a large amount of energy of green laser pointer will be concentrated in a very short time
At this point, the increase in irradiance between the cornea and retina of 2 × 10 5 × 10 times. If an increase of 5 × 10 to 50W / m beam, then the angle 2 7 2 membrane to the retina will become 2.5 × 10 W / m. That the pupil is 7mm limiting aperture in the worst conditions, this value is the pupil diameter of young people in the worst case measurements. If a bunch of intense laser is focused onto the retina, only a small portion (5%) of light absorbed by the rods and cones in the visual pigment. The vast majority of light will be absorbed by the melanin in the pigment epithelium (in the macular region, the wavelength of 400nm ~ 500nm within the part of the energy will be macular pigment absorption). The absorption of energy causes localized heating, and burns the pigment epithelium and the adjacent light-sensitive rod cells and cone cells. This burns or damage may lead to vision loss. Then, this kind of laser of green laser pointer is very powerful.
This loss of vision whether permanent, depending on the irradiation intensity. Decline in vision can not normally be found only when macular central part or foveal damage, the exposure of people would feel the vision loss. The fovea is a small depression of macular central retina most 6 SN / T × × × × - × × × × important part is the most sensitive vision District. It is part of the feel light on the retina (see the light of the object). Fovea, the perspective is about equivalent to the angle Zhang moon. If this area is injured, visual field defect may appear early in the visual central region of a fuzzy white spot, within two weeks or longer, the white spots into spots. So that the laser of 100mW green laser pointer can be used in some specific locations.
Finally, patients may in the normal vision will not be perceptible to the blind spot. However, when looking at the pattern as a blank field of view, blind spots can be immediately revealed. The periphery of the retina only in the event of a serious injury, the patient will have a subjective feeling. Small peripheral damage is not noticeable, and may even be in the system of the eye examination has not yet been found. In the 400nm to 1400nm wavelength range, the biggest hazard is the retinal damage. Radiation within the wavelength range can pass through the cornea, aqueous humor, lens and vitreous. Good parallel to the beam, because the assumptions of the retina such as a diameter of about 10 μm diffraction limit spot, so the harm is actually nothing to do with the distance between the radiation source and the eye. The laser beam light of 200mW green Laser Pointer is good in the balance ability.
In this case, it is assumed to reach thermal equilibrium, harmful to the retina to determine the angle αmin in the smallest object. Extended source 50mW blue violet laser pointer , because the retinal irradiance is only dependent on the characteristics of radiation in the light of brightness and eye lens, so the harm actually has nothing to do with the distance between the radiation source and the eye. Point-divergence beam light source, the harm that increases with the reduction in the distance between the waist and eye. The reason is that as the distance decreases, the collected power increases, the size of the retinal image can be assumed to maintain the order of magnitude in the diffraction limit (due to the ability to regulate the eye). The greatest harm in the shortest possible distance of adjustment. As the distance further reduce its harm reduction. The laser of green laser pointer high in the brightness.
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