JPS62211627A - Stroboscopic flashgun - Google Patents

Abstract

PURPOSE:To miniaturize a stroboscopic flashgun small in size by forming a shape of a reflector and a shape of a condensing convex Fresnel lens to specific shapes. CONSTITUTION:A vertical section of a reflector 3 is formed in an elliptical shape, and in front of the opening part, a convex Fresnel lens 4 is provided so that its groove 4a is placed at the outside of the reflector 3. A small-sized and efficient stroboscopic flashgun whose size Dp is small, and also which has a condensing operation for scarcely generating vignetting is constituted by forming it so as to have a specific relation of 1.5<f<3D, 0.4<K<1, D/10<R<D/2, 0.4D<Dp<1.2D, and D/20<Fp<D/3, among a focal distance (f) of the lens 4, a cone constant K for showing an elliptical shape of the reflector, a radius of curvature R of a reference spherical surface, depth Dp of the reflector 3, and an interval Fp between a focal position and the top.

Description

DETAILED DESCRIPTION OF THE INVENTION TECHNICAL FIELD The present invention relates to a strobe flash device used in cameras and the like, and particularly to a strobe flash device that is miniaturized.

"Prior art and its problems" Strobe flash devices generally have a semi-cylindrical shape with an elliptical cross section expressed by the formula x=a(I-JI-(y2/b')), as shown in FIG. reflector] and a cylindrical strobe flash tube 2 disposed at the focal point of the reflector 1. a indicates the length of the major axis of the ellipse, and b indicates the length of the minor axis of the ellipse. In such a strobe flash device, as shown in FIG. 10, the angle θ1 of the light beam directly emitted from the strobe flash tube 2 at the front opening 1a of the strobe reflector 1,
It is necessary to make the angle θ2 of the light beam reflected by the strobe reflector 1 and then irradiated equal to the irradiation angle e.

Therefore, is the depth of the strobe reflector the length of the major axis of the ellipse? ! a
It is necessary to make the aperture diameter D1. in the strobe reflector 1 equal to D1. must be twice the minor axis of the ellipse. From these facts, the following coefficient formula % formula % Here, for example, at the irradiation angle θ・25°, the aperture diameter D = 12 m
To obtain a strobe flasher of m, it is sufficient to substitute these values into the above formula. That is, the major axis length a, which determines the elliptical shape of the strobe reflector 1, is 14. The length of the short axis is 97 mm, and the short axis length b is 6 mm. Here, the depth of the strobe reflector 1, that is, the major axis length a is 14. l97m
m, which means that it must be made quite deep. That is, as can be seen from this example and the above formula, in a conventional strobe flash device, in order to narrow the illumination angle θ,
The depth of the strobe reflector 1, that is, the long axis length a, must be increased, which hinders miniaturization.

"Object of the Invention" An object of the present invention is to miniaturize a strobe flash device. In particular, the purpose of this invention is to reduce the depth dimension of a reflector in a type of strobe flash device in which a convex Fresnel lens is attached to the front surface of the reflector.

"Summary of the Invention" The present invention provides that when the irradiation angle range is ±15° to ±45° and the refractive index of the convex Fresnel lens is in the range of 1.4 to 2.0, the focal length of the convex Fresnel lens is f, conic constant K representing the elliptical shape of the reflector, radius of curvature of the reference sphere representing the elliptical shape of the reflector, depth of the reflector? ! Op, the ideal value for the distance Fp between the apex of the reflector and the focal point position is determined by empirical rules or calculations, and the acceptable range for this ideal value as a strobe flash device is studied and completed. It is something that That is, the present invention provides the above f
, R10p and F9 are in the ranges of the following formulas Φ, ■, ■, ■ and 0, respectively.

1.5<f<30
■0.4(K<I
■D/10<R<D/2
■0.4D
<Dp<1.20 ■0/20<Fp
<O/3 ■“
Embodiments of the Invention" The reason why the above range is optimal will be explained below using drawings and mathematical formulas.

Figures 1 and 2 show examples of the shape of the strobe flash device according to the present invention, in which the longitudinal section is x・y"/RCI◆(+-(+◆K)y2/R')"2
] (where K is a conic constant and day is the radius of curvature of the reference sphere) A semi-cylindrical reflector 3 with a constant cross section represented by an ellipse has a convex Fresnel lens 4 located in its front opening 3a,
A cylindrical strobe flash tube (xenon flash tube) 5 is located at the internal focal point. The convex Fresnel lens 4 has a convex Fresnel groove 4a formed on its front surface, that is, the surface opposite to the strobe flash tube 5. This lens 4 is
Convex Fresnel groove 4a! Compared to a convex Fresnel lens of the same type formed on the side of the strobe flash tube 5, there is less vignetting and a higher light-gathering effect.The vignetting in a convex Fresnel lens refers to the part that does not contribute to the light-gathering effect; As shown in FIG. 9(A) and (8), the convex Fresnel groove 4 is formed on the opposite side (subject side) of the flash tube 5 (see FIG. 9(A)). The one with the convex Fresnel groove 4a
It can be seen that there is less vignetting than in the case where the strobe light is formed on the side of the strobe flash tube 5 (see ce' in the same figure), and as a result, the light gathering effect is higher.

With the above configuration, the vertical illumination angle of the strobe can be set to θ,
By setting the refractive index of the convex Fresnel lens to n, it is possible to create a strobe flash device in which the depth Op of the reflector 3 is significantly shallower than that of the conventional one.

Next (Fl is determined from the focal length f of the convex Fresnel lens 4, the depth Op of the reflector 3, the distance Fp between the apex of the reflector 3 and the focal point position, and the coefficients representing the cross-sectional shape of the reflector 3.

First, it is assumed that the focal path w1f of the convex Fresnel lens is within the range of the following equation with respect to the aperture diameter of the reflector 3.

1.50 < f < 30 ■ If the focal path 111f of the convex Fresnel lens is shorter than this range, vignetting at the end of the convex Fresnel lens will increase, which is undesirable. If Mf is long, the depth Dρ of the reflector 3 will become large, and the effect of miniaturization will be small.

In the calculations below, unless otherwise specified, f=20
Calculate as follows.

Next, we will find the ideal tolerance range for the depth Op of the reflector 3, the distance Fp between the apex of the reflector 3 and the focal point position, and the coefficient representing the cross-sectional shape of the reflector 3. First, the basic formulas for calculating these values will be explained.

As shown in FIG. 3, when the angle of the prism 4a is σ, the refractive index is n, and the angle of incidence with respect to the first surface is 01, the deflection angle ε of the light beam is expressed by the following equation.

E=θI+5in-'[n5in(a-5in-'(
sine I /n))]-a...■ First, the prism angle σ at the end of the convex Fresnel lens is determined from the focal path Mf of the convex Fresnel lens. As shown in FIG. 4, the deflection angle 6 of the light beam at the end of the convex Fresnel lens is determined by the following equation.

6 = tan-'CD/2f) Therefore, by substituting 81·0 and ε=6 into the above equation 0 and solving for σ, the following equation is obtained.

σ=5in-'(sin 5/Jn"-2nco
s6 + I)... ■This formula determines the prism angle σ at the end of the convex Fresnel lens.0 order As shown in Figure 5, the light emitted from the focal point F of the reflector 3 and passing only through the convex Fresnel lens The angle ψ at which the exit angle ε1 of the light ray at the end of the convex Fresnel lens, which is irradiated onto the subject, is equal to the irradiation angle θ is determined. In the above formula 0, ε=medium/small-1=small-e, θ
Substituting 1=small, we get φ-θ=φ+5in-'[n5in(σ-5in-'(
sinφ/n)])-σ, rearranging this, θ= a-5in-'[n5in(a-sin-'
(sfnφ/n)) ] and solving this for φ yields the following equation.

φ = 5in-' [n5in(σ-5in - Suga(
sin(σ -8)/n)) Go...■ Next, in Fig. 5, light is emitted from the focal point F of the reflector 3, reflected by the reflector 3, refracted by the convex Fresnel lens 4, and directed toward the subject. The angle ρ at which the emission angle ε2 of the ray of light at the end of the convex Fresnel lens is equal to the irradiation angle θ is determined. The angle ρ is the angle of incidence of the light beam reflected by the reflector 3 onto the convex Fresnel lens 4. In the above equation 0, ε=ε2=θ, θ1
By substituting =p, θ=G) ◆5in-'(nsin(a -5tn-
'(sin o /n)))-σ...■ Transforming the 0 formula, f(ρ)・2ρ-σ-θ + 5in-'(nsin (σ-5in-' (si
np /n))=■, and find ρ such that f(ρ)=0 using the so-called midpoint method. The midpoint method is a method of finding the roots of a complex equation by repeated calculations, and can be easily performed using a combi coater or the like. For example, initial value ρ1=O
”, ρ2=90°, and error 6=0.001°.

A flowchart of this calculation is shown in Figure 8.A brief explanation of the flowchart shown in Figure 8 is as follows.

That is, first, the initial values p1 and ρ2 of ρ are set to 0°,
Assuming 90°, f(ρ1) and f(ρ2) based on this value
and calculate their product f(pl)・f(p2)
is always negative, that is, each f(ρ1), f(
Calculate by replacing the value of (ρ1 + ρ2)/2 with ρ1 or ρ2 one after another so that ρ2) approaches O, and calculate Iρ2-ρ1
Calculate until the value of 1 becomes 6 or less, and then calculate ρ
The value of 1 is found as ρ. ρ obtained in this way becomes an approximate solution to Equation 0.

Next, the shape of the reflector 3 is determined from φ and ρ determined in this manner.

In FIG. 6, first, the major axis length a of the ellipse representing the shape of the reflector 3 is determined. From the properties of an ellipse, FP+ PF'=F
P'◆P'F=2a. Therefore, FP+ PF'=
D/2sinφ+D/2sinp = 2a holds, therefore, a = (D/4XI/sinφ+I/5inp)
"""■Also, find the length b of the minor axis of the ellipse that represents the shape of the reflector 3. According to Figure 6, 2ae・D/2tan 10/2 sinρ holds, so e = (D/4aXI /lanφ◆I/lanρ)
・・・・・・■ However, here e is eccentricity e =
J a”-b2/a.

By substituting (1) and (2), b=aJI-C2... (2) Substituting a and b obtained in this manner into the ellipse equation, the shape of the reflector 3 can be determined. The equation of an ellipse can be expressed as follows.

x=a C1-Jl-y2/b') -”・■Also,
Conic constant = -C2, radius of curvature of reference sphere R = b 2/
From the relationship of a, it can also be expressed as the formula for conic curvature6, i.e., x = (y2/R)/[I+ (I-(1+ K)
y2/R2)]""...■ Also, the distance Fp between the apex of the reflector 3 and the focal point is Fp=a(
1-e), the depth Op of the reflector 3 is Dp=Fp+D/
It can be determined using the formula 2tanφ.

By performing the above calculations, we can calculate the focal length Mf and Coefficients representing the shape of the reflector 3 (conic constant K, radius of curvature of the reference sphere), depth Op of the reflector 3
, the distance Fp between the apex of the reflector 3 and the focal point can be easily determined.

Next, the above-mentioned calculation is performed by substituting the following values as input data, which shows a specific example of calculation.

Aperture diameter of longitudinal section of reflector D = 12 Vertical illumination angle θ; 25° Refractive index of convex Fresnel lens n = 1.4913 If the focal path of the convex Fresnel lens is Jlf 20 24, then The calculation result is obtained.

Conic constant K = -0,85922 Radius of curvature of reference sphere = 2.68777 Depth of reflector Dp = 8.782 Distance between apex of reflector and focal point Fp-1,384 Similarly, 0 =
12, when θ=33.5° and n=1.49136, we get the following result.

As f=20=24, K=-0,711558,
Fl = 3.569010ρ = 7.054, F9 =
Same as 1.936, 1ko0=12, e=15°, n=
In the case of 1.49136, the following result is obtained.

f=213=24e, K=-0,99010, P
I = 1.547650p = 12.099, Fp =
Similarly to 0.776, D=+2, θ=45°, n=1
．． In the case of 49136, the following result is obtained.

f = 20 = 24, K = -0,46357, day =
4.79809Dρ=5.354, Fp=2.8
55 A comparison table between the depth 0ρ of the reflector in the calculation results according to the present example described above and the depth 0ρ° of the reflector according to the conventional example is shown below.

From the above calculation results, the following becomes clear.

In other words, if the range of the vertical illumination angle of a typical strobe flash is ±15° to ±45°, the refractive index of the convex Fresnel lens is in the range of 1.4 to 2, and the aperture diameter of the longitudinal section is On the other hand, if the following conditions are met, the depth dimension of the reflector can be reduced to approximately half that of the conventional reflector.

Focal path of convex Fresnel lens M f 1.50<f<3
0...■Coefficient K (conical constant) representing the shape of the reflector 0.4<<1...■Coefficient representing the shape of the reflector (radius of curvature of the reference sphere) O/10<R<D /2 -・
・■Reflector depth Dp O, 4D<Dp<1.20
...■ Distance Fp between the apex of the reflector and the focal point
D/20<Fp<D/3...■ In the above embodiment, the convex Fresnel groove of the convex Fresnel lens is located on the opposite side of the strobe flash tube, but the convex Fresnel groove of the convex Fresnel lens Even if the groove is on the strobe flash tube side or on both sides, the shape of the reflector can be determined in the same way. In that case, if the values of f, K, R, Op, and Fp are also within the range of the above-mentioned 0 to 0 formula, the depth dimension of the conventional single strobe flash device can be reduced. are similar.

In FIG. 7, a semi-cylindrical housing part 3a centered on the axis X and having a radius d approximately equal to the radius of the strobe flash tube 5 is formed at the apex a of the reflector 3, and inside this semi-cylindrical housing part 3a. The present invention is applied to a strobe flash device of a type in which the rear half of the strobe flash tube 5 is housed in the coefficient Fp, Op and the shape of the reflector 3 shown in FIG. Define as in the example. According to this example, the focal point F7&
Reflector 3 can be brought close to the apex a of the reflector.
This becomes possible by further downsizing. Moreover, since the light emission center of the strobe flash tube 5 is located in front of the reflecting surface of the reflector 3, no effect is caused in the light emission efficiency.

"Effects of the Invention" As described above, the present invention provides f of a convex Fresnel lens constituting a strobe flash device, a conical constant K representing the shape of a reflector,
The radius of curvature R of the reference spherical surface that represents the shape of the reflector, the depth Op of the reflector, and the distance Fl between the apex of the reflector and the focal point position were set to the optimal ranges, so the dimensions in the depth direction of the reflector were It can be made smaller compared to the device. Furthermore, the irradiation efficiency is the same as that of conventional strobe flashers, making it possible to create a very compact and efficient strobe flasher.

[Brief explanation of drawings]

Fig. 1 is a sectional view taken along the line I-I in Fig. 2 showing an embodiment of the strobe flash device of the present invention, Fig. 2 is a front view thereof, and Fig. 3 is an optical path diagram showing the refraction state of the convex Fresnel lens. , Fig. 4 is a longitudinal cross-sectional view of the convex Fresnel lens, and Fig. 5 is an optical path diagram for determining the prism angle at the end of the convex Fresnel lens. Fig. 6 is an explanatory diagram for determining the major axis length and short axis length forming the ellipse of the reflector based on the properties of the ellipse. Figure 8 is a cross-sectional view showing an embodiment of 811 of the present invention, Figure 8 is a flowchart of a calculation formula for determining the angle of incidence at the end of the convex Fresnel lens of a ray of light passing through the reflector and convex Fresnel lens, Figure 9 (A) , (8) is a cross-sectional view showing vignetting in a convex Fresnel lens, and FIG. 10 is a vertical cross-sectional view showing a conventional strobe flash device. 3...Reflector, 4...Convex Fresnel lens, 5...
Strobe flash, f...focal length, D...aperture diameter,
K...Conical constant representing the cross-sectional shape of the reflector, day...
The radius of curvature of the reference sphere representing the cross-sectional shape of the reflector, Op.
... Depth of reflector, FI) - ... Distance between the apex of the reflector and the focal point. Figure 2 Figure 3 Figure 4 Figure 5 Procedure Neho Correction 1 ((Spontaneous) April 18, 1988 Patent Application No. 55742 2, Name of the invention Strobe flash device 3, Person making the correction Relationship to the incident Patent applicant address 2-36-9 Maeno-cho, Itabashi-ku, Tokyo Name (
052) Asahi Optical Industry Co., Ltd. Representative: Toru Matsumoto 4, Agent address: 3-1゜5, Yonban-cho, Chiyoda-ku, Tokyo 102
Date of amendment order 6, scope of claims of the specification to be amended and detailed description of the invention column 7
, Contents of the amendment (1) The claims of the specification are amended as shown in the attached sheet. (2) rO, 4 on page 5, line 8 and page 14, last line of the specification
<K<l J Toy') Note @@ r-1<K<-〇, 4
J Correct. (3) The entry rsinρJ on page 11, line 12 of the specificationffi! is corrected as "r tan ρ". Written patent claims stating the above amended and revised claims (1) Longitudinal cross section x = y2/day [++ (+- (to 1◆) y2
/R2) A semi-cylindrical reflector represented by an ellipse in "2", a cylindrical strobe flash tube located at the focal point of this reflector, and a convex Fresnel lens located at the front opening of the reflector. The aperture diameter in the longitudinal section of the reflector is D, and the refractive index n of the convex Fresnel lens is n=1.4.
~2.0, when the irradiation angle range is θ = ±15 @ ~ ±45°, the focal path Mf of the convex Fresnel lens, the conical constant K representing the elliptical shape of the reflector, and the elliptical shape of the reflector. The radius of curvature of the reference spherical surface representing the mold, the depth Op of the reflector, and the distance 1"p between the apex of the reflector and the focal point are:
A strobe flash device characterized in that it falls within the ranges of the following formulas (1), (2), (2), (2), and (0), respectively. 1.5<f<30 ■=1<to<-0,4■ D/10<R<D/2 ■0.4
D<Dp<1.20 ■D/20<
Fp<O/3 (2. In claim 1, the convex Fresnel lens has a convex Fresnel groove formed only on the surface opposite to the strobe flash tube lJ). (3) In claim 1 or 2, the reflector has a semi-cylindrical storage portion formed at its apex,
A strobe flash device in which the inner part of the strobe flash tube is stored inside this semi-cylindrical housing.

Claims (3)

[Claims] (1) Vertical section x=y^2/R[1+{1-(1+K)y
^2/R^2^^1^/^2] A semi-cylindrical reflector represented by an ellipse, a cylindrical strobe flash tube located at the focal point of this reflector, and a front opening of the reflector. The aperture diameter in the longitudinal section of the reflector is D, and the refractive index of the convex Fresnel lens is n.
n=1.4~2.0, irradiation angle range θ=±15°~
In the case of ±45°, the focal length f of the convex Fresnel lens, the conic constant K representing the elliptical shape of the reflector, the radius of curvature R of the reference sphere representing the elliptical shape of the reflector, and the depth of the reflector Dp and the distance Fp between the apex of the reflector and the focal point position are respectively expressed as follows [1] [2] [3]
[4] A strobe flash device that is within the range of formulas [5] and [5]. 1.5<f<3D[1] 0.4<K<1[2] D/10<R<D/2[3] 0.4D<Dp<1.2D[4] D/20<Fp< D/3 [5] (2) The strobe flash device according to claim 1, wherein the convex Fresnel lens has a convex Fresnel groove formed only on the surface opposite to the strobe flash tube. (3) In claim 1 or 2, the reflector has a semi-cylindrical storage portion formed at its apex,
A strobe flash device in which the inner part of the strobe flash tube is stored inside this semi-cylindrical housing.