Abstract: A method for automatically focusing on a slide includes the steps of locating a coverslip, acquiring images from predetermined focal depths in the slide, and starting at an initial focal depth proximate the surface of the coverslip. A set of predetermined characteristics within each of the images are measured to generate at least one image measurement for each of the plurality of images. A focus measure is computed for each of the images, where each focus measure is a function of at least one image measurement. A best focus location is determined relative to a focal depth where an acquired image has a highest focus measure.

Abstract: Accurately measuring and controlling the system transfer function of an imaging system, by eliminating interference from aliases. An image is captured of an image primitive with a uniaxial pattern, oriented at an angle to the primary axes of a sampling array. In order to accurately measure the system transfer function, a two-dimensional frequency representation is computed. The aliased components of the representation are separated from the unaliased components by translation in frequency along the axis perpendicular to the axis of the image primitive. Accurate measurement of the system transfer function makes it possible to accurately control the system transfer function.

Abstract: An automated apparatus for checking cytological system image collection integrity in an automated cytological system including an imaging apparatus controlled by a digital processor. The automated apparatus includes linearity checking apparatus, coupled to the imaging apparatus and the digital processor. System frequency response is checked using a modulation transfer function, where the sampling frequency may be determined by pixel size so as to allow the MTF to be determined beyond the sampling frequency of a system detector. A system signal to noise ratio is also checked for specific regions of the frequency spectrum.

Abstract: An automated method for checking cytological system autofocus integrity. The automated method includes the steps of checking focus illumination integrity, checking focus camera Modulation Transfer Function, checking focus camera position integrity, and checking closed loop accuracy. Checking focus illumination integrity includes checking focus illumination system integrity, and checking a focus noise floor level. Checking focus camera position integrity includes checking focus camera longitudinal separation, and checking focus camera lateral separation. Checking focus camera position integrity includes checking focus filter frequency response.

Abstract: A circuit is provided for correcting an image signal received from a camera wherein the camera includes a plurality of charge coupled devices, each for providing a light signal indicative of the intensity of light incident thereon and wherein the plurality of light signals from the plurality of charge coupled devices are indicative of an image received by the camera. The correction circuit includes a gain memory for storing a plurality of gain correction factors wherein each gain correction factor is associated with a respective charge coupled device of the camera. The correction circuit further includes an offset memory for storing a plurality of offset correction factors wherein each offset correction factor is associated with a respective one of the plurality of charged coupled devices. The gain memory is responsive to a control circuit for multiplying the plurality of electric signals by the appropriate gain correction factor.