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2. Ceiling projector - Wikipedia

   en.wikipedia.org/wiki/Ceiling_projector

   The ceiling projector or cloud searchlight is used to measure the height of the base of clouds (called the ceiling) above the ground. It is used in conjunction with an alidade, usually positioned 1000 ft (300 m) away and wherever possible set at the same level. The projector is normally set at 90°, although 71° 31' may be used, in relation to ...

3. Projection clock - Wikipedia

   en.wikipedia.org/wiki/Projection_clock

   A projection clock (also called ceiling clock) is an analogue or digital clock equipped with a projector that creates an enlarged image of the clock face or display on any surface usable as a projection screen, most often the ceiling. [1] The clock can be placed almost anywhere if only the projected image must be seen.

4. Projection screen - Wikipedia

   en.wikipedia.org/wiki/Projection_screen

   Projection screens may be permanently installed on a wall, as in a movie theater, mounted to or placed in a ceiling using a rollable projection surface that retracts into a casing (these can be motorized or manually operated), painted on a wall, [1] or portable with tripod or floor rising models as in a conference room or other non-dedicated ...

5. Optical head-mounted display - Wikipedia

   en.wikipedia.org/wiki/Optical_head-mounted_display

   An optical head-mounted display (OHMD) is a wearable device that has the capability of reflecting projected images as well as allowing the user to see through it. In some cases, this may qualify as augmented reality (AR) technology.

6. Overhead projector - Wikipedia

   en.wikipedia.org/wiki/Overhead_projector

   In contrast, a modern LCD or DLP projector often uses an Ultra-high-performance lamp which has a higher luminous efficacy and lasts for thousands of hours. [5] A drawback of that technology is the warm up time required for such lamps. Older overhead projectors used a tubular quartz bulb which was mounted above a bowl-shaped polished reflector.

7. Large-format slide projector - Wikipedia

   en.wikipedia.org/wiki/Large-format_slide_projector

   The first large-format slide projectors were built in the middle of the 20th century as background projectors for theaters and opera houses. From the early 50', the german Brand Reiche&Vogel was offering in a catalog a 2000w slide projector using 4.75"x 4.75" (12x12cm) slide or a scroller for film strip of the same size.