JPH0933880A - Liquid crystal projector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To automatically return an extension lens barrel to an initial position when a power source of a liquid crystal projector is turned OFF. SOLUTION: This projector is constituted of a lens part 1 having the extension lens barrel setting up a lens on a prescribed position in the lens barrel, a drive part 2 constituted of e.g. a DC motor moving the lens barrel of the lens part 1 along an optical axis, a gear of a motor shaft and the gear, etc., set up on the outer peripheral part of the lens barrel interlocked with the gear, a drive control part 3 controlling the operation moving the lens barrel by the drive part 2, a positional detection part 4 constituted of e.g. an optical encoder, etc., detecting the lens barrel position, the power switch 5 of the liquid crystal projector, a decision part 6 deciding the position, a memory 7 storing the initial position of the extension lens barrel and a control part 8 controlling respective parts.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal projector having a retractable lens barrel.

[0002]

2. Description of the Related Art Conventionally, a compact and portable liquid crystal projector shown in FIG. 5 has a main body 11 provided with a lens barrel 12 of a retractable type. In this liquid crystal projector, for example, a transmissive screen (not shown) is installed at a front facing position, and an image is projected on the transmissive screen. This time,
The size of the image (zoom) is adjusted by moving the position of the extension type lens barrel 12 back and forth according to the distance from the main body 11 to the transmissive screen, and the required lens inside the extension type lens barrel 12 is moved. Then, the sharpness (focus) of the image is adjusted.

When the above-mentioned zoom adjustment is mainly performed, the extension type lens barrel 12 is extended or retracted to change the length of the lens barrel. However, the main body 11 is compact, and the depth thereof is designed so that the tip end thereof is just housed in the main body 11 when the amount of extension of the extension type lens barrel 12 is the minimum (initial) state.

Therefore, in general, when zoom adjustment is performed, the tip of the extension type lens barrel 12 is projected to the outside of the main body 11.

However, when the liquid crystal projector is transported in the state where the above-mentioned extension type lens barrel 12 projects to the outside of the main body 11, the extension type lens barrel 12 may collide with something and a lens or the like may be damaged. There was a big risk of causing this.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and a liquid crystal projector in which a retractable lens barrel is set to the shortest (initial) state when the power is turned off and automatically returned to a position where it is housed in the main body. The purpose is to provide.

[0007]

In order to achieve the above object, a lens portion having a lens barrel of a pay-out type, a driving portion for moving the lens barrel of the lens portion along an optical axis, and a driving portion of the driving portion are provided. A drive control unit that controls a moving operation, a position detection unit that detects the position of the lens barrel or an amount corresponding to the position, a power switch of the liquid crystal projector, and a memory that stores the initial position of the extension type lens barrel. The determination unit that determines the current position of the lens barrel based on the initial position and the control unit that controls each unit.

[0008]

With the above-described structure, when the power switch is turned off, the drive control section controls the drive section to move the lens barrel backward, and the position detection section corresponds to the position or position of the lens barrel. The determination unit determines whether or not the lens barrel is at the initial position.If the lens barrel does not reach the initial position, the lens barrel is further moved backward, and the lens barrel is moved when the lens reaches the initial position. Stop.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A liquid crystal projector according to the present invention will be described in detail below with reference to the drawings. FIG. 1 is a block diagram of an embodiment of a liquid crystal projector according to the present invention. Reference numeral 1 denotes a lens unit having a lens barrel of a retractable type, which houses a lens at a required position in the lens barrel. 2 is a drive configured to move the lens barrel of the lens unit 1 along the optical axis, for example, a DC motor, a gear of the motor shaft, and a gear installed on the outer peripheral portion of the lens barrel that interlocks with the gear. It is a department. Reference numeral 3 is a drive control unit that controls the operation of the drive unit 2 to move the lens barrel. Four
Is a position detection unit that detects the position of the lens barrel, and is composed of, for example, an optical encoder. Reference numeral 5 is a power switch of the liquid crystal projector. Reference numeral 6 is a determination unit that determines the position. Reference numeral 7 is a memory for storing the initial position of the extension type lens barrel. Reference numeral 8 denotes a control unit that controls each unit.

FIG. 2 is a sectional view of the lens portion of the liquid crystal projector according to the present invention. Reference numeral 12 is a pay-out type lens barrel for zooming, in which a lens 18 is installed at the tip and a helicoid-shaped guide groove 17 provided along the optical axis is provided on the wall inside the lens barrel.
Reference numeral 13 is provided with a flange 13a for attaching to the main body 11 of the liquid crystal projector, a rotary ring 19 is rotatably attached to the outside of the tip, a fixed lens is attached to the inside of the tip, and a focus is provided on the outside of the middle portion It is a fixed lens barrel having a lens that moves along the optical axis inside the intermediate portion while attaching the rotating ring. 14
Is a gear 16 that is fixed to the fixed lens barrel and transmits power.
Is a motor such as a DC motor. 1
Reference numeral 9 denotes a rotating ring attached to the tip of the fixed lens barrel 13, and a pin provided at the tip of a support rod 15 provided in parallel with the optical axis is used as a helicoid-shaped guide groove for the payout type lens barrel 12. A gear 16 attached to the shaft 14 a of the motor 14 is meshed with teeth fitted in the outer peripheral portion of the motor 17.

Reference numeral 20 is a disc having a slit attached to a required position of the shaft 14a of the motor 14. 21a
Is a magnet, for example, attached to the rear end of the extension type lens barrel 12. Reference numeral 21b is a Hall element provided on the outer peripheral portion of the rotary ring 19 at a position corresponding to the magnet 21a.

The operation of moving the lens barrel of the liquid crystal projector according to the present invention to the initial position will be described with reference to FIGS. When the power switch 5 shown in FIG. 1 is turned off, the drive control unit 3 controls the drive unit 2 so as to move the lens barrel of the lens unit 1 backward, and the position detection unit 4 controls the current position of the lens barrel. The amount corresponding to the current position is detected, and the determination unit 6 determines the current position of the detected lens barrel or the amount corresponding to the current position based on the initial position data stored in the memory 7. As a result of the determination, when the current position is not the initial position, the drive control unit 3 further moves the lens barrel backward through the driving unit 2, and when the initial position is reached, the lens barrel is stopped.

The position detection and movement of the lens barrel will be described in more detail with reference to FIG. When the power switch 5 is turned off as described above, the drive control unit 3 rotates the motor 14 in a predetermined direction in the direction in which the pay-out type lens barrel 12 is retracted. When the gear 16 rotates in a corresponding direction to drive the teeth on the outer peripheral portion of the rotating ring 19 and the supporting rod 15 and the pin at the tip rotate as the rotating ring 19 rotates in a predetermined direction, the pin extends. Since the lens barrel 12 moves in the helicoid-shaped guide groove 17 provided in the lens barrel 12, the lens barrel 12 of the same extension type moves so as to contract in the optical axis direction. At this time, by providing an optical encoder on the shaft 14a of the motor 14, the position detection unit 4 can measure light pulses, and the initial position is determined from the number of the pulses.

FIG. 3 is a diagram for explaining the principle of the optical encoder of the liquid crystal projector according to the present invention. Along with the rotation of the disk 20 having a slit fixed to the shaft 14a, pulsed light in which the light output from the light emitting diode is intermittent is received by the light receiving element 20.
Input to a. Therefore, the position detector 4 counts the number of pulses for right rotation and the number of rotation for left rotation with positive and negative signs, respectively, so that the cumulative number of pulses is 0 at the initial position, for example.
It is.

FIG. 4 is a block diagram of a second embodiment of the liquid crystal projector according to the present invention. It should be noted that the same parts as those in FIG. What is FIG.
Differs in that the detection signal is obtained from the lens unit 1. Actually, as shown in FIG. 2, for example, a magnet 21a is attached to the rear end portion of the pay-out type lens barrel 12, and a hall element 21b is attached to the outer peripheral portion of the rotary ring 19 at a position corresponding to the magnet 21a. Since it is provided, the distance between the magnet 21a and the Hall element 21b becomes closer as the rotating ring 19 rotates,
The initial position is the closest position, and this can be judged by the strength of the magnetic force detected by the Hall element 21b.

For detecting the initial position, a reed switch may be installed on 21b so that the projection of 21a operates the reed switch at the initial position. Also,
The motor 14 of the drive unit 2 is a stepping motor,
The position detection unit 4 may detect the initial position from the pulse generated by the drive control unit 3 and the rotation direction data.

[0017]

As described above, the present invention provides a liquid crystal projector in which, when the power is turned off, the retractable lens barrel is put in the shortest (initial) state and automatically returned to the position where it is housed in the main body. Therefore, when transporting the liquid crystal projector, there is an advantage that it is possible to prevent damage accidents such as a lens. In addition, there is an advantage that the liquid crystal projector is compact and does not take up space when it is stored.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a liquid crystal projector according to the present invention.

FIG. 2 is a sectional view of a lens portion of a liquid crystal projector according to the present invention.

FIG. 3 is a diagram illustrating the principle of an optical encoder of a liquid crystal projector according to the present invention.

FIG. 4 is a block diagram of a second embodiment of a liquid crystal projector according to the present invention.

FIG. 5 is an external view of a compact, portable liquid crystal projector.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 lens part 2 drive part 3 drive control part 4 position detection part 5 power switch 6 judgment part 7 memory 8 control part 11 liquid crystal projector body 12 feed-out type lens barrel 13 fixed lens barrel 13a flange 14 motor 14a shaft 15 support rod 16 Gear 17 Guide groove 18 Lens 19 Rotating ring 20 Disc 20a Light receiving element 20b Light emitting diode 21a Magnet 21b Hall element

Claims (6)

[Claims] 1. A lens unit having a lens barrel of a pay-out type,
A drive unit that moves the lens barrel of the lens unit along the optical axis, a drive control unit that controls the movement operation of the drive unit, and a position detection unit that detects the position of the lens barrel or an amount corresponding to the position. A liquid crystal projector comprising a power switch, a memory for storing the initial position of the lens barrel, a determination unit for determining the current position of the lens barrel based on the initial position, and a control unit for controlling each unit. projector. 2. The liquid crystal projector according to claim 1, wherein the extension type lens barrel is returned to an initial position when a power switch is turned off. 3. The liquid crystal projector according to claim 1, wherein the position detector is an optical encoder. 4. The liquid crystal projector according to claim 1, wherein the position detector is formed of a Hall element. 5. The liquid crystal projector according to claim 1, wherein the position detector is composed of a reed switch. 6. The liquid crystal projector according to claim 1, wherein the drive unit is a stepping motor.