Idea: converting a B&W tube camera to colour using a colour CCD for chroma pickup
In the last month I have came up with an idea for a bit of fun which is to convert a B&W tube camera to colour using a CCD for chroma pickup. This involves using a B&W image pickup tube (iconoscope, image orthicon or vidicon) as the luminance channel and a CCD with its luminance stripped (or attenuated) purely for chroma pickup and a prism beam splitter to split the light to the tube and CCD and then the matrixed CCD chroma image and tube luminance image get added together which results in a colour image made of the combine tube luminance and CCD chroma. To make this idea practical I believe both tube image and CCD image have to both be accurately matching each other width/height and linearity so they can be accurately superimposed over each other.
Also another addition to this tube/CCD idea is to make best use of both the old and the new technology by having it set up to be switchable between 3 modes. Firstly it is good to have the original tube B&W image so mode 1 will be B&W tube picture and CCD switched off. Secondly why not make good use of the CCD for normal superior quality colour filming so in mode 2 the tube and it's associated high power electronics will be switched off and the CCD with it's low powered electronics will be switched on only and with full luminance. And the third option which is mode 3 (which is the purpose of this tube/CCD idea) is to have both tube and CCD switched on, luminance removed from CCD leaving only chroma and CCD chroma and tube luminance added together making a tube style colour picture.
Anyways whilst thinking about this idea I have came across the Fernseh/Bosch Museum site and found some excellent diagrams of colour cameras using a mix of image orthicon and vidicon technology on the Fernseh KC-33 colour camera page which had a few tube arrangements for the KC-33 colour camera which mixed image orthicon with vidicon and one of the diagrams containing an IO luminance 3 colour striped vidicon chroma camera arrangement (see diagram here) and that diagram has brought some clarity to my own idea in how the tube/CCD can be arranged. As seen in the diagram there's a beam splitter prism to split the beam to both the image orthicon tube and the colour vidicon tube, also there is another lens, a mirror and a prism block added for the vidicon. Using this arrangement I redrew the diagram in Corel using a colour CCD in place of the vidicon and below I have adapted the tube/CCD layout for an iconoscope tube type, image orthicon tube type and a vidicon tube type, and of course this principle applies to all the other variants of those basic 3 tube types.
Iconoscope/CCD colour layout
It appears from the original IO/vidicon diagram Fernseh are using their YRB method of making colour pictures which the green is derived from the luminance, red and blue channels, I can guess there will probably be issues on the accuracy of deriving green from the mix of tube and CCD seeing we're looking at two totally different image pickup devices whereas the YRB colour method will work well with 3 image pickup devices of the same type, for example in the case of a typical Bosch/Fernseh KCU-40 three plumbicon tubes are used, one for luminance and the other two for red and blue, and the green is derived from the three. Anyways I just copied off the original IO/vidicon diagram anyways as a basic layout for my own idea. Whilst in my diagrams the colour encoding method is YRB, I will most likely not utilize that method when I one day build one of these cameras but instead utilize 4 channels of YRGB like the EMI 2001 four plumbicon tube colour camera.
Now I have actually been putting this CCD/tube colour idea to the test and have experimented with taking a two video snaps of a subject, one with a B&W vidicon camera and one with a CCD colour camera and super imposing the two snaps over each other in Corel Photopaint to make the CCD/tube colour picture. In my experiment I displayed on my computer screen a very colourful photo of a rainbow lorikeet and took two video stills, one using using my 1974 Sony AVC-3250CE B&W vidicon camera and the other using my 1991 Panasonic NV-MS1 Super VHS CCD colour camcorder. I then had to straighten and align the two pictures so they will closely match up with each other when superimposed over one another so I rotated the images till they were straight and resized them and cropped them to closely match and be at a size of 720x576. I then reduced the brightness and contrast of the CCD image dramatically so only mainly the chroma information was there so when adding to the vidicon image the brightness won't overbloom. I then superimposed the darkened CCD image over the luminated vidicon image and blended them using "add" which adds the two images together making a nice luminated vidicon style picture with CCD colour. The images don't quite match exactly but good enough to make a decent image. Anyways below is the pictures illustrating this experiment.
Image Orthicon/CCD colour layout
Vidicon/CCD colour layout
After successfully creating a vidicon/CCD colour image I decided to take this little experiment a step further and see how it would work with an image orthicon style B&W image. Because I don't have a working image orthicon camera I had to create a pseudo image orthicon halo look to my vidicon image of the lorikeet by first adjusting the brightness up a little and the contrast down pretty low and then using the "unsharp mask" effect twice which brings on a pseudo image orthicon look to the image making some of the bright areas of the image halo. The haloing is not quite like that of a real image orthicon tube but looks okayish to simulate an image orthicon look. Anyhow here below is the orthiconized vidicon image and the resultant image after adding that image to the CCD chroma image, the results speak for themselves. I believe the early field sequential colour wheel image orthicon cameras made colour images similar to this but more below the knee of haloing due to the filter wheel reducing the light going to the tube.
Raw vidicon image
Raw CCD image
vidicon image straightened and resized and cropped to 720x576
CCD image straightened and resized and cropped to 720x576
Luminance almost completely removed from CCD image leaving mainly the chroma
The resultant vidicon/CCD colour image after blending the two images using "add" function which looks pretty good! :D
The resultant IO/CCD colour image after blending the two images using "add" function, once again a pretty good resultant image! :D
I would love to put this tube/CCD colour camera conversion idea of mine into practice so if anyone has anything to contribute to this idea to make it really practical or has spotted some flaws to this idea and my envisioned theory to it and wishes to provide corrections send me an email at email@example.com as I am open for any ideas. If anyone who already has the technical knowhow in building cameras wants to put my idea into practice, you're more than welcome and I in fact encourage you to do so as I want to see this idea come to fruition in whatever way possible!!! :D