JP2010191031A - Imaging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an imaging apparatus having a flash light-emitting part that emits luminous flux from a light source efficiently with uniform light distribution. <P>SOLUTION: A camera includes a flash light-emitting part 6 having a total reflective surface 14f emitting luminous flux emitted at a large angle from the vicinity of an emitting optical axis, out of the luminous flux from an Xe tube 12, to an irradiation direction. In the camera, the Xe tube 12 and an emitting surface 14e of an optical prism 14 are arranged to be tilted to a plane orthogonal to the optical axis O of a photographic optical system, and also the Xe tube 12 is arranged nearly parallel with the tilt angle α of the emitting surface 14e, and is arranged such that an emitting optical axis center 12b of the Xe tube 12 is deviated from an emitting optical axis center 14p of the emitting surface 14e. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an imaging apparatus having a flash light emitting unit.

  Patent Document 1 discloses a flash light emitting unit that forms a light distribution by providing a Fresnel lens on the front surface of a light emitting discharge tube and inclining the central axis of the light emitting discharge tube and the incident surface and the exit surface of the Fresnel lens to an angle that corrects. Disclosure. Patent Document 2 discloses a flash light emitting unit having an optical prism having an incident surface on which a light beam emitted at a larger angle than the vicinity of the exit optical axis is incident and a total reflection surface that totally reflects the light beam from the incident surface.

JP 2006-91364 A JP 2000-250102 A

  However, the configuration of Patent Document 1 has a problem in that it is difficult to obtain a sufficient amount of flash light due to a reduction in efficiency due to the reflectance and refraction of the reflector, and the configuration of Patent Document 2 has a problem of uneven light distribution.

  Therefore, an object of the present invention is to provide an imaging apparatus having a flash light emitting unit that efficiently emits a light beam from a light source with a uniform light distribution.

  An imaging apparatus according to one aspect of the present invention totally reflects a photographing optical system for photographing a subject, a light emitting unit, an incident surface on which light from the light emitting unit is incident, and part of the light incident on the incident surface. An optical prism having a total reflection surface and an exit surface, the exit surface of the optical prism and the central axis of the light emitting means are parallel, and the exit optical axis center of the exit surface of the optical prism and the light emission The center of the exit optical axis of the means is non-parallel to the optical axis of the imaging optical system, and the distance from the plane orthogonal to the optical axis of the imaging optical system to the exit surface of the optical prism is that of the imaging optical system The light emitting means and the light emitting means are arranged so that the center of the exit optical axis of the exit surface of the optical prism is closer to the optical axis of the photographing optical system than the center of the exit optical axis of the flash tube as the distance from the optical axis increases. With optical prism Characterized by location.

  The present invention can provide an imaging apparatus having a flash light emitting section that efficiently emits a light beam from a light source with a uniform light distribution.

It is a fragmentary sectional view of the flash light emission part vicinity of the digital camera of a present Example. It is a perspective view of the digital camera shown in FIG. 3A is a partial cross-sectional view in the vicinity of the flash light emitting portion of the digital camera shown in FIG. 1, and FIG. 3B is a partial plan view. It is a disassembled perspective view of the flash light emission part shown in FIG. It is BB sectional drawing of the flash light emission part shown in FIG.3 (b). It is sectional drawing corresponding to FIG. 1 of the flash light emission part of a comparative example. FIG. 7 is a ray diagram of the comparative example shown in FIG. 6. It is a light ray diagram of the present Example shown in FIG. FIG. 9A is an optical path diagram in a cross section corresponding to FIG. 1 of the flash light emitting portion of the comparative example, and FIG. 9B is an optical path diagram of FIG. FIG. 10A is a light distribution characteristic diagram corresponding to FIG. 9A, and FIG. 10B is a light distribution characteristic diagram corresponding to FIG. 9B. It is sectional drawing for demonstrating the setting of the prism shape of the optical prism shown in FIG.

  FIG. 1 is a cross-sectional view of the flash light emitting part of this embodiment. FIG. 2 is a front perspective view of the digital camera (imaging device, electronic device) of the present embodiment having the flash light emitting section shown in FIG.

  In FIG. 2, the digital camera includes a camera housing 1, a lens barrel 2 that houses a photographing optical system for photographing a subject, a power button 3, a release button 4, a mode lever 5 that changes a photographing mode, and a flash light emitting unit 6. . The lens barrel 2 is large enough to enable high-power zoom, and when the camera casing 1 is thinned, its exterior surface is configured by an inclined surface 1b connecting the lens barrel 2 and the camera outer peripheral edge 1a. become.

  FIG. 3A is a top view of the periphery of the flash light emitting unit 6, and FIG. 3B is a front view thereof. FIG. 4 is an exploded perspective view of the flash light emitting unit 6. The flash light emitting unit 6 includes a flexible circuit board 7, a main capacitor 8, a base 10, a reflector 11, an Xe tube 12 (light emitting means), an optical prism 14, a cover 16, and a plate 17.

  An electric element is mounted on a flexible circuit board (hereinafter abbreviated as “FPC”) 7 and functions as a flashing board. The FPC 7 has two holes 7a, two holes 7b for positioning, and an open land 7c. Two terminals 8a of the main capacitor 8 are inserted into the two holes 7a and soldered. The two bosses 10a of the base 10 are inserted into the two holes 7b, and the FPC 7 is fixed to the receiving surface 10b of the base 10 with a double-sided tape or an adhesive (not shown). Such fixing is the same for the FPC 7 on the main capacitor 8. Further, the FPC 7 further includes a plurality of lands (not shown), and a lead wire 9a, a lead wire 9b, and a lead wire 9c with a connector are soldered thereto.

  The main capacitor 8 is connected to the FPC 7, precharges power necessary for flash emission, and supplies power to the Xe tube 12 via the FPC 7 during light emission.

  The base 10 functions as a holding member or a frame.

  The upper part of the base 10 holds the reflector 11, the Xe tube 12, and the optical prism 14 and engages with the cover 16. The upper portion has a predetermined thickness and has a rectangular or track-shaped base portion as viewed from above and an upright portion that stands vertically from the upper surface of the base portion. A pair of claws 10e is formed on the side surface of the base. The standing portion forms a recess 10c and has a rib 10d. The recess 10c has a rectangular parallelepiped shape that houses a reflective umbrella rubber 15 described later. The rib 10 d is inserted into the hole 16 a of the cover 16 and positioned, and the pair of claws 10 e engage with the pair of holes 16 b of the cover 16.

  The trunk | drum of the base 10 has a structure which bent the flat plate member at right angle. One flat surface portion is a receiving surface 10b that faces and receives the FPC 7, and a pair of bosses 10a protrude from the receiving surface 10b. The pair of bosses 10a are inserted into the pair of holes 7b of the FPC 7, whereby the FPC 7 is positioned on the receiving surface 10b. The other plane portion is orthogonal to the receiving surface 10b, and is fixed to the plate 17 so as to face the plate 17, and further has a pair of bosses 10f and screw holes 10g. The pair of bosses 10f are inserted and positioned in the pair of holes 17a of the plate 17, and screws are fixed to the holes 10g through the holes 17b of the plate 17.

  The reflector 11 is a semi-cylindrical reflecting member that reflects the component of the light beam emitted from the Xe tube 12 that is a light source toward the rear side in the irradiation optical axis direction and the vertical direction. The inner surface of the reflector 11 is made of a metal material such as bright aluminum, or is made of a resin material in which a metal having a high reflectance is deposited on the inner surface. The reflectance of the reflector 11 is about 80 to 90%.

  When the reflective umbrella rubber 15 is inserted into the recess 10 c of the base 10, an appropriate clearance is maintained between the reflective umbrella rubber 15 and the back surface (not shown) of the reflective umbrella 11. A flexible terminal portion having an opening land 7c of the FPC 7 is inserted into this clearance. The reflective umbrella rubber 15 is made of an elastic member such as silicon rubber, and is charged moderately so that the opening land 7c is brought into contact with the back surface of the reflective umbrella 11 by an elastic force. By charging, a trigger voltage can be applied from the opening land 7 c to the nesa coat portion on the surface of the Xe tube 12 through the reflector 11.

  The Xe tube (light source) 12 is a light emitting discharge tube (xenon tube) having a cylindrical straight tube shape disposed in a semi-cylindrical recess of the reflector 11. Both end portions of the Xe tube 12 are inserted into through holes formed in the hollow cylindrical Xe rubber 13. The Xe rubber 13 is brought into contact with both ends of the optical prism 14 to hold the Xe tube 12. The Xe rubber 13 is composed of an elastic member such as silicon rubber. The electrodes 12a of the Xe tube 12 are soldered to the opposite end portions of the lead wires 9a and 9b on the FPC 7, respectively.

  The optical prism 14 is an optical member that is disposed in front of the emitting portion of the reflector 11 and is formed of a transparent body. The optical prism 14 is made of an optical organic polymer material having high transmittance such as polymethyl methacrylate (PMMA). The optical prism 14 is held by being engaged with a groove (not shown) of the base 10 by ribs 14a provided at both ends.

  The cover 16 is formed of a member that covers the upper side of the flash light emitting unit 6 and does not transmit the flash light. The plate 17 connects the base 10 to a main chassis (not shown) that holds a main board (not shown) on which electrical elements for processing the lens barrel 2 and the image, system, and power supply of the digital camera are mounted. However, the base 10 may have the function of the plate 17.

  FIG. 5 is a cross-sectional view taken along the line BB of FIG. 3B, and the reflector 11 is divided into a total of three regions, one region 11b on the rear side and two regions 11c on the front side from the light source center. Of the light beams emitted from the Xe tube 12, the light beams emitted backward and vertically in the emission optical axis direction are reflected by the regions 11 b and 11 c of the reflector 11. The optical prism 14 includes a first incident surface 14c for entering a light beam emitted from the vicinity of the exit optical axis out of the light flux from the Xe tube 12, and a pair for entering a part of the light beam emitted at a larger angle than the vicinity of the exit optical axis. A second incident surface 14d. The optical prism 14 further includes a pair of total reflection surfaces 14f that totally reflects a part of the light incident on the second incident surface 14d. The optical prism 14 has an exit surface 14e that emits the light beam from the first incident surface 14c and the light beam from the total reflection surface 14f. Thus, since the optical prism 14 has the total reflection surface 14f, a sufficient amount of light can be secured.

  6 is a cross-sectional view corresponding to the AA cross-sectional view of FIG. 3B when the Xe tube 102 is disposed without considering the inclination angle β of the exit surface 101e of the optical prism 101. FIG. In the figure, a line connecting the average heights of the exit surfaces 101e of the optical prism 101 is inclined by β degrees with respect to a plane P orthogonal to the optical axis O (photographing optical axis) of the photographing optical system of the camera. The tube 102 faces the subject and is disposed perpendicular to the camera optical axis direction. As a result, the distance between the exit surface 101e and the Xe tube 102 changes according to the position in the camera horizontal direction by the inclination angle β of the exit surface 101e. Thus, although the surface of the exit surface 101e is uneven, here, the average height is regarded as the effective exit surface 101e. Further, when there are a plurality of inclination angles of the effective exit surface 101e and the plane P orthogonal to the photographing optical axis O, the maximum inclination angle may be set to the inclination angle β. This also applies to the inclination angle α and the exit surface 14e shown in FIG.

  FIG. 7A is a cross-sectional view corresponding to the CC cross-sectional view of FIG. 3B in the case of FIG. 6, and also shows the emitted flash light. FIG. 7B is a cross-sectional view corresponding to the BB cross-sectional view of FIG. 3B in the case of FIG. 6, and also shows the emitted flash light. FIG. 7C is a cross-sectional view corresponding to the DD cross-sectional view of FIG. 3B in the case of FIG. 6, and also shows the emitted flash light.

  As shown in FIGS. 7A to 7C, the lengths 101hb, 101hc, and 101hd of the total reflection surface 101f vary depending on the position in the horizontal direction. Further, spread angles 101jb, 101jc, and 101jd at which the light beam reflected by the total reflection surface 101f is emitted from the emission surface 101e are changed. As a result, a portion where light rays are concentrated (for example, 101t) or a portion where the number of light beams is small (for example, 101u) occurs, and a striped light and dark portion occurs in the captured image.

  FIG. 1 is a cross-sectional view taken along line AA of FIG. 3B in the flash light emitting unit 6 of the present embodiment. FIG. 1 is a cross-sectional view in a plane including the optical axis O of the imaging optical system and the central axis C of the flash tube. In this embodiment, the central axis of the Xe tube 12 is arranged substantially parallel to the exit surface 14e of the optical prism 14 having the inclination angle α. In FIG. 1, a line connecting the average heights of the exit surfaces 14e of the optical prism 14 is inclined by α degrees with respect to a plane P orthogonal to the camera optical axis O, and the Xe tube 12 is inclined with respect to the subject. . Further, as the exit surface 14 e of the optical prism 14 moves away from the optical axis O in the X direction, it moves away from the surface P orthogonal to the optical axis O. However, since the center plane C of the exit surface 14e and the Xe tube 12 is substantially parallel, the distance between the exit surface 14e and the Xe tube 12 is substantially constant regardless of the position in the X direction.

  FIG. 8A is a cross-sectional view taken along the line CC of FIG. 3B and also shows the emitted flash light. FIG. 8B is a cross-sectional view taken along the line BB in FIG. 3B and also shows the emitted flash light. FIG.8 (c) is DD sectional drawing of FIG.3 (b), and also shows the flashlight emitted. As shown in FIGS. 8A to 8C, the lengths 14hb, 14hc, and 14hd of the total reflection surface 14f according to the horizontal position are substantially equal. In addition, since the emitted light beams 14jb, 14jc, and 14jd are not significantly changed in angle or density, even if the exit surface 14e is inclined, no difference in brightness or unevenness in light distribution occurs.

  However, in this state, light distribution is insufficient due to the fact that the entire light emitting unit is inclined by α degrees with respect to the plane P orthogonal to the optical axis O. In the present embodiment, in order to correct this, as shown in FIG. 1, the exit optical axis center 14p of the exit surface 14e is corrected by the distance Ax with respect to the exit optical axis center 12b of the Xe tube 12. Offset to the light-deficient side. In this embodiment, the exit optical axis center 14p of the exit surface 14e is offset from the exit optical axis center 12b of the Xe tube 12 by a distance Ax in a direction approaching the optical axis O. By doing so, it is possible to compensate for the shortage of light distribution on the side approaching the optical axis O.

  As shown in FIG. 1, the exit optical axis center 14p of the exit surface 14e of the optical prism 14 and the exit optical axis center 12b of the Xe tube 12 are parallel and non-parallel to the optical axis O, respectively.

    In the flash light emitting unit 6, due to the inclination, the distance from the plane P perpendicular to the optical axis O to the exit surface is small on the lens barrel side (14ma) and large on the camera outer peripheral side (14mb). Therefore, the emission optical axis center 14p is inclined to the side opposite to the lens barrel 2, and the light distribution on the lens barrel 2 side tends to be insufficient. Therefore, in the present embodiment, as shown in FIG. 1, the exit optical axis center 14p of the exit surface 14e of the optical prism 14 is set to the lens barrel 2 side (light beam) without changing the exit optical axis center 12b of the Xe tube 12. It is offset by a distance Ax on the side close to the axis O).

    FIG. 9A shows a light distribution before offsetting the exit optical axis center 14p of the exit surface 14e with respect to the exit optical axis center 12b of the Xe tube 12 in FIG. FIG. 9B shows the light distribution after the exit optical axis center 14p of the exit surface 14e is offset from the exit optical axis center 12b of the Xe tube 12 in FIG. The Xe tube 12 has a straight tube shape, and the entire inner periphery of the glass emits light. However, in FIG. 9A and FIG. 9B, only the light from the point light source at the center of the Xe tube 12 is displayed for convenience.

    In FIG. 9A, the number of light beams 14qa on the lens barrel side with respect to the exit optical axis center 14p is smaller than the number of light beams 14ra on the outer peripheral side (see, for example, the region 14s). Get dark. On the other hand, in FIG. 9 (b), the light beam 14qb on the lens barrel side and the light beam 14rb on the outer peripheral side with respect to the emission optical axis center 14p have substantially the same number and density of light beams, and the light beam distribution is uniform. The brightness of the captured image is approximately equal on the left and right.

    FIG. 10A is a light distribution characteristic diagram corresponding to FIG. 9A, and FIG. 10A is a light distribution characteristic diagram corresponding to FIG. 9A. The outer light distribution curve 18 indicates the light distribution characteristic in the left-right direction, the inner light distribution curve 19 indicates the light distribution characteristic in the vertical direction, and the light distribution characteristic indicates the amount of light for each angle. The light distribution curve 18 in FIG. 10B has a light quantity on the right side (lens barrel side) with respect to the light distribution center 20 corresponding to the exit optical axis center 14p of the exit surface 14e. It can be seen that the balance between the left and right is improved with little depression as shown by the circle 18a.

  In this embodiment, the exit surface 14e of the optical prism 14 is offset to the lens barrel side, but the entrance surface side of the optical prism 14 including the Xe tube 12 and the total reflection surface 14f may be offset to the camera outer peripheral side. .

  As the tilt angle α of the exit surface 14e increases, the tilt of the exit optical axis center 14p also increases and the offset amount Ax also increases. That is, in the light distribution characteristic adjusting method of this embodiment, the larger the maximum inclination angle α between the effective exit surface 14e and the surface P orthogonal to the optical axis O, the greater the exit optical axis center 14p and the exit optical axis in FIG. An interval (offset amount) in the direction perpendicular to the emission optical axis center 12b from the center 12b is set large. The offset direction is a direction that requires correction (a direction in which light distribution is insufficient). As described above, the flash light emitting unit 6 can suppress uneven light distribution without increasing the size even if the exit surface 14e of the optical prism 14 is inclined.

  Next, a method of adjusting the angle of the prism shape 14g on the exit surface 14e will be described with reference to FIGS. The prism shape 14g has a function of adjusting the light distribution angle of the left and right light beams to be emitted and improving the guide number by restricting the light beams that go outside the angle of view.

  FIG. 11 is a ray diagram of the prism shape 14g of FIG. As shown in the figure, the prism shape 14g can be divided into a central portion 14ga and both end portions 14gb and 14gc opposed to the arc length of the Xe tube 12.

  The central portion 14ga of the prism shape 14g is bilaterally symmetric with respect to the center of the camera optical axis, and the angle γ is adjusted to a light distribution angle necessary to satisfy the shooting field angle of the camera. The light beam that passes through the central portion 14ga is divided into a light beam that is refracted and then emitted to the subject, and a light beam that is totally reflected twice on the exit surface and returns to the reflector 11 and then re-irradiated to the optical prism 14. The guide number can be improved by repeating the reflection of the light beam deviating from the required light distribution angle until the desired irradiation angle is obtained.

  Both end portions 14gb and 14gc of the prism shape 14g are located outside the arc length portion of the Xe tube 12, and the prism angle δ is adjusted so as to refract the light beam irradiated in the oblique direction toward the photographing field angle. The

  In this way, by adjusting the angles γ and δ, unevenness in light distribution is reduced and the guide number is improved.

  Note that the imaging apparatus of the present invention is not limited to a digital camera, and can be applied to various cameras such as a single-lens reflex camera, a portable terminal, and a video camera.

2 Lens barrel 6 Flash emission unit 11 Reflector umbrella 12 Xe tube 14 Optical prism

Claims (2)

A shooting optical system for shooting the subject;
Light emitting means;
An incident surface on which light from the light emitting means is incident, a total reflection surface that totally reflects a part of the light incident on the incident surface, and an optical prism having an exit surface,
The exit surface of the optical prism and the central axis of the light emitting means are parallel,
The exit optical axis center of the exit surface of the optical prism and the exit optical axis center of the light emitting means are both non-parallel to the optical axis of the imaging optical system,
The distance from the plane perpendicular to the optical axis of the imaging optical system to the exit surface of the optical prism increases as the distance from the optical axis of the imaging optical system increases.
The light emitting means and the optical prism are arranged such that the exit optical axis center of the exit surface of the optical prism is closer to the optical axis of the photographing optical system than the exit optical axis center of the flash tube. An imaging device that is characterized. The larger the angle formed by the plane perpendicular to the optical axis of the imaging optical system and the exit surface of the optical prism, the greater the exit optical axis center of the exit surface of the optical prism and the exit optical axis center of the flash arc tube The imaging apparatus according to claim 1, wherein an offset amount of the imaging apparatus is increased.