JPH11108844A - Light source device for inspection of mirror surface materials and transmission materials - Google Patents

Abstract

(57) [Summary] A lighting position of an inspection light source can be arbitrarily controlled so as to obtain an optimum inspection image, and an optimum lighting pattern is automatically determined. The light source can control a lighting pattern arbitrarily.
An ED array light source 14 is used. The LEDs are sequentially turned on for each inspection area for each row, an optimum lighting row range is obtained, and the lighting position is automatically optimized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a light source device for inspecting a specular material and a transmissive material, and in particular, to obtain an image for inspecting a defect of the specular material and the transmissive material and reading a mark or a print on the material. The present invention relates to a light source device for inspection of a specular material and a transmission material used in an optical system to be used.

[0002]

2. Description of the Related Art An optical system is important for obtaining a high-quality image of an object to be detected in a material inspection / measurement. In particular, a light-transmitting material (transmitting material) and a mirror surface material transmit and refract light through the material. ,
Due to reflection and scattering, the positional relationship between the light source and the object is particularly important. Usually, in the inspection and measurement of this kind of material,
In order to improve the detection sensitivity, a dark field optical system or a bright field optical system in which the light source has light and dark is used, and each of the two optical systems has a reflection type and a transmission type.

FIG. 8 shows a transmission type dark field optical system, and FIG. 9 shows a transmission type bright field optical system. In the figure, reference numeral 1 denotes a planar light source, 2 denotes a light-shielding mask, 4 denotes an object to be detected, 5 denotes an object to be detected such as a defect or a character, and 6 denotes a camera for photographing a transmission image of the object to be detected. In the conventional optical system shown in each figure, a light-shielding mask 2 is arranged in front of a planar light source 1, and the light-shielding mask 2 gives light and dark to the light source to illuminate the detection object 4, and The change of the refraction and reflection angle of light by the detection target 5 is captured as a transmission image by the camera 6 and the detection target is detected.

[0004]

However, in the optical system for detecting a detection target by utilizing the change in the refraction and reflection angle of light as described above, the expected angle θ of the light source with respect to the detection target is S / N or the like. There is a problem that the detection sensitivity is affected. When the detection target has directionality, it is necessary to improve the detection sensitivity by giving the light source directionality in accordance with the directionality of the detection target. For this reason, conventionally, the height (Z in FIG. 8) of the light source and the mask width W
Must be adjusted mechanically, which is complicated.

Further, when the inspection object has a curved surface, the distance between the inspection object and the light source changes at each point of the inspection object, and the expected angle θ changes, so that there is a difference in the detection sensitivity on the inspection object. To do so, a light-shielding mask having an appropriate curvature in the horizontal or vertical direction must be prepared for each type according to the type of the object to be detected, which is troublesome. Further, even in a mode in which inspection within a certain area is performed using an area camera or the like, an optimum detection area that can be inspected at a time is limited to a narrow area in relation to a light source. There is a disadvantage that the object or the optical system must be moved mechanically, the position changing mechanism is complicated, and the position setting operation is complicated.

The present invention has been made in view of the above circumstances, and does not require complicated position setting of the optical system, and can always perform detection under optimum detection conditions, and can enlarge a detection area. An object of the present invention is to provide a light source device for inspection of a mirror surface material and a transmission material.

[0007]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention irradiates a mirror material and a transmission material with illumination light to capture an image of a detection object formed on the mirror material and the transmission material. A light-emitting unit in which a plurality of light-emitting sources which can be turned on / off independently are arranged in a plane, in a light source device for inspection of a mirror material and a transmissive material used for an inspection optical system observed through means; Control means for controlling lighting / extinguishing of each light emitting source and changing a lighting position of the light emitting unit.

[0010] According to the present invention, since a light emitting unit in which a plurality of light emitting sources which can be independently turned on / off controlled is arranged in a plane is employed as the light source, the lighting position of the light emitting unit can be easily changed and controlled. . Thereby, various lighting patterns can be formed, and the S / N of the detection target can be easily improved. Therefore, it is possible to always perform the detection under the optimum detection condition by always lighting in the optimum lighting pattern for the detection.

Further, in order to achieve the above object, the present invention irradiates a mirror material and a transmission material with illumination light, and captures an image of a detection object formed on the mirror material and the transmission material via an imaging means. In a light source device for inspecting a specular material and a transmissive material used for an inspection optical system to be observed, a light emitting unit formed in a planar shape and a light emitting unit arranged in a plane on a front surface of the light emitting unit and independently transmitting / shielding light. And a control means for controlling the transmission / shielding of each of the shutter means and changing the lighting position of the light emitting section.

According to the present invention, the lighting position of the light emitting section is changed by combining the planar light emitting section and the shutter means and controlling the transmission / shielding of the shutter means. Even with such a configuration, various lighting patterns can be formed, and detection can be performed with a lighting pattern that is optimal for detection. Further, in the light source device for inspection of the mirror material and the transmission material according to the present invention, the image of the detection target is sequentially photographed via the imaging means while changing the lighting position of the light emitting unit, and the inspection is performed based on the acquired photographed image. It is also possible to automatically determine the most suitable lighting pattern.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a light source device for inspecting a specular material and a transmissive material according to the present invention will be described below in detail with reference to the accompanying drawings. FIGS. 1 and 2 show an example in which the light source device for inspecting a mirror material and a transmission material according to the present invention is applied to a character reading device of a funnel glass for a cathode ray tube. FIG. 1 is a plan view, and FIG. 2 is a side view thereof. The funnel glass 10 for a cathode ray tube has a three-dimensional curved surface shape, and has random irregularities of several μm in height called frost on the entire surface of the product.

A convex character 12 having a height of several tens μm is press-molded on the surface of the funnel glass 10 for a cathode ray tube. Such a convex character 12 indicates, for example, a mold number, and as shown in FIG.
m, about 5 mm in width, with a character spacing of about 2 mm, formed side by side with several characters. The character reading device shown in FIG. 1 reads the convex character 12 and mainly includes an LED.
An inspection light source device including an array light source 14 and light source control means (not shown) for controlling turning on / off of the LED array light source 14, and a transmission image of the convex character 12 illuminated by the LED array light source 14. Area camera 16 for shooting
And The area camera 16 has an angle of view that can photograph the three character strings shown in FIG. 3 at a time, and is fixed at a predetermined position via a camera support member 18.

This character reading device employs a dark-field optical system for detecting, as a bright point, a convex shape of an edge portion of a character formed on the surface of the funnel glass 10 for a CRT, and is illuminated by an LED array light source 14. An image of the character portion is captured by the area camera 16, and the character is read based on the acquired image. The read information is used as feedback data for eliminating defective products.

FIG. 4 is a plan view of the LED array light source.
FIG. 5 is a side view thereof. This light source is composed of 12 × 18 (216 in total) light emitting diodes (LEDs) 20, 20... Arranged on a substrate 22.
It has a size of about mm × 72 mm. Note that reference numeral 2
Reference numeral 4 denotes a casing for accommodating the substrate 22, and a diffusion plate 26 is provided on a front surface of the light emitting unit.

Each of the light emitting diodes 20, 20,... Can be turned on / off independently, and each of the light emitting diodes 20, 20,.
Lighting / extinguishing is controlled by light source control means (not shown). The light source control means can arbitrarily change the lighting position (lighting pattern), and by controlling the lighting position, a dark portion and a bright portion can be arbitrarily formed in the planar light emitting portion.

Next, the operation of the character reading apparatus to which the inspection light source device configured as described above is applied will be described.
When reading the convex character 12 formed on the funnel glass 10 for a cathode ray tube using the character reading device shown in FIG. 1, it is most important to distinguish the convex shape of the character from the peripheral uneven shape (frost). This is one of the issues.

When attention is paid to a specific character edge, the point P at which the line connecting the area camera 16 and the character edge intersects the planar LED array light source 14 is a dark portion, and the periphery thereof is a bright portion. Is required. Therefore, utilizing the difference in the angle of refraction of light between the irregularities of the character edge and the irregularities of the frost part, the width W of the dark part of the light source is set to distinguish between the two.

FIG. 6 shows the relationship between the projection angle θ corresponding to the width W of the dark portion of the planar light source and the relative detection intensity of the image detected by the area camera 16. In the present embodiment, the angle of refraction at the uneven portion of the character edge is larger than the angle of refraction at the uneven portion of the frost portion. Therefore, as shown in FIG. It is large and it is difficult to detect character edges.

However, as the expected angle θ gradually increases, the detection intensity due to the frost unevenness decreases, and instead, the detection intensity due to the character edge increases. When the expected angle exceeds a certain value θ0, the detected intensity of the character edge exceeds the detected intensity of the frost, and the character edge can be detected. Therefore, by setting the width of the dark portion of the planar light source to a value W0 or more corresponding to the expected angle .theta.0, only the character edge portion can be detected as a bright portion.

When reading the three-character string shown in FIG. 3, the three-character inspection area frame is divided into, for example, six in the horizontal direction and three in the vertical direction to be divided into a total of nine detection areas.
The light source is turned on in an optimal pattern for each of the detection areas to capture an image. Then, three character strings can be detected by taking the "OR" of the images nine times and connecting them to one image. When detecting a vertical edge of a character, a dark area is formed in parallel with the edge.

Next, a procedure for determining an optimum lighting pattern for each of the divided detection areas will be described. FIG.
3 shows an example in which the inspection area frame is divided into three in the horizontal direction, and the LED array light source 14 is simply shown as a column lighting light source. Reference numeral 30 in the drawing indicates an inspection area frame of a character string to be detected.

The three divided detection areas A 1, A 2, A
3, the optimum lighting pattern for one detection area (for example, the middle area in the figure) A2 is determined by the following procedure. First, for this detection area A2,
The LED array light sources 14 are sequentially turned on for each vertical column from the first column (N1) on the left side in the figure to the last column (Nend). At this time, when the frost portion is detected, a random spot pattern is detected on the image captured by the area camera 16.

Since a random speckle pattern on an image can be grasped as noise in the image, the allowable maximum number K of noise is set in advance, and noise (speckle) exceeding this is detected. In this case, the position (row position) of the currently lit LED row is stored. In this way, when the light source spreads on both sides of the detection area in a planar manner, a range of Na to Nb where the number of noises exceeds the allowable maximum number K is obtained.
Turn off the columns Na to Nb determined by the above-described steps,
By illuminating the other rows, an optimal illumination pattern for the inspection area A2 can be obtained.

In the other inspection areas, the lighting pattern can be similarly optimized. In addition, the inspection area frame 30
In the case where is divided in the vertical direction, the LED array light sources 14 are sequentially turned on for each horizontal row, so that the lighting row can be optimized by the same method as described above. In the character reading apparatus of FIG. 1, the three character strings are divided into six in the horizontal direction and three in the vertical direction using the method described with reference to FIG. The lighting pattern is automatically determined, and nine kinds of screens are photographed while the lighting pattern of the LED array light source 14 is temporally switched. Then, the three character strings can be read by superimposing the nine images and connecting them to one image. Thus, a relatively large inspection area can be inspected at a time without mechanically moving the inspection object or the optical system.

In the above embodiment, the case where the LED array light source is used has been described as an example, but the form of the light source is not limited to this. That is, the light source may be divided into cells in a matrix, and lighting / extinguishing may be controlled in an arbitrary lighting pattern, and a combination of a planar light source and a liquid crystal shutter may be used. For example, a lighting pattern can be changed by disposing a liquid crystal shutter in front of a single planar light source and controlling transmission / shielding of the liquid crystal shutter.

Further, in the above-described embodiment, the character reading apparatus for reading the convex characters of the funnel glass for a cathode ray tube has been described as an example. However, the present invention is not limited to a dark-field optical system or a bright-field optical system. Further, the present invention can be widely applied to various inspection optical systems such as defect inspection using a translucent material as an object to be inspected, and reading of engraving and printing.

[0027]

As described above, according to the light source device for inspecting a mirror material and a transmissive material according to the present invention, a light emitting portion in which a plurality of light emitting sources that can be turned on / off independently can be arranged in a plane. Or a combination of a planar light emitting unit and a shutter means to change and control the lighting position of the light emitting unit, so that various lighting patterns can be easily formed, and the optimal lighting pattern for detection can be obtained. Detection can be performed.

According to the present invention, an image of a detection target is sequentially photographed through an image pickup means while changing a lighting position of a light emitting section, so that an optimal lighting pattern for inspection is obtained based on the acquired photographed image. Can be automatically determined. Further, since the detection can be performed while changing the lighting pattern, it is possible to divide the inspection area observed by the imaging unit and illuminate the inspection area with the optimal lighting pattern for each inspection area, and it is possible to perform inspection and inspection. There is an advantage that a relatively large inspection area can be inspected at a time without mechanically moving the optical system.

[Brief description of the drawings]

FIG. 1 is a plan view showing a configuration of a character reading apparatus to which the present invention is applied.

FIG. 2 is a side view of the character reading device shown in FIG. 1;

FIG. 3 is a plan view showing an example of a convex character formed on the surface of the funnel glass for a cathode ray tube shown in FIG. 1;

FIG. 4 is a plan view of the LED array light source shown in FIG. 1;

5 is a side view of the LED array light source shown in FIG.

FIG. 6 is a graph showing a relationship between an expected angle corresponding to a width of a dark portion of a light source and a relative detection intensity.

FIG. 7 is a conceptual diagram used for explaining a method of automatically optimizing a lighting position.

FIG. 8 is a plan view showing the configuration of a conventional transmission type dark field optical system.

FIG. 9 is a plan view showing a configuration of a conventional transmission type bright field optical system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Funnel glass for cathode-ray tubes (transmissive material) 12 ... Convex character (detection object) 14 ... LED array light source 16 ... Area camera 20 ... Light emitting diode (light emitting source) 26 ... Diffusion plate

Claims (4)

[Claims] A mirror material used in an inspection optical system for irradiating the mirror material and the transmission material with illumination light, and observing an image of a detection target formed on the mirror material and the transmission material via an imaging unit; In the light source device for inspecting a transmissive material, a light emitting unit in which a plurality of light emitting sources that can be turned on / off independently is arranged in a plane, and turning on / off of each of the light emitting sources is controlled to turn on the light emitting unit. A light source device for inspecting a specular material and a transmissive material, comprising: control means for changing a position. 2. The light source device according to claim 1, wherein the light emitting unit is configured by two-dimensionally arranging light emitting diodes as light emitting sources. 3. A mirror material used in an inspection optical system for irradiating the mirror material and the transmission material with illumination light, and observing an image of a detection target formed on the mirror material and the transmission material via an imaging means; A light-emitting device for inspecting a transmissive material, comprising: a light-emitting portion formed in a planar shape; and a plurality of shutter means arranged in a plane on a front surface of the light-emitting portion and capable of independently switching between transmission and light-shielding; Control means for controlling transmission / shielding of each shutter means to change a lighting position of the light emitting section, and a light source device for inspecting a mirror material and a transmission material. 4. A light source device for inspecting a mirror material and a transmissive material according to claim 1, 2 or 3, wherein the control unit changes a lighting position of the light emitting unit and detects an object to be detected via an imaging unit. An automatic lighting pattern determination means for sequentially photographing the images and determining an optimal lighting pattern for the inspection based on the acquired captured image.