JPH02124547A - Variable stroboscope for illuminating angle - Google Patents

Abstract

PURPOSE:To improve an illuminating efficiency by simultaneously moving a Fresnel lens and a light source for changing an illuminating angle. CONSTITUTION:As a planar cam 14 is displaced in an oblique and lower left direction, force is applied to the front of the light source 12 by the groove 15 of the planar cam 14 and pushed forward along the groove 17 of a guide 16. Here, the Fresnel lens 11 whose part engaged with the groove 18 of the planar cam 14 is retreated backward together as the planar cam 14 is retreated. As a result, when the planar cam 14 reaches a bottom position, the light source 12 moves 12b 12a; moreover, the Fresnel lens 11 moves 11b 11a respectively. Therefore, the illuminating efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Application of the Invention) The present invention relates to a variable illumination angle strobe installed in a camera equipped with a zoom lens, a still video camera, or the like.

(Background of the invention) In the conventional variable irradiation strobe,
As disclosed in No. 330 and the like, a Fresnel lens 1a (not shown in FIG. 7) is generally moved to a position 1b to change its irradiation angle. Also, special public service in 1986-
As disclosed in No. 51453, the state of FIG. 8(a) is changed to the state of FIG. 8(b), that is, the light source 2a is changed to the state of FIG.
It has also been proposed to change the irradiation angle by moving the reflective member 4a, which forms part of the reflective umbrella behind the light source 2a, to the position 4b.

However, in these conventional strobes, in the case of the former method, the irradiation angle was changed only by moving the Fresnel lens located at the front, which caused the following problems.

1) Increase in size due to the movement space of the Fresnel lens 2) Increase in the size of the Fresnel lens itself.In the latter case, the light source and the light source and reflecting member were moved to change the irradiation angle, resulting in the following problems. there were.

1) Since the amount of movement of the light source is determined by the size of the reflector, there is little change in the irradiation angle due to changes in reflection conditions. Conversely, if the amount of movement of the light source is increased, the entire strobe device will become larger. Furthermore, as is clear from Fig. 10, changes in the irradiation angle due to the positional relationship between the light source and the Fresnel lens differ from the change in the irradiation angle from the light source itself to the mirror image of the light source (2a,
Since the illumination angle change from 2b') behaves in the opposite way,
ineffective.

2) If the light source is a straight tube type such as a cannon tube, generally the θ! ′〉θ1゜02 ′〉θ2. θ,′
〉 θ3, the light reflected by the side reflector 5 is considerably smaller than the light used directly from the aperture of the reflector, and even if the reflection conditions are changed depending on the amount of movement of the light source, the illumination angle will not change. Changes (longitudinal) are small.

(Object of the Invention) An object of the present invention is to provide a variable irradiation angle strobe that can solve the above-mentioned problems, improve irradiation efficiency, and achieve miniaturization of the device.

(Features of the Invention) In order to achieve the above object, the present invention provides an irradiation angle setting means for moving either one of the light source and the reflector in a direction that reduces the distance in the optical axis direction, and moving the Fresnel lens forward. The illumination angle is variable by moving both the light source and the Fresnel lens, or the reflector and the Fresnel lens.

(Embodiments of the Invention) Hereinafter, the present invention will be described in detail based on illustrated embodiments.

FIG. 1 is a perspective view showing the main parts of the present invention. In this figure, 11 is a Fresnel lens, 12 is a straight tube type light source, ll'a is a wide-angle mode, and 1.1b is a telephoto mode. The position of the Fresnel lens is 12a when wide, 12b
indicates the position of the light source during telephoto mode. Also, 13 is a reflective umbrella.

Here, in this example, the focal length is 35 mm to 70 mm.
This shows a variable illumination angle strobe that has an illumination angle (irradiation range) that can correspond to the angle of view of a mm zoom lens.

FIGS. 2(a) and 2(b) are side views showing a mechanism for varying the irradiation angle.

As the plate cam 14 is displaced diagonally downward to the left in the figure, the light source 12 receives a forward force from the groove 15 of the plate cam 14 and is pushed forward along the groove 17 of the guide 16. At this time, the Fresnel lens 11, which is partially fitted into the groove 18 of the plate cam 14, moves backward in conjunction with the backward movement of the plate cam 14. As a result, the plate cam 14 is as shown in FIG. 2(b).
When reaching the lower position shown in , the light source 12 moves from 12b to 12a.
The Fresnel lens 11 moves from position llb to position lla.

In FIG. 3, the Fresnel lens 11 is a circular Fresnel lens with a focal length f on the object side, and a cylindrical Fresnel lens with a focal length f having refractive power only in the left and right directions on the light source side.

In addition, the eccentricity of the ellipse that determines the shape of the reflective umbrella 13 is K, the radius is R1, the depth is D, and the length, radius, and amount of movement of the light source 12 are,
β, r, HIIlt The amount of movement of the Fresnel lens 11 is Ff
If fl, then f = 1058 f, = 26.5 K = -0
,95R=3.72 β=16.0 2r
=3.5) (I11=0.825 FIIl=4.0
D=4.0 (unit: mm). At this time, the irradiation angle changes as follows.

Vertical: 30'' → 40' Horizontal: 45＠→ 62° This fully corresponds to the angle of view of the zoom lens.The amount of movement FIN of the Fresnel lens 11 here is about half that of the conventional one with this specification. It is.

Based on the empirical rules leading up to the above numerical settings, it is desirable that each value be within the following range in order to be compatible with the zoom lens.

f z < f ・・・・・・■20≦f
2≦30 ・・・・・・■-1≦≦0.5
......■0.1D≦H,≦D-2r
−■ ff＜3.6D ・・・・・・■D＜
For R<2R...■ If f exceeds this lower limit, the balance between the left and right irradiation angles corresponding to the film size cannot be maintained.

Regarding (2), if f2 exceeds this lower limit, the refractive power will be too strong and the light will be diffused as shown in FIG. If f2 exceeds the upper limit, the refractive power will be weakened, the amount of movement of the Fresnel lens will increase, and the strobe as a whole will become larger.

Regarding (2), if K exceeds the lower limit, the illumination angle change due to the movement of the arc tube will be insufficient. If K exceeds the upper limit of ■, the light will be too diffused and will no longer correspond to the angle of view of the zoom lens.

Regarding (2), when H and n exceed the lower limit, the illumination angle change due to the movement of the arc tube is insufficient. If H exceeds the upper limit of ■, the amount of movement of the arc tube is too large and the arc tube protrudes from the opening of the reflector.

Regarding (2), if the temperature exceeds the upper limit, the light will be too diffused and cannot correspond to the angle of view of the zoom lens.

Regarding (2), when R exceeds the lower limit, the light goes too far inward as shown in FIG. 5(a), and the light is diffused.

Furthermore, when R exceeds the upper limit, the light is directed too far to the outside as shown in FIG. 5(b), and the light is diffused.

As described above, according to the above embodiment, the illumination efficiency of the variable illumination angle strobe is improved.

Next, other embodiments of the present invention will be described.

FIG. 6 shows a variable illumination angle strobe that uses a light source (point light source) 22 such as a miniature light bulb, and has an illumination angle compatible with a zoom lens with a focal length of 35 mm to 70 mm, similar to the embodiment described above. .

The shape of the reflector 23 is rotationally symmetrical with respect to the optical axis in the side view of the above embodiment, and f,, 52.4 f, = 26.5 K = -
0.95R=3.72 2r=3. OH,=0.9
Fm=2.5 D=4.0 (unit: mm). At this time, the irradiation angle changes as follows.

Vertical: 30° → 52° Horizontal: 386° → 70' This fully corresponds to the angle of view of a zoom lens with a focal length of 35 mm to 70 mm.

According to this embodiment, since the irradiation angle is changed by simultaneously moving the Fresnel lens and the light source, the irradiation efficiency is improved and it is possible to further downsize or adapt to the angle of view of a high-magnification zoom lens. can. In addition, the shape of the reflective umbrella, the amount of movement of the light source, the focal length of the Fresnel lens,
Since there are more factors that determine the irradiation angle, such as the amount of movement of the Fresnel lens, more detailed design becomes possible.

(Correspondence between the invention and the embodiments) In this embodiment, the cam plate 14 and the guide 16 correspond to the irradiation angle setting means of the present invention.

(Modified example) In this embodiment, the illumination angle is variable by moving the Fresnel lens and the light source, but the configuration is not limited to this. When narrowing the illumination angle, the light source is fixed and the reflection A similar effect can be obtained by moving the umbrella forward and simultaneously moving the Fresnel lens forward so that the distance from the reflective umbrella increases.

Also, when narrowing the beam angle, the same effect can be obtained by fixing the Fresnel lens and moving the reflector backwards, and at the same time moving the light source backwards to shorten the distance between the reflector and the light source. It will be done.

(Effects of the Invention) As explained above, according to the present invention, the illumination angle setting means moves either one of the light source and the reflector in a direction that reduces the distance in the optical axis direction, and moves the Fresnel lens forward. Since the irradiation angle can be varied by moving both the light source and the Fresnel lens, or the reflector and the Fresnel lens, it is possible to improve the irradiation efficiency and downsize the device. Become.

[Brief explanation of drawings]

Fig. 1 is a perspective view showing an embodiment of the present invention, Fig. 2(a)
(b) is a side view showing the mechanism for varying the irradiation angle, Figures 3 (a) and (b) A are top views and side sectional views showing the positional relationship of each component, and Figure 4 is the same Fresnel view. Diagrams showing the state of light diffusion when the refractive power of the lens is too strong, Figure 5 (a) and (b) are the same <R<D, R>D
FIG. 6 is a perspective view showing another embodiment of the present invention, and FIGS. 7 to 10 explain problems with conventional variable illumination angle strobes. FIG. 11...Fresnel lens, 12...Light source, 13...Reflector, 14...Cam plate, 16...Guide, 21... ... Fresnel lens, 22 ... light source, 23 ... reflective umbrella.

Claims (1)

[Claims] (1) In a variable illumination angle strobe equipped with a light source, a reflector, and a Fresnel lens placed in front of the light source, when narrowing the illumination angle, the distance between the light source and the reflector in the optical axis direction is shortened. 1. A variable illumination angle strobe characterized by comprising an illumination angle setting means for moving one of the Fresnel lenses in a direction and moving the Fresnel lens forward.