Optical: systems and elements – Single channel simultaneously to or from plural channels – By surface composed of lenticular elements
Reexamination Certificate
2001-02-23
2003-05-06
Mack, Ricky (Department: 2873)
Optical: systems and elements
Single channel simultaneously to or from plural channels
By surface composed of lenticular elements
Reexamination Certificate
active
06560024
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a scan head and an appearance inspection technique, and it particularly relates to a scan head which scans an object under inspection and obtains information, and an appearance inspection method and apparatus which inspect the appearance of the object using the scan head.
2. Description of the Related Art
It is certain that Information Technology (IT) could define an aspect of the new hundreds in the twenty-first century as well as biotechnology. In the IT field, the product cycle is very short as symbolized as “dog year”, and the speed of development and the cost reduction are more critical as ever and a key to the survival of enterprises.
The hardware to support such an IT boom can be categorized into the Internet as an infrastructure, and the information device such as personal computers, personal digital assistance (PDA) and a cellular phone. The latter, that is, various kinds of terminals have been explosively spread and used. It highly owes to downsizing and low price in manufacturing, which has been achieved by high integration design.
High density implementation technology is an element to realize the high integration design, as well as rich types of design tools and advancement in semiconductor technology. The main point in the high density implementation is in manufacturing and inspecting technique. Conventionally, In-Circuit Tester (ICT) has been used to inspect the print circuit board after electrical components are implemented. However, the contact-type inspection apparatus cannot deal with the high density in implementation, and non-contact type, particularly an appearance inspection apparatus using image recognition technique has been highly demanded.
The concept of applying image recognition technology to the appearance inspection is well known for ages. Considering the situation in which even a compact board has several hundreds to over a thousand of parts implemented, however, very high resolution, for example, order of 20 microns, is required for the image to be inspected. Thus it likely takes longer to inspect the board compared to implementing components, and it becomes a very large hamper in a severe competition in product developments.
Under the situations described above, the applicant of the present invention proposed an appearance inspection apparatus having a line sensor in Japanese Patent Application Laid-open No. H8-254500. The apparatus includes a vertical light source as well as a side light source which was common at that time, and switches between two light sources according to testing items. The point of the apparatus is described as follows.
FIG. 1
shows a substrate
1
that is an object under inspection.
FIGS. 2A and 2B
show the effect of side light
6
a
and vertical light
6
b
respectively. As shown in
FIG. 2A
, when the side light
6
a
is projected on a component
2
, catoptric light
8
a
reflects sidelong from the horizontal surface of the component
2
, but part of the catoptric light
8
a
reflects vertically upward from the slope where solder
4
is properly mounted. On the other hand, as shown in
FIG. 2B
, when the vertical light is projected on the component
2
, catoptric light
8
b
reflects totally from the horizontal surface vertically upward, but it is not the case from the slope.
FIGS. 3A and 3B
show the images of the substrate
1
under the side light
6
a
and the vertical light
6
b
respectively which are captured by a CCD sensor provided above the substrate
1
. As shown in
FIG. 3A
, the image similar to a photograph copy is captured under the side light
6
a
, and it is comparatively easier to detect a solder bridge across the lead parts of the component, that is, the implementation defect which causes the solder to short-circuit the multiple leads, and a polarity mark on the component which indicates the position and the direction of the component. On the other hand, as shown in
FIG. 3B
, the high contrast image is captured under the vertical light
6
b
, and the edge part of the components and the slope part of the soldering appears black. Therefore, it is relatively easier to judge a shift in the location of the components, the absence of the component, and whether solder is properly attached to the electrodes or leads of the component.
As the demand for the appearance inspection apparatus grows increasingly, the inspection speed is still a general problem to be overcome in this field. As a matter of course, the requirement for the accuracy of the image recognition is becoming greater and greater.
SUMMARY OF THE INVENTION
The present invention has been made by the applicant in recognition of the above and an object thereof is to provide an appearance inspection technology which is able to meet inherently antinomy in requirements of processing speed and inspection accuracy, and component technology thereof. Another object of the present invention is to further improve the above-mentioned technology proposed by the applicant of the present invention.
An aspect of the present invention relates to a scan head. The scan head for scanning an object under inspection comprises a vertical light source which projects light on a surface of the object from right above, a line sensor which detects catoptric light that reflects vertically upward on the surface, and a lenticular sheet which is inserted between the vertical light source and the object and has a lens surface and a non-lens surface. The lenticular sheet is arranged in a manner such that the lens surface faces to the object and a direction of lens gouges in the lens surface and a scanning direction in the line sensor are nearly orthogonal. Herein, projecting light on the surface of the object from right above means projecting light at an almost zero incident angle onto the surface under inspection. The catoptric light that reflects vertically upward on the surface means light reflected at an almost zero reflection angle from the surface. Namely, the vertical light and the catoptric light pass along almost the same optical axis. Note that strictly speaking, the words of vertical light strictly means the light projected at a zero incident angle, but in this specification the vertical light may have a width from the zero incident angle at a certain degree according to the actual situation of the apparatus.
For instance, the vertical light source may be in a one-dimensional shape and placed in parallel to the line sensor. The line sensor may be a CCD sensor or any other image capturing sensors. The scanning direction in the line sensor means the direction along the long side of the sensor and it is generally orthogonal to the direction of the relative movement of the sensor and the surface under inspection. In the following, the direction of the relative movement is also referred to as a driving direction in this specification and it is discriminated from the scanning direction. The lens used in the lenticular sheet may be in general a cylindrical lens, but any equivalent thereof can be used as long as it has a similar effect in the present invention.
In this aspect of the present invention, it is possible that the light from the vertical light source refracts in the lens surface of the lenticular sheet and the light component vertical to the surface under inspection is stronger than other components. Consequently, the inspection under the vertical light can be performed more accurately.
The lenticular sheet may have a shade material with a line shape attached to the non-lens surface, the shade material being in a position at an opposite side corresponding to each of the lens gouges. In this case, as described later, the lenticular sheet works in a manner such that it can block off light components other than the light vertical to the surface under inspection. Therefore it can contribute to the improvement in the inspection accuracy under the vertical light.
Another aspect of the present invention also relates to a scan head. The scan head has a different configuration in the
Akiyama Yoshihiro
Iwano Yukio
Mack Ricky
Saki Corporation
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