JP2835838B2 - Auto focus projector - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an autofocus projection device.

2. Description of the Related Art Referring to FIG. 8, a conventional autofocus projection apparatus has an autofocus lens system b and a projection lens c mounted on a mirror a and a head h. Manuscript d
The projection image passing through the projection lens c passes through a projection lens c, is reflected by a mirror a, and is enlarged and projected on a screen e. At this time, the distance of the optical axis from the mirror a to the screen e is i. In this state, the autofocus lens system b measures the distance to the screen e. The distance i is estimated by this distance measurement.

Problems to be Solved by the Invention However, when the image which was rectangular at the point A of the screen e is raised to the point B by changing the inclination of the mirror a as shown by a broken line, the image becomes as shown in FIG. It becomes distorted and trapezoidal.

At this time, the distance g of the optical axis from the mirror a to the screen becomes i = gcosα, which increases. That is, the autofocus lens system b
In the method of directly measuring the distance between the camera and the screen e, the auto focus does not operate correctly.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an autofocus projection device that can reduce trapezoidal distortion of a projected image caused by a change in a projection position and can form an image correctly.

Means for Solving the Problems The means for solving the present invention are as follows. That is, in an autofocus projection device that projects an image of a projection object on a screen by a projection lens, an adjustment unit that forms the image of the projection object on the screen includes the projection lens, a signal generation unit, and a signal reception unit. And the projection lens, the signal generation unit and the signal reception unit are arranged so as to be movable together with respect to the projection object, and the signal generation unit is disposed substantially along the optical axis of the projection lens. The signal receiving unit receives the signal reflected from the screen substantially along the optical axis of the projection lens and outputs an output signal according to the distance to the screen. Then, the projection lens and the projection object are relatively moved in a direction perpendicular to the optical axis of the projection lens, and the image of the projection object is displayed on the screen. On the other hand, an image of the projection object is formed on the screen in accordance with an output from the signal receiving unit, and the projection lens is relatively moved with respect to the projection object in a direction substantially perpendicular to the optical axis. At the same time, by moving the signal generation unit and the signal reception unit together with the projection lens, the image of the projection object on the screen can be moved with little distortion, and the optimal focus is always maintained. An autofocus projection device, characterized in that it is configured to be obtained.

Embodiment An outline of an embodiment of the present invention will be described first with reference to FIG. 1 and FIG.

The overhead projector 1 as an autofocus projection device has a projection lens 11 and an adjustment unit H. The projection lens 11 screens a projection object (the document 7 in the illustrated example)
Project to 14.

The adjusting section H forms an image of the projection object 7 on the screen 14.

The signal generator 12 emits a signal toward the screen 14. The signal receiving unit 13 receives the signal reflected from the screen 14 and outputs an output signal according to the distance to the screen 14.

In response to the output from the signal receiving unit 13, the adjusting unit H relatively moves the projection lens 11 and the projection 7 in a direction orthogonal to the optical axis, and moves the projection lens 11 and the projection 7 on the screen of the projection 7. It is configured to form.

When it is desired to raise the position of the projection image on the screen 14 as shown in FIG. 2, the projection lens 11 is shifted to the screen 14 side. As a result, the distortion of the projected image is corrected by relatively moving the projection lens 11 and the projection object 7.

Further, an embodiment of the present invention will be described in detail with reference to FIG. 1 and FIG.

[Overhead Projector 1] The overhead projector 1 includes a main body 2, a support 3 and a head unit 4. At a corner of the main body 2, a column 3 is provided upright. The head portion 4 is set on the support column 3 so that the head portion 4 can be adjusted vertically.

[Main Body 2] The main body 2 includes a reset button 5 and a transparent platen 6.
Is provided. An ordinary original 7 is placed on the original platen 6.
Is put on. A light source 8 and a condensing Fresnel lens 9 are provided inside the main body 2.

The light source 8 emits visible light, and preferably has a small infrared light component. If necessary, a filter may be provided to remove infrared light.

[Head Unit 4] The base unit 4a of the head unit 4 supports a projection lens 10, a reflection mirror 11, a signal generation unit 12, a signal reception unit 13, and the like.

[Adjustment Unit H] The adjustment unit H includes a projection lens 10, a reflection mirror 11, and a signal generation unit.
12, a signal receiving unit 13, an operation means 30, and the like. Base part
4a is connected to the fixed part 4c via the elastic part 4b. The base part 4a is movable in a direction orthogonal to the optical axis by the driving means 4d of the fixed part 4c. The elastic part 4b is a belly made of flexible rubber or the like.

The driving means 4d is, for example, a combination of a motor and a ball screw.

The signal generator 12 and the signal receiver 13 are located on both sides of the projection lens 10. That is, the signal generator 12, the projection lens 10
The signal receiving unit 13 is arranged so as to be parallel to the screen surface 14.

The light from the light source 8 includes a Fresnel lens 9, a document table 6, and a document 7.
, And is focused on the projection lens 10 by the Fresnel lens 9. The light including the contents of the document 7 is enlarged and projected in a conjugate relationship on the screen surface 14 by the projection lens 10 and the reflection mirror 11, so that the contents of the document 7 can be displayed on the screen surface 14. As shown by the optical axis 10a of the projection lens 10, the point P of the document 7 is projected at a projection position A on the screen surface 14 in a conjugate relationship.

In addition, as is well known, the adjustment unit enables the projection lens unit 10 to move in the optical axis direction by rotating the motor 39 in response to a signal from the signal reception unit, and correctly projects the document 7 on the screen surface.

[Signal Generating Unit 12] Referring to FIG. The signal generator 12 includes a light emitting unit 16 for emitting light and a light projecting unit 17. This light emitting means 16
Preferably emits light in an infrared or near-infrared wavelength region, and a light emitting diode (LED) or a laser diode (LD) can be employed. The light projecting means 17 is a convex light projecting lens, and projects the light of the light emitting means 16 toward the screen surface 14.

[Signal Receiving Unit 13] On the other hand, the signal receiving unit 13 includes a condensing unit 20 and a light receiving position detecting unit 21.

The light condensing means 20 condenses the light from the light projecting means 17 reflected on the screen surface 14 to the light receiving position detecting means 21. The light receiving position in the light receiving position detecting means 21 corresponds to the distance L between the screen surface 14 and the light collecting means 20.

[Light receiving position detecting means 21] Here, the light receiving position detecting means 21 will be described.

The light receiving position detecting means 21 in FIG. 4 is preferably a semiconductor position detector (Position Sensitive Detector).

[Operating Means 30] The operating means 30 of FIG. 3 will be described.

The input terminals of the amplifiers 32 and 33 are connected to the electrodes 21d and 21c of the light receiving position detecting means 21, respectively. The output terminals of the amplifiers 32 and 33 are connected to the analog switch 35. The analog switch 35 is connected to a microprocessor 37 via an A / D converter 36.

The microprocessor 37 has the reset button 5
And a motor 39 as a stepping motor and the light emitting means 16 are connected. This reset button 5 is also shown in FIG.

The motor 39 can move the projection lens 10 in the direction of its optical axis in accordance with a command from the microprocessor 37. The movement position information of the projection lens 10 is fed back to the microprocessor 37. Further, the light emitting means
16 emits light according to a command from the microprocessor 37.

[Operation] First, the power is turned on, and the reset button 5 shown in FIGS. 1 and 3 is pressed to reset the microprocessor 37.

As shown in FIGS. 1 and 2, an original 7 on which a desired content is described is placed on an original table 6. Light source 8 allows projection lens
10. The contents of the original 7 are reflected on the screen via the reflection mirror 11.
Project onto 14 The point P of the document 7 is projected on the projection center A.

At this time, the focusing is performed by moving the projection lens 10 in the optical axis direction. Please refer to FIG.

That is, based on instructions from the microprocessor 37, for projecting light through the light projecting means 17 toward the light in the near infrared or infrared region from the light emitting means 16 to a point P ₂ of the screen surface 14. The light reflected by the screen surface 14 is received by the light receiving position detecting means 21 by the light collecting means 20. Based on the position of the center of gravity of the incident spot light LP, the photocurrents I ₁ and I ₂ are output from the electrodes 21d and 21e to the amplifiers 32 and
Entered in 33.

The amplifiers 32 and 33 convert these photocurrents I ₁ and I ₂ into current −
Voltage conversion is amplified. Then, two voltage values corresponding to the photocurrents I ₁ and I ₂ are switched by the analog switch 35 and are sequentially AD-converted by the A / D converter 36.

The signal converted into a digital value in this manner is sent to the microprocessor 37 as position data of the incident spot light LP. Based on this data, the microprocessor
37 calculates and determines the amount of defocus, and instructs the motor 39 to rotate by a predetermined number of steps.

As a result, the projection lens 10 moves by a predetermined amount along the optical axis direction, and the focusing is completed.

By the way, as shown by the broken line, the position information of the projection lens 10 is fed back to the microprocessor 37 and stored in the memory. Thus, when the reset button 5 is pressed next time, the projection lens 10 is moved from that position. Also, the projection lens 10 is moved only when the reset button 5 is pressed again or the power is turned on again to perform focusing, that is, the autofocus operation is performed. When the autofocus operation is completed, the next reset operation is performed. The position state of the projection lens 10 at the time of autofocusing is maintained until the power is turned on again.

If the auto focus is always activated, the light receiving position detecting means 21 detects the presenter or the pointing rod of the projected image on the screen surface, and the auto focus is activated in an attempt to focus on the light receiving position detecting means 21 or other disturbance conditions. The focus point always moves by expanding. For this reason, the screen surface is very difficult to see. In order to eliminate this, once the focus is set, the focus is fixed until the next reset or the power is turned on again, so that a stable image surface is obtained and the screen surface is easy to see.

Next, when the projection center in FIG. 2 is shifted from A to B, the driving means 4d is driven to extend the extendable portion 4c by a predetermined shift amount R. That is, the shift amount R between the projection lens 10 and the original 7 is
That is, it has moved in the direction orthogonal to the optical axis. Accordingly, the optical axis passing through the point P of the document 7 follows the path indicated by the dotted line, and the point P moves to the projection center B and is enlarged and projected.

Even in this case, the image on the screen 14 whose projection center is B does not cause trapezoidal distortion.

4 and 5 are principle diagrams showing the relationship between the projection lens 10, the original 7, and the screen 14. FIG. However, the reflection mirror is omitted. FIG. 4 corresponds to the position of the solid line in FIG. FIG. 5 corresponds to the position of the broken line in FIG.

When the projected image on the screen 14 is moved upward as shown in FIG. 5 from the standard state shown in FIG.
Although the document 7 and the screen 14 are moved in the plane perpendicular to the optical axis 10a, the projected image does not cause trapezoidal distortion.

When the projection center shifts from A to B in this manner, the focusing of the projection lens 10 is automatically performed in the same manner as described above.

At this time, the projection lens 10, the signal generating unit 12, the signal receiving unit 13, and the like that constitute the autofocus optical system are integrally moved by a predetermined shift amount. The optical axes of the projection lens 10, the signal generator 12, and the signal receiver 13 are substantially parallel. For this reason, the distance determined by the signal generation unit 12 and the signal reception unit 13 is measured from the projection lens 10 to the screen 14 along the optical axis even when the projection lens is moved, so that correct autofocus can always be performed.

FIG. 6 shows the side of the slide projector. The signal generating unit 112 and the signal receiving unit 113 are disposed on both sides of the projection lens 110. The three units are provided on the base unit 104a. The base 104a can be shifted in a direction orthogonal to the optical axis of the projection lens 110. The base 104a moves as shown by the dotted line. The image of the film F moves from the point A on the screen 114 to the point B.

Incidentally, the present invention is not limited to the overhead projector and the slide projector. It can be applied to other types.

Although the signal is described as light in the embodiment, any signal can be applied to the present invention as long as the signal is reflected and the distance can be known like an ultrasonic wave.

Effect of the Invention As described above, even if the projection position is changed, the distortion of the projection image can be reduced, the operation accuracy of the operator increases,
Handling becomes easy.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a preferred embodiment of an autofocus projection device of the present invention, FIG. 2 is a side view of this embodiment, and FIG. 3 is a distance measurement control device for autofocus. FIG. 4 and FIG. 5 are diagrams for explaining the principle of autofocusing. FIG. 6 is a diagram showing another embodiment of the present invention. FIG.
It is a figure showing a conventional example. 1 ... Overhead projector 11 ... Reflection mirror 12 ... Signal generation unit 13 ... Signal reception unit 14 ... Screen

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) G02B 7/11

Claims (1)

(57) [Claims] 1. An auto-focus projection device for projecting an image of a projection object on a screen by a projection lens, wherein an adjustment unit for forming the image of the projection object on the screen includes: a projection lens; a signal generation unit; A signal receiving unit, and the projection lens, the signal generating unit, and the signal receiving unit are arranged so as to be movable together with respect to the projection object. A signal is transmitted along the optical axis toward the screen, and the signal receiving unit receives a signal reflected from the screen substantially along the optical axis of the projection lens and responds to a distance to the screen. Outputting an output signal, and relatively moving the projection lens and the projection object in a direction orthogonal to the optical axis of the projection lens to display the image of the projection object on the screen. On the other hand, an image of the projection object is formed on the screen in accordance with an output from the signal receiving unit, and the projection lens is relatively moved with respect to the projection object in a direction substantially perpendicular to the optical axis. When moving, together with the projection lens, by moving the signal generation unit and the signal reception unit together, the image of the projection object on the screen can be moved with little distortion, and always the optimal An autofocus projection device, wherein a focus is obtained.