JPH08211275A - Zoom lens device for liquid crystal projector - Google Patents

Abstract

PURPOSE: To provide a zoom lens device for a liquid crystal projector which performs focusing and the fine adjustment of magnification after driving a front group lens and a rear group lens by each motor, previously storing driving information on each motor so that the front group lens and the rear group lens may move in an optical axis direction while keeping specified optical relation and moving the front group lens and the rear group lens to a specified position based on the driving information according to the designated magnification, for example, in the case where the device is constituted of two lens groups. CONSTITUTION: The front group lens 1a and the rear group lens 1b are driven by a driving motor for a front group 22 and a driving motor for a rear group 12, respectively. The driving information such as a zoom curve followed by the lenses 1a and 1b is previously stored and the driving motors 12 and 22 are driven based on the driving information. By designating a screen size and information on a distance to a screen and actuating the driving motors 12 and 22, the lenses 1a and 1b are moved from an initial position to a magnification position. Thereafter, focusing and the adjustment of the magnification are performed while confirming a picture on the screen.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a zoom lens device of a liquid crystal projector for enlarging and projecting an image appearing on a liquid crystal screen television or the like onto a screen or the like.

[0002]

2. Description of the Related Art In a conventional zoom lens apparatus for a liquid crystal projector, for example, in the case of a two-group zoom, a linear cam hole along the optical axis direction is formed in one of the two lens barrels, and the other lens barrel has a linear cam hole. A cam hole is formed in a spiral shape so as to regulate the amount of movement of the lens group in the optical axis direction, and the front lens group is connected to and supported by the rear lens group in the cam hole formed in each lens barrel. . For the lens group that needs to be moved in the optical axis direction for focusing, the lens mount is held by another lens barrel, and this lens barrel is connected to one of the lens barrels by a helicoid or the like. The lens group is movable in the optical axis direction with respect to the lens barrel. Therefore, when one of the two lens barrels is rotated about the optical axis, the lens groups are guided by the cam holes, and the respective lens groups move in the optical axis direction by an appropriate amount of movement to obtain the focal length. Will be changed. Further, when the lens barrel holding the focusing lens is rotated, the focusing lens advances and retreats in the optical axis direction by the helicoid mechanism to focus.

[0003]

As described above, in the conventional zoom lens device for a liquid crystal projector, a cam hole is formed in the lens barrel to mechanically drive the zoom. In order for the lens group to be zoom-driven along a desired zoom curve, the above-mentioned cam hole needs to be formed with high precision, which requires a high cost for machining the cam hole, and makes the zoom lens device expensive.

Further, in order for the lens group to move in the optical axis direction by a predetermined amount of movement, it must be in a predetermined position with respect to the cam hole in the initial state, and the initial focus adjustment work for that is complicated. Therefore, the assembly work requires time and effort.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a zoom lens device for a liquid crystal projector, which does not use a mechanical cam so as to reduce the processing cost and which does not require a labor for adjusting an initial focus.

[0006]

As a technical means for achieving the above object, a zoom lens device for a liquid crystal projector according to the present invention has a plurality of lens groups, and these lens groups are arranged in the optical axis direction. In a zoom lens device for a liquid crystal projector equipped with a zoom lens that advances and retracts to change the focal length, a drive motor is provided corresponding to each of the lens groups, and a plurality of lens groups are maintained while maintaining a predetermined optical relationship. The feature is that the driving motor is driven to change the focal length.

Further, in a zoom lens device for a liquid crystal projector having a plurality of lens groups and having a zoom lens for advancing and retracting these lens groups in the optical axis direction to change the focal length, each lens group is made to correspond to each of the lens groups. A drive motor is provided, and a lens position detecting means for detecting a predetermined position of each lens group is provided, and the plurality of lens groups are started from the predetermined positions detected by the lens position detecting means to maintain a predetermined optical relationship. It is characterized by changing the focal length.

Further, in a zoom lens device for a liquid crystal projector having a plurality of lens groups, and a zoom lens for advancing and retracting these lens groups in the optical axis direction to change the focal length, each lens group is made to correspond to each of the lens groups. A drive motor is provided, and a lens position detecting means for detecting a predetermined position of each lens group is provided, and the plurality of lens groups are started from the predetermined positions detected by the lens position detecting means to maintain a predetermined optical relationship. However, it is also characterized in that the focal length is changed, and the drive motor is driven to advance / retreat any one of the lens groups to bring the lens into focus.

[0009]

The driving information corresponding to the zoom curve to be followed by the plurality of lens groups at the time of zoom driving is stored in the memory, and the respective driving motors are driven according to the driving information. When you input the distance from the projector to the screen where the image is projected and the size of the screen, the microcomputer calculates the zoom factor and each drive motor is driven according to the zoom curve stored in the memory when the drive switch etc. is turned on. The lens groups move in the optical axis direction by the respective movement amounts. Then, the drive motor is stopped in a state where the zoom magnification is obtained.
Then, only the focusing lens group is driven by driving the drive motor so that the image is focused on the screen.
In this state, if the zoom magnification is not the desired one,
After each lens group is moved from the position to a desired magnification, the focusing lens group is moved again to perform focusing adjustment.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A zoom lens device for a liquid crystal projector according to the present invention will be specifically described below with reference to the illustrated embodiments. In this embodiment, the front lens group and the rear lens group are
A zoom lens device including one lens group will be described.

FIG. 1 is a schematic front view of this zoom lens device. Drive units 10 and 20 are arranged above the projection lens L at symmetrical positions on the outer surface of the lens barrel 1 housing the projection lens L. It is set up. 2 is a schematic cross-sectional view taken along line AA in FIG. 1. The projection lens L is composed of two lens groups, a front lens group 1a and a rear lens group 1b. The zoom drive state is shown in FIG. These lens groups 1a and 1b are held by lens mounts 3 and 4 in which guide bush portions 3a and 4a are loosely fitted to a guide rod 2 disposed below the projection lens L with the optical axis direction as the longitudinal direction. It is slidable along the optical axis.

A driving bush 4b is formed above the lens mount 4 of the rear group lens 1b, and the driving bush 4b is disposed below the rear group driving section 10 with the optical axis direction as the longitudinal direction. It is loosely fitted to the guide rod 5 and supports the lens mount 4 slidably in the optical axis direction. An input tongue piece 4c is provided on the side surface of the drive bush 4b so as to be directed laterally.

The rear lens group driving portion 10 is disposed on a pair of flange portions 11a and 11b which are formed on a part of the lens barrel 1 so as to be directed outward. A rear group drive motor 12 composed of a pulse motor is supported on the rear flange portion 11b, and the output screw of the rear group drive motor 12 has a male screw formed on its output shaft.
a is connected, and the drive screw 12a is supported by a holder bracket 14 having bearings 13a and 13b. A guide rod 15 is supported inside the holder bracket 14 with respect to the drive screw 12a. A drive bush 16 is slidably fitted in the guide rod 15 so as to be freely slidable.

As shown in FIGS. 1 and 2, the drive bush 16 is directed toward the drive screw 12a and a drive nut portion 17 is provided.
a is projected, and the side surface of the drive nut portion 17a is pressed by the drive screw 12a by the restoring force of itself. A part of the female screw to be screwed with the drive screw 12a is formed on the surface pressed by the drive screw 12a. Further, a spring arm 17b extends in the drive bush 16, and the tip end of the spring arm 17b faces the drive nut portion 17a and is pressed by the drive screw 12a. Therefore, the drive screw 12a is
When the drive nut portion 17a tries to separate from the drive screw 12a by being held between the drive nut portion 17a and the spring arm 17b, the drive nut 17a is restored by the restoring force of the drive nut portion 17a and the spring arm 17b. Are separated from the drive screw 12a.

A pair of locking tongues 18 project downward from the lower side of the drive bush 16 and the input tongue 4c is held by the pair of locking tongues 18. There is. Moreover, the locking tongue 18 is prevented from being separated from the input tongue 4c by the restoring force of the locking tongue 18 itself.

A position sensor 19, which is a lens position detecting means for detecting that the rear lens group 1b is at the initial position in zoom driving, is provided on the side of the lens barrel 1 by a photo interrupter or the like.

FIG. 3 is a schematic sectional view taken along the line BB in FIG. 1, showing a state in which the projection lens L is zoom-driven to the telephoto side. A driving bush 3b is formed in a part of the lens mount 3 holding the front lens group 1a, and a guide rod 6 supported in parallel with the optical axis of the projection lens L is loosely inserted in the driving bush 3b. The front lens group 1a is slidable in the optical axis direction. The drive bush 3b is provided with an input tongue 3c projecting laterally.

The front lens group driving section 20 has a pair of flange portions 21 arranged on the lens barrel 1 as in the rear lens group driving section 10 described above.
It is housed between a and 21b, and the rear flange part 21b
Drive motor 22 for the front group, which is a pulse motor, is connected to a drive screw 22a with a male screw formed on its output shaft, and this drive screw 22a is supported by holder bracket 24 via bearings 23a and 23b. Has been done. A guide rod 25 is supported on the holder bracket 24 at a position inside the drive screw 22a, and a drive bush 26 is slidably fitted on the guide rod 25. The drive bush 26 has the same structure as that of the drive bush 16 shown in FIG.
Further, as shown in FIG. 3, a drive nut portion 27a and a spring arm 27b, each of which is formed with a female screw to be engaged with the drive screw 22a, are provided, and the female screw portion of the drive nut portion 27a is a drive screw. In order to keep the screwed state by being pressed by 22a,
The drive nut 22a and the spring arm 27b make the drive screw 22a
Is sandwiched.

Similarly to the rear group drive section 10, a pair of locking tongue pieces 28 are provided on the lower side of the drive bush 26 so as to be directed downward, and the pair of locking tongue pieces 28 themselves. The input tongue 3c is held by utilizing the restoring force of the.

A position sensor 29, which is a lens position detecting means for detecting that the front lens group 1a is at the initial position in zoom driving, is provided on the side of the lens barrel 1 by a photo interrupter or the like.

The zoom lens device includes the drive motor
A microcomputer (not shown) for controlling the 12 and 22 is mounted. Further, drive information such as a zoom curve to be followed when the drive motors 12 and 22 operate is previously stored in a ROM or the like, and the drive motors are driven according to the drive information.
12 and 22 are activated.

A flange portion 7 is provided at the rear end of the lens barrel 1.
Is formed, and is connected to a liquid crystal optical system (not shown) through the flange portion 7.

On the control panel (not shown) of the zoom lens device, for example, a distance setting button from the zoom lens device to the screen for setting the magnification and a size setting button for inputting the size of the screen, Alternatively, a start button, a magnification adjustment button, a focus adjustment button, and the like are provided, and the operation described below is performed according to the operation of these buttons.

It should be noted that variations in the focal length due to individual differences that occur during the production of the projection lens may be measured in advance using a test chart or the like, and this data may be stored in the ROM or the like including the data.

The operation of the embodiment of the zoom lens device for a liquid crystal projector according to the present invention constructed as described above will be described below.

This zoom lens device is connected to the liquid crystal optical system in advance, and the projection lens L of the zoom lens device is installed so as to face the screen on which the image on the liquid crystal screen is to be projected. The main switch is turned on to activate the liquid crystal optical system and the zoom lens device. In the zoom lens device, when the main switch is turned on, the drive motors 12 and 22 are driven to move the front lens group 1a and the rear lens group 1b to the initial positions in zoom driving, and the position sensors 19 and 29 move these lenses 1a and 1b. Is detected to be in the initial position, the drive motors 12, 22 are stopped. In this state, the distance from the zoom lens device to the screen and the screen size are input by the distance setting button. Next, when the start button is operated, the drive motors 12 and 22 operate.
At the time of start, both of the lens groups 1a and 1b are at the initial positions in zoom driving, and the positions are detected by the position sensors 19 and 29. Then, according to the drive information stored in the memory, the drive motor 1 is moved to the position corresponding to the magnification obtained from the distance to the screen and the screen size.
2, 22 will be activated. When the rear group drive motor 12 operates, the drive screw 12a rotates.
Drive nut part 17 with a female screw threaded on a
The drive bush 16 provided with a and slidably fitted to the guide rod 15 is guided by the guide rod 15 to move. The lens mount 4 is connected to the drive bush 16 via the locking tongue piece 18 and the input tongue piece 4c, and the rear lens group 1b is held by this lens mount. Therefore, the rear lens group 1b is moved in the optical axis direction. Will move. The lens mount 3 is connected to the front group drive motor 22 via a drive screw 22a, a drive nut portion 27a, a drive bush 26, a locking tongue 28, an input tongue 3c, and the like. Since the group lens 1a is held, the front group drive motor 22
The operation of causes the front lens group 1a to move in the optical axis direction.

When the driving information stored in advance reaches the input magnification, the drive motors 12 and 22 are stopped and the image on the liquid crystal screen is projected on the screen at a predetermined magnification. In this state, if an image of a desired size is obtained and the projected image is in focus, the operation of the zoom lens device ends.

However, since the distance information to the screen input first is a rough one, the image may not be focused on the screen in some cases. In this case, operate the focus adjustment button to move the front group drive motor.
22 is operated independently of the drive information stored,
While visually observing, the front lens group 1a is moved until the image is focused on the screen. With the focus on the screen,
If the magnification is not the desired one, operate the magnification adjustment button to operate the drive motors 12 and 22, and visually check the front lens group 1a and the rear lens group 1b until the desired magnification is achieved. Move in the optical axis direction. When an image with a desired magnification is obtained, the focus adjustment button is operated again to move the front lens group 1a so that the image is focused on the screen, and focus adjustment is performed. Then, the operation of the magnification adjustment button and the focus adjustment button is repeated until the desired focus is achieved. Therefore, when the magnification adjustment button and the focus adjustment button are operated, the front lens group 1a and the rear lens group 1b are driven without following the drive information stored in advance.

In the operation described above, it is described that the front lens group 1a and the rear lens group 1b move to the initial positions when the main switch is turned on. However, for example, when the zoom lens device and the screen are permanently installed. However, it is inconvenient because the magnification and focus must be adjusted each time the main switch is turned on. Therefore, for example, if a set switch is provided to adjust the magnification and focus, and the set button for operating this set switch is pressed, the projection lens will move to its zoom position regardless of whether the main switch is on or off. It is convenient if you keep it. Then, in order to cancel the maintenance of the zoom position, a reset button or the like may be operated.

[0030]

As described above, according to the zoom lens device for a liquid crystal projector according to the present invention, the drive motor is operated so that the projection lens holds a predetermined optical relationship in the ROM or the like to perform the zoom drive. Since the driving information for the driving is stored in the memory and the projection lens is driven according to the driving information, it is not necessary to form a cam hole or the like in the lens barrel. Therefore, since a mechanical cam is not used, the processing cost of the cam hole and the like becomes unnecessary, and the manufacturing cost of the zoom lens device can be reduced.

Further, unlike the case of using a mechanical cam, the work of adjusting the initial focus becomes unnecessary, and the labor of this adjusting work can be saved.

[Brief description of drawings]

FIG. 1 is a front view of a zoom lens device for a liquid crystal projector according to the present invention.

FIG. 2 is a schematic cross-sectional view taken along the line AA in FIG. 1, showing a state where the projection lens has moved to the wide-angle side.

FIG. 3 is a schematic cross-sectional view taken along the line BB in FIG. 1, showing a state where the projection lens has moved to the telephoto side.

[Explanation of symbols]

 L shooting lens 1 lens barrel 1a front group lens 1b rear group lens 5 guide rod 6 guide rod 10 rear group drive unit 12 rear group drive motor 19 position sensor (lens position detection means) 20 front group drive unit 22 front group drive Motor 29 Position sensor (lens position detection means)

Claims (3)

[Claims] 1. A zoom lens device for a liquid crystal projector, comprising: a zoom lens having a plurality of lens groups, wherein the zoom lens is configured to advance and retreat in the optical axis direction to change the focal length. A zoom lens device for a liquid crystal projector, wherein a drive motor is provided to drive a plurality of lens groups while maintaining a predetermined optical relationship to drive each drive motor to change a focal length. 2. A zoom lens device for a liquid crystal projector, comprising: a zoom lens having a plurality of lens groups, wherein the lens groups are moved forward and backward in the optical axis direction to change the focal length. A driving motor is provided, lens position detecting means for detecting a predetermined position of each lens group is provided, and a plurality of lens groups are started from the predetermined positions detected by the lens position detecting means to maintain a predetermined optical relationship. However, the zoom lens device for liquid crystal projectors is characterized by changing the focal length. 3. A zoom lens device for a liquid crystal projector, comprising: a zoom lens having a plurality of lens groups, wherein the lens groups are moved forward and backward in the optical axis direction to change the focal length. A driving motor is provided, lens position detecting means for detecting a predetermined position of each lens group is provided, and a plurality of lens groups are started from the predetermined positions detected by the lens position detecting means to maintain a predetermined optical relationship. A zoom lens device for a liquid crystal projector, wherein the focal length is changed while driving the drive motor to advance or retreat any of the lens groups to bring the lens into focus.