A simple variable prism with a linear scale.

ABSTRACT

PURPOSE: To build a simple, low cost, variable-power prism with a linear scale. METHODS: A sliding lens system, using the prismatic effect of ophthalmic lenses, was constructed. RESULTS: The system functions well at low powers using conventional curved form ophthalmic lenses. CONCLUSIONS: The sliding lens variable prism is a useful alternative to the conventional rotating variable-power prism.