JP6482223B2 - Light irradiation device and work inspection device - Google Patents

Description

  The present invention irradiates light on an object (work) such as a product, for example, in a factory, and the like, and a light irradiation device suitably used for appearance inspection and reading of a symbol written on the surface, and the light The present invention relates to a workpiece inspection apparatus using an irradiation apparatus.

  Conventionally, for example, an object such as a product is irradiated with light to create a suitable illumination environment, and then the object is imaged with an imaging device such as a CCD camera to perform automatic appearance inspection and automatic symbol reading. The system is known.

  As a light irradiation apparatus used in this system, as shown in Patent Document 1, a large number of fine reflecting portions are arranged on the surface on the side opposite to the object of the transparent plate so that gaps are formed between them. There is one in which LED light is introduced from the side peripheral end face of the transparent plate. The light travels while being totally reflected in the transparent plate, but a part of the light is reflected by the reflecting portion and irradiated from the transparent plate toward the object. In addition, since there is a gap between the reflection units, the imaging apparatus can capture an image of the object with almost no influence from the reflection units so as to look into a bright room from the screen door.

JP 2003-98093 A

  By the way, when such a light irradiation apparatus is used, a moire (interference fringe) may be generated on the imaging screen depending on the magnification on the imaging apparatus side, which may affect the inspection or the like. In order to reduce this moire, Japanese Patent Application Laid-Open No. H10-228667 describes a method of arranging the reflective portions at a non-uniform pitch, for example.

  However, just because the reflection parts are arranged at a non-uniform pitch, the moire generated on the imaging screen is not necessarily reduced to such an extent that it does not affect the inspection or the like. There is a problem that the layout design of the parts and the production thereof are very time consuming and expensive.

  On the other hand, the inventor of the present application has made extensive studies on the arrangement design of the reflecting portions in order to reduce the moire to less than a predetermined value. I found something for the first time.

  Therefore, the present invention has been made as a result of the above-mentioned diligent studies by the inventors of the present application. For example, the main problem is to reduce the moire below a predetermined level so that the moire generated on the imaging screen does not affect the inspection or the like. To do.

  That is, in the light irradiation apparatus according to the present invention, a gap is formed between one side of the light-transmitting plate that is a work-facing surface that faces the work that is the object of light irradiation and the other surface of the light-transmitting plate. A plurality of reflection portions provided in the manner described above, and a light source portion provided at a position where the emitted light passes through the translucent plate and reaches the plurality of reflection portions, and is reflected by the multiple reflection portions Is configured to be able to irradiate the workpiece, and the light irradiation device is configured to be able to transmit the light reflected by the workpiece to the opposite side through the gap, and a distance between two reflecting portions and a predetermined reference When the angle formed by a straight line connecting the two reflecting parts with respect to a line is used as relative position information, the number of types of different relative position information among the plurality of relative position information obtained by the plurality of reflecting parts, and the plurality A plurality of reflection parts As the product of the variation amount indicating the variation of the release is equal to or greater than a predetermined value, characterized in that said a plurality of reflecting portions are provided list.

  If it is such a light irradiation apparatus, the variation amount which shows the dispersion | variation in the number of types of mutually different relative position information among several relative position information obtained by several reflective parts, and the several distance obtained by several reflective parts Since the plurality of reflecting portions are arranged in a random manner so that the product of and becomes a predetermined value or more, moire generated by the plurality of reflecting portions can be reduced below a predetermined value. Specifically, it will be described in detail together with the data. In addition, when arranging a plurality of reflection parts at random, it is only necessary to arrange a plurality of reflection parts using the product of the number of types of relative position information and the amount of variation as a parameter. Thus, it is possible to reduce the arrangement design of the reflection part and the time and cost of its production.

The other surface has a plurality of partition regions having the same arrangement pattern of the plurality of reflecting portions, and the product of the number of types and the variation amount in each partition region is a predetermined value or more. In addition, it is desirable that the plurality of reflecting portions be provided side by side.
In this case, the arrangement pattern of the reflecting portions is divided into a plurality of partitioned regions that are the same as each other, and the product of the number of types and the amount of variation obtained by the plurality of reflecting portions included in each partitioned region is a predetermined value or more. Therefore, it is possible to reduce the time and cost of the arrangement design of the reflecting portion and the production thereof as compared with the case where the arrangement design of the plurality of reflecting portions on the entire other surface is performed.

Moreover, the workpiece inspection apparatus according to the present invention includes the light irradiation device described above and an imaging device that captures the workpiece by capturing the light reflected by the workpiece and passing through the transparent plate through the gap. The imaging area of the imaging device on the other surface of the translucent plate is configured so as not to have uniform dots in which three or more reflecting portions are arranged at equal intervals and in a straight line. Features.
According to such a workpiece inspection apparatus, it is possible to reduce moiré caused by a plurality of reflecting portions to less than a predetermined value, and it is possible to improve inspection accuracy such as appearance inspection and symbol reading written on the surface. In addition, since the imaging region of the imaging device on the other surface of the translucent plate is configured not to have uniform dots in which three or more reflecting portions are arranged at equal intervals and in a straight line, moire is further increased. Can be reduced.

  According to the present invention configured as described above, in the light irradiation device configured to be able to irradiate the workpiece with the light reflected by the many reflecting portions and configured to transmit the light reflected by the workpiece to the opposite side through the gap. Moire generated by a plurality of reflecting portions can be reduced.

The center vertical positive end view which shows the internal structure of the light irradiation apparatus in one Embodiment of this invention. The top view of the light irradiation apparatus in the embodiment. The partial expansion vertical positive end view which mainly shows the reflection part of the light irradiation apparatus in the embodiment. FIG. 3 is a detailed view of part A in FIG. 2. The schematic diagram for demonstrating relative position information. The schematic diagram for demonstrating the number of types of relative position information. The figure which shows the arrangement | positioning aspect of the some reflection part in the embodiment. The figure which shows the relationship between the coordinate of a sensor, and light quantity. The figure which shows the simulation result which shows the relationship between "the number of types" x "standard deviation ((sigma))", and a moire amount. The schematic diagram which shows the generation | occurrence | production mechanism of a moire.

  An embodiment of a light irradiation apparatus according to the present invention will be described below with reference to the drawings.

  As shown in FIGS. 1 and 2, the light irradiation device 1 according to the present embodiment has a thin plate shape as a whole, and is arranged orthogonally on an imaging axis C between the workpiece W and the imaging device 5. Then, the work W is illuminated and a part of the light from the work W is transmitted, so that the image pickup of the work W can be performed by the imaging device 5. The light irradiation device 1 and the imaging device 5 constitute a workpiece inspection device 100.

  Specifically, the light irradiation device 1 includes a rectangular plate-shaped optical member 2, a light source unit 3 that irradiates light from the periphery of the optical member 2, and a frame body that holds the optical member 2 and the light source unit 3. 4 is provided.

  In particular, as shown in FIG. 3, the optical member 2 includes a translucent plate 21 that is set toward a workpiece W such as a product that is a light irradiation target, with one surface being a workpiece facing surface 21 a, and the translucent plate 21. And a large number of reflecting portions 22 arranged side by side on the other surface (the surface opposite to the workpiece) 21b.

  The translucent plate 21 is a colorless and transparent plate having a uniform thickness and a square plate shape in plan view, and is made of, for example, acrylic or glass.

  As shown in FIGS. 3 and 4, the reflection unit 22 has a two-layer structure of a reflection layer 221 that irregularly reflects light and a light blocking layer 222 that hardly reflects light, and each of them is, for example, a plane surface. It has a circular shape, has a diameter of several tens to several hundreds of μm, and a thickness that is extremely small and thin on the order of microns. A large number of the reflection portions 22 are randomly distributed over substantially the entire surface excluding the side peripheral edge portion of the anti-work facing surface 21b of the translucent plate 21 so that a minute gap S is formed between them. They are arranged side by side. A detailed arrangement mode will be described later.

Further, each reflecting portion 22 has the reflecting layer 221 attached to the anti-work facing surface 21b of the translucent plate 21 so that the reflecting layer 221 faces the workpiece W side. FIG. 3 is a schematic diagram for understanding, in which the thickness of the reflecting portion 22 is exaggerated, and the thickness of the translucent plate 21 is expressed thinner than the actual thickness. The reflective layer 221 is formed of, for example, a white pigment containing a particulate reflective filler (not shown) that is a light diffusing member, and mainly reflects light on the light reflecting surface that is the surface thereof. A part of the light entering the inside is diffused and reflected by the reflection filler. On the other hand, the light blocking layer 222 is formed using a matte black material (for example, brown or gray) such as chromium oxide (CrO ₂ ). In this embodiment, a thin chrome layer (not shown) having a mirror surface is further provided between the light blocking layer 222 and the reflective layer 221 for the purpose of reflecting light transmitted through the reflective layer 221. It is.

  The light source unit 3 includes four units respectively corresponding to the four side peripheral end surfaces 21 c of the light transmitting plate 21. Each unit is composed of a single wiring board 32 having a belt shape and a plurality of LEDs 31 mounted on the wiring board 32 at a regular interval, and these LEDs 31 are arranged so as to face the side peripheral end face 21c of the translucent plate 21. Then, light is emitted from the side peripheral end face 21 c toward the inside of the light transmitting plate 21.

  The frame body 4 has a rectangular (square) ring shape, and is made of a metal having, for example, a circumferential groove opened on the inner circumferential surface, and holds and accommodates the light source unit 3 in the circumferential groove. Further, at the opening edge of the groove, the side peripheral edge of the translucent plate 21 is sandwiched and held from the thickness direction.

Next, the operation of the light irradiation device 1 configured as described above will be described.
First, as shown in FIG. 1, the workpiece W and the imaging device 5 are placed facing each other, and the light irradiation device 1 is placed on the imaging axis C so that the workpiece facing surface 21 a faces the workpiece W therebetween. Install in.

  In this state, when light is irradiated from the light source unit 3, the light enters the inside from the side peripheral end surface 21c of the translucent plate 21, and as shown in FIG. It progresses while totally reflecting between 21a and the anti-work opposing surface 21b. In the process, the light that has reached the reflecting portion 22 attached to the anti-work facing surface 21b is diffusely reflected there, exits from the work facing surface 21a as uniformed diffused light, and is irradiated toward the work W. . With this light, the workpiece W is illuminated uniformly.

  On the other hand, the imaging device 5 captures the workpiece W as described above by capturing the light reflected by the workpiece W and passing through the transparent plate 21 through the gap S between the reflecting portions 22. W surface inspection and symbol reading. In addition, since the reflection part 22 is fine, this reflection part 22 does not interfere with imaging so that a bright room can be seen through a screen door. In this way, the reflected light from the reflecting section 22 can illuminate from the direction coaxial with the observation axis C of the imaging device 5, and the workpiece W is imaged by the imaging device 5 through the gap S to be inspected. It can be carried out.

  By the way, in the case where a plurality of reflecting portions are arranged in a row at an equal pitch, the vertical (or horizontal) arrangement pitch of the image elements is substantially the same as the CCD camera as the imaging device 5 of this embodiment. If it is uniform, moire may occur in the captured image. The cause of the moire as far as the present inventor has clarified is “light reflected by the reflecting portion and directed toward the workpiece W, and then reflected again by the workpiece facing surface and directed toward the imaging device”. More specifically, as shown in FIG. 10, when each reflection portion (virtual image of each reflection portion due to back surface reflection) reflected on the image element by the light substantially overlaps with a real image of each reflection portion reflected on the image element, Moire can occur.

  Thus, in the present embodiment, when the distance L between the two reflecting portions 22 and the angle θ formed by the straight line connecting the two reflecting portions 22 with respect to the predetermined reference line X are used as relative position information (see FIG. 5). Further, the product of the number of different types of relative position information among the plurality of relative position information obtained by the plurality of reflection units 22 and the variation amount indicating the variation of the plurality of distances L obtained by the plurality of reflection units 22 is predetermined. A plurality of reflecting portions 22 are randomly arranged so as to be equal to or greater than the value.

  Here, the distance L between the two reflecting portions 22 is a linear distance between the center points of the two reflecting portions 22. Further, the predetermined reference line X is the same in each of the plurality of reflecting portions 22, and in the present embodiment, is an X-axis line that passes through the center point of the reflecting portion 22 and extends in the right direction on the paper surface.

  Next, “the number of different types of relative position information among a plurality of pieces of relative position information obtained by the plurality of reflecting units 22” will be specifically described.

As shown in FIG. 6, when the five reflection parts A to E are considered, the relative position information between one reflection part A and each of the other reflection parts _{B to E} is (L _{(A → B)} , θ _{(A → B)} ), (L _{(A → C)} , θ _{(A → C)} ), (L _{(A → D)} , θ _{(A → D)} ), (L _{(A → E)} , θ _{(A → E)} ). Further, the relative position information between another reflecting portion B and each of the other reflecting portions A and C to E is (L _{(B → A)} , θ _{(B → A)} ), (L _{(B → C)} , θ _{(B → C)} ), (L _{(B → D)} , θ _{(B → D)} ), (L _{(B → E)} , θ _{(B → E)} ). Considering the other reflection parts C to E in the same manner, a plurality of pieces of relative position information obtained by the five reflection parts A to E are 20 in total.

Among the plurality of relative position information, B relative position information viewed from A (L _{(A → B)} , θ _{(A → B)} ) and A relative position information viewed from _B (L _{(B → A))} , Θ _{(B → A)} ), C relative position information viewed from A (L _{(A → C)} , θ _{(A → C)} ) and A relative position information viewed from _C (L _{(C → A))} , Θ _{(C → A)} ), and the like, the two pieces of relative position information obtained by the pair of reflecting portions are the same. When the two pieces of relative position information obtained by the pair of reflecting portions are the same, the number of types of relative position information different from each other is 10 (= ₅ C ₂ ). In addition, if there is the same relative position information other than the relative position information obtained by the pair of reflecting portions, it is subtracted from the number of types of different relative position information (a total of 10).

That is, the maximum value of the different relative position information obtained by the plurality (N) of reflection units 22 is a total of _N C ₂ (= N × (N−1) / 2). If there is the same relative position information other than the relative position information obtained by the pair of reflecting portions 22, it is subtracted from the number of different types of relative position information (total _N C ₂ ). At this time, to increase as much as possible the number of types of relative positional information, i.e., the number of types of different relative position information with each other, in order to _two meter _N C has a plurality of reflecting portions 22, three or more It is essential that the reflection portions 22 are configured so as not to have uniform dots arranged at equal intervals and in a straight line. In the present embodiment, the imaging region of the imaging device 5 on the other surface 21b of the translucent plate 21 is configured not to have uniform dots in which three or more reflecting portions 22 are arranged at regular intervals and in a straight line. Yes.

The “variation amount indicating the variation of the plurality of distances L” is a standard deviation of a plurality ( _N C ₂ ) of distances L.

  And in this embodiment, as shown in FIG. 7, the other surface (anti-work opposing surface) 21b has a plurality of partition regions 2R having the same arrangement pattern of the plurality of reflecting portions 22, and each In the partitioned area 2R, a plurality of reflecting portions 22 are arranged side by side so that “the number of types of relative position information” × “standard deviation of distance (σ)” is a predetermined value or more. FIG. 7 shows a case where the other surface (the anti-work facing surface 21b) is divided into 16 partition regions 2R having the same shape in plan view. If this is the case, the arrangement pattern of the reflecting portions 22 is divided into a plurality of partitioned regions 2R that are identical to each other, and the product of the number of types and the amount of variation obtained by the plurality of reflecting portions 22 included in each partitioned region 2R is predetermined. Since it is only necessary to design the arrangement so as to be greater than or equal to the value, it is possible to reduce the arrangement design of the reflecting portion 22 and the time and cost for manufacturing the reflecting portion 22 as compared with the case where the arrangement design of the plurality of reflecting portions 22 on the entire other surface is performed. it can.

  Next, a simulation result of “the number of types of relative position information” × “standard deviation of distance (σ)” for making the moire amount in the light irradiation apparatus 1 of the present embodiment less than a predetermined amount will be described.

  In this simulation, the size and the shape of the reflecting portion 22 are circular with a diameter of 0.21 mm or a diameter of 0.30 mm. Here, the simulation using the 0.21 mm diameter and the simulation using the 0.30 mm diameter were each performed the same number of times. The translucent plate 21 had an optical effective area size of 50 mm × 50 mm and a thickness of 10 mm. Furthermore, the number of the reflection portions 22 in one partition region 2R is an arbitrary number within the range of 4 to 88. In addition, the size and shape of one partition region 2R is a square having one side of 1.0 mm to 2.8 mm, and specifically, one side is 1.0 mm, 1.3 mm, 1.6 mm, 2 A square of 0.0 mm, 2.4 mm, and 2.8 mm was used. Then, the simulation was performed by arbitrarily combining the shape and size of the reflection portion, the number of reflection portions in the partition region, and the shape and size of the partition region described above. In addition, the distance between the light irradiation device 1 and the imaging device 5 was confirmed at several points in a range (50 mm to 200 mm) installed in actual use, and the moire amount at the distance where the moire amount was the largest was adopted.

  At this time, as shown in FIG. 8, when the horizontal axis is the coordinates of the sensor (image element) and the vertical axis is the amount of light obtained by the sensor (image element), the peak and the peak are concerned. "Peak"-"valley" in which the difference ("peak"-"valley") from one of the two sides adjacent to the maximum value is defined as the moire amount. Here, the peak is a range with the first inflection points on both sides of the valley adjacent to the mountain as both ends, and the light amount of the peak is the inflection point at both ends. The value between is averaged. Note that the light amount on the vertical axis in FIG. 8 is a value with no unit in the simulation, but has a one-to-one proportional correlation with the actually measured light amount. Shows a similar trend.

FIG. 9 shows the relationship between the “number of types of relative position information” × “standard deviation of distance (σ)” obtained by this simulation and the moire amount.
As can be seen from FIG. 9, the moire amount decreases as the value of “number of types of relative position information” × “standard deviation of distance (σ)” increases. For example, in order to reduce the moire amount to less than 5, it is understood that “the number of types of relative position information” × “standard deviation of distance (σ)” may be set to 400 or more.
In addition, even if it is not the number of reflection parts shown in the simulation, similarly, as the value of “number of types of relative position information” × “standard deviation of distance (σ)” increases, the amount of moire is reduced. By making “the number of types of relative position information” × “standard deviation of distance (σ)” equal to or greater than a predetermined value, the amount of moire can be reduced to less than the predetermined value.

<Effect of this embodiment>
According to the light irradiation device 1 according to the present embodiment configured as described above, the number of types of different relative position information among the plurality of relative position information obtained by the plurality of reflection units 22 and the plurality of reflection units 22 are obtained. Since the plurality of reflecting portions 22 are randomly arranged so that the product of the standard deviation indicating the variation in the plurality of distances is equal to or greater than a predetermined value, the moire generated by the plurality of reflecting portions 22 is reduced to less than a predetermined value. can do.

  Further, when the plurality of reflecting portions 22 are randomly arranged, the plurality of reflecting portions 22 may be arranged using the product of the number of types of relative position information and the variation amount as a parameter. Compared to the above, it is possible to reduce the layout design and the manufacturing time and cost of the plurality of reflecting portions 22.

  Furthermore, since the moire generated by the plurality of reflecting portions 22 can be reduced below a predetermined level, it is possible to improve inspection accuracy such as appearance inspection and reading of symbols written on the surface. In addition, since the imaging region of the imaging device 5 on the other surface 21b of the translucent plate 21 is configured not to have uniform dots in which three or more reflecting portions 22 are arranged at regular intervals and in a straight line, Moire can be further reduced.

The present invention is not limited to the above embodiment.
For example, in the above-described embodiment, the plurality of reflecting portions are arranged so that “the number of types of relative position information” × “standard deviation of distance (σ)” is equal to or greater than a predetermined value in the entire other surface (the surface opposite to the workpiece). Although the arrangement is arranged side by side, in a part of the other side (the surface opposite to the workpiece), a plurality of “relative position information types” × “distance standard deviation (σ)” is set to a predetermined value or more. It is good also as a structure which provides a reflection part side by side. Specifically, in the effective imaging region of the imaging device, a configuration in which a plurality of reflection units are arranged so that “the number of types of relative position information” × “standard deviation of distance (σ)” is equal to or greater than a predetermined value. It is possible.

In FIG. 7, all of the plurality of partition regions 2R have the same arrangement pattern. However, a part of the partition regions 2R in the plurality of partition regions 2R and the other part of the partition regions 2R The arrangement patterns may be different from each other. Moreover, it may be divided so that the planar view shape of some of the partitioned areas 2R and the planar view shape of other partially partitioned areas 2R are different from each other.
In addition to the above-described embodiment, the reflecting portion may be, for example, a concave portion provided on the surface opposite to the workpiece of the translucent plate. In short, the light incident from the end surface of the translucent plate is reflected toward the workpiece side. Any dot can be used.

  In addition, the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.

DESCRIPTION OF SYMBOLS 100 ... Inspection apparatus W ... Work 1 ... Light irradiation apparatus 2 ... Optical member 21 ... Translucent plate 21a ... One surface (work opposing surface)
21b... The other surface (surface facing the workpiece)
S ... Gap 22 ... Reflecting part 3 ... Light source part L ... Distance X between two reflecting parts ... Predetermined reference line θ ... A straight line connecting the two reflecting parts Angle 5 ... Imaging device

Claims (3)

A light-transmitting plate whose one surface is a workpiece-facing surface facing a workpiece that is a light irradiation target;
A number of reflecting portions provided on the other surface of the light-transmitting plate so that gaps are formed between each other;
A light source unit provided at a position where the emitted light passes through the translucent plate and reaches the plurality of reflection units;
A light irradiation device configured to irradiate the workpiece with the light reflected by the multiple reflecting portions, and configured to transmit the light reflected by the workpiece to the opposite side through the gap,
When the distance between the two reflecting portions and the angle formed by a straight line connecting the two reflecting portions with respect to a predetermined reference line are used as relative position information,
The product of the number of types of relative position information different from each other among the plurality of relative position information obtained by the plurality of reflection parts and the standard deviation of the plurality of distances obtained by the plurality of reflection parts is 400 or more. The light irradiation apparatus in which the plurality of reflection units are arranged at random . The other surface has a plurality of partition regions having the same arrangement pattern of the plurality of reflecting portions,
The light irradiation apparatus according to claim 1, wherein the plurality of reflection units are arranged side by side so that a product of the number of types and the amount of variation in each partition region is equal to or greater than a predetermined value. The light irradiation device according to claim 1 or 2,
The reflected at the workpiece, by capturing light passing through the transparent plate through the gap, obtain Preparations and an imaging device for imaging the workpiece workpiece inspection device.