Composition of photocopier optical system

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Composition of optical system of copier

copier is a common office equipment. It integrates optical technology, electrostatic imaging technology, electronic technology and mechanical technology. Its structure and principle are relatively complex. The optical system is an important part of the electrostatic copier. Its function is to expose the original through various optical elements, so as to form a light image, and transmit the light image to the charged photosensitive drum surface with uniform charge, so as to form an electrostatic latent image corresponding to the intensity of the original image. The optical systems of various types of copiers are quite different, but their working principles and the functions of various functional components are basically the same

I. Basic requirements for optical system

since the structure of the optical system has a great impact on the overall structure of the copier, and the quality of the copy is also closely related to the optical system, the optical system of the electrostatic copier must meet the following basic requirements:

1. the spectral characteristics of the light source and lens should match the photosensitive drum used

2. the light source shall have sufficient intensity to quickly de energize the sensitized drum

3. the (2101) light source with low wallpaper power and high luminous efficiency shall be selected to reduce power consumption

4. the optical path system has good adjustment performance and high luminous efficiency (i.e. low light loss)

5. the synchronization error between the optical path system and the photoconductor shall not be greater than 0.5%, and the optical distance shall always remain unchanged during the whole process from the starting point to the end point of scanning

6. ensure uniform illumination of the entire original

7. it shall have good heat dissipation to ensure the continuous copying of the copier, and the temperature of the platen glass shall not exceed 70 ℃

8. the repetition accuracy of the system shall be high, the structure shall be durable, safe and reliable

9. it shall have good sealing to prevent the external environment from polluting the optical system

10. the system shall be easy to load, unload, adjust, clean and replace vulnerable parts

11. the installation of light source shall be horizontal to the ground, especially the halogen lamp, otherwise its service life will be affected

12. irradiating the photoconductor through the optical path system should make the light energy received by each point on the surface of the photoconductive layer basically consistent

II. Optical scanning system

the optical system for scanning and exposing the original is called the scanning system, which includes the platen glass, exposure lamp, reflector, scanning frame, scanning frame position detection sensor and lens unit

(I) type of optical scanning system

at present, the scanning methods adopted by the electrostatic copier mainly include three types: original stage mobile slit exposure, draft stage mobile optical fiber exposure and reflector mobile slit exposure. The so-called slit exposure is to irradiate the original through a light band during exposure, and move synchronously with the photosensitive drum for scanning exposure to form an electrostatic latent image on the photosensitive drum

1. movable slit exposure of the original table

the movable scanning exposure system of the original table uses the reciprocating motion of the original table glass to complete the image scanning. The exposure lamp, lens and reflector are fixed, and the surface linear speed of the original stage and the photosensitive drum keeps moving synchronously or in a certain proportion. Therefore, this scanning exposure method has the advantages of simple optical system structure, small volume, clear and accurate imaging. However, this machine has poor load capacity on the platen, and the copying speed is generally low. It can not copy heavy originals, and the working space is large and the zoom grade is small

2. movable optical fiber exposure of the platen

the optical fiber optical system is composed of two rows of optical fibers which are staggered and stacked together. The optical fiber matrix is used to replace the lens and reflector in the optical system, and directly transmit the reflected light of the original image to the surface of the photosensitive drum to form an electrostatic latent image. This type of copier is characterized by the movement of the platen during operation; The optical fiber is immobile, simple in structure and small in size, but cannot be doubled and the resolution is low. Generally, the diameter of optical fiber used is about 1.1mm, and the length of fiber is 29.4mm. Such as the canonnp-200 copier of the old model

3. platen fixed exposure

platen fixed optical system copier is the exposure method adopted by most electrostatic copiers at present. The process of this exposure method is: the original platen and imaging lens are fixed during copying, and the movement of the first scanning reflector. What is your understanding of the tape tension machine? Let's introduce the maintenance method and functional characteristics of the belt pulling machine. The dynamic speed is always equal to or proportional to the linear speed on the surface of the photosensitive drum. The second scanning mirror moves in the same direction with the first scanning mirror at half the moving speed of the first scanning mirror, and the first mirror to the fourth or fifth mirror must always be in the focus of the imaging lens, whether on the left or right of the imaging lens, That is, keep the conjugate distance constant

the platen fixed copier is characterized by large platen load capacity, can copy thick books, small working space, fast copying speed, etc. However, it has high requirements for the movement accuracy of the optical scanning device, requiring that the scanning system be as light as possible, and that it must be stable during movement, with small vibration. Ricoh ft-4085 copier is a fixed platen type. (end)


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