JP2013083868A - Light irradiation device and camera - Google Patents

Abstract

Provided is a light irradiation apparatus which prevents thermal damage of a transmission optical system with an inexpensive configuration.
The light source includes a light source, a reflector that reflects light from the light source, and a transmission optical system provided in front of the light source and the reflector. In the light irradiation apparatus that irradiates the reflected light of 32 to the outside through the transmission optical system 33, the portion where the light is most concentrated among the places where the transmission optical system 33 is arranged passes through the substantial part of the transmission optical system 33. Without passing through the gap 33a.
[Selection] Figure 1

Description

  The present invention relates to a light irradiation apparatus and a camera for irradiating light to the outside.

  For example, a flash device for a camera directly irradiates part of light emitted from a flash discharge tube directly with the reflector and irradiates the light to the outside through a transmission optical system. In particular, in the flash device described in Patent Document 1, in order to prevent damage to the transmission optical system due to heat, a heat-resistant coating is applied to the transmission optical system or a transmission optical system having high heat resistance is used.

JP 2001-5063 A

  However, the use of the above heat-resistant coating or a high heat-resistant transmission optical system brings about an increase in cost.

  The present invention includes a light source, a reflective umbrella that reflects light from the light source, and a transmission optical system provided in front of the light source and the reflective umbrella, and transmits direct light from the light source and reflected light of the reflective umbrella. Applied to a light irradiation device that irradiates to the outside through an optical system, and the portion where the light is most concentrated among the arrangement positions of the transmission optical system is configured so that the light passes through the gap portion without passing through the substantial portion of the transmission optical system. It is characterized by that.

  ADVANTAGE OF THE INVENTION According to this invention, the light irradiation apparatus which prevented the thermal damage of the transmission optical system with the cheap structure can be provided.

1 is a schematic side sectional view of an external flash device for a camera according to an embodiment of the present invention. II-II sectional view taken on the line of FIG. FIG. 2 is a detailed view of the Fresnel lens in FIG. 1. The figure which looked at the Fresnel lens from the front.

An embodiment in which the present invention is applied to an external flash device for a camera will be described with reference to the drawings.
1 and 2, the flash device includes a main body 1, a mounting portion 2 for mounting on a camera, and a light emitting portion 3 that can rotate with respect to the main body 1. The light emitting unit 3 includes a flash discharge tube (for example, a xenon tube) 31, a reflector 32 disposed so as to cover the discharge tube 31, and a Fresnel lens 33 disposed in front of the discharge tube 31 and the reflector 32. The main capacitor 34 that stores electric charges for flash light emission, the housing 35 that houses these members 31 to 34, and the protector lens 36 that covers the irradiation port of the housing 35.

  The reflector 32 is generally formed by bending a single reflector, and its inner surface (reflective surface) is a quadratic approximate curved surface extending in the extending direction of the discharge tube 31. When the flash discharge tube 31 is flashed, about 1/3 of the emitted light is directly reflected, and the remaining 2/3 is reflected by the reflector 32 toward the front, a Fresnel lens 33 acting as a convex lens, and The light passes through the protector lens 36 in order and is irradiated to the outside to contribute to the illumination of the subject. The protector lens 36 may have lens characteristics or may be a flat panel.

  By the way, the Fresnel lens 33 is made of an acrylic resin (for example, PMMA) and has a relatively low heat resistance. Easy to receive. In particular, the center portion of the Fresnel lens 33 in the vertical direction, that is, the vicinity of the optical axis of the irradiation light is closest to the discharge tube 31, and the light incident on the Fresnel lens 33 is most concentrated on the center portion due to the characteristics of the reflector 32. Therefore, if the discharge tube 31 is caused to emit light continuously at a short time interval, the central portion of the Fresnel lens 33 may be damaged (for example, melted) by heat. The effect of heat can be reduced if the Fresnel lens 33 is separated from the discharge tube 31 and the reflector 32, but there are problems such as an increase in the size of the flash device and the inability to obtain desired light distribution characteristics.

  Also, in the external flash device, in order to prevent thermal damage of the Fresnel lens 33, all operations are automatically prohibited when there is a risk of heating, a high temperature warning is given with an icon or buzzer, Measures such as setting a limit on the number of flashes are taken. If the operation is prohibited by this, a warning is issued, or the number of continuous flashes exceeds the limit, the flash device must be naturally cooled for a while, and flash photography cannot be performed during that time.

  Accordingly, in the present embodiment, as shown in FIGS. 1 to 4, a through hole 33 a is provided in the central portion in the vertical direction of the Fresnel lens 33, and most of the light concentrated in the central portion passes through the through hole 33 a ( It was configured to be guided to the protector lens 36 side (without passing through the lens body). Thereby, the damage by the heat | fever of the Fresnel lens 33 can be suppressed, and the opportunity and time of the natural cooling mentioned above can be reduced.

  As can be seen from FIGS. 2 and 3, the through-hole 33 a is a slit-like hole extending in the extending direction of the discharge tube 31, and its length is substantially equal to the light emission range W (FIG. 2) of the discharge tube 31. Equivalent. Further, the height of the through hole 33 a is substantially equal to the diameter of the discharge tube 31.

  The presence or location of thermal damage of the Fresnel lens 33 depends on the shape and size of the discharge tube 31, the light emission intensity, the heat resistance of the Fresnel lens 33, and where the light is concentrated (the characteristics of the reflector 32). Depends on). For this reason, it is desirable to obtain an optimum value for the position, shape, and size of the through-hole 33a of the Fresnel lens 33 by experiment or the like for each model. When light concentrates at two or more locations, it may be possible to provide through holes 33a at two or more locations. Of course, it is necessary to consider the influence on the optical performance by providing the through-hole 33a.

  Here, since light passing near the center (optical axis) of the Fresnel lens 33 is hardly refracted from the beginning, the deterioration of the optical performance (light distribution characteristic) due to the provision of the through hole 33a at the center is so small that it can be ignored. . Further, since the protector lens 36 is fitted in front of the Fresnel lens 33 so as to substantially seal the internal space of the housing 35, even if the Fresnel lens 33 is provided with a through hole 33a, the inside of the housing 35 is externally provided. Dust, moisture, etc. do not enter the battery. Furthermore, the protector lens 36 also serves to prevent the hand from touching the Fresnel lens 33 that has become hot.

  Although the protector lens 36 is also made of acrylic resin such as PMMA, it is separated from the discharge tube 31 and the reflector 32 and the Fresnel lens 33 is provided between them, so that it is hardly affected by heat.

  As described above, in the present embodiment, the through-hole 33a is provided in the Fresnel lens 33 so as to reduce the thermal damage. Therefore, the Fresnel lens 33 is provided with a heat resistant coating, or a Fresnel lens having high heat resistance is used. There is no need to reduce the cost.

  The transmission optical system in which the through hole is provided is not limited to the Fresnel lens. Moreover, it may replace with a through-hole and may be a notch. Furthermore, instead of providing a through-hole or a notch in the transmission optical system, the upper and lower two transmission optical systems may be arranged with a gap between them, and the gap may play the same role as the through-hole. Good. In short, the portion where the light is most concentrated in the arrangement position of the transmission optical system may be configured such that the light passes through the gap portion without passing through the substantial portion of the transmission optical system.

  In the above description, the external flash device has been described. However, the present invention can also be applied to a flash device built in a camera and a camera incorporating the flash device. Further, the present invention can be similarly applied to various light irradiation devices other than the flash device. As an example, there is a projector device that has a light source such as an LED, a reflector, and a transmissive or reflective liquid crystal element and projects a light image formed by the liquid crystal element to the outside. If this type of projector apparatus has a transmission optical system in front of the light source and the reflector, the present invention is applicable.

  Moreover, the light (flashlight) which uses LED etc. as a light source may be sufficient. In the case of a flashlight, the light source light and the reflected light from the reflector are concentrated at all angles at the central portion of the transmission optical system, and therefore, for example, a circular through hole may be provided at the central portion. Moreover, in an illuminating device in which a plurality of LEDs as light sources are arranged in a predetermined direction, a slit hole extending in the arrangement direction may be provided in the transmission optical system. Thus, the shape of the gap provided in the transmission optical system must be determined by the shape and arrangement of the light source and the light distribution characteristics of the reflector.

3 Light Emitting Unit 31 Flash Discharge Tube 32 Reflector Umbrella 33 Fresnel Lens 33a Through Hole 34 Main Capacitor 35 Case 36 Protector Lens

Claims (7)

A light source;
A reflector that reflects light from the light source;
A transmission optical system provided in front of the light source and the reflector,
In the light irradiation device that irradiates the direct light from the light source and the reflected light of the reflector to the outside through the transmission optical system,
The light irradiating apparatus characterized in that a portion where the light is most concentrated among the arrangement positions of the transmission optical system is configured such that the light passes through the gap portion without passing through the substantial portion of the transmission optical system.   The light irradiation apparatus according to claim 1, wherein the gap is shaped according to a shape and arrangement of the light source or a light distribution characteristic of the reflector.   3. The light irradiation according to claim 2, wherein the light source is a discharge tube extending in a predetermined direction, and the gap is formed in a slit shape extending in an extending direction of the discharge tube. apparatus.   The light irradiation apparatus according to any one of claims 1 to 3, wherein a portion where the light is most concentrated among the arrangement positions of the transmission optical system is a portion including an optical axis of irradiation light.   5. The light irradiation apparatus according to claim 1, wherein a through-hole is provided as the gap in a portion corresponding to a portion where the light is most concentrated in the transmission optical system.   The housing according to any one of claims 1 to 5, further comprising a housing that houses the light source, the reflector, and the transmission optical system, wherein the light irradiation port of the housing is covered with a transparent member. The light irradiation apparatus of description.   A camera comprising the light irradiation device according to claim 1 as a subject illumination device.

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