JPH11119185A - Autofocus device for LCD projector - Google Patents

Abstract

(57) [Summary] An object of the present invention is to provide an automatic focusing device for a liquid crystal projector which automates a focus adjusting means of a projection lens. A projection lens having focus adjusting means, a focus adjusting mechanism for adjusting the focus of the projection lens, and a movable reflecting mirror means disposed between the dichroic mirror or dichroic prism and the projection lens. And the reflected light from the screen S is received via the movable reflecting mirror means 3, converted into a received light output signal, and the projection lens 1 and the LCD 1
A light receiving element 5 disposed at a position equivalent to the optical axis distance of 4r, 14g, 14b, and a focus position up to the screen S is detected and calculated by a light receiving output signal from the light receiving element 5, and drive control of the focus adjusting mechanism 2 is performed. It comprises a focus adjustment controller 6 for performing the adjustment and a position detector 2 for detecting the adjustment position of the focus adjustment mechanism 2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an automatic focusing device for a projection lens of a liquid crystal projector.

[0002]

2. Description of the Related Art In a presentation system using a personal computer or the like, a liquid crystal projector is used as a large display device. In particular, small portable liquid crystal projectors that are convenient to carry change the installation location each time they are used, the installation conditions such as the screen size and the distance to the screen change, and the number of users of the device is unspecified. FIG. 5 is a conceptual diagram of an optical system of a liquid crystal projector according to the related art and a control block diagram of focus adjustment of a projection lens. White light is emitted from a light source L such as a metal halide lamp, and emitted as parallel rays from the condenser relay lens system 10. The dichroic mirror 11 has a filter on its surface that reflects blue (hereinafter, referred to as b) and transmits red (hereinafter, referred to as r) and green (hereinafter, referred to as g). The dichroic mirror 12 has a filter on its surface that reflects r and transmits b and g.
Reference numeral 13 denotes a general mirror whose reflection characteristics do not depend on the wavelength of light. The parallel rays separated into r, g, and b enter the LCDs 14r, 14g, and 14b for each color. L for each color
The CDs 14r, 14g, and 14b modulate the light based on the supplied video drive signal, and emit the modulated light of r, g, and b from the emission surface. The modulated light for each color is combined on the same optical axis by a dichroic mirror or a dichroic prism 4.
+ G + b, and is projected and output on the screen S by the projection lens 1. The focus adjustment of the projection lens 1 is performed by manually inputting a focus adjustment input unit provided in the operation unit 8. The control unit 9 issues a focus drive control command to the focus drive control unit 6 based on the input. The focus drive control unit 6 drives and outputs to the focus adjustment mechanism 2 according to the focus drive control command. As described above, in the liquid crystal projector for portable use, the optical axis adjustment, the focus adjustment, the screen size adjustment, etc., of the screen are performed at each installation, and the operation is complicated particularly for unfamiliar unspecified users. There is a high demand for automation of these operations.

[0003]

SUMMARY OF THE INVENTION An object of the present invention is to provide an automatic focusing device for a liquid crystal projector which automates a focus adjusting means of a projection lens in view of these requirements.

[0004]

A projection lens having a focus adjusting means, a focus adjusting mechanism for adjusting a focus of the projection lens, and a movable reflecting mirror means provided between a dichroic mirror or a dichroic prism and the projection lens. A light receiving element which receives reflected light from the screen via the movable reflecting mirror means, converts the light into a light receiving output signal, and is disposed at a position equivalent to the optical axis distance between the projection lens and the LCD; and a light receiving output signal from the light receiving element And a focus adjustment control unit that detects and calculates the focus position to the screen and controls the driving of the focus adjustment mechanism, and a position detector that detects the adjustment position of the focus adjustment mechanism. In addition, a relay lens of a convex lens or a concave lens is additionally provided equivalently between the movable reflecting mirror means and the light receiving element.

[0005] Further, the movable reflecting mirror means is a flat mirror formed on a flat glass substrate by forming a reflecting film such as a metal thin film which reflects a part of the total luminous flux. Further, the reflection film formed on the movable reflecting mirror means, a metal thin film that reflects a part of the total light flux, a filter that reflects only infrared light, a filter that reflects only ultraviolet light, Alternatively, a reflective film such as a metal thin film that reflects all light is formed on a part of the central part as a transmission surface and on other parts.

Further, the movable reflecting mirror means includes: a flat mirror having a reflecting film formed on a flat glass substrate, having a rotating shaft having both ends holding structure at one end, and a connecting portion such as a gear fixed to the rotating shaft; The connecting portion is composed of a driving source such as a DC motor that is driven to rotate from the outside and a bearing portion that holds the rotating shaft in a rotatable state, and the flat mirror is rotatably driven by the driving source on a flat glass substrate. A flat mirror having a reflection film formed on one end thereof, a rotating shaft of a both-end holding structure at one end, and a connecting portion such as a pulley or a rotating arm fixed to the rotating shaft, and an operation for manually operating the rotation of the flat mirror. A reflection film is formed on a flat glass substrate, comprising a button mechanism, a link unit for linking the movement of the operation button mechanism to the external drive unit, and a bearing unit for holding a rotating shaft in a rotatable state. Formed at one end A flat mirror having a connecting part such as a pulley or a rotating arm fixed to the rotating shaft, a linear driving means such as an electromagnetic plunger, and a link for linking the movement of the linear driving means to the connecting part. A reflection film is formed on a flat glass substrate, comprising a link portion and a bearing portion that holds the rotation shaft in a rotatable state. The reflection film is formed at one end, and a rotation shaft having both ends holding structure is provided. A flat mirror with a rotating lever fixed to the other end and a connecting part such as a pulley or a rotating arm fixed to the other end or one end, a link part linked to the connecting part and rotating the flat mirror in one direction, and a rotating shaft And a bearing part that holds the mirror in a possible state, and enables the manual rotation of the plane mirror by the rotation lever, or a reflection film is formed on a plane glass substrate, and both ends are formed as sliding parts. A flat mirror and a flat mirror The optical system has an optical housing having a sliding groove or a sliding surface capable of holding a sliding portion at a fixed angle and slidable, and moving the flat mirror within a cross section of the projected light beam during focus adjustment, and at normal time. It moves out of the projected light beam cross section.

Further, the light receiving element is a phototransistor,
Semiconductor devices such as photodiodes that perform photoelectric conversion,
CdS, PI to be a solar cell that generates photovoltaic
Photovoltaic cells such as Nb, PbS, InSb, etc. are arranged in a linear or two-dimensional manner as photoelectric array sensors, and photovoltaic cells such as BBDs, CCDs, solar cells are arranged in a line or A two-dimensionally arranged photovoltaic array sensor, a plurality of photoelectric cells such as PbS and InSb are three-dimensionally arranged three-dimensionally, or a plurality of photovoltaic cells such as a BBD, CCD, solar cell, etc. A three-dimensional sensor in which power-source cells are arranged three-dimensionally.

Further, the structure of the three-dimensional sensor is such that a plurality of light receiving elements such as photoelectric cells or photovoltaic cells are arranged on a flat substrate, and the central axis connecting the plurality of light receiving elements is the optical axis of the reflected light. A plurality of light-receiving elements, such as a plurality of photoelectric cells and photovoltaic cells, are placed on a parallel surface at an arbitrary distance on a transparent substrate such as glass, which is arranged so as to intersect at an arbitrary angle to form a three-dimensional sensor. And the three-dimensional sensor is disposed by arranging the parallel surface so as to intersect perpendicularly with the optical axis of the reflected light, or a reflecting surface is provided at an arbitrary distance in the optical axis direction. A plurality of light receiving elements such as a photoelectric cell and a photovoltaic cell are provided at positions corresponding to the three-dimensional sensor.

Further, the focus adjustment control unit controls the A / D which converts an output signal of the light receiving element into digital data.
(Analog / digital converter), a data memory for temporarily storing the digital signal, and a comparison operation between the digital data read from the data memory and the A / D output data to calculate and output difference data. A comparison operation unit, a focus control unit that generates and controls a control signal of the focus adjustment mechanism so that the differential value of the difference data becomes zero, and a drive source such as a DC motor of the focus adjustment mechanism driven by the control signal. And a drive unit for outputting. At the time of automatic focus adjustment, the focus mechanism is controlled to move in a fixed direction from the initially set focus position, and the position at which the differential value of the difference data becomes substantially zero is set and controlled as the optimum focus position. A / D for converting the output signal of the light receiving element into digital data, controlling the focus so that the absolute value of the difference data is at the center position between two points, A threshold value judging unit that outputs judgment data for comparing and judging whether the signal value exceeds a preset threshold value, and an area calculating unit that adds and outputs the judgment data to calculate and output the cross-sectional data of the light flux near the focal position of the reflected light. A data memory that temporarily stores the cross-sectional data, a comparison calculator that compares the cross-sectional data read from the data memory and the cross-sectional data from the area calculator, and outputs differential data,
A focus control unit that generates and controls a control signal of the focus adjustment mechanism so as to minimize the absolute value of the difference data, and a drive unit that drives and outputs a drive source such as a DC motor of the focus adjustment mechanism by the control signal. At the time of automatic focus adjustment, the focus mechanism is controlled to move in a fixed direction from the initially set focus position, and the point at which the absolute value of the difference data becomes minimum is set and controlled as the optimum focus position, or a three-dimensional sensor type light receiving element A / D for converting the output signal of the digital data into digital data, a difference calculator for calculating and outputting difference data of the plurality of digital data, a data memory for temporarily storing the difference data, and a difference data read from the data memory And a comparison operation unit that performs a comparison operation on the output data of the difference operation unit to calculate and output the comparison data, and a focus adjustment mechanism that minimizes the absolute value of the comparison data. A focus control section for generating and controlling a control signal; and a drive section for driving and outputting to a drive source such as a DC motor of a focus adjustment mechanism by the control signal. To control the optimal focus position and setting. Further, focus control is performed such that the absolute value of the difference data is at the center position between two points having the same value.

Further, the drive source of the focus adjusting mechanism is a stepping motor which feeds a fixed angle or a fixed sliding amount step by step for each pulse drive.

Further, the detector for detecting the adjustment position of the projection lens focus adjustment mechanism is rotation detection means for detecting the rotation angle of the rotary drive shaft or the number of rotation pulses of the rotary body.
Alternatively, it may be a straight line detecting means for detecting the sliding amount of the drive shaft or the number of sliding pulses of the sliding portion, or a movable limit position detecting means such as a limit switch.

[0012]

FIG. 1 is a block diagram of an optical system and main parts of an embodiment of an automatic focusing apparatus for a liquid crystal projector according to the present invention, and FIG. 2 shows a plurality of embodiments of movable reflecting mirror means according to the present invention. In FIG. 1, modulated light of each color of r, g, and b is combined by a dichroic prism 4 and emitted from an emission surface as combined light r + g + b, similarly to the related art. A movable flat mirror 3 on which a reflection film is formed is arranged between the projection lens 1 and the dichroic prism. This reflective film is a metal thin film that reflects a few percent of all light colors,
Alternatively, a filter film that reflects only light in the infrared region and transmits light in other regions is formed, or a filter film that reflects only light in the ultraviolet region and transmits light in other regions is formed. Or, or make a part of the central part a transmissive surface,
A metal thin film or the like that reflects all light is formed in other portions. At the time other than the focus adjustment, the plane mirror 3 is moved to a position 3 ′ other than the cross section of the projected light beam, and the light emitted from the dichroic prism 4 is enlarged and projected on the screen S by both the projection lenses 1. This is achieved by driving the lens focus adjustment unit by the focus adjustment mechanism 2.

For automatic focus adjustment, the operation unit 8
Enter the automatic focus adjustment mode. The control unit 9 receives the input, instructs the display signal generation unit 16 to generate a signal for focus adjustment (for example, a white circle or a white square only at the center of the screen), and sends an automatic focus adjustment mode command to the focus adjustment control unit 6.
Then, the plane mirror 3 is rotated or slid to move within the cross section of the projected light beam. The display signal generating unit 16 generates a signal for focus adjustment, and drives the LCD for each color via the LCD driving unit 17. This signal image for focus adjustment is formed on the screen S. The reflected light r '+ g' + b 'from the screen S is condensed by the projection lens, further refracted and reflected by the plane mirror 3, and has a distance equivalent to the distance from the projection lens 1 to the LCDs 14r, 14g, and 14b on the optical axis. An image is formed on the arranged light receiving element 5. The physical distance can be changed by inserting a relay lens 15 equivalent to a concave lens or a convex lens between the plane mirror 3 and the light receiving element 5, and the degree of freedom of the design arrangement of the light receiving element can be changed. Is secured.

In FIG. 2, (a) explains the formation of the translucent reflective film 3a of the plane mirror 3. This semi-transparent reflective film is formed of a metal thin film that reflects half of all light colors, or a filter film that reflects only light in the infrared region and transmits light in other regions, or light in the ultraviolet region. A filter film is formed that reflects only the light in other regions and transmits light in other regions.

(B) The semi-transparent reflection film 3 of the plane mirror 3
a total reflection film 3b having a circular or polygonal transparent portion 3c in the center instead of a. The light emitted from the central transparent portion is projected on a screen, and the reflected light is totally reflected except the central transparent portion. The light receiving element 5 is refracted and reflected by the reflection film 3b.
Image on top. During normal operation, the plane mirror is housed at the position 3 'outside the light beam cross section of the projected image, so that it does not affect the light beam of the projected image at all.

(C) shows a first embodiment of the movable reflecting mirror means according to the present invention. The plane mirror 3 has a rotating shaft 31 at one end, and is provided by a bearing provided in an optical system housing (not shown). Supported. The flat mirror 3 has a half-moon-shaped flat gear 32 press-fitted into a rotating shaft 31 and is driven to rotate by a flat gear 33 press-fitted into a DC motor 34 shaft. At the time of normal use, it is housed at the position of the plane mirror 3 ′, and the entire amount of light flux of the projected image from the dichroic prism 4 is emitted to the projection lens 1. In auto focus mode, DC
It is driven to rotate by a motor 34, rotates about 45 degrees, and is positioned by a stopper 43. Reflected light r '+ g' +
b ′ is a plane mirror 3 whose optical axis is refracted by 90 degrees and formed on the light receiving element 5.

(D) shows a second embodiment of the movable reflecting mirror means according to the present invention, in which the plane mirror 3 has a rotating shaft 31 at one end and is rotated by a bearing in an optical system housing (not shown). Supported. The rotating shaft 31 has a half-moon-shaped pulley 35.
Alternatively, the rotating arm is press-fitted. The pulley 35
A wire 36 for driving pulley rotation is locked on the outer periphery of the wire, and a weak tension spring 41 is locked on one end of the wire, and the tension spring 41 is locked on the housing locking portion 42. On the other hand, the other end of the wire 36 is locked to a sliding shaft 38 of the automatic focus adjustment push button 37. Push button 37
Is inserted through a through hole in the apparatus housing F via a strong pressing spring 40 inserted into the sliding shaft 38. Sliding shaft 38
In the vicinity of the wire locking portion, locking pieces such as a speed nut and a C ring 39 are provided to prevent the wire from coming out of the through hole. In a normal use state, the push button 37 is pushed out of the housing F by the force of P0 by the strong push spring 40, while the weak tension spring 41 pushes one end of the wire 36 to P
The wire 36 is driven to rotate the outer periphery of the pulley 35 by the force of P0-P1 because of the relationship of P0 >> P1. In this state, the plane mirror is stored at the position 3 '. When the push button 37 is pressed, the wire 36 is driven to rotate by the force of P1 by the weak tension spring 41, and the plane mirror 3 is rotated to the position where it hits the stopper 43. In the present embodiment, the configuration in which the same effect can be produced can be obtained by replacing the wire with a belt or lever, replacing the weak tension spring with a weak compression spring, and replacing the strong compression spring with a strong tension spring.

(E) shows a third embodiment of the movable reflecting mirror means according to the present invention. The plane mirror 3 has a rotating shaft 31 at one end, and is provided by a bearing provided in an optical system housing (not shown). Supported. The rotating shaft 31 has a half-moon-shaped pulley 35.
Alternatively, the rotating arm is press-fitted. The pulley 35
A wire 36 for driving the pulley to rotate is locked on the outer peripheral portion, and a weak tension spring 41 is locked on one end of the wire, and the tension spring 41 is locked on the housing locking portion 42. On the other hand, the other end of the wire 36 is locked by linear sliding means such as an electromagnetic solenoid 44. In normal use,
The tension spring 41 pulls one end of the wire 36 and drives the outer periphery of the pulley 35 to rotate. In this state, the plane mirror is stored at the position 3 '. In the automatic focus adjustment mode, the wire is pulled back by the electromagnetic plunger, the pulley is driven to rotate, and the plane mirror 3 is rotated to the position where it hits the stopper 43. Instead of the plunger, a linear drive means such as a linear drive motor can be selected.

(F) shows a fourth embodiment of the movable reflecting mirror means according to the present invention, wherein the plane mirror 3 has a rotating shaft 31 at one end, and is rotated by a bearing in an optical system housing (not shown). Supported. A lever 45 for manual operation is press-fitted to the outside of the bearing at one end of the rotating shaft 31, and a pulley 35 having a half-moon square shape is press-fitted to the other end. A wire 36 for driving the pulley to rotate is locked on the outer peripheral portion of the pulley 35, one end of the wire is locked with a tension spring 41, and the tension spring 41 is locked with a housing locking portion 42. I have. In a normal use state, the tension spring 41 pulls one end of the wire 36 and drives the outer periphery of the pulley 35 to rotate. In this state, the plane mirror is stored at the position 3 '. When the lever 45 is manually operated in the direction of the arrow, the plane mirror 3 rotates about the rotary shaft 31 to a position of the stopper 43 by about 45 degrees. Further, the movement of the lever 45 is linked to an input switch of the operation unit 8 (not shown), and the automatic focus adjustment mode is input. In this description, the lock mechanism and the unlock mechanism of the lever 45 are omitted, but the presence or absence thereof is a design choice in the apparatus of the present invention.

(G) shows a fifth embodiment of the movable reflecting mirror means according to the present invention, wherein the plane mirror 3 is provided with two sliding grooves 46 or sliding surfaces provided in the optical housing portion F. Left and right position 4
It is held in a slidable state between the seven. The two sliding grooves 46 or the sliding surfaces are formed such that the surface connecting them is at an angle of 45 degrees to the optical axis of the projected image. Therefore, when the plane mirror 3 is at the position 47a in the light beam of the projected image, the reflected light r '+ g' + b 'is refracted by 90 degrees by the plane mirror 3 and is imaged on the light receiving element 5. Normally, the plane mirror 3 is located at a position 46b outside the range of the light flux of the projected image, and the entire amount of light emitted from the dichroic prism 4 is projected and output on the screen by the projection lens 1. The description of the movement driving means of the plane mirror is omitted.

FIG. 3 is a diagram for explaining the relationship between the optical axis of the optical lens, the cross-sectional area of the light beam, and the light intensity, and conceptual diagrams of various embodiments of the light receiving element according to the present invention. In (1), the image is projected and output from the projection lens 1 to the center of the screen S.
Test signal white circle (○) or white square (□) for focus adjustment
The light flux 1a of the reflected light of the signal image is projected by the projection lens 1 at a distance from the projection lens 1 to the LCDs 14r, 14g, 14b
Is formed on the light receiving element 5 disposed at an equivalent distance. At the in-focus position 1d, the light beam cross-sectional area is the smallest and the light intensity at the center of the light beam is the largest. The cross section of the light beam before and after the focus position increases in proportion to the square of the distance from the focus position, and the light intensity at the center of the light beam decreases in inverse proportion to the cross-sectional area. From another viewpoint, the change (differential value) in the light beam cross-sectional area and the light intensity at the parfocal point 1d is substantially zero. The center position between two positions 1c and 1e on the optical axis having the same light beam cross-sectional area and light intensity coincides with the focal point position 1d. Utilizing these properties, the present application forms a focal position detecting unit.
(2) is to detect the light intensity of the light beam, the light receiving element,
Semiconductor devices for photoelectric conversion, such as phototransistors and photodiodes, solar cells for generating photovoltaic power, or photoelectric cells such as PdS and PIN were used.

In (3) and (4), the light receiving element is set to Pb for the purpose of detecting the sectional area 5d of the light beam or the diameter 5c of the light beam.
A photoelectric array sensor in which photoelectric cells such as S and InSb are arranged in a line or two-dimensional form, or BBD, C
A photovoltaic array sensor in which photovoltaic cells such as a CD and a solar cell are arranged in a line or two-dimensionally.

(5) In order to simultaneously detect the light intensity of at least two points on the optical axis, the light receiving element is made of PbS, Inb.
Multiple photoelectric cells such as Sb, or BBD, CC
D, a three-dimensional sensor in which a plurality of light receiving elements such as a solar cell were three-dimensionally arranged.

(A) shows a first embodiment of a three-dimensional sensor structure, in which a light receiving element such as a semiconductor element, a solar cell or a photoelectric cell is placed at different positions on the flat printed circuit board 5e in the optical axis direction. Placed. The flat printed circuit board had a function of a three-dimensional sensor by being disposed at an angle θ of 45 degrees with respect to the optical axis.

(B) shows a second embodiment of a three-dimensional sensor structure, in which a semiconductor element, a solar cell, or a photoelectric element is provided on an upper surface 5f1 and a lower surface 5f2 of a transparent base material 5f such as glass having parallel upper and lower surfaces. A three-dimensional sensor function is provided by arranging a light receiving element such as a shaped cell and arranging the reflected light so as to be vertically incident on the upper surface.

(C) shows a third embodiment of the three-dimensional sensor structure, in which reflection surfaces 5g10 and 5g20 inclined at 45 degrees (arbitrary angles are possible) with respect to the optical axis are provided at two positions on the optical axis.
A light receiving element such as a semiconductor element, a solar cell, or a photoelectric cell is arranged at a distance corresponding to the reflected optical axis and at the same position from the reflecting surface to provide a function of a three-dimensional sensor.

FIG. 4 is a block diagram of a main part of various embodiments of the focus adjustment control unit according to the present invention. (A) is an example of a system that detects the light intensity at the center of the optical axis to detect the focus position. The light intensity detection signal from the light receiving element 5 is converted into digital light intensity data by the A / D 61 and is temporarily stored in the data memory 62 at regular intervals together with the address data. The comparator 63 compares the data from the A / D 61 with the data read from the data memory 62 to calculate and output a differential value, or the address data in the data memory 62 equal to the data from the A / D 61. Is output.

A position detector 7 is provided for detecting the adjustment position of the projection lens focus adjustment mechanism. The position detector 7 includes a rotation detection unit that detects the rotation angle of the rotary drive shaft or the number of rotation pulses of the rotating body, a linear detection unit that detects the amount of slide of the drive shaft or the number of slide pulses of the slide unit, Alternatively, a movable limit position detecting means such as a limit switch is selectively installed.

Next, the automatic focus adjustment operation including the focus control section 64 will be described. Upon receiving the automatic focus adjustment command from the control unit 9, the focus control unit 64 issues a command to the driving unit of the movable reflecting mirror means to move the plane mirror 3 to within the light flux range of the projected image, and focuses on the driving unit 65. The adjustment mechanism 2 outputs an initial position movement control signal so as to move to the initial focus adjustment position of the projection lens. The drive section 65 drives the DC motor of the focus adjustment mechanism to drive and output the focal position of the projection lens so as to be an initial value. The position detector (limit switch) 7 detects the initial position that is the closest focus, and sends an initial position detection signal to the focus control unit 64. Upon receiving the initial position detection signal, the drive unit 65 stops the initial position movement control, subsequently outputs a far focus position movement control signal toward the far focus direction, receives data from the comparison operation unit 63, and When the position is detected, the focus position movement control signal is stopped, and a command is issued to move the plane mirror 3 out of the luminous flux range of the projection image.
The focus adjustment is completed.

If the adjustment process is followed in FIG. 3A, the initial position starts from 1f, and 1e, 1d, and 1e.
The optical axis sectional area and the light intensity change in the order of c and 1b.
The focus control unit 64 of (a) determines that the differential value is approximately 0 at the position of the light intensity data 1d, or that the light intensity data of 1e and 1c match, so that the half of the address data of 1e and 1c The fact that the position of the address data is the confocal position is used. Practical control is a method of stopping the far focus position movement control signal at a position where the differential value becomes approximately 0. After moving to the position 1c, a near focus position movement control signal is issued in reverse, and the differential value becomes approximately 0. A method of stopping at a position or a method of stopping the position detector 7 at a predetermined address position as a continuous rotation detecting means or a continuous straight line detecting means is selected. Furthermore, if a stepping motor is used as the drive source of the focus adjustment mechanism 2, it can be adjusted to the in-focus position by outputting a predetermined reverse pulse.

(B) is an example of a system for detecting a focal position by detecting a light beam cross-sectional area or a light beam diameter. Detection signals of a plurality of points from the light receiving element 5 by the line sensor 5c or the two-dimensional sensor 5d are converted into digital light intensity data by the A / D 61. The digital light intensity data is compared with a preset threshold value, and the number of data exceeding the threshold value is added by the area calculator 67 and output as cross-sectional data. This section data is temporarily stored in the data memory 62 together with the address data. The comparison calculator 63 compares the cross-section data from the area calculator 67 with the cross-section data read from the data memory 62 to calculate and output a differential value, or a data memory equal to the cross-section data from the area calculator 67. The address data in 62 is output. The focus control unit 64 outputs a focus shift signal so as to be at a focus position corresponding to the address data. Subsequent control forms are the same as those described in (A), and thus will not be described.

FIG. 3C shows an example of a system for detecting a focus position by detecting the distribution of light intensity on the optical axis using a three-dimensional sensor. The detection signals from the three-dimensionally arranged light receiving element (1) 51 and light receiving element (2) 52 are converted into digital light intensity data by the A / D 61, respectively. The two light intensity data are input to the difference calculator 68, where the difference calculation is performed, and the difference data is output. This difference data is temporarily stored in the data memory 62 together with the address data. The comparison calculator 63 compares the difference data from the difference calculator 68 with the difference data read from the data memory 62 to calculate and output the minimum difference data. The focus control unit 64 outputs a focus shift signal so as to be at a focus position corresponding to the address data. Subsequent control forms are the same as those described in (A), and thus will not be described.

[0033]

The present invention is embodied in the form described above and has the following effects. In a liquid crystal projector, reflected light of an image projected and formed on a screen is refracted and reflected by a movable reflecting mirror means provided between the projection lens 1 and a dichroic mirror or a dachroic prism to form an image on a light receiving element 5. Focus position detecting means;
The automatic focus adjustment of the projection lens is enabled by the focal position adjustment control unit 6 of the projection lens 1. Further, there has been provided an automatic focusing device for a liquid crystal projector having various movable reflecting mirror means, a focal position detecting means, and an automatic focusing control means.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an optical system and a main part of an embodiment of an automatic focusing device for a liquid crystal projector according to the present invention.

FIG. 2 is an explanatory view of various embodiments of a movable reflecting mirror means according to the present invention.

FIG. 3 is an explanatory diagram of a relationship between an optical axis of an optical lens, a light beam cross-sectional area, and light intensity, and conceptual diagrams of various embodiments of a light receiving element according to the present invention.

FIG. 4 is a main part block diagram of various embodiments of a focus adjustment control unit according to the present invention.

FIG. 5 is a conceptual diagram of an optical system of a liquid crystal projector according to the related art and a control block diagram of focus adjustment of a projection lens.

[Explanation of symbols]

S screen L Light source 1 Projection lens 2 Focus adjustment mechanism 3 Plane mirror 3a Translucent reflective film 3b Total reflective film 3c Transparent part 31 Rotating shaft 32, 33 Gear 34 DC motor 3 Pulley 36 Wire 37 Push button 38 Sliding shaft 39 C-ring REFERENCE SIGNS LIST 40 push spring 41 tension spring 42 housing locking part 43 stopper 44 electromagnetic plunger 45 rotation lever 46 sliding groove 4 dichroic prism 5, 51, 52, 5e1, 5e1, 5e2, 5f1, 5
f2, 5g1, 5g2 light receiving element 5a semiconductor element 5e flat printed circuit board 5f transparent base material 5g10, 5g20 reflection surface 6 focus adjustment control unit 7 position detector 8 operation unit 9 control unit 14r, 14g, 14b LCD 15 relay lens 16 display signal Control unit 17 LCD drive unit 61 A / D 62 Data memory 63 Comparison operation unit 64 Focus control unit 65 Drive unit 66 Threshold judgment unit 67 Area operation unit 68 Difference operation unit

Claims (30)

[Claims] A white light emitted from a light source is separated into three primary colors by a dichroic mirror or the like, and signals generated by a display signal generation unit are driven by a liquid crystal panel (hereinafter referred to as LCD) provided for each color. The light emitted from the LCD for each color is combined by a dichroic mirror or a dichroic prism, the combined light is projected on a screen by a projection lens, and the projection lens A projection lens having focus adjustment means, a focus adjustment mechanism for adjusting the focus of the projection lens, and the dichroic A movable reflecting mirror which is installed between a mirror or a dichroic prism and the projection lens and has a reflecting film formed on a surface thereof A light receiving element that receives reflected light from the screen via the movable reflecting mirror means and converts the reflected light into a light reception output signal, and is disposed at a position equivalent to an optical axis distance between the projection lens and the LCD; A focus adjustment control unit that detects and calculates a focus position to the screen based on a light reception output signal from a light receiving element and performs drive control of the focus adjustment mechanism; and a position detector that detects an adjustment position of the focus adjustment mechanism. Receiving the reflected light of the image projected on the screen via the movable reflecting mirror means, converting the reflected light into a received light output signal, detecting a focal position using the received light output signal, and the focus adjusting mechanism; An automatic focusing device for a liquid crystal projector, wherein the automatic focusing device is adjusted and controlled to an optimum focus position. 2. A relay lens of a convex lens or a concave lens is additionally installed equivalently between the movable reflecting mirror means and the light receiving element, and an optical axis distance between the projection lens and the light receiving element can be arbitrarily set. 2. The method according to claim 1, wherein
An automatic focusing device for a liquid crystal projector according to the above. 3. A mirror according to claim 1, wherein said movable reflecting mirror means is a flat mirror formed on a flat glass substrate by forming a reflecting film such as a metal thin film which reflects a part of the total luminous flux. Autofocus device for liquid crystal projector. 4. A reflecting film formed on said movable reflecting mirror means,
4. The automatic focusing device for a liquid crystal projector according to claim 3, wherein a metal thin film that reflects a part of the total luminous flux is formed. 5. A reflecting film formed on said movable reflecting mirror means,
4. The automatic focusing device for a liquid crystal projector according to claim 3, wherein the automatic focusing device is formed by a filter that reflects only infrared light. 6. A reflecting film formed on said movable reflecting mirror means,
4. The automatic focusing device for a liquid crystal projector according to claim 3, wherein the automatic focusing device is formed by a filter that reflects only ultraviolet light. 7. A reflecting film formed on said movable reflecting mirror means,
4. The automatic focusing device for a liquid crystal projector according to claim 3, wherein a part of the central part is a transmission surface, and a reflection film such as a metal thin film that reflects all light is formed in other parts. 8. A flat mirror in which said movable reflecting mirror means has a reflection film formed on a flat glass substrate, has a rotating shaft of a both ends holding structure at one end, and an external drive unit such as a gear fixed to said rotating shaft. And a drive source such as a DC motor that is driven to rotate by the external drive unit from the outside, and a bearing unit that holds the rotation shaft in a rotatable state, and the plane mirror is rotationally driven by the drive source. 3. The automatic focusing device for a liquid crystal projector according to claim 1, wherein: 9. A movable reflecting mirror means, comprising: a reflecting film formed on a flat glass substrate; one end having a rotating shaft of a both-end holding structure; and a connecting portion such as a pulley or a rotating arm fixed to the rotating shaft. A plane mirror, an operation button mechanism for manually operating the rotation of the plane mirror, a link section such as a wire for linking the movement of the operation button mechanism to the connection section, and the rotation axis is rotatable. 3. The automatic focusing device for a liquid crystal projector according to claim 1, wherein the automatic focusing device is constituted by a bearing portion which is held in a state. 10. A movable reflecting mirror means, comprising: a reflecting film formed on a flat glass substrate; one end having a rotating shaft having both ends holding structure; and a connecting portion such as a pulley or a rotating arm fixed to the rotating shaft. A plane mirror, a linear drive unit such as an electromagnetic plunger, a link unit for linking the movement of the linear drive unit to the connection unit, and a bearing unit for holding the rotating shaft in a rotatable state. 3. The automatic focusing device for a liquid crystal projector according to claim 1, wherein the automatic focusing device is configured. 11. The movable reflecting mirror means, wherein a reflecting film is formed on a flat glass substrate, one end has a rotating shaft of both ends holding structure, and a rotating lever is fixed to one end of the rotating shaft, and the other end or A flat mirror having a connecting portion such as a pulley or a rotating arm fixed to one end, a link portion linked to the connecting portion and rotating the flat mirror in one direction, and a bearing for holding the rotating shaft in a rotatable state; 3. An automatic focusing device for a liquid crystal projector according to claim 1, wherein said autofocusing device comprises a rotating part, and said rotating lever allows manual rotation of said plane mirror. 12. A movable mirror means comprising a flat mirror having a reflecting film formed on a flat glass substrate and having sliding portions at both ends, and a sliding portion of said flat mirror held at a fixed angle and slidable. An optical unit housing having a suitable sliding groove or a sliding surface, wherein the flat mirror is moved within the cross section of the projected light beam during focus adjustment, and is moved out of the cross section of the projected light beam during normal operation. 3. The automatic focusing device for a liquid crystal projector according to 1 or 2. 13. An automatic focusing device for a liquid crystal projector according to claim 1, wherein said light receiving element is a semiconductor element for performing photoelectric conversion such as a phototransistor or a photodiode. 14. The photodetector according to claim 1, wherein the photodetector is a solar cell that generates photovoltaic power.
An automatic focusing device for a liquid crystal projector according to the above. 15. The light receiving element according to claim 1, wherein the light receiving element is a photoelectric cell such as CdS or PIN.
An automatic focusing device for a liquid crystal projector according to the above. 16. The automatic focus for a liquid crystal projector according to claim 1, wherein said light receiving element is a photoelectric array sensor in which photoelectric cells such as PbS and InSb are arranged linearly or two-dimensionally. apparatus. 17. A photovoltaic array sensor in which photovoltaic cells such as BBDs, CCDs, and solar cells are arranged in a line or two-dimensionally as the light-receiving element. An automatic focusing device for a liquid crystal projector according to the above. 18. The automatic focusing device for a liquid crystal projector according to claim 1, wherein the light receiving element is a three-dimensional sensor in which a plurality of photoelectric cells such as PbS and InSb are three-dimensionally arranged. 19. The liquid crystal projector according to claim 1, wherein the light receiving element is a three-dimensional sensor in which a plurality of photovoltaic cells such as a BBD, a CCD, and a solar cell are three-dimensionally arranged. Auto focus device. 20. The structure of the three-dimensional sensor, wherein a plurality of light receiving elements such as photoelectric cells or photovoltaic cells are arranged on a flat substrate, and the central axis connecting the plurality of light receiving elements is reflected light. 19. A three-dimensional sensor which is disposed so as to intersect at an arbitrary angle with respect to an axis to form a three-dimensional sensor.
10. An automatic focusing device for a liquid crystal projector according to item 9. 21. A structure of the three-dimensional sensor, wherein a plurality of light receiving elements such as photoelectric cells and photovoltaic cells are provided on a parallel surface of a transparent substrate such as glass at an arbitrary distance, and the parallel surface is provided. Is arranged so as to intersect perpendicularly with the optical axis of the reflected light,
20. The automatic focusing device for a liquid crystal projector according to claim 18, wherein the automatic focusing device is a three-dimensional sensor. 22. The structure of the three-dimensional sensor, wherein a reflection surface is provided at an arbitrary distance in the optical axis direction, and a plurality of light receiving elements such as photoelectric cells and photovoltaic cells are provided at positions corresponding to the reflection surface. 20. The automatic focusing device for a liquid crystal projector according to claim 18, wherein a three-dimensional sensor is provided by disposing. 23. An image processing apparatus comprising: an A / D (analog / digital converter) for converting an output signal of the light receiving element into digital data; a data memory for temporarily storing the digital signal; A comparator for comparing the digital data read from the data memory with the A / D output data to calculate and output difference data; and controlling the focus adjustment mechanism so that the differential value of the difference data becomes zero. A focus control unit for generating and controlling a signal; and a drive unit for driving and outputting to a drive source such as a DC motor of the focus adjustment mechanism according to the control signal. A position where the differential value of the differential data becomes substantially zero is set and controlled as an optimum focus position.
Or the automatic focusing device for a liquid crystal projector according to 2. 24. The automatic focusing device for a liquid crystal projector according to claim 23, wherein the focus control is performed such that the optimum focus position is a center position between two points where the absolute values of the difference data are equal. 25. The focus adjustment controller according to claim 1, further comprising: an A / D for converting an output signal of said light receiving element into digital data; and judgment data for judging whether said digital signal value exceeds a preset threshold value. A threshold value judging unit for outputting, an area calculating unit for adding and outputting the judgment data to calculate and output cross-sectional data of the light flux near the focal position of the reflected light, a data memory for temporarily storing the cross-sectional data, and reading from the data memory A comparison calculator that compares the calculated cross-section data with the cross-section data from the area calculation unit to calculate and output difference data, and generates a control signal for the focus adjustment mechanism such that the absolute value of the difference data is minimized. A focus control unit for controlling;
A drive unit that drives and outputs a drive source such as a DC motor of the focus adjustment mechanism according to the control signal. At the time of automatic focus adjustment, the focus mechanism is controlled to move in a fixed direction from an initially set focus position, and the difference data 3. An automatic focusing device for a liquid crystal projector according to claim 1, wherein a point at which the absolute value of the minimum is minimum is set and controlled. 26. The automatic focusing device for a liquid crystal projector according to claim 25, wherein the focus control is performed such that the optimum focus position is a center position between two points where the absolute values of the difference data are equal. 27. A plurality of A / Ds for converting an output signal of the three-dimensional sensor type light receiving element into digital data, and a difference calculation for calculating and outputting difference data of the plurality of digital data, wherein the focus adjustment control unit is provided. Device, a data memory for temporarily storing the difference data, a comparison calculator for comparing the difference data read from the data memory and the output data of the difference calculator to calculate and output comparison data,
A focus control unit that generates and controls a control signal of the focus adjustment mechanism, and a drive unit that drives and outputs a drive source such as a DC motor of the focus adjustment mechanism by the control signal so that the absolute value of the comparison data is minimized. 3. The automatic focusing device for a liquid crystal projector according to claim 1, wherein at the time of automatic focusing adjustment, a position where the absolute value of the comparison data is minimum is set and controlled as an optimal focusing position. 28. A stepping motor which feeds a drive source of the focus adjusting mechanism at a constant angle or a constant sliding amount every one pulse drive, and generates and outputs a signal of a predetermined number of pulses as a control signal of the focus adjusting mechanism. 27. The automatic focusing device for a liquid crystal projector according to claim 24, wherein: 29. A detector for detecting an adjustment position of the projection lens focus adjustment mechanism as rotation detection means for detecting a rotation angle of a rotation drive shaft or a number of rotation pulses of a rotating body. 3. The automatic focusing device for a liquid crystal projector according to 1 or 2. 30. A detector for detecting an adjustment position of the projection lens focus adjustment mechanism, a linear detection means for detecting a sliding amount of a drive shaft or a number of sliding pulses of a sliding portion, or a movable device such as a limit switch. 3. An automatic focusing device for a liquid crystal projector according to claim 1, wherein said automatic focusing device is a limit position detecting means.