2011

Device Measures Quality of a Laser Beam and its Illumination Field

This device measures laser illumination in applications such as imaging systems.

Laser line illumination systems may be used for numerous applications including imaging systems in which the laser line is directed toward a light modulator to reflect or transmit specific portions of the illumination field. The modulated light is then directed to an imaging surface. It is desirable that the laser line yield an illumination field that is uniform in peak power, power distribution, and spot size throughout the illumination line. If not, imaging errors result.

Laser Line Detection Device, the light of the laser source is led through an optical filter, and passed through two perpendicular movable slits. The second slit is on a rotating cylinder that scans the light characteristics for every vertical position of the first slit, thus composing a complete characteristic recorded by a fixed sensor." class="caption" align="right">This detector allows testing of the output characteristics of a laser line source before accepting it in an apparatus. The device measures the characteristics of a line of laser illumination and determines uniformity of total and peak energy, uniformity in spot size, in focal points, and in threshold values, as well as the length and width of the illumination line. To this end, the light of the laser source is led through an optical filter, and is subsequently passed through two movable slits that are perpendicular to each other. The second slit is on a rotating cylinder that scans the light characteristics for every vertical position of the first slit, thus composing a complete characteristic recorded by a fixed sensor. The device allows the rapid quality determination of new laser sources.

The apparatus leads the laser light through a filter, such as a 99% reflecting mirror, to reduce the amount of light received by the sensor. The filtered line is then passed through an aperture that is vertically movable. After passing through this first aperture, the laser light goes through a second perpendicular aperture, rotating in a horizontal plane. Typical dimensions would be 150 micrometers wide by 3 mm in length for the first aperture, while the second rotating slit may be 1 micrometer wide and 3 mm long and is positioned at or near the focal plane of the laser line.

For every vertical position of the first aperture, a complete rotation is made with the second slit, and is registered by a fixed CCD sensor. In this fashion, a complete scan of each portion of the line illumination field is recorded. The sensor measures peak energy and total energy across the width of the line segment. One way of representing the measurements is by a composite illustration of the illumination line where the amount of energy in the different areas falls between set threshold values.

This work was done by Agfa-Gevaert Group, and is available through the yet2.com technology licensing marketplace. For more information, visit http://info.hotims.com/34459-124.

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