JP4717835B2 - Illumination device and imaging device - Google Patents

Description

  The present invention relates to an illumination device that efficiently collects light emitted from a light source such as a light-emitting diode with respect to a necessary irradiation range, and an imaging device including the illumination device.

  As an illuminating device using a light emitting diode (hereinafter referred to as LED) as a light source, a lighting device utilizing the light condensing action of the LED itself has been put into practical use. The LED used in such a lighting device is referred to as a so-called dome type LED. In the dome type LED, an LED chip is fixed in a metal cup that becomes a reflecting mirror, and a dome-shaped transparent resin having a light condensing function is formed on a surface on the emission side of the metal cup. In this illumination device, the degree of light collection can be varied by changing the diameter or curvature of the dome. And the illuminating device using such a dome type LED is disclosed by patent document 1. FIG.

  On the other hand, Patent Document 2 discloses an illuminating device configured to condense a light beam emitted from an LED by a convex lens arranged on the light irradiation side of the LED without condensing the LED. Yes.

Further, Patent Document 1 discloses an illumination device that does not have a condensing function on an LED, reflects a light beam emitted from the LED in a direction opposite to the light irradiation direction in the prism, changes the direction, and emits the light toward a necessary irradiation range. 3 is disclosed.

Japanese Patent Laid-Open No. 10-21703 (paragraph numbers 0011 to 0013, FIG. 1, etc.) Japanese Unexamined Patent Publication No. 2000-89318 (paragraph numbers 0005 to 0006, FIG. 1, etc.) Japanese Patent Laid-Open No. 10-164315 (paragraph numbers 0030 to 0033, FIG. 1, FIG. 2, etc.)

  In the dome type LED, the dome is arranged at an optimal position with respect to the LED chip so as to improve the light collecting performance. However, the light irradiation characteristics as an illumination device using the LED depend on the optical specification of the LED. There are many cases. That is, the light condensing performance of the LED is not always optimal with respect to the light irradiation characteristics required for the illumination device. For this reason, in order to irradiate the light from LED efficiently to the required irradiation range of an illuminating device, the optical system (optical member) which controls the light from LED is separately needed like the structure shown in patent document 1. Become. In this case, the addition of the optical system increases the size of the lighting device or increases the cost.

  Furthermore, the dome-type LED has a generally long overall length and is inconvenient to be incorporated in an optical apparatus such as an imaging apparatus that is becoming smaller.

  On the other hand, a surface-emitting type LED that is not a dome type normally collects light by a convex lens formed on the light irradiation side, as disclosed in Patent Document 2. Condensing by the convex lens can brightly illuminate a specific region including the irradiation optical axis in the light irradiation range by appropriately setting the focal length of the lens. However, since a gap is generated between the LED and the convex lens, a part of the light flux from the LED escapes from the gap, and the irradiation efficiency is lowered.

  Moreover, in the condensing optical system using only the refractive action of the convex lens, it is possible to illuminate a region near the irradiation optical axis in the light irradiation range relatively brightly, but to obtain sufficient illuminance in other peripheral regions. Have difficulty. For this reason, it is difficult to illuminate the entire required irradiation range with uniform brightness.

  Further, even in such a surface emitting type LED, the total length of the condensing optical system becomes longer as the condensing action is increased. Therefore, it is not desirable to be incorporated in a small optical device.

  In addition, as disclosed in Patent Document 3, an optical system that converts the traveling direction of a light beam from a surface-emitting type LED is usually a prism surface or a reflection on the side opposite to the light irradiation side with respect to the light source. A surface is arranged and emitted to the light irradiation side while performing direction conversion and light collection.

  However, in the optical system disclosed in Patent Document 3, the light beam near the irradiation optical axis is simply collected sequentially while changing the traveling direction of the light beam by refraction or reflection, and collected using refraction and reflection. It is not configured to improve light efficiency. For this reason, there is a possibility that the light beam deviated from the irradiation optical axis is directed in a direction different from a desired direction (design direction). As a result, it is difficult to efficiently and uniformly irradiate the required irradiation range with the light beam emitted from the LED.

  The present invention can efficiently collect light from a light source such as an LED, and provides a small (thin) lighting device.

  An illumination device according to an aspect of the present invention reflects a light source and a light beam incident at a specific angle among light beams from the light source, and reflects and transmits light incident at an angle other than the specific angle. And an irradiation reflection surface that reflects the light beam transmitted through the reflection / transmission surface to the light irradiation side. Further, a light beam splitting unit that divides a divergent light beam from the light source into a light beam incident on the reflection / transmission surface at a specific angle and a light beam incident on the reflection / transmission surface at an angle other than the specific angle between the light source and the reflection / transmission surface. It is characterized by having.

  Note that an imaging apparatus including the above-described illumination apparatus and an imaging system that captures an object illuminated by light from the illumination apparatus also constitutes another aspect of the present invention.

  According to the present invention, the light beam from the light source is divided into the light beam part reflected to the light irradiation side by the reflection / transmission surface and the light beam part transmitting the light beam in the light beam dividing part, and further irradiated with the light beam transmitted through the reflection / transmission surface. Reflected on the light irradiation side by the reflecting surface. Thereby, although it is a small structure, it has high condensing performance, and it becomes possible to irradiate the light from a light source efficiently to a required irradiation range with uniform brightness.

  And by using such an illuminating device, size reduction of an imaging device and improvement of illumination imaging performance can be aimed at.

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

  A lighting apparatus that is Embodiment 1 of the present invention will be described with reference to FIGS. The illumination device of the present embodiment can efficiently collect light emitted from a minute surface-emitting type light source such as an LED. More specifically, the illumination device according to the present embodiment divides a light beam having a wide angle range emitted from the light source into a plurality of light beams having a narrow angle range by a light beam splitting unit described later, and the direction changing unit described later. The direction is changed to the light irradiation side by being reflected by different reflecting surfaces.

  FIG. 1 is a longitudinal sectional view of an optical system (hereinafter referred to as an illumination optical system) of the illumination apparatus of Example 1, and FIG. 2 is a view of the illumination optical system as viewed from the back side. FIG. 3 is a diagram showing an external appearance of a digital still camera (imaging device) incorporating the illumination device of this embodiment. 4 is a ray tracing diagram in which rays emitted from the center of the light source are added to the longitudinal sectional view shown in FIG. Further, FIGS. 5 to 7 are diagrams showing the ray tracing diagram shown in FIG. 4 separately for each divided light beam.

  In the digital still camera shown in FIG. 3, reference numeral 11 denotes a camera body, and 12 denotes a lens barrel provided on the front surface of the camera body 11. Reference numeral 13 denotes an illumination device of the present embodiment. The illumination device 13 is incorporated in the upper right part of the camera body 11 and illuminates a subject located on the light irradiation side. Reference numeral 14 denotes an image sensor such as a CCD sensor or a CMOS sensor, which is arranged in the camera body 11 and photoelectrically converts a subject image formed by the imaging optical system in the lens barrel 12. An image is generated based on the electrical signal output from the image sensor 14, and the image is recorded on a recording medium such as a semiconductor memory (not shown). The lens barrel 12 (imaging optical system) and the imaging element 14 constitute an imaging system.

  1, 2, 4 to 7, 1 to 3 are surface-emitting type LEDs that are light sources (different from the dome type LED disclosed in Patent Document 1), and 4 denotes a light beam emitted from the LEDs 1 to 3. It is an optical member for condensing.

  Reference numeral 5 denotes a hard substrate that holds each LED fixedly and is electrically connected to each LED. Each LED is a high-intensity white LED that has uniform light distribution characteristics over a wide angle range in its light emission direction and can emit steady light for a certain period of time. Each LED is fixed to the hard substrate 5 by an electrical connection method such as soldering. The hard substrate 5 is fixed to the chassis in the camera body 11. Reference numeral 6 denotes an exterior member of the camera body 11 shown in FIG.

  In addition, since the structure of surface emitting LED 1-3 is well-known, detailed description is abbreviate | omitted here.

  AXL shown in FIG. 4 is an irradiation optical axis from the optical member 4 toward the light irradiation side, and an optical path after a light beam emitted vertically upward from the center of the LED light emission surface to the light emission surface is emitted from the emission surface 4h. It corresponds to. In the present embodiment, the irradiation optical axis AXL is set so as to be inclined in parallel or slightly downward to the optical axis of the imaging optical system.

  Next, the optical member 4 will be described. The optical member 4 is an integrally formed member for condensing and controlling the light beams emitted from the LEDs 1 to 3, and is formed of a highly transparent resin material.

  In the light beam splitting portion 4A provided for each LED on the optical member 4, an incident surface 4a is formed so as to face the light emitting surface of each LED. The incident surface 4a is a surface on which the light beam from each LED first enters in the optical member 4, and is formed as a flat surface in this embodiment. Moreover, the incident surface 4a has the same shape and area as the light emission surface of each LED. Here, the same shape and area mean not only the case where they are completely the same, but also the case where they are not completely the same within the range of manufacturing errors. By making the shape and area of the incident surface 4a the same as the light emitting surface of each LED, it is possible to prevent the light flux emitted from each LED from leaking out of the light beam splitting section 4A and to have a minimum incident area. The subsequent enlargement of the optical system is suppressed.

  Reference numerals 4c and 4b denote first and second light guide reflection surfaces (first and second reflection surfaces), which are formed as surfaces extending from the end of the incident surface 4a toward the first reflection / transmission surface 4d described later. Yes. The first transmission / reflection surface 4c is formed on the light beam splitting portion 4A on the side opposite to the light irradiation side, and the second light guide reflection surface 4b is formed on the light beam splitting portion 4A on the light irradiation side. . In addition, the first and second light guide reflection surfaces 4c and 4b have a distance from the center line (line perpendicular to the LED light emitting surface) of the light beam splitting portion 4A shown by a one-dot chain line in FIG. To the first reflection / transmission surface 4d side. In addition, you may form the 1st and 2nd light guide reflective surfaces 4c and 4b as a curved surface.

  By forming these light guide reflection surfaces 4c and 4b in the light beam splitting portion 4A, the divergent light beam from each LED is directly converted into a light beam (third light beam), a first reflected light beam (first light beam), and a second light beam. The reflected light beam (second light beam) can be divided into three.

  As shown in FIGS. 4 and 6, the direct light beam is incident from the incident surface 4a and is not reflected by the first and second light guide reflection surfaces 4c and 4b, that is, between the light guide reflection surfaces 4c and 4b. Directly enters the first reflection / transmission surface 4d through the light passage region. Further, as shown in FIGS. 4 and 5, the first reflected light beam enters from the incident surface 4a, is totally reflected by the first light guide reflection surface 4c, and enters the first reflection / transmission surface 4d. Further, as shown in FIGS. 4 and 7, the second reflected light beam enters from the incident surface 4a, is totally reflected by the second light guide reflection surface 4b, and enters the first reflection / transmission surface 4d.

  In addition, by adjusting the length, inclination, and curvature of the light guide reflection surfaces 4c and 4b, the ratio of the direct light flux to the first and second reflected light fluxes in the light flux from the LED can be arbitrarily set.

  As described above, the light beam splitting unit 4A travels all the light beams from the LEDs 1 to 3 as the light sources toward the first reflection / transmission surface 4d, that is, the incident angle to the first reflection / transmission surface 4d. It can be divided into a plurality of light fluxes having different (incident angle ranges).

  Reference numeral 4B denotes a direction changing portion in the optical member 4, and 4d and 4e denote first and second reflection / transmission surfaces formed on the side opposite to the exit surfaces 4g, 4h, and 4i in the direction changing portion 4B.

  The direct light beam is incident on the first reflection / transmission surface 4d at an angle smaller than the critical angle that is the minimum angle that satisfies the total reflection condition (an angle other than the specific angle: the second angle). For this reason, the direct light is transmitted through the first reflection / transmission surface 4d.

  The first reflected light beam is incident on the first reflection / transmission surface 4d at an angle greater than the critical angle (specific angle: first angle). For this reason, the first reflected light flux is totally reflected by the first reflection / transmission surface 4d and travels toward the light irradiation side.

  Furthermore, the second reflected light beam is incident on the first reflection / transmission surface 4d at an angle smaller than the critical angle (an angle other than the specific angle: the second angle). Therefore, the second reflected light beam is transmitted through the first reflection / transmission surface 4d. However, the incident angle of the direct light flux on the first reflection / transmission surface 4d is different from the incidence angle of the second reflection light flux on the first reflection / transmission surface 4d.

  The direct light beam transmitted through the first reflection / transmission surface 4d is refracted by the first reflection / transmission surface 4d, is incident on the transmission surface 4k, which is an intermediate surface, and is further refracted by the transmission surface 4k. It is incident on the reflection / transmission surface 4e at an angle greater than the critical angle (specific angle: third angle). For this reason, the direct light beam is totally reflected by the second reflection / transmission surface 4e.

  On the other hand, the second reflected light beam that has passed through the first reflection / transmission surface 4d is refracted by the first reflection / transmission surface 4d and incident on the transmission surface 4k, and further refracted by the transmission surface 4k. The light enters the reflection / transmission surface 4e at an angle smaller than the critical angle (an angle other than the specific angle: a fourth angle). For this reason, the second reflected light beam passes through the second reflection / transmission surface 4e.

  The second reflected light beam transmitted through the second reflection / transmission surface 4e is refracted by the second reflection / transmission surface 4e, is incident on the transmission surface 4m as an intermediate surface, and is further refracted by the transmission surface 4m. It is incident on the irradiation reflection surface 4f as the final reflection surface at an angle greater than the critical angle. For this reason, the second reflected light is totally reflected by the irradiation reflection surface 4f.

  As described above, the direct light beam, the first reflected light beam, and the second reflected light beam divided by the light beam dividing unit 4A are separated into the total reflected light beam and the transmitted light beam by the first and second reflection / transmission surfaces 4d and 4e. Then, it is reflected to the light irradiation side by different surfaces 4d, 4e, 4f. The direct light beam, the first reflected light beam, and the second reflected light beam are emitted from different exit surfaces 4g, 4h, and 4i toward the necessary irradiation range on the light irradiation side.

  In other words, the divergent light beam emitted from the LED is divided into three light beams having different angle ranges by the light beam dividing unit 4A, and the two reflection / transmission surfaces 4d and 4e of the direction changing unit 4B are divided with respect to these three light beams. Selectively function as a total reflection surface or transmission surface. Thereby, the divergent light beam (light beam with no directivity) from the LED can be converted into a light beam with high directivity and irradiated to the necessary irradiation range.

  With the above configuration, as shown in FIG. 4, the exit directions of the three light beams divided and separated by the light beam dividing unit 4A and the direction changing unit 4B (first and second reflection / transmission surfaces 4d and 4e) are made the same. can do. As a result, it is possible to obtain an illumination light beam having the same emission direction as a whole (emitted in a direction parallel to the irradiation optical axis AXL in the cross section of FIG. 4). Here, the same injection direction means not only the case where they are completely the same, but also the case where they are aligned to such an extent that they can be regarded as the same.

  That is, a light beam emitted from a light source toward a wide angle range can be converted into a light beam having high directivity and finally having a uniform direction. In addition, by effectively using the reflecting surface, the thickness of the entire illumination optical system in the direction of the irradiation optical axis can be suppressed.

  Further, the center of the light emitting surface (light emission center) of each LED is arranged at a position on the light irradiation side with respect to the light transmission side opposite to the light irradiation side of the reflection / transmission surfaces 4d and 4e and the irradiation reflection surface 4f. Yes. Thereby, an illuminating device can be made thinner.

  Hereinafter, the shape of the optical member 4 will be described in more detail with reference to FIGS.

  In general, a large emission area is required to align the traveling direction of divergent light beams emitted from a light source in a wide angle range in a certain direction. Moreover, unless a certain optical path length is ensured from the light source to the exit surface of the optical member, it is difficult to efficiently collect light.

  On the other hand, in the present embodiment, the light beam splitting unit 4A efficiently splits the divergent light beam emitted from the light source using total reflection into a plurality of light beams having different traveling directions, and further, the direction conversion unit 4B performs total reflection. By using this, the entire illumination optical system is downsized. In this embodiment, since all the light beams can be controlled by the optical member 4 as a single component, an illumination optical system with good accuracy can be configured at low cost.

  In FIG. 5, the first reflected light beam that is emitted from the LED 1 (˜3) as the light source and totally reflected by the first light guide reflection surface 4 c is arranged symmetrically with the LED 1 with respect to the first light guide reflection surface 4 c. This is equivalent to a light beam emitted from the apparent LED 1a and transmitted through the first light guide reflection surface 4c. This is equivalent to shifting the position of the LED 1 to the position 1a by interposing the first light guide reflection surface 4c. By adopting such a configuration, it is possible to adjust conditions under which the first reflected light beam is likely to be totally reflected by the first reflection / transmission surface 4d. That is, the total reflection on the first reflection / transmission surface 4d can be reliably performed and guided to the emission surface 4g.

  The exit surface 4g converts the traveling direction of the first reflected light beam reflected obliquely downward by the first reflection / transmission surface 4d into a direction parallel to the irradiation optical axis AXL. It is configured as a plane inclined by an angle. However, the exit surface 4g may be configured as a curved surface, and this is the same for the other exit surfaces 4h and 4i.

  The first reflection / transmission surface 4d is formed as a curved surface in the present embodiment, but may be a flat surface. Further, in the cross section of FIG. 5, the first light guide reflection surface 4c is such that the amount of the first reflected light beam reflected here is one third of the total amount of the emitted light beam from the center of the light source. , Tilt and position are set. However, 1/3 here does not need to be exact 1/3. This also applies to the description of FIGS. 6 and 7 below.

  In FIG. 6, the direct light beam emitted from the LED 1 (˜3) passes through the first reflection / transmission surface 4 d and is refracted here as described above, and then re-enters the optical member 4 while being refracted from the transmission surface 4 k. To do. Then, the light is totally reflected by the second reflection / transmission surface 4e and emitted from the emission surface 4h.

  The exit surface 4h converts the traveling direction of the direct light beam reflected obliquely downward by the second reflection / transmission surface 4e into a direction parallel to the irradiation optical axis AXL, and therefore from the first angle with respect to the irradiation optical axis AXL. The plane is inclined by a small second angle.

  The second reflection / transmission surface 4e is formed as a curved surface in the present embodiment, but may be a flat surface. Further, in the cross section of FIG. 6, the distance between the first and second light guide reflection surfaces 4c and 4b is such that the amount of direct light beam is one third of the total amount of light beam emitted from the center of the light source. Is set.

  In FIG. 7, the second reflected light beam emitted from the LED 1 (˜3) and totally reflected by the second light guide reflection surface 4 b is apparently arranged symmetrically with the LED 1 with respect to the second light guide reflection surface 4 b. This is equivalent to a light beam emitted from the LED 1b and transmitted through the second light guide reflection surface 4b. This is equivalent to shifting the position of the LED 1 to the position 1b by interposing the second light guide reflection surface 4b. By adopting such a configuration, it is possible to prepare a condition in which the second reflected light beam is transmitted through the first reflection / transmission surface 4d and the second reflection / transmission surface 4e and is easily totally reflected by the irradiation / reflection surface 4f. it can. That is, the second reflected light beam can be guided to the exit surface 4i by surely transmitting the first reflected / transmitted surface 4d and the second reflected / transmitted surface 4e and totally reflecting the irradiation / reflecting surface 4f. become.

  The exit surface 4i is configured as a plane orthogonal to the illumination optical axis AXL in order to directly emit the second reflected light beam reflected by the illumination reflection surface 4f in a direction parallel to the illumination optical axis AXL.

  In the present embodiment, the irradiation reflection surface 4f is formed as a curved surface, but may be a flat surface. In addition, in the cross section of FIG. 7, the second light guide reflection surface 4b is such that the amount of the second reflected light beam reflected here is one third of the total amount of the emitted light beam from the center of the light source. , Tilt and position are set.

  As described above, in the present embodiment, the light beam splitting section 4A divides the light beam emitted from the light source center into three equal parts (however, it does not have to be exactly three equal parts) and guides it to the direction changing part 4B. As a result, the three divided light beams can be totally reflected in the desired direction by the reflection / transmission surfaces 4d and 4e and the irradiation / reflection surface 4f having the minimum area. As a result, the entire illumination optical system can be reduced in size.

  The first and second light guide reflection surfaces 4c and 4b, the first and second reflection / transmission surfaces 4d and 4e, and the irradiation reflection surface 4f all function as total reflection surfaces. For this reason, compared with the case where the reflective surface by metal vapor deposition is formed, the optical member 4 can be manufactured at low cost and the reflection efficiency can be improved.

  A lighting apparatus that is Embodiment 2 of the present invention will be described with reference to FIGS. Similarly to the lighting device of the first embodiment, the lighting device of the present embodiment can also efficiently collect light emitted from a minute surface-emitting type light source such as an LED. The illumination device of this embodiment is also built in the digital still camera shown in FIG.

  FIG. 8 is a longitudinal sectional view of the illumination optical system of the illuminating device of Example 2, and FIG. 9 is a ray tracing diagram in which rays emitted from the light source center are added to the longitudinal sectional view shown in FIG. Further, FIG. 10 to FIG. 12 are diagrams showing the ray tracing diagram shown in FIG. 9 separately for each divided light beam.

  In the first embodiment, the case where the light beam splitting portion 4 </ b> A is integrally formed with the optical member 4 has been described. However, in this embodiment, the light beam splitting portion is configured by a member different from the optical member 24.

  In each figure, reference numeral 21 denotes a surface-emitting type LED as a light source, and although not shown, three are provided as in the first embodiment. Reference numeral 23 denotes a reflecting member constituting the light beam splitting unit. Reference numeral 24 denotes an optical member for condensing the light beam emitted from the LED 21 and passing through the light beam splitting unit, and functions as a direction changing unit.

  Reference numeral 25 denotes a hard board that holds the LED 21 fixedly and is electrically connected to the LED 21. The LED 21 is a high-intensity white LED that has a uniform light distribution characteristic over a wide angle range in the light emission direction and can emit steady light for a certain period of time. The LED 21 is fixed to the hard substrate 25 by an electrical connection method such as soldering.

  High reflectance is given to the inner surfaces 23c and 23b facing the light emitting surface of the LED 21 in the reflecting member 23 (light passage region) by means such as metal vapor deposition. In the following description, the inner surfaces 23c and 23b are referred to as first and second light guide reflection surfaces (first and second reflection surfaces) 23c and 23b.

  The incident-side opening 23a formed by being sandwiched between the first and second light guide reflection surfaces 23c and 23b has the same shape and area as the light emitting surface of the LED 21. Here, the same shape and area mean not only the case where they are completely the same, but also the case where they are not completely the same within the range of manufacturing errors. As a result, the luminous flux emitted from the LED 21 is prevented from leaking outside the first and second light guide reflection surfaces 23c and 23b, and the aperture area of the optical system subsequent thereto is reduced to a minimum opening area. The increase in size is suppressed.

  The first and second light guide reflection surfaces 23c and 23b are formed as surfaces extending from the LED 21 side to a first reflection / transmission surface 24d described later. The first light guide reflection surface 23 c is formed on the side opposite to the light irradiation side of the reflection member 23, and the second light guide reflection surface 23 b is formed on the light irradiation side of the reflection member 23. Further, the first and second light guide reflection surfaces 23c and 23b are respectively spaced from the LED 21 side by a distance from the center line of the reflection member 23 (a line perpendicular to the light emitting surface of the LED 21) shown by a one-dot chain line in FIG. 1 is formed as an inclined surface that gradually increases toward the reflection / transmission surface 24d side. However, you may form the 1st and 2nd light guide reflective surfaces 23c and 23b as a curved surface.

  By forming these light guide reflection surfaces 23c and 23b on the reflecting member 23, the divergent light beam from the LED 21 is directly converted into a light beam (third light beam), a first reflected light beam (first light beam), and a second reflected light beam. It can be divided into three (second light flux).

  As shown in FIGS. 9 and 11, the direct light beam is not reflected by the first and second light guide reflection surfaces 23c and 23b (through the light passage region between the light guide reflection surfaces 23c and 23b). The light directly enters the first reflection / transmission surface 24 d of the optical member 24 through the incident surface 24 a of the optical member 24. Further, as shown in FIGS. 9 and 10, the first reflected light beam is reflected by the first light guide reflection surface 23c and enters the first reflection / transmission surface 24d through the incident surface 24a. Further, as shown in FIGS. 9 and 12, the second reflected light beam is reflected by the second light guide reflection surface 23b via the incident surface 24a and enters the first reflection / transmission surface 24d.

  In addition, by adjusting the length, inclination, and curvature of the light guide reflection surfaces 23c and 23b, the ratio of the direct light flux, the first reflected light flux, and the second reflected light flux in the light flux from the LED can be arbitrarily set. it can.

  As described above, the reflection member 23 as the light beam splitting unit directs all the light beams from the LED 21 as the light source toward the first reflection / transmission surface 24d, that is, toward the first reflection / transmission surface 24d. It can be divided into a plurality of light beams having different incident angles.

  Next, the optical member 24 will be described. The optical member 24 is an integrally formed member for condensing control of the light beam emitted from the LED 21 and is formed of a highly transparent resin material.

  The optical member 24 has a first reflection / transmission surface 24d, a second reflection / transmission surface 24e, and an irradiation / reflection surface 24f formed on the side opposite to the exit surface 24g. The light is guided to the exit surface 24g by total reflection or transmission.

  The direct light beam is incident on the first reflection / transmission surface 24d at an angle smaller than the critical angle (an angle other than the specific angle: a second angle). Therefore, the direct light is transmitted through the first reflection / transmission surface 24d.

  The first reflected light beam is incident on the first reflection / transmission surface 24d at an angle (specific angle: first angle) equal to or greater than the critical angle. For this reason, the first reflected light beam is totally reflected by the first reflection / transmission surface 24d and travels toward the light irradiation side.

  Furthermore, the second reflected light beam is incident on the first reflection / transmission surface 24d at an angle smaller than the critical angle (an angle other than the specific angle: the second angle). Therefore, the second reflected light beam is transmitted through the first reflection / transmission surface 24d. However, the incident angle of the direct light flux on the first reflection / transmission surface 24d is different from the incidence angle of the second reflection light flux on the first reflection / transmission surface 24d.

  The direct light beam transmitted through the first reflection / transmission surface 24d is refracted by the first reflection / transmission surface 24d, is incident on the transmission surface 24k as an intermediate surface, and is further refracted by the transmission surface 24k. It is incident on the reflection / transmission surface 24e at an angle greater than the critical angle (specific angle: third angle). For this reason, the direct luminous flux is totally reflected by the second reflection / transmission surface 24e.

  On the other hand, the second reflected light beam that has passed through the first reflection / transmission surface 24d is refracted by the first reflection / transmission surface 24d and incident on the transmission surface 24k, and further refracted by the transmission surface 24k. It is incident on the reflection / transmission surface 24e at an angle smaller than the critical angle (an angle other than the specific angle: a fourth angle). Therefore, the second reflected light beam passes through the second reflection / transmission surface 24e.

  The second reflected light beam transmitted through the second reflection / transmission surface 24e is refracted by the second reflection / transmission surface 24e, is incident on the transmission surface 24m as an intermediate surface, and is further refracted by the transmission surface 24m. It is incident on the irradiation reflection surface 24f as the final reflection surface at an angle greater than the critical angle. For this reason, the second reflected light is totally reflected by the irradiation reflection surface 24f.

  As described above, the direct light beam, the first reflected light beam, and the second reflected light beam divided by the reflecting member 23, which is a light beam dividing unit, are transmitted through the first and second reflection / transmission surfaces 24d and 24e with the total reflection light beam. It is separated into luminous fluxes and reflected on the light irradiation side by different surfaces 24d, 24e and 24f. The direct light beam, the first reflected light beam, and the second reflected light beam are emitted from the exit surface 24g toward the required irradiation range on the light irradiation side.

  In other words, the divergent light beam emitted from the LED is divided into three light beams having different angle ranges by the reflecting member 23, and the two reflection / transmission surfaces 24d and 24e are divided into a total reflection surface or a transmission surface with respect to these three light beams. To function selectively. Thereby, the divergent light beam (light beam with no directivity) from the LED can be converted into a light beam with high directivity and irradiated to the necessary irradiation range.

  With the above configuration, as shown in FIG. 9, the emission directions of the three light beams divided and separated by the reflection member 23 and the optical member 24 (first and second reflection / transmission surfaces 24d and 24e) are made the same. Can do. As a result, it is possible to obtain an illumination light beam having the same emission direction as a whole (emitted in a direction parallel to the irradiation optical axis AXL in the cross section of FIG. 9). Here, the same injection direction means not only the case where they are completely the same, but also the case where they are aligned to such an extent that they can be regarded as the same.

  That is, a light beam emitted from a light source toward a wide angle range can be converted into a light beam having high directivity and finally having a uniform direction. In addition, by effectively using the reflecting surface, the thickness of the entire illumination optical system in the direction of the irradiation optical axis can be suppressed.

  Furthermore, the center (light emission center) of the light emitting surface of the LED 21 is arranged at a position closer to the light irradiation side than the outermost end portion P opposite to the light irradiation side of the reflection / transmission surfaces 24d and 24e and the irradiation reflection surface 24f. . Thereby, an illuminating device can be made thinner.

  In this embodiment, the emission surface 24g is formed as a continuous single surface. By configuring the exit surface 24g as a single surface, the exit surface 24g having no step can be exposed as a product appearance, which is advantageous in terms of camera design. Further, by making at least a part of the exit surface 24g a curved surface and adjusting the curvature and inclination (inclination of tangent) for each exit area of the divided light beam, an illumination light beam having a uniform direction as a whole can be obtained.

  Hereinafter, the shape of the optical member 24 will be described in more detail with reference to FIGS. Also in the present embodiment, similarly to the first embodiment, the divergent light beam emitted from the light source in the reflecting member 23 is divided into a plurality of light beams having different traveling directions, and further, the total reflection is used in the optical member 24, thereby providing illumination. The entire optical system is downsized.

  In FIG. 10, the first reflected light beam emitted from the LED 21 and totally reflected by the first light guide reflection surface 23c is emitted from the apparent LED 21a arranged symmetrically with the LED 21 with respect to the first light guide reflection surface 23c. This is equivalent to the light beam transmitted through the first light guide reflection surface 23c. This is equivalent to shifting the position of the LED 21 to the position of 21a by interposing the first light guide reflection surface 23c. By adopting such a configuration, it is possible to adjust conditions under which the first reflected light beam is likely to be totally reflected by the first reflection / transmission surface 24d. That is, total reflection on the first reflection / transmission surface 24d can be performed reliably and guided to the exit surface 24g.

  The first reflected light beam is reflected obliquely downward by the first reflection / transmission surface 24d. The exit area of the first reflected light beam in the exit surface 24g converts the traveling direction of the first reflected light beam into a direction parallel to the irradiation optical axis AXL, so that its tangent is first with respect to the irradiation optical axis AXL. It is comprised as a curved surface inclined in the angle range.

  Further, the first reflection / transmission surface 24d is formed as a curved surface in the present embodiment, but may be a flat surface. Further, in the cross section of FIG. 10, the first light guide reflection surface 23c is such that the amount of the first reflected light beam reflected here is one third of the total amount of the emitted light beam from the center of the light source. , Tilt and position are set. However, 1/3 here does not need to be exact 1/3. This also applies to the description of FIGS. 11 and 12 below.

  In FIG. 11, the direct luminous flux emitted from the LED 21 passes through the first reflection / transmission surface 24d and is refracted here as described above, and then reenters the optical member 24 while being refracted from the transmission surface 24k. Then, the light is totally reflected by the second reflection / transmission surface 24e and emitted from the emission surface 24g.

  The direct light beam is reflected obliquely downward by the second reflection / transmission surface 24e. The exit area of the direct light beam in the exit surface 24g converts the traveling direction of the direct light beam into a direction parallel to the irradiation optical axis AXL, so that the tangent line is smaller than the first angle range with respect to the irradiation optical axis AXL. It is configured as a curved surface inclined in an angle range of 2.

  The second reflection / transmission surface 24e is formed as a curved surface in this embodiment, but may be a flat surface. Further, in the cross section of FIG. 11, the distance between the first and second light guide reflection surfaces 23c and 23b is such that the amount of direct light beam is one third of the total amount of light beam emitted from the center of the light source. Is set.

  In FIG. 12, the second reflected light beam emitted from the LED 21 and totally reflected by the second light guide reflection surface 23b is emitted from the apparent LED 21b arranged symmetrically with the LED 21 with respect to the second light guide reflection surface 23b. This is equivalent to the light beam transmitted through the second light guide reflection surface 23b. This is equivalent to shifting the position of the LED 21 to the position of 21b by interposing the second light guide reflection surface 23b. By adopting such a configuration, it is possible to prepare a condition in which the second reflected light beam is transmitted through the first reflection / transmission surface 24d and the second reflection / transmission surface 24e and is easily totally reflected by the irradiation / reflection surface 24f. it can. In other words, the second reflected light beam can be reliably transmitted through the first reflection / transmission surface 24d and the second reflection / transmission surface 24e and totally reflected by the irradiation / reflection surface 24f and guided to the exit surface 24g. become.

  The upper part of the exit surface 24g is configured as a plane orthogonal to the illumination optical axis AXL in order to emit the second reflected light beam reflected by the illumination reflection surface 24f in a direction parallel to the illumination optical axis AXL. However, this injection area may be a curved surface.

  In the cross section of FIG. 12, the second light guide reflection surface 23b is such that the amount of the second reflected light beam reflected here is one third of the total amount of the emitted light beam from the center of the light source. , Tilt and position are set.

  As described above, in the present embodiment, the light beam emitted from the center of the light source is divided into three equal parts (however, it may not be strictly equal to three equal parts) in the reflecting member 23 and guided to the optical member 24. Thereby, the three divided light beams can be totally reflected in a desired direction by the reflection / transmission surfaces 24d and 24e and the irradiation / reflection surface 24f having the minimum area, and as a result, the entire illumination optical system can be reduced in size.

  The first and second reflection / transmission surfaces 24d and 24e and the irradiation / reflection surface 24f all function as a total reflection surface. For this reason, compared with the case where the reflective surface by metal vapor deposition is formed, the optical member 24 can be manufactured at low cost and the reflection efficiency can be improved.

  Note that an optical member (an optical member different from the optical member 24) formed of a transparent resin is used in place of the reflecting member 23, and the light flux from the light source is 3 by utilizing total reflection on the inner surface of the optical member. You may make it divide into two.

  In the present embodiment, the exit surface 24g of the optical member 24 is configured as a single surface, but this surface may be configured as an optical functional surface such as a Fresnel lens. Use of the Fresnel lens is preferable because the optical performance of the illumination optical system is less influenced by the external shape of the camera.

  As described above, according to each of the above-described embodiments, it is possible to efficiently collect a light beam from a light source such as an LED and realize a thin illuminating device with a small volume occupied by the optical system. Furthermore, basically, the above effect can be obtained only by optimizing the shape of the optical member, and no special configuration is required. For this reason, an illuminating device can be manufactured cheaply.

  In each of the above-described embodiments, the case where two reflection / transmission surfaces of the direction changing unit are provided has been described, but three or more reflection / transmission surfaces may be provided. Increasing the number of reflection / transmission surfaces may further reduce the thickness of the illumination optical system.

  Moreover, it is good also considering the reflection / transmission surface formed in an optical member as one surface. Thereby, the shape of an optical member can be simplified and manufacture can be made easy.

  Further, in each of the above embodiments, the case where three light sources (LEDs) are used has been described. However, the number of light sources can be appropriately changed according to the brightness of each light source and the required brightness in the irradiation range. .

  In each of the above embodiments, a case where a white light source is used has been described. However, a plurality of monochromatic light sources having different emission colors may be used, or an infrared light source may be used.

  Further, in each of the above-described embodiments, a case has been described in which the three split light beams are emitted from the exit surface in a direction parallel to the irradiation optical axis AXL. However, it is also possible to illuminate a wide irradiation range by making the emission directions of the three emitted light beams different from each other and emitting the light beams with a certain extent as a whole.

  In the above embodiments, the lighting device built in the digital still camera has been described. However, the present invention can also be applied to a lighting device built in or attached to a single-lens reflex camera or a video camera.

1 is a longitudinal sectional view of an illumination optical system that is Embodiment 1 of the present invention. FIG. FIG. 3 is a rear view of the illumination optical system according to the first embodiment. FIG. 3 is an external view of a camera in which the illumination device according to the first embodiment is built. FIG. 2 is a ray tracing diagram in which rays emitted from the center of the light source are added. FIG. 2 is a ray tracing diagram in which rays of a first reflected light beam are added to FIG. 1. FIG. 2 is a ray tracing diagram in which rays of light flux are directly added to FIG. 1. The ray trace figure which added the light ray of the 2nd reflected light beam to FIG. FIG. 6 is a longitudinal sectional view of an illumination optical system that is Embodiment 2 of the present invention. FIG. 9 is a ray tracing diagram in which rays emitted from the center of the light source are added. FIG. 9 is a ray tracing diagram in which rays of the first reflected light beam are added to FIG. 8. FIG. 9 is a ray tracing diagram in which rays of light beams are directly added to FIG. 8. The ray trace figure which added the light ray of the 2nd reflected light beam to FIG.

Explanation of symbols

1, 2, 3, 21 LED
4, 24 Optical member 4a Incident surface 4b, 4c, 24b, 24c Light guide reflection surface 4d, 4e, 24d, 24e Reflection / transmission surface 4f, 24f Irradiation reflection surface 4k, 4m, 24k, 24m Transmission surface 5,25 Hard substrate 6 Camera exterior member 11 Camera body 12 Lens barrel 23 Reflective member 23b, 23c Light guide reflective surface

Claims (9)

A light source;
A reflection / transmission surface that reflects the light beam incident at a specific angle among the light beams from the light source to the light irradiation side and transmits the light incident at an angle other than the specific angle;
An irradiation reflection surface that reflects the light beam transmitted through the reflection / transmission surface to the light irradiation side;
A light beam provided between the light source and the reflection / transmission surface, and a divergent light beam from the light source is incident on the reflection / transmission surface at the specific angle, and a light beam is incident on the reflection / transmission surface at an angle other than the specific angle. And a light beam splitting unit that splits the light into two.   The light emission center of the light source is disposed at a position closer to the light irradiation side than an outermost end of the reflection / transmission surface and the irradiation / reflection surface opposite to the light irradiation side. The lighting device described. The light beam splitting unit has a reflecting surface that reflects a part of the light beam from the light source,
3. The illumination device according to claim 1, wherein the reflection surface is formed such that a distance from a center line of the light beam splitting portion increases from the light source side to the reflection / transmission surface side.   As the reflection / transmission surface, a light beam incident at a first angle is reflected to the light irradiation side, a first reflection / transmission surface that transmits the light beam incident at a second angle, and the first reflection / transmission surface is transmitted. 4. The optical system according to claim 1, further comprising: a second reflection / transmission surface that reflects a light beam incident at a third angle and transmits a light beam incident at a fourth angle. The lighting device described in one. The beam splitting unit has first and second reflecting surfaces,
Of the luminous flux from the light source, the first luminous flux reflected by the first reflecting surface is incident on the first reflecting / transmitting surface at the first angle,
Of the luminous flux from the light source, the second luminous flux reflected by the second reflecting surface is incident on the first reflecting / transmitting surface at the second angle and enters the second reflecting / transmitting surface by the second reflecting surface. Incident at an angle of 4,
Of the luminous flux from the light source, the third luminous flux that is not reflected by the first and second reflective surfaces enters the first reflective / transmissive surface at the second angle and enters the second reflective / transmissive surface. The illumination device according to claim 4, wherein the illumination device is incident at a third angle.   The incident surface on which the light from the light source first enters, the reflection / transmission surface on which the light from the incident surface is incident, the intermediate surface through which the light transmitted through the reflection / transmission surface is transmitted, and the light from the intermediate surface A single optical member formed with the irradiation reflection surface on which light is incident, and an emission surface that emits light reflected by the reflection / transmission surface and the irradiation reflection surface to the light irradiation side. The illumination device according to any one of 1 to 5.   The illumination device according to claim 6, wherein the optical member integrally includes the light beam splitting unit.   The lighting device according to claim 1, wherein the light source is a light emitting diode. The lighting device according to any one of claims 1 to 8,
An imaging apparatus comprising: an imaging system that images a subject illuminated by light from the illumination apparatus.