_______________________________________________________________________

Microscope illumination and photomicrography

Whole page rechecked 18th August 2007

The trouble about photomicrography work is that it grows progressively until there is a great pile of completed material. The simplest answer is to throw out the earlier work. With readers coming in who need the earlier work either as background, or somewhere cheap to start, this is a bad idea, so all work from inception has been kept. This also keeps me honest, since I cannot change course, and pretend the new direction is how it always was. A dry-as-dust summary of work so far follows. If you can face reading it, you should be able to follow the links to an area that interests you.

Summary

Early work

It was very plain, around June 2000, that digital photosensors were going to enter a period of rapid improvement in both quality and price. Current microscope bright-field illuminators used the classic tungsten/halogen lamp followed by a condenser stage. This arrangement swamped the system in infra-red, which overloaded digital photosensors. Additionally, unless the condenser stage was a costly achromatic one, colour aberration was introduced into the object on the slide, even before the microscope objective got to work on it.

By December 2000 I was using a high-intensity white LED in an optically-optimised housing that replaced the substage condenser, and eliminated the need for separate illumination. I did not know Carl Zeiss had actually introduced a similar product, a few months earlier. Since that time the housings on the ledlyt, as I call my device, have been further developed, but the optics remain as first completed.

The ledlyt gave me very even white achromatic illumination for bright-field, and there was no infra-red at all. The characteristics ideally suit both digital photosensors, and normal eyepiece work. With a tailored housing, the ledlydt can replace most microscope substage condensers, and is on sale.

With the light source taken care of, I began photomicrography on algae, in the water samples coming in regularly to Microcosm Consulting. In early 2001, all that was economically available was a Kodak webcam with a 480 x 680 pixel chip. I re-engineered the webcam and removed the lens. Photographic results were surprisingly good, but plainly limited by the size and resolution of the chip.

Background to the ledlyt, and webcam photomicrography. A whole section on the earliest ledlyt design, and webcam photography using it.

.

Camera development

As time passed, digital cameras became cheap enough to mechanically modify. I switched to a circuit board from a 1.3 megapixel camera, mounted inside a big technical case with the lens removed. Optical quality of the results improved, despite much colour correction being required. At least half of the current Algae Indentification Index photos have been taken by this camera.

The following links update the ledlyt to current, look at digital photomicrography in general, and give a full account of the 1.3 megapixel system.

Introduction to the ledlyt, and digital photomicrography

Microscope optics - check (and criticise) if you are an expert

Microscope objectives - specifications versus Finance

Digital camera basics - what Sony won't tell you

Photomicrography options - a few of the ways to fit a camera to a microscope

Developing the digital film - not as simple as it might appear

Technical Digital camera TDC 1b - full details and photos

The ledlyt - full details and photos

Fine quality - a very few photos at original quality

.

Digital photomicrography with a conventional digital camera

I took a detour investigating if a normal Casio 4 megapixel digital camera with a non-removable zoom could be used for photomicrography by adding subsidiary lenses. Many such systems are for sale. A clear conclusion at the end of the work was that image degradation was unavoidable. The microscope objective must form an image direct on the digital photosensor.

On the Algal Identification Index CDR, the Casio investigation is recorded, and pictured, in full detail, and it is a big chunk of work. I cannot even abbreviate it enough to make it downloadable. The basic flaw in the system, apart from the additional height required by the second lens system, is the performance at high power. The 40X objective acts as a point source. Any optical defect in the second lens system, and in the zoom, creates visible shadows on the final picture, and the end result is an uneven mess. With the second lens perfect, and perfectly clean, the Casio zoom, like most new-age lenses, has at least one aspheric component, and this is precision moulded, not ground. Other critical photomicrographers describe machining marks on the original lens mould being visible, and according to my photography the circular 'trails' produced on the picture are not tolerable. The moment a lensless camera is used, all these secondary features vanish.

.

CMOS chip camera techniques

I settled on a 2.11 megapixel camera from Ricoh. The chip was CMOS, not CCD, so there was no problem removing the lens, and the sensor dimensions were optimal for direct-image photomicrography. The all-metal camera body was easy to rebuild, rather than starting afresh. Results were good with a conventional mount on the top of the microscope tube.

I broke new ground by reviving old 'mechanical isolation' techniques to break the link between the camera and the microscope. The result used with a 40X objective has no vibration or mechanical feedback problems. I do not even need a cable release. Until sensor improvement outdates this camera, there is no need for further work.

Photomicrography with an isolated table - shortened version (some pictures) of the full CDR report

.

Ongoing work

Photo quality is now showing up shortcomings in the modest objectives that have been used for some time. I am buying in via eBay top quality 160mm objectives, and the detail and sharpness have once more improved. I am now free to concentrate on building the Algal Identification Index.

.

Our address is:-

7 Sykes Court, Pakenham, Vic 3810, Australia

Phone/fax is local 03 5941 4789 overseas +613 5941 4789. Please try to phone or fax while Eastern Australia (Melbourne and Sydney) is awake!.

The e-mail address remains of course the same - breck@permaflate.com