JPH01209435A - Projecting device using reflecting mirror - Google Patents

Abstract

PURPOSE:To accurately and easily perform focusing by projecting a projected image through a reflecting mirror, receiving and reflecting the signal of a signal generating part with the aid of this reflecting mirror, and transmitting it to a signal receiving part, even if the projecting angle of the reflecting mirror is changed. CONSTITUTION:The signal generating part 12 outputs a signal towards a screen 14 through the reflecting mirror 11. The signal receiving part 13 receives the signal reflected from the screen 14 through the reflecting mirror 11 and outputs an outputting signal in accordance with a distance to the receiving screen 14. The projecting device 1 is so constituted that an adjusting part A forms the image of a projected object 7 on the screen 14 corresponding to an output from the signal receiving part 12. Thus, an accurate and easy focusing can be possible, even if the elevation angle of the reflecting mirror 11 is changed.

Description

[Detailed description of the invention] − of The present invention relates to a projection device using a reflecting mirror.

As is well known, a projection device using an anti-tA mirror, the so-called A-backed projector (Ol-IP), places an original on a document table, passes light through the original, and transmits the light to a projection lens. The image is passed through a mirror, reflected by a mirror, and projected onto a screen. Further, in conventional OHPs, what is called an autofocus type is one in which initial focusing is manually set and only subsequent magnification changing operations are followed automatically. This allows the contents of the document to be enlarged and displayed on the screen.

Conventionally, with autofocus OHPs, you have no choice but to focus manually at the beginning, and if the distance to the screen changes, you have to manually focus everything. be.

There are also cases where it is desired to shift the projected image on the screen upward. In this case, the projected image is shifted by changing the elevation angle of the mirror provided at the top of the O)-IP. However, 0[''
The method of directly projecting light horizontally from P toward the screen and measuring the distance by receiving the reflected light has the following problems.

The measured distance value is always constant. However, the distance between the screen and the reflecting mirror increases or decreases by changing the elevation angle of the reflecting mirror.

In other words, a distance measurement error inevitably occurs depending on the magnitude of the elevation angle.

This invention was made in order to solve the above-mentioned problems, and uses a reflecting mirror that can be accurately and easily focused even if the elevation angle of the mirror is changed, and that is easy to handle at the projection site. The purpose of this project is to provide a projection device that is

11 causes LL The invention is summarized in the claims.

To do the lesson - Please refer to FIG.

An overhead projector 1 as a projection device includes a projection section S and an adjustment section A.

The projection section S projects the projection object 6 onto the screen 14 via the reflecting mirror 11. The adjustment section A is configured to adjust the projection object 6
This is to form an image on the screen 14.

The position of the image on the screen 14 can be moved by moving the reflecting mirror 11.

This projection device 1 using a reflecting mirror 11 includes a signal generating section 12
and a signal receiving section 13. The signal generator 12 is a reflector 1
1 to the screen 14.

The signal receiving section 13 receives the screen 1 via the reflecting mirror 11.
The screen 1 receives the signal reflected from the screen 4.
Outputs an output signal according to the distance up to 4.

The projection device 1 is configured such that the adjusting section A forms an image of the projection object 6 on the screen 14 in response to the output from the signal receiving section 12 .

The m-" target projection image is projected through the reflecting mirror 11. Signal generator 12
The signal is also sent to the screen 14 via the reflecting mirror 11.

The signal receiving section 13 receives the signal via the reflecting mirror 11.

Support 11 Please refer to FIG.

[Overhead Projector 1] An overhead projector 1 as an example of a projection device includes a main body 2, a support 3, and a head portion 4. Main body 2
A pillar 3 is provided vertically at the corner. This support column 3 has a head portion 4, and is set to be adjustable in elevation in the vertical direction.

[2 wood bodies] The main body 2 is provided with a reset button 5 and a transparent document table 6. A normal original 7 as a projection object is placed on the original table 6. Further, inside the main body 2, as shown in FIG. 2, a light source 8 and a condensing Fresnel lens 9 are provided.

This light source 8 emits visible light, and preferably has a small amount of infrared light component. In addition, if necessary, a filter can be installed to remove infrared light.

[Projection Section S] The light source 8, Fresnel lens 9, and document table 6 constitute a projection section S. This projection section S projects the original 7 onto a screen 14 via a projection lens 10, which will be described later.

[Head section 4] The head section 4 includes the projection lens 10. Reflector 11. Signal generator 12. It includes a signal receiving section 13 and an adjusting section A.

The signal generating section 12 and the signal receiving section 13 are located on both sides of the projection lens 10 on the base 4a.

As can be clearly seen in Figures 1 and 2, the signal generator 1
2. The signal receiving section 13 and the projection lens 10 are along the diagonal direction of the document table 6.

By doing this, the distance measuring base Fit length B can be maximized while reducing the size of the base 4a. If these three members were arranged in a direction parallel to the surface of the reflecting mirror 11, the outer dimensions of the base 4a would become too large.

For this reason, an increase in the size of the head portion 4 is unavoidable.

The light from the light source 8 passes through the Fresnel lens 9, the document table 6, and the document 7, and is focused onto the projection lens 10 by the Fresnel lens 9. The light containing the contents of the original document 7 is enlarged and projected onto the screen surface 14 by the projection lens 1o and the reflecting mirror 11 in a conjugate relationship. In other words, the original (contents of 47,
can be displayed.

See Figure 3.

The optical axis 10a of this projection lens 10 is located at a height hl from the mounting portion 15 of the main body 2. Point P'+ of the original 7 is projected onto the screen cotton 14 as a point P2 in a conjugate relationship.

The optical axis Q1 of the light projecting means 17 of the signal generating section 12, the optical axis Q2 of the signal receiving section 13, and the optical axis 10a of the projection lens 10 are arranged to converge at a nearby point P2 on the screen surface 14.

[Signal Generator 12] Refer to FIG. 4. The signal generating section 12 has a light emitting means 16 and a light projecting means 17 for emitting light. The light emitting means 16 is preferably capable of emitting light in the infrared or near infrared wavelength region, and can be a light emitting diode (LED) or a laser diode. The light projecting means 17 is a convex light projecting lens, and the light from the light emitting means 16 is directed to the screen surface 14.
It is designed to project light towards.

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

The light condensing means 20 directs the light from the light projecting means 17 to the screen surface 1.
4 is focused on the light receiving position detection means 21. The light receiving position in the light receiving position detecting means 21 corresponds to the distance IL between the screen surface 14 and the light collecting means 2o.

[Adjustment section A for autofocus] Please refer to FIG.

Adjustment unit A for focusing is a projection lens 10° motor 39
, gears 39a, 39b, and one operating means 30. Gear 39b of motor 39 meshes with gear A739a. The gear 39a meshes with a gear r39c of the projection lens 10.

[Light-receiving position detecting means 21] Here, the light-receiving position detecting means 21 will be explained with reference to FIG.

The light receiving position detection means 21 is preferably a semiconductor device detector (P'position S sensitive D).
). This light receiving position detection means 21
is composed of a P-type resistance layer 21a, an N+ type resistance layer 21b, and one layer 210 of a high-resistance Si substrate.

When an incident spot light LP from the screen surface enters a position X (resistance Rx) from the electrical center CL as shown by an arrow, this light is photoelectrically converted and becomes a photocurrent 1o. This photocurrent 1o is applied to two electrodes 21d and 21 of the resistance layer 21a.
It is divided and output from e as 1+ and I2.

Please refer to FIGS. 5 and 6.

The distance between the electrodes 21d and 21e is C9, and the resistance is RC, the distance from the electrical center CL of the light receiving position detection means 21 to the center of gravity of the incident spot light LP is X, and the resistance is RX. The photocurrent generated by the incident spot light LP is
Then, the photocurrents I+ and Iz obtained from the electrodes 21d' and 21e can be found from the following equations.

1o =1+ +12...(1)1
+ -Io (Rc/2-RX)/Rc...(2
) I2-Io (Rc/2+Rx)/Rc...
(3) Since the resistance distribution of the P-type paper layer is uniform, the resistance RX is proportional to the length X, and the resistance Rc is proportional to the distance C.

Therefore, equations (2) and (3) can be rewritten as shown below.

1 + -1o (C/ 2- X ) / C-(
4) I2=Io (C/2+x)/C=・(5) Here, by taking the ratio of I+ and 12, it is possible to detect the position of the incident spot light LP regardless of the amount of incident light. can. In other words, 12 C/2+x △=□=□ ... (6) 1+C/2-x For reference, the position resolution is determined by determining how far the length on the light receiving surface of the light receiving position detection means 21 is resolved for detection. The degree of position resolution is defined as the minimum detectable displacement of a light spot on the light receiving surface of the light receiving position detecting means 21. Therefore, the relationship between the two is as follows.

Position resolution -C/Position resolution These values are determined by the signal-to-noise ratio of the light receiving position detection means 21. Assuming that the center of gravity of the incident spot light changes by ΔX on the light receiving position detection means 21 with the interval C, the resulting displacement ΔI of the signal current is expressed by the following equation.

Δl−2io ・Δx/C・−・−・−＜7＞This△
ΔX when I becomes equal to the noise current in of the light receiving position detection means 21 becomes the minimum resolution ΔR.

△R-C-In/2Io =・18) Figures 4 and 6
See diagram.

The luminous flux of the light emitting means 16 is adjusted by the projection lens 17 to a state closest to a parallel luminous flux.

Here, the subject distance (screen surface 14 and light projecting means 17
The distance M) from the distance measurement base line length is B, the focal length of the light receiving lens is f, and the electrode spacing is C9, the electrical center position (PSD output current 1+).

Letting X be the distance from the spot light position (where I2 becomes equal) to the gravity center position of the focused incident spot light, the following equation is obtained.

X=B-f/L (9
) By substituting equation (9) into equation (6), the following equation 17 is obtained.

12 C/ 2 +X A=-=□ I + C/ 2- X C/2+B-f/L C-L+2B-fC/2-B-
f/L C-L-2B-f...(10) Rewriting equation (10), A+1 28-f L-□ ・□...(11) A-10 Become.

That is, by calculating the ratio of the signal current values taken out from the light receiving position detection means 21, the distance to the screen surface 14, which is the subject, can be determined from equation (11).

Furthermore, as is clear from equation (10), the ratio of the signal current values is approximately proportional to the reciprocal of the subject distance (L).

Note that 29 in FIG. 6 is a filter.

In Figure 6, as the subject distance increases, the distance
becomes smaller, and as L becomes smaller, X becomes larger.

[Operation means 301 Next, the operating means 30 shown in FIG. 4 will be explained.

The input terminals of the amplifiers 32 and 33 are connected to the light receiving position detection means 21.
are connected to electrodes 21d and 21c, respectively. The output terminal of amplifier 32 is connected to analog switch 35.

Analog switch 35 is connected to microprocessor 37 via A/D converter 36.

The microprocessor 37 is connected to the reset button 5, a motor 39 such as a step motor, and the light emitting means 16.

This reset button 5 is also shown in FIG. The motor 39 is capable of moving the projection lens 10 in the direction of its front axis according to commands from the microprocessor 37. This 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.

[Production vJ] First, turn on the power, press the reset button 5 shown in FIGS. 1 and 4, and reset the microprocessor 37.

As shown in FIG. 1, a manuscript 7 with desired contents written thereon is placed on a manuscript table 6. The light source 8 causes the projection lens 10. The contents of the original 7 are projected onto the screen surface 14 via the reflecting mirror 11.

At this time, the projection lens 10 is moved in the optical axis direction to perform initial autofocus. Please refer to FIG. That is, according to a command from the microprocessor 37, light in the near-infrared or infrared region is projected from the light emitting means 16 toward a point P2 on the screen surface 14 via the light projecting means 17. Screen surface 1
This light reflected at 4 is received by the light receiving position detecting means 21 by the condensing means 20. Based on the center of gravity of the incident spot light LP, a photocurrent It is generated from the electrodes 21d and 21e.

I2 is input to amplifiers 32.33.

These photocurrents 11, I2 by amplifiers 32 and 33 are
Current-to-voltage conversion is amplified. Then, the analog switch 35 switches the two voltage values corresponding to the photocurrents 1+ and 12, and the A/D converter 36 sequentially converts them to 0.

The signal thus converted into a digital value is sent to the microprocessor 37 as position data of the incident spot light LP. Based on this data, the microprocessor 37 calculates the amount of out-of-focus by using a predetermined formula, 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 autofocus 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. Thereby, the next time the reset button 5 is pressed, the projection lens 10 is moved from that position. In addition, the projection lens 10 is moved and focused only when the reset button 5 is pressed again or when the power is turned on again, that is, an autofocus operation is performed, and when the autofocus operation is completed, the next reset operation is performed. The position of the projection lens 10 during autofocus is maintained until the power is turned on again.

If autofocus is always activated, the light receiving position detection means 21 may detect the person explaining the projected image on the screen or the pointing stick, and the autofocus may operate to try to focus there, or other disturbance conditions may occur. The focus point constantly moves. This makes the screen very difficult to see. In order to eliminate this problem, after focusing by -degree, the focus is fixed until the next reset or power is turned on again, thereby obtaining a stable image surface and making the screen surface easier to see.

By performing a series of operations in this way, autofocus can be performed both initially and when setting the magnification, making handling at that time extremely easy.

Further, as described above, the reason why the wavelength region of the light from the signal generating section 12 is preferably near infrared or infrared is as follows. In other words, when the visible light signal generator 12 is used, a spot of visible light is visible on the screen surface 14, which overlaps with the document content on the screen surface 14, making it difficult to see. Furthermore, the spot overlaps with the projection light having a large amount of light, making it difficult for the light receiving position detecting means 21 to detect the spot hidden by the projection light. As a result, detection performance is significantly degraded.

During operation, the elevation angle of the reflector 11 in FIG. 3 may be changed from the solid line state to the broken line state. By doing this, the position of the image on the screen 14 is raised. Even if the state is changed in this way, the optical axis 1 of the projection lens 10
Since the optical axis Q+ of the 0a1 signal generating section 12 and the optical axis Q2 of the signal receiving section 13 are substantially parallel, there is almost no deviation in the angle of the optical axes of the three, so distance measurement accuracy can be maintained. . In other words, there is no change in autofocus accuracy.

Further, referring to FIGS. 1 and 3, the projection lens 10
The reason why the optical axis 10a, the optical axis 9i of the signal generating section 17, and the optical axis Q2 of the condensing means 20 are made to be close to each other on the screen surface 14 is as follows.

The screen surface 14 is not always perpendicular to the optical axis 10a of the projection lens 10. For this reason, each optical axis 10a as described above.

If Q+ and Q2 are not close to each other, there will be a difference in the optical path length of each optical axis, resulting in a large distance measurement error.

As shown in FIGS. 1 and 2, when the signal generating section 12 and the signal receiving section 13 are arranged near the projection lens 10 with the projection lens 10 interposed therebetween, the distance measurement base line length B can be made long. If the distance measurement basic length B shown in FIG. 6 can be made longer, the amount of change in the position X in the light receiving position detection means 21 relative to the amount of change in the distance 1111tL to the screen 14 becomes larger. In other words, the distance is 11 at the longer portion of the light receiving position detection means 21! tL
This means that the date of change can be detected. This makes it possible to improve distance measurement accuracy. Moreover, since both the signal generating section 12 and the signal receiving section 13 are located near the projection lens, the head can be made compact.

In the embodiments, the signal is described as light, but any signal that is reflected and distance can be determined, such as an ultrasonic wave, can be applied to the present invention.

1 vomit 11 As explained above, the projected image is projected through a reflecting mirror,
The signal from the signal generator is received by this reflecting mirror, reflected, and sent to the signal receiver.

In other words, even if the projection angle of the reflecting mirror is changed to move the projected image up or down, focusing can be done accurately and easily with almost no distance measurement error. Therefore, it is easy to handle at the projection site, and the operator can concentrate on explaining the projected image.

[Brief explanation of the drawing]

FIG. 1 is a perspective view showing an overhead projector according to an embodiment of the present invention, FIG. 2 is a plan view of the overhead projector, FIG. 3 is a side view of the overhead projector and the screen surface, and FIG. 4 is a projection lens operating means, FIG. 5 is a cross-sectional view showing an example of the light receiving position detecting means, and FIG. 6 is a diagram showing the signal generating section, signal receiving section, and screen surface. 1... Overhead projector 2...
......Body 4...Head section 5...Reset button 6...Light source 7... ...Original 10...Projection lens 10a+Q+,Qz-optical axis 11...Reflector 12...Signal generator 13...Signal reception Section 21...Light receiving position detection means 30...Operation means S...Projection section A...Adjustment department representative Patent attorney 1) Toru Hebe Figure 1 Figure 2 Figure 3 Figure 5 Figure 6

Claims (1)

[Claims] A projection object (7) is projected onto a screen (
14), and an adjustment section (A) that forms an image of the projection object (7) on the screen (14), and adjusts the position of the image on the screen (14). In a projection device using a reflecting mirror (11) configured to be movable by moving the reflecting mirror (11), a signal generating section (12) that emits a signal toward the screen (14) via the reflecting mirror (11) is provided. ), and a signal receiving section (13) that receives a signal reflected from the screen (14) via a reflecting mirror (11) and outputs an output signal according to the distance to the screen (14). , wherein the adjusting section (A) is configured to form an image of the projection object (7) on the screen (14) in accordance with the output from the signal receiving section (13). A projection device using a mirror.