JPS6340970A - Image pickup method for object having prescribed height - Google Patents

Abstract

PURPOSE:To obtain a higher object image then a reference surface by converting photoelectrically and storing only a slit light irradiating part on an object and storing a series of images, by utilizing a fact that radiated parts on the object and on the reference surface are shifted in the horizontal direction, when a slit light is radiated obliquely to the object having height from the reference surface. CONSTITUTION:A printed board 10 is fixed to an XY base having a reference surface, and a CCD camera 1, and a laser slit light source 12 are provided right above and in the diagonal upper direction, respectively. A slit light is projected at an angle alpha, a camera window W is made a little narrower than slit width/cosalpha, an image pickup is executed and an image is stored. An irradiation is executed by the width W each, partial images of chip parts 13-15 are accumulated successively, and in the end, the whole images 13'-15' are formed. By outputting them, a chip image is obtained. By selecting suitably the projection angle of the slit light, the slit width and the window width in accordance with the height of the chip parts, a minute object on a substrate can be distinguished from the substrate and can be recognized easily and exactly.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an imaging method suitable for application to inspecting the mounting state of chip components mounted on a printed circuit board, and particularly relates to a slit light and a photoelectric conversion device. combined. The present invention relates to a method of imaging an object having a predetermined height from a reference plane.

[Technical background of the invention and its problems] In general, in the process of mounting various chip components on a patterned printed circuit board and then soldering them, the chip components are temporarily attached to the printed circuit board. An inspection is being carried out to see if it is attached correctly. Conventionally, as shown in FIGS. 9 and 10, as such an inspection method, light is irradiated from the diagonal of the printed circuit board 20 on which the chip component 21 is mounted, and the chip component 21 is
The difference in brightness (black and white) between the shadow (black) caused by the height of the chip and the top surface of the chip component that is illuminated by the light was recognized by a camera 23 installed directly above. However, in such an imaging method, the shadow part may not be clearly black due to the unevenness of the printed circuit board 20 and the reflection of light, and depending on the part, only the electrode (metal) part (21a) at both ends may be white. In some cases, such parts cannot be recognized as a single part, or it is impossible to accurately image or identify such parts.

[Objective of the Invention] The present invention solves the difficulties of the conventional imaging methods and provides an imaging method that can accurately identify tall objects such as chip components on a printed circuit board.

[Summary of the Invention] In order to achieve such an object, in the imaging method of the present invention, when a slit light is irradiated from a diagonal direction to an object having a height from a reference plane, a This method takes advantage of the fact that the slit light irradiation part on the object and the slit light irradiation part on the reference surface are horizontally spaced, and only the slit light irradiation part on the object is cut out by a photoelectric conversion element.
This is stored in a storage device, and by repeating this operation while moving the object in the horizontal direction relative to the slit light and the photoelectric conversion element, a series of images is stored in the storage device, and this image is stored in the storage device. By outputting , an image of an object higher than the reference plane is obtained.

Next, the principle of the imaging method of the present invention will be explained with reference to five drawings.

In FIG. 1, a slit beam 1, such as a laser beam, has a slit width of LW and is projected onto a reference plane 2 at a predetermined angle α. A photoelectric conversion device, such as a matrix camera 3, is installed above the reference plane 2, and the reflected light of the laser beam can be captured in the window 4 of the field of view (F, O, V) of the camera. At this time, window 4
Since it is a necessary condition that the slit light is not irradiated on the part of the reference surface 2 that is captured by the slit light and that the slit light is irradiated only on objects that are above a certain height (ht), such projection of the slit light Angle (α) and width of window 4 (W
) and the location of the camera, etc. must be selected.

Also, the height H from the reference plane 2 is within a certain range (h!<H<h2
) In order to capture the object below the camera window, the upper limit of the slit light must pass through the intersection B between the desired height h2 and the left edge of the window, or exceed it. To do this, the width LW of the slit light is defined as hl, which is the height from the reference plane of the intersection A of the lower limit of the laser beam 1 and the right edge of the window (in the figure), and the intersection of the upper limit of the laser beam and the right edge of the window. When the height of A' from the reference plane is h2', formula 0 and (
Since the formula 0 holds true, the formula ■ must be satisfied.

LW= (h2'-hI) 5ina-
・('Dh2'-h2 = W tanα...
・・・・・・・・・■h2'=W 11. ana
+ h2 − ・・t■′＊”−t, w= (h
2- h 1+W tan α) sin α·-t; 3+ means that the higher h2 (that is, when capturing objects with a wider range of heights), the wider the slit width (LW) needs to be. Similarly, if the width W of the window is to be increased, the slit width (LW) must also be increased. However, in reality, slit light has a distribution as shown in Figure 2, and the wider the width of the slit light, the more difficult it becomes to obtain sharp slit light. You should choose appropriately. A method for dealing with objects of different heights will be described in detail in the embodiments described later. Further, as the slit light, one having a high degree of sharpness is preferred, and a laser slit light is preferably used. In the imaging method of the present invention, the part where the slit light is not irradiated on the reference plane but only on the object at a predetermined height is captured in the window of the camera,
After inputting the image into the storage device and repeating the cutting out of the image of the object at a predetermined height and inputting it into the storage device while moving the camera and slit light relative to the object, the image is stored in the storage device. By reproducing the captured image, the entire image of the object is obtained.

[Embodiments of the Invention] A preferred embodiment of the present invention will be described below with reference to the drawings.

Embodiment 1 In FIG. 3, a printed circuit board 10 is fixed to an X-Y stage (not shown) having a reference plane 2, a camera 11 such as a CCD camera is mounted above the stage, and a light source 12 of laser slit light is mounted diagonally above the stage. is installed. The printed circuit board 10 has a flat board surface and is preferably black or black ν.
The surface should be colored with a thickness of 0.5 m.
Chip parts 13, 14, and 15 of about m size are temporarily attached. When such a printed circuit board IO is irradiated with laser slit light, the light is irradiated onto the shaded area as shown in FIG. 4(a). The window W of the camera is defined by its irradiation width (
Set the slit width/cosα (where α is the projection angle) to be slightly narrower, capture the image, and store it in the storage device (buffer).
B2 (Fig. 4(b)).

Next, the printed circuit board is scanned by the window width using the XY stage, and similar imaging (FIG. 5(a)) and input to the buffer B2 (FIG. 5(b)) are performed. By repeating these steps, partial images of the chip 13 and I4.15 irradiated with the laser slit light are sequentially stored in the buffer B2, and finally the entire image 1 as shown in FIG.
3', 14' and 15' are formed. Output this,
Get the chip image. The projection angle of the laser slit light, the slit width, and the window width are appropriately selected depending on the height of the chip component.

Example 2 In this example, a printed circuit board 10' on which components 16 and 17 of different heights are mounted is simultaneously scanned and imaged, and two windows W1 and W2 are arranged side by side within the field of view of the camera. This allows one of the two parts 16 and 17 with different heights (
The lower one) 16 is captured in window Wl, the other (higher one)
17 is captured in window W2, the cut-out images are output and stored in different buffers B2 and B3, and images 16' and 17' are formed in the respective buffers 2.3, which are combined at the time of output to obtain the entire image. .

Embodiment 3 In this embodiment, the camera 11 is installed so that the field of view of the camera 11' is substantially perpendicular to the slit light (FIG. 8). When the camera 11 is installed perpendicularly above the reference plane 2 (the position indicated by the broken line), the reflected light of the slit light at the rear end 18a of one component 18 is reflected by the reference plane 2 and captured by the window of the camera. Something happened. In this case, it is difficult to obtain a clear image behind the component 18. This embodiment eliminates the influence of reflected light that causes noise, and as is clear from FIG. Since they are perpendicular to each other, almost no light enters the window W.

Further, since the reflected light reflected by the component surface 18b is captured by the window W as almost regular reflection light, the illuminance becomes high, and therefore an image with good contrast can be obtained.

[Effects of the Invention] As is clear from the above embodiments, in the method of imaging an object with a certain height according to the present invention, a slit light is irradiated diagonally to an object of a certain height, Since only the part of the object that is irradiated with the slit light is cut out using a photoelectric conversion device, minute objects such as chip components on a printed circuit board can be easily and accurately identified by distinguishing them from the printed circuit board. Furthermore, objects of various heights and sizes can be handled by appropriately selecting the angle of the slit light, the slit width, and the width and number of camera windows.

[Brief explanation of drawings]

FIG. 1 is a diagram showing an overview of the present invention, FIG. 2 is a diagram showing the luminous intensity of the slit light in FIG. 1, FIG. 3 is a diagram showing an outline of the first embodiment of the method of the present invention, and FIG. FIG. 5 is a diagram showing the steps of the first embodiment, FIG. 6 is a diagram showing an image obtained in the first embodiment, and FIG. 7 is a diagram showing the steps of the first embodiment. FIG. 8 is a diagram showing the outline of the third embodiment of FIG. 7, and FIGS. 9 and 10 are diagrams showing the conventional chip component inspection method. 1 ・・・・・・・・・・・・・・・Slit light 2...
........Reference plane 3, 11.11'...
...Matrix camera 3, W, W, ,V, ・-
Window B1, B2......Memory @(
Buffer) 10.10' ...... Printed circuit board 13.14.15.16.17.18 ... Chip parts (object) agent Patent attorney Moritani - Figure 1 Figure 2 Figure 3 Figure 4 (a) (b) Figure 5 (a) (b) Figure 6 Figure 9

Claims (1)

[Claims] A slit light is irradiated obliquely only onto an object at a predetermined height from this reference surface without irradiating the reference surface, and the reflected light from the irradiation is imaged by a photoelectric conversion device installed above the object and stored in a storage device. The object is imaged while moving in one direction relative to the slit light and the photoelectric conversion device, a series of images are stored in the storage device, and this is output, thereby capturing the entire image of the object. A method for imaging an object at a predetermined height, characterized by obtaining an image.