The Craftmans Shop > New from Old
An Encounter with a Surgical Operating Microscope.
nrml:
That is an interesting little microscope. Very compact and quite unusual in that it seems to have only one set of eyepieces. Most of them tend to have two sets of eyepieces so that an assistant or trainee can help with the operation or view the procedure. Most modern ones have an inbuilt camera in addition to the two sets of eyepieces which gets fed to an external monitor.
Pete W.:
--- Quote from: nrml on August 13, 2018, 07:47:45 PM ---That is an interesting little microscope. Very compact and quite unusual in that it seems to have only one set of eyepieces. Most of them tend to have two sets of eyepieces so that an assistant or trainee can help with the operation or view the procedure. Most modern ones have an inbuilt camera in addition to the two sets of eyepieces which gets fed to an external monitor.
--- End quote ---
In my opening post, I suggested typing 'Zeiss Op-Mi6' into Google and going to the photos offered there. Among those photos there are many showing other variants of the Op-Mi6 including lots with multiple sets of eyepieces.
On the one I have here there is a dummy beam-splitter sandwiched between the eyepieces and the main body of the microscope head. This one is just there to maintain the correct optical path length (aka 'tube length') but it could have been replaced by a functional beam-splitter and one or two additional sets of eyepieces. I used the past tense because Zeiss ceased to support the Op-Mi6 a long time ago!!
My first job was with EMI Ltd. One of their departments developed a colour television system. It didn't win the competition for the broadcast market so they had a go at the surgical training sector. It was reported of the inaugural trial that when the surgeon made his initial incision both the camera operator and the guy at the vision mixer panel in the OB van outside fainted and were caught by porters stationed by the surgeon for just that purpose!! (They might not have been porters.)
Pete W.:
I'm going to digress a bit but it's all in support of the theme of the thread!
I'm a gadget junkie. When my main hobby was SCUBA diving, I had much more equipment than matched the few hours per year I spent underwater. Similarly, when my main hobby was amateur radio, I had much more equipment than was justified by the time I spent on the air.
Having some awareness of my addiction to gadgets, I've spent my life deliberately avoiding 'taking up' photography - I knew once the camera bug bit me I'd be bankrupt overnight!! I did buy a digital camera (stills) when I set up my eBay account but I'm not 'into' DSLRs and, until now, definitely not 'into' video.
Despite that, I did buy a cheap digital camcorder a couple of years ago to record an outdoor social event and achieved results that were good enough. The camcorder is totally unbranded, no maker's name or model number. It will take either still photos or video and records onto an SD card. It just says 16 MegaPixels.
Now, how does all that relate to the surgical microscope? Well, although I've recorded some of the project with still photos, the aim of the project is to restore the operation of the focus and zoom motions in response to the rockers on the Pedal Unit. Can't show that very well in still photos! So, I thought that when I've developed this thread account a bit more, it would be appropriate to show those motions in a video to illustrate the fruit of the project.
So I set up the camera and a light source before the microscope stand and had a couple of attempts to show the focus and zoom motions in operation. Both takes were very fuzzy and out of focus. I was filming from a couple of feet distance. For the first take, I had the camera set with the 'focus' switch set to the mountains icon and for the second take I set it to the tulip icon. It didn't seem to make much difference to the sharpness of the video image.
If I unscrew the decorative aluminium ring around the lens, there is a male thread of 30 mm diameter. Does that correspond to a standard thread for attachment of filters and/or close-up lenses? Should I be looking for a close-up lens?
Pete W.:
Since my last post, I've got a different camcorder. Hopefully, I'll be able to capture the video 'footage' I referred to. But there's a lot to tell before that!
I explored the circuitry of the Pedal Unit but it wasn't making sense without the Control & Power Supply Unit so I turned my attention back to that. The first photo shows the innards of the Control & Power Supply Unit as received. The second photo shows most of the schematic of that unit. The parts omitted are the connections between the various power supply lines and the 12-way connector to the Pedal Unit and the connections between that connector and the 5-way connector to the Microscope Head. They will be shown on sheet 2 of the schematic (to follow later). Some of the circuitry on sheet 1 is a bit speculative - the reason is that the components are so closely packed into the box that visual access is impossible!
I have used Fast Stone Resizer on the schematic but I chose a bigger size than our usual value - if it's too big when I see it uploaded, I'll change it.
Most of the C & PSU circuitry is straightforward. Zeiss have chosen to fuse both legs of the mains supply input. I wouldn't have designed it that way but this post is showing what I received. All the metal parts of the C & PSU are bonded to each other and to mains earth and both the 12-way and the 5-way sockets provide a contact to bond to the metal parts of the Pedal Unit and the Microscope Head, pillar etc.
The two transformer secondaries each feed a bridge rectifier arranged to provide a symmetrical ± DC output. Secondary 'A' includes a tap selector switch to select one of two available output voltages. The switch concerned here is the one whose dolly is labelled 'Focus I II'. Secondary 'B' does not have this facility. The 'B' ± output rails each have a mystery component in series. These each measure 0·1Ω, they might be self-healing fuses of varistors. I was surprised to find that neither set of output lines is connected to ground.
The numbers in circles refer to the transformer secondary tag panel. References to 'Tag #8 & #9' and similar refer to the tag-strip that runs parallel to the edge of the box. I arbitrarily allocated numbers to the tags starting with #1 at the left-hand end (with the green/yellow wire). The two 'mystery components' can be seen mounted on the tag strip on the opposite side of the box.
My schematic drawing complies with no known standard but I hope you will be able to understand it. I grew up when resistors were shown as zig-zag lines and transformer windings were loopy but I agree that those styles take skill and time to depict well.
Pete W.:
The parts of the circuit of the Control & Power Supply Unit shown in sheet 1 of the schematic (see previous post) were fairly easy to trace, partly by visual examination and partly using my Fluke multimeter. The parts of the circuit comprising the interconnections between the various connectors were more difficult, since much of the wiring was in the depths of the housing, inaccessible to both Fluke test probes and Mk1 eyeball. In fact, the space was so densely packed that there was no access even for my dental mirror. Consequently, some of the connections shown on Sheet 2 of the schematic are inferred and there may even be connections that are not shown at all. The fact that I was able eventually to achieve both focus and zoom operation of the microscope head depends on the 'P/FZ' switch remaining in the 'P' position and the focus and zoom connectors remaining unused. (The particular microscope head in this instrument is wired to connect to the 'P' connector.)
The 'Focus I II' switch is partly beneath the upper tag-strip in the photo included in the previous post - the 'FZ/P' switch is partly beneath the lower tag-strip.
In my next post, I expect to describe my tussle with the Pedal Unit microscope head.
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