[optacon-l] Re: Reading LCD monitor with the Optacon

  • From: Mary Emerson <maryemerson@xxxxxxxxxxxxx>
  • To: optacon-l@xxxxxxxxxxxxx
  • Date: Mon, 13 Feb 2012 06:21:20 -0800

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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