[optacon-l] Re: Reading LCD monitor with the Optacon
- From: "cpond" <cpond@xxxxxxxxx>
- To: <optacon-l@xxxxxxxxxxxxx>
- Date: Mon, 13 Feb 2012 10:37:40 -0500
I use the normal lens with the retina to read the LCD screen; no need for
the CRT lens in this case for my laptop's screen.
Charles
-----Original Message-----
From: Mary Emerson
Sent: Monday, February 13, 2012 9:21 AM
To: optacon-l@xxxxxxxxxxxxx
Subject: [optacon-l] Re: Reading LCD monitor with the Optacon
Nancy and list,
Maybe you need to adjust the brightness setting on the CRT display
itself; turn down brightness. Sometimes low brightness and high contrast
work; sometimes low contrast and high brightness work. Also, there are
various ways to adjust the CRT lens itself; try unscrewing the top of
the lens to make it longer, instead of screwing it all the way down into
the lens barrel. Remember, TSI developed at least two types of CRT
lenses, one for CRT screens with larger print, and another for CRTs with
smaller print.
Below, I'm adding the instructions that were included with the CRT lens
for larger print CRTs. If you have an R1D or R1C optacon, the CRT lens
was supposed to work in inverse mode. If you have an optacon 2, adjust
the mode slide switch either in the lowest or highest position; the
middle position is normal, if I recall correctly, and not often used
with a CRT lens. If inverse won't work, use normal mode; Windows often
has dark colors on a light screen.
Here, starting in the next paragraph, are the instructions. Maybe this
information will help somebody else on the list, too.
TELESENSORY SYSTEMS, INC.
3408 Hillview Avenue
P.O. Box 10099
Palo Alto, California 94304
Telephone 415/493-2626 Telex 348352
OPERATING INSTRUCTIONS FOR CRT LENS’* MODULE F1A
INTRODUCTION
The CRT Lens Module F1A is an Optacon accessory that may be attached to
the retina of
a Model R1C/D Optacon to read some Cathode ray Tube terminals. There are
numerous
variations in CRT’s including those which are supposedly identical,
which mean that
one’s own Optacon, the F1A CRT Lens Module, and the specific CRT in
question must
be evaluated together to determine if an effective reading system can be
achieved.
Although the CRT Lens Module is designed to read characters 1/8 to
1/4 inch (3 to 6 mm) tall, there are significant variables which prevent
TSI from
consistently predicting which CRT’s are readable. These include the
brightness and
contrast of the CRT display, the focus adjustment of the CRT, and
presence of a dust
cover with its underlying CRT tube curvature, extraneous light from the
surrounding
room, the refresh rate of the CRT, and the ratio of character height to
width.
FEATURES OF F1A ..’-. - ..--.
The bayonet sleeve which accepts the Optacon retina is on the back side
of the F1A at the
end closest to the user and furthest from the CRT screen during use. The
front end of the
F1A contains three small nylon ball bearings which are positioned
directly against the
CRT ^ screen during use. The features below are described in a sequence
from back to
front.
Bayonet sleeve - accepts the Optacon retina which is inserted with a
push/twist action.
Zoom lens magnification adjustment - The zoom lens adjustment ring is at
the back of the
F1A barrel, just before the barrel makes a right angle turn to the
bayonet sleeve. The ring
has a larger diameter than the barrel. It slides forward and backward
approximately 1/4
inch (6 mm) with the forward position providing the greatest
magnification. The ring can
be locked into position from its ”free-sliding” position by twisting it”
either clockwise or
counter-clockwise relative to to the barrel.
Focus adjustment - Focus is adjusted by varying the length of the
barrel. About 3/4
inch (19 mm) forward from the zoom ring are two smaller knurled rings
having the same
diameter as the barrel. The forward ring is attached to the front half
of the barrel.
Turning it adjusts barrel length. The second ring (toward the back) is a
lock ring. A flat
side on the circumference of the barrel just forward of the two
focus adjustment rings provides a tactile monitor of the number of turns
made while
adjusting barrel length. .^Eleven complete turns will adjust the barrel
from minimum to
maximum length. ^ ’
Light shield - The two inch (51 mm) diameter disk near the front of the
F1A is designed
to shield the CRT from extraneous light. In some situations, this shield
may be
unnecessary. It can be unscrewed from the barrel and removed after
separating the barrel
in two by completely unscrewing the front ^ section beyond its maximum
extension.
Nylon ball bearings - Provide smooth, low-friction movement of the F1A
across both
glass screens and protective dust covers.
SET-UP PROCEDURES
Preliminaries:
The sighted CRT user will generally prefer a very strong contrast
between the characters
and the background. This is usually not ideal for the Optacon. The
Optacon generally
works best when the CRT is very bright, in which case the contrast may
be low. In other
words, both the characters and the background are usually bright when
CRT adjustments
are optimum for Optacon reading. Frequently the best CRT brightness
and/or contrast
settings will result in the appearance of retrace lines on the screen.
Preliminary to evaluating the F1A, one could ask a sighted assistant to
adjust the CRT
brightness and/or contrast controls (if present) to yield characters and
background as
bright as possible without significantly distorting character focus.
Next, use the chart below to make an initial focus (barrel-length)
adjustment. This
adjustment will be based upon two factors: (1) F1A’s are
factory-adjusted at TSI to
various internal lens settings, and (2) CRT’s come with or without cover
screens.
NOTE: For best results with a CRT with cover screen, the screen should
be removed. If
the screen is not removed, you may not be able to read some parameter
information.
CRT Without Cover CRT With Cover ’., Screen ’ Screen’
F1A Lens Setting No. 4 9 complete turns 9 complete turns (reads larger
print)
from minimum. - from ’minimum
F1A Lens Setting No. 7 4 complete turns 1 complete turn^’ (reads smaller
print)
from minimum from minimum
Remove the standard lens module from the Op’tacon retina module and set
it aside in a
safe place. ,
Adjust the zoom ring to minimum magnification by unlocking it, sliding
it back toward
the bayonet sleeve as far as possible, and relocking it.
Now, hold the F1A against the CRT screen. If your Optacon is designed
for left index
finger reading, turn the F1A until the bayonet sleeve (which accepts the
retina) points left.
(If your Optacon is designed for right index finger reading, the bayonet
sleeve should
point right.) Holding the F1A this way, insert the retina module into
the F1A bayonet
sleeve so that the camera cord emerges from the 12 o’clock position.
CRT Light Adjustments:
The following procedures are designed to determine whether the CRT emits
enough light
for the Optacon to operate properly. ’”
1. Both the CRT and the Optacon should be on, with the
Optacon’s normal/invert switch in the invert position.
2. Aim the F1A at a blank screen or blank portion of the dis-
play previously adjusted by a sighted assistant.
3. Turn the Optacon’s threshold counterclockwise until the array
”blooms”. (Namely, all
of the pins are vibrating.) Then back off by turning the threshold
clockwise until the
bloom just disappears.
4. Display a line of ”L’s”across the screen.
5. Leaving the Optacon threshold at the setting in Step 3, scan the
”L’s”. If the Optacon
responds, proceed with
F1A focus adjustments in the next section . If the Optacon does not
respond, increase
CRT contrast and repeat steps
2-5.” If the Optacon still does not react to print with any of the CRT
contrast adjustments
you have made, the F1A you are using is probably not receiving enough
light from your
CRT’s screen and probably will not work with your equipment. Try
evaluating an F1A
with a different factory-adjusted lens setting (if you have one
available), starting again with ”Preliminaries”.
Note: If the ”L’s” appear upside down, remove the retina module from the
F1A, rotate it
180° and replace it.
F1A Focus Adjustments: ’
Ignore image size and leave magnification at a minimum with the zoom
ring all
the way back (toward you) . Try to improve focus by using various barrel
lengths, adjusting Optacon threshold after each barrel length adjustment to
determine if the image is becoming clearer. Try to find the barrel length
adjustment which will provide the best average focus for characters
appearing in
both the corners and the center of the portion of the CRT screen that
you will
want to read.
Magnification Adjustment: .
Using the zoom ring and Optacon’s threshold adjustment, adjust
magnification.
When the magnification is adjusted to provide the correct image size,
the focus
may require readjustment, especially if your F1A has lens setting Number
4. ”
Improving CRT Light Adjustments:
Assuming that previous adjustments were properly made, the F1A should
require
no further focus or magnification adjustments. Next, you want to determine
whether any additional adjustments to the CRT’s intensity and/or
contrast controls
result in clearer images for the Optacon. . -..- , -,.
Before attempting to improve the CRT’s light adjustments, note the ;
Optacon’s
threshold setting and ask a sighted assistant to note the starting point
CRT intensity
and/or contrast settings. Now, without adjusting the F1A, determine whether
variations in the Optacon threshold adjustments and the CRT intensity
and contrast
adjustments provide improved images. If not, return to the settings in
use at the
beginning of this section. Make note of these settings so that next time
you use
this CRT, you will have some way of quickly making the proper settings.
The above instructions assume that the CRT has brightness and contrast
controls.
Not all CRT’s do. Some have a single brightness control which simultaneously
adjusts intensity and ’contrast. Others have no ” external controls. If
you cannot
make the exact adjustment suggested, do the best you can within the
limitations of
your system.
You may notice a beat frequency or periodic pulsation in your Optacon’s
array
when reading the CRT screen. This is due to the fact that some CRT screens
renew their images at a different rate than the Optacon views them. The
Optacon
camera’s scan rate has been adjusted to the average refresh rate of the most
popular CRT’s. This may not be an | exact synchronization with your CRT.
This
electronic incompatibility ’ does not damage your Optacon in any way.
Some CRT cover screens are quite flexible. As a result, you may discover
that a
character is in focus when you are applying very little pressure against
the screen
and out of focus when you apply enough pressure to bend the screen inward.
Performance may be improved by removing the cover screen, if it is
possible and
safe to do so.
3a0
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