Abstract:
An iris diaphragm includes shutter blades moved by a conventional control member during a first phase of adjustment to reduce the aperture to a size at which diffraction effects are still unimportant. In a second phase of adjustment the shutter blades are stationary and a transparent support member is moved to introduce increasingly dense portions of a graduated filter into the optical path. Light control over a range of 1:1,000,000 may thus be obtained. There may follow a third phase in which the shutter blades again move to reduce the aperture to zero. The blades and the filter support may be placed on opposite sides of a permanent stop and actuated by respective control members coupled to a common setting ring. Alternatively the blades and filter support may be on the same side of the stop and actuated by a common control member. The filter support may be introduced into the optical path only after the first phase has ended, or a transparent portion thereof may be always in the optical path, the filter-carrying portion being brought into action only during the second phase.
Abstract:
A coarse and fine adjustment device especially for focusing a lens system in which both the coarse and fine adjustment are transmitted by two levers pivotally connected together. The coarse or fine adjustment levers are moved by control means which may comprise screw-threaded pins, cam surfaces or an inclined plane acting upon the levers. Only one of the levers is in actual contact with the element to be moved.
Abstract:
Relative movement between two members is sensed by a device yielding a signal during successive increments of movement. A first circuit means applies one pulse to a reversible counter for each incremental movement and a second circuit controls the direction of counting to accord with that of movement.
Abstract:
TWO PRESENT INVENTION IS CONCERNED WITH APPARATUS FOR DETERMINING THE ORIENTATION OF AN OBJECT RELATIVE TO A SYSTEM OF REFERENCE AXES, SAID SYSTEM COMPRISING TOW PLANE REFLECTING SURFACES WHICH ARE DISPOSED AT 90* TO EACH OTHER, ARE FIXED RELATIVE TO THE OBJECT AND ARE ARRANGED TO RECEIVE AN IMAGE FROM A FURTHER PLANE REFLECTING SURFACE WHICH IS PIVOTALLY MOUNTED ON A THEODOLITE, A COLLIMATOR WHOSE OPTICAL AXIS IS DIRECTED TOWARDS SAID FURTHER REFLECTING SURFACE, A TELESCOPE WHOSE OPTICAL AXIS IS PARALLEL TO THAT OF THE COLLIMATOR AND WHICH WILL RECEIVE THE IMAGE OF THE COLLIMATOR RETICULE AFTER REFLECTION AT THE THREE SAID REFLECTING SURFACES WHEN SAID FURTHER REFLECTING SURFACE IS IN A PLANE PERPENDICULAR TO THE LINE OF INTERSECTION OF THE PLANES CONTAINING SAID TWO REFLECTING SURFACES, AND MEANS FOR DETERMINING THE POSITION OF SAID FURTHER REFLECTING SURFACE ON THE THEODOLITE.
Abstract:
Apparatus yeilding an electrical signal representative of the position of a boundary line between adjacent light and dark zones, with respect to a reference position, comprises two photoelectric cells having a separation in the direction in which the boundary moves. Means are provided whereby the output P1 of that one of the photocells which is last reached by the boundary during its movement is multiplied by a constant k, yielding a signal K.P1 which, together with the signal P2 from the other photocell, is applied to a difference amplifier providing an output signal which passes through zero when K.P1 P2. This signal may be applied to one input of a second difference amplifier, receiving also an output of a third differential amplifier providing a negative signal whenever P2 is less than a predetermined value. The final output signal may be applied to control traversal of the assembly including the two photocells, so as to obtain a measure of the boundary displacement.
Abstract:
Apparatus for indicating and/or controlling the exposure time of photographic material exposed to the electron beam of an electron microscope includes an electron impermeable, insulated conductive screen which may be positioned to intercept a part at least of the electron beam. The current flowing to the screen may be measured to indicate required exposure time. Alternatively the voltage across a resistor in the current path may be stored and integrated to yield a signal for indicating that exposure should be terminated. The signal may be used to produce termination of exposure.
Abstract:
Counting errors are automatically detected in a displacement measuring system using encoding and counting by sensing a value CL and substracting it from a value CE registered by a counter. The difference of the values is memorized at the beginning of measurement and is then continuously compared with the memorized difference. Non-coincidence between the instantaneous difference and the memorized difference actuates an alarm.
Abstract:
In an electron microscope having a velocity filtering system involving reflection in a prism, the normal objective lens is replaced by a complex lens comprising three electrostatic lens elements. This arrangement enables the order of image and diffraction diagram in the propagation path to be reversed, so that the diffraction diagram can be filtered as well as the image.