Liquid Crystal Projector

The present invention relates to front-type and rear-type liquid crystal projectors using a liquid crystal panel, particularly to a control mechanism of the liquid crystal panel.

As a conventional liquid crystal panel setting structure, a structure in which a liquid crystal panel is directly secured to a photosynthetic prism is disclosed in the official gazettes of Japanese Patent Application Laid-Open No. 4-10128 and Japanese Patent Application No. 4-270557. In these official gazettes, it is particularly shown that an imaging optical system is decreased in size, weight, and number of parts and the cost is decreased due to reduction of assembling and controlling operations by omitting a mechanism for performing picture-element alignment control (hereafter referred to as alignment control) between a plurality of liquid crystal panels (also known as light bulbs) for modulating the light separated into red, green, and blue and arrangement control (hereafter focus control) of each liquid crystal layer surface serving as an object within the allowable focal depth of a projection lens.

In the case of the structure disclosed in these official gazettes, however, because a liquid crystal panel is firmly secured to a photosynthetic prism, it is very troublesome to remove the liquid crystal panel if repair or reproduction is necessary. Repair of a product is not frequently required after the product is shipped from a factory to a market. In a factory before shipping a product, however, repair and reproduction are frequently required due to the following causes.

(1) Replacement of a defective product with a non-defective product because a pattern is disconnected due to chipping, a circuit device is broken down due to static electricity incoming from an electrode terminal, or contamination is caused by hand oil or adhesive.

(2) Replacement of a defective product with a non-defective product when a claim suddenly occurs because each manufacturing process is not stabilized in the beginning of mass production of a liquid crystal panel.

Moreover, decreasing the alignment control accuracy to 1/2 picture elements or less between picture elements is indispensable to reduce the unclearness of a screen and prevent color drift. When considering the magnification chromatic aberration of a projection lens and the accuracy deviation of the synthetic surface of a photosynthetic prism, it is necessary to keep the control accuracy within several microns. Moreover, though the focus control accuracy depends on a set value of the allowable scattering circle of a projected image and a set F value, the allowable focal depth comes to approx. 100 .mu.m and thus, control is necessary in this range. Therefore, an exclusive expensive regulator capable of adjusting six axial directions is necessary. Furthermore, because it is impossible to set the expensive regulator to every foothold for performing after-sale services, a product must be repaired or reproduced by returning it to a limited foothold or a manufacturing factory. Therefore, the following problems are pointed out.

(1) After-sale service is interrupted or a user must pay much money when replacing a defective imaging optical-system unit with a new one.

(2) Also when performing repair or reproduction in a manufacturing factory, the serviceability ratio in mass production is lowered and resultingly, the cost is increased.

Moreover, a liquid crystal panel and a photosynthetic prism are expensive parts. Therefore, when three high-precision liquid crystal panels for red, blue, and green capable of corresponding to the 640.times.480 dot arrangement are used, it is very wasteful to do away with them as defective products because they account for 20 to 40% of the part cost and the cost increases.

It is an object of the present invention to provide a liquid crystal projector simplifying the structure, using less number of parts, and decreasing the man-hour for assembling and controlling operations.

It is another object of the present invention to provide a liquid crystal projector making it possible to easily replace a manufactured liquid crystal panel.

It is still another object of the present invention to provide a liquid crystal projector making it possible to obtain a high quality image by simplifying the assembling and controlling operations.

It is still another object of the present invention to provide a compact and lightweight liquid crystal projector by realizing a small optical system.

The liquid crystal projector according to one mode of the present invention comprises three liquid crystal panels for modulating the first color light, second color light, and third color light respectively, photosynthetic, i.e. light synthetic means in which four rectangular prisms are arranged so that the top side of each right angle fits and contacts each other and two types of selected wavelength surfaces having a different wavelength selectiveness are formed to be cruciform on the contact surface in each prism to synthesize the color lights modulated by the liquid crystal panels, a projection lens for projecting the light synthesized by the photosynthetic means, a setting member located between a pair of opposite sides of liquid crystal panels in a direction in common to the liquid crystal panels and a pair of sides of the incident surface of the photosynthetic means corresponding to a pair of opposite sides of a liquid crystal panel to set the liquid crystal panels to the photosynthetic means, and a wedge-type spacer member for adjusting the position of a liquid crystal panel in its planar direction and the direction perpendicular to the planar direction. Moreover, the liquid crystal panels are secured to the photosynthetic means through the setting member and the spacer member.

In the case of the liquid crystal projector according to another mode of the present invention, a liquid crystal panel, setting member, spacer member, and photosynthetic means are fixed each other by an adhesive in the above liquid crystal projector.

In the case of the liquid crystal projector according to still another mode of the present invention, a setting member and a spacer member comprise a member capable of transmitting light in the above liquid crystal projector.

In the case of the liquid crystal projector according to still another mode of the present invention, a spacer member is arranged between a setting member and photosynthetic means or between the setting member and a liquid crystal panel in the above liquid crystal projector.

In the case of the liquid crystal projector according to still another mode of the present invention, a pair of setting members is arranged at the facing side of a liquid crystal panel along its vertical direction and a pair of setting members form a channel for vertically passing a cooling air together with a liquid crystal panel and photosynthetic means in the above liquid crystal projector.

In the case of the liquid crystal projector according to still another mode of the present invention, a liquid crystal panel is stored in and secured to a conductive shield case in the above liquid crystal projector.

In the case of the liquid crystal projector according to still another mode of the present invention, an adhesive is softened when heated in the above liquid crystal projector. Therefore, when repair or reproduction is necessary, a setting member can be removed by heating a bonded portion.

The liquid crystal projector according to still another mode of the present invention comprises three liquid crystal panels for modulating the first color light, second color light, and third color light respectively, photosynthetic means in which four rectangular prisms are arranged so that the top side of each right angle fits and contacts each other and two types of selected wavelength surfaces having a different wavelength selectiveness are formed to be cruciform on the contact surface in each prism to synthesize the color lights modulated by the liquid crystal panels, a projection lens for projecting the light synthesized by the photosynthetic means, a wedge-type spacer member for adjusting the position of the liquid crystal panels in their planar direction and the direction perpendicular to the planar direction, and a protrusion which is formed on a pair of opposite sides of an incident surface in a direction in common to the incident surfaces, and engaged with the spacer member. Moreover, the liquid crystal panels are secured to the photosynthetic means through the spacer member and the protrusion.

The liquid crystal projector according to still another mode of the present invention comprises at least one liquid crystal panel arranged on an object position of an imaging optical system provided with a projection lens and photosynthetic means, a holding member to which the liquid crystal panel is secured, a frame located between the holding member and the photosynthetic means, and a wedge-type spacer member located between the frame and the photosynthetic means to adjust the position of the liquid crystal panel in its planar direction and the direction perpendicular to the planar direction. Moreover, the holding member is provided with a body at whose central portion a window is opened and in which a liquid crystal panel is arranged so as to cover the window, and an elastic member engaging with the frame to temporarily secure the body to the frame. Furthermore, the liquid crystal panel is secured to the photosynthetic means through the holding member, the frame and the spacer member.

In the case of the liquid crystal projector according to still another mode of the present invention, the outer periphery of a liquid crystal panel is fixed by means of point bonding at least several points by an adhesive with a relatively high securing force when the liquid crystal panel is secured to a holding member and the remaining portion is fixed by an elastic adhesive in the above liquid crystal projector.

In the case of the liquid crystal projector according to still another mode of the present invention, a position adjusting member for adjusting the position of a holding member is arranged on a frame in the above liquid crystal projector.

In the case of the liquid crystal projector according to still another mode of the present invention, a joint is provided between the body of a holding member and an elastic member, the joint and a frame are fixed by a screw, and a hole to be fitted to a positioning dowel on the frame is formed on the holding member in the above liquid crystal projector.

The liquid crystal projector according to still another mode of the present invention comprises at least one liquid crystal panel arranged at the object position of an imaging optical system provided with a projection lens and photosynthetic means, a support frame arranged so as to face the incident surface of the photosynthetic means and supporting the margin of the liquid crystal panel, and a wedge-type spacer member located between the support frame and the liquid crystal panel to adjust the liquid crystal panel in its planar direction and the direction perpendicular to the planar direction. Moreover, the liquid crystal panel is secured to the support frame through the spacer member.

In the case of the liquid crystal projector according to still another mode of the present invention, a projection lens is secured to a support frame in the above liquid crystal projector.

In the case of the liquid crystal projector according to still another mode of the present invention, a support frame also serves as the frame of an optical system including a light separating system and moreover, photosynthetic means comprises a dichroic mirror in the above liquid crystal projector.

The liquid crystal projector according to still another mode of the present invention comprises at least one liquid crystal panel arranged at the object position of an imaging optical system provided with a projection lens and photosynthetic means, a support frame arranged so as to face the incident surface of the photosynthetic means and having a plurality of protrusions, and a holding member to which the liquid crystal panel is secured, which has an opening to be engaged with the protrusion, and in which the opening and the protrusion of the support frame are bonded and fixed. The liquid crystal panel is secured to the support frame through the holding member.

The liquid crystal projector according to still another mode of the present invention comprises three liquid crystal panels for modulating the first color light, second color light, and third color light respectively, photosynthetic means in which four rectangular prisms are arranged so that the top side of each right angle fits and contacts each other and two types of selected wavelength surfaces having a different wavelength selectiveness are formed to be cruciform on the contact surface in each prism to synthesize the color lights modulated by the liquid crystal panels, an outgoing-side polarization plate attached to the incident surface of the photosynthetic means, and a wedge-type spacer member located between the facing side of the liquid crystal panel and the position of the outgoing polarization plate corresponding to the facing side to adjust the position of the liquid crystal panel in its planar direction and the direction perpendicular to the planar direction. The liquid crystal panel is secured to the photosynthetic means through the spacer member and the outgoing-side polarization plate.

The liquid crystal projector according to still another mode of the present invention comprises at least one liquid crystal panel arranged at the object position of an imaging optical system, an outgoing-side polarization plate attached to the surface of the liquid crystal panel at the photosynthetic means side, and a wedge-type spacer member located between the outgoing-side polarization plate and the liquid crystal panel to adjust the position of the liquid crystal panel in its planar direction and the direction perpendicular to the planar direction. Moreover, a protrusion having a slope is formed on the outgoing-side polarization plate, the slope of the protrusion are engaged with the spacer to bond and fix them, and the liquid crystal panel is secured to the photosynthetic means through the spacer member and the outgoing-side polarization plate.

The liquid crystal projector according to still another mode of the present invention comprises at least one liquid crystal panel arranged at the object position of an imaging optical system provided with a projection lens and photosynthetic means, an outgoing-side polarization plate attached to the surface of the photosynthetic means side of the liquid crystal panel, a transparent sheet attached to the incident surface of the photosynthetic means, a wedge-type spacer member located between the outgoing-side polarization plate and the transparent sheet to adjust the position of the liquid crystal panel in its planar direction and the direction perpendicular to the planar direction. Moreover, the liquid crystal panel is secured to the photosynthetic means through the outgoing-side polarization plate, spacer member, and transparent sheet.

The liquid crystal projector according to still another mode of the present invention forms a protrusion having a slope on a transparent sheet and engages the slope of the protrusion with a spacer and bond and fix them in the above liquid crystal projector.

Because the present invention is constituted as described above, it has the following advantages.

(1) Because a mechanism for alignment control and focus control is omitted, an optical system is decreased in size and weight by the values equivalent to the size and weight of the mechanism and thus, a compact liquid crystal projector is realized. In the case of downsizing a liquid crystal panel by using a polysilicon TFT, to downsize the optical system with the panel, the above control mechanism mainly prevents an optical system from being downsized. According to the present invention, however, it is possible to omit the control mechanism and therefore, downsize the apparatus.

(2) Moreover, it is possible to increase a cooling-air channel space by using the space of the omitted control mechanism. Furthermore, because a setting member and a frame securely form a channel, the cooling efficiency is improved and thereby, cooling is realized by a small fan. Therefore, these points are also advantageous for downsizing.

(3) By securing a liquid crystal panel to photosynthetic means such as a photosynthetic prism, it is possible to prevent the positional deviation between liquid crystal panels. Therefore, it is possible to improve reliabilities such as disturbance resistance, temperature change resistance, and handling resistance. Even when combining members with different thermal expansion coefficients and boding and fixing them, it is possible to prevent deviation and cracking due to temperature change resistance by setting an adhesive, bonding condition, and glass transition point most suitable for a working temperature range. Therefore, it is possible to prevent picture element deviation and correspond to a finer product.

(4) Because a control mechanism is omitted, the part cost and assembling cost can be decreased and moreover, expensive optical parts can be downsized. Thus, costs are greatly decreased.

(5) In particular, because the back-focus value of a projection lens can be decreased, it is possible to properly design the projection lens and moreover, increase the F value. Therefore, the projection light quantity is increased and the cost performance is further improved.

(6) Moreover, even if a defective liquid crystal panel is found in the manufacturing process of a factory or in a market, it is possible to replace the defective liquid crystal panel with a non-defective one and reproduce a product without using an exclusive alignment controller. Therefore, it is possible to greatly decrease the after-sale service cost and moreover, repair the defective liquid crystal panel for a short term and furthermore, improve the serviceability ratio and decrease the defective fraction in mass production of exclusive alignment controllers in a factory.

(7) Furthermore, there is an advantage that focus control can be omitted. Unless the screen size of a liquid crystal panel is changed in the design of a projection lens stressing the telecentric incident light, deviation of focus is further effective by using the fact that practical unclearness is relatively greatly allowed.

(8) Moreover, because a liquid crystal panel is protected by a shield case and a holding member, it is possible to prevent chipping, cracking, dielectric breakdown, or contamination which occurs in handling a product and thereby, improve the yield and after-sale serviceability.

(9) Furthermore, because an optical unit can be formed in which a projection lens, photosynthetic prism, and liquid crystal panel are integrated with a support frame, the handling characteristic and assembling characteristic are improved. Furthermore, it is possible to disuse a master lens for adjustment, decrease the man-hour for adjustment, and prevent bad influences due to deviation of the projection lens characteristic. Furthermore, there is a flexibility to be substituted for the cross dichroic mirror system.

(10) Furthermore, it is possible to integrate a support frame by replacing it with the frame of an optical system.

(11) Furthermore, a cooling-air channel is formed between each of three liquid crystal panels and the incident surface of a prism constituting photosynthetic means and thereby, the cooling effect can be improved.

FIG. 1 is a top view showing the structure of an optical unit of the liquid crystal projector of the first embodiment of the present invention.

FIG. 2 is a block diagram showing the structure of a controller for performing assembling and alignment control of the optical unit in FIG. 1.

FIGS. 3A and 3B are illustrations of an image displayed on a CRT when performing alignment control.

FIGS. 4A to 4C are local top views showing another structure of the setting member in FIG. 1.

FIG. 5 is a top view showing a part of the structure of an optical unit of the liquid crystal projector of another embodiment of the present invention.

FIG. 6 is an enlarged front view of the optical unit in FIG. 5.

FIGS. 7A and 7B are local sectional views of the embodiments in FIGS. 5 and 6.

FIGS. 7C and 7D are sectional views showing an application example of the embodiment in FIG. 7B.

FIG. 8 is a front view showing another structure of the frame and holding member of the embodiment in FIG. 6.

FIG. 9 is a front view showing the detail of the holding member in FIG. 8.

FIG. 10 is a front view showing still another structure of the frame and holding member of the embodiment in FIG. 6.

FIG. 11 is a front view showing the detail of the holding member in FIG. 10.

FIG. 12 is a top view showing the structure of a part of an optical unit of the liquid crystal projector of still another embodiment of the present invention.

FIG. 13 is a top view showing an application example of the embodiment in FIG. 12.

FIGS. 14 to 16 are top views respectively showing a part of an optical unit of the liquid crystal projector of still another embodiment of the present invention.

FIGS. 17A to 17C are top views respectively showing a part of an optical unit of the liquid crystal projector of still another embodiment of the present invention.

FIG. 1 is a top view showing the structure of an optical unit of the liquid crystal projector of an embodiment of the present invention. In FIG. 1, liquid crystal panels 1a, 1b, and 1c modulate red light 2a, green light 2b, and blue light 2c obtained by separating the light emitted from a light source (not illustrated) by a separating optical system (not illustrated) in accordance with an image signal output by a control circuit (not illustrated). A polarization plate 3 is arranged at the emitting side of each of the liquid crystal panels 12a, 1b, and 1c, which is attached and secured to the panel glass of each of the liquid crystal panels 1a, 1b, and 1c. A setting member 4 is formed into a prismatic shape made of glass, ceramic, or resin. One side of the prismatic shape is respectively bonded and secured to the both sides of the liquid crystal panels 1a, 1b, and 1c and a slope 4a is formed on the other side of it. A plurality of spacer members 5 are made of wedge-type glass and arranged under the slope 4a. A photosynthetic prism 6 incudes a dichroic layer, the light incident surface of the prism is arranged so as to face the liquid crystal panels 1a, 1b, and 1c. The image light modulated by the liquid crystal panels 1a, 1b, and 1c is synthesized by the dichroic layer and projected to a screen (not illustrated) by a projection lens 7. One side of the setting member 4 is bonded and secured to the panel glass surface of the liquid crystal panels 1a, 1b, and 1c. In this case, one side of the setting member 4 is bonded and secured to the outside of the polarization plate 3 as illustrated so that the setting member 4 does not cover or contact the polarization plate 3 of the emitting side. Moreover, a spacer member 5 is inserted into the gap with a triangular cross section formed by the slope 4a of the setting member 4 and the light incident surface of the photosynthetic prism 6 and they are mutually secured by a bonding layer formed in the minimum gap.

Then, the assembling and alignment control method is described below. The setting member 4 is secured to each of the liquid crystal panels 1a, 1b, and 1c by a photo-curing adhesive which is hardened by visible light and softened by heat to form a liquid crystal panel unit. Then, the liquid crystal panel unit is chucked by an alignment controller and transferred to the light incident surface position of the photosynthetic prism 6. Positional adjustment in X- and Y-axis directions vertical to the optical axis of the projection lens 7 and positional adjustment in the rotational directions of X.THETA. and Y.THETA. about X and Y axes-are performed and positioning adjustment is performed so that the liquid crystal surface is brought into the focal plane of the projection lens 7.

Then, a plurality of spacer members 5 coated with a photo-curing adhesive are inserted into the gap with a triangular cross section formed by the light incident surface of the photosynthetic prism 6 and the slope 4a of the setting member 4 to harden the adhesive by applying light such as ultraviolet radiation to the adhesive.

Then, focusing is performed also for the liquid crystal panels 1a, 1b, and 1c similarly to the above mentioned and moreover, rotation adjustment in X and Y directions and rotation adjustment of the surface formed by X and Y axes are performed by the alignment controller on the basis of the liquid crystal panel 1b so that picture elements fit each other. After positioning is completed, a wedge 5 coated with a photo-curing adhesive similarly to the above mentioned is inserted into the gap with a triangular cross section formed by the slope 4a of the setting member 4 and the light incident surface of the photosynthetic prism 6 and the adhesive is hardened by applying light such as ultraviolet radiation to the adhesive to form a prism unit.

FIG. 2 is a block diagram showing the structure of a controller for performing the above assembling and alignment control. In FIG. 2, a personal computer 100 connects with a CRT 101 and a memory 102 and drives a driving circuit 104 through a controller 103. The driving circuit 104 controls a six-axis manipulator 105 to perform the focus control and alignment control of the liquid crystal panels 1b, 1a, and 1c in FIG. 1. When the above types of control are completed, the driving circuit 104 drives an ultraviolet apparatus 107 and emits light such as ultraviolet radiation to harden the adhesive and secure the setting member 4 to the photosynthetic prism 6. In the case of the above types of control, an image passing through the projection lens 7 of the optical unit 106 is directly picked up by a CCD camera 108 or the image projected onto a screen is picked up by the camera 108 and the signal of the picked-up image is displayed on a CRT 110 through an image circuit 109.

FIGS. 3A and 3B are illustrations of the image displayed on the CRT 110 at the time of the above alignment. FIG. 3A shows a directly-displayed pattern 112 of each picture element of the liquid crystal panels 1a, 1b, and 1c. FIG. 3B shows a test pattern 113 displayed on the liquid crystal panels 1a, 1b, and 1c. An operator operates the personal computer 100 while viewing the displayed pattern and performs the above types of control while controlling the six-axis manipulator 105.

Then, other structures of the holding member 4 in FIG. 1 are described below. FIGS. 4A to 4C are illustrations showing other structures of the setting member 4. In the case of the structure in FIG. 4A, the spacer member 5 is set between the liquid crystal panel 1b and the setting member 4. The gap with a triangular cross section formed between the slope 4a and the liquid crystal panel 1b formed on the other side of the setting member 4 is not constant in most cases. Therefore, by dividing the gap into two or three portions vertically, it is possible to easily secure a bonding area adaptively to the shape of each inserting portion and decrease the value of protrusion to the outside. Thus, interference with an adjacent member can be prevented.

In the case of the example in FIG. 4B, the setting member 4 is integrated with the photosynthetic prism 6 so that assembling can be rationalized. In the case of the example in FIG. 4C, the adjacent setting member 4 is integrated and bonded and secured to a corner of the photosynthetic prism 6 as illustrated.

When a liquid crystal panel becomes defective after manufacturing the optical unit 106 or if a defective product is mixed, it is necessary to heat the bonding portion between each of the liquid crystal panels 1a, 1b, and 1c and the setting member 4 by a drier or a laser beam. Thus, the adhesive is softened by heating and the liquid crystal panels 1a, 1b, and 1c can smoothly be removed. In this case, because the setting member 4 is kept secured to the photosynthetic prism 6, the liquid crystal panel unit can be replaced by bonding and securing a non-defective liquid crystal panel unit to one side of the setting member 4. Moreover, in this case, because the mutual positional relation is not changed in the focus direction, it is possible to omit the focus control.

FIG. 5 is a top view showing the structure of a part of an optical unit of the liquid crystal projector of another embodiment of the present invention. FIG. 6 is an enlarged front view of the structure. In this case, portions different from the embodiment in FIG. 1 are described below. The frame 8 corresponding to the setting member 4 in FIG. 1 is made of a resin with a small thermal expansion coefficient (e.g. PPS or reinforced polycarbonate) having a high heat resistance and holds a holding member 9 made of metal. An L-type positioning portion 8a is protruded from four corners of the surface of the frame 8 and a slope 8b engaged with the wedge 5 is provided at the back of the frame 8.

A quadrangular window 9a is formed at the central portion of the holding member 9, and an adhesive to be hardened by visible light is applied to the circumference of the window 9a and the liquid crystal panel 1b is attached to the circumference to harden and fix the adhesive by applying light to the adhesive. Then, a non-light portion of the liquid crystal panel 1b is prevented from light by the frame portion around the window 9a. A flexible printed circuit board (FPC) 10 is conductively secured to the liquid crystal panel 1b by an anisotropic conductive film (ACF) 11 and extended to the outside from the recess of the frame 8. Moreover, a T-type elastic portion 9b is formed on the holding member 9, which is formed by being protruded from each side of the quadrangular frame of the body of the holding member 9 and expanded and the elastic portion 9b is temporarily secured to the positioning portion 8a of the frame 8 by using its elastic force. Then, corners of the body of the holding member 9 are permanently secured to the frame 8 by a visible-light-curing adhesive to be softened by heat and thus, a liquid crystal panel unit is formed. Moreover, the liquid crystal panels 1a and 1c are similarly set to the photosynthetic prism 6 and thus, a liquid crystal panel unit corresponding to each of the panels is formed. Assembling and alignment control are performed in the same manner as that of FIG. 1 and thus, a prism unit is formed.

To replace defective liquid crystal panels 1a, 1b, and 1c after forming the prism unit in FIGS. 5 and 6, it is necessary to remove the holding member 9 after softening the adhesive by heating the bonding portion between the holding member 9 and the frame 8 in the same manner as that of FIG. 1. Then, by reassembling the defective liquid crystal panel unit as a non-defective one, performing assembling and alignment control same as described above, and performing the same bonding and securing again, it is possible to reproduce a product. In this case, focus control can be omitted by keeping the accuracy of the liquid crystal surface position of the liquid crystal panel unit within the tolerance. However, the operability is further improved without using an exclusive alignment controller by preparing the condition so that the alignment control can be performed by a person.

FIGS. 7A and 7B are local sectional views of the embodiment in FIGS. 5 and 6. In FIG. 7A, a plurality of local bent portions 9c are formed at the margin of the body of the holding member 9 to prevent the adhesive of the liquid crystal panel 1b from flowing. Formation of the bent portions 9c is effective to improve the sticking force to the liquid crystal panel 1b when the adhesive has a high flowability.

In FIG. 7B, the slope at the head of a flat countersunk head screw 12 is engaged with the margin of the body of the holding member 9 to adjust the rotation in X- and Y-axis directions and in a plane including X and Y axes. An adhesive is applied to the threaded portion of the flat countersunk head screw 12. The adhesive uses the anaerobic-curing type which adheres to a purposed member by a screw tightening force and cures. It is also possible to increase the looseness torque by forming a resin film on the threaded portion. Moreover, only by setting the flat countersunk head screw 12 to the side where the position of the liquid crystal panel 1b is deviated and adjusting it, the other side can be supported by the spring force of the elastic portion 9b.

FIGS. 7C and 7D are local sectional views showing application examples of FIG. 7B. In the case of the example in FIG. 7C, an eccentric cam 13 set to a dowel is used instead of the flat countersunk head screw in FIG. 7B so as to obtain a friction torque. In the case of the example in FIG. 7D, an eccentric pin 14 is fitted into a hole instead of the eccentric cam 13. In these cases, the eccentric cam 13 or the eccentric pin 14 is secured by friction stop.

FIG. 8 is a top view showing another structure of the frame 8 and holding member 9 of the embodiment in FIG. 6. Four joints 9d are formed between the body of the holding member 9 and the elastic portion 9b and two dowels 8b provided on the frame 8 are fitted into holes 9e and 9f provided on the joints 9d and the holding member 9 is secured to the frame 8 by four screws 15. The screws 15 also prevent the body from deforming such as warping or twisting due to the reactive force of the elastic portion 9b.

To replace a defective liquid crystal panel with a non-defective one, the screws 15 must be removed to remove the defective liquid crystal panel unit. Then, the dowel 8b is cut off to temporarily fix the holding member 9 with a non-defective liquid crystal panel bonded by hanging the elastic portion 9b on the positioning portion 8a. Alignment control is performed by using the adjusting members 12, 13, and 14 shown in FIGS. 7B to 7D and thereafter, the holding member 9 is permanently fixed by the screws 15.

A structure for bonding and securing the liquid crystal panel 1b to the holding member 9 is described below by referring to FIG. 9. FIG. 9 is a front view of the holding member 9. The holding member 9 is set to a jig (not illustrated), the liquid crystal panel 1b is positioned, and a spindle (not illustrated) chucked in a vacuum state is lowered to set it onto the holding member 9. Under the above state, a visible-light-curing adhesive with a relatively high securing force is applied to a point 16a between the margin and the bent portion 9c of the liquid crystal panel 1b in the directions of 12, 4, and 8 o'clock of a clock. Then, visible light is applied to the adhesive to harden the adhesive and secure the liquid crystal panel 1b. Moreover, other portion 16b is reinforced and bonded by an elastic visible-light-curing adhesive like silicon resin. However, the other portion 16b can be omitted when the point 16a has a sufficient sticking strength. Moreover, by reinforcing the missing portion of the bent portion 9c with another member, the reinforcement effect is further obtained and the bent portion 9c is stabilized.

FIG. 10 is a top view showing still another structure of the frame 8 and holding member 9 of the embodiment in FIG. 6 and FIG. 11 is a top view showing the detail of the holding member 9. In the case of this embodiment, an elastic portion for temporarily fixing the frame 8 and holding member 9 is provided not on the holding member 9 but on the frame 8. Elastic portions 8c protruded from four corners of the body of the frame 8 contact the corners of the body of the holding member 9 to provide an elasticity for the corners and temporarily fix the body. Moreover, a protruded piece 9d of the holding member 9 is permanently fixed by the screw 15. Only the central portion connecting a pair of the elastic portions 8c is connected with the body of the frame 8 and other portions are lifted from the body of the frame 8. In the case of this embodiment, a case is shown in which position adjustment is performed at three points by a spacer 5.

FIG. 12 is a sectional view showing the structure of a part of the liquid crystal panel unit of still another embodiment of the present invention. In the case of this embodiment, a liquid crystal panel 1b is bonded and secured to shield cases 17a and 17b made of a conductive material such as metal in the same manner as that of the embodiment in FIG. 9. A quadrangular window is provided at the central portion of the shield cases 17a and 17b respectively and a window 17c provided on the shield case 17b has the same function as the window 9a provided on the holding member 9. Alignment control is performed similarly to the case of the embodiment in FIG. 1 to form a prism unit. By replacing the shield case 17b shown in FIG. 12 with the holding member 9 shown in FIG. 6, advantages of the both of them can effectively be shown.

FIG. 13 is a sectional view showing a modification of the embodiment in FIG. 12. This embodiment is an example when omitting the outside shield case 17b in a pair of shield cases 17a and 17b in FIG. 12.

In the case of the embodiments in FIGS. 12 and 13, a channel in the vertical direction (direction perpendicular to the paper surface) is formed by the light incident surface of a photosynthetic prism 6, setting member 4, and polarization plate 3 and thereby, the incident surface of the photosynthetic prism and the polarization plate 3 can effectively be cooled by supplying cold air from the bottom because there is not any obstacle.

FIG. 14 is a top view showing the structure of a part of the optical unit of still another embodiment of the present invention. In the case of this embodiment, a photosynthetic prism 6 is positioned and secured to a support frame 18. Liquid crystal panels 1a, 1b, and 1c are bonded and secured into three recesses provided on the support frame 18 through a spacer member 5 by a visible-light-curing adhesive to be softened by heating. Of course, alignment control is made in the same manner as that of FIG. 1. A support frame 18 forms an optical unit by securing a projection lens 7 with screws.

FIG. 15 is a top view of the optical unit of the application example of FIG. 14. In the case of this embodiment, two dowels 18a are provided on each recess of the support frame 18 in FIG. 14. Moreover, this embodiment uses a liquid crystal panel unit from which the elastic portion 9b of the holding member 9 in FIG. 5 is removed. Alignment control same as that of the embodiment in FIG. 1 is made possible by engaging holes 9e and 9f formed on the holding member 9 with dowels 18a so that backlash occurs. The dowels 18a are fixed with a visible-light-curing adhesive to be softened by heating. The structures in FIGS. 14 and 15 make it possible to replace a photosynthetic prism 6 with a dichroic mirror.

FIG. 16 is a sectional view of an embodiment in which the photosynthetic prism in FIG. 14 is replaced with a dichroic mirror 20. Moreover, a support frame 18 can be integrated with the frame of an optical system for supporting a mirror for separating lamp light into red, green, and blue or a mirror for leading reflected light. Furthermore, it is possible to form an optical unit by storing the prism units in FIGS. 1, 5, 8, and 12 in the support frame 18.

FIGS. 17A and 17B are top views showing the structure of a part of the optical unit of still another embodiment of the present invention. In the case of the embodiment in FIG. 17A, an outgoing-side polarization plate 3 is attached to the light incident surface of a photosynthetic prism 6 and a liquid crystal panel 1b is set very closely to the polarization plate 3. When alignment control is performed in the same manner as that of the embodiment in FIG. 1 and positioning is completed, the liquid crystal panel 1b is bonded and fixed by a spacer member 5.

In the case of the embodiment in FIG. 17B, a protrusion 3a with a slope is formed on the outgoing-side polarization plate 3 and the slope of the protrusion 3a is engaged with the slope of the spacer member 5 to secure a stable bonding force.

In the case of the embodiment in FIG. 17C, a transparent sheet member 19 is attached to the light incident surface of a photosynthetic prism 6. Moreover, an outgoing-side polarization plate 3 is attached to a liquid crystal panel 1b. The liquid crystal panel 1b is bonded and fixed by setting a spacer member 5 between the transparent sheet member 19 and the outgoing-side polarization plate 3. To reproduce a defective liquid crystal panel 1, the outgoing-side polarization plate 3 is removed and then reattached in the case of the embodiments in FIGS. 17A and 17B but the transparent sheet member 19 is removed and reattached in the case of the embodiment in FIG. 17C. Of course, it is possible to replace the liquid crystal panel 1 by removing the spacer member 5.

In the above embodiments, though drawings are omitted, a cooling fan is set at the bottom of the photosynthetic prism 6 in the cross-sectional direction. By blowing up cooling air by the cooling fan, produced heat is absorbed from the incident surface of a liquid crystal panel, outgoing-side polarization plate, and incoming-side polarization plate (not illustrated). Because the present invention makes it possible to omit a mechanism for alignment control and focus control, it is possible to expand a channel by a space equivalent to the omitted control mechanism. Moreover, it is possible to form a channel in the vertical direction by the setting member 4, frame 8, and support frame 18.