JPH02294614A - Optical parts for uniforming luminous flux - Google Patents

Abstract

PURPOSE:To uniform luminous flux by bending the optical axis of luminous flux which is made incident on an incidence surface perpendicularly by a transparent plate by a specific angle and restoring the luminous flux to luminous flux parallel to the original axis by a transparent plate which is arranged at a constant distance. CONSTITUTION:The light beam which is made incident on the +theta surface is changed in direction by refraction by the angle alpha satisfying an equation I and becomes a light beam having an angle beta, satisfying an equation II, to the X axis by refraction when exiting from the transparent plate 1. Further, when the light beam enters the transparent plate 2, the angle to the X axis becomes alphaagain and the light beam reaches a projection surface 23. The distance Q that the light beam travels in a Y-axial direction until it reaches the projection surface 23 is shown by an equation III eventually. This light beam is projected from the +theta surface, so the light beam which is made incident on the +theta surface and exits from the +theta surface and the light beam which is made incident on a -theta surface and exits from the -theta surface similarly exits shifting in parallel by Q and -Q respectively. Consequently, the high-efficient uniform luminous flux is obtained.

Description

Detailed Description of the Invention [Industrial Application Field] The present invention provides a uniform and unidirectional light beam required for the light incident portion of an optical fiber light guide, the illumination light source of a slide projector, etc. Regarding optical components for obtaining.

[Prior art] Line light sources used in defect inspection equipment for sheet materials,
Optical fiber light guides are used as cold light sources for LCD backlights in LCD printers, but in order to obtain high-quality illumination without uneven illuminance, these light incident areas must be diffused to uniformize the incident light. Devices using plates or optical fibers and light guides as described in Japanese Patent Application No. 63-106779 have been devised.

Additionally, an optical system using a relay condenser is generally used in the light source section of a slide projector to prevent uneven brightness throughout the projected image.

[Problems to be Solved by the Invention] The characteristics required of these light source sections or light source uniformizing means are as follows.

(1) The amount of light is uniform throughout.

(2) High efficiency.

Furthermore, considering cost and practicality, (3) Easy to design and produce.

(4) Small size and does not take up much space.

Children are important.

The method using the above-mentioned diffusion plate and the patent application No. 1067-1983
The method using optical fibers and light guides in No. 79 uses reflective curved surfaces and lenses to create a directional light beam, which is passed through a homogenizing component to remove brightness irregularities, but the former uses a diffuser. The angle at which the light rays are scattered by the plate is large;
The efficiency is extremely low because the beam properties of the light are impaired and the light that does not fit within the aperture angle of the optical fiber becomes a loss. on the other hand,
The latter has good uniformity performance and is efficient without impairing the beam properties of light, but it is difficult to miniaturize, and the random mixing method is not easy to mass-produce while maintaining quality.

Furthermore, the optical system using the relay condenser described above has good uniformity performance and is not so bad in efficiency, but it requires careful design and adjustment of the bulb, reflector, condenser lens, etc., and requires advanced technology. is required. Therefore, within the scope of the prior art, it is difficult to realize an optical system that simultaneously satisfies (1) to (4).

[Means for Solving the Problems] In view of the problems of the prior art described above, an object of the present invention is to provide an optical component that can be miniaturized and can uniformize the luminous flux with high efficiency.

In order to achieve the above object, the optical component for uniformizing the light flux of the present invention is a rectangular piece in which one side is flat and the other side has a plurality of prism units formed in a stripe shape so that condition A is satisfied. A structural unit consisting of two transparent plates installed parallel to each other with the ridgelines of each prism unit parallel to each other and their flat sides facing each other, and constructed by overlapping at least one structural unit in parallel. It is characterized by being

(Condition A) The Y axis is parallel to each of the two perpendicular sides of the surface of the transparent plate,
If we take the Z-axis and the X-axis in the direction perpendicular to the surface, then the ridgeline of the prism unit is parallel to either the Y-axis or the Z-axis, and both sides of each prism unit are parallel to the X-axis, as shown below. [1] and [2] are formed so as to form an angle θ to −θ shown in equations.

However, δ is the smaller of the spread angle of the incident light beam or the spread angle (±δ) that can be used by a device that uses the output light beam, and δ<θ.

n: refractive index of the transparent body In order to efficiently uniformize the light beam with a normal light intensity distribution over a wide range, it is necessary to It is best to install a parallel reflective surface.

The present invention is similar to the method described in Japanese Patent Application No. 3779, 1983-10, and is used in a method of creating a directional light beam using a reflective curved surface or a lens, and removing brightness unevenness through a uniformizing component. This is a luminous flux equalizing component, which has the feature of uniformizing the amount of light without impairing the beam properties of the luminous flux, similar to the method described above.

This feature is important for obtaining high efficiency, even in fiber optic light guides or slide projectors.
Light rays that spread beyond the aperture angle of the optical system installed later are not used and are lost, so although the light source does not need to be parallel light, it is desirable that the light beam has unidirectionality. .

[Effect] The operation of the present invention will be explained with reference to FIG.

In FIG. 1, 2, 2 is a rectangular transparent plate constituting the structural unit 15 according to the present invention. Figure 1 shows structural unit 1
5 viewed from the axial direction parallel to the plane on which the prism unit 30 is formed, and this axis is defined as the Y-axis. It is assumed that the incident light enters from above the drawing along the X axis perpendicular to the plane on which the prism unit 30 is formed. Note that the Z-axis is taken in a direction perpendicular to the X-axis and the Y-axis.

First, consider a ray of light that is incident parallel to the X-axis. The plane that makes an angle of 10 with the X axis on the incident plane of the transparent plate l is the +θ plane (
In the output surface 23 of the transparent plate 2, the surface parallel to the +θ plane of the incident surface 20 is called the +θ plane. , the plane parallel to the -θ plane will be called the -θ plane. According to Snell's law, a ray incident on the +θ plane changes its direction by an angle α that satisfies the equation
It becomes a ray that forms an angle β with the axis that satisfies the equation (■). A detailed diagram of this angle α and angle β is shown in FIG. Further, when the light enters the transparent plate 2, the angle with the X axis becomes α again, and the light reaches the exit surface 23. In the end, the distance Q that the light ray moves in the Y-axis direction until it reaches the exit surface 23 is expressed by equation (2).

sxn(-10)=nsin(510+α)...■
．． π sinβ=nsina
．． ．． ．． ■Q” (d+ +dz) tana+
Ltan β... ■If this ray hits the +θ plane, the ray will return to the original state and be emitted as a ray parallel to the X-axis.

In this way, a light ray that enters the +θ plane and exits from the +θ plane, or similarly a light ray that enters the −θ plane and exits from the −θ plane, respectively, are deviated from parallel by Q−Q and exit. Here, θ is θ determined by the formula ■. If α is taken to be equal to , then α=10, and all light parallel to the X axis will pass through either of the two optical paths mentioned above.

In addition, if there is only the transparent body 1.2, the light that deviates from the transparent plate 2 due to a shift of Q or -Q in the Y-axis direction will be lost, but as shown in FIG. 1, both sides of the structural unit 15 In the case where a reflecting plate having a reflective surface is provided and the overall shape is a cylindrical light guiding path, the light is reflected by the reflecting surface 7 of the light guiding path and reaches the transparent plate 2. If the incident light entering the entrance surface 20 has the light amount distribution shown in FIG. 3, the output light will have the light amount distribution 8 (
(Due to light rays entering the +θ plane and exiting from the +θ plane)
, light intensity distribution 9 (due to rays incident on the -θ plane and emitted from the 10th plane), light intensity distribution 8° (due to rays incident on the +θ plane, reflected at surface 7, and then emitted from the 1θ plane) ,
By combining the light intensity distribution 9° (due to light rays incident on the 10 plane, reflected by the surface 7, and then emitted from the 10 theta plane), the light intensity distribution is made uniform as 1o. It is also clear that the parallelism of the incident light is not impaired. Reflective surface 7 of the light guide path
For the invention having a structure in which there is no light intensity distribution (the invention claimed in claim 1), the light intensity distribution 8° and the light intensity distribution 9 do not exist, so the light intensity distribution 10
'It will look like this.

As can be seen from FIG. 4, in the configuration in which a cylindrical light guide path whose inner surface is a reflective surface (invention according to claim 2) is formed,
In order to obtain a luminous flux that fills the entire width of the exit surface, the thickness of transparent plate 1 is dl, the thickness of transparent plate 2 is d2, and so that Q=W/4.
All you have to do is choose the distance L between them. If d+ and d2 are sufficiently small, it is sufficient.

If the incident light is perfectly parallel light, the light intensity distribution will have light intensity irregularities with a period T of each prism, but since the present invention realizes uniformity of the light flux with a slight spread angle, in reality By using light at a predetermined distance from the center, it is possible to eliminate unevenness in the amount of light with period T. If we set that distance as D, DOT/tan δ...
(2), where δ represents the smaller of the spread angle of the incident light beam or the spread angle that can be used by the device that utilizes the output light beam.

Therefore, the smaller the period T, the smaller the distance D can be, which is preferable for downsizing the device, but if it is too small, the roundness of the corners of the serrated surface will become thicker due to the limit of machining accuracy, so It is not preferable to make it smaller.

Furthermore, the fact that the spread angle δ is not O means that the value of the refraction angle α has a corresponding spread, so even if θ:00 is set, there are light ray components as shown in rays 11 to 13 in Figure 5. , although strictly speaking it is not as shown in Figure 4,
θ Aya θ. In this case, the effect shown in FIG. 4 can be obtained if the spread angle δ is not too large. In order for the equalization component of the present invention to work effectively, it is necessary that δ is smaller than θ, and a part of any prism unit 30 on the entrance surface 20 and the exit surface 23 is located at the top of the prism formed by the adjacent surface. Most of the light rays at large angles that are blocked by corners take optical paths as shown in FIGS. 11 to 13, so they are hardly effective light rays.

Next, we will explain how to find the valid range of the value of θ.
In Figure 6, the beam with a divergence angle δ at the incident plane has a refractive index n
If the spread angle becomes δ゛ when it enters the medium, then
δ゜ is expressed as follows in the first approximation.

sin(π/2−ψ)=nsin(π/2−φ). ．． C
OSψ=ncosφ. '． sinφdφ= n sinφdφ. '． dφ=
(sinψ/nsinφ)dψδ' = (sinψ
/nsinφ)δ In this case, the angle ψ is θ. If it is equal to , then φ=2ψ=20. Therefore, d$=dψ/ 2 n cosψ … oδ゜2 δ/
2n cos ψ... ■Next, consider the case where the angle ψ is increased by Δψ as shown in Figure 7. The bending angle φ゛ of parallel light can be calculated using the formula φ1 = φ + Δφ = φ + Δψ / 2 n cos ψ
=2ψ+Δψ/2ncos ψ =2(ψ+Δψ) 12-1/2 ncos
ψ) Δψ... O If Δψ is small, the spread angle within the medium is approximately equal to δ° in equation ■. If δ° is larger than the second term on the right side of equation O,
There is a ray component that satisfies φ゛=2(ψ+Δψ)...O within the spread angle. Since this component is the component that most efficiently exhibits the effects of the present invention, having this component is a condition for applying the present invention.

Therefore, δ'> (2-1/2 n cos ψ) Δψ.゜． Δψ
δ/(4ncosψ−1).゜． 80〈δ/(4nc
osθ. -1).゛． Δθkuδ/ (1+8n”)””
- O From this, the ■ formula is derived.

This inference was made regarding the spread angle of the incident light, but if δ is the effective spread angle of the output light, exactly the same result will be obtained by tracking the line of sight at the exit surface.

The characteristic feature of the present invention is that a light beam incident perpendicularly to the incident surface is divided into light beams whose optical axis is bent by an angle β, 1β by a transparent plate 1, and the light beam is By returning the beam parallel to the axis of , which also has the effect of expanding the luminous flux.

In FIG. 1, this effect is not affected by the period T (also called the prism width) of each prism unit 30 formed on the entrance surface 20 of the transparent plate 1 and the exit surface 23 of the transparent plate 2; This can be achieved as long as the angle .theta. formed by .theta. with the X axis is formed accurately. For example, as shown in FIG. 8, a configuration in which the pitch (period) T1 of the prism units 30 on the input surface 20 side is twice as long as the pitch T2 on the output surface 23 side can also be adopted. .

Furthermore, as shown in FIG. 9, the deviation ciy of each prism unit 30 between the entrance surface 20 and the exit surface 23 in the Y-axis direction is not a problem, and therefore there is an advantage that positioning accuracy of the transparent plates 1 and 2 is not required. be.

[Example] Next, the optical component for uniformizing the luminous flux of the present invention will be described in detail based on a specific example.

FIG. 10 shows a perspective view of an optical component for uniformizing the luminous flux of the present invention. FIG. 10(a) shows a configuration without a reflective surface, the first
FIG. 0(b) shows a configuration having a reflective surface. Reflective surfaces are also installed on the top and bottom sides of the component, which prevents light rays angled in the Z direction from leaking from the top and bottom surfaces and resulting in loss. As shown in both figures, a plurality of prism units 30 are formed extending in the Z-axis direction in the figures, and are formed in a striped shape. The transparent bodies 1 and 2 are each integrally molded by injection molding or the like, and are arranged in parallel with each other by the above-mentioned distance L.

In addition, in the present invention, the overall shape is important, and there is no need for it to be integrally molded, as shown in Fig. 11.
Align the semi-serrated transparent bodies 50 of the same shape and thickness d to a height H.
A transparent body having the same shape as that shown in FIG. 10 may be functionally equivalent. In this case, the adhesive must be transparent.

FIG. 12 shows an embodiment in which the waveforms of the overlapping emission surfaces are stacked such that they are shifted by 1/2 period (T/2). In the transparent body construction and 2, the serrated transparent bodies 50 stacked in this way do not need to have the same shape, and the prism unit 3
It may be a stack of layers having different periods T and phases of 0.

By stacking the serrated transparent bodies 1 having different periods T and phases of the prism units 30 in this manner, there is an effect that the light intensity unevenness with the period T described above is less likely to appear. In FIG. 12, if the plate thickness d is smaller than T, the equation (2) is replaced by the equation (2), and the equation (2) becomes the condition under which light intensity irregularities with a period T do not appear.

Dad/tan δ°...■ Here, δ° represents whichever is smaller of the spread angle in the plate thickness direction that can be used by a device that utilizes the incident light flux or the output light flux.

In addition, in the present invention, it is common to provide an air space between the transparent plates 1 and 2, which has the greatest effect of uniformizing the luminous flux, but in cases where it is not possible to arrange the transparent plates in the air, Instead, it is clear that the present invention can be constituted by arranging the structural unit according to the present invention in a medium (including vacuum) such as a gas or liquid having a refractive index smaller than the refractive index of the transparent plate 1.2. be. Figure 13 shows structural units (refractive index n l + n + > n 2) in a medium with refractive index n2.
It is a diagram showing a configuration in which the angle in Brism unit,
The refractive index and the like are selected and designed according to the refractive index of the front medium.

Furthermore, the structural unit shown in FIG. 1 has the effect of making the light amount uniform only in one axis direction, and when using a light source 43 in which the light amount is uneven only in one direction as shown in FIG. 14, this structural unit l5 However, if the non-uniformity of the light amount is a two-dimensional light source of 43 degrees, the structural unit 15 as shown in Fig. 15 may be used.
It is necessary to use two with their equalization axes perpendicular to each other to achieve uniformity.

Furthermore, the non-uniformity of the light amount of the light source is extremely large, and as shown in FIG.
If this non-uniformity cannot be sufficiently removed with one or two stages as shown in FIG. 15, sufficient uniformity can be achieved by arranging parts with different Qs in multiple stages. To simplify, let the first stage Q = W/4 and the mth stage Q, = W/2.
'''+1 is sufficient.

The ease of design and production is shown below, as well as the performance obtained.

Here, we will design a type with reflective surfaces on the sides. 35
Slightly larger than the film size, 28n+m x 40InI for mm slide projectors! Assume that + luminous flux is obtained.

Adopting the configuration shown in Figure 6, first, as parts for vertical uniformity, W = 28 mm H = 40 mm, the material is methacrylic resin (PMMA resin), n = 1.49 Using the formula, θ = θ. = 26.5' From equations ■ and ■, α = 26. 5' β=41.8°Q=W/4
=7+nm, d+ =cL =1.5 mm■
Substitute into the formula 7 = (1.5X2)X0.5 +LX0.89 From this L =: 6.2mm To facilitate production, T = l. Omm. Next, for the parts used for horizontal uniformization, θ and T are equal (W = 40 mm H = 28 mm Q = W/4 = 1 0 mm, d + = da
= 1.5 mm as 1 0 = (1.5X 2)
XO. 5 + L x O. 89, it becomes L”9.6mm.

This concludes the design and is extremely simple. Figures 16 and 17 are measurement examples of the incident light 5 output light in this design example in the configuration shown in Figure 1.The Y axis is parallel to the long side of the output surface, and the center of each surface is On the straight line passing through and from now on H/4
It shows the light intensity distribution on straight lines separated by . When the incident light has the light amount distribution shown in FIG. 16, the light amount distribution of the output light becomes as shown in FIG. 17, and it can be seen that sufficient uniformity has been achieved.

Here, if the spread angle of the luminous flux is δ = 20°, then D > T
/ tan δ = 2.8 m + n, and the required length of this optical component is at least 6.2 + 9.6 + 1.5 x 4 + 2.8
=24.6 ROM Even if there is some margin, it is 3 cm
Less is more than enough. As described above, the optical system using the present invention is extremely compact, and it is difficult to construct an optical system with a similar function using a relay capacitor, which is impossible using the method shown in Japanese Patent Application No. 106779/1983. It is.

In addition, in the present invention, when a ray of light is incident on the surface of a prism,
When light rays exit from the surface of the prism, some of the light rays are reflected, reducing the amount of transmitted light. This reflection loss is around 10% when n = 1.5. To reduce this loss and increase efficiency, apply an anti-reflection coating to each prism surface that minimizes the reflectance at a predetermined angle of incidence. Good. It is also effective to lower the reflectance by thinly coating the material with a low refractive index material.

[Effects of the Invention] As explained above, the optical component according to the present invention is as follows: (1) The transparent bodies 1 and 2 can be manufactured by integral molding, and the design is simple, so it can be provided at low cost.

(2) The transparent bodies 1 and 2 are plate-shaped and there is a space between them, so the transparent bodies 1 and 2 are lightweight and compact.

■It is easy to align both transparent bodies 1 and 2, and the installation work can be done easily.

It has the following advantages.

Further, according to the present invention, it is possible to uniformize the light intensity of the non-uniform light flux produced by using a reflective curved surface or lens in the light source without impairing the beam properties, and to achieve uniform light flux with high efficiency. A light source that can provide a luminous flux can be easily produced and has great practical effects.

[Brief explanation of drawings]

Fig. 1 shows the structural unit of the present invention, Fig. 2 is a partially enlarged view thereof, Fig. 3 shows the light intensity distribution of incident light, and Fig. 4 shows the principle of uniformization of light beams. Figure 5 is a diagram showing that there are rays that pass through different optical paths than the rays shown in Figure 1 because the incident light beam has a divergence angle, and Figure 6
Figures 7 and 7 are diagrams for explaining the basis for deriving formula (2), Figures 8 and 9 are diagrams showing deformation of a transparent body, and Figures 10 (a) and (bl are integrally molded, respectively). Figures 11 and 12 show examples using transparent bodies made of
The figures each show an example of a laminate according to the present invention, Fig. 13 shows an example in which a low refractive index medium is used instead of an air space, and Fig. 14 shows uniformity in one structural unit. Figure 15 is a diagram showing an example of a homogenized component configured with two structural units perpendicular to each other in the homogenization direction;
17 and 17 are diagrams showing the light amount distribution of incident light and emitted light, respectively. 1.2...Transparent body 3...-θ plane 4...+θ plane 7...Reflection surface 15...Structural unit 20...Incidence surface 21 of transparent body 1...Transparent body 1 Output surface 22...Incidence surface 23 of transparent body 2...Output surface 30 of transparent body 2...Prism unit 43.43°...Light source 50...Serrated transparent body

Claims (2)

[Claims] (1) Two rectangular transparent plates each having a plurality of prism units formed in a stripe shape so that one side is flat and the other side satisfies condition A, with the ridgelines of each prism unit parallel to each other and each other. What is claimed is: 1. An optical component for uniformizing light flux, characterized in that the optical component is constructed by superimposing at least one structural unit in parallel, with the structural units being arranged in parallel so that their plane sides face each other. Condition A: The Y-axis is parallel to the two perpendicular sides of the transparent plate,
If we take the Z-axis and the X-axis in the direction perpendicular to the surface, then the ridgeline of the prism unit is parallel to either the Y-axis or the Z-axis, and both sides of each prism unit are parallel to the X-axis, as shown below. [1] and [2] are formed so as to form an angle θ to −θ shown in equations. θ_0-δ/(1+8n^2)^1^/^2<θ<θ_
0+δ/(1+8n^2)^1^/^2...[1] θ_0=cos^-^1((1+8n^2)^1^/^
2/4n)...[2] However, δ is the smaller of the spread angle of the incident light flux or the spread angle (±δ) that can be used by a device that uses the output light flux, and δ<θ_0 n: of the transparent body. refractive index (2) An optical component characterized in that a reflective surface parallel to the XZ plane and/or a reflective surface parallel to the XY plane of the coordinate system of condition A is installed in contact with the optical component according to claim 1.