Letter | Published:

An Image-Splitting Microscope for Accurate Measurement


AN instrument has been devised for the very precise measurement of small objects, such as thin wires, blood cells or the like. The principle involved, which is a century and a half old, is that of the heliometer. The image is split into two complete images which may be sheared across each other by operation of a suitable control. The two images of the object are set edge to edge, an adjustment which is capable of great accuracy, and the amount of shear involved is read off from a suitable scale. The shear is then reversed, crossing the two images over and setting them edge to edge once more. The difference between the two readings of shear is proportional to the diameter of the object and can be calibrated by means of a ‘stage micrometer’.

Access optionsAccess options

Rent or Buy article

Get time limited or full article access on ReadCube.


All prices are NET prices.

Author information

Rights and permissions

Reprints and Permissions

About this article

Further reading


By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.