Opaque Projectors: The opaque projector, epidioscope, epidiascope or episcope is a device which displays opaque materials by shining a bright lamp onto the object from above. A system of mirrors, prisms and/or imaging lenses is used to focus an image of the material onto a viewing screen. Because they must project the reflected light, opaque projectors require brighter bulbs and larger lenses than overhead projectors. Care must be taken that the materials are not damaged by the heat generated by the light source. Opaque projectors are not as common as the modern "overhead". Opaque projectors are typically used to project images of book pages, drawings, mineral specimens, leaves, etc. They have been produced and marketed as artists’ enlargement tools to allow images to be transferred to surfaces such as prepared canvas, or for lectures and discourses.


 Video projectors: A video projector is an image projector that receives a video signal and projects the corresponding image on a projection screen using a lens system. All video projectors use a very bright light to project the image, and most modern ones can correct any curves, blurriness, and other inconsistencies through manual settings. 

 Video projectors are widely used for many applications such as, conference room presentations, classroom training, home theatre and concerts. Projectors are widely used in many schools and other educational settings 

Overhead Projectors: An overhead projector is a variant of slide projector that is used to display images to an audience.

 

Overhead projector commonly used at school.

 Slide Projector:

A slide projector is an opto-mechanical device to view photographic slides. Slide projectors were common in the 1950s to the 1970s as a form of entertainment; family members and friends would gather to view slide shows. In-home photographic slides and slide projectors have largely been replaced by low cost paper prints, digital cameras, DVD media, video display monitors, and video projectors.

A projector has four main elements:

• electric incandescent light bulb or other light source (usually fan-cooled)
• reflector and "condensing" lens to direct the light to the slide
• slide holder

• focusing lens 

Movie Projector: A movie projector is an opto-mechanical device for displaying moving pictures by projecting them on a projection screen. Most of the optical and mechanical elements, except for the illumination and sound devices, are present in movie cameras.

 





Television (TV) is a telecommunication medium for transmitting and receiving moving images that can be monochrome (black-and-white) or colored, with or without accompanying sound. "Television" may also refer specifically to a television set, television programming, or television transmission.
The etymology of the word has a mixed Latin and Greek origin, meaning "far sight": Greek tele (τῆλε), far, and Latin visio, sight (from video, vis- to see, or to view in the first person).

Camcorder:
A camcorder (formally a video camera recorder) is an electronic device that combines a video camera and a video recorder into one unit; typically for out-of-studio consumer video recording. Equipment manufacturers do not seem to have strict guidelines for the term usage; for instance marketing materials may present the device by its colloquial term camcorder, while full name on the package and manual is often video camera recorder.
The majority of devices that are capable of recording video are camera phones and digital cameras primarily intended for still pictures, but the term "camcorder" is often restricted to mean a portable, self-contained device having video capture and recording as its primary function.
The earliest types were tape-based camcorders, which recorded analog signals onto videotape cassettes. In the 21st century digital recording became the norm, with tape dwindling away gradually, replaced with other storage media such as internal flash memory, hard drive, and SD card.Camcorders that do not use magnetic tape are often called tapeless camcorders, while camcorders that permit using more than one type of medium, like built-in hard disk drive and memory card, are sometimes called hybrid camcorders.

Tape Recorder: An audio tape recorder, tape deck, or tape machine is an audio storage device that records and plays back sounds, including articulated voices, usually using magnetic tape, either wound on a reel or in a cassette, for storage. In its present day form, it records a fluctuating signal by moving the tape across a tape head that polarizes the magnetic domains in the tape in proportion to the audio signal.