American Optical History  -
AO Scientific Instruments History

The AO Lensometer
Note "Lensometer" was an AO Trademark name

AO Promotional photo (~1920) for the first marketed AO Lensometer which was first sold in 1921;
the principal by which we still measure lenses today. In 1916, AO began using the Lensometer in its factory/ branches.
In 1917, it line of Centex lenses was introduced
which were designed by effective power (now the Industry Standard).

Early "AO Lensometer" related measuring devices

This website page shows the lineage of the AO Lensometer over time, an instrument which
is still one of the most important devices in the Ophtlamic Industry today.

Dr. Tillyer in the image above from a 1918 Booklet on the Lensometer
Download this first booklet (4mb pdf)

Download the AO 1938 Booklet about this model, and the complete background
of the AO Lensometer up until then. It was written by Dr. Estelle Glancy

1914 AO Lensometer which predated the first device sold in 1921

Early Lensometer (Serial #002) - 1921
AO Optical Heritage Museum Collection

AO "Wellsworth" Lensometer ad from Febrary, 1922 showing Doc Tillyer measuring a lens

A look at the early development/ timeline of AO's Lensometer (Left image below)

Model 603 from 1938 - The Junior AO Lensometer (at right above)

Information on WWII and AO Lensometers used in the war (bottom link)

AO Lensometer Catalogues from 1947 (L)- list price $310 and 1958 (R)- list price $435

1952 Instructions / Manual & Maintenance Booklet
Download pdf (10mb)


1956 AO Electronic Focusing Lensometer by Whitney/Haynes/Gunter

AO Lensometer Catalogue - 1959  (above)

A simple diagram of the principal used in the AO Lensometer to measure tranmission dioptric power of a spectacle lens.
This is from Don Whitney's 1981 Optics training slides that he compiled for a course given at that time.

1977 Brochures of two popular AO Lensometers

Download AO 12603 Lensometer Brochure

Download AO 12620 Lensometer Brochure

AO Lensometer Blueprint - 1971

Specialized AO Lensometers
The one shown below was used to develop the AO Tillyer Masterpiece lens series; Ina Pasay Dawson is shown here using this device in the 1970's.
This device was built a couple 1-2 decades before. It permitted one to measure off-axis tranmission power of the lens,
to determine the optical errors the eye would see as the eye rotates away from optical center.

This device among the many AO Lensometeres from the Optical Heritage Museum collection.

Download complete AO Masterpiece Lens brochure from 1968 (excerpts above)

The device below (1977) used a  modified in AO 12603 Lensometer to accomplish the same thing as the "Masterpiece Lensometer" above. It permitted one to rotate a lens (using set center of rotation distances) to similuate the eye motion away from optical center. With this rotation, power errors and prism retulted. To measure these errors, the telescope was rotated as shown to determine whether the design / fabrication met AO and Industry Standards at that time.  ANSI Z80.1 -1972 required lenses to meet specific off-axis tolerances for power errors.

Download the AO SLP that I wrote  in 1979 on how to use

AO Lensometer Calibration Lenses

This is the AO primary true-power lens set Calibrated by Doc Tillyer when he worked at the National Bureau of Standards prior to joining AO.

Each lens was measured for its refractive index (a sliver taken from the edge). The curves were measured and then the resulting power calculate.
Two lenses were re-certified in 1977 and had not changed. It is this set by which all AO Lensometers were originally calibrated.

The set (and another secondary set) is part of the Optical Heritage Museum collection.

Blair Wong (Ben Franklin Institute of Technology - Opticianry Dept Chair & Exec Director of MA Opticians Assocation
and Diane Matuck (Board of MA Opticians Assocation) examine the AO NBS set from 1916.

1977 AO Lensometer calibration lens set ad above and two below today.


This AO Lensometer was modified ~ 1987 and used to check the reflected image of Progressive Lens mold engravings;
it was not used for Transmission measurements, but was a clever and accurate way to examine engraving quality.

May 2009 Lensometer Display (courtesy of the Optical Heritage Museum)
at the Southbridge Hotel and Conference Center

Past Display in Downtown Southbridge storefront window

1900 - Trial Lens Sets

AO produced a trial lens set design by Charles Prentice. This set was composed of biconcave minus lenses of true curve out the convex plus lenses were designed to neutralize the minus lenses. This meant that the lenses were almost exactly true vertex refractions or effective power. The first lenses so made. This principle is still used in our trial lens sets. Only the rings & cases have been updated.

Optical Heritage Museum collection-

AO Gift to Charles Prentice (1920) but still his basic design

More about AO Scientific Instruments achievments/timeline

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