Composition of image information output system

The image information output system of the electronic color separation machine is generally composed of a recording light source, a recording cylinder, a recording optics, and a recording control system. Its task is to perform various conversions in recording the output signal of the image processing system to the photosensitive material. .

First, record light

The recording light source refers to a light source that enables a recording film to sense different light intensities representing image information. The recording light source differs from the scanning light source in that it only requires that the light emitted from the light source match the photosensitive spectrum range of the recording light-sensitive material and the intensity is higher than Records the perceived light energy value of the film.

The recording light source has two kinds of bromine tungsten lamp, xenon lamp and laser which have the light intensity that varies with the image signal and the light intensity is constant using the modulator to change the light intensity. Among them, the characteristics of the glow modulator tube, bromine tungsten lamp, and xenon lamp have been described in detail earlier. The focus here is on the laser light source that is currently used by most electronic color separation machines.

Laser is a new light source in the 1960s which is completely different from the light emission mechanism of ordinary light sources. It is also known as stimulated radiation amplification light, also known as stimulated emission light. The composition of the laser is shown in Figure 4.1. It consists of 1) a laser generator (ie, a laser tube filled with a laser gain medium); 2) a laser energy system comprising two parts of a laser power source and an excitation circuit; and 3) an output beam quality control. The laser power supply is the key to the generation of a stable laser. The structure of the laser power supply is similar to that of an ordinary power supply and has two operating states. One is the steady state of the current, that is, the current sampling signal on the sampling resistor, through the feedback amplifier in the power supply to achieve a stable output current, also known as current control mode. The second is the stable light state. That is, the photocell at the rear of the laser tube is used as the sampling signal of the laser value and is sent back to the power feedback amplifier to ensure the stability of the output light value, which is also called the light control mode. The laser light source has the following characteristics: 1) good directionality and small laser divergence angle; 2) high brightness and energy concentration; 3) good monochromaticity, with a line width of about 10 nm; 4) good coherence and a coherence length of ten meters To hundreds of meters. The current electronic color separation machine uses argon ion laser as the recording light source, and also uses He-Ne laser as the recording light source. The relevant output characteristics of the laser light source are shown in Table 4.1.

Second, the record drum

The recording cylinder is a high-precision cylinder made of metal, the surface of which is covered with a suction hole or a suction groove for absorbing the photosensitive film, and its length and diameter are changed according to the size of the recording radial dimension.

Third, record control system

The recording control system of the electronic color separation machine varies in structure depending on the type of the recording light source and the color separation sheet. In general, there are two types. The first is a recording control system for recording continuous dichroic films, the structure of which is shown in Figure 4.2. It is composed of three parts: exposure light source, exposure optical system and exposure light hole. When the image processing system inputs electrical signals or digital signals representing image information into the recording control system, these image information are first converted into electrical signals for controlling the light emission intensity of the exposure light source so that the image signals are converted into different intensities. The optical signal, which has been recorded on the photosensitive film on the surface of the recording cylinder after being divided by the exposure optical system to focus and expose the aperture, or formed on the photosensitive film after being decomposed by the screen of the screen, forms the desired four-color separation sheet. The second is the record head recording the halftone dichroic sheet, and its structure is shown in Fig. 4.3. It consists of a light source, a beam splitter system, a modulation system, an exposure optical system, and an exposure aperture. It will represent the electrical or digital signal of the image information as the control signal formed by the dot, control the dot generator, record the image information in different dot size on the photosensitive material, and can directly make half for plate making. Color halftone dot separation.