GB945320A - Improvements in photomicrographic apparatus - Google Patents

Abstract

945,320. Photomicrographic apparatus. C. REICHERT OPTISCHE WERKE A. G. March 10, 1961 [ March 10, 1960], No. 8950/61. Headings G2A and G2J. [Also in Division G1] A photomicrographic apparatus comprising an optical lens system for directing image-formforming light rays towards a shutter operable by energization of an electromagnet and by an electric timer device arranged to control the duration of energization of said electromagnet and consequently the duration of opening of said shutter, includes an optical beam-splitter in the path of said rays for deflecting a fixed proportion of said rays capable of forming a visible image of an eye retina and means for adjusting the illumination of a comparison field coincident with said visible image, said adjustable means including a light alternating device adjustable to control the proportion of light reaching said field from an external light source, and said timer device including a time setting member mechanically coupled to said light attenuating device so that the duration of opening of the shutter is related to the adjustment of said light attenuating device in such manner that the product of the illumination of said comparison field and the duration of opening of the shutter is constant. As shown, image-forming light from a microscope (only barrel 1 of which is illustrated) is directed through an electromagnetically operated shutter 3 to a camera 4. Part of the light beam is directed by a prismatic beamsplitter 2 through a lens 5 and is focused on to a ground-glass screen 7, the visible image produced thereby being observed through a lens 8. Light from a lamp 9 is also directed by a lens 11 and a mirror 12 on to the screen 7 to form a comparison field, the brightness of which may be varied and made equal to the surrounding visible field by adjusting the position of a neutral wedge filter 10. For this purpose, filter 10 is coupled through a rack 15 and a pinion 14 to an adjusting knob 13. The knob 13 is coupled by way of its shaft 16 to a rotary switch 18 having resistors 19 coupled to an electrical timer 17 for operating the shutter 3. To allow for film sensitivity or other exposure factors, the pinion 14 is adjustably coupled to the knob 3 and shaft 16 in that (as shown in Fig. 3) a bushing 21 rigid with pinion 14 carries a leafspring 20 bearing a projection 22 which is engageable in any of a number of holes in a flange 23 of the knob 3, a manually operable projection 24 being provided on the leaf spring and a scale 25 of film sensitivities being provided on knob 13 for cooperation with a fixed index 26. Alternatively, such factors as film sensitivity may be allowed for by inserting an additional light attenuating device into the path of rays passing through lens 5 or by adjusting the intensity of the light source 9.