Olympus CX23 Review

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ZodiacPhoto
Posts: 59
Joined: Sat Sep 24, 2022 6:53 pm

Olympus CX23 Review

#1 Post by ZodiacPhoto » Sat Mar 18, 2023 4:50 pm

I’ve got on my work bench an Olympus CX23 microscope. This is a current model, positioned as an educational microscope for schools and colleges. I decided to compare it to a laboratory-grade microscope (BX40) and see what you would sacrifice if you opted for a CX23 instead.

Probably the first thing you’d notice is how light this microscope is – specs say about 6kg / 13lb. It feels like a half of BX40. The internal aluminum-alloy frame is covered by plastic panels, and they are a bit creaky when you press on them hard. The upper frame is divided into two arms, this reminded me of a classic Steindorff Microbe Hunter https://www.microscopy-uk.org.uk/mag/ar ... dorff.html (I’d love to own one someday!).
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Being a “school” microscope, the 10x/20mm eyepieces and the 30° head are locked with additional screws, they require just a couple of turns to release. The four Plan Achromat objectives (4X, 10X, 40X, and 100X Oil) with F.N. 20mm are just set really tight in the nosepiece, no thread locker is used. I was able to unscrew them with a silicone pad with no problems and no marks left. Note how the inner optical elements of the 4X and 100X objectives protrude well beyond the objective thread into the nosepiece. This makes them unusable in other Olympus microscopes – they stop the revolver’s rotation when installed into BX40.

On the other hand, optics from BX40 – the objectives and the tilt head – fit perfectly in the CX23 and perform normally – the head dovetail is the same, and the air inside the two Olympus microscopes seems to be identical 😉
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CX23 uses an LED light source, and, for student’s safety (my guess), its max. brightness is limited but sufficient for transparent specimen observation. The LED has a visible magenta tint when viewed from outside, but it is not very noticeable when looking through the optics.

This microscope uses a simple Abbe 1.25 condenser, its height can be adjusted by a knob, and a variable aperture lever has markings at 4, 10, 40 and 100x positions. Olympus makes a kit containing a field diaphragm and a condenser centering lens https://www.olympus-lifescience.com/en/ ... ontent6318 to add Kohler illumination, if desired. Does anybody know where I can buy this kit in the USA, or has one for sale? I think the kits from older models (CH and CX series) would fit also – my filter holder from the old CH2 fits perfectly into this condenser.
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I tried to hand-hold the condenser from the BX40 under the stage, it fits fine and provides better contrast, but mounting it will require a 3d-printed adapter, as this condenser is mounted to the condenser carrier using 3 screws, not a dovetail.

The mechanical stage is rack-less, it uses wire to drive the specimen holder, its movement is precise and without any backlash.

I was pleasantly surprised how well the optics performs in this microscope – the 4x, 10x, and 40x (I did not test the 100x) Plan objectives create evenly lit, sharp image from edge to edge, without any hint of softness at the edges, and minimal chromatic aberration on par with Olympus BX40 Plan objectives – in fact, when the 22mm eyepieces from BX40 are installed in the CX23, the image remains sharp to the edge!

The small power brick can be inserted into the base, so only the power entry connector is accessible, so you can use it as a regular, brick-less microscope, if desired.
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What I liked:
- Lightweight
- Small footprint
- Great ergonomics
- I find it good looking, but it’s in the eye of the beholder, I guess
- Great optical performance
- Condenser is height-adjustable, has a diaphragm.
- Rack-less, precise mechanical stage
- Compatible with Olympus UIS/UIS2 optics (upgradeable)

What I did not like that much:
- Plastic panels are a bit creaky
- Frame and stage are not as sturdy as BX40, but this is expected (not flimsy in any way)
- LED has some magenta tint, limited max. brightness.
- Uses an external power brick (but small and hides in the base)
- Condenser is very basic, upgrading will require custom parts.
- Kohler illumination is not included (kit is available, but is difficult to find).

Why am I looking at microscopes like CX23? The work bench you see in the top photo is my electronic bench where I work on my electronics projects. I don’t have a dedicated place to use a microscope when I feel like it, so I have to bring the microscope from the closet to this bench. I have some back problems, and carrying something like BX40 I have now is difficult. I am in search for a “no optical compromise” lightweight microscope, I am not sure yet if this CX23 is the ticket… any ideas will be appreciated.

ZodiacPhoto
Posts: 59
Joined: Sat Sep 24, 2022 6:53 pm

Part 2 - Look inside

#2 Post by ZodiacPhoto » Sat Mar 18, 2023 8:00 pm

I’ve got this scope by sheer serendipity for free, but I had to spend two days cleaning it from some semi-hard goo and repairing it. Now it is in pristine shape, more or less.
Somebody used this glue-like compound liberally on the stage, and it leaked into everything below it (condenser, light source), and made all the lower panels look ugly. Luckily, it was washable!
Here are some photos of internal parts - I had to disassemble it completely for cleaning.
There may be more than one way to skin a cat, but there is only one way to skin (remove plastic panels from) a CX23:
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In the first part of the review I mentioned that the LED source has some magenta tint, but not very noticeable through the optics. Disassembly has shown that Olympus employed a Fresnel lens in the collector assembly above the LED, under the frosted glass. It looks like this Fresnel lens works like a prism of sort, sending some violet and blue parts of the spectrum outside, creating the magenta diffused light.
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In any case, the LED looks easy to replace if desired:
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The focusing assembly is an eccentric cam mechanism with a roller bearing, converting rotation of the focus knob into vertical linear motion of the stage. While many parts are plastic, this microscope is built to withstand student's use (and abuse), and I hope this mechanism is reliable enough, especially in somebody's careful personal use:
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Thanks for reading, let me know if you have any questions!

apochronaut
Posts: 6272
Joined: Fri May 15, 2015 12:15 am

Re: Olympus CX23 Review

#3 Post by apochronaut » Sun Mar 19, 2023 1:31 pm

Thanks for posting that. It is a very good primer for the scope and reduces a lot of guesswork about it's relative value and potential future usefulness.

dirigibil
Posts: 21
Joined: Sat Feb 11, 2023 5:16 pm

Re: Olympus CX23 Review

#4 Post by dirigibil » Sun Mar 19, 2023 3:22 pm

Why do the CX objectives have optical parts that go into the nose? Is this on purpose to keep people from using the E Plans on non-student scopes or is there a technical reason?

ZodiacPhoto
Posts: 59
Joined: Sat Sep 24, 2022 6:53 pm

Re: Olympus CX23 Review

#5 Post by ZodiacPhoto » Sun Mar 19, 2023 4:24 pm

dirigibil wrote:
Sun Mar 19, 2023 3:22 pm
Why do the CX objectives have optical parts that go into the nose? Is this on purpose to keep people from using the E Plans on non-student scopes or is there a technical reason?
An interesting question...
I don't have another Olympus 100x oil objective (don't have a need for immersion), but that's compare this 4X to a regular Olympus Plan 4X objective:
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I aligned both objectives that their front and rear elements are in the same plain. It looks like the distance between the front and rear elements is practically the same, but the whole lens is shifted about 8mm into the nosepiece:
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It can't be the same optical formula, because both objectives remain parfocal at 45mm. Also, I tried to mix CX23 objectives with BX40 objectives on the same microscope, to compare 10x to 10x and 40x to 40x performance, and they are perfectly parfocal to each other.
I found that there is almost no perceivable difference between CX23 objectives and regular Olympus UPlanC N objectives. Actually, CX23 objectives exhibit a bit less longitudinal CA (green / magenta shift for out-of-focus edges) than UPlans, but a bit more than UPlanFL - but the difference is minor.
If you are right, and Olympus wants to prevent usage of these relatively inexpensive and well-performing objectives on clinical scopes, why didn't that apply the same treatment to 10x and 40x objectives? I have no idea, strange...
Also, I've never seen CX23 objectives sold separately by Olympus distributors, maybe they only come with the scope.

dirigibil
Posts: 21
Joined: Sat Feb 11, 2023 5:16 pm

Re: Olympus CX23 Review

#6 Post by dirigibil » Sun Mar 19, 2023 5:05 pm

If you are right, and Olympus wants to prevent usage of these relatively inexpensive and well-performing objectives on clinical scopes, why didn't that apply the same treatment to 10x and 40x objectives?
Can you think of a reason why the 4x and the 100x would need to be shorter relative nose->stage than the non-E objectives? There has to be a reason... the engineering on these units is highly specialized and the models are long-running, they wouldn't have done it unless there was a specific need.

dirigibil
Posts: 21
Joined: Sat Feb 11, 2023 5:16 pm

Re: Olympus CX23 Review

#7 Post by dirigibil » Sun Mar 19, 2023 5:51 pm

OK what do you make of this? (pp345-346)

* https://www.researchgate.net/publicatio ... 7/download
The details of structural functionality in aberra-
tion correction will be discussed in Part II. Concerning
the manufacture accuracy of optical elements, in the
popular front group (B), although the embedded lens has
great advantage in field curvature correction and spheri-
cal aberration restraint, owing to its small clear aperture
(~1 mm), it is difficult to produce. The ‘ball technology’ is
usually used for the production, but the cost is relatively
high, particularly to realise high accuracy of the cement-
ing. Therefore, for the cost-driven systems, the front lens
is designed with a single lens. However, if the refractive
index of the lens is not large enough, to achieve high NA,
the shape of the lens tends to be hyper-hemisphere, which
cannot be mounted to the leading edge of the objective.
The front group (A) nearly reaches the maximum NA
(1.25), which could be achieved by single hemispherical
lens with d-line refractive index around 1.52.

According to Section 5.8, for superresolution localiza-
tion microscopy, owing to the strong illumination inten-
sity at the front group, the cementing surface in the (B)
type front group is vulnerable. However, if a single lens
is used, the maximum NA cannot fulfill the required
strong excitation. Utilising front group (C), the NA could
be further enlarged with the hyper-hemisphere, and the
optical contact bonding is not sensitive to the strong UV
illumination. Furthermore, the mounting of the front
group could be fixed at the edge of the thick plane plate;
thus the system assembly is feasible. The only risk is the
robustness of the ‘optical contact bonding’ technique.
According to this comparison, it could be seen that to
determine the shape of the front group, all three design
concepts are involved. Functionality in aberration correc-
tion determines the basic shape. The application fixed the
boundary condition. The final trade-off is associated with
the consideration of manufacture and technology.

Example II
Comparison shown in Figure 24 is similar to that in
Figure 16, but the difference between these two 60×
TIRF objectives is the choice of doublets or triplets in
correcting spherical and chromatic aberrations. Both
these two systems are apochromatic corrected for visible
range from g-line to C-line and utilised vignetting for field
correction.

The different parfocal length determines the mechan-
ical dimension to fill lenses. The 60×/1.48 45 mm parfo-
cal objective from Olympus used two cemented triplets in
the middle group, whereas the 60×/1.45 60 mm parfocal
objective utilised four doublets. These two setups have
similar functionality in spherical and chromatic aberra-
tion correction. But the triplet setup could relatively save
space (also beneficial from the stronger front lens).
The selection of cemented doublets or triplets also
highly depends on the coating technique of the manufac-
turers. Because of the strong veiling glare generated by
the air–glass interface, if excellent antireflection cannot
be realised by coating, the air–glass interface with strong
curvature should be avoided. Consequently, except the
functionality of aberration correction, the cemented tri-
plets utilised in the high-performance objectives are typi-
cally designed with stronger inner cemented surface and
flatter outer surfaces. On the contrary, if the veiling glare
could be controlled by coating, utilising cemented dou-
blets instead of triplets could introduce additional degree
of freedom for correction, which is advantageous in relax-
ing the system sensitivity.

Scarodactyl
Posts: 2775
Joined: Sat Mar 03, 2018 9:09 pm

Re: Olympus CX23 Review

#8 Post by Scarodactyl » Sun Mar 19, 2023 6:53 pm

Thank you, this is a great review!

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