Retroreflectors, especially for beam scanning applications and b

Details Retroreflectors, especially for beam scanning applications and b Retroreflectors, especially for beam scanning applications and b

1982-04-02

1984-08-07

Arnold, Bruce Y.

350103, 350590, G02B 5124, G02B 5128, G02B 1700

Patent

active

044640145

DESCRIPTION:

BRIEF SUMMARY
The present invention relates to retroreflectors especially for beam scanning applications, and to beam scanning apparatus incorporating such retroreflectors. Various types of retroreflectors are known, in particular, so-called triple mirrors and retroreflecting foils such as the foil sold under the "Scotchlite" trademark.
In comparison with mirrors retroreflectors have the property that they reflect a light beam back on itself not only at normal incidence but also when the light beam is incident within a predetermined angular range around the main angle of normal incidence. As a result of this property retroreflectors are well suited to a variety of different applications. By way of example, retroreflectors are particularly useful for road signs in order to make the latter readily visible at night and for retroreflective safety devices for motor vehicles and road users. Retroreflectors are also used with light barriers and with beam scanning apparatus such as the beam scanning apparatus used for generating light grids and light curtains.
For these applications it is particularly advantageous that the retroreflector and the light transmitter/receiver of the beam scanning apparatus do not need to be accurately aligned.
For beam scanning applications interest has, in the past, been centered on the triple mirror type of reflector which is a product of high optical quality and, accordingly, is relatively expensive to manufacture.
For cost and technical reasons there is also a great deal of interest in retroreflecting tapes and foils which consist of small retroreflecting particles, in particular glass spheres or beads which are mounted in closely packed form on a substrate such as a plastic foil. The small retroreflecting particles are in particular glass spheres and have substantially the same characteristics as a triple mirror, i.e. they reflect the incident light back on itself. The angular range in which incident radiation is reflected back on itself depends on the angle of incidence of the incident radiation. The customary retroreflecting materials (such as the retroreflecting tape sold under the trademark "Scotchlite") exhibit the retroreflecting property (i.e. the property of reflecting light back on itself) over a range depending on the type of material from .+-.20.degree. to .+-.50.degree. relative to the direction of normal incidence. There are, however, a series of applications for which this angular response range of the retroreflector is not acceptable. In order to overcome the relatively pronounced directional dependence which is associated with reflection at retroreflectors attempts have already been made to sub-divide a retroreflector consisting of triple mirrors into individual elements (DE-PS No. 22 36 482). In this arrangement the individual retroreflecting elements are inclined to one another at increasing angles to that the scanning light beam of a light curtain impinges as closely as possible to normal incidence on the individual triple elements which are more directionally dependent than the aforementioned retroreflecting foils. The known retroreflector with retroreflecting elements inclined at increasing angles to one another is however only suitable for use with a sector-shaped scanning beam. Each individual retroreflector element must also be set at a predetermined position relative to the scanning beam and this makes it difficult if not impossible to manufacture the retroreflector by cost-effective mass production techniques.
The principal object underlying the present invention is to provide a retroreflector based on the use of tightly packed retroreflecting particles in which the directional dependence of the retroreflector is reduced sufficiently that retroreflecting properties are obtained over a larger angular range of incident light with light incident at each angle within this angular range being preferably reflected back on itself.
It is a further object of the present invention to provide a retroreflector which results in only a minimal loss of intensity of the retroreflecte

REFERENCES:
patent: 3806222 (1974-04-01), Knappe
patent: 3945714 (1976-03-01), Walter
patent: 4123140 (1978-10-01), Ryan et al.
patent: 4263345 (1981-04-01), Bingham et al.

Affiliated with

Also associated with

Rating

Retroreflectors, especially for beam scanning applications and b does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Retroreflectors, especially for beam scanning applications and b, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Retroreflectors, especially for beam scanning applications and b will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-601142