The following is an example of a medical endoscope, which we designed specifically for inspecting the inner esophageal lining. This optical design is very small and may easily be adapted or scaled up in size for other hollow-cavity inspection applications.

The basic mode of operation of this imaging system is to form an annular image on a focal plane of the entire 360-degree panoramic object formed by the inner esophageal lining.

This is a catadioptric imaging system: it comprises both reflective mirrors and refractive lenses. The design is very simple and extremely compact. It allows imaging all the way out beyond the "horizon" line of the lens (out beyond a typical lens' 180-degree FOV). There is no image formed of anything straight out in front of the lens, so it is very will suited to imaging inside hollow tubes, such as the esophagus.

Our panoramic endoscope system measures just 7.10mm diameter to the outside of the protective window, and it uses an Aptina WLC CMOS image sensor - one of the world's smallest cameras available. The single-piece construction of the Contrast proprietary panoramic lens makes it very easy to produce, either by diamond-turning or by molding from plastic.

The entire imaging system, from the front of the panoramic lens to the image sensor plane, measures just 7.35mm long.

The protective window, shown in a cutaway view above, is actually a cylindrical glass tube measuring 8.0mm OD by 6.0mm ID.

The animated figure above shows the size of our entire system, including the actual Aptina CMOS image sensor housing, relative to the size of a U.S. dime. For reference, a dime measures just 17.91mm diameter.

Our panoramic endoscope system features very good image quality, as shown in the figures below:

 

The MTF and spot diagrams above show that the Contrast panoramic lens offers very good image quality, all the way out to 100 line-pairs per millimeter, across the entire object field range, which covers a 4.0mm tall strip and wraps 360-degrees around the lens.

The figures below show an example of the imaging properties of this panoramic endoscope lens. The first figure shows a sample image target, which comprises a grid pattern inside a tube that measures 8mm diameter by 4mm long, in relation to the imaging system.

 

Finally, the figure below shows a simulated image of this tube-shaped grid pattern that is captures on the Aptina CMOS sensor. Note that the image is annular in shape and accurately images the entire 360-degree panorama of the inside of the target tube (8mm diameter by 4mm long).

 

 

 

SUMMARY

We designed a custom panoramic endoscope for use in a medical imaging application. Contact us to learn more about how Contrast Optical can solve your optical design problems.