Radiant energy – Photocells; circuits and apparatus – With circuit for evaluating a web – strand – strip – or sheet
Reexamination Certificate
1999-10-29
2001-09-18
Allen, Stephone B. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
With circuit for evaluating a web, strand, strip, or sheet
C359S399000, C702S150000
Reexamination Certificate
active
06291830
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to an optical position alignment sensor for aligning electronic components, which is used in the electronic component placement industry. Machines of the type used in the electronic component placement industry are sometimes called pick and place machines.
Electronic shadowing techniques incorporated in optical-based sensors are in widespread use today in the electronics industry in pick and place machines for mounting electronic components on printed circuit boards. One of the most commonly used position alignment sensors is manufactured by CyberOptics Corporation in Golden Valley, Minn. and is sold as a LaserAlign® component alignment sensor. LaserAlign type sensors use a light source focused into a stripe of light, which is typically incident on the side of an electronic component, thereby forming a shadow which is cast onto a detector. When the electronic component is rotated (by a nozzle controlled in x, y and z direction by the pick and place machine), the shadow cast on the detector changes in width.
The orientation process is generally carried out while the pick and place machine is transporting the component to a target printed circuit for placement. When the orientation process is carried out simultaneously with the transport of the component, the orientation process is sometimes referred to as an “on-head” or an “on-the-fly” measurement. Conversely, “off-head” measurements are made when the sensor is not affixed to the pick and place head but rather, is stationary relative to the head.
One of the problems typically not addressed by the prior art is a position alignment sensor for aligning at least two components which prevents undesirable glints (i.e., reflections), both large and small angle, from interfering with accurately orienting either of the components.
SUMMARY OF THE INVENTION
The present invention includes a method and apparatus which reduce two types of undesirable glints (small and large angle glints) in an optical position alignment sensor designed to orient at least two components. The method includes shining a plurality of rays of light onto the components, the rays directed generally perpendicularly to a central axis of each of the components where each of the components block the rays to cast a shadow of the outline of the components. Some of the rays of light are specularly reflected from one of the components to provide a large-angle glint, which is the first type of glint reduced by the present invention. The method then passes the rays of light through an optic with positive power so as to focus the two shadows at a focal point, the optic focuses an image of the shadows at a component plane located behind the focal point. An aperture is positioned substantially at the focal point and an opening in the aperture is positioned to allow the rays of light to pass therethrough except for the large-angle glint. The combination of the positive optic and the aperture prevents the large angle glint from reaching the detector. A detector is positioned behind the component plane and a plane of the detector is positioned parallel to the plane of the optics, so that an unfocused image of the shadows falls on the detector. The placement of the detector behind the image of the component plane reduces the effect of the small angle glint of the present invention.
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patent: 8-111598 (1996-04-01), None
patent: 9-214198 (1997-08-01), None
patent: 9-210626 (1997-08-01), None
Allen Stephone B.
CyberOptics Coporation
Westman Champlin & Kelly P.A.
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