Bench mount optical comparators are smaller units than floor mount, with screen sizes from 12″ to 16″. Horizontal models have a horizontal path of light. The object being inspected is held in a vertical position on a stage or platform. The light source is near the operator pointing to the instrument lens. The object can be located on a strong platform, therefore heavy objects can be inspected.
Vertical models have a vertical light path. The light source is in the base of the comparator pointing upward to the lens. The object being inspected is placed on a glass surface which covers the light source. The weight of objects can not be as great as with horizontal models. Their primary use is in profile, edge, and dimension measurement of thin or flat objects.
Image is one of the most important features in selecting an optical comparator. All magnifying lens systems turn the vertical axis upside down and the horizontal axis from left to right. It requires some training to interpret the image. Most manufacturers offer some image correction. The most common is the vertical (or erect) image. This corrects the vertical axis, but leaves the horizontal axis reversed. For some models, only the horizontal axis is corrected. The most sophisticated systems provide a corrected image.
Travel: The object is placed on a stage which has a range of travel in the horizontal (X direction) and the perpendicular (Y direction). All manufacturers offer a number of stage sizes as options. This listing states the largest stage available. Some manufacturers provide this stage as standard, some require that any stage be listed as an option. The smaller stages usually go with higher magnification lenses and provide more accurate measurements. The standard stages are manually operated. Motorized and CNC driven stages are available as options for most models.
Magnification Lenses: The magnification lenses available are 5x, 10x, 20x, 25x, 31.25x, 50x, 62.5x, 100x, 200x, 500x. Each manufacturer has a range available that will vary by model. This list states the smallest to largest magnification for a given model. Some manufacturers provide the 10x lens as standard, while some require that the lens be purchased separately.
Resolution is the smallest increment readable on the optical scales provided. All manufacturers offer digital readout as standard. RS 232 and other digital outputs are an option.
Maximum Sample Weight is the maximum load that the stage can handle and still perform reliably.
Focus Travel is the distance that the stage can travel to bring the edge or a point on a surface into focus. Some manufacturers state a maximum value. However this number varies with the lens magnification. The greater the magnification, the smaller the field of view and the shorter the depth of field and focus travel.
Lens Mount: This is the fitting of the lens and is either bayonet or thread type.
Lens Turret: Some manufacturers have a three lens turret as standard. Some offer it as an option. The turret allows quick change of magnification.
Light Source: This parameter is not listed, because all models are equipped with 150 watt halogen bulbs. All manufacturers provide optical fiber bundles for surface illumination.