Data processing: generic control systems or specific application – Specific application – apparatus or process – Robot control
Reexamination Certificate
2001-02-22
2002-05-07
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Robot control
C700S166000, C700S167000, C356S237100, C356S243100, C219S267000, C219S269000, C250S231120, C250S231140
Reexamination Certificate
active
06385507
ABSTRACT:
BACKGROUND OF THE INVENTION
The invention relates to an illumination module for illuminating an object to be examined, which module comprises an exit window for radiation generated in the module, a module axis which extends perpendicularly to the central part of the exit window, and a number of radiation-generating elements which are arranged in at least two illumination rings, which illumination rings have a midpoint, which is situated on the module axis, and are individually switchable, the radiations of the different illumination rings passing through the exit window at different angles with respect to the module axis.
The invention also relates to an optical device for the observation of an object, which device is provided with such an illumination module, and to an apparatus for placing electronic components on a support, which apparatus is provided with at least one such optical device.
At present, said apparatus is often used to automatically, very accurately and very rapidly place electronic components on a support, such as a printed circuit board (PCB). Said apparatus comprises one or more robots, provided with a suction pipette, and an equally large number of placement stations associated with the relevant robots. The suction pipette receives a component to be placed from a component input device, whereafter the associated robot transports the suction pipette and the component to a position on a support which, at that instant, is situated in the placement station. Before the component can be placed on the support, it has to be identified and inspected for irregularities, and it must be checked whether the component is correctly oriented with respect to, for example, a system of coordinates of the robot. To this end, the placement station is provided with an optical observation device for observing the component held by the suction pipette, which observation device is alternatively referred to as vision module. This device comprises a camera by means of which an image of the component is converted into electric signals which are electronically processed. A good observation device should meet the following requirements: the image must be free of distortion, the observation device should also be capable of imaging large components, the aperture angle of the beam with which the component is illuminated must be relatively small, and, for specific applications, the angle of incidence of the illumination beam on the component must be as large as possible. To properly observe the component, it is necessary for this component to be illuminated in the right way. To achieve this, the observation device comprises an illumination module.
Such an illumination module is described in U.S. Pat. No. 4,893,223. The known illumination module comprises a large number of light-emitting diodes, also referred to as LEDs, which are mounted on the inner surface of a concave plate and arranged in rings or angle sectors. Since the components to be placed by means of the placement machine may demonstrate different shapes and different surface conditions, the illumination module should preferably be programmable, i.e. it should be possible for groups of LEDs, such as the LEDs of a ring or the LEDs of a comer sector, to be switched on individually, so that the angle at which the object is illuminated and/or the part of the object that is illuminated can be adjusted. The illumination module described in U.S. Pat. No. 4,893,223 is used to illuminate the free end, which is provided with a solder ball, of the connection pins of a component, which is commonly referred to as surface mounted device (SMD). The observation device wherein this illumination module is employed, makes it possible to inspect only the end of one pin of the SMD. To inspect a subsequent pin, the observation device and the SMD are moved with respect to each other. Thus, the illumination module described in U.S. Pat. No. 4,893,223 has a small illumination field, and the angle between the beam of the LEDs and the normal to the surface of the SMD is relatively small. The beams supplied by the LEDs have a relatively small aperture angle, of the order of 10°. The illumination module in accordance with U.S. Pat. No. 4,893,223 is difficult to manufacture because all LEDs must be accurately aligned to make sure that they all illuminate the same small area.
BRIEF SUMMARY OF THE INVENTION
It is an object of the invention to provide a programmable illumination module having a wide range of applications, which can be readily manufactured and has minimal dimensions, and which, in addition, can be adjusted for a large illumination field, and which is capable of supplying a very oblique illumination beam. This illumination module is characterized in that all the radiation-generating elements are provided on a flat plate which extends parallel to the central part of the exit window, and the principal rays of all radiation beams emitted by the radiation-generating elements extend parallel to the module axis.
The fact that this module is capable of supplying a very oblique illumination beam means that selected radiation, originating, for example, from the outermost illumination ring, includes a very small angle, of for example at least 6°, with the illuminated surface of the object.
The provision, with great accuracy, of the radiation-generating elements on a flat plate is simpler than the provision, with the same accuracy, of said elements on a concave plate. The flat plate may be embodied so as to be a printed circuit board with electric conductors via which the radiation-generating elements are fed.
A preferred embodiment of the illumination module is further characterized in that opposite each illumination ring there is provided a radiation guide which, in a plane at right angles to the module axis, is ring-shaped in section, the entrance plane of said radiation guide being situated opposite the associated illumination ring, and the shape of the light guide is exit plane situated opposite the entrance plane being adapted to the desired direction of the radiation to be supplied by the associated illumination ring.
The use of these radiation guides enables the optimum illumination direction for a specific application to be achieved. The radiation guide associated with a certain illumination ring also makes sure that the radiation from said ring is not mixed with radiation from other illumination rings. Since the radiation from an illumination ring is confined to the associated radiation guide until it exits via the exit plane of this guide, the beams of the radiation-generating elements can have a relatively large aperture angle, for example in the range from 20° to 30°. In addition, the radiation guide ensures, via total internal reflections, that the radiation beam leaving the radiation guide demonstrates a certain degree of homogeneity. In this regard, the length of the radiation guide and the aperture angle of the LEDs of the associated illumination ring play a part.
To further increase the homogeneity, the illumination module is preferably further characterized in that the exit surface of all radiation guides, with the exception of the outermost radiation guide, is provided with a diffuse body the surface of which facing away from the radiation guides has such a shape that the radiation beam exiting from a radiation guide through this surface has a desired direction.
The radiation guides may be filled with air. Preferably, however, the illumination module is characterized in that the radiation guides, possibly with the exception of the innermost radiation guide, are filled with a transparent synthetic resin.
In accordance with a further characteristic, the synthetic resin is polycarbonate or polymethyl methacrylate. These synthetic resins, which are also known by the abbreviations PC and PMMA, respectively, are highly transparent and of good optical quality.
Preferably, the illumination module is characterized in that scattering particles are integrated in the synthetic resins.
If so, these synthetic resins have a diffuse effect, and the rel
Biren Steven R.
Cuchlinski Jr. William A.
Marc McDieunel
U.S. Philips Corporation
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