JP2003215671A - Light projecting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light projecting device capable of restraining the occurrence of a loss light beam to be as small as possible by preventing a light beam from being made incident on a light emitting tube again, and enhancing radiation efficiency to an object by restraining the occurrence of a light beam (stray light) whose radiating direction is hardly controlled. <P>SOLUTION: The light projecting device is equipped with a cylindrical light emitting tube 1, a reflection mirror 2 reflecting light radiated from the tube 1 and provided with a light guide window 2A whose innermost part is opened in order to guide the light radiated to the rear of the tube 1, and a light guide means 3 totally reflecting the light made incident from the window 2A, returns it forward and projecting it. The total reflection surfaces 31A to 31C of the guide means 3 are provided on the outside of the mirror 2. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light projecting device mainly used for a light emitting device of an image pickup device such as a camera.

[0002]

2. Description of the Related Art For example, in a light emitting device such as a flash of a camera, a discharge tube or an arc tube (hereinafter collectively referred to as an arc tube) is used in order to efficiently project and irradiate a subject with projection light. , And a reflecting mirror that reflects the light emitted from the arc tube.

For example, as shown in FIG. 9, the reflecting mirror 101 is usually formed to have a substantially elliptical cross section, and the arc tube 10 is provided in the vicinity of one focus position of the ellipse.
2 are arranged so that the light emitted from the arc tube 102 is effectively projected and emitted forward.

[0004]

By the way, in recent years, along with the miniaturization of cameras, there is an increasing demand for miniaturization of light-emitting devices such as flashes and higher efficiency. However, in the above-mentioned conventional reflecting mirror, as shown in FIG. 10, the size of the arc tube is finite, and a part of the light emitted from the arc tube 102 to the rear (the inner part of the reflector) is reflected. A on the mirror 101
After being reflected at a point, it is incident on the arc tube 102 again at a point B, and is further transmitted through the arc tube 102 at a point C. The light that re-enters the arc tube 102 has Fresnel reflection at the previous reflection point and the incident point, so that the light amount (light intensity) is approximately half when it finally travels to the subject in front. Decays to. Further, these light rays are repeatedly refracted and reflected in the glass of the arc tube, and become light rays (stray light) whose irradiation direction is difficult to control, which is the most harmful effect in designing the light emitting section.

Further, in order to increase the luminous efficiency, as described in, for example, Japanese Patent Laid-Open No. 3-48835 and Japanese Patent Laid-Open No. 5-142629, the shape of the reflecting mirror is not an elliptical shape, but the frontage is narrow and the depth is large. By making it a deep parabolic shape,
A structure has been proposed in which the degree of freedom of light distribution characteristics is increased to suppress rays outside the angle of view. However, if the depth is increased, of the light emitted to the rear of the arc tube, as described above, the proportion of the light that is reflected by the reflecting mirror and enters the arc tube again, and is incident and transmitted there, increases. Irradiation efficiency to the front is rather reduced.

In view of the above-mentioned circumstances, therefore, the present invention prevents re-incidence to the arc tube to suppress the generation of loss light rays as much as possible, and also generates light rays (stray light) whose irradiation direction is difficult to control. It is an object of the present invention to provide a light projecting device capable of suppressing irradiation of light and increasing the efficiency of irradiation of a subject.

[0007]

According to the first invention, a cylindrical arc tube and light emitted from the arc tube are reflected,
Also, a reflecting mirror provided with a light guide window having an opening at the innermost portion for guiding the light emitted to the rear of the arc tube, and the light incident from the light guide window is totally reflected and returned to the front. A light projecting device including a light guide means for projecting light, wherein a total reflection surface of the light guide means is provided outside the reflecting mirror.

As a result, the light from the light emitting tube, which has been re-incident on the light emitting tube and wasted and wasted by the light amount and the light intensity, is attenuated by the light guiding by the total reflection in the light guiding means. It becomes possible to return to the front without doing so, and the luminous efficiency can be improved.

A second aspect of the present invention is a cylindrical arc tube,
From the light guide window, a reflecting mirror provided with a light guide window having an innermost opening for reflecting the light emitted from the arc tube and guiding the light emitted to the rear of the arc tube. A light projecting device for reflecting incident light on a surface on which a metal thin film or a dielectric multilayer film is formed and returning the light to the front to project the light, wherein the reflecting surface of the light guiding means is The feature is that it is provided outside the reflecting surface.

Thus, the light from the light emitting tube, which has been re-incident on the light emitting tube and wasted by wastingly attenuating the light quantity and the light intensity, is guided by reflection by the light guiding means.
The light can be returned to the front side without being attenuated, and the luminous efficiency can be improved.

In the first or second aspect of the invention, it is preferable that the reflecting mirror is provided with means for holding the arc tube and forming an electrode for taking in an electric current from the outside to the arc tube.

Thus, both the function of holding the arc tube and the function of the trigger electrode for power supply for applying a voltage to the arc tube can be combined, and the structure is simplified accordingly.

The third invention is a cylindrical arc tube,
A reflecting surface having a metal thin film or a dielectric multilayer film that reflects the light emitted from the arc tube is provided, and a conductive material having an innermost opening for guiding the light emitted to the rear of the arc tube. A light projecting device comprising: a light window provided with a light window, and a light guiding means for totally reflecting on a total reflection surface for guiding light different from the reflecting surface and returning the light forward and projecting light. It is characterized in that a total reflection surface for guiding light of the light guide means is provided outside the reflection surface.

As a result, the light from the light emitting tube, which has been re-incident on the light emitting tube and wasted by attenuating the light amount and the light intensity, is lost to the metal thin film or the dielectric multilayer film of the light guiding means. By guiding light by total reflection at the filmed reflecting surface, it is possible to return to the front without attenuating, and it is possible to increase the luminous efficiency.

A fourth invention is a cylindrical arc tube,
A reflecting surface having a metal thin film or a dielectric multilayer film that reflects the light emitted from the arc tube is provided, and a conductive material having an innermost opening for guiding the light emitted to the rear of the arc tube. A light guide means for providing incident light by providing a light window and reflecting the light at a light guide reflection surface provided by forming a metal thin film or a dielectric multilayer film separately from the reflection surface and returning the light forward and projecting the light. And a light guide reflection surface of the light guide means provided outside the reflection surface.

As a result, the light from the light emitting tube, which has been re-incident on the light emitting tube and wasted by attenuating the light amount and the light intensity, is lost to the metal thin film or the dielectric multilayer film of the light guiding means. By guiding light by reflection on the filmed reflecting surface, it is possible to return to the front without attenuating, and it is possible to improve the luminous efficiency.

Further, in the first to fourth inventions, the light guide means may be provided with a cylindrical lens or a toroidal lens at an emitting portion.

This makes it possible to adjust the projection direction of the light emitted backward from the arc tube when returning it to the front.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to the accompanying drawings. [First Embodiment] FIGS. 1 to 3 show a flash device to which a light projecting device according to a first embodiment of the present invention is applied. The flash device is a cylindrical arc tube 1. And a reflecting mirror 2 for reflecting the light emitted from the arc tube 1, and a light guide means 3 for guiding the light emitted to the rear of the arc tube 1 and projecting the light to the front. ing. A transparent cover 5 (see FIG. 2) that protects the arc tube 1, the reflecting mirror 2, and the like from dust and the like is provided at the opening on the front side of the flash device.

As the arc tube 1, a xenon tube (Xe) is used in this embodiment, and both end portions protruding left and right are
It is fixed by a supporting member 11 having a shape as shown in FIGS. The support member 11 is also configured to function as a trigger electrode, and in order to apply a required trigger voltage to the electrodes at both ends when the xenon tube (Xe) performs a light emitting operation. It is made of a conductive metal plate. The support member 11 is connected to a discharge circuit (not shown) by a lead wire (not shown).

The reflecting mirror 2 is formed in an elliptical shape or a parabolic shape in cross section, and there is a possibility that the light emitted from the arc tube 1 will be reflected by the reflecting mirror 2 and re-enter the arc tube 1 ( It is configured to reflect all the light except light from the arc tube 1 (toward the rear) and project the light toward the subject in the front.

As shown in FIG. 3, the reflecting mirror 2 of this embodiment has an elliptical cross section, and the arc tube 1 is provided at one focal point of the reflecting mirror 2 or in the vicinity thereof. Further, as shown in FIGS. 1 and 2, the reflecting mirror 2 is a light guide including a hole for taking in the light emitted from the light emitting tube 1 particularly toward the rear side. The window 2A is opened in a horizontally long shape over the entire inner part of the reflecting mirror 2.

The light guide window 2A of the reflecting mirror 2 is opened in the range of a specific angle θ1 from the optical axis L (see FIGS. 3 and 5) in the vertical (Z) direction, whereby the light guide means is formed. 3 is regulated, and a critical angle is exceeded in a total reflection surface 3A of the light guide means 3 described later (a total reflection condition is satisfied).
Only light from which the angle of incidence can be obtained is incident.

The light guide means 3 is for reflecting the light emitted rearward from the arc tube 1 and returning it to the front side. In this embodiment, the light guide means 3 is constituted by the light guide member 31, and is located at the back side. The rear surface, that is, the outer surface (hereinafter, referred to as total reflection surfaces 31A to 31C
It is configured so that it is totally reflected.

The light guide member 31 is made of a transparent material that attenuates as little as possible when light from the arc tube 1 is transmitted. For example, in this embodiment, the refractive index n is 1.49 and the transmittance is 92% acrylic ( PMMA) -based synthetic resin is used, and in particular, the total reflection surfaces 31A and 31B are formed in a unique curved surface shape. Further, the light guide member 31 has a certain strength because it is formed to be relatively thick, and when it is arranged on the back side of the reflecting mirror 2, it also serves as a frame for holding the reflecting mirror 2. It is supposed to work.

The total reflection surfaces 31A and 31B are formed by curved surfaces having a predetermined curvature shape, while the total reflection surface 31C is formed.
Is a plane. In addition, by any chance, the total reflection surfaces 31A to 31C, which are the rear surface (back surface) of the light guide member 31,
Considering that a part of light is incident at an incident angle equal to or less than the critical angle, an ordinary metal film such as aluminum (A
The mirror surface may be formed by depositing an L) film or a silver (Ag) film. Further, when the irradiation light from the arc tube 1 has a peculiar narrow wavelength band and is coherent (coherent) light or the like, a dielectric multilayer film for reflecting the wavelength light may be formed. Good.

The light guide member 3 which is irradiated by the arc tube 1
In order to prevent all the light passing through and advancing 1 from being transmitted to the outside and disappearing, all the light is transmitted through the front surface (front surface) 32 of the light guide member 31. Although it is formed so as to avoid the optical path, the front surface 32 may be configured to be totally reflected. In addition to acrylic (PMMA), a transparent synthetic resin such as polycarbonate (PC) or polyolefin, or a glass material such as quartz may be used as the material for forming the light guiding means 3, but the workability and the cost are low. Considering the above, the synthetic resin is preferable.

This light guide member 31 is provided with an entrance window 31D opened so as to face the light guide window 2A, and the optical path diagram shown in FIG. 5 (however, for the sake of clarity of explanation, the cylindrical lens 4 described later is (Ignored), so that all the light taken in from the entrance window 31D (irradiated rearward from the arc tube 1) is incident on the total reflection surfaces 31A to 31C of the back surface at an incident angle equal to or greater than the critical angle. Is configured.
Further, the light taken in through the incident window 31D is totally reflected by the total reflection surfaces 31A to 31C, and the light is emitted through the exit window 3D.
The light is guided to 1E, and is emitted and projected from the emission window 31E toward a subject not shown in the drawing.

In this embodiment, a xenon tube (Xe) that emits light having a spectral characteristic close to natural light is used as the arc tube 1, but when acrylic (PMMA) is used as the light guide member 31, , The critical angle of the chief ray is 42
It becomes degree. In addition, the arc tube 1 taken in through the entrance window 31D
When entering the total reflection surfaces 31A to 31C, all the light is incident at an incident angle equal to or greater than this critical angle, and the light is refracted at the total reflection surfaces 31A to 31C and transmitted from there to the outside. It is constructed so that no light escapes.

As described above, the light from the arc tube 1 causes Fresnel reflection at the entrance window 31D and the exit window 31E, as shown in FIGS. %, The luminous efficiency of irradiation light is significantly improved, as will be described later, as compared with the conventional structure in which the light guide member 31 is not used.

A cylindrical lens (cylindrical lens) 4 is provided in the exit window 31E of the light guide means 31 so that an optimum light distribution according to the irradiation pattern on the subject can be obtained. ing. It should be noted that the cylindrical lens 4 of this embodiment has a substantially convex cross-section in the short side (Z) direction and is configured to diffuse the emitted light. However, depending on the emission distribution, the cylindrical lens 4 has the same cross section. The cross section may have a concave cross section, and the emitted light may be converged. A curved toroidal lens may also be used in the longitudinal (X) direction.

Therefore, according to this embodiment, the light from the arc tube 1 has a Fresnel loss of at most 1 at the entrance window 31B and at the exit window 31C as described above.
It is about 0%. Therefore, it becomes possible to project (return) about 90% of the rest of the light emitted from the arc tube 1 toward the subject. This allows
The irradiation light amount of the light irradiated rearward from the arc tube 1 can be increased by about 30% as compared with the conventional irradiation amount of about 60%.

Further, in this embodiment, the support member 11 is used as the power supply to the arc tube 1 and the fixed support means.
Other than this, for example, the configuration shown in FIGS. 6 and 7 may be adopted. That is, as a means for supplying electric power to the arc tube 1 and a fixed support means, a support portion 2B is provided in the innermost portion of the reflecting mirror 2 while avoiding a plurality of light guide windows 2A opened, and the support portion 2B is electrically conductive to receive the arc tube 1. You may make it provide the pillow part 2C which consists of a functional metal. Then, the pillow portion 2 on the side of the arc tube 1 and the reflecting mirror 2
By directly contacting C with the discharge tube 1, the discharge tube 1 is fixed and supported at the same time as power is supplied to the arc tube 1, and the reflecting mirror 2 and a discharge circuit (not shown) are connected by a lead wire. You may do it.

[Second Embodiment] Next, the second embodiment of the present invention will be described.
The embodiment will be described with reference to FIG. In this embodiment, the same parts as those in the first embodiment are designated by the same reference numerals to avoid redundant description.

In this embodiment, the reflection surface is formed of the reflection film 6 formed on the inner surface side of the light guide member 31 of the light guide means 3. On the other hand, the outer surface side of the light guide member 31 is, as in the first embodiment, the total reflection surfaces 31A to 31C configured to cause total reflection or a reflection surface on which a reflection film is formed. Is possible.

The reflection film 6 and the reflection film are coated with a metal thin film such as an aluminum (Al) film or a silver (Ag) film which constitutes a normal reflection mirror.
When the irradiation light from the arc tube 1 is monochromatic light or coherent light, a dielectric multi-layer film that almost completely reflects the corresponding light having a specific wavelength may be deposited.

Therefore, the total reflection surfaces 31A to 3A provided on the outer surface.
1C and the surface on which the reflective film 6 provided on the inner surface is formed,
Since the light rays are reflected and returned to the front, the degree of freedom in design is increased unlike the first embodiment. Further, if the outer surface is a surface on which a reflective film is formed, it is not necessary to have a special shape that gives a critical angle, and it is optional, and the degree of freedom in design is further increased.

[0038]

As described above, according to the present invention, the light projecting device is provided with the light guide means configured to totally reflect or reflect the light emitted rearward from the arc tube and return it to the front. Since it is possible to prevent the light emitted from the arc tube from re-entering the arc tube, and to suppress the generation of loss light rays as much as possible, the light emitting tube of the light projecting device has a corresponding amount. This makes it possible to improve the luminous efficiency and further downsize the light projecting device, which is convenient for application to a flash device of a camera which is becoming smaller. Moreover, according to the present invention, since it is possible to suppress the generation of a light beam (stray light) whose irradiation direction is difficult to control, it becomes easy to design and control the irradiation pattern on the subject.

[Brief description of drawings]

FIG. 1 is a perspective view showing a configuration of a flash device according to a first embodiment to which a light projecting device of the present invention is applied.

FIG. 2 is a schematic cross-sectional view of the flash device shown in FIG.

FIG. 3 is an explanatory diagram showing a shape of a light guide member of the flash device shown in FIG.

FIG. 4 is an exploded perspective view of the flash device shown in FIG.

5 is an explanatory diagram showing an optical path of light emitted from an arc tube in the flash device shown in FIG.

FIG. 6 is a perspective view showing a reflecting mirror showing a modified example of the flash device shown in FIG. 1 and a supporting member for supporting the arc tube on the reflecting mirror.

FIG. 7 is a sectional view showing a flash device provided with the reflecting mirror of FIG.

FIG. 8 is a perspective cross-sectional view showing the configuration of a flash device according to a second embodiment to which the floodlighting device of the present invention is applied.

FIG. 9 is an explanatory diagram showing a conventional flash device.

FIG. 10 is an explanatory diagram showing a defect of a conventional flash device.

[Explanation of symbols]

1 arc tube 11 Support member (energizing means) 2 reflector 2A light guide window 2B support 2C pillow part (energization means) 3 Light guiding means 31 Light guide member 31A to 31C total reflection surface 31D entrance window 31E exit window 32 Front (front) 4 Cylindrical lens (cylindrical lens) 6 Reflective film (metal thin film; reflective surface)

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁷ Identification code FI theme code (reference) F21V 8/00 F21V 13/12 Z 13/12 G03B 15/02 L G03B 15/02 F21Y 103: 00 // F21Y 103: 00 F21V 7/12 CE

Claims (4)

[Claims] 1. A cylindrical arc tube and a light guide window having an innermost opening for reflecting the light emitted from the arc tube and guiding the light emitted to the rear of the arc tube. And a light guide means for totally reflecting the light incident from the light guide window and returning it to the front to project the light, wherein a total reflection surface of the light guide means is provided. A light projecting device provided on the outside of the reflecting mirror. 2. A cylindrical arc tube, and a light guide window having an innermost opening for reflecting light emitted from the arc tube and guiding light emitted to the rear of the arc tube. And a light guide device for reflecting the light incident from the light guide window on the surface on which the metal thin film or the dielectric multilayer film is formed and returning it to the front to project the light. A light projecting device, wherein the reflecting surface of the light guide means is provided outside the reflecting surface. 3. A cylindrical arc tube and a reflecting surface on which a metal thin film or a dielectric multilayer film that reflects the light emitted from the arc tube are formed, and the light emitted to the rear of the arc tube is provided. A light guide window in which a light guide window having an opening at the innermost portion is provided for guiding light, and the incident light is totally reflected by a total reflection surface for light guide different from the reflection surface and returned to the front to be projected. And a total reflection surface for guiding light of the light guide means outside the reflection surface. 4. A cylindrical arc tube and a reflecting surface on which a metal thin film or a dielectric multilayer film that reflects the light emitted from the arc tube are formed, and the light emitted to the rear of the arc tube is provided. A light guide window having an opening at the innermost portion for guiding light is incident, and the incident light is reflected on a light guide reflection surface formed by forming a metal thin film or a dielectric multilayer film separately from the reflection surface. And a light guide means for returning the light to the front and projecting the light, wherein the light guide reflection surface of the light guide means is provided outside the reflection surface. apparatus.