外文文献原稿和译文(信工080201071吴文锋)

外文文献原稿和译文

原稿

Abstract

An objective definition of the protective area of laser eye protectors is discussed.First an appropriate test , method is descried,which is based on the current eye protection standard EN 168. For a variety of already CE type approved laser eye protectors,i.c.for different goggle and spectacle types, results of corresponding measurements are shown. From these results the requirements on the vertical and horizontal angle ranges are derived,which have to be covered by laser eye protectors.This proposal will be implemented in the currently processed amendments of the laser safety standards EN 207 and EN 208. 2001 Elscvier Science Ltd . All rights reserved.

Keywords: Protective area; Laser eye protectors ;EN 207; Eye protection standards; CE type approval

Introduction

The European laser eye protection standards EN 207[1] and EN 208[2] require that "The frame shall be designed so that no laser radiation can penetrate from the side unintentionally."This requirement also implies that the frame should resist at last 10 s to the level of irradiance against which it is designed to protect. This specification for the area to be covered is open to different interpreted in a strict way, only goggle type eye protectors could be permitted. On the other hand, goggles have a very limited peripheral field of view and tend to fog. Except for wearers of corrective spectacles type eye protectors,therefore, usually are the better choice. People would more easily be prepared to wear them because they are more comfortable.

In order to ensure uniform judgeement by the different test laboratories whether the standards mentioned are complied with, it is important to have an objective test method

giving reliable results and to specify a minimum requirement for the coverage of the eye region by the lase eye protectors. The purpose of this paper is to describe such a test method and to propose a minimum requirement.

Test method

A test method determining the coverage of eye protectors is described in prEN 168[3]. This method is similar to that described in EN 207 for the determination of the field of vision. The eye protector is mounted on the test head is form specified in EN 168:1995[4]. This artificial head is used for evaluating all eye protectors in the framework of the basic standard. Such an artificial head represent a mean of the population . In practice, the fitting of an eye protector would depend on the form of the individual head.

A narrow pointing laser beam is directed along the optical axis CC to the centre of one eye of the test head. The test head can be rotated about the two axes AA and BB. These two axes of rotation and the optical axis CC intersect in the middle of the front surface of one eye. The three axes are perpendicular to one another.

The point of intersection has a distance 32 mm from the centre of nose which corresponds to half the mean interpupillary distance specified in EN 166[5]. The limits of the protective area are determined by the points at which the laser beam passes by the eye protector. For each angle of rotation about the axis BB, an upper and a lower limiting angle of protection can be found by rotation about the axis AA.

In the following figures, horizontal angles count as positive if the laser beam is directed to the temporal side of the eye protector and they count as negative if the beam is directed to the nasal side of the eye protector. Likewise, vertical angles count as positive if the laser beam is directed to the upper side of the eye protector and negative when it is directed to the lower side of the eye protector.

The limit of the protective area is reached not only when any of the observations of the laser beam make direct contact with the centre of the eye without being intercepted by the eye protector but also when the beam hits a point on the eye protector at which the material is not sufficiently resistant to laser radiation ,i.e. it does protect for at least 10 s as determined in accordance with EN 207 or EN 208.