Over its almost 300-year history of development, the microscope has probably become one of the most popular optical instruments, widely used in all areas of human activity. It is especially difficult to overestimate its role in teaching schoolchildren who learn about the microworld around them with their own eyes.
A distinctive feature of the proposed microscope is the “non-standard” use of a conventional Web camera. The principle of operation is to directly register the projection of the objects under study onto the surface of the CCD matrix when illuminated by a parallel beam of light. The resulting image is displayed on a PC monitor.
Compared to a conventional microscope, the proposed design does not have an optical system consisting of lenses, and the resolution is determined by the pixel size of the CCD matrix and can reach several microns. The appearance of the microscope is shown in Fig. 1 and fig. 2. The model “Wcam 300A” from Mustek, which has a color CCD matrix with a resolution of 640x480 pixels, was used as a Web camera. The electronic board with the CCD matrix (Fig. 3) is removed from the case and, after minor modifications, is installed in the center of the light-tight case with an opening lid.The modification of the board consisted of resoldering the USB connector in order to make it possible to install additional protective glass on the surface of the CCD matrix and seal the surface of the board.
A through hole is made in the housing cover, in the center of which a block of three LEDs different colors of glow (red, green, blue), which is a light source. Block LEDs, in turn, is covered with a light-proof casing. Remote location LEDs from the surface of the matrix allows you to form an approximately parallel beam of light on the measurement object.
The CCD matrix is connected to the PC using a USB cable. The software is standard and included with the Web camera.
The microscope provides image magnification of 50...100 times, with an optical resolution of about 10 microns with an image refresh rate of 15 Hz.
The design of the microscope is shown in Fig. 4 (not to scale).
To protect it from mechanical damage, quartz protective glass 6 with dimensions 1x15x15 mm is installed on the input window of the CCD matrix 7 to protect it from mechanical damage. Protection of the electronic board from liquids and mechanical damage is ensured by sealing its surface with silicone sealant 8. The object under study 5 is placed on the surface of protective glass 6. Lighting LEDs 2 are installed in the center of the hole in the cover 4 and are covered from the outside with a light-proof plastic casing 3. The distance between the object under study and the block LEDs is approximately 50...60 mm.
The lighting LEDs (Fig. 5) are powered by battery 12 of three series-connected galvanic cells with a voltage of 4.5 V.The power is turned on using switch SA1, LED HL1 (1 in Fig. 4) is an indicator light, located on the protective casing and signals the presence of supply voltage. The lighting LEDs EL1–EL3 are turned on and thus the lighting color is selected using switches SA2–SA4 (13) located on the side wall of the housing 11.
Resistors R1, R3—R5 are current-limiting. Resistor R2 (14) is designed to adjust the brightness of LEDs EL1-EL3; it is installed on the rear wall of the case. The device uses constant resistors S2-23, MLT, variable resistors - SPO, SP4-1. Power switch SA1 - MT1, switches SA2 - SA4 - push-button SPA-101, SPA-102, LED AL307BM can be replaced with KIPD24A-K
Since the apparent size of the output images depends on the characteristics of the video card used and the size of the monitor, the microscope requires calibration. It consists of registering a test object (transparent school ruler), the dimensions of which are known (Fig. 6). By measuring the distance between the ruler strokes on the monitor screen and correlating them with the true size, you can determine the image scale (magnification). In this case, 1 mm of the monitor screen corresponds to 20 microns of the measured object.
Using a microscope, you can observe various phenomena and measure objects. In Fig. Figure 7 shows an image of laser perforation of a 500 ruble banknote. The average diameter of the holes is 100 µm, and a variation in the shape of the holes is visible. In Fig. Figure 8 shows an image of a Hitachi color picture tube mask. The diameter of the holes is about 200 microns.
A spider, its leg and mustache were chosen as examples of biological objects; they are shown in Fig. 9 and fig. 10, respectively (the diameter of the whisker is about 40 microns), the author’s hair (diameter is 80 microns) - in Fig.11, fish scales - in Fig. 12. It is interesting to observe the processes of dissolution of substances in water. The processes of dissolving salt and sugar are given as an example. In Fig. 13,a and fig. 14a shows particles of dry salt and sugar crystals, respectively, and in Fig. 13.6 and fig. 14.6 - the process of their dissolution in water. Zones of increased concentration of substances and the effects of light focusing at dissolution centers are clearly visible.
