Making Digital Camera Microscope Adapters Richard J Kinch, PhD Last updated: November, 2013. Richard Kinch cutting a microscope adapter on a metalworking lathe This page describes the custom adapters I make to fit a variety of cameras, microscopes, and medical instruments. I engineer and fabricate these adapters personally using my own CAD facility, optical engineering laboratory, machine shop, and electronics workbench. For most of these simpler mechanical adapters, I charge $175 to $375 (USD), depending on the complexity. Adapters incorporating optical elements are more complex and typically cost $500 to $950, including the optical elements. Complete kits for medical and scientific instruments, with custom mechanical, optical, and electronic components, range from $800 to $6000. Old and new optical instruments are thereby fitted into the modern age of digital imaging. I also research and develop new instrumentation designs for larger projects which involve much higher costs. Besides the mechanical attachment, these adapters apply one of several optical principles to couple the camera to the microscope, including: Afocal (through the normal eyepiece to inexpensive small-format digital cameras) Focal (from a photoport to lensless digital SLR cameras) Focal (from a photoport to small-format digital cameras via a relay lens) Afocal (through a custom photo-eyepiece for large-lensed digital cameras) As an example, you can inspect a 3D solid model for a typical adapter [Autodesk DWF file, 26 KB]. (This requires the free Autodesk DWF Viewer). The viewer allows you to rotate (orbit), pan and zoom the 3D model so you can see exactly what we are discussing. You can also view the mechanical drawing [PDF file, 30KB]. Here is another 3D model that shows a typical adapter and eyepiece nesting [Autodesk DWF file, 28 KB]. Rotate the model (using the orbit tool in the viewer) so you can see how the custom adapter closely fits the supplied microscope eyepiece. And here is one more 3D model that shows the camera, adapter and eyepiece arrangement. [Autodesk DWF file, 58 KB]. The metalworking process may be illustrated by the first such adapter I made was some years back. This was for a Sony DSC-S30 digital camera, mounting to a Bausch and Lomb microscope. This creates a system for high-quality, wide-field photomicrography. The lens of the Sony DSC-S30 camera provides a 37 mm inside diameter x 0.75 mm inside threads, and the microscope eyepiece provides a smooth 1.138 inch outer diameter cylinder. Thus the adapter will consist of a turret with outside threads to mate to the camera lens, and an inside bore to slip snugly over the microscope eyepiece. The first dimensional step is to turn down the cylinder, leaving a raised ridge of 37 mm diameter, ready to take on the outside threads. I chose to thread a length of 5 mm, which was about twice the length of the inside threads on the camera turret. Using the threading bit to turn the smooth diameter makes it easy to leave 60 degree bevels on all the stepped edges. I was happy to find that the 0.75 mm metric thread pitch is available on the minilathe using the standard set of change gears (see the Yahoo 7x10minilathe group files area for tables of using change gears for metric threading). The photos show the work progressing on an aluminum billet I made as a casting experiment, and the casting flaws show up as dark spots or flecks. For later versions, I have been using aerospace grade aluminum stock. Next I mounted the tailpiece onto the lathe with a drill chuck and 1/2-inch drill bit, and bored a hole into the center of the piece. With that 0.500 inch starter hole drilled, I was ready to start boring out the 1.138 inch inside diameter that would receive the microscope eyepiece. For this I used carbide boring bar bits that reached the 1 depth of the finished part. (Making the boring bar tool holder is the subject of another of my project descriptions.) After boring the hole a few thousandths oversize, I had a close fit of the adapter to the eyepiece. I finished the part by cutting it from the cylinder using a parting tool. I cut a length that maximized the fitted depth, but still let the camera lens come to rest on the eyepiece. The photo shows the finished adapter. Below is a view of the Sony DSC-S30 camera, with and without the adapter mounted. This is an old Bausch and Lomb inspection microscope. This US-manufactured item isnt made any more, but when new they sold for about $2000. The optics are superb, providing a wide, flat field at a variety of zoom magnifications from 7x to 30x. Today, you can find them used on eBay for perhaps $500 or less, or you can buy a similar imported item for about that price new. The turrets of the binocular eyepieces have the virtue of being smooth, even aluminum cylinders. This allows a simple cylindrical adapter to nest on top of the eyepiece. This is the camera mounted on the microscope eyepiece. The adapter aligns and rigidly fixes the camera to the microscope. The camera lens protrudes in such a way as to touch the eyepiece, so I should apply a bit of vinyl tape as a cushion, or perhaps machine a spacer ring to insert as a standoff. I may add winged setscrews in the future to lock the camera on the eyepiece. This shows the camera turned on, with the camera display imaging the the microscopes magnified view of a coin. The optical system of this camera is well-matched to the exit pupil of this microscope. By adjusting the camera zoom one can either get a vignetted photo of the full field of the microscope, or a full-framed photo of the center region of the microscope view. Both modes are desirable for various purposes. The photo below shows the full-frame mode. This is a portion, at full resolution, of a photo taken by the Sony camera in the above setup. The object shown is a Lincoln penny, of which you are seeing part of Lincolns face. I measured the features shown with calipers, giving a true height of the representation as 0.070 in. The digital image is 526 pixels high. Thus the system resolves about 7500 pixels/inch, which is 7.5 pixels/thousandth-inch, 130 microinches/pixel, or 3.4 microns/pixel. If we assume your display renders 96 pixels/inch, then the effective magnification is about 78x (= 526 pixels / 96 pixels/in / 0.070 in). The camera resolves 1472 x 1104 pixels (not much by todays standards), so the camera and microscope can photograph a physical area of about 0.2 by 0.15 true inches at this level of detail; the full field to the eye view in the microscope is about a 0.25 inch diameter circle. The microscope field zooms from about 1 inch at 7x magnification, to 1/4 inch at 30x. This is an amazing quality of result given that this camera sells for under $200, and the microscope sells used for about $500. Such a system would have cost many $1000s, and required costly film processing, not many years ago. I dont know the resolution limits of the microscope optics, but theyre probably better than what the Sony DSC-S30 camera is resolving in this setup. If that is true, then a higher-resolution camera would resolve more detail. I have a much better digital camera now, but it uses a large-aperture lens that isnt as well-matched to the microscope aperture, resulting in a severe vignette in the image. As a general optical design principle, one would want a small camera lens for this kind of behind-the-eyepiece microscopy. With camera lenses, bigger is usually better, since you can gather more light. But digital cameras can (and typically do) have very small, but nevertheless high-quality, lens systems, because the CCD electronic imaging devices are so much smaller than film formats. The light available is determined by the microscope optics, not the camera. Many digital cameras today (2004) seem to be using imaging chips and lenses that are very close to the human eye in physical scale. This is a wonderful thing for those wanting to adapt the cameras to microscopes, because no optical adapters (such as a negative relay lens) are needed, just mechanical arrangements. The pupil of the human eye may be assume to be about 4 to 5 mm in diameter when viewing microscope images. A good microscope will provide an exit pupil of similar diameter, and the camera lens should match this as well. Not so wonderful for the would-be photomicrographer is the trend away from putting filter mount threads on the lens turrets, even on the more expensive consumer models; later versions of my Sony DSC-S30 have a telescoping lens contraption that regrettably features no thread mount. If youre looking to buy a digital camera with hopes of photomicrography, look for one with a fixed, threaded turret, with the inside thread diameter significantly larger than the microscope eyepiece you hope to use. Even if your camera has an extending/retracting lens turret, you may find an optional adapter tube (see Nikon, Canon, and Olympus examples below) that provides both room for the turret and filter threads for a further adapter. As a last resort, one can fit a sleeve machined just larger than the turret, with one or more screws for clamping to the turret itself. The original microscopy experiments above were done in 2002. In 2004, I repeated them with the same microscope, but using a higher-resolution camera (Sony DSC-F707, 2560 x 1920 resolution = 5 megapixels) and an Edmund Scientific Co. resolution test target (gratings from 5 lines/mm to 200 lines/mm). This apparatus proved a resolution of 160 lines/mm (4000 lines/inch), or equivalently to 8000 pixels/inch (3 microns/pixel). The photograph shows a contrast enhancement of the 160 lines/mm grating. This is about the same resolution achieved directly viewing into the microscope eyepiece with the naked eye, and is the essential resolution limit imposed by the inspection microscope. Thus a higher-resolution camera does not necessarily translate into higher resolution photomicroscopy images, because the microscope itself introduces the resolution-limiting optical elements. This is a proper approach to the task, where the camera should be chosen to capture an image of some specified area, consistent with the resolution limits and field size of the microscope. The advantage of a better camera is chiefly the larger field size it can capture at the resolution limits. To the left is a thumbnail of another Lincoln penny image taken with the higher-resolution camera at something less than the maximum magnification. See the full 1600x1600 resolution image here [155 KB JPG file], which makes a 20X image on a typical 96 dpi monitor. We can see a field of up to 0.9 inches diameter at this resolution (2000 pixels/inch), with the whole item imaged at once instead of just the nose. Using combinations of the camera and microscope zoom lenses, the magnification can be increased by another factor of about four to 80X or so, but vignetting will start to reduce the size of the object area. The Sony DSC-S85 camera with the Sony VAD-S70 adapter (45mm to 52mm lens adapter) provides a 52mm filter thread. Here are some more digital camera microscope adapters I made for a customer. These slide over a slightly smaller 1.135 eyepiece on a Bausch and Lomb microscope. The smaller item on the left provides an M41x0.5 thread for an Olympus C-3020 digital camera. The larger item on the right provides an M62x0.75 thread for an Olympus E-10 or E-20 digital camera. I used commercial 6061 aluminum round stock for these. The threads on the left look uneven because of an interference pattern (moire effect) on the digital photo. Note the optical illusion which makes the bore look larger on the left adapter compared to the right; they are in fact equal. The photos below show the attachment of the M41x0.5 adapter (above on left) to an Olympus C-3020 digital camera, and to the microscope eyepiece. This adapter I made for a customer with a Nikon Coolpix 5700 digital camera (reviewed here and here) and a Nikon Labophot microscope. That Nikon camera is unusual because although it is a rather advanced model, the zoom depends on the lens turret extending various distances in and out of the camera body, like many snapshot cameras. While the lens hood provides a threaded ring, because of the turret extension, you cannot mount a filter or adapter directly to those threads; instead you must use a Nikon UR-E8 adapter (shown in the photos), which is essentially a 34mm long step-down tube from male M53.5-0.75 (mates to lens hood) to female M50x0.75 (for further accessories). This tube has an ID=51mm and OD=55.75mm, with a stop ridge of 47mm ID at 5.5mm inside of the female threads. This is the black item in the photos. The aluminum microscope adapter I made mated to the M50x0.75 thread on the UR-E8 adapter and received a 23mm (OD) Nikon Labophot microscope eyepiece via a slip fit, overall length of 1 inch. After taking these specimen photos, I enlarged the 23mm bore to 29.2mm to slip over the external diameter of the Labophot eyepiece. Another unusual feature of this adapter is that it can be screwed inside the UR-E8 adapter, or reversibly outside, depending on the camera lens turret extension. This allows the microscope eyepiece a 1.75-inch vertex range relative to the camera, to accommodate various zoom settings while minimizing vignetting. The photos to the left show the reversible mounting. I made a similar large adapter, with Nylon thumbscrew, to adapt a Nikon D70 digital camera with a 70-300mm zoom lens and 62mm lens thread (M62x0.75), to a Celestron 4060 microscope eyepiece with a 1.100 outside diameter. This step-down ring adapter (shown in the center of the photo) I made for a customer who already had a Canon LA-DC52C step-up adapter (left of photo) for a Canon A60, A70, A75, or A85 digital camera (similar to the LA-DC52D for the A80 or A95, or the LA-DC52B for the A30 and A40), which provides an M52x0.75 thread, which was to be mounted to a C-mount (1-32 thread) adapter (right of photo) on the microscope. This Canon adapter, like the Nikon one above, provides an offset tube, inside which the lens turret of the camera has room to extend and retract. Both the inside and outside edges of the ring are threaded, although the photo resolution doesnt resolve all the threads. This adapter is different than the others in that instead of an unthreaded sliding fit to a cylindrical microscope eyepiece, the adapter provides a female thread to connect to C-mount threads on the microscope. It is essentially a 1/4 thick aluminum washer with threads on the inside and outside edges. A similar approach would work for the Canon LA-DC58D conversion lens adapter, which provides a 58mm filter thread for the Canon Powershot G6 camera. Likewise for the LA-DC58 for the Powershot G1 and G2, and the LA-DC58B for the Powershot G3 and G5. This adapter I made for a customers Olympus C-4000 camera, which provides a 43mm filter thread mount. The smooth inside bore slips closely over the eyepiece (1.162 outside diameter) of a Bausch and Lomb inspection microscope. The height in the photo shows my standard 1-inch overall length for these adapters. I have also begun including a rubber O-ring with each of the slip-type adapters. For example, for this adapter with a 1.162 inside diameter, a standard inch-series #213 Buna-N O-ring (ID=15/16, OD=1-3/16, section=1/8) fits snugly into the inside diameter without distorting. This provides a cushion against which one can rest the front of the lens turret to achieve a near-minimal vertex distance to the eyepiece optics. To increase the vertex distance, one can insert more of the same O-rings in a stack. This adapter also required an additional modification (not shown in the photo above or visible in the assembly photo below) to accommodate the turret lens of the camera projecting 0.050 beyond the end of the Olympus CLA-1 41mm-43mm adapter/extension tube for this camera. Since the step ending the 43mm female threads inside the Olympus tube was 0.115 deep, a total length of at least 0.165 (0.2 in practice) had to be relieved inside the threaded end of the adapter, with an inside diameter of 1.575 (40mm) to allow passage of the 1.45 dia extending lens turret. This photo shows the completed assembly, consisting of the Olympus C-4000 camera, Olympus CLA-1 adapter, and custom microscope adapter. Most camera filter threads have a tiny 0.75mm spacing (pitch). This close-up photo shows a threaded section of the C-4000 adapter above. Threads cut properly on a lathe wiil have a smooth finish and correct profile. Good-quality threads attach easily to the camera lens, and ensure a secure attachment. I usually design the threaded length to span about 1/4, which is about 8 to 10 fully threaded turns, like you see here. Full engagement to the camera lens typically requires only 2 or 3 careful turns. Should the initial threads of an adapter ever be damaged, such as by dropping it or accidentally cross-threading it into the lens, I can repair it on the lathe by simply facing off a bit of the threaded end, exposing new, undamaged threads at the adapter face. This custom adapter connects the 37mm filter thread on the customers camera to an American Optical (AO) inspection microscope 10X eyepiece having a 1.180 outside diameter. This adapter is a bit thin, but still strong enough for the mounting task. In cases where the camera threads happen to be smaller in diameter than the outside of the eyepiece, the adapter uses a shoulder to step up the body diameter and maintain strength. This photo shows how the eyepiece joins precisely to the adapter with a slip fit. This provides an accurate axial alignment, which minimizes aberrations and distortions in the photo images. By having the customer send the actual eyepiece, a very close fit is guaranteed on the first try. These slip fits are designed to be close enough for a telescoping fit between the eyepiece and the adapter, allowing an adjustable range of vertex distance. The adapter can be fixed on the eyepiece by assembling with a bit of tissue paper or other thin shim for a tight fit. Or, a bit of white glue or cyanoacrylate (CA) glue (super glue) into the gap creates a semi-permanent attachment; since CA glue does not bond strongly to the oxidized aluminum surfaces of the adapter and eyepiece, the bond is more of a wedge casting than a true glued bond, and the pieces can be later separated and the glue cleaned off if needed. We can also add an optional 1/4-20 threaded hole and Nylon thumbscrew to the adapter as a clamp. This custom adapter mounts a Nikon 4500 digital camera with 28mm threads to an Olympus SZ-CTV microscope adapter. The Olympus adapter provides a cylindrical slip fit with a thumbscrew. This custom adapter mounts a Nikon Coolpix 950 digital camera with 28mm threads to a Leica microscope eyepiece with 1.126 outside diameter. This is an unusual adapter in that the eyepiece diameter exceeds the camera threads, requiring a stepped shoulder on the adapter. This custom adapter mounts an Olympus C-750 digital camera (via the 55mm Olympus CLA-4 adapter tube) to a cylindrical microscope eyepiece. These custom adapters are threaded bushings, with C-mount (1-32) threads on the outside, and 1/4-20 (UNC coarse) threads on the inside. Lengths are 10mm and 14mm. The cost of a small item like this by weight roughly equates to gold. Precision instrumentation is not cheap. Here the same two adapters are reworked to 1/2-20 (UNF fine) inside threads, with a third adapter of 16mm length. This custom adapter mounts a 37mm camera thread (M37x0.75) to a 1.310 outside diameter cylindrical Bausch & Lomb inspection microscope eyepiece. Note the use of a fitted O-ring as a cushion for the front of the camera lens, which minimizes the reflex distance and vignetting. We provide the correct O-ring(s) as needed with the adapter. This custom adapter mounts a 30mm camera thread (M30x0.75) to a 1.152 outside diameter cylindrical Bausch & Lomb inspection microscope eyepiece. This mounts a Sony DCR-TRV11 or DCR-TVR27 video camera to the scope. This custom adapter mounts a 37mm camera thread (M37x0.75) to a 1.221 (31mm) outside diameter cylindrical Nikon CoolPix MDC lens (a relay lens for a Leica MZ16 and other microscopes, also called an MDC-A or MDC-relay, presumably just an acronym for microscope digital camera [adapter]). The close-fitting smooth inside bore of the adapter provides a telescoping mechanism which with the single nylon clamping screw (1/4-20 x 1 inch) provides an adjustable vertex distance between camera and microscope. Male threads (M28x0.75-3mm) at the end of the MDC lens are not used; a fixed step-up ring (28mm to 37mm), a standard item from photographic suppliers, is an alternative for a fixed-vertex-distance adaptation. The custom adapter (on the right in the photo) is a threaded-flanged bushing which adapts the 28mm (M28x0.75) female thread of the Nikon UR-E6 adapter (on the left in the photo, for a Nikon Coolpix 5000 digital camera) to a female C-mount thread (1-32) for attachment to a microscope lens. The flange allows one or two O-rings to be inserted to adjust the vertex distance. This bushing weighed only 3.6 grams, and the inside and outside threads cleared each other by a thickness of less than 1mm. The finished item was priced at about 3 times the cost of gold by weight. This custom adapter mounts a Canon EOS Digital Rebel 300D digital SLR with 18-55 EFS lens (58mm camera thread, M58x0.75) to a 1.154 (29.3mm) outside diamter microscope eyepiece, namely a Leica Mark X Gemolite Stereo Zoom with 15X W.F. eyepieces. The three nylon screws (1/4-20 x 1-inch) allow for vertex distance adjustment. Topcon SL-5D and SL-6E Slit Lamp This custom adapter retrofits Canon and Nikon digital SLRs to the camera port of an ophthalmological instrument, a Topcon slit lamp (Topcon SL-5D slit lamp and Topcon SL-6E slit lamp). The camera port in the original design accepted an obsolete Topcon 35mm film camera back. This photo shows the original bayonet ring mount for the original film camera. This drawing shows the new adaptation for the Topcon SL-5D and SL-6E slit lamps, consisting of a custom adapter which replaces certain components in the original bayonet mount, and a stock T-mount adapter for the Canon or Nikon digital SLR. The custom adapter provides a male T-mount thread (M42x0.75), on which a commercial adapter (T-mount to EOS) is then attached for the camera. The design works with the original Topcon locking ring to secure the adapter into the instrument. Adapting in two pieces via an intermediate T-mount thread has several benefits: it avoids having to machine the more difficult EOS bayonet lens fitting, it allows rotation of the camera on the instrument, it provides an adjustable vertex distance; and it is compatible with many other T-mount items. The T-mount-to-EOS ring can be purchased inexpensively off-the-shelf, as well as for a wide variety of other camera lens standards. See the detailed mechanical drawing [2.7 MB PDF file] for complete details and specifications. A photo showing the upgraded camera coupler mounted in a Topcon SL-5E slit lamp, ready to receive the digital camera. The camera coupler locks into the Topcon instrument using the original locking ring and handle seen just below the camera bayonet mount. A photo showing the Canon 400D (Rebel XTi) digital SLR being mounted on the Topcon SL-5E slit lamp, using the adapter. Close coupling of the new camera to the instrument maintains parfocality with the eyepiece view, while not interfering with the observers chin. The digital camera can be quickly removed and a conventional lens attached for use in ordinary photography. Besides the Canon 400D (Rebel XTi), the Canon 300D (Digital Rebel), 350D (Digital Rebel XT), 1000D (Digital Rebel XS), and 450D (Digital Rebel XSi) models are also suitable for this application.
Posted on: Tue, 28 Jan 2014 10:57:15 +0000
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