DE2646701C3 - Photoelectric arrangement - Google Patents

Description

The invention relates to a photoelectric arrangement for measuring the speed of flying bodies, in which one of a? Lasersf ^r ahl derived beam path defines a fixed distance and the detected bepötigte for flying through the path time in an evaluation electronics and, together with the path to determine the respective body speed is used.

In known arrangements with a laser and a downstream cylinder lens for expanding the parallel laser beam, the intensity of the laser light beam decreases with increasing divergence angle away. The reason for this lies in the different brightness distribution over the cross-section of the parallel Laser beam (Gaussian intensity distribution). This decrease in intensity is for laser light barriers ballistic measurements disturbing.

The object of the invention is to eliminate the aforementioned disadvantages and with simple means a To create photoelectric arrangement for ballistic measurements of high measurement accuracy.

The invention solves the problem in that the laser beam is closed in one plane by means of cylindrical lenses a thin, largely parallel band of laser light is widened and that between the laser and the An optical element is inserted into the first cylinder lens, which largely divides the laser beam into several partial beams equal intensity, the aforementioned laser light band being deflected by means of optical elements is that two parallel laser light bands arise with a precisely defined distance and that further that second band of laser light is fed to a photoelectric converter by means of a lens, which the Evaluation electronics controls

The arrangement according to the invention is characterized by high measurement accuracy, since the intensity distribution is largely constant over the entire divergence angle of the laser light bundle If only one photodetector, one amplifier and one trigger are used, measurement errors are also eliminated those in known arrangements with separate components for generating two laser light bands can occur due to phase delays in the electronics. Another advantage is the low structural size Effort, since only one laser and one set of the aforementioned electronic components are required

it is

An exemplary embodiment of the invention is shown in the drawing
It shows
1 shows an arrangement for measuring the speed of flying bodies,

F i g. 2 inside section along the line H-II of FIG. 1.
The F i g. 1 and 2 show a photoelectronic arrangement for measuring the speed of flying bodies, preferably projectiles. Of the

Laser beam LS is expanded into a thin laser light band LS ₁ by means of two cylindrical lenses Z \ and Zi and deflected by means of two mirrors U \ and Lh in such a way that two parallel light bands _{LSxZLS 1 are created} with a precisely defined mutual distance s . The laser light band LS ₂ is fed by means of a cylinder axis Z _{3 to} a photoelectronic converter (e.g. a photodiode) P , the analog output signal of which is amplified in an amplifier V and converted into square-wave pulses J ₁ I] ₂ in a trigger R

will. The output of the trigger R is connected to an electronic counter which is started when a pulse Jx occurs and is stopped when a pulse J _{2 occurs.}

Determining the speed of projectiles

G takes place in such a way that the flight time t is measured for a predetermined distance s of the flight path and the quotient V ₀ = s / r is formed. To determine the time t is in Fi {;. 1 the time counter Z is provided, which is started or stopped by the electrical pulses JxI] _2.

A start pulse J \ is generated when the projectile G flies through the laser light band LS ₁ , a stop pulse J ₂ when the projectile G flies through the laser light band LS ₂ .
Between the laser L and the cylindrical lens Z \ ist

an optical element T is also provided, which divides the parallel laser beam into several beams of equal intensity. This results in a uniform distribution of brightness. Interference fringe systems that arise when the partial beams are superimposed do not have a disruptive effect with this arrangement.

The optical element T can be a rectangular phase guide or a birefringent prism (for example a Wolluston prism). Furthermore, the optical element P can consist of geometrically dividing splitter prisms

«Ο or partial plates or from a known diffraction grating in connection with a birefringent prism etc. exist.

1 sheet of drawings

Claims (1)

Claim: Photoelectric arrangement for measuring the speed of flying bodies, in which a beam path derived from a laser beam defines a fixed route and the time required to fly the route is determined in evaluation electronics and used together with the route to determine the respective body speed characterized in that the laser beam is widened by means of cylinder lenses (Z \ u. Z ₂ ) in one plane to form a thin, largely parallel laser light band (LS ₁ ) and that between the laser (L) and the first cylinder lens (Z \) an optical element (T) is inserted, which divides the laser beam into several partial beams of largely equal intensity, whereby the aforementioned laser light band (LSy) is deflected by means of optical elements (U \ u. U ₂ ) so that two parallel laser light bands (LSxILS ₂ ) with precisely defined Distance (s) arise and that also the second laser light band (LS ₂ ) by means of a lens e (Zz) is fed to a photo- electronic converter (P) which controls the evaluation electronics (V / R / Z)