Radiant energy – Photocells; circuits and apparatus – Optical or pre-photocell system
Reexamination Certificate
2000-11-08
2001-11-13
Lee, John R. (Department: 2878)
Radiant energy
Photocells; circuits and apparatus
Optical or pre-photocell system
C356S614000
Reexamination Certificate
active
06316765
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a device for detecting the position of rotating objects, the device having an optical signal transmitter and an optical sensor.
Detecting the position of rotating objects, in particular, rotating shafts, is frequently performed in machine construction or engineering with the aid of reticles which rotate with the object and are evaluated by a sensor. It is thereby possible to determine the speed, position and, if appropriate, the direction of rotation of the rotating object.
Such devices, however, are not suitable for detecting position with high precision, such as is required, for example, in electronic reproduction technology when exposing recording material by an electronic recording unit, also known as a recorder or an image setter, in order to achieve a good recording quality.
A light beam modulated by an image signal is guided in a recorder over a recording material to be exposed in a punctiform and line-wise manner by a rotating light-beam deflecting device. In this process, the recording material is fixed on a holder which moves relative to the light-beam deflecting device. In order to attain a good recording quality, it is necessary to generate a reference pulse, by an exact position detection, by which the deflecting movement of the light beam and the transport of the recording material are synchronized.
A device for generating such a reference pulse has already been disclosed heretofore in the German Published Non-prosecuted Patent Application (DE-OS) 195 16 154. This known device has a fixed or stationary light source which generates a light beam directed onto a rotating object. The light beam is reflected by a mirror disposed on the rotating object onto a stationary optical sensor which generates an electric reference pulse at a defined angular position of the rotating object.
This heretofore known device, however, is also not adequately suitable for satisfying increased demands for accurate position detection.
SUMMARY OF THE INVENTION
It is therefore an object of the invention of the instant application to provide an improvement in a device for position detection so as to ensure that a position is marked accurately with a device having a simpler construction.
With the foregoing and other objects in view, there is provided, in accordance with the invention, a device for detecting the position of rotating objects, having an optical signal transmitter and an optical sensor, comprising a stationary light source included in the optical signal transmitter for generating along an optical axis a light beam directed onto a rotating object, the optical sensor being stationary and being arranged on said optical axis on a side of said rotating object located opposite the optical signal transmitter, in the region of the optical axis of the signal transmitter and the sensor, the rotating object being formed with a diametrically extending bore having an entrance window for the light beam and an opposite exit window for the light beam, a slit diaphragm arranged in vicinity of the exit window, and an objective for focusing the light beam onto the slit diaphragm arranged in vicinity of the entrance window, the slit of the slit diaphragm being aligned with a transverse extent thereof at least approximately perpendicularly to an axis of rotation of the rotating object.
In accordance with another feature of the invention, the light source is a laser diode.
In accordance with a further feature of the invention, the sensor is a photodiode.
In accordance with an added feature of the invention, the signal transmitter has a collimator arranged on the optical axis.
In accordance with an additional feature of the invention, the collimator is formed as a member selected from a group consisting of an achromat, a plano-convex lens and an aspherical lens, respectively.
In accordance with yet another feature of the invention, the collimator is arranged so that it is displaceable in the direction of the optical axis.
In accordance with yet a further feature of the invention, the objective and the slit diaphragm are arranged so that they are displaceable inside the bore.
In accordance with a concomitant feature of the invention, one of the objective and the slit diagram, respectively, is arranged so that it is displaceable inside the bore.
Other features which are considered as characteristic for the invention are set forth in the appended claims.
Although the invention is illustrated and described herein as embodied in a device for detecting the position of rotating objects, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings, wherein:
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Lindemann Eckhard
Zelenka Thomas
Greenberg Laurence A.
Heidelberger Druckmaschinen
Lee John R.
Lerner Herbert L.
Pyo Kevin
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