(Not Applicable)
(Not Applicable)
The present invention generally relates to an illumination head for printed circuit board verification and more particularly to an illumination head that may be disposed a prescribed distance above the printed circuit board in order to facilitate rework thereon.
In order to inspect printed circuit boards, it is desirable to illuminate the same with an illumination source. Typical illumination sources include rings of light and/or spotlights which direct light onto a top surface of the printed circuit board. In this regard, once the top surface of the printed circuit board is illuminated, the printed circuit board may be inspected through the use of a video camera and/or automated inspection technique.
It is desirable to illuminate the top surface of the printed circuit board such that shadows and/or glare which can impair inspection are eliminated. Therefore, in the prior art, the illumination head for an inspection station is disposed in close proximity to the top surface of the printed circuit board.
It is undesirable to have the illumination head disposed in close proximity to the top surface of the printed circuit board because reworking of a defective circuit board is difficult. Specifically, during inspection of the printed circuit board, the operator of the inspection station must determine where imperfections in the printed circuit board exist. Upon identifying such imperfections, the operator marks the imperfections and then removes the printed circuit board from the inspection station in order to rework the circuit board. Because the illumination head is positioned in close proximity to the top surface of the printed circuit board, the operator of the inspection station cannot effectuate repairs to the printed circuit board. Accordingly, the operator must mark and remove defective printed circuit boards in order to rework the same. Once the defect has been marked, rework on the printed circuit board is effectuated on another machine.
The present invention addresses the above-mentioned deficiencies in inspection stations by providing an illumination head for an inspection station that may be disposed 4 to 6 inches above the top surface of the printed circuit board and still generate a clear image of the inspected part. In this respect, reworking of the printed circuit board may be accomplished at the inspection station which includes the illumination head of the present invention. Accordingly, an operator using an inspection station having an illumination head of the present invention may find defects on the top surface of the printed circuit board and rework the same without removing the printed circuit board from the inspection station.
An illumination head for an inspection and rework station. The illumination head has an optical axis and is operative to illuminate a part. The illumination head comprises a backlight having an aperture formed therein which is coaxially aligned with the optical axis of the illumination head. Further, the illumination head comprises at least one lightline disposed adjacent to the backlight. The backlight is operative to direct light onto the part along the optical axis and the lightline is operative to direct light onto the part at an angle incident to the optical axis. Accordingly, the illumination head may be disposed a prescribed distance above the part (i.e., typically four to six inches).
In accordance with the present invention, the aperture of the backlight may be circularly configured and the illumination head may further comprise an annular ringlight disposed between the backlight and the lightline. The ringlight is coaxially aligned with the aperture and operative to direct light onto the part along the optical axis. The lightline typically comprises two lightlines disposed on opposite sides of the illumination head. The illumination head may further comprise an iris coaxially aligned with the optical axis and configured to selectively regulate the level of illumination directed onto the part.
The illumination head constructed in accordance with the present invention may further include a viewing device coaxially aligned with the optical axis and operative to generate an image of the part through the aperture of the backlight. The viewing device may be a CCD camera.
In the preferred embodiment, the backlight is a translucent sheet configured to transmit light. The backlight is in optical communication through at least one optical fiber with a light source operative to illuminate the backlight. Similarly, the lightline may comprise a plurality of optical fibers disposed in substantially parallel relation to one another and operative to direct light upon the part at an angle incident to the optical axis.
In accordance with the present invention, there is provided a method of illuminating a part with an illumination head having an optical axis, a lightline, and a backlight. The method comprises illuminating the part with light directed at an angle incident to the optical axis with the lightline and illuminating the part with light directed along the optical axis with the backlight such that the illumination head is disposed a prescribed distance above the part. The method further may include coaxially aligning the aperture with the optical axis prior to illuminating the part.
In accordance with the present invention, the illumination head may further comprise an annular ringlight coaxially aligned with the aperture such that the method further comprises illuminating the part with light directed along the optical axis with the ring light. Additionally, the illumination head may further comprise an iris coaxially aligned with the aperture such that the method comprises controlling an amount of illumination from the backlight and the ringlight with the iris.