Projection instructions

See visual stimuli equipment for brief descriptions of specific hardware and physical layout. 

Using the InFocus LP350 projector
Determining image size and field of view
Making image adjustments

Using the InFocus 350 DLP projector

The InFocus projector is designed for XVGA (1024x768) resolution display, although it can display other (resampled) resolutions.  Display from higher resolution devices causes some horizontal "pixel jitter".

The manual for the projector is on the table supporting the projector in the equipment room.

To use the projector:

Turn the projector power on:  The power switch is a green button on the left side of the projector in the equipment room.  It takes many seconds for the bulb to light up.  If no video source is connected or detected, a blue screen with the "InFocus" logo will be displayed.

Connect a video source to the projector:  The video source can be the visual stimulus computer at the operator's console, an investigator provided computer, or some other video source. 

For a computer video source at the operator's console, a projection hub and cable is used. Connect the "computer cable" to the hub's video in port and the stimulus computer's video out port, and the stimulus computer monitor's cable to the hub's video out port.

Select projector's source:  If a video source is not automatically detected, press the "source" button on top of the InFocus LP350 to toggle through the possible source channels ("computer 1", "computer 2", "video").

Check projection: The projected image can be checked from within the magnet room (CAUTION: Do not bring any unapproved measurement device into the magnet room), at the magnet bore video monitor at the operator's console, or looking over the projector through the waveguide.

Turn off the projector: At the end of use, be sure to turn off the projector.  The bulb has a 2000 hour life, and the projector will display a warning when this lifetime is nearing an end.  (Note: Do not turn the projector on and off repeatedly. Allow the projector bulb to heat up for at least 5 minutes before turning it off. When hot, the bulb will take a minute to turn on.)


Determining image size and field of view

Apparent field of view: The apparent field of view is the angular dimensions of the projected image from the subject's perspective. The rear projection screen's standard position is just inside the "head" end of the magnet bore, at an apparent distance of ~24" from the subject. The diameter of the projection screen is 13.625".  The largest image that can be fully accomodated at the standard size ratio of 4:3 (width:height) is 11"x8.25". At an apparent distance of 24", these largest image dimensions corresponds to an angular field of view of 26.4x19.8 degrees.

The projection screen can be positioned closer or more distant from the subject, within limits. For the screen positioned at an apparent distance of 16", the corresponding maximum 4:3 image angular field of view will be 39.7x29.8 degrees. This is the approximate maximum apparent field of view that can be practically achieved.

Image size:  The image size for any given projection screen position can be adjusted by changing the pixel dimension of the stimuli (to 1024x768, or 640x480/800x600 with the projector's "resize" parameter "off"), using black on the edges of the projected image (only using the center of the projected image for the stimulus), and/or adjusting the zoom ring on the projector lens. The following chart lists the dot pitch of the image on the rear projection screen at 64" from the front of the projector/telescope lens (24" apparent distance), with various projection parameters:

InFocus LP350 image size at 64"/24"


 full resolution (1024x768)
 800x600
resize on
 640x480
resize on
 800x600
resize off
 640x480
resize off
with telescope
zoomed out
 82 pxl/inch
(image size > screen)
 64 pxl/inch
(image size > screen)
 51 pxl/inch
(image size > screen)
 82 pxl/inch
(image size = 9.8"x7.3"
 82 pxl/inch
(image size = 7.8"x5.9")


zoomed in
 100 pxl/inch
(image size = 10.25"x7.7")
 78 pxl/inch
(image size = 10.25"x7.7")
 62.5 pxl/inch
(image size = 10.25"x7.7")
 100 pxl/inch
(image size = 8"x6")
 100 pxl/inch
(image size = 6.4"x4.8")
without telescope
 zoomed out
 31.25 pxl/inch
(image size > screen)
 24.4  pxl/inch
(image size > screen)
 19.5 pxl/inch
(image size > screen)
 31.25 pxl/inch
(image size > screen)
 31.25 pxl/inch
(image size > screen)

zoomed in
 38.7 pxl/inch
(image size > screen)
 30.2 pxl/inch
(image size > screen)
 24.2 pxl/inch
(image size > screen)
 38.7 pxl/inch
(image size > screen)
 38.7 pxl/inch
(image size > screen)

The image size can also be altered by repositioning of the rear projection screen. The minimum focus distance (without telescope) of the projector is  58", which  is just clear of the end of the magnet.

Video sources are rescaled to "full resolution", with various options available for fitting the video format to the 4:3 projection size ratio. See the InFocus 350 manual for details.
 

Making image adjustments

Image position: The image can be repositioned within a small range by adjusting the positions of the projector or projector/telescope. Do not alter the position of the telescope with respect to the projector without CNI staff assistance.

Raise/lower/level image: Turn the three bolts that pass through the bottom face of the projector stand to ajdust the vertical position of the image.

Shift left/right: Slide the projector base, keeping the lens centered on the waveguide.

Image brightness: If the telescope is being used, adjust the aperture at the exit pupil by moving the bar horizontally. If the projector's controls (see projector manual) are used to adjust the brightness, return them to default values after use.

Focus: The end of the projector's lense barrel can be twisted to adjust the focus within a small range. The minimum focus distance (without telescope) of the projector is  58", which is just clear of the end of the magnet. If the telescope needs adjustment to alter the focus, please seek CNI staff assistance. (When using the telescope, the edges of the image will not be in sharp focus when the center of the image is focused. Stopping down the telescope aperture will minimize the difference in focus, at the expense of image brightness.)

Color balance: If the projector's controls (see projector manual) are used to adjust the color balance, return them to default values after use.