Talk:Video camera tube

Orthicon & tube sizes

One item that has not been discussed is the relative size of the various camera tubes. This is not much of an issue for studio cameras, but can be of considerable concern for portable cameras.

Typical Image Orthicons are rather long (approximately 18 inches), while Vidicons are typically only a few inches long. Additionally, Image Orthicons are typically many inches in diameter (3-4.5 inches), while Vidicons may be less than an inch in diameter. The result is that cameras using Image Orthicons are typically rather huge boxes, while cameras using Vidicons may be held in the palm of a hand.

Another issue that has not been addressed is the ruggedness of the various tubes. Image Orthicons can be quite fragile. The target plate in an Image Orthicon is made from glass and is quite thin, which results in it being rather fragile. The target must be of an insulating material, and thin enough that electric charges deposited on the front of the tube by the photoemitted electrons can migrate through the thin layer to the back of the target, where they will be scanned by the electron beam. One of the cautionary notes about the operation of Image Orthicon tubes states that they should never be pointed with the face below about a 30 degree angle. This is to prevent any debris, which may be present at the back of the tube as a result of the manufacturing process, from sliding forward along the neck of the tube and impacting the target, since such an impact, even by a tiny bit of debris, is likely to shatter the target.

Another cautionary note involves the operating temperature of Image Orthicons. The photoemissive layer at the front of the tube is somewhat volatile. Thus, the tube should never be subjected to operation in temperatures at which the photoemissive material could evaporate, since it would likely be deposited on the target, which would ruin the charge storage mechanism that the target operates on. A similar effect can be produced by excessive illumination. Thus, an Image Orthicon should never be aimed, even momentarily, such that its view images the sun or a bright light, since the energy focused on the photoemissive surface may be intense enough to cause evaporation of the photoemissive material.

A counter-effect is that the characteristics of the photoemissive material are somewhat temperature sensitive, which means that Image Orthicons may lose some sensitivity in cold temperatures. Thus, some camera equipment which used Image Orthicons would provide a heater to warm the front of the tube in cold weather.

---

Dave

Iconoscope's sensitivity

• The iconoscope section needs some work. Larger "lux" values indicate less sensitivity. "75,000 lux" is a terrible sensitivity. Tropical noon sunlight is around 100,000 lux.

That number can't be right. It's all over the web, but it has to be wrong. The source of this misinformation seems to be http://www.akh.se/tubes/camera.htm . Iconoscopes were insensitive, but not that insensitive, at least in their later forms.

• It should be mentioned that the image orthicon combines the advantages of the image dissector and the iconoscope. The orthicon was the first tube that had decent sensitivity.

--Nagle 18:50, 11 March 2006 (UTC)

• In re this question, it seems possible that what is meant is that a light source of about 75klx intensity is required for a decent image. Having taken photographs of stage-lit events I can confirm that the light intensity is usually comparable with cloudy daylight, and stronger lighting is certainly possible. It does seem unlikely that what is meant is that the tube could only register--as a minimum--signals of 75klx.

• It is also possible that the article refers to the first tubes only.

• The datasheet for the RCA 5820 Image Orthicon, states "Commercially acceptable pictures can be obtained at incident light levels greater than about 10 foot-candles". So unless I am wrong, that means: 10fc = 107.64 lux is pretty near the 200lx as described generally in [1]. While the RCA 1848 iconoscope says "Good operation can be obtained with a highlight illumination level on the mosaic in the order of 7 foot-candles", so roughly 75lx, NOT 75Klx (perhaps there was a typo or a conversion error). However, this appreciations are subjective, because that would mean that the iconoscope was more sensitive than the IO, which is completely impossible. My best guess is that simply what was considered good in 1940 was not in 1950s. According to Terman in Radio Engineering, IO should be between 100 and 1000 times more sensitive than the iconoscope. Alchaemist (talk) 04:34, 13 March 2009 (UTC)

Alchaemist -- do not confuse SCENE illumination, the light falling on the subject and TARGET illumination, the light collected by the lenses and delivered to the tube's target.

I am looking at the original paper data sheet from the published and readily available RCA HB-3 Handbook, for the 5820 Image Orthicon dated Sept 15 1949, Its states "...illumination on photocathode for maximum signal Output: 0.01 ft-c" You can find a sheet from Philips for their 5820 at http://tubedata.milbert.com/sheets/030/5/5820.pdf stating similar values.

The data sheet, same source, for the RCA 1850-A Iconoscope states that the required illumination on the target should be between 4 and 20 ft-c.

The Iconoscope is about a thousand times less sensitive than an Image Orthicon. To convert foot-candle to lux multiply by 10.8 OldZeb (talk) 05:39, 15 March 2009 (UTC)

Excellent! Thanks for noticing it, what I looked didn't specify so. The PDF I have for 1848 iconoscope, didn't have any values, neither a curve. I'll correct these values in the article with the ones you mention. Regards! Alchaemist (talk) 03:35, 16 March 2009 (UTC)

Orthicon or Image Orthicon

My recollections of camera tube types are that there is a difference between the "Orthicon" and the "Image Orthicon" tubes. The Image Orthicon was developed out of the Orthicon tube which was invented by Arthur Rose in 1937/38. The Orthicon had no what we used to call "Image Amplifier" located in the larger section at the front of the Image Orthicon tube. So, for the article to be correct, the heading “Orthicon” should really be changed to “Image Orthicon”, the words "or simply orthicon tube" removed and another heading and description for its ancestor the “Orthicon”. I’m having a problem locating technical information about the Orthicon (sans Image) tube but I found a diagram and a bit more information at: http://members.chello.nl/~h.dijkstra19/page4.html and an IEEE reference at: http://www.ieee.org/organizations/history_center/legacies/rose.html. In Australia we were using Image Orthicon cameras at least into the 1970's. Fernseh brought out the only solid state Image orthicon camera I know of in about 1968. We referred to the tubes as "IO's". Peter Resch 06:39, 28 April 2006 (UTC)

Elaboration on above comment and 'emmy' correction

The nickname 'emmy' came from another tube from the same family, the Emitron (or CPS Emitron). (for more, see http://www.burle.com/cgi-bin/byteserver.pl/pdf/pctdhbook.pdf which is based from original source material, see its footnotes) The Image Orthicon, or IO, and the emitron, or CPS Emitron, both used a mosaic type photoemitter.

Regarding the comment above, I believe he's talking about the earlier Multiplier Orthicon. The MO tube had an electron multiplier in it that amplified the signal prior to sending it to the video amp so as to produce a stronger but still relatively clean input signal. But the IO tube also had a multiplier built in for the same purpose, but also had a two-sided target. And both were sent to a video amplifier. The multipliers were to boost the weak source signal. On principle I agree with the notion of making the heading just 'Orthicon', but generally when people talk about orthicon tubes, they're talking about IO tubes as they were the more advanced and in more widespread use.

140.247.121.204 (talk) 15:18, 20 March 2008 (UTC)

A not so tiny detail

I'd like to see this article explain how it's possible to have a beam going from electron gun to target and then have a return beam. If high voltage is what accelerates the beam one way then I'm confused how a beam can then go the other way. That's the sort of thing that's glossed over and I'd be very curious about. Steve / filmteknik

Steve,

The electrons will land on the target only as long as the target potential is higher than the cathode potential. All remaining electrons are either reflected or scattered depending on their arrival energy and return towards the cathode. Most will be captured, however, by the aperture electrode, which is beloe cathode potential. It is at this point that electron multiplier structures can be inserted to read out the return beam as is done in image orthicons (read the reflected beam) and isocons (read the scattered beam.

Dave Gilblom

Vladimir Zworykin vs Philo Farnsworth

This article gives primary credit to Vladimir Zworykin and minimizes the contribution of Philo Farnsworth in the invention of the television camera. Farnsworth is responsible for the key idea of using a 2 dimensional matrix of photosensitive material to create the electronic signal. Zworykin, backed with the resources of RCA, improved on Farnsworth's ideas and created the iconoscope. Although Zworykin/RCA attempted to claim the entire invention, the US patent office found in favor of Farnsworth and RCA was required to pay royalties to Farnsworth for his patents. Farnsworth version of the story can be found here http://www.farnovision.com/chronicles/tfc-who_invented_what.html http://www.farnovision.com/chronicles/tfc-intro.html Zworykin/RCA version of the story can be found here http://www.acmi.net.au/AIC/ZWORYKIN_BIO.html

Kharkless

I am sorry to say this but the idea of using a 2 dimensional matrix of photosensitive material goes back to Alan Archibald Campbell Swinton who presented this idea in the paper Distant Electric Vision printed in the journal Nature 78, 151 (18 June 1908), several years before Farnsworth. You can find a copy of this paper in the web page:

http://www.nature.com/nature/journal/v78/n2016/pdf/078151a0.pdf.

Even in Farnsworth's wikipedia file it is textually said: [In 1930, after a visit to Farnsworth's laboratory, Vladimir Zworykin copied this apparatus for RCA, though he found it impractical and returned to his work on the iconoscope. The U.S. Patent Office rendered a decision in 1935 that the "electrical image" of Farnsworth's image dissector was not in Zworykin's inventions, and priority of that invention was awarded to Farnsworth].

RCA indeed paid in 1939 one million dollars for Farnsworth's patent on the "Electrical Image" concept because they needed the patent rights to produce their Image Orthicons (built by Rose, Law, and Weimer in 1944-1945). The image part (photocatode and target) in the Image-Orthicon is indeed a Farnsworth's Image-Dissector, but Zworykin's Iconoscope does not use any "Electric Image" as the U.S. Patent Office dictaminated. Zworykin used Tihanyi's ideas, but not Farnsworth's ones. —Preceding unsigned comment added by 189.216.171.103 (talk) 05:08, 10 March 2009 (UTC)

Plumbicon Tubes

In the TV series Monty Python's Flying Circus, they used EMI 2001's with Plumbicons. In one episode, Episode 17, a model of a building exploded and caused the camera to show a glowing red and green halo and then it faded away. Was this a malfunction? Curvebill 18:48, 9 September 2007 (UTC) by abhinav —Preceding unsigned comment added by 59.93.70.119 (talk) 16:51, 19 October 2008 (UTC)

Image Orthicon copy-edit

• I rewrote the subsection Operation of the Image Orthicon to be more precise and accurate. I based myself in Radio Engineering by Frederick Terman from 1947. I would like to cite it as a source, however it applies to the whole subsection, rather than a part of it, so I don't know where to put it. Finally, I don't think the copy-edit note should stay for the Image Orthicon section, what do you think? Should we remove it? Regards! Alchaemist (talk) 03:57, 13 March 2009 (UTC)

Two Historical Notes

One of the first all-electronic video camera tubes was invented in France by Edvard-Gustav Schoultz in 1921. He filed the French patent FR-539-613 on August 23, 1921. The patent was accepted on April 5, 1922, and published on June 28, 1922. You can find a copy of the original document in the web page [[2]]

The Image Dissector was also invented in Germany by Max Diekmann and Rudolf Hell in 1925. They filed the German patent DE-450-187 on April 5, 1925. The patent was accepted on September 15, 1927, and published on October 3, 1927. You can find a copy of the original document in the web page [[3]]

--134.153.204.160 (talk) 15:47, 24 July 2009 (UTC)

Image Dissector

Starting around 27 July, an anon editor has been rewriting the image dissector section, and the image dissector article, too, to give credit for that device to others besides Farnsworth. I have no problem crediting the others for what they did, but it was my impression that "image dissector" was a specific reference to Farnsworth's device. Is there evidence that the inventions of the others are referred to by the same term? Or shouldn't they have their own section(s)? I introduced an "Early steps" section to separate those from the Farnsworth tube. Dicklyon (talk) 06:39, 31 July 2009 (UTC)

Note that Dieckmann and Hell did indeed call their primitive (and unworkable) electronic imaging device "Image Dissector". The title of their 1925 patent application, "Lichtelektrische Bildzerlegerröhre", literally translates to "Photoelectric Image Dissector Tube".

licht = photo; elektrisch = electric; bild = image; zerlegen = dissect; röhre = tube.

Source: Follett Vest-Pocket Dictionary: German, (German-English / English-German), Follett, 1970.

Cheers, Rico402 (talk) 15:24, 31 July 2009 (UTC)

Right, I had already verified that translation, though my translation sources suggested "break" and "burst" rather than "dissect"; I just wanted to know if "dissector" was sourced in this context, as I always thought that was a uniquely Farnsworth term; turns out it is sourcable for the Dieckmanna/Hell device, too, so I added a bit about that. I think this section still suffers from too much editor interpretation of primary sources, which is really unnecessary, since there is a huge secondary literature, easy to find, on this topic. Dicklyon (talk) 16:32, 31 July 2009 (UTC)

Gentlemen. Best wishes from the Anonymous Author (I prefer the long and original Latin term, please). The proper translation to English of the term "Lichtelektrische Bildzerlegerröehre für Fernseher" is: Photoelectric tube that takes images apart for television. There are different grades of breaking or cutting up things in German.

Zerbrechen means: beak to pieces; like crashing a vase against a wall.

Zergliedern means: dismember or dissect; like with an insect.

Zerkleinern means: reduce to small pieces; like grinding Parmesan cheese.

Zerlegen means: take apart, cut up, take to pieces; like dismantling a watch.

Okay... So what's the point of defining Zerbrechen, Zergliedern and Zerkleinern? Showing off? Kindred words share a common root; how unusual. Rico402 (talk) 08:27, 1 August 2009 (UTC)

On the other hand please find attached below some transcriptions taken from three books and two articles on the history of television talking about the works of Dr. Max Dieckmann, Dipl.-Ing. Rudolf Hell, and Inventor Philo Farnsworth. I hope you may take the best decision of your own after having this piece of information.

1) R.W. Burns, Television: an international history of the formative years [[4]], The Institution of Electrical Engineers, Science Museum (Great Britain), page 358 and 360.

---Unknown to Farnsworth when he filed his patent, two German workers, Dr M Dieckmann and Dipl Ing Hell had patented a similar camera tube on 5 April 1925. The patent was made public on 15 September 1927, about eight months after Farnsworth's application, and so the two patents were independent of each other. The principal difference between the operation of the camera tubes concerned the method of scanning: Farnsworth used electric fields, Dieckmann and Hell employed magnetic fields. Generally, camera and display tubes have a simpler internal electrode configuration when magnetic deflection is utilised since the coils are necessarily external to the tube. The photoemissive cathode surfaces of both tubes consisted of a coating of potassium, or rubidium, or sodium. Hell claimed in 1951 that he made a tube but could not get it to function because of the inadecuate knowledge (in 1925) of electron optics.

The same utterly irrelevant crap: "Unknown to Farnsworth"; "could not get it to function". So the significance is what? That someone filed a patent for a fundamentally unworkable device?

From Early Television: A Bibliographic Guide to 1940, George Shiers and May Shiers, ed. New York: Garland, 1996, p. 80.:

"An indication of the upsurge in the interest in television is seen in the number of patents listed: thirty-seven for 1925, thirty-one for 1926, more than four-fold the annual rate of disclosures for the previous six years." (Emphasis added.)

My goodness, we gotta get all these in the article right away! One can never have enough useless information (in an article about video camera tubes that actually work). Rico402 (talk) 08:27, 1 August 2009 (UTC)

By the way electron optics is indeed the art of using electrostatic or magnetic fields in order to deflect or focus electron beams. Imagine for example the electron optics used in the electron microscope. Furthermore Farnsworth used electrostatic field deflection for scanning the electron image only in his first device[[5]], all and everyone of his subsequent devices used magnetic field deflection[[6]] [[7]] [[8]] [[9]].

Yes, and tying your shoes is "the art of manipulating the ends of the laces into a secure but easily-released knot, most commonly in the form of a bow". I don't think we need a primer on electrostatics and electromagnetics from "google patents". Rico402 (talk) 08:27, 1 August 2009 (UTC)

2) Albert Abramson, The history of television, 1880 to 1941[[10]], page 97.

---The camera tube (which was later to be called an Image Dissector) was essentially the same as that of Max Dieckmann and Rudolff Hell. However, their patent had not yet been issued and, as often happens in the field of invention, was almost identical. Still, where Dieckmann failed to get his tube to operate, Farnsworth was to success...

Rubbish, regardless of what Abramson says: "essentially the same"; "almost identical". How curious that they could never get it to work. Have you seen the schematic of this silly thing? Rico402 (talk) 08:27, 1 August 2009 (UTC)

3) Albert Abramson, Zworykin, pioneer of television[[11]], page 54.

---In April 1925, Dr. Max Dieckmann and Rudolf Hell applied for a German patent on a unique camera tube which electrically converted the entire optical picture into an "electron image" instead of using a single electron beam to scan the target. It was a cold-cathode tube that used high voltage to free the electrons from the photoelectric plate. The electrical image thus produce would be moved sequentially by means of coils or plates across a single anode in an aperture. The current from this anode would be led to an amplifier and become the picture signal. This form of scanning of the image inspired the name "image dissector". While Dieckmann and Hell claimed to have built several tubes of this type, they had to admit later that they could never get any of them to work.

Precisely my point: they could never get any of them to work. Rico402 (talk) 08:27, 1 August 2009 (UTC)

4) J.D. MacGee, The Contribution of A. A. Campbell Swinton, F.R.S., to Television, Notes Rec. R. Soc. Lond., 1977, 32[[12]], pp. 97.

---It is certainly true that without charge storage as now used in almost all television camera tubes it would be impossible to transmit television pictures except at unacceptably high levels of illumination. The image dissector tube, due to Dieckmann and Hell and later developed by Farnsworth, is the only alternative and it is inherently about four orders of magnitude less efficient.

"[D]ue to Dieckmann and Hell"?! The development of a working tube had little if anything to do with Dieckmann and Hell's little unsuccessful experiment. MacGee just doesn't know what he's talking about. Rico402 (talk) 08:27, 1 August 2009 (UTC)

5) Malcolm Gladwell, The Televisionary, The Newyorker. [[13]]

--But this was Farnsworth's mistake, because television wasn't at all like the safety razor. It didn't belong to one person. May and Smith stumbled across photoconductivity, and inspired LeBlanc, who, in turn, inspired Swinton, and Swinton's idea inspired inventors around the world. Then there was Zworykin, of course, and his mentor Boris Rosing, and the team of Max Dieckmann and Rudolf Hell, in Germany, who tried to patent something in the mid-twenties that was virtually identical to the image dissector.

This "virtually identical" crap really gets around. (I.e., where do suppose Gladwell got phrase?) And who doesn't rely on The Newyorker for the most accurate and comprehensive account of developments in science and technology? :) Rico402 (talk) 08:27, 1 August 2009 (UTC)

Please Gentlemen feel free to compare the transcriptions above against the original material, and so to decide by your own.

Best wishes: Non vox, non votum, sed actum.

And you can drop the faux polite routine. Rico402 (talk) 08:27, 1 August 2009 (UTC)

Postdate: By the way Dicklyon, it is strange you sat that I give credit for that device to others besides Farnsworth, but you never said that I was also who explained when Farnswoth introduce the magnetic focusing and the electron multiplier in the image dissector. Strange should I say.

Oh please... Strange I should say, that you've never learned how to sign you posts or open an account.

Logica falsa tuam philosophiam totam suffodiant. Thus I'm not persuaded by your arguments to credit Dieckmann and Hell with anything other than possibly coming up with a clever name for the device that every serious researcher in the field knew was needed for the realization of a fully electronic television system. Cheers, Rico402 (talk) 08:27, 1 August 2009 (UTC)

Magnetic Focusing

It is quite arrogant to say that the Farsnworth "Television system" included a much more advanced device for "the conversion and dissecting of light". Who says that?, advanced with respect to what?, where is the reference?

Let me point out George Everson book The story of television: the life of Philo T. Farnsworth[[14]] where it is textually said in page 91 that: We again went into the receiving room. Things were turned on again. The bluish field lighted up. Cliff put the slide in again. A fuzzy, blurry, but wholly recognizable image of the black triangle instantly filled the center of the picture field. This was our first television picture!

The real breakout come with the magnetic focusing, and Farnsworth knew that. Let me point out the following references.

1) The same George Everson book as two paragraphs above, in page 24 he says that: In thinking the matter through, Farnsworth concluded that unless he prevented it the electron image would unquestionably become blurred. His knowledge of optics told him that light beams could be focused; therefore, why could he not provide a magnetic lens, or solenoid, to control the electrons and keep the unseen electron image sharply focused? This magnetic fo-cusing was the second essential in the development of his tele-vision camera.

2) The same George Everson book again, in page 81 he says that: In his original conception of the magnetic lens Phil thought that as the current increased the focus would become sharper, but early experiments showed this was not the case. The focus sharpened to a certain strength, but then if more current was applied the image again became blurred.

This magnetic lens was another original contribution to electronics. It provided Farnsworth with an important patent in television scanning[[15]].

The design and placement of the magnetic coils around the dissector tube became an essential factor in the production of a clear, undistorted image.

3) R.W. Burns, Television: an international history of the formative years, in pages 360--361 says that: In April 1928 Farnsworth applied for a patent for an improved image dissector. The new device incorporated a long solenoid, in which the tube was placed, so as to establish a uniform logitudinal magnetic field along the axis of the image dissector. It is easy to show that an appropriate magnetic field enables the electronic image formed in the plane of the cathode to be focused in the plane of the aperture. Although the magnetic field configuration does not constitute an electron lens--- since it can neither focus a parallel beam of electrons nor produce a magnified or diminished image of an extended source of electrons---it does lead to a sharper images.[[16]]

Best wishes: Non vox, non votum, sed actum.

--148.247.186.142 (talk) 22:15, 31 July 2009 (UTC)

References - Campbell-Swinton and Television

1) Letter to Nature suggesting the use of a modified CRT for transmitting moving images.

---A.A. Campbell Swinton, Distant Electric Vision, Nature 78, 151 (18 June 1908)[[17]]

2) Presidential address to the Röntgen Society where the first all-electronic transmitting CRT is described with certain detail and a diagram[[18]].

---A.A. Campbell Swinton, Presidential Address, J. Roentgen Soc. 8 (Jan. 1912), pp. 1--15.

---A.A. Campbell Swinton, Fernsehen, Z. Schwach 6 (1912), pp. 149--153

... The image screen is a mosaic of insulated cubes of rubidium faced by a metal gauze screen with a space between filled with conductive gas, such as sodium vapor. The scanning beam charges the photoelectric elements negatively; those that are brightly illuminated release charges through the ionized gas to the gauze screen, or signal plate.

... certain ideas that have occurred to my imagination in the hope that they may lead others to the invention of a more practicable method of arriving at what is wanted.

3) Updated version of the original 1911 scheme.

---A.A. Campbell Swinton, The possibilities of television with wire and wireless, Wireless World, 14 (Apr. 9 1924), pp. 51--56; (Apr. 16, 1924), pp. 82--84; (Apr. 23, 1924), pp. 114--118.

---Television, Mr. Campbell Swinton's system, Engineer, 137 (Apr. 12, 1924), pp. 384--385.

---Mr. Swinton's views, Popular Wireless, (Apr. 12, 1924), p. 245.

4) Research article describing Campbell Swinton's experiments on television.

---A.A. Campbell Swinton, Electric Television, Nature 118, 590 (23 October 1926)[[19]]

...I actually tried some "not very successful" experiments in the matter of getting an electrical effect from the combined action of light and cathode rays incident upon a selenium-coated surface.... The transmitting apparatus consisted of a home-made Braun oscillograph in which a metal plate coated with selenium was substituted for the usual fluorescent screen, the image to be transmitted being thrown by a lens upon the selenium surface, and the end of the cathode ray beam being caused electromagnetically to traverse the projected image. Experiments were also tried in receiving with a Braun tube which I purchase in Germany, but in its then "hard" form it proved very intractable.

--148.247.186.142 (talk) 00:15, 1 August 2009 (UTC)

Mr. Anon, thanks for all your info. Why don't you make yourself an account and help us get the article improved? My objections before were based on my inability to verify some of your assertions, and what I thought was improper structuring of the contributions of others inside the section on the image dissector, which I had thought was a specific reference to the Farnsworth device. Now that I know there are sources that apply that term to the Dieckmann and Hell device, I've gone ahead and cited those sources. What's important in getting your contributions to stick in Wikipedia is simply good sourcing, to clearly indicate whose information or interpretation is being summarized. Your own interpretations of primary sources (e.g. patents) will not usually survive in a topic like that one, where there is a deep secondary literature that should be relied on.

I'm also willing to ask for a removal of the semi-protect if you say that you're willing to cooperate but don't want to make an account for some reason. Dicklyon (talk) 04:41, 1 August 2009 (UTC)

Dicklyon, you're being too forgiving. This is the same unregistered user who altered the text to read:

"The first practical all-electronic camera tube was the Image Dissector filed for patent by Dieckmann and Hell in 1925 (patent issued in 1927) and filed again for patent and demostrated (sic) by Philo Farnsworth in 1927 (patent issued in 1930)." (Emphasis added.)

He's arguing that Dieckmann and Hell produced the fist "practical" design, and that Farnsworth just coincidentally duplicated their work. It's an utter falsehood, considering that Dieckmann and Hell's design bears little resemblance to Farnsworth's, they could never get it to work, and they didn't even have an approach to understanding how to make it work. What's the point of being the "first" to patent a gadget if one doesn't know what he's doing and his gadget doesn't work and his research goes nowhere.

This is just another in a long series of attempts to undermine Farnsworth's contributions to the field with specious claims of priority.

Btw, the "semi-protect" stays until 07:41, 6 August 2009 (UTC). Cheers, Rico402 (talk) 09:58, 1 August 2009 (UTC)

Rico and anon, I presume you guys have a history that's making you act this way toward each other; let's try to break out of it. Rico, don't fall for his bait. There's no need to discuss his interpretation of original patents and other primary sources. Let's just focus on the right stuff, namely summarizes what other historians have already concluded and published, then we can avoid having to argue over all that other stuff. Dicklyon (talk) 17:21, 1 August 2009 (UTC)

On the other hand the image dissector designed, invented, or whatever by whoever is the first stage in and a main part of the image orthicon and the image isocon, which were later replaced by the vidicon and similar tubes around 1950 or 1960. But the magnetic focusing for video camera tubes invented by Farnsworth in 1928 --via a long focusing coil placed along the tube-- survived the image orthicon era and it was a main ingredient in the vidicon and similar tubes; see the vidicon's diagram in the article. Thus Farnsworth's magnetic focusing was extensively used from the famous press conference in 1928 until 1990 or so. I suppose that Farnsworth did not earn royalties for the whole 70 years, but the fact is that Farnsworth was the first one in patenting a video camera tube with magnetic focusing.

--189.216.206.234 (talk) 18:05, 1 August 2009 (UTC)