| 摘要 |
An analog circuit for an autofocus microscope system measures a degree of focus of an object directly from the video signal of a microscope CCD camera . The circuit then returns an index to a host computer for the purpose of adjusting the position of the microscope's objective lens to bring the objec t in focus. Best focus ins found by comparing indices at several different vertical positions. The criterion adopted for determining the degree of focu s is derived from the energy distribution of the video signal spectrum. The signal passes through a highpass filter, a gate (to remove scanning artifacts), a squarer and an integrator. The high frequency energy of the video spectrum is a maximum at best focus and as the optics defocus, the distribution shifts to lower frequencies. Low cost, real time autofocus is achieved with the analog circuitry of this invention, replacing more expensi ve dedicated real time image processing hardware.
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