JPH10123594A - Light distribution lens for stroboscope and zoom stroboscope device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a light distribution lens whose thickness is not increased like a convex lens and which is formed so that the loss of light quantity is reduced and a built-in substance is shielded besides by forming the central part thereof as a convex lens part and forming the periphery as a peripheral convex Fresnel lens part. SOLUTION: This light distribution lens for a stroboscope 10 is formed so that the front surface thereof is provided with a rectangular shape being long in the length direction of a stroboscopic light emission tube. Besides, it is provided with the convex lens part 11 at the central part and the peripheral convex Fresnel lens part 12 surrounding the lens part 11 on the front and the back of the front surface. It is also possible that the lens part 11 and the lens part 12 are formed only on one surf ace out of the front and the back surfaces of the lens 10 and the other surface is formed to be plane according to the set of power. The lens part 11 is circular and it occupies the whole length of the rectangular lens 10 in a short side direction at the central part. The minimum edge thickness (peripheral thickness) of the lens 10 is regulated by a gap between the front and the back lens parts 12 and the maximum thickness is regulated by the thickness of the lens part 11 at the central part.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light distribution lens that collects light in front of a light emitter of a strobe, and a zoom strobe device using the same.

[0002]

2. Description of the Related Art Strobe light distribution lenses of this type have long been composed entirely of convex lenses. However, as the power of the convex lens increases, the thickness of the central portion increases, and it becomes difficult to secure the thickness (edge thickness) of the peripheral portion. For this reason, it becomes difficult to design a lens or secure a space. Also, if the whole is a convex lens, a light emitting device (light emitting tube)
Built-in components such as lead wires, soldered parts, and internal mechanisms are exposed through the convex lens, which is not preferable in appearance.

For this reason, conventionally, a convex Fresnel lens has been widely used as a light distribution lens. Fresnel lens
Theoretically, it can be made thinner while having the same power as the convex lens, and also has the effect of concealing built-in components. However, there is a problem that a light amount loss due to a surface (cylindrical surface) parallel to the optical axis of each ring zone is inevitable. In particular, in a flash device for a compact camera, which is required to be miniaturized in an extreme, it is difficult to use a large-sized light-emitting device having a large amount of light, and light-loss is a serious problem.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a light distribution lens for a strobe, which does not increase the thickness as much as a convex lens, has a small loss of light amount, and has an effect of concealing a built-in object, and a zoom strobe device using this light distribution lens. With the goal.

[0005]

SUMMARY OF THE INVENTION The present invention relates to a stroboscopic light distribution lens that is located in front of a strobe light emitting device and condenses light.
It is characterized in that the periphery of the central convex lens portion is a peripheral convex Fresnel lens portion. In the case where a central convex lens portion and a peripheral convex Fresnel lens portion are provided on both front and rear surfaces, respectively, the peripheral Fresnel lens surfaces on the front and rear surfaces are such that the positions of the cylindrical surfaces parallel to the optical axes of the front and rear orbicular zones do not match in front view. Preferably, the pitches are different from each other. In the peripheral edge Fresnel lens, it is preferable that the depth of each annular zone is set to be substantially constant. The radius of curvature of the central convex lens portion and the radius of curvature of the peripheral Fresnel lens surface can be the same or different, and an aspheric surface can be used.

Further, the present invention provides a light emitting unit, a light distribution lens located in front of the light emitting unit and condensing, and a zoom means for changing a distance between the light emitting unit and the light distribution lens. The zoom strobe device provided is characterized in that at least one central portion of the front and back surfaces of the light distribution lens is a convex lens surface, and the periphery of the central convex lens portion is a peripheral convex Fresnel lens portion.

[0007]

1 and 2 show an embodiment of a light distribution lens 10 for strobe light according to the present invention. The stroboscopic light distribution lens 10 has a front rectangular shape that is long in the length direction of the stroboscopic arc tube, and has a convex lens portion 11 at the center and a convex Fresnel lens portion 12 at the periphery surrounding the central convex lens portion 11 on both sides. Have. Depending on the power setting, the central convex lens portion 11 and the peripheral convex Fresnel lens portion 12 may be formed on only one of the front and back surfaces of the light distribution lens 10 for flash, and the other surface may be flat.

The central convex lens portion 11 has a circular shape, and occupies the entire length in the short side direction at the central portion of the rectangular light distribution lens 10 for a strobe light. In other words, the peripheral convex Fresnel lens portion 12 does not exist around the center of the strobe light distribution lens 10 in the short side direction. In other words, the stroboscopic light distribution lens 10 removes the upper and lower peripheral convex Fresnel lens portions 12 at the central portion from a circular lens having a circular central convex lens portion 11 and an annular peripheral convex Fresnel lens portion 12, and Are formed in a rectangular shape with the peripheral convex Fresnel lens portion 12 left. The minimum edge thickness (peripheral thickness) t of this strobe light distribution lens 10 is the front and back peripheral convex Fresnel lens portion 12.
The maximum thickness T is defined by the thickness of the central portion of the central convex lens portion 11. The chain line in FIG. 2 shows the shape of the stroboscopic light distribution lens 10 including the central convex lens portion 11 and the peripheral convex Fresnel lens portion 12 and the optically uniform convex lens 10 ′ when the light amount loss due to the cylindrical surface 12 b is not considered. ing.

As shown in FIG. 3, the peripheral convex Fresnel lens portion 12 is formed such that the depth d of a cylindrical surface 12b parallel to the optical axis of each ring zone 12a is substantially constant. The base lens surface of the peripheral convex Fresnel lens part 12 is the central convex lens part 1
Assuming that the surface has the same radius of curvature as that of No. 1 and the depth d is constant, the pitch of each annular zone 12a becomes narrower toward the periphery. In the conventional Fresnel lens, the pitch of each orbicular zone 12a is constant, and therefore, the depth d becomes deeper toward the periphery, but when the depth d is made constant in this way, the minimum thickness can be secured. Easy. In FIG. 3, the peripheral Fresnel lens portion 12 is provided only on one surface of the light distribution lens 10.

[0010] Further, as shown in FIG.
The minimum thickness t can be increased and the strength can be increased by varying the pitch of the front and rear orbital zones 12a so that the position of the cylindrical surface 12b parallel to the optical axis of 2a does not match in front view. Cylindrical surface 12 parallel to the optical axis of front and back annular zones 12a
When the positions of b are matched in a front view, the minimum thickness t ′ is t
Smaller (t> t ′). 3 and 4 show:
A fixing surface (printing surface) 13 for fixing to the camera body is further drawn outside the peripheral Fresnel lens portion 12.
1 and 2 do not illustrate this fixed surface.

The center convex lens portion 11 and the peripheral convex Fresnel lens portion 12 can be formed from base surfaces having the same radius of curvature or different base radii depending on required light distribution characteristics.

The stroboscopic light distribution lens 10 is made of a molded product of a synthetic resin material, and the radius of curvature can be set arbitrarily. Light distribution lens 10 for this strobe
Is applied to a zoom strobe device, the exit angle changes as the incident angle to the central convex lens portion 11 and the peripheral convex Fresnel lens portion 12 changes, so the light distribution characteristics in each state are taken into consideration. Thus, these radii of curvature can be determined. Of course, an aspherical surface can also be used.

FIG. 5 shows an embodiment in which the present stroboscopic light distribution lens 10 is applied to a zoom strobe device of a zoom compact camera. The light distribution lens 10 is fixed to a camera body (not shown). Behind the light distribution lens 10, a light emitter unit 14 having a light emitter (light emitting tube) 14a and a reflector umbrella 14b is located. It is guided movably in the axial direction. The zoom photographing lens 20 is provided with a zoom gear 21 that is rotatable around the optical axis of the zoom photographing lens 20 and that rotates during a zoom operation. A rack 24 of a cam plate 23 meshes with the zoom gear 21. The cam plate 23 is movably supported in the direction of the rack 24. The cam plate 23 has a cam groove 25, and the light emitting unit 14
, A follower pin (not shown) provided integrally therewith is fitted. Therefore, when the zoom gear 21 rotates in accordance with the zooming operation of the zoom photographing lens, the cam plate 23 moves to move the light emitting unit 14 in the optical axis direction of the light distribution lens 10, and the irradiation angle is set to the focal length of the photographing lens. Vary accordingly. That is, when the distance between the strobe light distribution lens 10 and the light emitting unit 14 is changed, when the distance is small, the refractive power of the light distribution lens 10 becomes small, and a large irradiation angle is obtained. The refractive power of the optical lens 10 increases, and a small irradiation angle can be obtained. In particular, in the telephoto state of the photographing lens which needs to irradiate the irradiation light up to a long distance, the refraction of the central convex lens portion 11 is important, and since the central convex lens portion 11 has no light amount loss due to the cylindrical surface 12b, Preferred power can be obtained as a whole. On the other hand, in the wide-angle state of the photographing lens, a large irradiation angle is prioritized, so that the light amount loss due to the cylindrical surface 12b of the peripheral convex Fresnel lens portion 12 does not matter much.

The radius of curvature of the central convex lens portion 11 and the peripheral convex Fresnel lens portion 12 of the stroboscopic light distribution lens 10 can be freely set so as to obtain necessary light distribution characteristics as described above. The peripheral convex Fresnel lens portion 12 of the strobe light distribution lens 10 is connected to the lead wire 1 of the arc tube 14a.
7 and its internal parts such as soldered parts are concealed.

FIG. 6 shows the light distribution lens 10 (solid line) of the central convex lens peripheral edge Fresnel lens according to the present invention and the conventional full-convex lens type light distribution lens (dashed line) in a telephoto state (140 mm focal length for 35 mm camera). It is the graph which showed an example of the light distribution characteristic in center guide number: 17). According to the light distribution lens 10 of the present invention, almost the same guide number and light distribution characteristics as those of the conventional full convex lens type can be obtained, and the inside of the strobe can be blocked by the peripheral convex Fresnel lens portion 12. The effect is obtained. Note that the two lenses in FIG. 6 have different radii of curvature so that the guide numbers at the center are substantially equal.

[0016]

According to the present invention, it is possible to obtain a light distribution lens for a strobe which does not increase the thickness as much as a convex lens, has a small loss of light amount due to the circular surface of the annular zone of the Fresnel lens, and has an effect of concealing built-in components. Can be. According to the zoom strobe device using this light distribution lens, it is possible to obtain a degree of freedom in setting light distribution characteristics from a large irradiation angle to a small irradiation angle. Is maintained, and the irradiation light can reach a long distance.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of a strobe light distribution lens according to the present invention.

FIG. 2 is a sectional view taken along the line II-II in FIG.

FIG. 3 is an enlarged sectional view of a Fresnel lens part of the light distribution lens of FIG. 1;

FIG. 4 is an enlarged sectional view of another embodiment.

FIG. 5 is a perspective view showing an embodiment of a zoom strobe device using the light distribution lens of FIG. 1;

FIG. 6 is a diagram illustrating an example of light distribution characteristics of the zoom strobe device of FIG. 5;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Light distribution lens for strobes 11 Center convex lens portion 12 Peripheral convex Fresnel lens portion 12a Ring zone 12b Cylindrical surface 14 Light emitting unit 20 Zoom shooting lens 21 Zoom gear 23 Cam plate 25 Cam groove

Claims (5)

[Claims] 1. A stroboscopic light distribution lens which is located in front of a light emitting device of a strobe and condenses light, wherein a central convex portion of at least one of the front and rear surfaces is a convex convex lens portion, and a periphery of the central convex lens portion is a peripheral convex Fresnel. A light distribution lens for a strobe characterized by having a lens portion. 2. The method according to claim 1, further comprising a central convex lens portion and a peripheral convex Fresnel lens portion on both front and rear surfaces, wherein the front and rear peripheral Fresnel lens surfaces are parallel to the optical axes of the front and rear annular zones. Light distribution lenses for strobe light whose pitches are different from each other so that the cylindrical surface positions do not match in front view. 3. The strobe light distribution lens according to claim 1, wherein the peripheral Fresnel lens has a substantially constant depth of each annular zone. 4. The strobe light distribution lens according to claim 1, wherein the radius of curvature of the central convex lens portion and the radius of curvature of the peripheral Fresnel lens surface are different. 5. A zoom system comprising: a light emitting unit; a light distribution lens positioned in front of the light emitting unit to collect light; and zoom means for changing an interval between the light emitting unit and the light distribution lens. A flash strobe device, wherein at least one central part of the front and back surfaces of the light distribution lens is a convex lens surface, and the periphery of the central convex lens portion is a peripheral convex Fresnel lens portion.