frame that holds a lens barrel body that holds some or all of the lens units other than the lens group of the projection lens, when focus adjustment A rectilinear moving mechanism that has a rotating body that rotates relative to the lens barrel body, and that moves the holding frame linearly in the optical axis direction relative to the lens barrel body in conjunction with the rotation of the rotating body; It is provided with.

  At the time of focus adjustment, the rotating body is rotated. This rotation may be manual or automatic. In the case of the automatic type, a distance measuring mechanism is provided, a motor is driven based on the result of distance measurement by the distance measuring mechanism, and the driving of the motor is input to the rotating cylinder. In the case of manual type, the rotating body is a focus ring. A rectilinear support mechanism for supporting the holding frame together with the focus ring so as to be movable in a straight line with respect to the barrel main body in an optical axis direction; A helicoid mechanism that moves in the optical axis direction with respect to the cylinder body.

  The lens group that moves in the optical axis direction during focus adjustment may be one or more lens groups of a plurality of lens groups that constitute the projection lens. As the linear support mechanism, for example, it is preferable that the linear advance key is formed by engaging a linear key formed on a convex line parallel to the optical axis and a linear groove formed on the concave line.

  As described above, in the projection apparatus of the present invention, the lens group that moves in the optical axis direction during focus adjustment is moved straight without rotating. By integrating the lens group into the holding frame at a fixed rotational position where the projected light beam is transmitted, only a specific area can be used for any type of projector, such as projectors with different focus positions or projectors with different screen sizes. Thus, the projected light flux can be transmitted, so that the deterioration of the performance of the projected image can be surely prevented.

  The projector 10 includes a projection device 11 and an image light generation unit 12. The projection device 11 includes a projection lens 13 composed of a plurality of lens groups. The projection lens 13 is of the front lens focus adjustment type, and at the time of focus adjustment, the front lens group (focus lens group) 15 closest to the screen 14 of the projection lens 13 is moved in the direction of the optical axis 16. . In FIG. 1, the lens barrel 17 that holds the projection lens 13 is simply illustrated in order to prevent complication of the drawing.

  As shown in FIGS. 2 and 3, the lens barrel 17 includes a front holding frame 20, a focus ring 21, and a lens barrel body 22. The front lens group 15 is held by the front holding frame 20. The remaining lens group is held by the barrel main body 22. The outer periphery of the front holding frame 20 has a back surface 20b that is recessed by one step with respect to the front (screen side) surface 20a along the direction of the optical axis 16, a male helicoid 23 on the front surface, and a back surface 20b that is recessed by one step. Are formed with a plurality of rectilinear keys 24 projecting at equally divided positions in the circumferential direction.

  Each of the rectilinear keys 24 is formed to extend in parallel to the optical axis 16, and engages with a plurality of rectilinear grooves 25 provided in the same number as the rectilinear keys 24 on the front inner periphery of the barrel main body 22. Thereby, the lens barrel main body 22 supports the front holding frame 20 so as to be linearly movable in the direction of the optical axis 16. These rectilinear keys 24 and rectilinear grooves 25 constitute the rectilinear support mechanism of the present invention.

  The focus ring 21 is disposed so as to cover the front holding frame 20 and the front end of the barrel main body 22. A female helicoid 26 that engages with the male helicoid 23 is formed on the inner surface of the focus ring 21. In addition, a long hole 27 is opened in the focus ring 21 along a partial range in the circumferential direction. The head of a screw pin 28 attached to the outer periphery of the front end of the barrel main body 22 is engaged with the long hole 27. As a result, the focus ring 21 rotates within the length of the long hole 27 in the circumferential direction, that is, within a certain angle in a state where movement in the direction of the optical axis 16 is stopped with respect to the barrel main body 22. When the focus ring 21 rotates, the front holding frame 20 moves straight in the direction of the optical axis 16 according to the lead of the male / female helicoids 23 and 26 in a state where the front holding frame 20 is stopped by the lens barrel body 22. Thereby, the focus adjustment of the projection lens 13 can be performed. The male / female helicoids 23 and 26 constitute the helicoid mechanism of the present invention.

  As shown in FIG. 4, a plastic lens is used for some lenses 30 of the front lens group 15 held by the front holding frame 20. In order to improve the optical performance, the lens 30 is an aspherical lens whose optical surface shape (cross-sectional shape) is rotationally symmetric about the optical axis 16, and is made by injection molding.

  The lens 30 has a flange 31 and an optical surface 32. As shown in detail in FIG. 5, the collar portion 31 is an outer peripheral portion that is held by the front holding frame 20, and is a surface that does not converge or diverge the projected light beam. The optical surface 32 is an inner range excluding the collar portion 31 and is a surface that converges or diverges the projected light beam.

  The lens 30 is formed with a cutout portion 33 in which a part of the outer periphery of the collar portion 31 is cut out on a straight line in order to reduce the cost without processing after the gate. The notch 33 has a protrusion 34 after the gate generated by injection molding. Since the protrusion 34 has a cut-out position of the cut-out portion 33 so as to have a height that does not contact the inner periphery of the front holding frame 20, a jammer is secured when the lens 30 is fixed to the front holding frame 20. Never become.

  By the way, in the lens 30, the local 35 of the optical surface 32 in the vicinity of the protrusion 34 is in a range in which performance is easily deteriorated when an image is projected. This is because, in the local 35, a weld mark caused by a sudden change in the cross-sectional area of the molded product, a wrinkle generated by the resin being cooled before the holding pressure is applied, and the pattern at the time of freezing being frozen. This is because defects such as warpage and deformation caused by the anisotropy of the shrinkage rate are likely to occur near the gate.

  Therefore, when the lens 30 is incorporated into the front holding frame 20, the projection 34 is incorporated in a certain posture, for example, located below as viewed from the screen 14. This fixed posture allows the projected light flux to pass through only the specific area 36 excluding the local area 35, even if the focus position varies, or even if it is commonly used for projectors with different image screen sizes or launch projection type projectors. The posture, that is, an absolute posture with respect to the projection device 11 is obtained. This specific area is a part of or all of the specific area that is used for projectors with different focus positions, projectors with different image screen sizes, or launch projection type projectors. This is a common range.

  Before making the projection device 11, the front lens group 15 is incorporated in the front holding frame 20 in advance. At this time, the molded lens 30 is assembled in a fixed posture. The front holding frame 20 incorporating the front lens group 15 is carried to the projection device manufacturing process. In the projection device manufacturing process, a lens group other than the front lens group 15 is incorporated in the lens barrel body 22 in advance. Thereafter, the front holding frame 20 is assembled from the front side of the lens barrel main body 22 in such a posture that the straight advance key 24 engages with the straight advance groove 25.

  At this time, the lens 30 of the front lens group 15 is incorporated so as to maintain the fixed posture with respect to the barrel main body 22. This is because when the lens 30 is assembled in the front holding frame 20, the lens 30 is incorporated in the front holding frame 20 in which the direction of the rectilinear key 24 is aligned so as to be in a constant posture with respect to the lens barrel body 22. Therefore, by engaging the rectilinear key 24 with the rectilinear groove 25 in that direction, the lens 30 is uniquely positioned in the projection device 11 as well.

  Thereafter, the male and female helicoids 23 and 26 are joined by inserting the focus ring 21 while rotating it from the front side of the front holding frame 20. With this rotation, the focus ring 21 is retracted with respect to the front holding frame 20. This retraction is performed until the screw hole from the long hole 27 toward the lens barrel body 22 is exposed. Finally, the projection pin 11 is completed by fixing the screw pin 28 to the screw hole 40 through the long hole 27.

  The completed projection device 11 is conveyed to the focus adjustment process. In the focus adjustment step, an image prepared in advance for examining the resolution is projected onto a screen 14 arranged at a predetermined finite distance, and the focus ring 21 is rotated in one direction or the other direction while viewing the image so that the image is displayed. Find the best focus position. When the focus adjustment position of the focus ring 21 is determined, the focus ring 21 is fixed to the barrel main body 22 by fixing means (not shown). The projection device 11 for which the focus adjustment has been completed is incorporated in the projector 10. In the projection device 11, since the lens 30 that is a plastic lens is incorporated in a fixed posture with respect to the barrel main body 22, the projection light beam passes only through the specific region 36 except the local 35. For this reason, the performance of the image to project does not deteriorate.

  In addition, the local 35 arises in the substantially the same position in a molded article lens by using the same injection device and metal mold | die. In the above embodiment, the position is limited to the position in the vicinity of the gate, that is, the range in which the failure phenomenon due to the gate occurs. However, the present invention is not limited to this range, and the failure phenomenon due to mold molding is not limited to this range. It is good also considering the range which is easy to generate | occur | produce as a local. What is necessary is just to fix this lens to a holding frame by making this local 35 into a fixed attitude | position (direction). Further, in the above-described embodiment, the posture in which the lens is incorporated is unified to the posture in which the local 35 is directed downward. However, the present invention is not limited to this, and the projection light flux is not limited to this even when used for a plurality of types of projectors. Any position in the rotational direction may be used as long as it does not pass through.

  In the above embodiment, the rectilinear key 24 and the rectilinear groove 25 are arranged at equally spaced positions in the circumferential direction, that is, at the same interval positions in the circumferential direction. For this reason, when assembling the front holding frame 20 into the barrel main body 22, it is necessary to carefully incorporate the rotational position of the front holding frame 20 so that the lens 30 is in a rotational position where the lens 30 is in a fixed posture. This is because there are a plurality of engagement positions between the rectilinear key 24 and the rectilinear groove 25. Therefore, it is preferable to provide the straight key 24 and the straight groove 25 at positions having different intervals in the circumferential direction. If it carries out like this, since the rectilinear key 24 and the rectilinear groove | channel 25 will engage only in the position of the circumferential direction, an assembly becomes easy. Conversely, the straight movement key 24 may be provided in the lens barrel body 22, and the straight movement groove 25 may be provided in the front holding frame 20. Further, the cross-sectional shape of the straight advance key 24 and the straight advance groove 25 may be any shape as long as it is a known shape.

  In the above embodiment, the front lens group 15 that moves during focus adjustment is configured by two lenses, but may be configured by one lens or three or more lenses. When a plurality of lenses are used, as described in the above embodiment, a plastic lens may be used for at least one lens 30, or all the lenses may be plastic lenses. When a plurality of plastic lenses are used, they may be incorporated into the front holding frame 20 so that all of the local areas 35 excluding the specific area when viewed from the screen 14 are in a fixed orientation when incorporated into the barrel main body 22.

  Moreover, in the said embodiment, although it is set as the front lens focus adjustment type projection apparatus 11, the lens group moved at the time of focus adjustment is not restricted to a front lens, It is good also as lens groups other than a front lens. Furthermore, although one lens group is moved during the focus adjustment, the present invention is not limited to this, and the present invention can be applied to a projection apparatus configured to move a plurality of lens groups simultaneously.

  Further, in the above embodiment, the lens 30 that is a plastic lens is an aspherical lens that is rotationally symmetric with respect to the optical axis 16, but a rotationally symmetric spherical lens may also be used, and the lens 30 moves straight forward during focus adjustment. Therefore, a rotationally asymmetric spherical lens or a rotationally asymmetric aspheric lens can also be used.

  In the above embodiment, the male / female helicoids 23 and 26 having a trapezoidal cross section are used, but instead of these, a male / female screw having a V-shaped cross section may be used. If the screw type is used, the backlash is less than that of the helicoid, and the space can be saved. Furthermore, since the lead angle with respect to the rotation amount can be increased, the movement amount of the front holding frame 20 can be increased with a small amount of rotation.

Further, the projection device of the present invention can also be employed in a rear projector. The rear projector includes a rear screen incorporated in a housing, a projector unit that generates image light from a white light source, and a rear mirror that reflects image light emitted from the projector unit toward the screen. Enlarge the image. In the projector unit,
A projection lens is incorporated. Some rear projectors are designed to be thinned by bending the projection lens into a substantially V shape to suppress an increase in dimension in the thickness direction due to the length of the projection lens. This type of projection lens includes a bending optical system such as two plane mirrors and a prism, for example, between a front optical system and a rear optical system that are separated in the front and rear in the optical axis direction. The bending optical system bends the optical axes of each other so that the front optical system faces upward with respect to the rear optical system, for example. For this reason, the bending optical system has two reflecting surfaces inclined so that their normal lines do not belong to the same plane, and the optical path of the projection light is bent by these reflecting surfaces. By configuring a part or all of the front optical system of such a projection apparatus as a lens group that moves in the optical axis direction during focus adjustment, the operation during focus adjustment can be easily performed.

It is explanatory drawing which shows the outline of the projector using this invention. It is sectional drawing which shows the positional relationship with a front holding frame, a focus ring, and a lens-barrel main body. It is a disassembled perspective view which shows a front holding frame, a focus ring, and a part of front end of a lens-barrel main body. It is sectional drawing which shows the front holding frame holding a front lens group. It is a longitudinal cross-sectional view which shows the front holding frame demonstrated in FIG. 4, and is seen from the screen side.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 Projection apparatus 13 Projection lens 15 Front lens group 20 Front holding frame 21 Focus ring 22 Body of lens barrel 23 Male helicoid 24 Straight key 25 Straight groove 26 Female helicoid 27 Long hole 28 Screw pin

Claims (2)

In a projection apparatus that enlarges and projects an image obtained by synthesizing image information of a plurality of color lights based on a plurality of display elements through a color synthesis unit on a screen through a projection lens ,
For some or all of the lenses, a plastic lens having a protrusion formed by injection molding on a part of the outer periphery is used, and the focus of the projection lens is changed by moving in the optical axis direction, and the optical surface of the plastic lens A focusing lens group through which the projected luminous flux passes only in a specific region of
A holding frame that holds the lens group in a fixed posture in which the protrusion is located either above or below the specific region when viewed from the screen ;
A lens barrel body that holds a part or all of the lens group other than the lens group of the projection lens, and
A rectilinear movement that has a rotating body that rotates relative to the lens barrel body during focus adjustment, and that moves the holding frame linearly in the optical axis direction relative to the lens barrel body in conjunction with the rotation of the rotating body. And a mechanism.   The rotating body is a focus ring that rotates at a fixed angle with respect to the barrel main body at the time of focus adjustment, and the rectilinear movement mechanism moves the holding frame straight in the optical axis direction with respect to the barrel main body. And a linear support mechanism that supports the movable body and a helicoid mechanism that moves the holding frame in the optical axis direction relative to the lens barrel body in conjunction with rotation of the focus ring. The projection device according to claim 1.

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