JP2009086182A - Projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a projector capable of preventing continuous emission of laser beam to the same area when any abnormality occurs in a scanning part. <P>SOLUTION: The projector comprises a light source part 101 which emits laser beam, and the scanning part which scans the laser beam emitted from the light source part 101. The projector further comprises a projection window 110 disposed in a scanning range of laser beam by the scanning part to reflect a part of the laser beam and transmit the remainder; a light receiving element 111 which receives the laser beam reflected by the projection window 110; and light source output reduction means 112 and 102 which reduce the output of laser beam emitted from the light source part 101 based on the light quantity of the laser beam received by the light receiving element 111. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a laser beam scanning projector.

  In recent years, laser projectors using laser light have been proposed. Since laser light is excellent in monochromaticity and directivity, it is easy to obtain an image with good color reproducibility. As described in Non-Patent Document 1, the basic principle of a laser projector is, for example, using a scanning mirror that horizontally and vertically scans laser light from a laser light source, and the laser light is vertically directed by a vertical scanning mirror. An image is formed by a raster scan by reciprocating a plurality of times by a horizontal scanning mirror during a single scan. The gradation expression can be obtained by modulating the output intensity of laser light. As a laser beam scanning means, it is known to use a galvanometer mirror as a scanning mirror, or to scan the scanning mirror with an actuator that can be manufactured by MEMS technology.

  By the way, since the laser beam is emitted from a very small light emitting point and is a light beam having a very high degree of parallelism, it is necessary to avoid a situation in which the laser beam is directly applied to a person. In particular, in the case of a front projection type projector, there is nothing between the projector and the screen, so if a person accidentally enters the projection area while the projector is operating, the laser light is There is a risk of direct irradiation. Techniques for avoiding such a situation are proposed in Patent Documents 1 to 3.

In particular, in a rear projection type projector with a housing structure in which the projector and the screen are integrated, there is no risk that a person will accidentally enter the projection area, but if the screen is damaged or falls off the housing It is conceivable that the laser beam is directly irradiated to the viewer. A technique for preventing this is proposed in Patent Document 4.
JP 2006-178342 A JP 2005-309162 A JP 2006-227083 A JP 2007-017649 A “Ultra-Miniature Projector: A High Resolution, Battery Powered Laser Display” SID 06 DIGEST p. 2015-2017

  In the projector that displays an image by scanning the laser beam from the laser light source as described above, even if some abnormality occurs in the scanning mirror, there is a possibility that a situation that requires attention may occur. As an abnormality that may occur in the scanning mirror, for example, it is conceivable that the scanning mirror is mechanically or electrically failed. In such a case, the scanning mirror for horizontal scanning and / or vertical scanning is stopped, so that the laser light from the projector does not display a two-dimensional image, and 1 on the screen. Either continue to illuminate the point or display a horizontal or vertical straight line. When attention is paid to the location where the laser beam is irradiated, the intensity of the light irradiated per unit time is larger in this state than when the two-dimensional scanning is normally performed. Therefore, it is not preferable in terms of safety to keep irradiating the laser beam with the above abnormality occurring, and it should be avoided that such a state continues.

  In addition to the internal factors of the projector due to the failure of the scanning mirror itself, other causes of abnormalities in the scanning mirror include when some foreign object enters the projector from the outside of the projector and the foreign object collides with the scanning mirror. An external factor that the scanning mirror breaks down due to the impact of the above can also be considered. Therefore, it is preferable that the projector has a configuration that can prevent the scanning mirror from being broken due to such an external factor.

  An object of the present invention is to provide a projector that can prevent laser light from being continuously irradiated to the same region when some abnormality occurs in a scanning unit.

  A further object of the present invention is to provide a projector that can prevent foreign matter from entering the scanning unit from the outside.

  In order to achieve the above object, a projector according to the present invention is a laser beam scanning type projector having a light source unit that emits laser light and a scanning unit that scans the laser light emitted from the light source unit. An optical element that is disposed in a scanning range of the laser light by a scanning unit, reflects a part of the laser light and transmits the rest, and a light detection unit that receives the laser light reflected by the optical element; And a light source output suppressing unit that suppresses an output of the laser light emitted from the light source unit based on a light amount of the laser light received by a light detecting unit.

  ADVANTAGE OF THE INVENTION According to this invention, when a certain abnormality generate | occur | produces in a scanning part, the projector which makes it possible to prevent that the same area | region is continuously irradiated with a laser beam can be provided.

  Next, embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 is a diagram showing a schematic configuration of a projector according to the first embodiment of the present invention.

  The projector according to the present embodiment includes a light source unit 101 including three laser light sources 101R, 101G, and 101G that respectively emit red (R), blue (G), and green (B) laser beams (laser beams). And an LD control unit 102 for controlling each of the light sources 101R, 101G, and 101G. The projector further includes dichroic mirrors 103 and 104 and mirror 105 that substantially match the optical paths of the laser beams from the light sources 101R, 101G, and 101G, and vertical and horizontal scanning mirrors 106 and 107 that constitute a scanning unit that scans the laser beams. And mirror drive units 108 and 109 for driving them.

  Each of the above components is housed in the housing 113. An opening is formed in a part of the housing 113, and a projection window 110 is provided in the opening. The laser beam scanned by the scanning unit passes through the projection window 110 and is emitted to the outside of the housing 113. In the housing 113, a light receiving element 111 and a microcomputer 112, which will be described later, are further accommodated.

In the present embodiment, laser diodes (LD) are used for the laser light sources 101R, 101G, and 101G. As these laser light sources, it is preferable to use those having a characteristic of emitting a laser beam of linearly polarized light with TEM ₀₀ . In recent years, the performance of laser light sources has been remarkably improved, and those that emit high-power, that is, high-intensity laser beams are readily available. Therefore, it is preferable to use such laser light sources. Furthermore, it is preferable that the polarization directions of the laser beams emitted from the light sources 101R, 101G, and 101G coincide. Therefore, the light sources 101R, 101G, and 101G are adjusted so that the polarization directions of the emitted laser beams coincide.

  The LD control unit 102 performs drive control of the laser light sources 101R, 101G, and 101G. A laser beam whose output is modulated according to an image signal by the LD control unit 102 is emitted from the laser light sources 101R, 101G, and 101G. As will be described later, the LD control unit 102 also stops or attenuates the output of the laser light sources 101R, 101G, and 101G in accordance with a command from the microcomputer 112.

  The laser beams of the respective colors are synthesized by the dichroic mirrors 103 and 104 and the mirror 105 so that their optical paths substantially coincide. In the present embodiment, the dichroic mirror 103 has a characteristic of reflecting blue (B) light and transmitting green (G) light and red (R) light. The dichroic mirror 104 has a characteristic of reflecting green (G) light and transmitting red (R) light. Since the dichroic mirror is a well-known technique, the detailed configuration and principle thereof will not be described.

  The scanning unit includes a vertical scanning mirror 106 and a horizontal scanning mirror 107, and mirror driving units 108 and 109 for driving them. As the scanning mirrors 106 and 107, a galvano mirror or a micro mirror using MEMS technology can be used. In this embodiment, the configuration including the two scanning mirrors of the vertical scanning mirror 106 and the horizontal scanning mirror 107 has been described as an example. However, instead of these, scanning in both the vertical direction and the horizontal direction is possible. A simple micromirror may be used. In this case, since only one scanning mirror and one driving unit are provided for the scanning unit, it is possible to reduce the size of the scanning unit, and thus the projector, and the number of components.

  In the present embodiment, the projection window 110 is arranged in the scanning range of the laser light scanned in the vertical direction and the horizontal direction by the scanning unit. As the projection window 110, a wire grid type reflective polarizing plate in which fine aluminum wires are formed on a glass substrate is used as an optical element that reflects part of the laser light and transmits the rest. Such a reflective polarizing plate is commercially available and is available. The reflective polarizing plate that can be used as the projection window 110 is not limited to the wire grid type. Other types of reflective polarizing plates can be used as long as they have the characteristic of transmitting light with a polarization component whose transmission axis matches that of incident linearly polarized light and reflecting light with a component whose transmission axis does not match. It can be used as the projection window 110. The projection window (reflective polarizing plate) 110 of the present embodiment is installed in the housing 113 in a state where the transmission axis of the reflective polarizing plate is shifted by a predetermined angle with respect to the polarization direction of the laser light that is linearly polarized light. Yes.

  The light receiving element 111 as the light detecting means detects light reflected by the projection window 110 which is a reflective polarizing plate. A photodiode or the like can be used as the light receiving element 111. The microcomputer 112 has a function of transmitting the light detection result by the light receiving element 111 to the LD control unit 102.

  The casing 113 that accommodates each of the above-described structures has a sealed structure in which the projection window 110 is provided in the opening that emits the scanned laser light. For this reason, the scanning unit cannot be physically accessed from outside the housing 113. As a result, failure and breakage of the scanning unit due to entry of foreign matter from the outside are prevented.

  Next, the operation of the projector according to the present embodiment will be described.

  The LD control unit 102 is responsible for drive control of the laser light source 101 and control of intensity modulation of the laser light emitted from the laser light source 101. The LD control unit 102 controls driving and modulation of the laser light sources 101R, 101G, and 101G so as to emit laser light modulated in accordance with an image signal input from an external device (not shown). Laser light emitted from each of the laser light sources 101R, 101G, and 101G is incident on the scanning unit by the dichroic mirrors 103 and 104 and the mirror 105 with their traveling directions and optical paths being matched. In the scanning unit, the laser beam is two-dimensionally scanned by the vertical scanning mirror 106 and the horizontal scanning mirror 107 driven by the mirror driving units 108 and 109, respectively. The laser beam scanned by the scanning unit passes through the projection window 110 and is emitted from the housing 113 (laser beam 11), whereby an image is displayed on the projection screen.

  Here, as described above, the reflection type polarizing plate forming the projection window 110 is fixed to the housing 113 with its transmission axis shifted by a predetermined angle with respect to the polarization axis of the laser beam 11. A part of the beam 11 is reflected by the reflective polarizing plate. The reflection of the laser beam 11 by the reflective polarizing plate will be described with reference to FIGS. 2, 3A and 3B.

  First, as shown in FIG. 2, when the laser light incident on the reflective polarizing plate 401 is linearly polarized light 41 inclined by a predetermined angle with respect to the transmission axis of the reflective polarizing plate 401, 41 is decomposed into a component 43 that passes through the reflective polarizing plate 401 and a component 42 that reflects. Here, the predetermined angle is, as shown in FIGS. 3A and 3B, when the coordinate axis when the laser light is perpendicularly incident on the projection window 110 (laser beam 50 shown in FIG. 3A) is XYZ. The angle formed by the polarization direction of the laser beam with respect to the polarization axis of the projection window 110 on the YX plane. Referring to FIG. 3B, the predetermined angle is an angle α formed on the XY plane of the projection window 110 by the polarization direction of the laser light with respect to the polarization axis of the projection window.

  Referring to FIG. 3B, in the XZ plane, if the laser beam 11 having an intensity I is incident on the projection window 110 at an angle θ, the projection window 110 transmits the reflection-type polarizing plate by the action of the reflection-type polarizing plate. Reflected light with an intensity of I · sin α, which is a component not to be reflected, is reflected in the direction of angle θ ′. The light receiving element 111 described above is disposed on an extension line in the traveling direction of the reflected light 12 in order to receive this light. Since the incident angle and the reflection angle are equal, θ = θ ′. Further, the angle α is an angle that should be arbitrarily determined by the designer within a range of 0 to 90 degrees. Since the intensity of the reflected light 12 in the XZ plane is expressed by I · sin α as described above, the intensity of the reflected component light becomes weaker as the angle α approaches 0 degrees, and conversely as the angle α approaches 90 degrees. The light intensity of the reflection component is increased.

  With the above configuration, if the scanning unit is operating normally, the reflected light 12 is incident on the light receiving element 111, so that the light receiving element 111 detects light having an intensity within a predetermined range. That is, since the laser beam 11 is scanned by the scanning mirrors 108 and 109 (see FIG. 1), if the scanning mirrors 108 and 109 are operating normally, a part of the laser beam 11 being scanned is scanned. Light periodically enters the light receiving element 111.

  Here, the light detection amount that the light receiving element 111 will receive in a certain period in the normal state is set as a predetermined light detection amount having a certain numerical range. The reason why the predetermined light detection amount has a certain numerical range is that the intensity of the laser beam 11 varies depending on the brightness of the projected image, and therefore the light receiving element 111 receives light in a certain period according to the brightness of the projected image. This is because the detected amount of light will vary. The numerical range of the predetermined light detection amount may be fixed regardless of the image to be projected, or may be appropriately changed according to the image to be projected.

  When the scanning mirrors 108 and 109 have some abnormality and the scanning mirror is stopped at a position where the reflected light 12 does not enter the light receiving element 111, the light amount detected in a certain period is substantially zero. Therefore, the amount of light detected by the light receiving element 111 in a certain period is smaller than the predetermined amount of light detection. On the other hand, when the scanning mirror is stopped at the position where the reflected light 12 is incident on the light receiving element 111, the light receiving element 111 continues to detect light over a certain period. The light detection amount due to is larger than the predetermined light detection amount. The microcomputer 112 as the determination unit determines whether the light detection amount by the light receiving element 111 is larger or smaller than the predetermined light detection amount, and determines that the light detection amount is larger or smaller than the predetermined light detection amount, the LD control unit A signal is transmitted to 102. When receiving the signal from the microcomputer 112, the LD control unit 102 controls the laser light sources to stop driving the laser light sources 101R, 101G, and 101B or attenuate their outputs. As described above, the microcomputer 112 serving as the determination unit and the LD control unit 102 that controls the light source unit 101 constitute a light source output suppression unit that suppresses the output of the laser light emitted from the light source unit 101.

  The projector according to the present embodiment can prevent a laser beam having a certain intensity from being continuously irradiated to a certain region by the above-described operation even when some abnormality or failure occurs in the scanning unit.

  In the above description, it has been described that it is preferable to align the polarization axes of the laser beams emitted from the laser light sources 101R, 101G, and 101B of the respective colors, but this is not always necessary. For example, the light receiving element 111 also detects an abnormality in the scanning unit by shifting the polarization axis of only laser light of at least one of the three colors by a predetermined angle with respect to the polarization axis of the reflective polarizing plate that is the projection window 110. It is possible. The output characteristics according to the ratings of commercially available R, G, B, and laser light sources for each color are not always appropriate when considering the white balance of the projected image. In such a case, only for the laser light source of the color light with sufficient output, the light receiving element 111 scans by the above-described operation even if the polarization axis of the laser light is shifted from the transmission axis of the reflective polarizing plate. It is possible to detect abnormalities in the part.

(Modification)
FIG. 4 is a diagram showing a schematic configuration of a modification of the projector shown in FIG. FIG. 5A is a perspective view showing a case in the projector shown in FIG. 4, and FIG. 5B is a cross-sectional view showing the inside of the case.

  As shown in FIG. 4, in the projector according to this modification, scanning mirrors 106 and 107 and mirror driving units 108 and 109 that constitute a scanning unit, a light receiving element 111 and a microcomputer 112 are accommodated in a box-shaped case 201. These are unitized. A case 201 containing these configurations, a light source unit 101 including three laser light sources 101R, 101G, and 101B, an LD control unit 102, dichroic mirrors 103 and 104, and a mirror 105 are provided in an outer casing 204. Is housed in.

  The functions and operations of the light source unit 101, the LD control unit 102, the dichroic mirrors 103 and 104 and the mirror 105, the vertical scanning mirror 106, the horizontal scanning mirror 107, the mirror driving units 108 and 109, the light receiving element 111, and the microcomputer 112 are described. Is as described with reference to FIG. 1 and the like, and a description thereof will be omitted.

  As shown in FIGS. 4 and 5, the case 201 has an incident window 202 into which a laser beam emitted from the light source unit 101 and whose traveling direction and optical path are matched by the dichroic mirrors 103 and 104 and the mirror 105 is incident. There is provided an exit window 203 through which laser light that enters the case 201 from the entrance window 202 and is scanned by the scanning mirrors 106 and 107 exits.

  A light transmissive member is used for the entrance window 202. As the material, glass as well as plastic can be used. The surface of the entrance window 202 is preferably provided with an antireflection coating. By doing so, the optical loss when the laser light passes through the incident window 202 can be minimized. The size of the incident window 202 may be larger than the beam diameter of the laser beam.

  A wire grid type reflective polarizing plate is used for the exit window 203 as in the configuration shown in FIG. The reflective polarizing plate forming the exit window 203 is fixed to the case 201 with its transmission axis shifted from the polarization axis of the laser beam 21 by a predetermined angle, as in the projection window 110 shown in FIG. .

  The box-shaped case 201 is hermetically sealed with an opening portion through which laser light is incident and an opening portion through which the laser beam is emitted by an incident window 202 and an exit window 203, respectively. For this reason, the scanning unit cannot be physically accessed from outside the case 201. As a result, failure and breakage of the scanning unit due to entry of foreign matter from the outside are prevented.

  The exterior housing 204 has an opening 204a for projecting the laser beam 21 emitted from the emission window 203 of the case 201 onto the projection screen. In this modified example, since the scanning unit is protected by the case 201, it is not necessary to cover the opening 204a of the exterior housing 204 with a window member or the like.

  The image projecting operation by the projector of this modification is the same as that of the projector shown in FIG. Also in the projector of this modification, similarly to the projector shown in FIG. 1, the light receiving element 111 detects the amount of reflected light 22 at the exit window 203 that is a reflective polarizing plate, and based on the detected light amount. The microcomputer 112 transmits a signal to the LD control unit 102. Then, when receiving the signal from the microcomputer 112, the LD control unit 102 controls the laser light sources so as to stop driving the laser light sources 101R, 101G, and 101B or attenuate their outputs. Therefore, even if some abnormality or failure occurs in the scanning unit, it is possible to prevent the laser beam having a certain intensity from being continuously irradiated to a certain region by this operation.

  Furthermore, in this modification, since the case 201 containing the scanning unit has a sealed structure, there is no possibility that dust may enter the case 201 from the outside and affect the operation of the scanning unit. For this reason, the projector according to the present modification includes a cooling fan that takes in air from the outside into the exterior casing 204 in order to cool the light source unit 101 provided in the exterior casing 204 and circuit components that generate heat. 204 can be provided. Therefore, the light source unit 101 and circuit components can be cooled well, and the projector can be stably operated for a long time.

1 is a diagram showing a schematic configuration of a projector according to a first embodiment of the present invention. It is a figure explaining reflection of the laser beam by a reflective polarizing plate (projection window). It is a figure explaining reflection of the laser beam by a reflective polarizing plate (projection window). It is a figure explaining reflection of the laser beam by a reflective polarizing plate (projection window). It is a figure which shows schematic structure of the modification of the projector shown in FIG. 4A is a perspective view showing a case in the projector shown in FIG. 4, and FIG. 4B is a cross-sectional view showing the inside of the case.

Explanation of symbols

11, 21, 50 Laser beam 12, 22 Reflected light 41 Linearly polarized light 42, 43 Component 101 Light source 101R, 101G, 101B Laser light source 102 LD controller 103, 104 Dichroic mirror 105 Mirror 106 Vertical scanning mirror 107 Horizontal scanning mirror 108, 109 Mirror Drive Unit 110 Projection Window 113 Case 201 Case 202 Incident Window 203 Output Window 204 Exterior Case 204a Opening 401 Reflective Polarizing Plate

Claims (6)

In a laser beam scanning type projector having a light source unit that emits laser light, and a scanning unit that scans the laser light emitted from the light source unit,
An optical element that is disposed in a scanning range of the laser light by the scanning unit, reflects a part of the laser light, and transmits the rest;
A light detecting means for receiving the laser light reflected by the optical element;
A light source output suppressing unit that suppresses an output of the laser beam emitted from the light source unit based on a light amount of the laser beam received by the light detecting unit;
A projector comprising: The laser light emitted from the light source unit is linearly polarized light of three colors of red, green and blue,
The optical element is a reflective polarizing plate,
2. The projector according to claim 1, wherein a transmission axis of the reflective polarizing plate is deviated by a predetermined angle with respect to a polarization direction of at least one of the three linearly polarized light beams.   The light source unit, the scanning unit, the light detection unit, and a light source output suppression unit are housed in the housing, and the optical element is provided in an opening formed in the housing. 2. The projector according to 2. A case that houses at least the scanning unit and the light detection unit; and an exterior housing that houses the light source unit and the light source output suppression unit.
The case is formed in a portion where a light transmissive member is provided in an opening formed in a portion where the laser light incident on the scanning portion passes and the laser light emitted from the scanning portion passes. The projector according to claim 1, wherein the optical element is provided in the opened opening. The light source output suppression means is
Light quantity of the laser light said light detecting means has received it is determined whether the larger or smaller than the predetermined light detection amount in a predetermined period, the amount of the laser light which the light detecting means has received said predetermined light A determination unit that emits a signal when it is determined that the detected amount is larger or smaller than the detected amount;
A control unit that controls the light source unit to limit the output of the laser light emitted from the light source unit when the signal is received from the determination unit;
The projector according to claim 1, comprising:   The projector according to claim 5, wherein the predetermined light detection amount has a numerical range.

Images