英语翻译

英语翻译
History
Between 1960 and 1973,Leitz (Leica)[1] patented an array of autofocus and corresponding sensor technologies.At Photokina 1976,Leica had presented a camera based on their previous development,named Correfot,and in 1978 they displayed an SLR camera with fully operational autofocus.The first mass-produced autofocus camera was the Konica C35 AF,a simple point and shoot model released in 1977.The Polaroid SX-70 was the first autofocus single-lens reflex camera,released in 1978.The Pentax ME-F,which used focus sensors in the camera body coupled with a motorized lens,became the first autofocus 35 mm SLR in 1981.In 1983 Nikon released the F3AF,their first autofocus camera,which was based on a similar concept to the ME-F.The Minolta Maxxum 7000,released in 1985,was the first SLR with an integrated autofocus system,meaning both the AF sensors and the drive motor were housed in the camera body,as well as an integrated film advance winder - which was to become the standard configuration for SLR cameras from this manufacturer,as it would for Nikon.Canon,however,elected to develop their EOS system with motorised lenses instead.More recently,Nikon have also adopted this strategy with their AF-S range of lenses; their entry-level DSLRs do not have a focus motor in the body.
Active autofocus
Active AF systems measure distance to the subject independently of the optical system,and subsequently adjust the optical system for correct focus.
There are various ways to measure distance,including ultrasonic sound waves and infrared light.In the first case,sound waves are emitted from the camera,and by measuring the delay in their reflection,distance to the subject is calculated.Polaroid cameras including the Spectra and SX-70 were known for successfully applying this system.In the latter case,infrared light is usually used to triangulate the distance to the subject.Compact cameras including the Nikon 35TiQD and 28TiQD,the Canon AF35M,and the Contax T2 and T3,as well as early video cameras,used this system.
An exception to the two-step approach is the mechanical autofocus provided in some enlargers,which adjust the lens directly.