China Education Equipment Purchasing Network News: The laser has a narrow spectrum, high light intensity, and good directionality, which can achieve a perfect combination of beautiful color performance and large screen display. However, there is an important issue that concerns the safety of the human eye with the laser light source.
Laser is a kind of extremely powerful light, and its convergence is very good, it can gather a lot of energy at a very small point. In daily life, lasers have been widely used in industrial, medical, scientific research, military and other fields. Especially when lasers are mentioned, people will naturally think of high-power lasers such as laser weapons and laser cutting machines. We know that lasers are harmful to the human eye. The damage is mainly caused by its high energy, so people's concern about the damage to human eyes caused by laser display products is not unreasonable.
What about display products such as laser projectors and laser TVs that are not safe for human eyes? To unravel people's worries and doubts, let's talk about the principles of different implementations of laser display. Generally, there are two main categories of laser projection schemes, one is a scanning display method, and the other is a projection display method.
The scanning method to realize the laser display image is the earliest attempt to achieve laser imaging. People use the good directionality of laser to scan progressively, and the laser beam scans from top to bottom and from left to right. Horizontal deflection is achieved by a multi-faceted rotating mirror in the projection head, and vertical deflection is achieved by a tilted mirror.
The laser beam used in this solution has strong energy and does harm to the human eye. Today's scanning laser projection solutions are used in large screen and high brightness projection solutions in addition to small projections such as mobile phone embedded projection. This method is basically abandoned, and global manufacturers or R & D institutions have focused their laser display technology solutions on a safe and reliable projection-type display method.
Projection method for laser display solutions: red, green, and blue laser beams are incident on the corresponding light valve after beam expansion, shimming, and decoherence, and the light valve is added with an image modulation signal. The three-color laser is combined by the X prism to enter the projection objective, and finally projected onto the screen through the projection objective to obtain the laser display image.
The reason why this projection display scheme is safe for human eyes is because its red, green and blue lasers have a beam expansion process before imaging. The principle of so-called beam expansion is to spread a thin parallel beam with a lens, and then use a convex lens to spread, and then use a convex lens to claim a thicker parallel beam. At this time, the laser has changed from a point light source to a surface light source.
The red, green, and blue visible laser beams pass through specialized beam-shaping and shaping equipment to expand the laser divergence angle so that it has an energy density similar to that of a xenon lamp, instead of a laser with an energy density tens of thousands of times higher than that of a xenon lamp. The low-energy secret monochromatic light at this time is also not dangerous when it comes out of the laser, that is, the light projected from the lens of the laser projector is the same as the light projected from the lens of any ordinary bulb light source projector. Safety performance index.
Take the TV as an example, the screen is broken, and the laser is accidentally emitted from the screen, so you do n’t have to worry. The laser is still part of the soft light refracted by the lens after being expanded, and it does not harm the human eye.
The laser front projector already has a good commercial operation case, and its safety has been well verified. In July 2008, Beijing Zhongshi Zhongke Optoelectronics Technology Co., Ltd. established the world's first laser theater together with a well-known theater in the United Nations. Before the operation of the theater, CTV Zhongke invited an independent authority, the Institute of Radiation and Radiation Medicine of the Academy of Military Medical Sciences, to test the possible risks posed by the laser projector to human eyes. The report shows that "a protective response can be taken within the normal reaction time of the human eye without accidental damage due to excessive exposure time, so it belongs to the safe range of human eye exposure for a short time.
The maximum power density of the reflected light of the screen is 1.2W / m2, which is far below the maximum allowable irradiation flux in 104 seconds, which is the safe irradiation dose during this time. The report fully verified that the laser display scheme based on the projection method is very safe for the human eye and is very suitable for the human eye. The operation of the laser theater has not received any feedback from consumers.
Removal of safety concerns about laser display technology and products will make more people believe that there is nothing to stop the laser light source from becoming an inevitable trend in the future development of display technology.
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