Image analysis – Histogram processing – For setting a threshold
Patent
1990-10-26
1993-09-14
Couso, Jose L.
Image analysis
Histogram processing
For setting a threshold
382 1, 382 17, 356418, G06K 900
Patent
active
052456714
DESCRIPTION:
BRIEF SUMMARY
DESCRIPTION
1. Technical Field
This invention relates to an apparatus for inspecting a printed circuit board (hereinafter referred to as a "PC board") or the like, and to a method of operating the apparatus. More particularly, the invention relates to an apparatus which inspects the properties of a curved surface and is applied in detecting the orientation of curved-surface elements of a curved-surface body comprising a set of a number of curved-surface elements the surfaces whereof are oriented in different directions; an apparatus which inspects the properties of a curved surface and is ideal for inspecting the shape of a soldered portion of a part mounted on a PC board; a PC board inspecting apparatus for extracting hue patterns in the three primary colors from an original image obtained by imaging a part mounted on a PC board, comparing the extracted results with taught data and judging the acceptability of the mounted state of the part, such as the soldered state; a teaching method for teaching, prior to inspection of the PC board, the mounted position of a part, the class of the mounted part and feature quantities of the mounted state of the part in the abovementioned inspecting apparatus; a method of setting an inspection zone for setting, prior to inspection of the PC board, a mounted-part inspection zone in the abovementioned inspecting apparatus; a method of displaying inspection results for displaying the results of part inspection on the screen of a display unit in the abovementioned inspecting apparatus; and a display method in a PC board inspecting apparatus ideal for verifying the acceptability of the extracted state of hue patterns.
2. Background Art
The shape of the surface of a soldered region of a part mounted on a PC board can be mentioned as a typical example of a curved-surface body having a multiple-oriented surface. Conventionally, such a soldered region is inspected visually, and the acceptability of the soldered state, namely the absence or presence of solder, the amount of solder and its solubility, short circuits and improper conduction are judged based on this visual inspection.
With this method using such visual inspection, however, the occurrence of inspection error cannot be avoided, judgment differs widely depending upon the individual performing the inspection, and there are limits upon inspection processing capability.
In recent years, a variety of automatic inspection apparatus capable of performing an inspection of this kind automatically have been proposed.
The shape of the surface of a soldered region is a cubic shape of three dimensions, and the ability to detect three-dimensional shape information is essential in order to inspect such a shape.
FIG. 1 illustrates an example of an automatic inspection apparatus capable of detecting three-dimensional shape information. The apparatus irradiates a soldered region on a PC board 2 with slit light 1. A reflected-light image of an optical cutting-plane line 3, which is produced on the surface of the PC board 2 inclusive of the soldered region by irradiation with the slit light 1, is picked up by an image pickup device 4, and the three-dimensional shape of the soldered portion is detected by investigating the imaged pattern.
With this inspection method, however, all that is obtained is shape information indicative of the portion irradiated with the slit light 1, and it is difficult to ascertain the three-dimensional shape of other portions. Moreover, the surface of the soldered region is such that the orientation thereof is not uniform with respect to the surface direction of the PC board. Consequently, at least four combinations of light source and image pickup device 4 are necessary. For this reason, the apparatus is complicated and a highly precise assembling operation is required. A problem is that this invites higher cost.
Accordingly, in order to solve this problem, a method is available in which the surface of a curved-surface body undergoing inspection is irradiated with light from a plurality of directions having di
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Kobayashi Shigeki
Tanimura Yasuaki
Yotsuya Teruhisa
Couso Jose L.
Omron Corporation
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