Method of setting an electro-optical signal path and an apparatu

Details Method of setting an electro-optical signal path and an apparatu Method of setting an electro-optical signal path and an apparatu

1995-07-24

1998-05-19

Negash, Kinfe-Michael

Optical: systems and elements

Deflection using a moving element

Using a periodically moving element

359154, H04B 1000

Patent

active

057543240

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The invention relates to a method for setting an electro-optical signal path and to an apparatus for carrying out said method.


BACKGROUND ART

A known method of this type is described in for instance "Lichtschranken" by M. Rascher and H. Klemmt, Dr. Alfred Huthig Verlag GmbH, 1987, and by this method a light source emits short light pulses with a fixed duty cycle and a fixed pulse intensity. A light-sensitive receiver is connected to a mean value generating circuit as well as to a single comparator circuit. A signal appears on the output of the comparator, said signal indicating whether the generated mean value exceeds or is lower than a set reference value applied on the reference input of the comparator. An interruption of the optical transmission between the light source and the light receiver causes a lower mean value which after the comparison with the fixed reference results in a change in the output signal on the comparator. This method is encumbered with several draw-backs. The establishing of several sets including a light source and a light receiver arranged close to one another may result in an error situation in which it is impossible to set a reference value, which in a reliable manner causes a signal change on the output of the comparator when the light source associated with the light receiver is interrupted. The remaining light sources take inadvertently part in setting a mean value which irrespective of the interruption of the light source in question prevents a signal change on the output of the comparator in question. When the reference value is set so close to the mean value applying to no interruption of the light sources that an interruption of the light source associated with the light receiver results exactly in a signal change, the light receiver becomes very sensitive to interruptions often occurring within the industry, such as electrical noise radiation, mechanical shakes of the light source as well as variations in the emitted light intensity of the light source caused by temperature variations and ageing of the components.
U.S. Pat. No. 5,126,555 describes an apparatus where the above error situation has been avoided by means of a synchronized receiver circuit ensuring that nothing but the pulse pattern emitted by the light source is recognized after reflection on an object in the so-called activation circuit of the light receiver. This is obtained by the emitted pulse/interruption pattern, such as in form of an EXCLUSIVE-OR gate. being recognized instead of generation of a simple mean value. As a result, foreign light sources emitting a continuous or pulse-shaped light intensity recognized on the light receiver can be distinguished from the light source of the apparatus, whereby a change encumbered with errors is avoided on the output. The light source remains interrupted until the error situation has ceased.
This apparatus is encumbered with the draw-back that it can be inactivated when exposed to a foreign light source. Another draw-back is found in the fact that the fixed light pulse intensity used in the apparatus does not immediately prevent an overload of the light-sensitive receiver or the succeeding mean value generating circuit, said overload appearing in connection with strongly reflecting objects. Finally, an essential draw-back of this apparatus is that it does not comprise means for adapting the pulse intensity of the light source to a use involving varying transmission conditions between the light source and the light receiver.
This draw-back has been overcome in an apparatus described in EP-PS No. 0.418.989, describing a photo-cell with a light source. The output power of this light source is automatically adapted to optionally appearing impurities on the light source or on the light receiver. The appearance of impurities may result in a gradual attenuation of the transmission therebetween. The advantage is obtained by means of a detection circuit connected to the light receiver. The detection circuit activates a coupling process ensuring tha

REFERENCES:
patent: 4206510 (1980-06-01), Strait
patent: 5126555 (1992-06-01), Hawryluk

Affiliated with

Also associated with

Rating

Method of setting an electro-optical signal path and an apparatu does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Method of setting an electro-optical signal path and an apparatu, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of setting an electro-optical signal path and an apparatu will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-1858213