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1、AvagoTechnologies Semiconductor Products Group Navigation Products DivisionLaser Navigation Safety and Performance in an Optical Mouse SensorWhite PaperIntroductionAvago Technologies, inventor of the popular LED-based optical mouse navigation engine, again revolutionized the PC mouse industry with t
2、he introduction of LaserStream laser navigation technology. Avago Technologies new LaserStream navigation engines provide much finer precision and more accurate tracking on a wider variety of surfaces, such as glossy and reflective surfaces.The key component in the LaserStream system is the VCSEL (V
3、ertical Cavity Surface Emitting Laser), a laser technology previously developed for high-end networking equipment. With the laser, because of its unique light wave characteristics, products using this as an illumination source require compliance to stringent Optical Radiation Regulations worldwide.
4、Manufacturers must ensure that their laser mice meet eye safety regulations, safeguarding the users safety.This document explains the importance of eye safety, the regulations surrounding eye safety and labeling of products, the impact of eye safety and performance, and our recommendations to ensure
5、 a safe laser mouse product.*Note: The manufacturer of the final system, not the manufacturer of the individual pieces, holds the responsibility of eye safety compliance. Since Avago Technologies, Inc., manufactures the components and not the final product sold to consumers, Avago Technologies is no
6、t responsible for safety compliance.How the Human Eye WorksThe human eye consists of a lens, retina, and optic nerve. To see an object, the lens in our eyes focuses an object into small, sharp images on the retina. The retina contains photoreceptors that convert the light into chemical signals. The
7、optic nerve picks up these signals and sends them to the brain.If the eye is looking at a light source such as the sun or a light bulb, the focusing effects of the lens will concentrate the light onto a small area of the retina. By the time the light reaches the retina, the intensity in that area co
8、uld be increased by up to 100,000 times. Local intensity can thus be very high.TemperatureTpeakImage on RetinaRetinaDamage ThresholdFigure 1. The human eye sees by focusing light into small, sharp images on the retina. The light is absorbed into the retina, where most of it is converted into heat. I
9、f the retinal temperature is raised too high, eye damage can result.2The Risk of Eye DamageAn object that emits light at a high power level could damage the retina of the eye. Eye damage can occur for two reasons: thermal damage (heat) and photochemical damage (chemical change). In both cases, the d
10、amage is irreversible and causes permanent loss of sight.Thermal DamageThe light we see is absorbed into the retina where most of it is converted into heat. If the retinal temperature is raised too high, it can cause disruption of the organic tissue; and a burn or lesion is produced. This is called
11、thermal damage hazard.Photochemical damageLight of high enough energy can also break chemical bonds in the eye and form new molecules. Usually the molecules formed are not the same as the ones existed before the bonds were broken. Thus, photoreceptor molecules are destroyed. This is called photochem
12、ical damage.Optical mice emit light through a lens in the bottom of the mouse. This light may be visible light or invisible (infrared) light. If the mice are designed incorrectly, the light emitted could have enough power to cause eye damage.How Much Light Is Too Much?The International Electrotechni
13、cal Commission (IEC) is an international standards organization that oversees the standards procedures for eye safety regulations. The IEC document that covers eye safety is IEC 60825- 1, Edition 1.2. The IEC standard is adopted by practically all nations who publish a laser safety standard, includi
14、ng Australia, Japan, US, Canada, and all countries in the EU. (In Europe, the European standardization organization has published an identical document that is referred to as EN 60825-1.) Every product sold in these countries must be tested and comply with the eye safety regulations.The IEC document
15、 defines safe limits for light output power. The light limits vary depending on type of light (LED or laser) and wavelength of light.Based on the light output power, the product is defined into classes. There are 5 major product classes in the IEC standard with 2 sub classes:Class 1No risk to eyes i
16、ncluding use of optical instrument. No risk to skin. Products are safe under reasonably foreseeable conditions of operation, including the use of optical instruments for intrabeam viewing. Class 1 denotes lasers that do not pose a hazard under normal or single fault conditions. No label is required.Class 1MA subclass of Class 1. Denotes devices that are safe to view if magnifying viewing aids are not used. No label is required.Class 2No risk to eyes for only short time expo
