Archive for September, 2015

What do you call a Drosophila who likes to drink? A bar fly!

Long hours under the microscope are no joking matter!

The thought of a Drosophila headed to the local bar for a drink creates a funny joke, but after long hours of sorting flies under a microscope that causes eyestrain or neck pain, you may be the one that wants to head to the local bar for a drink!

Unfortunately most users do not know why they experience discomfort when using a stereo microscope. Users who have several microscopes to choose from in a lab or in a manufacturing inspection setting simply sit down and use the preferred microscope. They tell their co-workers that they like to use one over another but they cannot explain why.

While preference may be for something such as ergonomics, a common cause is simple: one requires eyes to rotate inward and the other allows the eyes to relax and look through the microscope “straight on.”

Greenough v Galilean Optical Paths

Many Blood Moons ago around 1890, the American biologist and zoologist Horatio Greenough introduced a design to microscopy that would provide an accurate representation of the sample with a large field of view, low magnification, and depth perception. The design was simple, create a light path for each eye where the lenses are mounted at a 12.5 degree angle and focused on the sample at a center location.

a) CMO optical design that uses a single objective to combine right and left light paths to generate a stereo image.
b) Greenough optical design that angles light toward a center point beginning from the eyepieces.

Since the image is passing through the center of every lens in the optical system, the design produces a quality image that is still being used today in many stereo microscopes. However, the 12.5 degree angle causes the eyes to have to rotate inward often causing discomfort.

Fast forward to 1957 when the American Optical Company introduced their Common Microscope Objective (CMO) design. The new design took inspiration from the Galilean telescope where each eye would have a series of lenses that were mounted flat and the image would be bent inward and focused by a single lens at the bottom of the microscope. Correction for the single lens is more challenging, but this design provides users with the sensation of looking across the room, as opposed to the tip of one’s nose!

Eyestrain Doesn’t Just Hurt Eyeballs

Although eyestrain is an acute ailment that disappears quickly after walking away from the microscope, the effects of eyestrain can be felt for some time. In severe cases eyestrain can lead to all types of headaches. For some users the sensation is immediate, where for others it takes hours to detect the discomfort.

Although graduate students and lower-level employees are accustom to working through less-than-ideal conditions, no one should be denied the joys of a genetic screen or solder inspections because of a headache caused by eyestrain!

The experience is easy to recreate by attempting to focus on the tip of your nose. After just a few moments your eyes will begin to hurt! Although the sensation looking through the microscope is more similar to reading a newspaper a little too closely, and therefore may take hours to fully develop, the sensation is the same.

How to Adjust a Stereo Microscope for Comfort

Whether your stereo microscope is Greenough or CMO, the optics can be adjusted to optimize comfort. Based on design, CMO will always be more comfortable, but a simple adjustment can make a big difference.

On a Leica microscope the adjustment is easy. The eyepieces when rotated left or right, adjust the eyepiece lens in and out. Looking at the eyepiece housing, there are white markings that indicate whether the eyepiece is adjusted left or right of center. Center is the larger white line. Center the line on the eyepiece housing and shaft and proceed as follows:

  • Zoom out to the lowest magnification setting. Focus the microscope using both eyes. This gets you in the ballpark for the next steps.
  • Zoom to the highest magnification, refocus the microscope with both eyes.
  • Zoom to the lowest magnification again. Without focusing the microscope, twist the right eyepiece in both directions until the image comes into focus.
  • Close the right eye and open the left eye. Without adjusting focus on the microscope, twist the eyepiece until the left eye is focused on the sample.

  • At this point, with both eyes open, the sample should be perfectly focused. In addition, the zoom body will be parfocal throughout the zoom range! Repeat this process at high magnification and you will be in the best position for a comfortable viewing experience!

    Trust W. Nuhsbaum, Inc

    When choosing a stereo microscope for routine inspection or advanced imaging, it takes the knowledge and experience of a microscope specialist to ask the right questions that identify your needs. It also takes a company with the resources of W. Nuhsbaum, Inc to be able to demonstrate the difference in Leica quality regardless of Greenough and Gallelean stereo microscope design.

    Contact one of W. Nuhsbaum, Inc.’s microscope experts to learn more about the stereo microscopes that will make the difference in your work.

    Megapixel meltdown: Canon’s 250 megapixel sensor

    Megapixel Meltdown: Cannon announces the release of a 250 megapixel sensor

    With the recent release of a 250 megapixel sensor, the world of microscopy will never be the same. Or will it? Although microscope users will continue to demand higher resolution cameras it is not the primary factor for comparison.

    For years consumer electronics have lead the way in educating people in the standards for how to evaluate a camera. The most common standard – megapixels. Consumer camera manufacturers make little to no mention of the lens, resolving power, sensor noise, dynamic range, sensitivity or anything that actually influences quality images. So when Canon releases a 250 megapixel sensor, consumers immediately assume more is better – and that sensor should be connected to the microscope!

    Although the 250 megapixel sensor will allow an investigator to make a high resolution print the size of a small house, it will not allow said investigator to learn more about the sample in the image.

    Resolving power of optical system influences the need for sensor resolution

    Although camera sensors are amazing at capturing the detail in an image provided by a series of lenses, the series of lenses dictate the resolving power of the system. In short, unless the optical system is capable of resolving to the level of the camera pixel, the camera’s pixels are wasted. There could be more than one pixel capturing the same exact feature on the sample, providing your image a lot of pixels, but not a lot of data. Thankfully smart people who know numbers have worked out the details of digital sensors in microscopy. Some important equations are below:

    Optical Resolution (um) = (0.61 * wavelength)/(NA)

    Object size (um) = (Optical Resolution * Objective Magnification (i.e. 63X)/(c-Mount Adaptor)

    Nyquist Sampling Frequency: Object size/2.3 = Pixel Size to Resolve Object (um)

    Alternatively, if one would simply prefer plug numbers into a calculator, there is a web based calculator available also. Or for more information, Photometrics has an excellent learning zone dedicated to matching resolution.

    In the case of the Canon sensor, the pixels are about 1.49 microns across, so in the case of a compound microscope with a 10X objective lens with a numerical aperture of 0.4 and a lens free 1X c-mount, the ideal pixel size would be 3.646 microns. Or in the case of a stereo microscope with a 1X objective lens ideal pixel size would be about 3.5 microns.

    At 1.49 microns, the 250 megapixel sensor is at least 2X over sampling at low magnification and 8X over sampling at high magnification. Furthermore, this behemoth sensor is so big (29.2 x 20.2 mm) that it would require a magnifying intermediate lens to avoid vignetting – making the pixel size over sampling problem worse.

    Microscopes are made for imaging molecules, not mountains

    Nothing is more awesome than one upping a friend as it relates to Megapixels. If this were not true, Apple would not have released an iPhone with 4K streaming and a 12 megapixel sensor. Nothing like megapixels to make someone feel like their phone is obsolete…

    From the calculations above it’s clear that there is a limit to the value of megapixels as it relates to resolution. In the case of the 250 megapixel sensor, the developers never intended for the sensor to go onto a microscope, since they cite the sensors ability to read a serial number off an airplane from 11 miles away. Ideally Canon’s 250 megapixel sensor would be used for telescopes, not microscopes.

    When considering the specialized optics of light microscopes there are practical limits to resolution. Cameras that go beyond the three micron pixel size limit are simply offering users bragging rights, because there is not benefit to additional data.

    Real factors to consider when evaluating a camera

    While megapixels are a simple number to digest and compare across many different products, there are other factors to consider:

  • Quantum Efficiency

  • Read noise

  • Signal to noise ratio

  • Full well capacity

  • Dark current

  • Pixel size

  • Sensor size

  • All of these factors contribute to what many people will consider to be a beautiful image. Inky blacks with vibrant whites all while providing the field of view and resolution that is enough to record data.

    Trust W. Nuhsbaum, Inc.

    Choosing a camera can be intimidating, but the process can be made easy by consulting with the team of microscope and imaging specialists from W. Nuhsbaum, Inc. Trust the experience of W. Nuhsbuam, Inc to weather the technology winds of change and advise on the proper technology for your experiments.