JPH04356036A - Overhead projector and its projection light amount adjustment method - Google Patents

Abstract

PURPOSE:To evade the projection of a phenomenon image due to original mounting and replacement on a screen by rotating polarizing plates in an optical path of projection light and cutting off or passing the light. CONSTITUTION:The polarizing plates 17 and 18 are constituted in a projector head 15. The fixed polarizing plate 17 is fixed across a spacer while crossing the optical axis 112 of a lens barrel where a projection lens 16 is mounted, and the movable polarizing plate 18 is fixed to a polarizing plate ring with a stop ring. The polarizing plate ring where the polarizing plate 18 is fixed is loosely fitted in a head main body orthogonally to the optical axis 112 and rotatably. A light shield position control means is provided at the position in a rotation area wherein the planes of vibrations of the polarizing plates 17 and 18 cross each other at right angle. In this constitution, the two polarizing plates 17 and 18 are relatively rotated manually or automatically by the system in the optical path of the projection light nearby a photographic lens system to cut off or pass light beam flux which is emitted by a light source 11, passed through the surface of a document 14, and projected on a screen 111.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an overhead projector for projecting characters, figures, etc. written on a transparent document, and more particularly to an overhead projector having a function of blocking or transmitting light from projection onto a screen by the overhead projector.

0002

2. Description of the Related Art In conferences and reporting sessions, an overhead projector is often used to project original images onto a screen in order to facilitate explanations and improve the understanding of the audience.

[0003] According to Japanese Utility Model Application No. 61-132831, a light-shielding method has been proposed which makes it possible to change the placement of the original to be projected without causing discomfort to the viewers of the screen and without blinking the light source. , the idea of using a light shielding means consisting of an iris diaphragm type shutter or a swing door type shutter is disclosed.

[0004] However, mechanical shutters consisting of an iris diaphragm and a sliding door have a complicated structure, and when these shutters are used to block or pass light projected onto a screen, the image on the screen is At this point, it still remains
The problem of causing discomfort to viewers remains.

[0005]

[Purpose of the Invention] This invention has been made in view of the above, and it is possible to prevent the screen from suddenly becoming brighter or darker so that the light path of the projected light can be adjusted without causing discomfort to the viewer. An object of the present invention is to provide an overhead projector in which a polarizing plate is rotated to block light or pass light.

[0006]

DESCRIPTION OF THE INVENTION In order to achieve the above-mentioned object, this technology uses a projection lens system to convert the optical axis of the irradiated light from a light source that has passed through a transparent original on which information to be projected is written, so that it is projected onto a screen. In the overhead projector for projecting, at least a pair of polarizing plates are disposed in the entire beam flux path of the irradiated light toward the screen, and a polarizing plate rotating means is provided for rotating either one of the polarizing plates. Further, the polarizing plate rotating means is configured to include an operating means that allows an operator to rotate either one of the polarizing plates, and the polarizing plate rotating means is configured to include: an original film detection means for detecting the presence or absence of an original film on the original table; a polarizing plate rotation drive means for rotationally driving one of the polarizing plates; and a response to the detection output of the original film detection means. and drive signal sending means for sending a drive signal to the rotational drive means, and drive signal sending command means that allows an operator to instruct the drive signal sending means to send a drive signal. In addition, in an overhead projector that converts the optical axis of irradiated light from a light source that has passed through a transparent original on which information to be projected is written and projects it onto a screen, the total rays of light directed toward the screen are At least one pair of polarizing plates are disposed in the bundle path, and one of the polarizing plates is rotated to adjust the amount of light projected onto the screen. In an overhead projector that converts the optical axis of transmitted light emitted from a light source by a projection lens system and projects it onto a screen, at least one pair of polarizing plates is disposed in the total beam path toward the screen, and
Rotating either one of the polarizing plates to block the amount of light projected onto the screen; further, in the light blocking method,
The structure includes a light-shielding position regulating means for regulating the light-shielding position.

As a result of having the above configuration, in the present invention,
An operator manually rotates one of a pair of polarizing plates disposed in a beam path through which irradiated light heads toward a screen. The device also detects the presence or absence of film on the document on the document table, and in response to the detection output, drives the drive signal sending means, and the drive signal sent from the drive signal sending means causes the motor rotation driving means to polarize. Rotates the motor that rotates the plate.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be explained in detail below based on preferred embodiments shown in the accompanying drawings. FIG. 1 shows the main configuration of an overhead projector to which first and second embodiments of the present invention are applied. The code 10 is the light source 11 or the light source 11
13 is the main body 1 of the overhead projector, which has a built-in condensing mirror 12 for concentrating the luminous flux upward.
14 is a transparent document in which information to be projected is placed on the mounting surface of the mounting table 13; 15 is a projection lens 1 constituting a projection lens system;
6, etc., 17 is a fixed polarizing plate that is irradiated from the light source 11, passes through the transparent original 14, and transmits only the light component belonging to the vibration plane unique to this polarizing plate toward the projection lens 16; 18 is a movable The polarizing plate 19 is a rotating rod (polarizing plate rotating means) that rotates the movable polarizing plate 18 , and these polarizing plates 17 and 18 are configured in the projector head 15 .

The projector head 15 is attached to a pillar 10a that stands up from the main body 10, and moves up and down along this pillar to adjust the state of the projected image of the transparent original 14 onto the screen 111.

The fixed polarizing plate 17 and the movable polarizing plate 18 have a light shielding function according to the present invention.
FIG. 2 shows the configuration of a first embodiment of the projector head 15 of No. 8. In FIG. 2, the same components as those shown in FIG. 1 are given the same numbers. The fixed polarizing plate 17 is connected to the optical axis 112 of the lens barrel 15C on which the projection lens 16 is mounted.
, and is fixed via a spacer 22. The projection lens 16 is fixed with a retaining ring 23. Movable polarizing plate 1
8 is fixed to the polarizing plate ring 20 with a retaining ring 21. The polarizing plate ring 20 to which the polarizing plate 18 is fixed is loosely fitted into the head main body 15A perpendicular to the optical axis 112 and is rotatable. In this rotating state, the rotating rod 19 is inserted and fixed to the side surface of the polarizing plate ring 20 through a rotating groove 15B cut into the side surface of the head main body 15A. The rotation groove 15B limits the rotation range of the rotation rod 19 in a direction perpendicular to the optical axis 112 to 90°. A light shielding position regulating means is provided at a position in a rotation range where the vibration planes of the polarizing plates 17 and 18 are perpendicular to each other. The head body 15A and the lens barrel 15C constitute a part of the projector body 15.

With this configuration, the operation of the first embodiment of the present invention will be explained using FIGS. 1 to 3.

The fixed polarizing plate 17 shown in FIG. 2 allows only light components having vibrations belonging to the vibration plane unique to this polarizing plate to pass toward the projection lens 16. Similarly, the movable polarized light 18 also allows the projected light having a component vibration unique to this polarizing plate to pass through. The positional relationship between the fixed polarizing plate 17 and the movable polarizing plate 18 is as shown in FIGS. 1 and 2, and as shown in FIG. When they are in a parallel state, all of the vibrational light that has passed through the vibration plane of the movable polarizing plate 18 passes through the fixed polarizing plate 17 and is transmitted through the projection lens system to the transparent original 14 shown in FIG. The information written in is projected onto the screen 111 and made available to the viewers.

[0013] The operator of the overhead projector,
When it is desired to replace the transparent original 14, the operation lever 19 is moved in FIGS. 1 and 2 while the light source 11 of the projector is turned on.
The optical axis 112 rotates from the position along the rotation groove 15B shown in FIG. 2 with the optical axis 112 as the rotation center. In this rotation process, the vibration plane of the movable polarizing plate 18 continuously changes the intersection angle between the vibration planes of the fixed polarizing plate 17 from 0°, which is a parallel state, to 90°, which is an orthogonal state. (stepless) change. During this change process, the polarizing plate 1
8 is continuously and gradually attenuated by the polarizing plate 17, and is regulated by the 90° rotating end of the rotating groove 15B, so that the intersection angle of the vibration planes of both polarizing plates is as shown in FIG. 3(B). When the orthogonal state shown in FIG.
1, the projection light does not reach the point. In this state, the operator replaces the transparent original 14 with a desired original. After replacement, when the operating rod 19 is rotated in the opposite direction, the change in the intersection angle of the vibration planes of both polarizing plates causes the projected light of the screen 111 to gradually increase in brightness through a process reverse to that described above. From the state shown in FIG. 3(B) to the state shown in FIG. 3(A), the projection state of the screen becomes a state where it can be viewed by a viewer.

The rotation position and rotation range of the operating rod 19 may be set as appropriate depending on the relationship between the projector and the operator.

Next, a second embodiment of the present invention is shown in FIG. 4(A).
, shown in (B). The same components as in the first embodiment are given the same reference numerals.

In FIGS. 4A and 4B, click grooves 34A, 34B, 34C, 34D, and 34E are formed on the outer periphery of the polarizing plate ring 20 that fits into the head body 15A. In this embodiment, five click grooves are formed by dividing the 90° range in which the polarizing plate ring 20 rotates into four equal parts. The dividing method may be set as appropriate other than this. A click hole 30 corresponding to each click groove is formed in the head body 15A, a click ball 33 and a click spring 32 are inserted into the click hole 30, a click pressure adjustment screw 31 is set, and the click groove, 34A, 34B, 3
Apply click pressure to 4C, 34D, and 34E.

In such a configuration, when the operating rod 19 is rotated, in addition to continuously (steplessly) changing the mutual intersection angle of each vibration plane of the fixed polarizing plate 17 and the movable polarizing plate 18, The clicked rotation position can be changed intermittently (stepwise). The operator can attenuate the light emitted onto the screen 111 (Fig. 1) by a constant amount each time, and by selecting the desired click position, the viewer can adjust the degree of attenuation that changes each time the original is replaced. You will be freed from watching the meeting.

In this embodiment, the polarizing plate 17 is fixed and the polarizing plate 18 is movable, but the polarizing plate 18 may be fixed and the polarizing plate 17 is movable.

FIG. 5 is a main configuration diagram of an overhead projector to which a third embodiment of the present invention is applied. Note that the same components as in the first embodiment are denoted by the same reference numerals, and explanations of duplicate configurations and operations will be omitted.

Reference numeral 51 denotes an inverted L-shaped sensor support that is erected at a suitable position on the upper surface of the mounting table 13 and supports the film sensor 52. The film sensor 52 is fixed to the lower surface of the projecting portion 51a of the sensor support 51.
It is arranged in a beam path that passes through the transparent original 14 and heads toward the photographing lens 16 . For example, a photoelectric conversion element (light receiving element) is used as the film sensor 52, and is configured to output a predetermined electric signal when receiving light from a light source.

Reference numeral 53 denotes a polarizing plate ring 55 disposed within the projector head 15 and fixedly supporting the movable polarizing plate 18.
A polarizing plate rotating motor 54 is fixedly supported by the rotating shaft 53a of the polarizing plate rotating motor 53, and meshes with a gear portion on the outer periphery of the polarizing plate ring 55. This is a transmission gear that transmits the driving force from the polarizing plate rotation motor 53. Reference numeral 56 denotes a light-shielding tape attached to one edge of the transparent original 14 at a position facing the film sensor 52.

Next, a specific configuration of a third embodiment of the projector head 15 including polarizing plates 17 and 18 is shown in FIG. In FIG. 6, the same components as those shown in FIGS. 2 and 5 are given the same reference numerals.

The polarizing plate ring 55, which fixedly supports the movable polarizing plate 18, has a gear formed on its outer periphery, and is loosely fitted into the support cavity in the head body 15A in a state perpendicular to the optical axis 112. It can be rotated around the center. A polarizing plate rotation motor 53 having a transmission gear 54 fixed to a rotation shaft 53a is fixed to the head main body 15A. These components that cooperate with each other to rotate the polarizing plate constitute a polarizing plate rotating means.

FIG. 7 shows the configuration of a control circuit for rotating the movable polarizing plate 18. Components corresponding to those shown in FIGS. 5 and 6 are given the same reference numerals.

Comparators 70 and 71 receive a detection signal sent from the film sensor 52 and compare the signal with a reference level (V) held in a reference level setter (memory or the like) 72. The reference level is set to a predetermined level between the high level and low level of the outputs 73 and 74 of the comparators 70 and 71, respectively, based on the outputs of the film sensors. Comparators 70, 71 and reference level setter 72 constitute a level detector 710. 75 and 76 are the respective outputs 77 of the comparators 70 and 71;
This is an OR gate that takes in 78 to the input terminal. A level detector 710 and OR gates 75 and 76 constitute the main part of the control circuit. Reference numeral 711 denotes an input device at the input end of these OR gates for allowing the operator to command the rotation direction of the polarizing plate rotation motor 53, and this is constituted by, for example, an input key. Reference numeral 79 denotes a motor drive unit that rotates the polarizing plate rotating motor in accordance with the outputs of the OR gates 75 and 76. SIP in FIG. 7 is a sensor signal input port, KIP1,
KIP2 indicates a key input port, and DOP1 and DOP2 indicate drive output ports, respectively.

With this configuration, the operation of the third embodiment of the present invention will be explained using FIGS. 5 to 7.

When the light source 11 is turned on when the transparent original 14 is not set on the mounting table 13 shown in FIG. Ru. The film sensor 52 sends a low level output to the sensor signal input port SIP shown in FIG. Low level outputs from the sensor signal input ports are input to comparators 70 and 71. The comparator 70 outputs a high level signal when this low level output is lower than the reference level preset by the reference level setter 72. The output of the other comparator 71 becomes low level. This high level signal passes through the OR gate 75 and the motor drive section 79.
reach. The motor drive unit 79 receiving this signal causes
The polarizing plate rotation motor 53 is rotated, and this rotational force is transmitted to the polarizing plate ring 55 via the gear 54, and the polarizing plate ring 55 rotates together with the movable polarizing plate 18 about the optical axis 112. .

In this rotation process, the vibration plane of the rotating polarizing plate 18 continuously (none) changes the intersection angle of the natural vibration planes to orthogonal to each other in relation to the vibration plane of the fixed polarizing plate 17. stage). During this change process, the projected light that has passed through the polarizing plate 18 is continuously and gradually attenuated by the polarizing plate 17, and the intersection angle of the vibration planes of both polarizing plates is as shown in FIG. 3(B).
When the orthogonal state shown in FIG. 1 is reached, all of the projected light that has passed through the polarizing plate 18 is blocked by the polarizing plate 17, and no projection light reaches the screen 111 shown in FIG.

In this state, when the operator places a desired original on the loading platform as shown in FIG.
The light shielding tape 56 affixed to the light source 11 blocks the light beam from the light source 11 toward the film sensor. The shielded film sensor 52 sends a high level output to the sensor signal input port SIP shown in FIG. The comparator 71 receiving this high level output outputs a high level signal because this high level output is higher than the reference level. The output of the other comparator 70 becomes low level. The comparators 70 and 71 enter the output state when the film original 14 is placed on the loading table 13 as shown in FIG. This high level signal is O shown in Figure 7.
It passes through the R gate 76 and reaches the motor drive section 79. The polarizing plate rotation motor 53 is rotated in the opposite direction to the above-mentioned direction by the motor drive unit 79, and the polarizing plate ring 55 is rotated by the movable polarizing plate 1.
8, it is rotated in the opposite direction to that described above. Since the intersection angle of the vibration planes of both polarizing plates changes through a process opposite to the above case, the projected light of the screen 111 is gradually intensified, and as shown in FIG.
From the state shown in B) to the state shown in FIG. 3A, the projection state of the screen becomes available for viewing by viewers. When the operator replaces the original with another desired original while keeping the light source 11 on, the film original 1 is placed on the mounting table 13 so that the film sensor 52 can receive the light from the light source.
If the position of 4 is shifted, the film sensor receives the projected light. The movable polarizing plate 18 is rotated as described above, and the projected light is gradually reduced and blocked. In this state, the operator removes the transparent original 14 and replaces it with a desired original. After replacement, the projection light is gradually increased and the display is ready for viewing.

In this embodiment, the polarizing plate 17 is fixed and the polarizing plate 18 is movable, but the polarizing plate 18 may be fixed and the polarizing plate 17 is movable. Further, the polarizing plates 17 and 18 may be provided near the projection lens and on the beam path after the optical axis is converted by the mirror shown in FIG. 1 or 5.

[0031] Also, from the key 711 to the key input port K
Rotation control of the polarizing plate can also be performed by inputting high level and low level paired signals to IP1 and KIP2.

[0032]

[Effects of the Invention] As described above, the overbed projector according to the present invention has a simpler structure when installed in the vicinity of the projection lens system, compared to the case where an iris diaphragm and a sliding door type mechanical shutter light shielding means are used. Yes, the following benefits can be obtained.

That is, it is not necessary to blink the light source every time the transparent document to be projected is replaced. Since the transparent document surface is always bright, positioning on the mounting table is easy. When replacing the transparent original surface, the light is either not emitted at all or is emitted to the desired darkness, so that unnecessary images of the original, such as the top and bottom, reverse, tilt, hand, etc., are not projected onto the screen or are projected in the desired darkness. Since the image is projected in the darkness of the sky, the viewer's discomfort is eliminated.

[Brief explanation of the drawing]

FIG. 1 is a conceptual diagram of an overhead projector showing an embodiment of the present invention.

FIG. 2 is a diagram showing a first embodiment of the head section of the overhead projector of the embodiment shown in FIG. 1;

FIGS. 3(a) and 3(b) are diagrams showing the crossing state of each vibration plane of two polarizing plates.

4A and 4B are diagrams showing a second embodiment of the head section of the overhead projector of the embodiment shown in FIG. 1; FIG.

FIG. 5 is a conceptual diagram of an overhead projector showing a third embodiment of the invention.

6 is a diagram showing a head section of the overhead projector of the embodiment shown in FIG. 5. FIG.

7 is a diagram showing the configuration of a control circuit of the overhead projector of the embodiment shown in FIG. 5. FIG.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 10... Main body, 11... Light source, 12... Condensing mirror, 13... Mounting table, 14... Transparent original, 15... Projector head, 1
5A...head body, 15B...rotation groove, 15C...lens barrel, 1
6... Projection lens, 17... Fixed polarizing plate, 18... Movable polarizing plate, 19... Operating rod, 110... Mirror, 111... Screen, 112... Optical axis, 20, 55... Polarizing plate ring, 2
1, 23... Retaining ring, 22... Spacer, 30... Click hole, 31... Click pressure adjustment screw, 32... Click spring, 33... Click ball, 34A, 34B, 34C, 3
4D, 34E...Click groove, 51...Sensor support, 5
2...Film sensor, 53...Polarizing plate rotation motor, 5
4... Gear, 56... Light shielding tape, 70, 71... Comparator, 7
2... Reference level, 75, 76... OR gate, 79... Motor drive section, 710... Level detector, 711... Input device,
SIP...Sensor signal input port, DOP1, DOP
2...Drive output port, KIP1, KIP2...Key input port.

Claims (7)

[Claims] 1. An overhead projector in which irradiated light emitted from a light source and transmitted through a transparent original on which information to be projected is written is converted to an optical axis by a projection lens system and projected onto a screen, in which the irradiated light is directed toward the screen. 1. An overhead projector comprising: at least a pair of polarizing plates disposed in all light beam paths; and a polarizing plate rotating means for rotating one of the polarizing plates. 2. The overhead projector according to claim 1, wherein the polarizing plate rotating means is a rotating rod for manually operating one of the polarizing plates. 3. The polarizing plate rotating means rotates either one of the original film detecting means for detecting the presence or absence of a film fixed on the original placed on the original table, and the polarizing plate. 2. The polarizing plate rotation driving means for driving the polarizing plate, and a drive signal sending means for sending a driving signal to the rotation driving means in response to the detection output of the original film detection means. 2 overhead projectors. 4. The overhead projector according to claim 3, further comprising drive signal sending command means that allows an operator to instruct the sending of a drive signal to said drive signal sending means. 5. In an overpet projector in which irradiated light from a light source that has passed through a transparent original on which information to be projected is written is converted into an optical axis by a projection lens system and projected onto a screen, all light rays directed toward the screen are A method for adjusting the amount of projected light for an overhead projector, comprising disposing at least a pair of polarizing plates in a beam path and rotating one of the polarizing plates to adjust the amount of light projected onto a screen. 6. In an overhead projector in which light emitted from a light source passes through a transparent original on which information to be projected is written, the optical axis is converted by a projection lens system, and the light is projected onto a screen. 1. A method for adjusting the amount of projected light of an overhead projector, characterized in that at least one pair of polarizing plates is disposed in the path, and one of the polarizing plates is rotated to block the amount of light projected onto a screen. 7. The projection light amount adjustment method for an overhead projector according to claim 6, wherein the light blocking method includes a light blocking position regulating means for regulating a light blocking position.