Brief introduction of the structure and working pr

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A brief introduction to the structure and working principle of the projector

in our work, the projector has been used all the time, but many people may not know the structure and working principle of the projector very well. In fact, the projector, like the slide projector, also uses the convex lens imaging principle to project transparent objects onto the screen. The rubber tension machine can also cooperate with the type of the test object or requirements to destroy the test piece and obtain the whole test process, The projector is mainly composed of optical system, ventilation equipment and circuit

optical system of projector

the optical system of projector mainly includes light source, auxiliary condenser, threaded lens, projection lens, reflector and reflective bowl. The requirements and functions of light source, projection lens and reflective bowl are similar to those of slide projector

(1) the condensing system of the projector

the condensing lens of the projector is mostly a screw lens, also known as a Fresnel lens. It is composed of two thin flat plexiglass plates with concentric circular threads, which acts as a large-diameter convex lens. The screw lens has the advantages of large diameter, light weight and good light transmittance, while the main disadvantage is that the deformation will be caused when the temperature rises above 70 ℃

in order to reduce the surface temperature of the screw lens, a crescent lens, also known as the auxiliary condenser, is placed between the light source and the condenser. It can not only block the radiation of the heat energy of the light source to the screw lens, but also expand the containment angle of the screw lens. There is a load glass on the screw lens, which can not only show projection films, but also write, and can also use high molecular waterproof material waterstop gb18173.2 ⑵ 000 for some experiments or teaching aids

(2) planar reflector

the projector is equipped with an angle adjustable planar reflector to convert the vertical optical axis from the condenser to the horizontal optical axis. Therefore, the slide has changed from vertical inverted to horizontal upright, and the magnified positive image is obtained on the screen, so that the teacher can explain and demonstrate to the students, which is very convenient. Before starting the projector, the plane reflector must be turned on to ensure that the light emitted by the light source is directed to the screen after starting the projector, so that the light spot appears on the screen; If the plane reflector is not turned on, it will reflect the light emitted by the light source back to the light source after startup, which will increase the temperature in the machine and the surface of the light source, and affect the service life of the projector

other parts and circuits of the projector

there are also some important electrical equipment and ventilation equipment in the projector. The transformer converts 220 V mains power into 24 V AC voltage for projection bulbs. Most projection bulbs are 24 v/300 w bromine tungsten lamps, which generate a lot of heat during operation. If they are allowed to accumulate, the temperature in the machine will inevitably rise, which will damage the threaded lens and electrical equipment. Therefore, the machine is equipped with a squirrel cage fan, so that the pointer in the machine is aligned with the zero point, and the heat is discharged out of the machine in time to reduce the temperature in the machine

rotating the focusing button will drive the projection lens and plane mirror to move up and down along the vertical direction, change the distance between the projection lens and the object (projection), and realize the focusing process. In addition, the elevation angle of the plane mirror is adjustable. Changing the elevation angle can adjust the height of the image on the screen. The mirror can also rotate 360 degrees in the horizontal plane, so that the image can be projected on any wall of the projection room without moving the body

at present, there is also a high brightness projector, whose structure is roughly the same as that of an ordinary projector, except that the light source does not use a bromine tungsten lamp, but uses a dysprosium lamp with a luminous effect of 2 ~ 3 times that of a bromine tungsten lamp. For the use method, please refer to the relevant parts of the reflective slide projector

use of projector

1. general adjustment of projection equipment

① adjusting the light spot is to make the light spot project evenly onto the screen. If it is uneven, adjust the position of the bulb and the reflecting bowl or condenser, and move slowly until it is even

② adjusting the optical path is to make the optical path of each symmetrical point on the screen relative to the optical axis equal. For example, move the position and angle of the slide projector and the position and inclination of the screen to make the screen perpendicular to the incident light axis, and the picture will not produce trapezoidal distortion

③ adjusting the distance is to adjust the distance between the slide projector and the screen to change the size of the image. Generally speaking, the width or height of the image should be 1/5 of the length of the classroom

④ adjust the focal length, that is, adjust the lens and the projected 3 The distance to build the 3rd generation semiconductor Innovation Incubation Platform makes the picture present the best clear state

2. usage of special operating parts of projector

(1) usage of tone adjustment knob

during focusing, if it is found that the center and edge of the picture cannot be adjusted clearly at the same time, or the image lines have color edges (note that it does not refer to the color edges at the edge of the projection spot), adjust the tone adjustment knob to make it normal

(2) usage of strong and weak light switch

if the indoor light is too strong, diluting the image on the screen, the projector can use strong light, that is, turn the strong and weak light switch to the strong light position. When working at the strong light level, the bulb voltage is higher than normal, which will shorten the life of the bulb. Therefore, try not to use the strong light when it is available or not. However, the strong and weak light switch shall be set to the weak light position before shutdown

(3) usage of light change switch

if the bulb of the projector is normally damaged during projection, the light change switch can be placed in another position, and the circuit is connected to the spare bulb, so as to achieve the purpose of quick bulb replacement

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