With the advent of HD camcorders, zoom functions can be provided with the properly chosen camcorder with internal optical and digital zoom capability. Our optical coupling components hook it to the microscope.
Standard phase contrast view.
Rotate the turret condenser and you have a simple 3D differential interference
Rotate the turret condenser again and you have darkfield.
Move the zoom out on the camcorder and you have maximum field of view.
Hit the button or the remote control and zoom in on the object of interest.
Continue to zoom and you increase image size further.
All of the images shown here were obtained using a 40x non-
Rotate a 100x objective into place and you can achieve most unbelievable video magnification. The red blood cell here is video and optically magnified 38,000X. Want >100,000x magnification?
Use a large flat panel monitor.
The Story Behind Microscope Magnification and Zoom Systems
There is a bit of misunderstanding about magnification factors and zoom systems on microscopes and how they function. Part of the problem has been the creative marketing on the part of some microscope resellers.
Let’s set the story straight. The maximum magnification you can get on a standard light microscope is about 1250x to 1600x. This is viewing through the eyepiece with the naked eye which will also give you the finest detail you can see. This detail is termed resolution.
Though we can get large magnification with optical arrangements, digital video, and manipulating a camera up and down over the video coupling lens (the lens that connects the microscope to the camera and focuses the image to the camera chip), what we want is "useful" magnification, not “empty” magnification. Useful magnification is a function of resolution. Resolution is the limit up to which two small objects are still seen separately. It is used as a measure of the resolving power of a microscope.
Resolution in a microscope is a function of the numerical aperture of the objective (printed as NA on the objective). Digging into the mathematics, the maximum resolved distance is equal to the wavelength of the color of light through the specimen divided by 2NA. Going further, the maximum magnification possible with optimum resolution tops out at slightly less than 1000 times the NA. A 100x oil objective typically can have a numerical aperture of 1.3. so 1.3 X 1000 = 1300 as the theoretical limit of magnification with the most resolution. Since no manufacturer makes a 13x eyepiece (13x eyepiece X 100x objective = 1300 mag) we are left with the standard 12.5x eyepieces which gives 1250x magnification.
When a microscope is sold based on some ultimate magnification factor like 8,000x or 30,000x, this is simply related to the physical image size that appears on the video monitor. For example, a red blood cell is 7 to 8 microns in diameter. If you have a red blood cell that is 1 inch large on the video monitor, divide 8 microns into 1 inch (.0254 meters) and you will arrive at the number 3175. So a 1 inch red blood cell on the video monitor is magnified 3175x. Do you have any more resolution of that image than what you can see through the eyepiece at 1250x? No you do not. You just have a bigger image. But sometimes, bigger is better and in the case of microscopy viewing, it is a nice advantage.
One way to get a zoom function is through the use of a computer with a digital zoom software function. Choose the right imaging software and this is a built in function, so there is little extra cost to get this option if you are going through a computer. Computer video zooming is not dependent on a scopes maximum light intensity. However, when you are seeking more magnification using higher power objectives, optical zooms, or vertical camera adjustments (explained below), more light is needed to push the image through the optics.
Another zoom method that has been used by some manufacturers is through vertically adjusting the camera over the video coupling lens. For optimum focus, a camera should be set at one specific distance but these manufacturers take advantage of the physics of older style finite corrected microscope objectives which is older technology but still widely available. How it works is this: if you observe the principles of light and image projection, you will note that the further away you get from the place where you may be projecting an image to, the larger the image gets. By varying a camera’s distance over the projection lens (the video coupler) of a microscope, a zoom type effect can be achieved. It is not the best way to accomplish the job, but it is simple and inexpensive. One company, no longer in business, patented a motorized drives that make the vertical camera adjustment by simply pushing a button. Because of these patents, they were asking for a $20-
A third way to get a zoom function is with an optical zoom placed between the camera and microscope. This is far superior to the method mentioned above. It does not rely on magnifying the image with electronics, nor manipulating the camera distance from the video coupler, but by using optical lenses.
A fourth way is to use the built in optical and digital zoom function on the latest HD camcorders. With a consumer driven market where manufactures crank out large volumes of devices it means lower costs all around and with the right camera and optical connections to the microscope, this has become one of the best low cost zoom options.
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