Olympus microscopes and photomicrographic equipment

Attaching a C-mount video camera to an Olympus BH-2 microscope with an MTV-3 or U-PMTVC adapter

Introduction

C-mount video camera on an Olympus BH-2 microscope

Olympus produced the MTV-3 and other equipment for connecting video cameras with a C-mount to trinocular versions of their BH-2 compound microscopes, including the BHS, BHT and BHTU biological models, the BHSP and BHTP polarising models and the BHM, BHMJ, BHMJL and BHSM metallurgical models. You can also connect a video camera to other Olympus microscopes

Starting from the top, you need the following items:

Video camera body
C-mount adapter
Photo eyepiece
Trinocular head

The BH-2 microscope was discontinued around 1993, and so most of the items referred to on this page (including the MTV-3, the NFK photo eyepieces and the BH2-TR30 trinocular head) are also discontinued. The best places to find them are eBay and microscope dealers who sell used equipment.

Video camera bodies

You do not need a lens on the video camera, because the C-mount adapter relays the image from the photo eyepiece directly onto the sensor, and so only video cameras that accept C-mount interchangeable lenses are suitable.

Many sorts of video camera can be used, both digital and analogue, ranging from surveillance cameras to very expensive and specialised cameras designed for photomicrography.

The Olympus MTV-3 and U-PMTVC adapters are designed for use with video cameras with either a 1″ sensor (16 mm diagonal) or a 2/3″ sensor (11 mm diagonal), depending on the choice of photo eyepiece; cameras with smaller sensors can be used but will have a restricted field of view.

The video camera body is connected to a C-mount adapter.

C-mount adapters

Olympus produced the cream-coloured MTV-3 C-mount adapter (catalogue number 7-C555) to allow video cameras to be used with trinocular versions of their BH-2 compound microscopes. The detachable top section has a male C-mount for attaching a camera and a 0.3× reducing relay lens that intercepts the image from the photo eyepiece and relays it onto the sensor in the camera. The bottom of the MTV-3 clamps on to the circular dovetail on trinocular heads for BH-2 microscopes.

The MTV-3 produces a circular image approximately 16 mm in diameter, and to take full advantage of this a video camera with a 1″ sensor would be needed. The Nikon 1 J1 and V1 cameras have a CX format sensor with a 15.9 mm diagonal, and so they also appear to be suitable.

Reduction factors in C-mount adapters are normally quoted relative to a 1″ sensor, so a 0.3× adapter would be used with a 1/3″ sensor. However, in the specification of the MTV-3 (and the U-PMTVC), Olympus use 0.3× to refer to the reduction of the image circle of an NFK 2.5× eyepiece from approximately 48 mm (to safely cover 35 mm film) down to 16 mm for a 1″ video sensor.

The black U-PMTVC adapter (catalogue number U-V210, 037151) that is still available for the BX and other current Olympus microscopes can also be used on the BH-2. Like the MTV-3, it includes a 0.3× reducing relay lens. The only significant difference from the MTV-3 is that it provides some adjustment for parfocality between the video camera and the viewing eyepieces.

Focus through the viewing eyepieces.
Loosen both Allen (hex) clamping screws on the U-PMTVC.
Hold the top part stationary, and rotate the lower part until the image on the monitor is in focus.
Re-tighten both clamping screws.

Olympus also produced the uncommon and expensive TVZ-M Zoom Video Lens (catalogue number 7-C567) with a magnification range of 0.55× to 1.1×. This includes a parfocalising collar and is designed to work without a photo eyepiece. The bottom of the TVZ-M clamps on to the circular dovetail on trinocular heads for BH-2 microscopes.

Diagnostic Instruments produce alternative adapters for video cameras with ½″, 2/3″ and 1″ format sensors; they are designed to work without a photo eyepiece.

Photo eyepieces

To project the image produced by the objective onto the 0.3× relay lens in the C-mount adapter, special photo eyepieces that sit inside the circular dovetail on the trinocular head are used, not the viewing eyepieces.

The NFK photo eyepieces were designed for photomicrography with the LB or long barrel objectives that were supplied with the BH-2 microscope, including the DPlan, SPlan, SPlan Apo, MSPlan and Neo SPlan ranges. These objectives have a 45 mm parfocal distance.

For a video camera with a 1″ sensor (16 mm diagonal), with the MTV-3 C-mount adapter, the NFK 2.5× photo eyepiece (catalogue number 2-LC894) provides the best match to the view through the WHK 10×/20 L viewing eyepieces. The NFK 2.5× photo eyepiece is also appropriate for standard 16 mm cine film (12.7 mm frame diagonal) and Super 16 mm cine film (14.5 mm frame diagonal).

For a video camera with a 2/3″ sensor (11 mm diagonal), with the MTV-3 C-mount adapter, the NFK 1.67× photo eyepiece (catalogue number 2-LC898) provides the best match to the view through the WHK 10×/20 L viewing eyepieces. Unfortunately, the NFK 1.67× eyepieces are uncommon and expensive.

Using a video camera with a ½″ sensor (8 mm diagonal), a 1/3″ sensor (6 mm diagonal) or a smaller sensor will result in a restricted field of view. Using a photo eyepiece with a higher magnification will also result in a restricted field of view.

You must use a photo eyepiece with the MTV-3 and U-PMTVC adapters, but the TVZ-M is designed for use without one.

None of the photo eyepieces can cover the field of view through the BH2-SWTR30 superwide trinocular head.

Trinocular heads

Trinocular heads have a pair of inclined tubes for binocular viewing plus a third vertical tube that takes an NFK photo eyepiece.

Three trinocular heads were made for the BH-2 microscope, and they all incorporate the 38 mm circular dovetail for attaching a C-mount adapter. The common trinocular head is the BH2-TR30. The other heads are the superwide BH2-SWTR30 and the tilting BH2-TTR, which are uncommon and very expensive.

BH2-TR30 trinocular head

Olympus BH2-TR30 trinocular head

If the image on the monitor is not in focus at the same time as the image seen through the viewing eyepieces, then some video cameras allow you to adjust the focus. If you use a U-PMTVC adapter, then you can use its parfocality adjustment.

Trinocular heads for the BH microscope can be used on a BH-2, but they need a PM-ADF eyepiece adapter to provide the circular dovetail.

Alternative C-mount adapters

Diagnostic Instruments produce their DD50BHC 0.5× C-mount coupler for video cameras that have a ½″ format sensor, their DD63BHC 0.63× C-mount coupler for video cameras that have a 2/3″ format sensor, and their D10BHC 1.0× C-mount coupler for video cameras that have a 1″ format sensor. These couplers are designed to work without a photo eyepiece. They replace the top section of the BH2-TR30 trinocular head (the part with the circular dovetail), which can be removed by unscrewing 3 screws.

Diagnostic Instruments C-Mount Coupler for BH-2

Attaching a C-mount video camera to other Olympus microscopes

Olympus CH-2 compound and CK2, CK40 and CK40M inverted microscopes

The normal trinocular head for the CH-2 and CK2 microscopes is the BH-TR45-W, which has a plain vertical eyepiece tube. The CH3-TR45 for the CK40 and CK40M is similar. In order to provide the circular dovetail to which the MTV-3 C-mount adapter clamps, you need to add a PM-ADF eyepiece adapter.

If you use the BH2-TR30 trinocular head on a CH-2 or CK2, then you do not need the PM-ADF.

Olympus IMT-2 inverted microscope

The IMT-2 does not need a trinocular head because it has a side port with the circular dovetail to which the MTV-3 C-mount adapter clamps. An NFK photo eyepiece can be pushed into the side port.

Olympus AH3 Vanox compound microscope

The AH3 versions of the Vanox microscope have a port on top of the head that accepts an AH2-ADF adapter (catalogue number 7-C548). This adapter provides the circular dovetail to which the MTV-3 C-mount adapter clamps, and an NFK photo eyepiece fits inside the dovetail.

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Olympus microscopes and photomicrographic equipment

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