Modular Viewing Heads for Olympus BH2 Microscopes
The various viewing heads for the BH2 series of microscopes are of the Jentzsch design, and are described below.
The BH2 line of scopes can be used with various viewing heads, as detailed below.
Click here to see a the specifications of the various viewing heads for the Olympus BH2.
BH2-BI30
BH2-BI30 Binocular Head
The BH2-BI30 (Olympus 3-LC405) is a Jentzsch style binocular head with automatic correction of optical tube length for all settings of inter-ocular distance. This version accepts 23mm oculars, has a 30-degree inclination angle, a field number of 21, and has a diopter adjustment on the left eyepiece tube. The right eyepiece tube includes a small notch on the bottom to hold reticle eyepieces in the proper orientation.
The BH2-BI30 was standard on the various BH2 upright scopes, and may also be used on the IMT2 inverted scope.
BH2-BI45
BH2-BI45 Binocular Head
The BH2-BI45 (Olympus 3-LC404) is a Jentzsch style binocular head with automatic correction of optical tube length for all settings of inter-ocular distance. This version accepts 23mm oculars, has a 45-degree inclination angle, a field number of 21, and has a diopter adjustment on the left eyepiece tube. The right eyepiece tube includes a small notch on the bottom to hold reticle eyepieces in the proper orientation.
The BH2-BI45 was standard on the IMT2 inverted scope, and may also be used on any of the BH2 upright scopes.
BH2-SWBI30 Binocular Head
The BH2-SWBI30 is a Jentzsch style binocular head with automatic correction of optical tube length for all settings of inter-ocular distance. This version accepts 30mm oculars, has a 30-degree inclination angle, a field number of 26.5, and has no diopter adjustments on either eyepiece tube (the 30mm eyepieces contain diopter adjustments). The left and right eyepiece tubes include a small notch on the bottom to hold reticle eyepieces in the proper orientation.
The BH2-SWBI30 provides a super-wide visual field when used with SPlan objective lenses. This viewing head may be used on the IMT2 inverted scope or any of the BH2 upright scopes.
BH2-TR30
BH2-TR30 Trinocular Head
The BH2-TR30 (Olympus 3-LC553) is a Jentzsch style trinocular head with automatic correction of optical tube length for all settings of inter-ocular distance. This version accepts 23mm oculars, has a 30-degree inclination angle, a field number of 21, and has a diopter adjustment on the left eyepiece tube. The right eyepiece tube includes a small notch on the bottom to hold reticle eyepieces in the proper orientation.
The BH2-TR30 includes a 3-position diverter shaft on the right–hand side to control the split of light between the binocular eyepieces and the camera port (the light can be split between the eyepieces and the camera port in a 100/0, 80/20, or 0/100 relationship). This viewing head may be used on the IMT2 inverted scope or any of the BH2 upright scopes.
BH2-SWTR30
BH2-SWTR30 Trinocular Head
The BH2-SWTR30 is a Jentzsch style trinocular head with automatic correction of optical tube length for all settings of inter-ocular distance. This version accepts 30mm oculars, has a 30-degree inclination angle, a field number of 26.5, and has no diopter adjustments on either eyepiece tube (the 30mm eyepieces contain diopter adjustments). The left and right eyepiece tubes include a small notch on the bottom to hold reticle eyepieces in the proper orientation.
The BH2-SWTR30 includes a 3-position diverter shaft on the right-hand side, to control the split of light between the binocular eyepieces and the camera port (the light can be split between the eyepieces and the camera port in a 100/0, 80/20, or 0/100 relationship).
The BH2-SWTR30 provides a super-wide visual field when used with SPlan objective lenses. Although the eyepieces provide a super-wide field number, the camera port on the BH2-SWTR30 does not provide additional field coverage. This viewing head may be used on the IMT2 inverted scope or any of the BH2 upright scopes.
BH2-TBI
BH2-TBI Tilting Binocular Head
The BH2-TBI tilting binocular viewing head (Olympus 3-LC406) uses a 23mm Jentzsch style binocular mechanism similar to that used in the BH2-BI30 binocular viewing head. The BH2-TBI has an adjustable inclination angle of 0 to 45 degrees, a diopter adjustment on the left eyepiece tube, and provides a field number of 21. This viewing head may be used on the IMT2 inverted scope or any of the BH2 upright scopes.
BH2-TET
BH2-TET Trinocular Head
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The BH2-TET has a 30-degree inclination angle, a diopter adjustment on the left eyepiece tube, and provides a field number of 21.
BH2-TTR
BH2-TTR Tilting Trinocular Head
The BH2-TTR tilting trinocular viewing head (Olympus 3-LC407) uses a 23mm Jentzsch style binocular mechanism similar to that used in the BH2-BI30 binocular viewing head. The BH2-TTR has an adjustable inclination angle of 0 to 45 degrees, a diopter adjustment on the left eyepiece tube, and provides a field number of 21.
The BH2-TTR includes a 3-position diverter shaft on the right-hand side, to control the split of light between the binocular eyepieces and the camera port (the light can be split between the eyepieces and the camera port in a 100/0, 80/20, or 0/100 relationship).
This viewing head may be used on the IMT2 inverted scope or any of the BH2 upright scopes.
BH2-SMT
BH2-SMT Erect Binocular Head
The BH2-SMT uses a Jentzsch style binocular viewing head similar to that used in the BH20BI30. The BH2-SMT provides optically erected imaging.
BH2-PT
BH2-PT Monocular Tube
The BH2-PT monocular phototube (Olympus 3-LC151) can be used on the IMT2 inverted scope or on any of the upright scopes in the BH2 line, to replace the viewing head and to attach either an eyepiece or a camera (using the PM-ADF eyepiece adapter). The BH2-PT, which features a 23mm ocular tube compatible with the various BH2 eyepieces, contains no optics whatsoever and provides a field number of 21
IMT2-PT
IMT2-PT Photo Tube
The IMT2-PT monocular phototube can be used on the IMT2 inverted scope or on any of the upright scopes in the BH2 line, to replace the viewing head and to attach a camera (using a suitable adapter). The IMT2-PT features the same 38mm NFK dovetail mount as found on the BH2 trinocular heads. The IMT2-PT contains no optics whatsoever, and provides a field number of 21.
AH-MPS-W
AH-MPS-W Right-Angle Projection Screen
The AH-MPS-W is a cream colored projection screen for the BH2, which uses an NFK photo eyepiece and contains an integral 90-degree prism to project an image onto a 155mm viewing screen. The magnification of the projected image is equal to the objective magnification multiplied by three times the NFK magnification. These projection screens are quite rare.
AH-SPS-W
AH-SPS-W Right-Angle High-Resolution Projection Screen
The AH-SPS-W is a cream colored projection screen for the BH2, which uses an NFK photo eyepiece and contains an internal 90-degree prism to project an image onto a 155mm viewing screen. The magnification of the projected image is equal to the objective magnification multiplied by three times the NFK magnification. The AH-SPS-W is similar to the AH-MPS-W, but provides a higher resolution image on the viewing screen. These projection screens are quite rare.
BH2-WP
ABH2-WP Wall Projection Prism
The BH-WP is a 90-degree projection prism for the BH2, which projects an image onto a suitable white wall or screen. These projection prisms are quite rare.
What is a Jentzsch Viewing Head?
The Jentzsch style binocular viewing head was developed by German-born Felix Jentzsch in 1913, while Jentzsch was employed by the Leitz company. The original Jentzsch design had parallel eyepiece tubes and provided for interpupillary-distance adjustment by allowing the eyepiece tubes and their associated prisms to laterally slide further apart or closer together.
The Jentsch design as first produced by Leitz utilized adjustable eyepieces to compensate for the inevitable changes to the optical tube length that occurred as a result of adjustments to the interpupillary distance. Subsequent improvements provided automatic tube-length compensation by coupling the positions of the eyepieces within the eyepiece tubes to the lateral sliding mechanism, such that as the eyepiece tubes were slid further apart, the eyepieces moved deeper into the tubes, and as they were slid together, the eyepieces moved further out, thereby automatically compensating for the tube-length variation.
The primary disadvantage of the Jentzsch design is the necessity to compensate the tube length with changes to the interpupillary-distance setting, which adds both cost and mechanical complexity. Also, since the eyepiece tubes are mechanically linked to the interpupillary distance slides (in automatically compensated Jentzsch designs), a very loose slide mechanism can allow the interpupillary distance setting to move if pressure is inadvertently applied to the eyepieces by the operator.
Advantages to the Jentzsch design are that the height of the eyepieces do not vary, nor do the eyepieces rotate (so measuring reticles within the eyepieces do not rotate within the field of view) with changes in the interpupillary distance setting. Additionally, a loose slide mechanism in a Jentzsch-style head does not allow creep under the influence of gravity, whereas a loose Siedentopf head mechanism can creep.
Before You Buy A Trinocular Head
Be careful when shopping for a trinocular head for your BH2 microscope. You will find that there are many out there that look like the one shown on the left side of the image below, which is missing the top “chimney tube”. Compare this head to the one on the right, which still has the chimney tube (which contains the recess for the NFK photo eyepiece and the 38mm mounting dovetail for the Photomicro L Adapter or the MTV-3 adapter). The chimney tube was removed from the head on the left many years ago, in order o fit the third party C-mount adapter shown in place of the tube.
After installing the third party adapter (Diagnostic Instruments, in this case), the owner no doubt launched the original chimney tube into the air with a quick, deft toss, setting the tube on an arc of destruction towards the nearest trashcan, where it hit its mark with a dull, sickening thud.
Chimney tubes are quite rare on the used market, and are very expensive when they do show up, so be sure the trinocular head you buy still has its original parts. Don’t be tempted to think you can buy a head like the one shown on the left of the image below and simply use the third party C-mount adapter to attach a camera to your BH2. The Diagnostic Instruments C-mount adapter shown in this image is not suitable for the BH2, since its integral reduction lens does not provide compensation for the incomplete intermediate image produced by the Olympus LB objectives, and since its design does not allow an NFK photo eyepiece to be used. The NFK photo eyepiece (or a conventional LB eyepiece) is strictly required if optimal photomicrographic imaging is to be obtained from the BH2. THERE ARE NO EXCEPTIONS!
The third-party vendors selling these things were of course well aware of the optical limitations of their adapters while they were actively marketing them to BH2 owners, but they either didn’t bother to tell their prospective customers of the limitations, or if they did, the BH2 owners who bought them chose to save a few bucks and live with lower-quality imaging on their scopes.
Storing Your Trinocular Head
The best way to store your trinocular head when it’s not being used is to place suitable dust caps into the two ocular tubes, over the top camera port, and over the bottom circular dovetail mount, so that no dust can make its way into the housing to foul the internal optics. Additionally, push the prism selector shaft on the right-hand side of the housing fully in, to the “V” position. Keeping the selector shaft in this position will do two things: 1) The selector shaft will be somewhat protected, since it will not protrude as far from the housing and will therefore be much less likely to be accidentally damaged. 2) The glass prism that selects the desired operating mode will be positioned such that there will be no glass directly exposed beneath the opening on the camera port. Any dust that does make its way into the camera port will tend to settle on bare metal, rather than exposed glass. If you choose to store the trinocular head in a large Ziploc bag, be sure to place a fresh desiccant package in the bag before you zip it closed. Otherwise, the humidity in the sealed bag can reach very high levels as the room temperature fluctuates, which can contribute to fungus growth. Be sure to replace or recharge this desiccant packet every few months.