JP3762306B2 - LIGHTING DEVICE AND PHOTOGRAPHING DEVICE USING LIGHTING DEVICE - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a lighting device, particularly a lighting device suitable for an optical device having no sufficient thickness in the vertical direction, and a photographing device using the same, for example, attached to a part of a camera body (shooting body), This is suitable for shooting by irradiating illumination light (flash) efficiently on the subject side in conjunction with the shooting operation of the camera body.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, an illuminating device used for a photographing apparatus such as a camera is composed of a light source and optical components such as a reflector and a Fresnel lens that guide a light beam emitted from the light source forward.
[0003]
In such an illuminating device, various proposals have heretofore been made in order to efficiently collect a light beam emitted from a light source in various directions within a required irradiation angle of view. In particular, in recent years, instead of the Fresnel lens that has been placed in front of the light source until now, an optical member using total reflection such as a prism and a light guide is arranged, thereby improving the light collection efficiency and improving the vertical optical system. Proposals have been made to achieve both reductions in thickness.
[0004]
As a proposal of this type, as shown in Japanese Patent Application Laid-Open No. 10-115852, the applicant has made the light beam incident on the optical member from the light source into the left and right sides by total reflection surfaces formed on the upper and lower side surfaces. There is an illumination optical system using a small prism with high light collection efficiency that is condensed by a cylindrical lens or a Fresnel lens provided on the exit surface.
[0005]
[Problems to be solved by the invention]
In recent years, in a photographing apparatus such as a camera, the size of the apparatus itself has been further reduced as compared with the related art. In particular, as a recent trend, there is a strong demand to keep the vertical height of the camera low, and accordingly, there is also a demand for thinning the vertical thickness of the strobe light emitting part located at the top of the camera. strong. Against this background, there is a strong demand for practical use of a thin strobe optical system that does not deteriorate optical performance.
[0006]
In view of this, Japanese Patent Laid-Open No. 10-115852 has proposed a thin light-emitting portion in which the thickness in the vertical direction is suppressed by using a total reflection optical system that causes little reduction in efficiency even when reflected multiple times. This is because the light beam incident on the optical member from the light source is condensed by the total reflection surfaces formed on the upper and lower side surfaces in the vertical direction (the radial direction of the flash discharge tube), and the horizontal direction (flash discharge). (Longitudinal direction of the tube) constitutes a thin and efficient illumination optical system by efficiently condensing with a cylindrical lens or a Fresnel lens provided on the exit surface.
[0007]
On the other hand, problems of the strobe optical system according to the above method include the following. First, when a cylindrical lens is provided on the exit surface to collect light in the left-right direction (longitudinal direction of the flash discharge tube), the curvature is set small to increase the light collection effect. Therefore, the peripheral part can be depressed with respect to the central part, and it is difficult to bring it out as an external part as it is. For this reason, when commercializing, it is necessary to add components such as a reflector and a separate protective panel, which not only increases the cost, but also involves many components as an illumination optical system. There was a disadvantage that the efficiency was lowered. Furthermore, as an improvement plan, a lens with a Fresnel lens formed on the exit surface is also proposed. However, when a normal Fresnel lens is used, the aperture area is large, but it is difficult to use all of this aperture area effectively. Therefore, it cannot always be said that the illumination optical system has improved both the space efficiency and the efficiency of the optical system.
[0008]
From the above, the greatest problem to be solved by the present invention is to propose a thin illumination optical system that makes the most effective use of a given aperture area with the minimum necessary component configuration. It is intended to efficiently collect light flux that has not been used effectively without adding any other components, thereby increasing the light collecting performance.
[0009]
The object of the present invention is to achieve an illumination that maintains a uniform light distribution characteristic on the irradiation surface by making the thickness extremely thin as compared with the conventional illumination optical system and using the energy from the light source with high efficiency. It is an object to provide an illumination device suitable for a still camera, a video camera, and the like, and a photographing device using the illumination device.
[0010]
[Means for Solving the Problems]
In order to achieve the above object, the illumination device of the first invention according to the present application is configured as irradiation light having a predetermined irradiation angle through an optical member arranged in front of the light beam from the light source means and a reflector covering the rear. In the illumination device for irradiating, the optical member includes an incident surface facing the light source means, a reflecting surface that totally reflects a part of the light beam from the incident surface, and an exit surface that forms a Fresnel lens surface facing the incident surface. When the surface closer to the optical axis of the inner Fresnel lens of the two surfaces constituting the Fresnel lens surface is an edge surface, the angle formed by the optical axis of the edge surface of the Fresnel lens is separated from the optical axis center. The side surface shape of the optical member is a curved surface shape that guides the light beam to the edge surface of the Fresnel lens.
[0011]
In particular, the Fresnel lens surface of the optical member is formed in a direction substantially perpendicular to the longitudinal direction of the light source.
[0012]
The center of curvature of the side shape of the optical member is on the optical axis center side of the Fresnel lens, and is present on the irradiation surface side from the Fresnel lens surface.
[0013]
In addition, a reflecting surface having a shape of the reflecting umbrella substantially concentric with the center of the light source means is formed at least in part.
[0014]
By adopting the above configuration, even in an illumination optical system that is extremely thin in the vertical direction, illumination with uniform light distribution characteristics on the irradiation surface can be efficiently performed.
[0015]
In addition, since the light collection in the horizontal direction and the light collection in the vertical direction can be controlled independently with a single optical member, once the shape is determined, there is no manufacturing variation and an illumination optical system with stable optical characteristics can be configured. .
[0016]
Furthermore, since basic light control is performed by refraction and total reflection of the optical member, energy from the light source can be used efficiently, and all light control can be performed within a single optical member. Therefore, the entire illumination optical system can be configured to be extremely small and inexpensive.
[0017]
DETAILED DESCRIPTION OF THE INVENTION
(First embodiment)
Embodiments of the present invention will be described below with reference to the drawings.
[0018]
1 to 4 show an illuminating device according to a first embodiment of the present invention, particularly a flash light emitting device in this embodiment. FIG. 1 shows a flash discharge tube of a main part constituting an optical system of the flash light emitting device. 2 is a cross-sectional view taken along a plane including the central axis, FIG. 2 is a longitudinal cross-sectional view of the main part constituting the optical system of the flash light emitting device, FIG. 3 is an exploded perspective view of only the main optical system of the flash light emitting device, and FIG. It is a perspective view of the camera to which the invention is applied. In FIG. 1, a ray trace diagram of representative rays emitted from the light source is also shown.
[0019]
FIG. 1A and FIG. 1B show the optical path of only the light beam directed toward the center of the optical axis on the irradiation surface among the light beams emitted from the light source with the same cross-sectional shape. In addition to showing the region actually used in each part, it is possible to specify the optical path in which the component toward the center of the optical axis on the irradiation surface is formed.
[0020]
As shown in FIG. 4, the flash light emitting device according to the present embodiment is arranged at the upper right portion when viewed from the front of the camera body, and the exit window is thin in the vertical direction where the vertical Fresnel lens is formed.
[0021]
In the figure, 1 is a flash light emitting unit, 11 is a photographing device body, 12 is a lens barrel provided with a photographing lens, 13 is a release button, and 14 is an operation member for zooming the photographing lens. Tilt it to the tele direction, and tilt it to the back to zoom in the wide direction. 15 is an operation button for switching various modes of the camera, 16 is a liquid crystal display window for informing the user of the operation of the camera, 17 is a viewing window of a photometric device for measuring the brightness of outside light, and 18 is a viewing window of the viewfinder. It is a window. Since each function except the flash light emitting unit is a known technique, a detailed description is omitted here. In addition, the mechanical component of this invention is not limited to the above-mentioned structure.
[0022]
Next, components that define the optical characteristics of the flash light emitting unit, which is the main focus of the present invention, will be described in more detail with reference to FIGS.
[0023]
In the figure, reference numeral 2 designates a cylindrical flash discharge tube (xenon tube) that emits flash light and has a left and right longitudinal direction. Reference numeral 3 denotes a reflector that reflects in the light emission direction a component of the luminous flux emitted from the flash discharge tube 2 in the light emission direction, and a metallic material such as bright aluminum whose inner surface is formed with a high reflectance surface, or The inner surface is made of a resin material or the like having a highly reflective metal deposition surface formed thereon. Reference numeral 4 denotes an illumination light guide optical member that efficiently irradiates the subject side with the light beam directly emitted from the flash discharge tube 2 and the light beam reflected by the reflector 3 and incident. As the material of the optical member 4, an optical resin material having a high transmittance such as an acrylic resin or a glass material is suitable.
[0024]
In the above configuration, the photographing apparatus 11 is a photometric device (not shown) after the release button 13 is pressed by the user when the camera is set in the “strobe auto mode”, for example, as is conventionally known. A central processing unit (not shown) determines whether or not the flashlight emitting device emits light based on the brightness of external light measured by the device and the sensitivity of the loaded film. When the central processing unit determines that “flash light emitting device emits light” under shooting conditions, the central processing unit outputs a light emission signal and flash discharges via a trigger lead wire (not shown) attached to the reflector 3 The tube 2 is caused to emit light. The emitted light beam is emitted through the reflector 3 in the direction opposite to the irradiation optical axis, and the light beam emitted in the irradiation direction is directly incident on the optical member 4 disposed on the front surface. After being converted into a predetermined light distribution characteristic via 4, the object side is irradiated.
[0025]
In particular, the present invention is a proposal of an illuminating device in which the overall shape of the illuminating optical system of the photographing apparatus is extremely thin and the light distribution characteristics of the necessary irradiation range at that time are kept uniform. The method for setting the optimum shape will be described in more detail.
[0026]
FIG. 1 is a cross-sectional view taken along a plane including the central axis of the flash discharge tube of the main part constituting the optical system of the flash light emitting device of the first embodiment of the present invention, and optimizing the light collecting characteristic in the left-right direction. It is a figure which shows the basic idea for aiming at. 1 (a) to 1 (b) show the same cross-sectional view, and a ray tracing portion of a light beam irradiated in the center direction of the optical axis on the irradiation surface is also appended. In addition, the number of each part in a figure respond | corresponds to FIG. 2, FIG.
[0027]
As shown in FIG. 1A, the light beam emitted from the flash discharge tube 2 is incident from the incident surface 4a of the optical member 4 and then emitted from the Fresnel lens surface 4b formed on the emission surface side. At this time, due to the refractive power of the Fresnel lens, there is a light flux that travels from the region wider than the arc length, which is the substantial light emission range of the flash discharge tube, in the direction of the exit optical axis of the irradiated surface, and a light collecting effect is obtained. I understand that. However, as can be seen from the figure, when a Fresnel lens is formed to provide a condensing function, a discontinuity occurs at the edge of the Fresnel lens, and the emitted light exceeds the area of the opening of the optical system. There is a region that does not contribute to the axial direction. Further, it can be seen that this phenomenon occurs frequently in a peripheral region away from the center of the light emitting portion. In other words, by using a Fresnel lens, a significant light condensing effect can be obtained by refraction, but the aperture of the illumination optical system becomes wider than necessary, and a space-efficient optical system using the entire original aperture It turns out that it is not.
[0028]
In this embodiment, an efficient optical system is formed by effectively using an opening in a region where there is no light beam directed in the direction of the exit optical axis on the Fresnel lens surface. Another effect is to construct an optical system that derives the maximum guide number in a given aperture area.
[0029]
In order to obtain such a configuration, in this embodiment, the shape of each part of the optical member 4 is devised as shown in FIG. That is, the side surfaces 4c and 4c ′ of the optical member 4 are formed in an optimal curved surface shape, and the light is totally reflected on this surface. Further, the light beam after total reflection is guided to the edge surface of the Fresnel lens portion, and a new optical path is formed which is refracted by this edge surface and directed toward the exit optical axis direction. As a result, in addition to the light beam shown in FIG. 1A, the light beam shown in FIG. 1B is added. From almost all surfaces of the emission surface 4b of the optical member 4, the emission optical axis is obtained. There will be a light beam directed in the direction, and an optical system using the aperture area most effectively can be constructed.
[0030]
In the illustrated embodiment, the total reflection surfaces 4c and 4c ′ of the optical member 4 have a cylindrical shape of R50 (curvature radius 50 mm) in contact with the Fresnel lens exit surface. The cylindrical lens surface has a shape that gives a curvature on the paper surface of FIG. 1 but does not give a curvature in the vertical direction of the drawing. Also, regarding the inclination of the edge surface of the Fresnel lens, the angle of each surface becomes steeper as the angle of the edge surface moves away from the center of the optical axis of the Fresnel lens surface so that it is directed to the exit optical axis direction after refraction on this surface. The inclination is changed so as to be (larger). The edge surface of the Fresnel lens refers to a surface closer to the optical axis of the Fresnel lens among the two surfaces constituting the Fresnel lens.
[0031]
This is to prevent the component refracted at the edge portion of the Fresnel lens after total reflection from being biased in a certain direction on the irradiated surface. That is, the device is devised so that the continuity of the light distribution characteristics is not lost by linking the continuous change of the Fresnel lens edge portion with the curved surfaces of the total reflection surfaces 4c and 4c ′.
[0032]
In the configuration of the present embodiment, the cylindrical lens having a constant curvature (R50) in which the central axis is on the optical axis side and the irradiation surface side is present from the Fresnel lens surface as the shape of the total reflection surfaces 4c and 4c ′ of the optical member 4. Although it is a surface, it is not limited to this shape, and various shapes that can have the same effect may be adopted. For example, the total reflection surface on the side surface may be configured with a plurality of surface shapes having different inclinations. Further, the shape is not limited to the cylindrical lens surface shape, and may be various secondary curved surface shapes or three-dimensional curved surface shapes such as toric surface shapes.
[0033]
In this embodiment, the angle with the center of the optical axis is gradually increased as the edge portion of the Fresnel lens is directed toward the peripheral portion. However, as the distance from the light source center increases, This is because the refractable area on the refracting surface of the Fresnel lens gradually decreases, so that it is not necessary to raise the Fresnel edge surface more than necessary. In addition, since the region that can be easily controlled by the side total reflection portions 4c and 4c ′ of the optical member 4 is a region close to the total reflection surface, the total reflected light component is increased by laying the inclination of the Fresnel lens edge portion. This is effective when viewed as the entire optical system.
[0034]
Further, as shown in FIG. 3, the Fresnel lens surfaces are arranged side by side in a direction substantially perpendicular to the longitudinal direction of the light source.
[0035]
Next, the shape of the optical system of the flash light emitting device in the vertical direction will be described using the cross-sectional view of FIG.
[0036]
First, the cross-sectional shape of the reflector 3 is a semi-cylindrical shape (3a) that is substantially concentric with the flash discharge tube 2 in the shape behind the emission optical axis. This is a convenient shape for returning the reflected light from the reflector again to the vicinity of the center of the light source, and has the effect of making it less likely to be adversely affected by refraction or total reflection of the glass portion of the flash discharge tube. Also, with this configuration, it is easy to think because the reflected light from the reflector can be treated as a light beam that is almost equivalent to the direct light from the light source, and the overall shape of the optical system that follows can be minimized. Is good.
[0037]
On the other hand, the portions 3b and 3b ′ close to the exit surface on the front side of the light source of the reflector 3 are configured to be aspherical so that the increasing rate of the opening area increases as the exit end portion is approached. This shape is effective as a glass tube for sealing the discharge tube and a means for reducing uneven light distribution that occurs at discontinuous points in the optical system, and can collect light with uniform light distribution characteristics. .
[0038]
Next, the shape of the optical member 4 arranged on the exit surface of the reflector will be described. As shown in the drawing, between the entrance surface 4a and the exit surface 4b, the entrance surface side is a flat surface, and the exit surface side is gradually increased in inclination. 4d '. These 4d and 4d 'constitute a total reflection surface, and constitute an extremely efficient reflection optical system with little light loss due to reflection. In addition, by adopting this optical system and performing multiple reflections to gradually condense the divergent light beam, the vertical illumination angle is kept within a certain range and the vertical height is minimized. It is possible to make the configuration suppressed to a minimum.
[0039]
【The invention's effect】
As described above, by adopting the configuration of the present invention, it becomes possible to construct a thin illumination optical system that makes the most effective use of a given aperture area. It has become possible to collect well and improve the light collecting property.
[0040]
In addition, since the light collection in the left and right direction and the light collection in the vertical direction can be controlled independently with a single optical member, once the shape is determined, there is no manufacturing variation and an illumination optical system with stable optical characteristics can be configured. .
[0041]
Furthermore, since basic light control is performed by refraction and total reflection of the optical member, energy from the light source can be used efficiently, and all light control can be performed within a single optical member. Therefore, the entire illumination optical system can be configured to be extremely small and inexpensive.
[Brief description of the drawings]
FIG. 1 is a cross-sectional view of a flash light emitting device optical system according to a first embodiment of the present invention in a flash discharge tube axial direction.
FIG. 2 is a longitudinal sectional view of the flash light emitting device optical system of the first embodiment of the present invention in the flash discharge tube radial direction.
FIG. 3 is an exploded perspective view of only the main optical system of the flashlight emitting apparatus according to the first embodiment of the present invention.
FIG. 4 is a perspective view of a camera to which the flash light emitting device according to the first embodiment of the present invention is applied.
[Explanation of symbols]
4 Optical member 2 Flash discharge tube 3 Reflector umbrella 11 Camera body 12 Lens barrel 13 Release button 16 Liquid crystal display window 17 Viewing window 18 for photometry device Viewfinder viewing window

Claims (5)

In an illuminating device that irradiates a light beam from a light source means as irradiation light having a predetermined irradiation angle via an optical member arranged in front and a reflector that covers the back, the optical member has an incident surface facing the light source means, The light of the inner Fresnel lens of the two surfaces that has a reflecting surface that totally reflects a part of the light flux from the incident surface and an exit surface that forms a Fresnel lens surface facing the incident surface. When the surface closer to the axis is the edge surface, the angle formed with the optical axis of the edge surface of the Fresnel lens is increased as the distance from the optical axis center increases, and the side surface shape of the optical member is set to the edge surface of the Fresnel lens. An illumination device characterized by having a curved surface shape for guiding a light beam.   The lighting device according to claim 1, wherein the Fresnel lens surface of the optical member is formed in a direction substantially perpendicular to a longitudinal direction of the light source. 2. The illumination device according to claim 1 , wherein the center of curvature of the side surface shape of the optical member is on the optical axis center side of the Fresnel lens and is on the irradiation surface side of the Fresnel lens surface.   2. The lighting device according to claim 1, wherein the reflector has a reflecting surface formed at least partially concentrically with a center of the light source means.   An imaging device using the illumination device according to claim 1.

Images