[optacon-l] Re: Reading LCD monitor with the Optacon
- From: Nancy Shackelford <ladym74731@xxxxxxxxxxxxxxxx>
- To: <optacon-l@xxxxxxxxxxxxx>
- Date: Mon, 13 Feb 2012 11:01:37 -0600
I shall try this. Thanks.
Nance
Nancy Shackelford
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----- Original Message -----
From: "Mary Emerson" <maryemerson@xxxxxxxxxxxxx>
To: <optacon-l@xxxxxxxxxxxxx>
Sent: Monday, February 13, 2012 8:21 AM
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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