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Dino-Lite Digital Microscope Performance

Last Updated: 24th Oct 2013

By Mineralogical Research Company

The question often arises as to the technical competence and quality of the of the Dino-Lite line of digital microscopes. I am therefore responding to these questions based upon my observations, as first a user and later a dealer, as well as some technical data and measurements. In this short note, I provide objective information that will serve to put into perspective the quality and usefulness of the Dino-Lite Digital Microscope as a serious instrument capable of being used for scientific purposes.

Dino-Lite Digital Microscope in action


The mechanical design and construction of the Dino-Lite is rugged and well thought out. The most common models employ a high impact plastic body. A beautifully finished alloy body version is also available that adds a high-end touch to the instrument, though the optics and electronics are identical to the lower priced high strength plastic version. All of the Dino-Lite models share the same coaxial focus control, which is very smooth and easy to use. Most models have a magnification range of 20:1, or more. However, there are other ranges of magnification available, as shown below (Table 1).

Table 1. Field of View (FOV) & Working Distance (WD) for popular Dino-Lite models

MODELSMag. FOV max FOV min WD max WD min
AM4113TL-M405x - 34x 95x6010x8 42040
AD4113TL10x - 92x33.5x254.3x3.527048
AD4113T10x - 230x 50x37 1.6x1.31793.5
AM413T5500X 0.67X0.5430


The electronic and mechanical designs are robust and failures are very low at approximately 0.2%, by our experience.

The most frequent questions and comments are regarding the quality of the optics and resolution. To answer these questions, I had to query the factory and perform some simple tests. Currently, sixty different models of Dino-Lite Digital Microscopes are protected by U.S. Patent #7.112.817. Because other companies have tried to copy the Dino-Lite, proprietary information such as lens design, number of lens elements and performance specifications were not available. What I was able to confirm, from the factory, is that the lenses are manufactured from optical glass and are multi-coated, as opposed to the plastic lenses that are used in many of the very cheap knockoffs that are available on the grey market. The questions regarding performance, notably resolution, had to be answered by test.

The following two paragraphs will provide some background information and help to understand the conclusions drawn later in this note, but are not necessary if you don’t like the math. The resolution of any microscope is finite and a function of diffraction and the wave nature of light. Resolution is defined by R=0.61λ/NA, where R is resolution in nm, λ = average wavelength of the illumination in nm and NA = numerical aperture of the lens. Numerical aperture (NA) is dimensionless and is a somewhat better way to specify a microscope lens, as it doesn’t depend upon the wavelength of light, but only upon the geometry of the optical light cone.

I mention the following because a common request is for "sharp optics and large depth of field". The depth of field (D) of any microscope, with a numerical aperture in the range of ~0.05 – 0.3, is a function of its resolution and is defined by: D=(3.27R^2)/λ From this it can be seen that depth of field is less for high resolution microscopes and greater for low resolution microscopes. That is, you cannot have both high resolution and large depth of field. For two microscopes, with the same NA, the depth of field will be the same at a given magnification. We strive for high resolution, knowing that depth of field suffers as a result. This is the nature of light and the immutable laws of optical physics.

To compare the Dino-Lite optical resolution with other microscopes, a somewhat simple measurement of resolution was made. This allowed for the calculation of NA, which could then be compared with that of microscopes of known high quality. To obtain a reasonable approximation of the resolution, a calibration slide with 10um tic marks was used. Unfortunately a finer graduated slide, such as a resolution standard, was not available, as they are extremely expensive. The Dino-Lite model with the highest magnification (AM413T5) was selected in order to achieve maximum resolution. As can be seen in the photo below (Figure 1), the 10um spacing between lines (tics) is cleanly resolved.

Figure 1. Reduced full frame image of calibration slide taken with Dino-Lite AM413T5


It was conservatively estimated that, with finer line thickness, at least 3 subdivisions of the 10um tic marks could be resolved. That would equate to a resolution of approximately 3.3um, or 303 lines/mm. According to the Rayleigh criteria, the lines need not have clear space between them to be resolved, as long as they can still be discerned as separate lines. The numerical aperture can be calculated from the resolution.

NA=0.61λ/R=0.61X550nm/3300nm=0.1 or better.

To assure that the above assumption is correct, a crop of the slide image was taken and offset to divide the 10um tic marks by thirds (Figure 2).

Figure 2. Crop of previous image offset to divide the tic marks by thirds


The shifted tic marks are clearly resolved, so the estimate originally made is very conservative. The resolution is actually higher than estimated, by Rayleigh criteria. Finally, an optical test was implemented to physically measure the entrance acceptance angle of the lens. From the measured acceptance angle the numerical aperture was calculated and found to be in agreement with the calculations above. How does this compare with high end stereo microscopes? Nikon specifies their best stereo microscope objectives as follows (Table 2):

Table 2. Nikon Stereo Microscope Objective Specifications

Objective Magnification Color Code Numerical Aperture Working Distance (mm)
ED Plan 0.75x Yellow 0.068 117
ED Plan 1.0x White 0.09 84
ED Plan 1.5x Green 0.14 50.5
Plan Apo 1.0x N/A 0.1354
Plan Apo 1.5x N/A 0.21 24


From the table, the Nikon ED Plan 1X objective has an NA of 0.09, nearly equal to the Dino-Lite NA of 0.1. Keep in mind that higher NA results in higher resolution. The Dino-Lite has a resolution of greater than 303 lines/mm and has essentially the same resolution as that of the Nikon ED Plan 1X objective. The highest resolution Plan Apo 1.6X objective is only better by a factor of 2:1. Under the best of conditions, the Plan Apo 1.6X can resolve 625 lines/mm. Consider that these objective lenses are used on high end (>$10K) microscopes and it becomes obvious that the Dino-Lite has very credible performance at a fraction of the cost.

Below are comparison images taken of calibration slides. The instruments used (Figure 3.) were a Dino-Lite AM413T5 and a Nikon SMZ800 research grade stereo microscope with 1x ED Plan objective lens (NA=0.09). Both of the images, which are small crops of the original images, were taken at the maximum magnification of the instrument. A 1.3MP camera was used on the Nikon scope because it matched the sensor size and resolution of the Dino-Lite. It is hard to dispute the similar performance shown in the comparison images (Figure 3). The difference in line thickness is due to two different calibration slides being used.

Figure 3. Resolution comparison


An examination of the reduced full frame of the test slide (Figure 1) will give some measure of the very good field flatness and lack of geometric distortion that is inherent to the Dino-Lite optical system. Chromatic aberration (color fringing) is very good out to the edge of the field.

The simple tests described here were performed to provide objective data with which to judge the level of performance that can be expected from the Dino-Lite and to demonstrate that the Dino-Lite models are of sufficient quality and precision to qualify as serious and capable scientific instruments. The following images were made with the Dino-Lite AD4113T, which has a magnification range of 10x-230x.

Artinite
Boltwoodite
Wulfenite
Artinite
Boltwoodite
Wulfenite
Artinite
Boltwoodite
Wulfenite


Boleite, Pseudoboleite
Aurichalcite
Rutile
Boleite, Pseudoboleite
Aurichalcite
Rutile
Boleite, Pseudoboleite
Aurichalcite
Rutile




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Comments

Nice review! Were any of these test images made from stacked photos?
Steve.

Steven Kuitems
25th Oct 2013 9:04pm
Thanks Steve, I hope that it was informational. Only the Boltwoodite is a stacked image, as it was just too deep. The others are all single images.

Mineralogical Research Company
26th Oct 2013 12:48am
Thanks for this nice review. People have been asking me about this instrument, so now I can simply refer them to your article. The above images are very good. I note that the artinite image is also a stack because it shows ghost artifacts around the crystals and "reflections" around the image's perimeter. These are typical artifacts of unedited stacks, such as the boltwoodite image.

Harold Moritz
28th Oct 2013 1:09pm
You have a keen eye, Harold! I went back and looked at the properties for the Artinite and yes, it was processed with CombineZ. The picture is about 3 years old, before I had Zerene Stacker and I forgot that it had been stacked. At that time I was just turning the focus knob to increment the focus, so it wasn't done with any accuracy.

Gene Cisneros

Mineralogical Research Company
28th Oct 2013 3:41pm
Once again, many thanks Gene. That article will be very useful to me, and even a mathematical dolt like myself can understand the details...

Tim

Timothy Greenland
29th Oct 2013 11:46am
Tim,

Your kind comments are appreciated.

Gene

Mineralogical Research Company
30th Oct 2013 1:30am

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