Quality Magazine

Microscope Retrofit Enlarges Eyepiece

May 19, 2003
For microscope users who wear eyeglasses or those who suffer from eye or neck strain, a new enlarged eyepiece just might be the answer.

Called ISIS, the technology is a retrofit accessory that replaces traditional eyepieces on stereo and research microscopes. The unit slides onto the host microscope tubes in the same way as the original OEM eyepiece, but provides a wider field of view. The ISIS eyepiece is priced at $1,700 and is targeted for use with microscopes from such suppliers as Leica, Nikon, Olympus, Zeiss and Wild, said Mark Rocha, marketing manager for Vision Engineering (New Milford, CT).

The ISIS uses multi- lenticular technology that includes a transparent lens that is 83 millimeters in diameter and generates an exit pupil 12 Arial greater than the light delivered to conventional eyepieces. The lens contains more than 2 million miniature lenticular lens-shaped elements, each about 70 microns in size, and rotates at 3,400 rpm. When the lens spins, the millions of individual optical paths are merged to produce an aberration-free, high-clarity image, said Rocha.

The ISIS extends the distance from the microscope to the eye by 38 millimeters. With traditional eyepieces, the movement of a pupil can blur the image because the pupil moves beyond the narrow ray bundle produced by conventional technologies.

The ISIS, which is powered by a separate power supply that plugs into the eyepiece assembly, allows freer head and body movement. The operator does not need to look directly into the microscope; instead the operator can look into the eyepiece from a comfortable distance. The ISIS has an expanded light ray bundle, which means that the operators can move their eyes to the full image area in the viewer.

"Most microscope users have to sit in a rigid posture and the slightest movement of the pupil will cause them to lose the image," said Rocha. "You can not only move your pupil to some degree but can move your head and body around and work in a comfortable posture."

Also, microscope users who wear glasses do not have to remove them to look into the ISIS viewer.

"If you wear glasses you have to take them off to get a good image. Some microscopes offer high eyepoint eyepieces, however, eyeglass lenses may still get scratched because they make contact with the unit," said Rocha the viewer does not magnify the image. Also, even though the image is filtered through the lenticular lens, Rocha said that there is no loss in resolution.

"While the technology improves comfort without affecting image quality, ISIS also performs well with the speciality illumination techniques and camera options featured on the host microscopes."

Another distraction common to microscope operators is that of mouches volantes, or "floaters," in the eye. These are tiny tissue fragments that float in the eyeball fluid and can hinder microscope operations. The rotation of the lenticular lens eliminates this problem, said Rocha.

In addition, Rocha said there are no repeatability issues. "What the operator sees is what they see," he said. "The quality of the image is not going to change. The only thing that will change is whether the operator is comfortable or not."

What is a Lenticular Disc?
At the heart of Vision Engineering's patented Expanded Pupil Technology lies a transparent multilenticular disc, composed of numerous lenticules, which act as independent image forming surfaces with diameters of a few microns each.

Lenticular means that it is shaped like a lentil or lens. In Vision Engineering's Lynx Dynascope, the 148mm diameter multilenticular disc surface comprises of over 3.5 million individual lenticules (lenses), each measuring just 70 microns in size. The Dynascope disk spins at 3,400 revolutions per minute to merge the millions of individual optical paths, delivering a smooth expanded-pupil stereo image with a generous depth of focus and a wide field of view.

In use, the multilenticular disc serves to expand the intrinsic pupil of the system. The resultant image is reflected through the field lenses to the operator's eyes and the high-resolution image is projected onto a large viewing area for maximum viewing comfort.

As operators frequently alternate their views from the magnified object image to the actual object, especially when manipulating parts, the large distance to the apparent magnified image eliminates the need for the eyes to refocus each time which can reduce eyestrain and fatigue.

In addition, employing a viewer rather than eyepieces permits greater positional freedom for the operator and allows the use of spectacles. Operators who need reading glasses remove them for microscope viewing and must then re-focus at a different distance, which again quickly leads to eye fatigue. Operators with astigmatism fare worse because removing spectacles immediately spoils their vision.