Optical aid

Figure H.5 Optical aid for seeing higher universes. (Invention hy William Beaty.)...

Received April 26, 1951. For material supplementary to this article order Document 3244 from American Documentation Institute, 1719 N St., N.W., Washington 6, D. C., remitting 1.00 for microfilm (images 1 inch high on standard 35-mm. motion picture film) or 6.75 for photocopies (6X8 inches), readable without optical aid. 

Audio-Visual Aids In this category those teaching aids are included which involve the use of two of our senses i.e. hearing and seeing. These are classified as (i) optical aids and (ii) Television. 

Optical Aids Some such aids are discussed here. 

It is usual to begin with an exact visual examination, if possible in comparison with an undamaged sample. Notice should be made of any peculiarities in appearance. Sometimes abraded and raised areas, holes, thin places and pressure marks can be easily recognized without optical aids. With the use of a magnifying glass they can be seen more clearly and in more detail. The same is true for many... 

A visual examination should be made to yield information on the general condition of the part, component or surface to be examined, including such conditions as the presence of scratches, wear, cracks, corrosion or erosion on the surface, or evidence of leaking. Optical aids such as television cameras, binoculars and mirrors may be used. Surface rephcation as a method of visual examination may be considered acceptable, provided that the resolution at the surface is at least equivalent to that obtainable by visual observation. Any visual examination that requires a clean surface or decontamination for the proper interpretation of results should be preceded by appropriate cleaning processes. 

In general, the visible spectrum comes to mind, where a human is observing his environment either with the naked eye or via optical and electro-optical aids like binoculars, night vision goggles (NVG) or forward-looking infrared (FLIR)... 

BOR-60 (Russian Federation) visual with optical aids... 

CEFR (China) conputer control and visual with optical aids if necessary... 

Fermi (USA) internal-visual with optical aids (limited extent) ... 

Class 2M lasers emit visible radiation in the 400—700 nm range but with power output below 1 mW. These lasers pose little ocular hazard to the unaided eye but become potentially hazardous when viewed with optical aids. 

NOHD is the distance along the axis of the laser beam beyond which the irradiance (W/cm ) or radiant exposure (J/cm ) is not expected to exceed the appropriate personnel exposure level, that is, the safe distance from the laser. The NOHD-O is the NOHD when viewing with optical aids. 

Thermography Optical aids (closed circuit TV, light tubes, etc.) Visual, with aid of gages... 

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