Abstract: In a system in which the tomographic image of an object under investigation is produced on the basis of the amount of absorption of radiation by the object when a source of radiation and a plurality of radiation sensitive detectors with the object interposed therebetween are rotated around the object, the output signal from at least one of the plural detectors is used to correct the radiation absorption amount. Another selected one of the plural detectors may be used for checking whether the object is positioned within a useful detection view.

Abstract: A tomographic imaging system is disclosed in which the quantity of absorption or transmittance of a transmissive radiation by or through a certain tomographic cross-section of an object under consideration is detected and the distribution of radiation absorption or transmittance in the cross-section is reconstructed through a convolution operation. A weighting function used in the convolution operation is prepared with a predetermined one of its positive orders the value of which is an integration of the weighting function from the predetermined positive order to positive infinity and a predetermined one of its negative orders the value of which is in integration of the weighting function from the predetermined negative order to negative infinity.

Abstract: A leukocyte detector comprises a first and a second filter means adapted to select color components with different wave lengths, or green and blue color components, respectively, from the microscopic image of a stained blood smear, a first and a second opto-electric converter means for converting the transmitted light from said first and second filter means into corresponding electrical signals, a subtractor for subtracting the outputs from said first and second opto-electric converter means, and a comparator which compares the output of said subtractor with the predetermined threshold limit value.

Abstract: A signal separation system is used to discriminate cytoplasm of white blood cells from a sample of white blood. The signal separation system includes a light source generating light passed through a blood sample, a light separator for separating green and blue light beams from the light passed through the sample, first and second photoelectric converters for changing the green and the blue light beams to first and second electric signals, a signal treatment circuit which converts the first and the second electric signals to binary signals with respect to certain threshold levels and then forms a separation signal from the binary signals, and the gate circuit which separates the signal component of the white blood cells from the sample with the function of the separation signal.