Considerations when selecting a light source

1.The emission spectrum of the light source should match the absorption characteristics and color sensitivity of the photosensitive material.The energy of light varies with the frequency of the wavelength. The shorter the wavelength, the higher the frequency, and the greater the energy of the photon.When light is absorbed by matter in the process of radiation, it will cause physical and chemical changes in matter due to the certain energy of photon. The chemical reaction caused by light energy is called photochemical reaction.The so-called photochemical matching means that the spectral output distribution of the selected light source should be matched with the spectral color sensitivity of the photosensitive material.That is, the wavelength range of photochemical reaction of photosensitive material absorbing light is just the output range of luminous spectrum of light source, and the maximum absorption peak of photosensitive material is just at the output peak of light source.In this way, the light of the light source can be absorbed by the photosensitive material to the maximum extent and a photochemical reaction occurs.

2.High luminous efficiency and high intensity.On the condition that other conditions remain unchanged, the greater the power and luminous efficiency of the light source, the greater the luminous intensity or brightness, the greater the illuminance of the exposure surface, and the shorter the time required for the photosensitive material to obtain the same exposure.

3.The light source has little thermal radiation.Under the premise that the light source has sufficient luminous intensity or bright light, the thermal radiation of the light source should be as small as possible.When using high-power light source, it is necessary to take forced cooling (air cooling, water cooling) and other measures to expose the photosensitive material and control the temperature below 32℃.

4.The luminous intensity is uniform.The luminous intensity of the irradiation surface of the light source should be as uniform as possible.The exposure device shall be designed to ensure that the illumination difference of each point on the exposure surface of the photosensitive material does not exceed 15%.Light source environment adaptability is strong.Light source should have a strong ability to adapt to the environment, in a variety of different temperature, airflow, voltage changes, can work normally.Of course, in actual production, it is not realistic to choose a light source that can completely meet the above requirements.The purpose of the above selection principle is just to hope that the plate-making operator should consider the influence of the light source on the exposure quality of the photosensitive material when choosing the plate-making light source.