Home |
Search |
Today's Posts |
|
Electronics Repair (sci.electronics.repair) Discussion of repairing electronic equipment. Topics include requests for assistance, where to obtain servicing information and parts, techniques for diagnosis and repair, and annecdotes about success, failures and problems. |
Reply |
|
LinkBack | Thread Tools | Display Modes |
#1
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
Is there such a thing ?
I know how LCDs work and it's obvious for the most part, polarized light is coming out of them. Years ago I was getting gas and wearing polarized sunglasses. I couldn't see the display on the pump, I thought it was defunct actually, things break. But I look closer of course and my head tilts a bit and I begine to see it. So I tilt my head alot and of course it dawned on me.. It was polarized the wrong way. I believe I am qualified to say the engineer made it the wrong way because for polarized sunglasses to work they must have a certain polar orientation.. Glare contains more light of one polarization than the other because of being reflected at a somewhat oblique angle. It is "squished". We on the same page here ? As such, the engineer who designed the display should have known which polarization NOT to use and designed accordingly. Oh yes it is far fetched to ask a guy to think of everything like that, but that's why they get the big bucks. I can bitch, but not draw and quarter the dude. Anyway the other day my buddy shows up and he's got new glasses and though not tinted, they are supposedly polarized. I know a little optics and I had a look at his glasses and I see one his main problem is astigmatism. Then he tells me they're polarized so I broke out my cellphone and looked through the lenses while turning, but it didn't darken. I'm thinking maybe they can't polarize it so well not tinted but that's bull**** because it just can't work that way. So either his glasses are not really polarized or my elcheapo phone has an unpolarizer. I'm sure that if an unpolarizer exists it would be in use because alot of people have polarized sunglasses. However I am having a hard time fathoming just how such a thing would work. In a way it would have to produce something that is not there. If such a "filter" exists, it is just one of those things of which I am not yet aware. Would a diffuser unpolarize light ? Damifino. Also, LCD TVs. Take it a step further, if you have an LCD projection set, is the light still polarized when it hits the screen ? Yahoo answers fell flat on their face with this one. First of all the question was FUBARed IMO. The OP was talking about multiple filters and how if at 45 degrees and all this ****, bla bla bla. Google kept trying to go for unpolarized, which is no good of course. Any of that type of engineer around here like to field the question ? J |
#3
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
On 11/07/2012 12:32 PM, wrote:
Is there such a thing ? I know how LCDs work and it's obvious for the most part, polarized light is coming out of them. Years ago I was getting gas and wearing polarized sunglasses. I couldn't see the display on the pump, I thought it was defunct actually, things break. But I look closer of course and my head tilts a bit and I begine to see it. So I tilt my head alot and of course it dawned on me. It was polarized the wrong way. I believe I am qualified to say the engineer made it the wrong way because for polarized sunglasses to work they must have a certain polar orientation. Glare contains more light of one polarization than the other because of being reflected at a somewhat oblique angle. It is "squished". We on the same page here ? As such, the engineer who designed the display should have known which polarization NOT to use and designed accordingly. Oh yes it is far fetched to ask a guy to think of everything like that, but that's why they get the big bucks. I can bitch, but not draw and quarter the dude. Anyway the other day my buddy shows up and he's got new glasses and though not tinted, they are supposedly polarized. I know a little optics and I had a look at his glasses and I see one his main problem is astigmatism. Then he tells me they're polarized so I broke out my cellphone and looked through the lenses while turning, but it didn't darken. I'm thinking maybe they can't polarize it so well not tinted but that's bull**** because it just can't work that way. So either his glasses are not really polarized or my elcheapo phone has an unpolarizer. I'm sure that if an unpolarizer exists it would be in use because alot of people have polarized sunglasses. However I am having a hard time fathoming just how such a thing would work. In a way it would have to produce something that is not there. If such a "filter" exists, it is just one of those things of which I am not yet aware. Would a diffuser unpolarize light ? Damifino. Also, LCD TVs. Take it a step further, if you have an LCD projection set, is the light still polarized when it hits the screen ? Yahoo answers fell flat on their face with this one. First of all the question was FUBARed IMO. The OP was talking about multiple filters and how if at 45 degrees and all this ****, bla bla bla. Google kept trying to go for unpolarized, which is no good of course. Any of that type of engineer around here like to field the question ? J A polymer quarter-wave plate after the polarizer makes the output more or less circularly polarized, so that polaroid sunglasses pass half the light regardless of which way they're rotated. I don't know how fancy they get, but by using multiple layers of stretched polymer, you can make very nearly achromatic quarter wave plates. Otherwise the sunglasses would cause the colour to change slightly depending on which way the display was oriented. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net |
#4
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
Seriously excellent pics. It's not the cool lookingness of it, it's the way it was made. However does it prove that it unpolarizes the light or just gives it a twist naturally, like an LCD would ?
Anything to do with circularly polarized light does nothing to answer this. I do find it an interesting subject though. Circularly polarized light is not likely to be usable by LCD displays because twisting the light would make no differece. At any rate, I am talking about something that actually unpolarizes polarized light. Does such a thing exist ? Those pictures don't prove it because under those test conditions all it has to do is twist a bit. It might be interesting to see a motion video of that and have the cameraperson tilt the camera one way and the other and see what happens. J |
#6
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
|
#7
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
On 11/08/2012 12:05 AM, isw wrote:
In , wrote: Seriously excellent pics. It's not the cool lookingness of it, it's the way it was made. However does it prove that it unpolarizes the light or just gives it a twist naturally, like an LCD would ? Anything to do with circularly polarized light does nothing to answer this. I do find it an interesting subject though. Circularly polarized light is not likely to be usable by LCD displays because twisting the light would make no differece. Circular polarizers are commonly used for improving contrast on displays where (1) there are conductive shiny parts inside, and (2) the light is generated in the display (examples would be Nixie tubes and vacuum-fluorescents). Light that goes in gets circularly polarized, but when it is reflected from an electrical conductor the "rotation" is reversed and it can't get back out again. Light generated inside the display loses some intensity passing through the circular polarizer, but nowhere near as much as the reflected light. Circular polarizers are also used on some LCDs for similar reasons. At any rate, I am talking about something that actually unpolarizes polarized light. Does such a thing exist ? Those pictures don't prove it because under those test conditions all it has to do is twist a bit. It might be interesting to see a motion video of that and have the cameraperson tilt the camera one way and the other and see what happens. Light that has never been polarized has "waves" at all angles. After it's passed through a polarizer, the only waves that get through are all going the same way. Passing polarized light through various things can change the angle of the polarization, but I don't think it can be randomized again. Isaac Polarization is usually defined in terms of the E field direction, i.e. E_0 in the usual expression for a monochromatic plane wave, E(x,t) = Re{E_0 exp(i(k dot x - omega*t) }, where x is the position vector (i.e. the location of the observation point in space) and k is the propagation vector, also called the spatial frequency vector. The energy carried by any light beam is proportional to |E|**2. (Strictly speaking it's proportional to the vector cross product of E and H, but in any given linear medium, |H| is proportional to |E|.) E is a vector, so it has to have a direction and a nonzero magnitude at any instant if there's power flowing. (|E| can be zero if the polarization is exactly linear, but only for an instant.) Thermal light has no time-averaged polarization, but that's because it's very broadband. Sunlight has a polarization vector that changes on the scale of a femtosecond or two. Once the light has been put through a polarizer, there's no way to recover that very rapid variation, but there are various approximate methods for making "depolarizers". For displays and other such things, circular polarizers are the most common sort of depolarizer, because they fix the polaroid sunglass problem, they're cheap, and that's all that's needed. Note that a circular polarizer so-called doesn't actually work analogously to a linear polarizer--it's a film polarizer laminated with a quarter-wave plate on one side, whereas in order for it to pass one helicity unaltered, it would need a waveplate on each side. For display use, you put the waveplate on the outside, facing the viewer, so that it selects one linear polarization from the LCD as normal, and then converts it to circular, so that the viewer's sunglasses don't cause problems. Other approaches sometimes used in instruments are rotating ground-glass diffusers, which make the polarization change on the scale of hundreds of microseconds at best, or Cornu depolarizers, which are waveplates whose retardation varies rapidly across the field of view. Cornu depolarizers are mostly used in grating spectrometers, where they can adequatly homogenize out the polarization dependence of the grating. They're not much use otherwise. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC Optics, Electro-optics, Photonics, Analog Electronics 160 North State Road #203 Briarcliff Manor NY 10510 hobbs at electrooptical dot net http://electrooptical.net |
#8
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
On Nov 7, 11:56*am, Cydrome Leader wrote:
...snip... Same effect here with some safety glasses, you can see the stresses in the lense against the frames as well http://www.panix.com/~presence/D700-...s-02-15-09.jpg Is it possible to see the polarized effect with the naked eye? On these types of glasses, I see the stresses at the corners where plastic is mounted as rainbow hues, very disturbing - interpret as cheapness. |
#9
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
Robert Macy wrote:
On Nov 7, 11:56?am, Cydrome Leader wrote: ...snip... Same effect here with some safety glasses, you can see the stresses in the lense against the frames as well http://www.panix.com/~presence/D700-...s-02-15-09.jpg Is it possible to see the polarized effect with the naked eye? On no. these types of glasses, I see the stresses at the corners where plastic is mounted as rainbow hues, very disturbing - interpret as cheapness. well, anything optical made out of plastic is cheap to start with. There's going to be streeses in mounted lenses. I've noticed it in glasse lenses in metal frames as well. |
#10
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
Robert Macy wrote:
Is it possible to see the polarized effect with the naked eye? On these types of glasses, I see the stresses at the corners where plastic is mounted as rainbow hues, very disturbing - interpret as cheapness. The human eye can "sort of" detect polarisation of light. http://en.wikipedia.org/wiki/Haidinger%27s_brush I can see it; it's easy with practice. 1) Clear blue sky near sunrise or sunset : Look vertically up and spin yourself around by moving your feet. You will look a tit, but it's the best way to see it easily. 2) LCD monitor. Large clear area of white background. Again, rotate your head, so your head is vertical (normal position), then horizontal, etc.. In both cases, you are looking for a yellow-ish "bow tie" shape, at the VERY CENTRE of your vision. The bits that aren't yellow, which bits also form a bow-tie shape, appear (very) slightly blue-ish. Personally, I find that the yellow is far easier to see than the blue. Martin |
#11
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
I am talking about something that actually unpolarizes
polarized light. Does such a thing exist? Yes. A non-metallic reflective surface. |
#12
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
On Nov 9, 4:33*pm, Fleetie wrote:
Robert Macy wrote: Is it possible to see the polarized effect with the naked eye? On these types of glasses, I see the stresses at the corners where plastic is mounted as rainbow hues, very disturbing - interpret as cheapness. The human eye can "sort of" detect polarisation of light. http://en.wikipedia.org/wiki/Haidinger%27s_brush I can see it; it's easy with practice. 1) Clear blue sky near sunrise or sunset : Look vertically up * *and spin yourself around by moving your feet. You will look * *a tit, but it's the best way to see it easily. 2) LCD monitor. Large clear area of white background. Again, rotate * *your head, so your head is vertical (normal position), then * *horizontal, etc.. In both cases, you are looking for a yellow-ish "bow tie" shape, at the VERY CENTRE of your vision. The bits that aren't yellow, which bits also form a bow-tie shape, appear (very) slightly blue-ish. Personally, I find that the yellow is far easier to see than the blue. Martin Thanks for the detail experiments! Remembering back, years ago when driving in bright sunlight after a rainfall, I used to tilt my head back and forth and marvel at how the sheen of light reflecting off the wet pavement would change. Didn't correlate to polarized light, just thought the effect was 'interesting' |
#13
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
On Saturday, November 10, 2012 3:36:58 AM UTC-5, William Sommerwerck wrote:
I am talking about something that actually unpolarizes polarized light. Does such a thing exist? Yes. A non-metallic reflective surface. Hmmmmm. There are people here who know alot more about physics than I, but I do remember something about that. Most metals conduct and most conductors reflect light. I guess that means they are usually opaque ? However any smooth surface can reflect. Totally black plastic can be polished to a mirror finish and though it will reflect alot of light, you can still tell. So is it that something that does not conduct electricity will do this ? J |
#14
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
"William Sommerwerck" writes:
I am talking about something that actually unpolarizes polarized light. Does such a thing exist? Yes. A non-metallic reflective surface. Nope. -- sam | Sci.Electronics.Repair FAQ: http://www.repairfaq.org/ Repair | Main Table of Contents: http://www.repairfaq.org/REPAIR/ +Lasers | Sam's Laser FAQ: http://www.repairfaq.org/sam/lasersam.htm | Mirror Sites: http://www.repairfaq.org/REPAIR/F_mirror.html Important: Anything sent to the email address in the message header above is ignored unless my full name AND either lasers or electronics is included in the subject line. Or, you can contact me via the Feedback Form in the FAQs. |
#15
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
I am talking about something that actually unpolarizes
polarized light. Does such a thing exist? Yes. A non-metallic reflective surface. Nope. Then why was it that projecting 3D slides at home required a metallized screen? |
#16
Posted to sci.electronics.repair
|
|||
|
|||
Light Unpolarizer
|
Reply |
Thread Tools | Search this Thread |
Display Modes | |
|
|
Similar Threads | ||||
Thread | Forum | |||
Cooper Lighting Motion Sensor Outdoor Light, Turning Light On | Home Repair | |||
Cooper Lighting Motion Sensor Outdoor Light, Turning Light On | Home Repair | |||
wireless eetra light light switch + so,e persomal stuff y don'trea;;y want to knoww! | UK diy | |||
selling led lighting such as led christmas light,led decorative light,led house lamp | UK diy | |||
Propane Stove: Pilot Light Won't Stay Light Testing Thermopile | Home Repair |