JP2005214688A - Light source device for inspection - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To realize a light source device for inspection, capable of illuminating with high efficiency, without unevenness in color and brightness by a light produced by overlapping light beams of different wavelengths. <P>SOLUTION: To the light source device for inspecting radiating specified light signal to an object to be checked by combining the emission lights from a plurality of light sources, a polygonal column which is so formed that introduction light conducted by only inside is provided. The emission lights from a plurality of light sources are made incident on one bottom of the polygonal column, and the emission light from the other bottom of the polygonal column is irradiated to the object to be inspected. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an inspection light source device, and more particularly, to an improvement in light amount and an improvement in illuminance and color uniformity of an inspection light source device.

Conventionally, in the inspection of a light receiving element, a configuration is used in which a predetermined light source is used to irradiate a light receiving element to be inspected with light of a known color or amount of light, and an electrical signal output from the light receiving element is monitored. . The inspection light source device used here includes a configuration in which light is superimposed using a plurality of light emitting elements that emit light having different wavelengths.
Prior art documents related to such an inspection light source device include the following.

JP 59-214734 A

FIG. 4 is a configuration diagram showing an example of a conventional inspection light source device.
In FIG. 4, the light emitting units 41 and 42 are combined with the condenser lenses 43 and 44 so as to allow light to enter the semi-transparent mirror or the band pass filter 45. The semi-transparent mirror or band-pass filter 45 transmits half of the light emitted from the light emitting unit 41 and reflects half of the light emitted from the light emitting unit 42, so that these lights are superimposed on the same optical path and incident on the inspection object 46.

FIG. 5 is a configuration diagram showing another example of a conventional inspection light source device.
In FIG. 5, the light emitting portions 51 and 52 are combined with the condensing lenses 53 and 54 so as to allow light to enter the light receiving end face of the bundle fiber 55. Light incident on the light receiving end face of the bundle fiber 55 from the two light emitting units 51 and 52 is superimposed in the bundle fiber 55 and guided to the inspection object 57 through the lens 56.

However, the inspection light source device shown in the conventional example has the following problems.
In the inspection light source device having the configuration using the semi-transparent mirror in FIG. 4, the transmittance decreases according to the square of the transmittance each time the light of different wavelengths to be synthesized increases, and the three colors using the two semi-transparent mirrors. In the configuration, there is no loss at all, and even when the transmittance and the reflectance are 50%, (0.5) ² = 0.25, and the light collection efficiency is significantly deteriorated.

Further, in the inspection light source device having a configuration using a bandpass filter instead of the semi-transparent mirror in FIG. 4, the transmittance is generally good, and there is no problem in the synthesis of light with different wavelengths such as RGB. However, it is impossible to synthesize light that is continuous in wavelength by superimposing light having wavelengths close to each other, and it can only be used for addition of missing teeth spectrally. Furthermore, preparing an expensive bandpass filter with different characteristics corresponding to the number of light to be superimposed and configuring the optical system increases both cost and optical system size.

  On the other hand, in the configuration using the bundle fiber as shown in FIG. 5, the solid angle of the light incident on the light receiving end face is determined by the numerical aperture (NA) of the bundle fiber and has a small cross-sectional area. Cannot be imported at the same time.

  Further, since the bundle fiber is a structure in which the fibers are bundled, the distribution of chromaticity and luminous intensity at the emission end face is strictly an aggregate of grains having different chromaticity and luminous intensity for each fiber. When the end face is imaged, the illuminance distribution at the position of the inspection object is as shown in FIG.

FIG. 6 is a diagram illustrating a state where the end face of the bundle fiber is imaged.
As shown in FIG. 6, it is inevitable that the honeycomb end face of the bundle fiber is reflected and becomes a mottled pattern having different chromaticity and light amount, and the lens is imaged on the irradiated surface even if it is close to parallel light. I can't do that. That is, the efficiency is lowered because the imaging optical system having the best illumination efficiency cannot be used.

  In addition, a technique for guiding light to a bundle fiber and illuminating an object by freely drawing a free distance is common, but the light amount distribution at the emission end is not constant. The difference in the light intensity distribution at the exit end means that if light is superimposed using a plurality of light emitting elements that emit light of different wavelengths, color unevenness and illuminance unevenness will occur in the irradiated area, and light reception will occur. It cannot be used for applications such as device inspection.

FIG. 7 is a view showing the distribution of the light quantity at the exit end face of the bundle fiber.
The result of calculating the distribution of the light quantity at the exit end face after being guided to the bundle fiber at an arbitrary incident angle was plotted with the diameter of the end face on the horizontal axis and the light quantity on the vertical axis. Since the fibers are randomly crossed, the luminance does not increase only in a specific portion, but the unevenness is not eliminated and does not become uniform. In the method using the conventional light guide member, it is possible to simply guide light, but it is not possible to equalize the emission end face.

  The present invention is intended to solve the problems of such a conventional light source device for inspection, and the light generated by superimposing the light of different wavelengths is highly efficient in causing uneven color and illuminance. It aims at realizing the light source device for inspection which can perform no illumination.

  The present invention is an inspection light source device having the following configuration.

(1) In an inspection light source device that synthesizes emitted light from a plurality of light sources and irradiates a predetermined optical signal to an inspection target,
It has a polygonal column formed so that incident light is conducted only inside,
An inspection light source device characterized in that light emitted from the plurality of light sources is incident on one bottom surface of the polygonal column, and light to be inspected is irradiated from the other bottom surface of the polygonal column.

(2) In an inspection light source device that synthesizes light emitted from a plurality of light sources and irradiates a predetermined optical signal to an inspection target,
Bundle fiber,
A polygonal column formed so that incident light is conducted only inside,
With
One bottom surface of the polygonal column is brought close to the other end surface of the bundle fiber, light emitted from the plurality of light sources is incident on one end surface of the bundle fiber, and light emitted from the other end surface of the bundle fiber Is incident on one bottom surface of the polygonal column, and the inspection target light source device is irradiated with light emitted from the other bottom surface of the polygonal column.

(3) The inspection light source according to (1) or (2), further comprising at least one imaging optical system that forms an image of the bottom surface on the exit side of the polygonal column on the inspection target. apparatus.

(4) At least one condensing optical system for condensing emitted light from the plurality of light sources when entering the polygonal column or the bundle fiber is provided (1) to (3) The inspection light source device according to any one of the above.

(5) The inspection light source device according to any one of (1) to (4), wherein the polygonal column is configured such that a plane mirror is provided on a side surface and a reflection surface faces inward.

(6) The inspection light source device according to any one of (1) to (5), wherein the plurality of light sources are light emitting diodes.

The present invention has the following effects.

According to the first aspect of the present invention, a light source device for inspection that can perform illumination without color unevenness and illuminance unevenness with high illumination efficiency is realized by passing light beams generated by superimposing lights of different wavelengths through a polygonal column. can do.

  According to the second aspect of the present invention, it is possible to achieve uniform chromaticity and illuminance at a level that cannot be realized with only the bundle fiber by passing the emitted light of the bundle fiber through the polygonal column.

According to invention of Claim 3, the illumination intensity on to-be-inspected object can be made the strongest, and illumination efficiency can be improved.

According to invention of Claim 4, incident efficiency can be improved by making the light of an LED lamp inject into a polygonal column via a condensing lens.

According to the fifth aspect of the present invention, a polygonal prism can be manufactured at a low cost with a simple structure by providing a plane mirror on the inner surface of the prism and providing a reflecting surface facing inward. .

According to invention of Claim 6, it becomes long life by using an LED lamp as a light source. In addition, instantaneous switching to desired chromaticity and illuminance is possible. Furthermore, since no spectral filter is used, it can be constructed at low cost.

Hereinafter, the present invention will be described in detail with reference to the drawings.
FIG. 1 is a block diagram showing an embodiment of an inspection light source device according to the present invention. In FIG. 1, the case where the LED lamp which is a light emitting element is used as a light source is shown.
As a means for controlling the emitted light of the LED lamp, for example, a technique for adjusting the forward current to generate a desired luminance for each LED lamp and controlling the chromaticity and illuminance of the illumination is well known. The description is omitted.

In FIG. 1, LED lamps 1A to 1E are obtained by arranging a plurality of different types of LED lamps having different emission spectral distributions. An LED lamp having an emission wavelength that fills the wavelength range of visible light without a gap by a combination of spectral distributions is selected. The LEDs 1A to 1E are arranged in a conical shape with the center of the ball lens as a vertex so as to face a ball lens 3 described later. In this case, it is better to arrange so that the incident angle to the ball lens is as small as possible.
Further, since the incident efficiency varies depending on the position of the LED lamp, the amount of light applied to the object to be inspected is monitored, and the forward current may be controlled so that the amount of light of each LED becomes a desired amount of light.

  The condensing lenses 2A to 2E are optical systems that are individually optimized because the divergence angles of the light beams differ depending on the LED lamps. These are arranged as necessary, and collect the light flux of the LED lamps on the ball lens 3. Light is incident. Thereby, the incident efficiency can be improved.

  The ball lens 3 is disposed immediately before the end face 4A of the prismatic rod 4 (one bottom surface of the prism). The ball lens 3 is a ball lens whose maximum cross-sectional area is about twice as large as that of the prismatic rod. As a result, the luminous flux of the LED lamp is narrowed at a position immediately after the ball lens is emitted, and is efficiently incident on the prismatic rod 4.

The prismatic rod 4 is made of a glass material (optical glass material) or plastic (for example, transparent vinyl chloride or acrylic) and is a polygonal columnar shape whose end surfaces 4A and 4B are mirror-polished, and the light beam emitted from the ball lens 3 is reflected on the end surface. The light is taken in from 4A and emitted from the end face 4B (the other bottom face of the prism). The light beam entering the prismatic rod 4 is repeatedly reflected on the side surface of the column, and the distribution of the light beam is spatially uniform on the exit surface, so that the chromaticity and illuminance distribution are uniform. The imaging optical system 5 is, for example, a convex lens, and images the exit end 4B of the prismatic rod 4 on the inspection target 6 that is a light receiving element. The light quantity distribution at this time is shown in FIG.
The prism rod may have a configuration in which a plane mirror is provided on the inner side surface of the prism and the reflecting surface is directed inward to form a cavity. If comprised in this way, a prismatic rod can be manufactured cheaply with a simple structure.

FIG. 2 is a diagram showing the distribution of light quantity at the exit end face of the prismatic lot. The calculation was performed under the same conditions as those shown in FIG. It can be seen that the difference in the light amount distribution is reduced to 1/3 or less, and the light amount distribution is constant.

The fact that the light distribution is constant means that color unevenness does not occur, and as a result, completely uniform illumination without color unevenness and illuminance unevenness can be obtained on the object to be inspected. Will also be optimal.

By the above, an illumination part with uniform chromaticity and illuminance can be obtained in every corner, margin illumination parts can be reduced, and maximum values can be obtained for both distribution and illumination area. Here, the surplus illumination part is a light beam that has gone out of the inspection area as a result of setting the light flux so that the non-uniform peripheral part is driven out of the inspection area in order to uniformly illuminate the inside of the inspection area. Say.

  When the ball lens is not used, the cross-sectional area of the prismatic rod may be increased to some extent in consideration of the efficiency at the entrance of the prismatic rod. However, in this case, when the light to be inspected is relatively small and the light guided is reduced, the irradiation efficiency is remarkably deteriorated when the imaging optical system illuminates the object to be inspected. The prismatic lot incident efficiency must be sacrificed.

  In this embodiment, the ball lens is an optical system arranged immediately before the prismatic lot, but it may be condensed by a wide angle lens such as a fish eye lens. At this time, it is preferable to place the incident end of the prismatic lot on the imaging surface of the wide-angle lens so that the most efficient incidence can be achieved. In any case, when direct oblique light enters the prism lot, the projected cross-sectional area of the incident surface of the prism lot becomes smaller according to COSθ when the incident angle is θ, and is condensed as the incident angle increases. Although the efficiency is lowered, a reduction in the projected cross-sectional area is suppressed by a ball lens, a wide-angle lens, etc., and condensing can be performed without loss.

  Furthermore, since the ball lens has an effect of efficiently diffusing light entering the prismatic lot, it contributes to shortening the prismatic lot. In a diffusive sense, an element having a refractive action such as a diffusing plate, a single lens, and a photographing lens can be regarded as equivalent to a ball lens.

On the other hand, when a lamp that cannot be regarded as a point light source, such as a halogen lamp, requires a certain amount of absolute light, a bundle fiber is often used, but it reaches the exit end while maintaining the light intensity distribution at the entrance end. A uniform illuminance distribution cannot be obtained at the exit end.

Therefore, it is common to make the illuminance distribution at the exit end uniform by randomly knitting fiber strands. Although some improvement in the uniformity of the distribution can be seen as a result of this, if it is necessary to make the amount of light uniform after superimposing the light with different wavelengths, the color and the amount of light were different for each fiber strand. Then, uniformization cannot be achieved. A configuration for solving this problem will be described below with reference to the drawings.

FIG. 3 is a block diagram showing another embodiment of the inspection light source device of the present invention. In FIG. 3, the same components as those in FIG. 1 described above are denoted by the same reference numerals, and description thereof is omitted.
In FIG. 3, the ball lens 3 is disposed immediately before one end face (incident end face) of the bundle fiber 7, and the luminous flux of the LED lamp is narrowed at a position immediately after the emission of the ball lens, and the efficiency is applied to the incident end face of the bundle fiber 7. It is often incident and emitted from the other end face (exit end face). The prismatic rod 4 is arranged so that its incident end face (one bottom face of the prism) is close to the exit end face of the bundle fiber 7 and is inspected with uniform distribution of chromaticity and illuminance from the exit end face (the other bottom face of the prism). Illuminate 6.
The exit end face of the bundle fiber 7 and the entrance end face of the prismatic rod 4 are preferably in contact with each other, but may take a distance depending on the allowable incidence efficiency.

As described above, the advantage that the light can be easily guided by the bundle fiber 7 is left, and the bundle fiber 7 is inserted between the ball lens 3 and the prismatic lot 4 in order to obtain uniform accuracy. Can be greatly improved, and an optical system that does not impair accurate uniformity can be obtained.

Conventionally, if the end face of the bundle fiber is imaged, the image is formed as shown in FIG. 6 above, so that the image is not intentionally formed. However, the end face is made of glass or plastic and the end face is mirrored. By placing a polished prismatic lot in the middle, the object to be inspected can be illuminated in an imaging relationship with a light emitting end with uniform illuminance, so that a maximum value can be obtained for both uniform accuracy and efficiency.

Further, since the prismatic rod is uniform if it has a length of about 15 times or more of the cross-sectional dimension, it is about 100 mm if it is a bundle fiber φ4, φ6 mm generally commercially available. Therefore, it is possible to obtain high quality uniform illumination without increasing the size by remodeling an existing bundle fiber and integrally forming a prismatic lot at the tip. There is already a form in which a cylindrical end cap is made of a glass material at the entrance end and the exit end, but this does not have the intended purpose of the present invention, and is meaningful for making a prism. When the irradiation area is desired to be circular, it is sufficient to use a polygonal column with a polygonal bottom without sticking to a quadrangle.

In addition, the bundle fiber has a great feature with respect to other optical systems in that it can be easily connected to the light source section. Is easy to install.

Conventionally, lighting fixtures using light guides (bundle fibers) have been widely used for visual inspection, automatic inspection, image inspection, and laboratory use. This type of lighting fixture is supported alongside LED lighting because it is versatile by exchanging the light guide and has good operability. On the other hand, in automatic inspection and image inspection, further miniaturization, high functionality, and high productivity (strict threshold management) are required, and a more uniform and stable lighting device is required. For this reason, the conventional general inexpensive illuminating device is insufficient, and a large inspection cost is generated for an inspection target that requires expensive special illumination.

A major feature of the illumination device using the light guide is that the bundle fiber and the light source unit can be easily connected and separated, and can be exchanged according to the object. Therefore, by simply replacing the expensive light source unit with the bundle fiber using the present invention as it is, the uniformity is improved, and a highly accurate fiber unit meeting the market requirements can be realized.

  The present invention is not limited to the above-described embodiments, and includes many changes and modifications without departing from the essence thereof.

It is a block diagram which shows one Example of the light source device for a test | inspection of this invention. It is the figure which showed distribution of the light quantity in the output end surface of the prismatic lot in this invention. It is the block diagram which showed the other Example of the light source device for a test | inspection of this invention. It is the block diagram which showed an example of the conventional light source device for a test | inspection. It is the block diagram which showed the other example of the conventional light source device for a test | inspection. It is the figure which showed a mode that the end surface of the bundle fiber in the conventional light source device for a test | inspection was imaged. It is the figure which showed distribution of the light quantity in the output end surface of a bundle fiber in the conventional light source device for a test | inspection.

Explanation of symbols

1A, 1B, 1C, 1D, 1E LED lamp 2A, 2B, 2C, 2D, 2E Condensing lens 3 Ball lens 4 Rectangular rod 5 Imaging optical system 6 Object to be inspected

Claims (6)

In an inspection light source device that synthesizes emitted light from a plurality of light sources and irradiates a predetermined optical signal to an inspection target,
It has a polygonal column formed so that incident light is conducted only inside,
An inspection light source device characterized in that light emitted from the plurality of light sources is incident on one bottom surface of the polygonal column, and light to be inspected is irradiated from the other bottom surface of the polygonal column. In an inspection light source device that synthesizes emitted light from a plurality of light sources and irradiates a predetermined optical signal to an inspection target,
Bundle fiber,
A polygonal column formed so that incident light is conducted only inside,
With
One bottom surface of the polygonal column is brought close to the other end surface of the bundle fiber, light emitted from the plurality of light sources is incident on one end surface of the bundle fiber, and light emitted from the other end surface of the bundle fiber Is incident on one bottom surface of the polygonal column, and the inspection target light source device is irradiated with light emitted from the other bottom surface of the polygonal column.   3. The inspection light source device according to claim 1, further comprising at least one imaging optical system that forms an image of the bottom surface on the exit side of the polygonal column on the inspection target.   4. The apparatus according to claim 1, further comprising: at least one condensing optical system that condenses the light emitted from the plurality of light sources when entering the polygonal column or the bundle fiber. 5. The light source device for inspection as described in 2.   5. The inspection light source device according to claim 1, wherein the polygonal column is configured such that a plane mirror is provided on a side surface and a reflection surface is directed inward. The inspection light source device according to claim 1, wherein the plurality of light sources are light emitting diodes.

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