r\ b(o. ii./o-^ 
 
 ET-104 May 1937 
 
 United States Department of Agriculture 
 Bureau of Entomology and Plant Quarantine 
 
 A SIMPLE MICROPROJECTOR 
 By S. W. Simmons, Division of Insects Affecting Man and Animals 
 
 Field workers at times find themselves in need of a method for reproduc- 
 ing images of small specimens mounted on slides when usual manufactured devices 
 for this purpose are not readily obtainable. In such instances a monocular 
 compound microscope can be made to serve as a microprojector by fitting it with 
 the simple mirror attachment described herein. This attachment can be made at 
 very little expense, and the necessary materials are usually available. 
 
 The apparatus consists essentially of a mirror so mounted near the 
 ocular of the microscope that the image is reflected downward on a piece of 
 paper. 
 
 The materials needed are as follows: 
 
 (1) One mirror of as nearly optically correct glass as possible, 
 
 approximately 1 by 1 inch. (Optically correct glass is needed, 
 otherwise the image will be distorted.) 
 
 (2) Metal frame for mirror. 
 
 (3) One metal bar about 3 inches long, 1/2 inch wide, and 1/16 inch 
 
 thick. 
 
 (4) One strip of spring steel or brass, approximately 3/4 inch 
 
 wide and about 2f inches long. 
 
 (5) Solder. 
 
 Figure 1 shows construction and assemblage of the apparatus. One end 
 of the metal bar is soldered to the back of a piece of thin sheet copper, brass, 
 or tin. This piece of metal should be about 1/4 inch greater on all sides 
 than the mirror. The mirror is then placed on the metal, face upward, on the 
 side opposite from the metal bar, and the edges of the metal are turned over 
 it to form a rigid frame. 
 
 To the opposite end of the bar and about 1\ inches from the mirror a 
 spring clip is soldered as shown in the figure. This clips over the draw tube 
 of the microscope and holds the apparatus firmly in place. It is easily con- 
 structed from thin spring brass or steel. 
 
 The metal bar is bent so that it places the mirror directly in front of 
 the ocular lens, and at a 45° angle to it. 
 
- 2 - 
 
 The apparatus is then clipped on to the draw tube of the raicroscope, and 
 the instrument is tilted back so that the draw tube is parallel with the table. 
 When a piece of white paper is placed beneath the mirror and the object on the 
 slide is brought into focus the image is reflected on the paper. 
 
 The mirror is properly adjusted when the field of light reflected is 
 circular. This can be determined by the use of a compass. Corrections are 
 made by bending the metal bar and turning the apparatus. 
 
 It is essential that the source of light be adequate and that the room 
 be darkened. Most medium-priced raicroscope lamps are probably satisfactory. 
 A small spot light on a universal-jointed mount is convenient, but such lamps 
 are generally not bright enough to use with high-power magnifications. The 
 brighter lamps with large lenses can be used successfully. Scattered light 
 from the lamp must be at a minimum. This can be reduced by placing the large 
 end of a metal funnel over the lens and directing the small end of the funnel on 
 the object. The condenser and mirror of the microscope can be removed or pushed 
 to one side and the light placed close beneath the specimen, care being taken 
 to avoid overheating. Colored glass filters are better removed from the lamp 
 before use, 
 
 The magnification varies with the distance of the mirror from the eye 
 lens, with the length of the draw tube, with the distance of the paper from 
 the mirror, and with the ocular and objectives used. 
 
 When the center of the mirror is 15 mm from the ocular and the paper is 
 5-g- inches below the mirror, as it is v/hen lying on a table beneath the ocular 
 of the average microscope tilted parallel to the table, a magnification of 
 about 52.5 times can be obtained with a 16-mm objective and a lOx ocular. By 
 pulling out the draw tube the magnification is increased. Extending it 26 mm 
 increases the magnification to 64 times. With large lice, mites, etc., a 32-mm 
 objective is convenient and does not require an especially strong light. A 
 very good light must be used with an objective less than 4 mm. 
 
 Specimens reflected in this manner can be traced conveniently. A small 
 mirror as recommended does not interfere with free use of the pencil when 
 drawing. 
 
Figure 1. — Mirror attachment for microprojection, 
 asserabled for use on a compound microscope. 
 Actual size. 
 
UNIVERSITY OF FLORIDA 
 
 3 1262 08721 6718