Abstract: An automatic focusing apparatus of a peak stop system adapted to perform focusing adjustment by: measuring contrast while moving stepwise an objective lens or an object in a direction of a focal point along an optical axis of the objective lens with a certain pitch width from a reference point to store the contrast measured at each position during the movement into a memory: comparing a difference between the contrast value measured at a present position where the objective lens or the object has been just moved and the contrast value stored at each position where the objective lens or the object has been already moved, with a preset judgment value; and judging that the position of the maximum contrast (the focal point) has been passed in relation to the gradual movement with the above pitch width when each of compared results is a positive value at each position, in order to make it possible to detect accurately the position of the maximum contrast, disregarding sub-peaks of the contrast.

Abstract: In order to be suited for long-term use in an enclosed space and to enable various modes of illumination by simple procedures and at a low cost without adding special optical components, the illuminating device for microscopes of the invention comprises a surface light source including a plural number of semiconductor light sources arranged in two dimensions, a control circuit selectively lighting some or all of the plural number of semiconductor light sources in conjunction with selection of an illumination mode, and an optical system for condensing and transmitting the light from the surface light source. The illuminating device of the invention makes it possible to observe a sample simultaneously in different illumination modes when the illuminating device is equipped with three surface light sources and the sample is irradiated simultaneously with the lights from the three surface light sources.

Abstract: A schlieren optical device using diode emitting monochromatic light as spot light source so as to have a compact and light-weight design, low calorific power, and low power consumption, and assure high reliability. In said optical device, imaging lens consists of a pair of lens groups arranged with an airspace reserved therebetween, knife edge consists of a light-shielding coating arranged on the surface of one of said lens groups and the other lens group is displaceable along the optical axis. Said optical device comprises a schlieren optical system and an optical system of a transmission type of microscope having optical axes perpendicularly intersecting with each other at the position of a sample, or a pair of schlieren optical systems and an optical system of a transmission type of microscope having optical axes perpendicularly intersecting with one another.

Abstract: A heater for microscopes for heating a sample and maintaining the sample, which is mounted on a platform of the microscope, at a preset temperature during observation of the sample. The heater includes a platform for supporting thereon a sample container and a heater for heating at least part of the platform. A first heater box is fitted, open end down, over the platform and is connected thereto to form a first space which surrounds the sample container. A second heater box is then fitted over the first heater box in such a manner that a second space which surrounds the first heater box is formed. Heater means are provided for heating the second space. Accordingly, the temperatures in the first space and in the second space can be controlled independently to achieve better control over the temperature of the sample which is to be observed and to control condensation which may otherwise form in the sample holding container.