JP3539324B2 - Lighting equipment - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
The present invention relates to an illuminating device that irradiates an object with light emitted from a linear light source converged in one direction, and particularly to an illuminating device that can irradiate a wide range at a time.
[0002]
[Prior art]
2. Description of the Related Art Conventionally, as an illumination device suitable for a measurement device using a line sensor camera, a device that linearly illuminates a measurement target has been used. As an example of such a device, for example, a lighting device disclosed in Japanese Patent Application Laid-Open No. 9-31279 is known. In this apparatus, light emitted from a line light guide using an optical fiber bundle is condensed by a cylindrical lens, thereby illuminating an object linearly using light quantity effectively.
[0003]
[Problems to be solved by the invention]
However, such a lighting device also has the following problems. That is, a line light guide usually has a width limitation determined by the total amount of fibers.For example, in order to illuminate a wide band-shaped object such as a steel plate, a line light guide and a cylindrical lens are paired, and Were required to be arranged in the width direction of the irradiation target. At this time, line light guides and cylindrical lenses are arranged as closely as possible, but when performing inspection with high resolution, avoid being affected by gaps between adjacent line light guides and cylindrical lenses. I couldn't do that. Further, even if fibers having a small diameter are arranged without gaps, in order to prevent the influence of the gaps on the cylindrical lens, there is no choice but to use a single fiber, in which case the cost of the lens alone becomes extremely high There was a problem.
It is an object of the present invention to provide a lighting device which can solve a wide range at a time by solving these problems.
[0004]
[Means for Solving the Problems]
The present invention is an illumination device that irradiates an object by condensing light emitted from a linear light source in one direction by a cylindrical lens, wherein the cylindrical lens includes a plurality of cylindrical lenses whose end surfaces are polished. Consists of abutted end facesWherein the angular characteristic of the amount of light emitted from the linear light source is bilaterally symmetric with respect to the abutting surface of the cylindrical lens, and the maximum angle of incidence at which light emitted from the linear light source is incident on the cylindrical lens. Value θ ₁ Is n _Two ^Two / N ₁ ^Two − sin ^Two θ ₁ > 1. Where n ₁ Is the refractive index of air, n _Two Is the refractive index of the cylindrical lens.
[0008]
BEST MODE FOR CARRYING OUT THE INVENTION
Now, the refractive index n as shown in FIG._TwoAnd the refractive index n along the principal axis of the cylindrical lens from the plane 11 of the cylindrical lens 10₁ Incident angle θ from the medium₁ Consider the case where light enters.
In that case, as shown in FIG. 2, the light ray 1 incident from the plane 11 of the cylindrical lens is expressed by the following Snell's law.
n₁・ Sin θ₁= N_Two・ Sin θ_Two                ... (Equation 1)
Angle θ that satisfies_Two Then, the light ray 1 that has reached the convex surface 12 of the cylindrical lens is again refracted at the refraction angle θ.₁ And is emitted from the lens convex surface 12.
[0009]
On the other hand, from the plane 11 of the cylindrical lens 10 along the main axis of the cylindrical lens, the refractive index n₁ Incident angle θ from the medium₁ After the light is incident on the end surface 13 and before reaching the convex surface 12 of the cylindrical lens 10, the light beam 2 reaches the end surface 13 at an incident angle π / 2−θ._Two Will be incident. This is the refraction angle θ from the end face 13._Three, And according to Snell's law,
n_Two・ Sin (π / 2-θ_Two) = N₁・ Sin θ_Three      ... (Equation 2)
therefore,
sinθ_Three= N_Two/ N₁・ Cosθ_Two                  ... (Equation 3)
From (Equation 1),
cosθ_Two= (1-n₁ ^Two/ N_Two ^Two・ Sin^Twoθ₁)^1/2     ... (Equation 4)
From (Equation 3) and (Equation 4),
sinθ_Three = (N_Two ^Two/ N₁ ^Two−sin^Twoθ₁)^1/2       ... (Equation 5)
The condition that the light ray 2 causes total reflection at the end face 13 of the cylindrical lens 10 and no light leaks from the end face 13 is sin θ_Three> 1. By rewriting this total reflection condition,
n_Two ^Two/ N₁ ^Two−sin^Twoθ₁> 1 (Equation 6)
It becomes.
[0010]
In this case, as shown in FIG. 3, when the two cylindrical lenses 10, 10 whose end faces 13 are completely polished are brought into abutment, the light rays 2 and the light rays 3 incident on the end face 13 are respectively totally reflected and folded. However, if the light amounts of the light beams 2 and 3 are completely equal, the light beam 2 'looks as if the light beam 3 is refracted and emitted, and the light beam 3' is also refracted. Observed as if they were emitted. In other words, this is exactly the same state as a single cylindrical lens having no seam of the cylindrical lens. Therefore, as long as all the light incident on the joint at the end face of the adjacent cylindrical lens is symmetrical with respect to the angular characteristic and the amount of light with respect to the joint, it is the same as using a single cylindrical lens. Characteristics of the light source. As a result, even when the divided cylindrical lenses are used, the same optical state as that when a single long cylindrical lens is used can be realized.
[0011]
In the above example, the case where two cylindrical lenses are butted is described. However, even when three or more cylindrical lenses are butted, if the characteristics of the light source with respect to the angle characteristics and the amount of light are symmetric with respect to each joint, the same effect is obtained. I do.
[0012]
Normally, the cylindrical lens is usually chamfered, but in the case of the present invention, the chamfered surface is chamfered to avoid scattering of light on the chamfered surface and refraction in an unexpected direction. It is better to match the end faces without the joints, so that the seams are less noticeable. In the case of glass, if chipping is not performed, "chips" may occur. Therefore, it is preferable to use resin such as acrylic as a material of the cylindrical lens.
[0013]
In addition, when a cylindrical lens formed by abutting a plurality of cylindrical lenses utilizing the above principle is used, it is necessary to make the plurality of cylindrical lenses rigid.For example, an integrated holder is used. By holding a plurality of cylindrical lenses by using the same, it is possible to obtain rigidity equivalent to the rigidity of the holder. In that case, it is usual to use a metal holder, but especially when a resin-made cylindrical lens such as acryl is used, a difference in thermal expansion coefficient with respect to the cylindrical lens becomes large, so that a temperature change occurs. In such a case, the lens may be distorted or damaged. Therefore, when a cylindrical lens made of resin is used, as shown in FIG. 4, in the radial direction of the cylindrical lens 10 that is less affected by expansion, the cylindrical lens 10 is attached to the holder 15 only by considering a slight difference in thermal expansion. (See FIG. 4 (a)). On the other hand, in the longitudinal direction where the influence of expansion is large, the cylindrical lens is preliminarily taken into consideration in consideration of a large difference in thermal expansion generated between the cylindrical lens 10 and the holder 15. It is necessary to secure 10 to the holder 15 with a margin. As a fixing method in the longitudinal direction, for example, elastic members such as springs and rubbers are arranged on both left and right ends of the holder 15, and the cylindrical lens 10 is fixed to the holder 15 by these, and the length of the cylindrical lens 10 in the length direction due to heat is fixed. A method of absorbing a dimensional change by its elastic force is conceivable (see FIG. 4B). In FIG. 4B, reference numeral 16 denotes a spring for adjusting the tightening force, reference numeral 17 denotes a screw for holding the spring, and reference numeral 18 denotes a pressing plate placed between the cylindrical lens 10 and the spring 16.
[0014]
In the case of using a plurality of cylindrical lenses as described above, as a linear light source, for example, as shown in FIG. 5, an optical fiber is taken in a bundle 20 and the optical fiber is line-shaped at the output end to the very end in the width direction. A plurality of line light guides 22 arranged side by side (in the figure, the linear optical fibers are indicated by 21) can be used in close contact. However, in order to carry out the present invention, it is essential that the output light amounts of the left and right line light guides are equal, the output angle characteristics of the fibers at the output ends of the line light guides, and the directions of the fibers themselves are aligned. Needless to say,
[0015]
Finally, FIG. 6 shows a schematic configuration of an embodiment of the illumination device according to the present invention using the above-described cylindrical lens and line light guide. Here, the light emitted from the light source 23 passes through the optical fiber bundle 20 and enters the line light guide 22 in which the optical fibers are arranged on a line. The light emitted from the line light guide 22 is condensed through the cylindrical lens 10 and is irradiated on a wide object (for example, a steel plate) 24 to be inspected.
[0016]
【The invention's effect】
As described above, according to the illuminating device of the present invention, the use of a plurality of cylindrical lenses, without being affected by seams of the cylindrical lenses, and with the same effect as using one cylindrical lens Thus, it is possible to illuminate a wide object as described above, so that a device for irradiating a wide range at a time can be realized at lower cost.
[Brief description of the drawings]
FIG. 1 is a perspective view of a cylindrical lens.
FIG. 2 is a schematic diagram showing an optical path when light enters from a plane of a cylindrical lens along a main axis thereof.
FIG. 3 is a schematic view showing an optical path when light enters from a plane of a cylindrical lens along a main axis thereof in a state where end faces of two cylindrical lenses are polished and abutted against each other.
FIG. 4 is a structural diagram showing a relationship between a plurality of cylindrical lenses and a holder for holding them.
FIG. 5 is an exemplary diagram when a plurality of line light guides are used side by side.
FIG. 6 is a configuration diagram of a device showing an embodiment of a lighting device according to the present invention.
[Explanation of symbols]
Reference Signs List 10 cylindrical lens, 11 cylindrical lens plane, 12 cylindrical lens convex surface, 13 cylindrical lens end surface, 15 holder, 16 spring, 17, screw, 20, optical fiber bundle, 22 line light guide, 23 light source, 24 steel plate.

Claims (1)

An illumination device that condenses light emitted from a linear light source in one direction by a cylindrical lens and irradiates the object with light,
In the above-mentioned cylindrical lens, a plurality of cylindrical lenses whose end faces are polished are formed by abutting on the end faces ,
The angle characteristic of the amount of light emitted from the linear light source is symmetric with respect to the butting surface of the cylindrical lens,
The maximum value of the incident angle θ ₁ at which light emitted from the linear light source enters the cylindrical lens. But,
n ₂ ² / n ₁ ² − sin ² θ ₁ > 1
Where n ₁ Is the refractive index of air, n ₂ Is the refractive index of the cylindrical lens,
A lighting device characterized by satisfying the following relationship:

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