JPH11119184A - Automatic focusing device for liquid crystal projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an automatic focusing device for a liquid crystal projector which can automate a projection lens focusing means. SOLUTION: The automatic focusing device is constituted of a projection lens 1 having a focusing means, a focusing mechanism 2 for focusing the lens 1, a semitransparent reflection film means 3 arranged between a dichroic mirror or dichroic prism 4, a light emitting part 18 consisting of a light emitting element or the like arranged on a position equivalent to an optical axis distance between the lens 1 and an LCD 14 so as to emit focus position detecting projection light to a screen S, a light receiving part 5 consisting of a light receiving element or the like for receiving reflected light B from the screen S through the means 3 and converting the received light into a received light output signal, a focusing control part 6 for detecting and calculating a focus position up to the screen S by an output signal from the light receiving part 5 and controlling the drive of the mechanism 2, and a position detector 7 for detecting a position focused by the 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. 6 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 focus adjustment means, a focus adjustment mechanism for adjusting the focus of the projection lens, and a dichroic mirror or a translucent reflection film means provided between the dichroic prism and the projection lens. A light-emitting portion, which is disposed at a position equivalent to the optical axis distance between the projection lens and the LCD, and emits detection light for detecting a focus position on the screen, and a translucent reflection film for reflecting light from the screen; A light-receiving unit including a light-receiving element that receives light via a means and converts it into a light-receiving output signal, and a focus adjustment control that detects and calculates a focal position to a screen based on the light-receiving output signal from the light-receiving element and controls driving of a focus adjustment mechanism And a position detector for detecting an adjustment position of the focus adjustment mechanism. Further, between the translucent reflective film means and the light emitting unit and the light receiving unit, a relay lens of a convex lens or a concave lens is additionally provided equivalently.

Further, the semi-transparent reflective film means is a semi-transparent mirror in which a metal thin film or the like is deposited on a flat glass substrate, or a semi-transparent prism in which a metal thin film or the like is deposited on an inclined surface of the prism.

Further, the semi-transparent reflective film is formed by a semi-transparent reflective film of a metal thin film that reflects a part of the total light flux, formed by a filter that reflects only infrared light, or reflects only infrared light. The filter is formed by a filter that reflects only infrared light formed by the filter.

Further, the light emitting section is constituted by a light emitting element which emits the detected projection light and a modulator which drives the light emitting element at a high frequency.

Further, the light emitting element constituting the light emitting portion may be an LED that emits visible light, an infrared emitting laser diode or an LED with an infrared transmitting filter that emits infrared light, or an ultraviolet light that emits ultraviolet light. An optical laser diode or an LED with an ultraviolet light transmission filter is used.

Further, the light receiving section receives the detected projection light and converts it into a received light output signal, a filter for passing only the received light output signal component of the modulation frequency, and a detector for detecting the output signal from the filter. And

Further, the light receiving element constituting the light receiving section is a semiconductor element for photoelectric conversion such as a phototransistor or a photodiode, a solar cell for generating photovoltaic power, or a photoelectric type cell for CdS or PIN. PbS,
A three-dimensional sensor in which a plurality of photoelectric cells such as InSb is three-dimensionally arranged, or 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.

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

Further, the focus adjustment control section includes an A / D for converting the output signal of the light receiving element into digital data, a data memory for temporarily storing the digital signal, and a digital data read out of the data memory and A / D. A comparison operation unit for performing a comparison operation with the output data of D to calculate and output difference data; a focus control unit for generating and controlling a control signal of a focus adjustment mechanism so that a differential value of the difference data becomes zero; A plurality of A / Ds for converting an output signal of a three-dimensional sensor type light receiving element into digital data, and a plurality of digitals. A difference calculator for calculating and outputting difference data of data, a data memory for temporarily storing the difference data, and a difference calculation between the difference data read from the data memory and the difference memory A comparison operation unit that performs a comparison operation to output the comparison data by calculating the comparison data, a focus control unit that generates and controls a control signal of the focus adjustment mechanism so that the absolute value of the comparison data is minimized, And a drive unit that outputs a drive to a drive source such as a DC motor of the focus adjustment mechanism.

Further, 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.

Further, the drive source of the focus adjustment mechanism is a stepping motor that feeds a fixed angle or a fixed sliding amount step by step for each pulse drive, and generates and outputs a signal of a predetermined number of pulses as a control signal of the focus adjustment mechanism.

[0015] 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.

Further, the operation unit is provided with an automatic focus adjustment input unit and a manual focus adjustment input unit, and the display signal generation unit is provided with a focus adjustment adjustment signal generation unit. Is generated, and the detected and projected light is emitted from the light emitting unit, the detected and projected light is imaged and displayed on a screen, and the reflected light of the imaged detected and projected light is used as a light reception signal for focus position detection.

[0017]

FIG. 1 is a block diagram of an optical system and main parts of an embodiment of an automatic focusing device for a liquid crystal projector according to the present invention. FIG. 2 shows several embodiments of the translucent reflective film means according to the present invention. In FIG. 1, r, g and b
The modulated light of each color is synthesized by the dichroic prism 4 and emitted from the emission surface as synthesized light r + g + b, as in the prior art. A translucent mirror 3 having a translucent reflection film 3 formed between the projection lens 1 and the dichroic prism
a or the translucent prism 3b. This translucent reflective film 3 is a metal thin film that reflects a few% 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. I have. For this reason, dichroic prism 4
Of the combined light r + g + b emitted from the projection lens 1
Is projected and output on the screen S. The focus adjustment of the projection lens 1 is performed by driving the lens focus adjustment unit by the focus adjustment mechanism 2.

At the time of automatic focus adjustment, an automatic focus adjustment mode is input from the operation unit 8. The control unit 9 receives the input and sends a signal for focus adjustment (for example,
A command to generate a black circle or a black square only at the center of the screen is issued, and an automatic focus adjustment mode command is issued to the focus adjustment controller 6. The display signal generator 16 generates a signal for focus adjustment,
The LCD for each color is driven via the LCD drive unit 17. At the same time, a control command is issued to the light emitting unit 5 to output the detected projection light a. The detected projection light forms an image on a black image portion (the above-described black circle or black square image) at the center of the screen S. The reflected light b from the screen S is condensed by the projection lens, further refracted and reflected by the translucent reflection film means 3, and is projected on the optical axis from the projection lens 1 to the LCDs 14r, 14g,
An image is formed on the light receiving unit 5 arranged at an equivalent distance to the distance to 14b. This equivalent distance can be changed by inserting a relay lens 15 equivalent to a concave lens or a convex lens between the translucent reflective film means 3 and the light emitting section 18 and the light receiving section 5 so that the physical distance can be changed. The degree of freedom of arrangement in design is secured.

FIG. 3 shows a light emitting section 18 and a light receiving section 5 according to the present invention.
It is a key map of an Example of. (A) shows a light-emitting element in which a light-emitting element is fixed to a base material such as a printed circuit board, and is driven by a DC source to emit continuous detection projection light.
(B) is to selectively receive the detected projection light when receiving light,
The light emitting element 18a is modulated and driven by a modulator 18b with a 47 KHz high frequency signal. (C) is a light receiving section 5 corresponding to the continuous detection and projection light reception, in which the light receiving element 5a is fixed to a base material such as a printed circuit board, and the converted output signal is a DC signal. (D) is a light receiving section 5 corresponding to the reception of the high-frequency modulated detection projection light. The converted output signal from the light receiving element 50 is selectively output by a 47 KHz band-pass filter 51, linearly detected by a detector 52, and reflected light. Is output. By using the modulated projection light and selecting and inputting the light when receiving the projection light, it is possible to improve the accuracy of detecting the target focal position.

FIG. 4 is a diagram for explaining the relationship between the optical axis of the optical lens, the light beam cross-sectional area 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.
The light flux 1a of the detection projection light for focus adjustment is projected by the projection lens 1 so that the distance from the projection lens 1 to the LCDs 14r, 14g,
An image is formed on the light receiving unit 5 disposed at an equivalent distance from 14b.
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. A position 1c on two optical axes having the same light flux cross-sectional area and light intensity;
The center position between 1e coincides with the in-focus position 1d. Utilizing these properties, the present application forms a focal position detecting unit.

(2) is for detecting the light intensity of the light beam.
The light receiving element was a semiconductor element for photoelectric conversion such as a phototransistor or a photodiode, a solar cell for generating photovoltaic power, or a photoelectric cell such as PdS or PIN.

(3) 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 in the optical axis direction on a flat printed circuit board 5e. 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 the three-dimensional sensor structure, in which a semiconductor element, a solar cell, or a photoelectric element is provided on the upper surface 5f1 and the lower surface 5f2 of a transparent substrate 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) 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 position corresponding to the reflection optical axis and at the same distance from the reflection surface to provide a function of a three-dimensional sensor.

FIG. 5 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 section 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 comparison calculator 63 stores the data from the A / D 61 and the data memory 6.
The data read from 2 is compared and the differential value is calculated and output, or the address data in the data memory 62 equal to the data from the A / D 61 is calculated and 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 outputs an initial position movement control signal to the drive unit 65 so that the focus adjustment mechanism 2 moves to the initial focus adjustment position of the projection lens. The drive unit 65 drives the DC motor of the focus adjustment mechanism 2 to drive and output the focal position of the projection lens 1 to 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 the focus adjustment is completed.

4 (1), the initial position starts from 1f, and 1e, 1d, 1
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 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.

[0031]

The present invention is embodied in the form described above and has the following effects. In the liquid crystal projector, the detection projection light is emitted by the light emitting unit 18 and the reflection light of the detection projection light image projected and formed on the screen is reflected by the translucent reflection means provided between the projection lens 1 and the dichroic mirror or the dichroic prism. The focus position detecting means for refracting and reflecting the light to form an image on the light receiving unit 5 and the focus position adjustment control unit 6 of the projection lens 1 enable automatic focus adjustment of the projection lens. Furthermore, an automatic focusing device for a liquid crystal projector having various detecting means and automatic focusing control means has been provided.

[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 a plurality of embodiments of the translucent reflective film means according to the present invention.

FIG. 3 is a conceptual diagram of an embodiment of a light emitting unit 18 and a light receiving unit 5 according to the present invention.

FIG. 4 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. 5 is a main block diagram of various embodiments of a focus adjustment control unit according to the present invention.

FIG. 6 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 A detection projection light B reflected light 1 projection lens 2 focus adjustment mechanism 3 translucent reflective film means 3a translucent mirror 3b translucent prism 4 dichroic prism 5 light receiving unit 5a semiconductor element 5e flat printed board 5f transparent base material 5g10 , 5g20 reflective surface 5b, 50, 51, 52, 5e1, 5e2, 5f1, 5
f2, 5g1, 5g2 light receiving element 6 focus adjustment control unit 7 position detector 8 operation unit 9 control unit 14r, 14g, 14b LCD 15 relay lens 18 light emitting unit 18a light emitting element 18b modulator 52 filter 54 detector 61 A / D 62 Data memory 63 Comparison operation unit 64 Focus control unit 65 Drive unit 68 Difference operation unit

Claims (27)

[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 translucent reflective film means installed between a mirror or dichroic prism and the projection lens; A light-emitting unit, which is disposed at a position equivalent to the optical axis distance between the screen and the LCD, and includes a light-emitting element that emits detection projection light for detecting a focus position on the screen, and reflects the reflected light from the screen through the translucent reflection. A light receiving unit including a light receiving element that receives light via a film means and converts the light into a light receiving output signal, and a focus position to the screen is detected and calculated based on a light receiving output signal from the light receiving element, and drive control of the focus adjusting mechanism is performed. A focus adjustment control unit, comprising a position detector for detecting an adjustment position of the focus adjustment mechanism, receiving reflected light of the detected projection light image formed on the screen via the translucent reflection film means, Converting the reflected light into a received light output signal, detecting a focal position using the received light output signal, and controlling the focus adjustment mechanism to an optimum focus position. Autofocus device. 2. A relay lens, which is equivalent to a convex lens or a concave lens, is additionally provided between the translucent reflective film means and the light emitting unit and the light receiving unit, and an optical axis distance between the projection lens and the light receiving element is reduced. 2. The automatic focusing device for a liquid crystal projector according to claim 1, wherein the automatic focusing device can be arbitrarily set. 3. An automatic focusing device for a liquid crystal projector according to claim 1, wherein said semi-transparent reflection film means is a semi-transparent mirror obtained by depositing a metal thin film on a flat glass substrate. 4. An automatic focusing device for a liquid crystal projector according to claim 1, wherein said semi-transparent reflecting film means is a semi-transparent prism in which a metal thin film or the like is deposited on an inclined surface of the prism. 5. An automatic focusing device for a liquid crystal projector according to claim 1, wherein said translucent reflection film is formed of a metal thin film translucent reflection film which reflects a part of the total light flux. 6. The automatic focusing device for a liquid crystal projector according to claim 1, wherein said translucent reflection film is formed by a filter which reflects only infrared light. 7. The automatic focusing device for a liquid crystal projector according to claim 1, wherein said translucent reflection film is formed by a filter which reflects only ultraviolet light. 8. A light-emitting device comprising: a light-emitting element that emits the detection projection light; and a modulator that drives the light-emitting element at a high frequency, and has a light output obtained by high-frequency modulation of the detection projection light. 3. The automatic focusing device for a liquid crystal projector according to claim 1 or 2. 9. An LED which emits visible light, wherein said light emitting element is an LED which emits visible light.
9. The automatic focusing device for a liquid crystal projector according to claim 1, wherein the device is a (Light Emitting Diode). 10. An automatic focusing device for a liquid crystal projector according to claim 1, wherein said light emitting element is an infrared light emitting laser diode for emitting infrared light or an LED with an infrared transmitting filter. 11. The automatic focusing device for a liquid crystal projector according to claim 1, wherein said light emitting element is an ultraviolet light laser diode or an LED with an ultraviolet light transmitting filter which emits ultraviolet light. 12. A light-receiving element for receiving the detected projection light and converting it into a light-receiving output signal, a filter for passing only a light-receiving output signal component of the modulation frequency, and detecting an output signal from the filter. 3. An automatic focusing device for a liquid crystal projector according to claim 1, wherein said automatic focusing device is constituted by a detector that performs the operation. 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. An automatic focusing device for a liquid crystal projector according to claim 1, wherein said light receiving element is a three-dimensional sensor in which a plurality of photoelectric cells such as PbS and InSb are arranged three-dimensionally. 17. The automatic 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. Focusing device. 18. A 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 a central axis connecting the plurality of light receiving elements is reflected light. 17. 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.
8. The automatic focusing device for a liquid crystal projector according to 7. 19. The 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,
18. The automatic focusing device for a liquid crystal projector according to claim 16, wherein the automatic focusing device is a three-dimensional sensor. 20. 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. 18. The automatic focusing device for a liquid crystal projector according to claim 16 or 17, wherein the automatic focusing device is provided as a three-dimensional sensor. 21. 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. 22. The automatic focusing device for a liquid crystal projector according to claim 21, 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. 23. 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. 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. 24. A stepping motor for feeding a drive source of the focus adjustment mechanism by a fixed angle or a fixed sliding amount step by step for each pulse drive, and generating and outputting a signal of a predetermined number of pulses as a control signal of the focus adjustment mechanism. 24. The automatic focusing device for a liquid crystal projector according to claim 21, 22 or 23. 25. 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. 26. 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. 27. An automatic focus adjustment input section and a manual focus adjustment input section in the operation section, and a focus signal adjustment signal generation section in the display signal generation section. An adjustment signal is generated and the detection projection light is emitted from the light emitting unit, the detection projection light is imaged and displayed on the screen, and reflected light of the imaged detection projection light is used as a light reception signal for focus position detection. 3. The method according to claim 1, wherein
An automatic focusing device for a liquid crystal projector according to the above.