It looks like you're using an Ad Blocker.

Please white-list or disable AboveTopSecret.com in your ad-blocking tool.

Thank you.

 

Some features of ATS will be disabled while you continue to use an ad-blocker.

 

US Patent #US 6506148 B2. -Nervous system manipulation by electromagnetic fields from monitors

page: 5
19
<< 2  3  4    6  7  8 >>

log in

join
share:

posted on Aug, 27 2015 @ 04:12 PM
link   
a reply to: dashen

Yawn, yes...I'm sure he is incorrect!



For a CRT the intensity of an image is expressed in millamperes.

For a liquid crystal display (LCD), the current densities in the definition of image intensity are to be replaced by driving voltages, multiplied by the aperture ratio of the device. For an LCD, image intensities are thus expressed in volts.

It will be shown that for a CRT or LCD screen emissions are caused by fluctuations in image intensity. In composite video however, intensity as defined above is not a primary signal feature, but luminance Y is. For any pixel one has


That part about how the current is replaced by voltage actually shows a lack of understanding about how this would work. While in the LCD, the opacity and color of the crystal filter is controlled by voltage; voltage does not contribute to the intensity of any electromagnetic effects present...only current can do that. In the CRT the pixel intensity is controlled by what we might call "beam current", though that is not quite correct...thus the electron beam develops a magnetic field of it's own...which is the field originally referred to.

As for color and/or brightness pulsations...if done at the right frequency and color...can cause epileptic seizures. But, that is rather a different thing than "stimulation of the skin with weak electromagnetic fields ."




posted on Aug, 27 2015 @ 06:14 PM
link   
a reply to: tanka418

you are just not getting it mate.

Ohm's law[edit]
Main article: Ohm's law
Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance,[7] one arrives at the usual mathematical equation that describes this relationship:[8]

I = frac[V][R]
where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current.[9]


i is current (amps) v is voltage (potential difference) and R is resistance(aperture ratio e.g. size of monitor)
ohms law much?



posted on Aug, 27 2015 @ 06:43 PM
link   

originally posted by: dashen
a reply to: tanka418

you are just not getting it mate.

Ohm's law[edit]
Main article: Ohm's law
Ohm's law states that the current through a conductor between two points is directly proportional to the potential difference across the two points. Introducing the constant of proportionality, the resistance,[7] one arrives at the usual mathematical equation that describes this relationship:[8]

I = frac[V][R]
where I is the current through the conductor in units of amperes, V is the potential difference measured across the conductor in units of volts, and R is the resistance of the conductor in units of ohms. More specifically, Ohm's law states that the R in this relation is constant, independent of the current.[9]


i is current (amps) v is voltage (potential difference) and R is resistance(aperture ratio e.g. size of monitor)
ohms law much?


lol...

Well...while Ohm's law does have some application here, you clearly do not understand where, or how.

But, it's kind of like this...Amperes of current, not volts of potential, are what determine the strength of an electromagnetic field. Please check that out!

An electromagnetic field is created by the tube, mostly by the current flow of the electron beam...its that whole thing where current flow in a conductor creates an electromagnetic field; check that out too!

The LCD is a voltage controlled device...in cases like this that is due to the very high impedance or resistance of it's control inputs; thus very little current can flow, resulting in almost no electromagnetic field.

Typical voltages used in the tube: 18,000 volts
Typical voltages used in the LCD: 12 volts.

Oh, and yes...as an msee I know about Ohm's law.



posted on Aug, 27 2015 @ 10:21 PM
link   
a reply to: tanka418
thought you would get a lol out of that last one
yaaargghh.
electromagnetic radiation in the visible and near infrared and uv range.
there is no field.
forget the field.
just photonic pulses.
so sleepy.
very sleepy.
edit on 27-8-2015 by dashen because: zzzzzzzzzzzz



posted on Aug, 27 2015 @ 10:37 PM
link   
a reply to: tanka418

also, get a load of this
and do you know how to use ohms law as a regular equation?
where r is a constant you can interchange i with v



posted on Aug, 31 2015 @ 05:25 PM
link   
So that is it then?
No more shills?
No more ignoring the major body of evidence and making straw man arguments?
it's a good feeling....



posted on Aug, 31 2015 @ 05:39 PM
link   

originally posted by: dashen
So that is it then?
No more shills?
No more ignoring the major body of evidence and making straw man arguments?
it's a good feeling....


Evidence of what?!!!???

That you have stumbled across a patient and paper you can not understand written by a person with little more understanding than you have?

Dude!!! This guy states his premise, then ignores it! He claims (partially correct) that there are certain electromagnetic effects, then attempts to justify them with something entirely unrelated.
Then you elevate him to the status of a demigod...WOW!!!

I have agreed with what is correct and attempted to correct that which is not; and you call me a shill! Now there's a way to learn...then you try to gloat! Seriously bad form!!

Again, and for the record, LCD displays do not, can not, produce the kinds of electromagnetic effects you and your author think.

There needs to be a junk box around here.



posted on Aug, 31 2015 @ 05:57 PM
link   
a reply to: tanka418

Is English your second language?
Light pulses.
read the words image pulsation.
you have obviously no understanding of rudimentary electric principles.
One that electromagnetic pulses include visible light.
second that you obviously don't understand ohms law that voltage and current are interchangeable in certain instances.
Third a physicist who works with DARPA and other defense engineering firms since the 60s better well have an
understanding of basic Electric theory and circuitry.
Something so far you have yet to show.
If you would have bothered reading the whole thing you would clearly see that he says that the electromagnetic effect of a CRT is only incidental to the effect that he wishes to facilitate with a pulsating image.
I've only repeated it about a dozen times.
but you are still off on your trip.
Address any of the points that I've made or continue looking like a joker.



edit on 31-8-2015 by dashen because: (no reason given)



posted on Aug, 31 2015 @ 08:36 PM
link   

originally posted by: dashen
a reply to: tanka418

Is English your second language?
Light pulses.
read the words image pulsation.


Let us visit the original abstract...


ABSTRACT
Physiological effects have been observed in a human subject in response to stimulation of the skin with weak electromagnetic fields that are pulsed


As you can see this "response" is quite specific, and it is a "skin response". This virtually eliminates light pulses, specifically.



you have obviously no understanding of rudimentary electric principles.


Yet, I'm a retired Electrical Engineer (MSEE)...I'm also a computer scientist, and software engineer (MSCS).



One that electromagnetic pulses include visible light.


I did not say otherwise. I argued that these light pulses do not apply within the context of this paper.



second that you obviously don't understand ohms law that voltage and current are interchangeable in certain instances.


lol



Third a physicist who works with DARPA and other defense engineering firms since the 60s better well have an
understanding of basic Electric theory and circuitry.


Actually, I've found that other disciplines tend to lack understanding of areas they have not specialized in. For instance, a physicist, astronomer, etc. will have little real understanding of data behavior, where a computer scientist will have in depth understanding. Conversely, that computer scientist will lack understanding of astronomy.

In short; it is unlikely that our physicist will have a greater understanding than an engineer.



Something so far you have yet to show.


Oh really!!!??

So my explanation of how the CRT develops the signal your physicist is interested in doesn't show my understanding? Wanna try again?




If you would have bothered reading the whole thing you would clearly see that he says that the electromagnetic effect of a CRT is only incidental to the effect that he wishes to facilitate with a pulsating image.


As I said; "Dude!!! This guy states his premise, then ignores it!"



I've only repeated it about a dozen times.
but you are still off on your trip.
Address any of the points that I've made or continue looking like a joker.




Yes off on my trip...perhaps you should pay attention and maybe learn something new...

So, I've addressed all of your phantom points, and, well they ain't so much more than a misunderstanding. And , in case you haven't been paying attention; you are half correct.

edit on 31-8-2015 by tanka418 because: (no reason given)



posted on Aug, 31 2015 @ 08:55 PM
link   
a reply to: tanka418

So the beginning is a an overview of the principals of the invention, the summary and what follows is what you seem to be hellbent on ignoring in your responses.
So here it goes again..

.

SUMMARY

Computer monotors and TV monitors can be made to emit weak low-frequency electromagnetic fields merely by pulsing the intensity of displayed images. Experiments have shown that the ½ Hz sensory resonance can be excited in this manner in a subject near the monitor. The 2.4 Hz sensory resonance can also be excited in this fashion. Hence, a TV monitor or computer monitor can be used to manipulate the nervous system of nearby people.

The implementations of the invention are adapted to the source of video stream that drives the monitor, be it a computer program, a TV broadcast, a video tape or a digital video disc (DVD).

For a computer monitor, the image pulses can be produced by a suitable computer program. The pulse frequency may be controlled through keyboard input, so that the subject can tune to an individual sensory resonance frequency. The pulse amplitude can be controlled as well in this manner. A program written in Visual Basic(R) is particularly suitable for use on computers that run the Windows 95(R) or Windows 98(R) operating system. The structure of such a program is described. Production of periodic pulses requires an accurate timing procedure. Such a procedure is constructed from the GetTimeCount function available in the Application Program Interface (API) of the Windows operating system, together with an extrapolation procedure that improves the timing accuracy.

Pulse variability can be introduced through software, for the purpose of thwarting habituation of the nervous system to the field stimulation, or when the precise resonance frequency is not known. The variability may be a pseudo-random variation within a narrow interval, or it can take the form of a frequency or amplitude sweep in time. The pulse variability may be under control of the subject.

The program that causes a monitor to display a pulsing image may be run on a remote computer that is connected to the user computer by a link; the latter may partly belong to a network, which may be the Internet.

For a TV monitor, the image pulsing may be inherent in the video stream as it flows from the video source, or else the stream may be modulated such as to overlay the pulsing. In the first case, a live TV broadcast can be arranged to have the feature imbedded simply by slightly pulsing the illumination of the scene that is being broadcast. This method can of course also be used in making movies and recording video tapes and DVDs.

Video tapes can be edited such as to overlay the pulsing by means of modulating hardware. A simple modulator is discussed wherein the luminance signal of composite video is pulsed without affecting the chroma signal. The same effect may be introduced at the consumer end, by modulating the video stream that is produced by the video source. A DVD can be edited through software, by introducing pulse-like variations in the digital RGB signals. Image intensity pulses can be overlaid onto the analog component video output of a DVD player by modulating the luminance signal component. Before entering the TV set, a television signal can be modulated such as to cause pulsing of the image intensity by means of a variable delay line that is connected to a pulse generator.

Certain monitors can emit electromagnetic field pulses that excite a sensory resonance in a nearby subject, through image pulses that are so weak as to be subliminal. This is unfortunate since it opens a way for mischievous application of the invention, whereby people are exposed unknowingly to manipulation of their nervous systems for someone else's purposes. Such application would be unethical and is of course not advocated. It is mentioned here in order to alert the public to the possibility of covert abuse that may occur while being online, or while watching TV, a video, or a DVD.

DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates the electromagnetic field that emanates from a monitor when the video signal is modulated such as to cause pulses in image intensity, and a nearby subject who is exposed to the field.

FIG. 2 shows a circuit for modulation of a composite video signal for the purpose of pulsing the image intensity.

FIG. 3 shows the circuit for a simple pulse generator.

FIG. 4 illustrates how a pulsed electromagnetic field can be generated with a computer monitor.

FIG. 5 shows a pulsed electromagnetic field that is generated by a television set through modulation of the RF signal input to the TV.

FIG. 6 outlines the structure of a computer program for producing a pulsed image.

FIG. 7 shows an extrapolation procedure introduced for improving timing accuracy of the program of FIG. 6.

FIG. 8 illustrates the action of the extrapolation procedure of FIG. 7.

FIG. 9 shows a subject exposed to a pulsed electromagnetic field emanating from a monitor which is responsive to a program running on a remote computer via a link that involves the Internet.

FIG. 10 shows the block diagram of a circuit for frequency wobbling of a TV signal for the purpose of pulsing the intensity of the image displayed on a TV monitor.

FIG. 11 depicts schematically a recording medium in the form of a video tape with recorded data, and the attribute of the signal that causes the intensity of the displayed image to be pulsed.

FIG. 12 illustrates how image pulsing can be embedded in a video signal by pulsing the illumination of the scene that is being recorded.

FIG. 13 shows a routine that introduces pulse variability into the computer program of FIG. 6.

FIG. 14 shows schematically how a CRT emits an electromagnetic field when the displayed image is pulsed.

FIG. 15 shows how the intensity of the image displayed on a monitor can be pulsed through the brightness control terminal of the monitor.

FIG. 16 illustrates the action of the polarization disc that serves as a model for grounded conductors in the back of a CRT screen.

FIG. 17 shows the circuit for overlaying image intensity pulses on a DVD output.

FIG. 18 shows measured data for pulsed electric fields emitted by two different CRT type monitors, and a comparison with theory.

DETAILED DESCRIPTION

Computer monitors and TV monitors emit electromagnetic fields. Part of the emission occurs at the low frequencies at which displayed images are changing. For instance, a rythmic pulsing of the intensity of an image causes electromagnetic field emission at the pulse frequency, with a strength proportional to the pulse amplitude. The field is briefly referred to as “screen emission”. In discussing this effect, any part or all what is displayed on the monitor screen is called an image. A monitor of the cathode ray tube (CRT) type has three electron beams, one for each of the basic colors red, green, and blue. The intensity of an image is here defined as

I=∫j dA, (1)

where the integral extends over the image, and

j=jr+jg+jb, (2)

jr, jg, and jb being the electric current densities in the red, green, and blue electron beams at the surface area dA of the image on the screen. The current densities are to be taken in the distributed electron beam model, where the discreteness of pixels and the raster motion of the beams are ignored, and the back of the monitor screen is thought to be irradiated by diffuse electron beams. The beam current densities are then functions of the coordinates x and y over the screen. The model is appropriate since we are interested in the electromagnetic field emision caused by image pulsing with the very low frequencies of sensory resonances, whereas the emissions with the much higher horizontal and vertical sweep frequencies are of no concern. For a CRT the intensity of an image is expressed in millamperes.

For a liquid crystal display (LCD), the current densities in the definition of image intensity are to be replaced by driving voltages, multiplied by the aperture ratio of the device. For an LCD, image intensities are thus expressed in volts.

It will be shown that for a CRT or LCD screen emissions are caused by fluctuations in image intensity. In composite video however, intensity as defined above is not a primary signal feature, but luminance Y is. For any pixel one has

Y=0.299R+0.587G+0.114B, (3)

where R, G, and B are the intensities of the pixel respectively in red, green and blue, normalized such as to range from 0 to 1. The definition (3) was provided by the Commission Internationale de l'Eclairage (CIE), in order to account for brightness differences at different colors, as perceived by the human visual system. In composite video the hue of the pixel is determined by the chroma signal or chrominance, which has the components R-Y and B-Y It follows that pulsing pixel luminance while keeping the hue fixed is equivalent to pulsing the pixel intensity, up to an amplitude factor. This fact will be relied upon when modulating a video stream such as to overlay image intensity pulses.

It turns out that the screen emission has a multipole expansion wherein both monopole and dipole contributions are proportional to the rate of change of the intensity I of (1). The higher order multipole contributions are proportional to the rate of change of moments of the current density j over the image, but since these contributions fall off rapidly with distance, they are not of practical importance in the present context. Pulsing the intensity of an image may involve different pulse amplitudes, frequencies, or phases for different parts of the image. Any or all of these features may be under subject control.

The question arises whether the screen emission can be strong enough to excite sensory resonances in people located at normal viewing distances from the monitor. This turns out to be the case, as shown by sensory resonance experiments and independently by measuring the strength of the emitted electric field pulses and comparing the results with the effective intensity window as explored in earlier work.

One-half Hertz sensory resonance experiments have been conducted with the subject positioned at least at normal viewing distance from a 15″ computer monitor that was driven by a computer program written in Visual Basic(R), version 6.0 (VB6). The program produces a pulsed image with uniform luminance and hue over the full screen, except for a few small control buttons and text boxes. In VB6, screen pixel colors are determined by integers R, G, and B, that range from 0 to 255, and set the contributions to the pixel color made by the basic colors red, green, and blue. For a CRT-type monitor, the pixel intensities for the primary colors may depend on the RGB values in a nonlinear manner that will be discussed. In the VB6 program the RGB values are modulated by small pulses ΔR, ΔG, ΔB, with a frequency that can be chosen by the subject or is swept in a predetermined manner. In the sensory resonance experiments mentioned above, the ratios ΔR/R, ΔG/G, and ΔB/B were always smaller than 0.02, so that the image pulses are quite weak. For certain frequencies near ½ Hz, the subject experienced physiological effects that are known to accompany the excitation of the ½ Hz sensory resonance as mentioned in the Background Section. Moreover, the measured field pulse amplitudes fall within the effective intensity window for the ½ Hz resonance, as explored in earlier experiments and discussed in the '874, '744, '922, and '304 patents. Other experiments have shown that the 2.4 Hz sensory resonance can be exited as well by screen emissions from monitors that display pulsed images.

These results confirm that, indeed, the nervous system of a subject can be manipulated through electromagnetic field pulses emitted by a nearby CRT or LCD monitor which displays images with pulsed intensity.



posted on Aug, 31 2015 @ 09:00 PM
link   
a reply to: tanka418

I disagree with your posts in a lot of other threads, but in this one, it's quite clear that you know what you are talking about, and that you are absolutely correct. Bravo.

edit on 8/31/2015 by AdmireTheDistance because: (no reason given)



posted on Aug, 31 2015 @ 09:20 PM
link   

originally posted by: AdmireTheDistance
a reply to: tanka418

I disagree with your posts in a lot of other threads, but in this one, it's quite clear that you know what you are talking about, and that your are absolutely correct. Bravo.


The summary repeatedly mentioned pulsed images.
the whole thing is based on pulsed images.
are you not reading what im reading?
You guys are getting confused by the introduction i think .



posted on Aug, 31 2015 @ 10:07 PM
link   
a reply to: dashen

yes, yes...I'm aware of all that and, as I've already said the issue I have is:



For a liquid crystal display (LCD), the current densities in the definition of image intensity are to be replaced by driving voltages, multiplied by the aperture ratio of the device. For an LCD, image intensities are thus expressed in volts.


And, again, as I said; voltage does not determine the strength of an electromagnetic field, current does. A modern LCD is a "voltage driven or operated device". It is the nature of the technology used, it is also in the nature of the technology to limit the total power of the LCD monitor to only a few watts, which means that, although the voltage is only 12 volts, the current is similarly small. Divide that by a few million pixels and Kirchhoff will tell you there is no energy in an individual pixel, Course then again with only a few amps (maybe 5) and only one "turn" Maxwell, and several others will insist there is virtually no electromagnetic field.

Please don't start with your incorrect notions of how voltage and current may be interchangeable under some conditions...it an illusion not unlike making 2 + 2 = 5...ie: it may "look" real; it's not.

A LCD device will have a negligible electromagnetic field. A CRT will generate a significantly larger signature...



posted on Aug, 31 2015 @ 10:09 PM
link   
a reply to: AdmireTheDistance
Ty...I try...
Do something good from time to time...



posted on Aug, 31 2015 @ 10:29 PM
link   
a reply to: tanka418

again with the field. good lordy.


Computer monotors and TV monitors can be made to emit weak low-frequency electromagnetic fields merely by pulsing the intensity of displayed images. Experiments have shown that the ½ Hz sensory resonance can be excited in this manner in a subject near the monitor. The 2.4 Hz sensory resonance can also be excited in this fashion. Hence, a TV monitor or computer monitor can be used to manipulate the nervous system of nearby people.


do you see what is written here?
image intensity pulsed at 1/2 Hz and 2.4 Hz.
no fields to speak of except in the visual range.


where R, G, and B are the intensities of the pixel respectively in red, green and blue, normalized such as to range from 0 to 1. The definition (3) was provided by the Commission Internationale de l'Eclairage (CIE), in order to account for brightness differences at different colors, as perceived by the human visual system. In composite video the hue of the pixel is determined by the chroma signal or chrominance, which has the components R-Y and B-Y It follows that pulsing pixel luminance while keeping the hue fixed is equivalent to pulsing the pixel intensity, up to an amplitude factor. This fact will be relied upon when modulating a video stream such as to overlay image intensity pulses.


See what that says?
no extra voltage necessary.

edit on 31-8-2015 by dashen because: (no reason given)



posted on Aug, 31 2015 @ 10:51 PM
link   
a reply to: tanka418

ok, lets at least agree what were arguing about. you say that an LCD monitor doesnt use enough current to generate an "electromegnetic field" and/or "magnetic field"
I say the image displayed on the actual monitor is the "electromagnetic radiation" in question and that a "magnetic field" is not the matter being discussed in the patent.
you say ""That part about how the current is replaced by voltage actually shows a lack of understanding about how this would work. While in the LCD, the opacity and color of the crystal filter is controlled by voltage; voltage does not contribute to the intensity of any electromagnetic effects present...only current can do that.'
I say the patent claims that pixel luminance intensity is a factor of RGB values and not actual voltage or current.

is that right?

edit on 31-8-2015 by dashen because: (no reason given)



posted on Aug, 31 2015 @ 11:15 PM
link   
Nevermind.
edit on 3120150820151 by Domo1 because: (no reason given)



posted on Aug, 31 2015 @ 11:28 PM
link   

originally posted by: dashen
a reply to: tanka418

again with the field. good lordy.


Computer monotors and TV monitors can be made to emit weak low-frequency electromagnetic fields merely by pulsing the intensity of displayed images. Experiments have shown that the ½ Hz sensory resonance can be excited in this manner in a subject near the monitor. The 2.4 Hz sensory resonance can also be excited in this fashion. Hence, a TV monitor or computer monitor can be used to manipulate the nervous system of nearby people.


do you see what is written here?
image intensity pulsed at 1/2 Hz and 2.4 Hz.
no fields to speak of except in the visual range.


Did you happen to catch this yet?


ABSTRACT
Physiological effects have been observed in a human subject in response to stimulation of the skin with weak electromagnetic fields that are pulsed


Its that whole "stimulation of the skin" that is shooting you down. Here is an experiment you might try; Take your shirt off, so that you have plenty of exposed skin. Have somebody using a LED flashlight shine the light on you back; turning it on an off at random.

Record what you sense, and let us know how much you can sense when the light is on.

The point here is that the presence of light is not generally sensed by the skin, especially when it is not very bright r coherent.

Honestly I'm surprised you haven't figured out that the brighter the image, the stronger the electromagnetic field, and that is his while point; pulsing the image, in turn pulses the electromagnetic field. And, this field is supposed to be weak, hence some of the verbiage throughout the paper, starting in the abstract.


now then, he speaks about computer monitors and tv monitors, yet, if you pay attention, you should notice that he is referring to old CRT monitors; where all of the comments made by your author are indeed correct. None of his remarks apply well to the LCD, which is an entirely different technology.



posted on Aug, 31 2015 @ 11:43 PM
link   

originally posted by: dashen
a reply to: tanka418

ok, lets at least agree what were arguing about. you say that an LCD monitor doesnt use enough current to generate an "electromegnetic field" and/or "magnetic field"
I say the image displayed on the actual monitor is the "electromagnetic radiation" in question and that a "magnetic field" is not the matter being discussed in the patent.


You are aware that, in this instance, the electromagnetic field is the same as the magnetic field. In face the only difference is that the electromagnetic field is created by the orderly movement of electrons along a compact path. And a magnetic field is created by the alignment of magnetic dipoles within a material.

What is being discussed in the patient is the effect of weak electromagnetic fields on the skin.




you say ""That part about how the current is replaced by voltage actually shows a lack of understanding about how this would work. While in the LCD, the opacity and color of the crystal filter is controlled by voltage; voltage does not contribute to the intensity of any electromagnetic effects present...only current can do that.'
I say the patent claims that pixel luminance intensity is a factor of RGB values and not actual voltage or current.

is that right?


No.

RGB values are entirely dependent on either voltage, or timing and current. In the LCD the crystal filter is controlled by voltage, in the CRT color and brightness are controlled by both current and timing...the beam must be striking an appropriate colored phosphor dot.



posted on Sep, 1 2015 @ 12:21 AM
link   
a reply to: tanka418

well, theres this from the patent

Screen emissions also occur for liquid crystal displays (LCD). The pulsed electric fields may have considerable amplitude for LCDs that have their driving electrodes on opposite sides of the liquid crystal cell, for passive matrix as well as for active matrix design, such as thin film technology (TFT). For arrangements with in-plane switching (IPS) however, the driving electrodes are positioned in a single plane, so that the screen emission is very small. For arrangements other than IPS, the electric field is closely approximated by the fringe field of a two-plate condenser, for the simple case that the image is uniform and extends over the full screen. For a circular LCD screen with radius R, the field on the center line can be readily calculated as due to pulsed dipoles that are uniformly distributed over the screen, with the result

E d(z)=(½)VR 2/(z 2 +R 2)[fraction (3/2)],  (21)

where Ed(z) is the amplitude of the pulsed electric field at a distance z from the screen and V is a voltage pulse amplitude, in which the aperture ratio of the LCD has been taken into account. Eq. (21) can be used as an approximation for screens of any shape, by taking R as the radius of a circle with the same area as the screen. The result applies to the case that the LCD does not have a ground connection, so that the top and bottom electrodes are at opposite potential, i.e., V/2 and −V/2.

If one set of LCD electrodes is grounded, monopoles are needed to keep these electrodes at zero potential, much as in the case of a CRT discussed above. The LCD situation is simpler however, as there is no charge injection by electron beams, so that the potentials on the top and bottom plates of the condenser in the model are spatially uniform. From (14) it is seen that monopoles, distributed over the disc of radius R in the plane z=0 such as to provide on the disc a potential V/2, induce on the symmetry axis a potential φ  ( z ) = 1 π  V     β  ( R ) . ( 22 )

Figure US06506148-20030114-M00008
Differentiating with respect to z gives the electric field on the symmetry axis E m  ( z ) = zVR  z   π  ( z 2 + R 2 ) , ( 23 )

Figure US06506148-20030114-M00009
induced by the pulsed monopoles. For an LCD with one set of electrodes grounded, the pulsed electric field for screen voltage pulse amplitude V at a distance z from the screen on the center line has an amplitude that is the sum of the parts (21) and (23). The resultant electric field in the back is relatively small, due to the change in sign in the monopole field that is caused by the factor z/|z|. Therefore, screen emissions in front of an LCD can be kept small simply by having the grounded electrodes in front.

As a check on the theory, the pulsed electric field emitted by the 3″ LCD-TFT color screen of the camcorder mentioned above has been measured at eleven points on the center line of the screen, ranging from 4.0 cm to 7.5 cm. The pulsed image was produced by playing back the video recording of the 15″ computer monitor that was made while running the VB6 program discussed above, for a image intensity pulse frequency of ½ Hz, R=G=B=K, modulated around K=127 with an amplitude ΔK=51. After normalization to a uniform full screen image with 100% intensity modulation by using the nonlinear relation (20), the experimental data were fitted to the theoretical curve that expresses the sum of the fields (21) and (23). The effective screen pulse voltage amplitude V was found to be 2.1 volt. The relative standard deviation in V for the fit is 5.1%, which shows that theory and experiment are in fairly good agreement.



new topics

top topics



 
19
<< 2  3  4    6  7  8 >>

log in

join