JP2017219432A - Braille inspection equipment and method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To not only recognize braille but also evaluate a braille quality.SOLUTION: Braille B on an object S is illuminated with a coaxial epi-illumination device 10, and imaged from a vertical upper side by an imaging apparatus 30. Further, the braille B is illuminated obliquely with an oblique illumination device 20, and imaged from the vertical upper side by the imaging apparatus 30. Recognition of the braille and three-dimensional shape measurement information of the braille are created on the basis of image signals imaged under each illumination of coaxial epi-illumination and oblique illumination, and a braille quality is determined on the basis of the three-dimensional shape measurement information, especially on height information.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an apparatus and method for the inspection of Braille represented on the surface of an object, in particular for inspection of Braille quality.

  Due to the widespread use of universal design, Braille notation is progressing mainly in public facilities, beverages and daily necessities. Along with this, there is a need for technologies and devices for guaranteeing the quality of Braille in products (objects) represented in Braille cheaply and efficiently.

  The Braille printed material inspection method and apparatus described in Patent Document 1 are designed to facilitate the inspection of Braille even if there is a black pattern or solid on the printed paper surface, and a predetermined incident angle on the surface of the Braille printed material. Is irradiated with light, and the regular reflected light from the surface of the Braille printed material is imaged with a CCD camera.

  The Braille inspection device described in Patent Document 2 is intended to enable accurate inspection of Braille attached to product packages, transparent sheets, and the like. In response, a transparent fluorescent ink that emits light is attached, and ultraviolet rays are irradiated to the object to be inspected, and the transparent fluorescent ink in the braille portion is caused to emit light and imaged with a camera.

JP 2002-99900 A JP 2010-181388 A

  All of the inspection methods and apparatuses described in these documents only recognize Braille, and do not perform inspection or evaluation of Braille quality, particularly Braille height.

  The present invention provides a Braille inspection apparatus and method capable of not only recognizing Braille represented on the surface of an object but also evaluating its quality, in particular, checking its height.

  The Braille inspection device according to the present invention is a coaxial epi-illumination device that irradiates coaxial epi-illumination light including parallel light perpendicular to the surface on which the Braille of the object is represented. An oblique illumination device that irradiates oblique illumination light including an oblique illumination device, an imaging device that captures an image of reflected light including light that is reflected vertically from the surface in which braille is represented, the coaxial incident illumination, and the oblique illumination Based on the image signal captured by the imaging device below, at least based on the information obtained from the image processing means for extracting the points constituting Braille and creating the three-dimensional shape measurement information of the points, and the information obtained from the image processing means Thus, a judging means for judging the braille quality is provided.

  In a preferred embodiment, the Braille inspection device further includes an output device that outputs at least one of the creation information by the image processing unit and the determination result by the determination unit. The output device is a display device, a storage device, or a communication device.

  In a preferred embodiment, the three-dimensional shape measurement information of the point includes information related to the planar shape and height.

  In one embodiment, the image processing apparatus obtains information on the height of a point based on the shadow length of the image of the point obtained by photographing under oblique illumination.

  In the Braille inspection method according to the present invention, coaxial epi-illumination light including parallel light perpendicular to the surface on which the Braille of an object is represented is irradiated to capture an image under coaxial epi-illumination from above (vertical). The oblique illumination light including parallel light is irradiated obliquely on the surface represented to capture an image under oblique illumination from the vertical (vertical) upper side, and each of the image under the coaxial incident illumination and the image under oblique illumination Based on the signal, at least the points constituting the Braille are extracted and the 3D shape measurement information of the points is created, and the quality of the Braille is determined based on at least the 3D shape measurement information.

  According to the present invention, since the three-dimensional shape of the braille including the height is measured and the shape quality inspection of each point of the braille is performed, the quality inspection with high accuracy is possible. Therefore, it is possible to provide high quality Braille. In particular, the present invention can be suitably used for an object that requires accurate reading of identification information or the like.

An arrangement of an imaging device, a coaxial incident illumination device, and an oblique illumination device is shown. The block diagram which shows the electric constitution of a braille inspection apparatus. The top view which shows an example of Braille. Sectional drawing which follows the VI-VI line of FIG. The image which image | photographed the actual Braille same as the Braille of FIG. 3 under coaxial epi-illumination is shown. The image which image | photographed the actual Braille same as the Braille of FIG. 3 under oblique illumination is shown. An actual Braille image taken under coaxial epi-illumination is shown. 8 shows an image obtained by binarizing the image of FIG. The figure which drew the mass block in the binary image of FIG. Indicates the braille recognized. The barycentric position in a binary image is shown. An actual Braille image is shown under oblique illumination. The state of measuring the shadow length is shown. The principle of point height measurement is shown. The concept of height measurement for irregular points is shown.

  FIG. 1 shows the positional relationship between an object in which Braille is represented, a coaxial incident illumination device, an oblique illumination device, and an imaging device. FIG. 2 shows the main features of the Braille inspection device including image processing means, determination means, and the like. This shows the electrical configuration of the unit (excluding the lighting device). FIG. 3 is a plan view showing an example of Braille having an ideal shape (corresponding to “Me” in the Japanese syllabary), and FIG. 4 is a sectional view taken along line IV-IV in FIG.

  3 and 4, Braille inspection object S is a public facility, food / beverage package, container or box, etc., which has been subjected to Braille, but is generally portable. Is a movable property. On the surface of the object S, Braille Braille composed of a maximum of six points of 2 × 3 is represented. Six points are indicated by symbols B1, B2, B3, B4, B5, and B6, and a Braille character constituted by a combination of the presence or absence of these points is indicated by a symbol B. Each point in Braille has a hemispherical shape if it is formed normally (ideally). The range of each Braille consisting of a maximum of 6 points is called a Braille block. As described later, a substantially square virtual shape surrounding each point is called a mass. Braille is arranged to create words (braille words) and sentences (braille text). 3 and 4, a range (Braille block) in which one Braille (one unit of Braille) is represented is indicated by a rectangle, and this is an object S. In general, the rectangular part is a part of the object. A braille block may be affixed to the object, or the object itself may be deformed to form braille.

  In FIG. 1, Braille B (object S) is placed at an inspection position (inspection place). The object S may be placed at the inspection position by hand, or the inspection position is set to a predetermined position on the conveyance path of the conveying device, the object S is conveyed by the conveying device, and the object S reaches the inspection position. In this case, the conveyance may be stopped and the inspection may be performed.

  A coaxial epi-illumination device 10 is disposed directly above the inspection position (vertically above), and an imaging device 30 is further disposed thereon. The coaxial epi-illumination device 10 irradiates coaxial epi-illumination light including parallel light perpendicular to the surface (braille block) on which the braille of the object S is represented, and includes a surface light source 11 and a half mirror 12, for example. The half mirror 12 deflects the illumination light from the surface light source 11 perpendicularly to the surface of the object S and transmits specularly reflected light from the surface of the object S. The specularly reflected light transmitted through the half mirror 12 is directed to the imaging device 30. The surface light source 11 preferably includes a lot of parallel light. In order to perform inspection while avoiding (or suppressing) adverse effects caused by patterns, patterns, etc. drawn on the surface of the object, it is important to increase the parallelism of the light incident on the surface of the object, which is highly parallel It is recommended to use a lighting device or raise the installation position of the lighting device. Furthermore, by using a lens with a narrow angle of view (long focal length), it is possible to observe specularly reflected light even at the field of view. The inspection range can be expanded. As described later, Braille reading (Braille recognition) and planar (two-dimensional) shape measurement such as diameter and roundness are performed using an image captured under coaxial incident illumination.

  The oblique illumination device 20 is disposed so as to project obliquely incident light (oblique light) onto the surface of the object S on which the Braille B is represented. The oblique illumination device 20 includes, for example, a point light source 21 and a convex lens or a Fresnel lens 22 having a convex lens function, and the point light source 21 is arranged near the focal point of the Fresnel lens 22. The oblique illumination device 20 also emits oblique illumination light including parallel light. The oblique illumination is used to capture an image representing a Braille shadow including Braille height information. Even when the braille is transparent, it is desirable to use bright illumination with high parallelism so that the braille shadow can be extracted stably. In addition, the longer the shadow, the better the measurement accuracy, so that the shadow does not touch the adjacent braille at a shallow (low) angle as much as possible (for example, it is incident on the surface of the object at an angle of about 10 degrees). ) It is desirable to irradiate.

  2, the signal processing device 40 includes an image processing unit (image processing unit) 41, a determination unit (determination unit) 42, a control unit (control unit) 43, and the like. The signal processing device 40 is configured by a computer, for example. The signal processing device 40 is connected to an imaging device 30, an operation unit (operation device) 44, a display device 45, and a storage device 46, and a communication device if necessary. The imaging device 30 is a visible light (or infrared light) electronic camera. When the operation start operation is performed by the operation unit 44, a start signal is given from the operation unit 44 to the control unit 43, a trigger signal is output from the control unit 43 at a predetermined timing, and the imaging unit device 30 detects the surface of the object S. An image of Braille B is acquired. First, a lighting command is given to the coaxial epi-illumination device 10 from the control unit 43, and imaging is performed by the imaging device 30 in synchronization therewith. Thereafter, a lighting command is given to the oblique illumination device 20, and the imaging device 30 performs imaging in synchronization therewith. That is, imaging under coaxial epi-illumination and imaging under oblique illumination are performed separately. The image data acquired by the imaging is transferred to the image processing unit 41, Braille is extracted by processing described later, Braille reading, and three-dimensional shape measurement are performed. Then, the determination unit 42 compares the acquired character string and the shape measurement value with a predetermined determination value, and performs pass / fail determination. The inspection information including the determination result is displayed on the screen of the display device 45 together with the identification code of the object S, and is stored in the storage device 46 linked to the identification code of the object, or is stored in a management device such as a server by a communication device. Sent. The above processing may be automatically performed in conjunction with a transport device that transports an object, or may be performed with human intervention.

  FIG. 5 shows an example of an image obtained by imaging an actual Braille having the same configuration as the Braille shown in FIG. 3 by the imaging device 30 under the coaxial epi-illumination by the coaxial epi-illumination device 10. As described above, each point of Braille B forms a hemispherical convex portion upward from the surface of the object S, so that the parallel incident light is irradiated from the coaxial epi-illumination device 10 perpendicularly to the surface of the object S. Then, the light regularly reflected on the surface of the object S (light reflected substantially vertically) is incident on the imaging device 30, but the imaging device 30 directly above the light regularly reflected on the hemispherical surface of each point. There is almost no light incident on. Therefore, the surface of the object S is bright and dark in the region corresponding to the hemispherical surface of the points. This image is suitable for extracting points constituting Braille.

  FIG. 6 shows an example of an image obtained by imaging an actual Braille having the same configuration as the Braille shown in FIG. 3 by the imaging device 30 under oblique illumination by the oblique illumination device 20. An oblique line indicates oblique illumination light. A shadow is generated around each point of Braille B, and the shadow extends on an extension line of oblique illumination light. The image including the long shadow is an image in which the height information of the points is visualized. If the shadow of a point touches an adjacent point, the measurement accuracy decreases, so it is desirable to illuminate from the direction in which the distance between adjacent points becomes longer as indicated by the arrows.

  The processing of the image processing unit 41 will be described with respect to an image obtained by imaging under the coaxial incident illumination.

  FIG. 7 shows an example of an image represented by an image signal output from the imaging device 30 by imaging an actual Braille character under the coaxial incident illumination.

  An image obtained by binarizing the image shown in FIG. 7 with a predetermined threshold is shown in FIG. 8 (inverted in black and white). In the image of FIG. 8, for example, an area represented by a white pixel and other feature amounts of the shape are measured, and the measured value is subjected to threshold processing, and when a predetermined threshold is exceeded, it is determined that a point exists (point Extraction). Measure the shape of the extracted points such as diameter and roundness. This shape measurement can be used to evaluate the quality of dots or braille. The shape measurement value may be used for point extraction. Instead of the binarization process, an edge detection process may be performed. Braille can be extracted based on the shape feature such as the area calculated based on the edge detection processing result, or the above shape measurement can be performed based on the edge detection processing result. Higher accuracy can be expected when shape measurement is performed on the points extracted by the edge detection process than when the binarization process is performed.

  Subsequently, a square 2 × 3 square (shown by a broken line) surrounding each point in the braille block is formed on the image, and it is determined whether or not there is an extracted point (the presence or absence of a point) in each square. Acquires the position (arrangement) of points in the braille block. In the example of FIG. 9, points B1, B2, and B6 exist. Braille reading (braille recognition) is performed by comparing the arrangement of the extracted points in the braille block with a previously registered braille list. As shown in FIG. 10, the braille that produces the image of FIG. 7 is recognized as the text “ki”.

  Next, processing of the image processing unit 41 that measures the height of each point in Braille will be described.

  The center of gravity of each point portion (point portion) extracted in the image obtained by imaging under the coaxial incident illumination is calculated. In FIG. 11, the center of gravity of the point B2 in the binarized image shown in FIG. 8 is indicated by cg.

  In the image obtained by imaging under oblique illumination, as shown in FIG. 12, a measurement area Ar including a long shadow ka is formed with the previously calculated center of gravity cg as a reference position. A binarization process or an edge detection process is performed in the measurement area Ar, and a point shadow ka is extracted. Then, as shown in FIG. 13, a distance L (maximum distance between the center of gravity and the shadow) between the center of gravity cg of the point and the tip of the shadow ka is calculated, and this distance L is converted into the height of the point. For this conversion, a calibration table (calibration table) of the height of the points actually measured and the length of the shadow (the center of gravity and the length to the tip of the shadow) is created, and the height is calculated using this table. Can be obtained.

  FIG. 14 shows the principle of point height measurement in Braille. When the point Bi (i = 1 to 6) has a hemispherical normal shape or a shape close thereto, the distance between the tip P of the shadow formed when illuminated obliquely and the center of gravity cg is It is proportional to the height H of the point Bi. This assumes that the point is highest at the center of gravity of the point.

  As shown in FIG. 15, when the shape of the point Bi is considerably deformed from the normal shape, it is not always the highest at the position of the center of gravity cg. If oblique illumination light is irradiated only from one direction, the measurement accuracy may be reduced. In order to prevent a decrease in measurement accuracy, oblique illumination is performed separately from the opposite direction (or two different directions close to the opposite direction), and images are taken in each oblique illumination (imaging under coaxial epi-illumination is performed once. Good). The distance between two shadow tips P1 and P2 obtained based on images under oblique illumination from two different directions may be measured.

  The determination unit 42 determines the quality of each point or Braille based on the three-dimensional shape measurement information (diameter, roundness, height, etc.) of each point obtained in the image processing unit 41. For example, a threshold (such as a non-defective product height range, an upper limit value or a lower limit value) is set for the height of each point, and the quality of each point can be determined by comparison with the threshold value. Even if the roundness and the radius are compared with the threshold values determined for these in this determination, the quality of the point shape can be determined in consideration of the result. If all the extracted points constituting the braille are determined to be good, the braille can be accepted.

  As described above, the three-dimensional shape of the braille including the height is measured and the shape quality inspection of each point of the braille is performed, so a high-quality inspection can be performed. Therefore, it is possible to provide high quality Braille. In particular, the present invention can be suitably used for an object that requires accurate reading of identification information or the like.

10 Coaxial epi-illumination device
20 Oblique lighting system
30 Imaging device
40 Signal processor
41 Image processing unit (image processing means)
42 Judgment part (judgment means)
43 Control unit
44 Operation section
45 Display device (output device)
46 Storage device (output device)
B Braille B1, B2, B3, B4, B5, B6 Point S Object cg Center of gravity ka Shadow

Claims (7)

A coaxial epi-illumination device that radiates coaxial epi-illumination light including parallel light perpendicular to the surface on which the braille of the object is represented,
An oblique illumination device that irradiates oblique illumination light including parallel light obliquely onto the surface represented by Braille,
An imaging device that captures an image of reflected light including light that is vertically reflected from the surface in which braille is represented;
Image processing means for extracting at least points constituting Braille and creating three-dimensional shape measurement information of points based on image signals captured by the imaging device under the respective illumination of the coaxial incident illumination and oblique illumination; And determination means for determining braille quality based on information obtained from the image processing means,
Braille inspection device.   The braille inspection apparatus according to claim 1, further comprising an output device that outputs at least one of creation information by the image processing unit and a determination result by the determination unit.   The braille inspection device according to claim 2, wherein the output device is a display device.   The braille inspection device according to claim 2, wherein the output device is a storage device.   The braille inspection apparatus according to claim 1, wherein the three-dimensional shape measurement information of the points includes information regarding a planar shape and a height.   The braille inspection apparatus according to claim 1, wherein the image processing apparatus obtains information regarding the height of a point based on a shadow length of an image of the point obtained by photographing under oblique illumination. Coaxial epi-illumination light including parallel light perpendicular to the surface on which the braille of the object is represented is taken, and an image under the coaxial epi-illumination is taken from above.
Illuminating obliquely illuminating light including parallel light obliquely onto the surface in which Braille is represented, and taking an image under obliquely illuminating from vertically above,
Based on the respective image signals of the coaxial epi-illumination image and the oblique illumination image, at least extraction of points constituting Braille and creation of three-dimensional shape measurement information of the points,
Judgment of Braille quality based on at least the 3D shape measurement information
Braille inspection method.