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The ledlyt

Ledlyt installations on the Olympus GB40 (ring mount) and the Nikon Alphaphot (fork mount). The photos are at different scales, but notice the centre section of both brass housings is the same diameter, only varying in length. Inside the housings the optical core is identical, but located higher up in the Nikon. The Nikon external ledlyt housing is polyacetal, to save weight.

The ledlyt is a replacement for the normal light/Abbe condenser system used in a microscope. A high-brightness white LED and a specialised diffuser system is mounted in a 'dummy' condenser of the same dimensions as the Abbe unit it replaces. The light is brilliant white, outstandingly even, and dims progressively through some very useful shades of grey, as opposed to the usual red-brown. Lowering the ledlyt from its top position right under the slide varies the illumination from completely flat to increasing amounts of shadowing, similar to stopping-down a conventional system, without side-effects. For photography, the ledlyt maintains a constant colour temperature regardless of light setting, and emits no Infra-Red at all. The only real criticism of the ledlyt, when shown to informed users, is that compared with the normal condenser system, it is too easy, and all the skill of driving the normal set-up goes out of the window.

The ledlyt went on the market in December 2000, and I assumed it was unique. About a year ago I discovered Zeiss had probably beaten me to first by a few months, and had a device available, of dummy condenser/diffuser construction, which looked uncannily familiar.

The first question to answer is whether there is any difference between the two. I have only closely-examined the Zeiss unit on the Net, and in the manufacturer's literature, but the Zeiss unit is cordless, using a small PP3 9 Volt battery fitted in the housing. The device is sold to fit one model, the Axiostar, which is their general purpose (and excellent) student microscope.

Front and side views of the ledlyt power supply. The battery holder is lidless, so battery changes take seconds (every few years).

Apart from the obvious differences of installation on any model for which we can make a dummy condenser housing, and so far, years of working life from the massive 6V lantern battery in the external power supply, there may be a fundamental difference in optical performance. As ledlyt development was coming to a close, the unit was delivering adequate, but unremarkable illumination. I found a specific combination of device geometry and diffuser opalescence that introduced some of the characteristics of phase illumination to the light source. This gently sharpens the edges of images, particularly on objectives 20X and above, and the photomicrographs on this website display the result. I do not have the Education or Status to say if this effect actually displays more detail, or only looks as if it does, but either way, some prominent local microscopists maintain it is useful. Zeiss may have used other means to secure the same result, but from examining their publicity pictures, it is plain ledlyt optical geometry is not in use. My personal opinion is that the ledlyt provides phase-based optical sharpening, and the Zeiss unit does not.

Phase-based optical sharpening. The light grey background has intensified to white along the sides of this live and waving Oscillatoria. The same mechanism has created a fine black line along the sides, and made internal detail more visible. Winkel 25X and ledlyt.

The phase effect has kept the core optical design of the ledlyt cast in stone. In early models, if the condenser to be replaced was large, the ledlyt weighed more, and added to the load on the lower rack and pinion. We never actually saw one drop under Gravity as a result, but some came close, where the lifting gear had worn slack over time and heavy use. The revamped ledlyt housings are lighter and more compact, and feature side-entry of the power cable. This is in response to the current Olympus student model, which features a prominent non-removable light concentrator below the Abbe condenser, which tends to collide with a vertical cable. Where the original condenser is large, we can now provide an external housing machined in polyacetal, which cuts the weight of the ledlyt down to only a few grams more than the original condenser.

Illuminated ledlyt in top position, just under the slide, when inserted, but not in contact. The back view of the ledlyt shows the Nikon objective centre is nowhere near the condenser centre, and the adjusting screws have been used to pull the ledlyt to one side, so it lines up with the objectives.

The major microscope manufacturers have thankfully standardised their condenser mounts over long periods of time. For instance the Olympus condenser from the GB40 model (about 1975) will still fit their latest student microscope, not only in alignment, but with the top position still just clearing the slide as it should. There is a similar continuity with Zeiss, although in both cases larger mounts have been introduced with modern specialised models. The Zeiss uses a bigger ring mount, and the high-tech Olympus models a side-insertion fork mount similar to the Nikon.

We have not yet seen a conventional microscope that could not take a ledlyt in a housing of the same dimensions as the condenser. This does not include metallurgical models, which require a combination of more light, and a greater illuminated area. Models we have matched already, for example the Olympus ring-mount, we should be able to provide a ledlyt after getting you to make a few basic checks that the condenser mount is not some 'stranger'. If a ring-mount is involved, we can work on a dimensionally equal device, if you, for instance mail us your previous condenser, with care. If you can find a responsible toolmaker, and ask him to measure up your condenser carefully, and send us a dimensioned sketch, that would also fit the bill. Fork-mounts are very tricky devices. The ledlyt has provision for centre alignment built into the mount, but getting a fork-mount unit to match precisely without testing it on the original microscope for fit, centre and vertical movement, not to mention slide clearance, is exacting and exasperating. The ledlyt is meant to fit all comers. Talk to us.

Price

This will vary according to the condenser the ledlyt has to mimic, but all-up, including power supply, cost should be between 350 and 400 Australian dollars.