The projector, like the slider, uses cam lens imaging principles to project transparent objects into the screen and to create magnified images, as shown in figures 2-2-8. The projector consists mainly of optical systems, ventilation and circuits。
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Figure 2-2-7 reflector slider structure chart
1. Optical system for projectors
The optical system of the projector, which consists mainly of light sources, auxiliary polyscopes, screw lenses, screening lenses, mirrors and reflecting bowls, has similar requirements and functions to those of the slide machine and is not discussed here。
(1) the projector's spotlight system
Most of the projector's oculars are screw lenses, also known as the finel lenses, which are made up of two thin, flat, organic glass plates with co-centric threads, and function as if they were a large-calibre cones. A screw lens has the advantage of being large in calibre, light in weight and light, and the disadvantage is mainly that temperature rises to above 70 °c to cause deformation。
In order to reduce the surface temperature of the screw lens, a new monthly mirror is placed between the light source and the polyscope, also called the auxiliary polyscope. It's both able to shield thermal radiation from the screw lens from the light source and expand the tolerance angle of the screw lens. There are glass loads on the screw lens that can be shown not only in slides, but can also be written or demonstrated in some experiments or teaching aids。
(2) flat mirror
The projector is equipped with a calibrated plane mirror that transforms the vertical axis from the lens into a horizontal axis. The slides were thus turned from vertical to horizontal and were magnified on the screen to make it easy for teachers to talk to students about side presentations. The projector must open the plane mirror before opening, ensuring that the light from the light is directed to the screen after opening, so that the light spots appear on the screen; if the plane mirror does not open, it returns the light from the light back to the light source, increases the temperature of the inside and the surface of the machine and affects the lifetime of the projector。
2. Other components of projectors and circuits
The projectors also contain important electrical and ventilation equipment, as shown in figures 2-2-8. Among them, the transformer converted 220 v municipal electricity into 24 v exchange voltage for the screening of light bulbs. Most of the lamps are shown as 24 v/300 w tungsten lamps, which work with large amounts of heat and, if they are allowed to accumulate, the internal temperature will inevitably increase and damage screw lenses and electrical equipment. The aircraft is therefore equipped with rat cage-like fans, which remove the in-board heat from the machine in a timely manner and reduce the in-board temperature. Rotation focus buttons will drive the screening lens and the plane reflector up and down the vertical direction, changing the distance between the screening lens and the object (show) and achieving the focus process. In addition, the angles of the plane reflectors can be adjusted to change the angles and adjust the height of the images on the screen. The mirror can also rotate 360 degrees horizontally so that, without moving the body, the image can be projected on any of the walls of the screening room。
The circuits of the projector are shown in figure 2-2-9, where the k1 power switch is connected to ensure that the fan and the light bulb are turned on or off simultaneously. The k2 safety switch is also called a side door switch and is located below the polyoptic panel (the projector door). When the door is lifted, the door is broken, the work switch is disabled, the light bulb and the fan are not working; when the door falls, the switch is open and the work switch resumes。
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Figure 2-2-9 electricity principles for projectors figure
At present, there is also a high-light projector, which has the same structure as the normal projector, except that light sources do not use bromine. Conversion of tungsten lamps to tungsten lamps, which are 2-3 times bromotungsten lamps, can be used to refer to relevant parts of reflector slide machines。
Use of projectors
General adjustments to projecting equipment
One adjusts the light spot, so that it is evenly projected on the screen. If it is not even, the light bulb can be repositioned to reflect bowls or spotlights, and the movement will be slower until it is even。
2 the luminescent adjustment is to equalize the range of symmetrical points on the relative axis on the screen. The image does not produce glacial malformations, for example, by moving the slider's position, angles and the positions and inclinations of the screen screens to vertically align the screen with the input axis。
3 resizes the image by adjusting the distance of the slider to the screen. Generally, the width or height of the image should be one fifth of the length of the classroom。
The focus is adjusted to adjust the lens's distance from the projector to give the picture the best possible clarity。
Use of special operating components for projectors
(1) use of the hue-adjusting thrust
In the course of the focus, if it is found that the central part of the picture and the edges cannot be adjusted for clarity at the same time, or if the coloured edges of the image line (not to mention the edges that appear on the edges of the projection) are found, the tuning button should be adjusted and normalized。
(2) use of strong and weak light switches
If the indoor light is too strong to dilute the image on the screen, the projector can use strong light, i. E. Toss a strong light switch to a strong light position. When working at a strong light level, the light bulb voltage is higher than at normal times, reducing the lifetime of the light bulb, so that the use of strong light is minimized when available. However, when off, the strong and weak light switch is placed in the weak light position。
(3) use of changing light switches
If the projector has normal damage to the light bulb during the screening, the switch can be placed in a different position and the circuit is connected to the backup light bulb for the purpose of quickly replacing the light bulb。
