View Full Version : Television Without Scanning?


Rinehart
03-01-2012, 09:21 PM
This article was written about 1937 or 38 by U. I. Sanabria. To me it sounds like gibberish--can anyone make head or tail of it?

Electronic M
03-02-2012, 12:15 AM
Sounds like a plausible system for a steampunk story, but it just don't seem all that practical in the real world.....It does show imagination on the part of the author though.

PS: you need to increase the resolution of those scans they were exceedingly difficult to read.

Jeffhs
03-02-2012, 01:07 AM
That's pretty much how flat-screen TVs work, isn't it? No scanning lines, just pixels, so there's nothing to scan. I don't think flat TVs have sync problems, either, as there doesn't seem to be anything to go out of sync if there are no scan lines. Or are there actually such things as sync problems with flat panels? :scratch2: If it is possible for a flat screen to lose synchronization (e. g. if the signal is too weak), there is no way to adjust the sync frequencies as there was with CRT TVs. Considering digital TV's all-or-nothing nature, however, I would think the picture wouldn't even show on the screen if there were a sync problem caused by a weak signal -- let alone synchronize properly.

Electronic M
03-02-2012, 01:47 AM
I believe that FPs convert analog signals (when a digital input is not used) to a digital image then process it in the same way as a digital input....So if the synch detector of the analog to digital converter was lousy it might be possible for a flat panel to "loose synch".
Also on digital signals if the signal drops out temporarily and the screen gets pixelated/ moving scenery get distorted that is sort of like loosing synch. To help compress digital video signals parts of the image that remain unchanged for multiple frames are only sent once, and only the parts that move or change are sent thereafter. So if the signal is disrupted momentarily part of the motion/change data will be missing or wrong and cause the parts of the image that are changing from frame to frame to be out of synch (and or distorted) with the station. Because sometimes the change/motion data can be based on the previous frames motion/change data being received correctly the errors from the missing data can exacerbate them selves over several frames until the next COMPLETE frame is transmitted.

I think the pixels of a flat panel would disqualify it from being a direct incarnation of that system because, though FPs don't really have to use scanning, they are still splitting an image into pieces for transmission and reassembling them for reception/display.

Jeffhs
03-02-2012, 02:42 AM
Thanks much for that explanation, Tom. I guess I have an awful lot to learn about digital TV, having grown up with NTSC analog CRT sets.

Your statement, however, that DTV pictures are separated into several pieces, transmitted, and then reassembled at the receiving end rang a bell in my head -- I probably read it somewhere online, in an article on DTV theory. I do know that DTV receivers rely heavily on computer technology, so that explanation makes sense. DTVs are about the only kinds of televisions that display a "Please Wait . . . " message for the first few seconds after they are first turned on (as my Insignia 19" FP does); that is probably to allow the set's microprocessor and other circuits to initialize before the picture appears.

BTW, I don't know if other brands of flat TVs do this, but my Insignia set will sometimes turn itself off and back on again within a second or so when I shut it off with my GE (Jasco Products) universal remote control. The set does not do this with its own remote. I checked Insignia's website, specifically the user community forum where owners post problems they are having with their sets. One of those posts did mention the turn-off problem when using universal remotes; the problem is caused by the remote actually sending two identical signals to the TV, to ensure that the set is turned off. However, since the remote IR (infrared) signal that turns the TV on is identical to the one that turns it off, the TV is actually getting two turn-on signals -- which is why it will switch on again after having been shut off with a universal controller. The solution is to point the remote away from the television as soon as the power button is pushed. This prevents the TV's remote sensor from receiving two power-off signals, and the set will power off and stay off.

This is a known problem with Insignia TVs, according to the website. I don't know why these sets only do this with universal remotes and not with the original; maybe slight differences in IR signals between universals and the set's own controller? :scratch2:

I would use my set's original remote 100 percent of the time if it were a universal remote, but it isn't. That is, it will operate the television, but not a VCR, DVD, cable box, etc. unless these devices are what are referred to in the TV's online manual as "HDMI-CEC" compatible. For this to work I'd need to connect my VCR and DVD to my FP TV via two HDMI cables, and the VCR and DVD would have to be HDMI-CEC compatible, which I am sure my VCR isn't -- it's far too old (manufactured by Panasonic in 2002). I'm not sure my DVD player meets the HDMI-CEC standard either; it may not, since it was made in 2005 by a Chinese electronics manufacturer (Changhong), which I had never heard of until I bought the unit to replace my CyberHome DVD three years later.

Rinehart
03-02-2012, 01:53 PM
My apologies for the poor quality of the scans. I got them from a television history web site, and although they are clear enough here, I guess they lost some resolution when I sent them as attachments.
Although the tone of the article--"If we extend this [Clarence Darrow's] reasoning, we might then say that in a new science the majority of the engineers are doing the wrong thing"--suggests that it was written by a crank, Sanabria himself wasn't one. I think he opened the first school devoted specifically to training television technicians, which is why I was unwilling to dismiss it out of hand.

Electronic M
03-02-2012, 04:47 PM
I think it was written more to open the eyes of engineers at the time and inspire them to think outside the box than as a "your wasting your time with scanning TV I have what will replace it all built and ready to conquer the market" sort of thing.

earlyfilm
03-03-2012, 02:41 PM
Rinehart, could you provide a link to the original Ulises A. Sanabria article on Television without Scanning? I'd like to reread the article.

I read about this system in the 1950's while I was in grade school. (At the time, our rural library had more books from the pre-WW II era than current ones.)

I remember thinking that this guy was either shyster or complete fruitcake! It just ain't possible.

Now, however, I agree with

I think it was written more to open the eyes of engineers at the time and inspire them to think outside the box than as a "your wasting your time with scanning TV . . . . . " sort of thing.

that this was a thinking exercise.

I now realize that Sanabria was a visionary like C. Francis Jenkins, Philo T. Farnsworth, John Logie Baird and Peter C. Goldmark, all of whom had first, great and practical ideas for their time, but were quickly forgotten when technology side-stepped them.

James.

Rinehart
03-03-2012, 06:20 PM
I got the article from Steve McVoy's web site:www.earlytelevision.org/optical_tv.html It states that it is a reprint from an article in the July 1938 issue of Radio Craft, and it is linked to an unattributed article on the subject in the July 1947 issue of the same magazine.

old_tv_nut
03-05-2012, 11:14 AM
Fun, but:

I'm afraid there's a missing piece of optics in the proposal. If you went out with binoculars to look towards the tower, all you would get is a view of the projector lens, the same as sitting in a movie theater and looking back at the projector. A system like this needs a condenser or relay lens, or a diffusing screen, at the point where the "virtual screen" would be. The concept might be rescued if the image was actually projected on a screen close to the tower, and then the viewer was provided with a zoom-lens light-amplifying telescope to view the projected image.

This does not mention the problem of the high level of bias light due to daylight washing out the image (even if infrared). Perhaps it would only be used after sunset?

old_tv_nut
03-05-2012, 11:33 AM
Slight revision - he says the image is "projected" "using no screen *or objective lens*"

If there's no objective lens, there is no projection - then, what is visbile to the world is the film inside the projector. So... the local telescope essentially has to zoom in on the film itself. If the local telescope optics had sufficiently low flare, daylight might not be a problem - it would essentially be looking down the throat of the "projector" at the film. In this case I see problems with aiming the home unit, plus distortions due to thermal currents.