- What is the difference between a stereo microscope and a compound microscope?
- What is the difference between resolving power of an objective and resolution?
- How do N.A. and magnification relate to the brightness of an image?
- What is “Depth of field”?
- What is Dioptric correction or adjustment?
- What is meant by eyepoint?
- Explain What “Field Number” means?
- What is “Field of view”?
- What is Interpupillary Distance?
- What is meant by parfocal?
- What does working distance mean?
- How is Total Magnification calculated?
- What is meant by the term “Useful Magnification”?
- Why do some objectives require immersion oil or water?
- Why do some objectives have an iris?
- Do I need special objectives for darkfield microscopy?
- What does the inscription "0.17" on the objective mean?
- What does the objective inscription "160" mean?
- What is an infinity-corrected objective?
- Why do some objectives have the inscription "Plan"?
- Why do objectives usually have a color ring on them?
- What do the inscriptions "LWD" or "ULWD" mean on an objective?
- What do objectives with the inscriptions "NIC" or "DIC" mean?
- Why do some objectives have a spring-loaded front lens?
- Why am I getting a worse image with a 40X than with a 20X objective?
- Can I use phase contrast objectives for other types of observation?
- Can I use an infinity-corrected objective on a finite tube length microscope?
- What does "C" or "K" or "WF" or "H" mean when printed on the eyepieces?
- What is a photo-eyepiece?
- Why Can't I use eyepieces of increasingly higher magnification to achieve higher total magnification?
- What does a neutral density filter do?
- What is a daylight blue filter, and Why do I need one?
- How is a daylight blue filter used?
- Why place a green filter in the light path?
- What is the difference between achromat & plan achromat objectives?
- What does "DIN" standard mean?
- What does "FN" stand for?
- What kind of illumination options do you have?
- What is the difference in types of illumination?
- What does coaxial mean?
- What is darkfield microscopy?
- What is brightfield microscopy?
- What is phase contrast?
- What is oil immersion?
- Can I add a mechanical stage to my microscope?
- Can I attach a video camera to my microscope?
- Can I add a 35mm camera to my microscope?
- Can I attach a digital camera to my microscope?
- Can I clean my microscope myself?
- Whats the differences between a CCD and a CMOS camera?
What is the difference between a stereo microscope and a compound microscope?
A compound microscope has one optical path that is split at the observation tube that gives identical left and right images. A stereo microscope is like two compound microscopes side-by-side but with an offset from one another to mimic the natural offset of two eyes. It is the offset that provides depth perception in ordinary life and for the three-dimensional view or “erect image” in stereo microscopes.
What is the difference between resolving power of an objective and resolution?
Resolving power refers to the clarity with which an objective can clearly separate two points or lines lying close together. The shorter the distance between the points or lines, the greater the resolving power. Also the higher the N.A. (numerical aperture) number of the objective, the greater it’s resolving power. Resolution is the ability to distinguish two points as two points. One may need to compromise between resolving power and resolution to achieve the desired image.
How do N.A. and magnification relate to the brightness of an image?
The higher the N.A. value, for a given magnification, the brighter the image. A higher magnification reduces the brightness of an image.
What is “Depth of field”?
The height difference within features of an object that appear acceptably sharp when viewed with an optical instrument. Depth of field depends on the objectives, eyepieces and tube factor. Depth of field decreases when increasing magnification.
Dioptric correction is the compensation of long- or short-sightedness by the adjustment of the eyepieces.
Light rays from all points in the field of view converge together at this point. This is where the user’s eye must be positioned
The field number is the diameter of the eyepiece lens usually expressed in millimeters.
Field of View, or FOV, is the amount of the object that can be seen with a particular optics combination. It is the circular area which can be seen when looking into a microscope. It is a combination of objective and eyepiece characteristics and field of view decreases with increasing magnification. In most cases, the field number of the eyepiece can be used to determine the FOV or field size using the following formula:
Field Size = Field Number ÷ Objective Magnification
Interpupillary Distance is the distance between the centers of the pupils of your two eyes.
A stereo microscope can be said to be “parfocal” when an object can be observed from the lowest magnification to the highest without having to re-focus
The working distance is the distance from the object plane to the front of the objective.
Working distance decreases each time a higher-power objective is used.
The total magnification a microscope configuration is calculated from the magnifying power of the objective multiplied by the magnification of the eyepiece and, if installed, multiplied by the auxiliary lens.
Useful magnification is obtained when the magnification is between 500 and 1000 times the numerical aperture of the objective. Since the human eye has limited resolving power, the magnification should be selected so that the image details can still be distinguished by the eye. If the magnification falls below this range, details can no longer be recognized by the eye. If the magnification is above this range, this is simply referred to as “empty magnification” as the objective is no longer able to resolve structures. The image therefore appears out of focus.
The resolving power of an objective lens depends on its numerical aperture, which in turn depends on the refractive index of the medium between the specimen and the objective lens. A higher refractive index means the lens can gather more light and deliver a better image intensity. Air has a relatively low refractive index, and when it is the medium between specimen and the lens, lower N.A. objectives perform at their best capacity. Higher N.A. objectives need a higher refractive index to operate and immersion oil provides that higher index. For optimum performance, you will also need to oil the top lens of the condenser to the bottom of the specimen slide. Immersion objectives are marked "oil" or "oel". Objectives marked "wi", require water as the immersion contact medium.
In order to preserve darkness of the background for darkfield microscopy, the objective cannot have an N.A. higher than the lowest N.A. marked on the darkfield condenser. An iris that can reduce an objective's N.A., can allow you to use higher N.A. objectives for darkfield work. Objectives with an N.A. above 1.2 require an iris for darkfield. For ordinary brightfield observation, the iris can simply stay wide open.
In most cases, from a transmitted light observation, you will only need a darkfield stop in the condenser. At higher magnifications, you will need an objective with an iris as well as a darkfield condenser.
The "0.17" refers to the thickness in millimeters of the cover glass that was assumed by the lens designer in computing the corrections for the objective. For objectives with a numerical aperture higher than 0.45, departing from this thickness (or using no cover glass at all) may result in a less than satisfactory image.
The 160 identifies a finite tube-length objective, with a distance of 160mm from the nosepiece (where the objective screws in) to the top of the observation tube (where the eyepiece inserts). When you lengthen this distance by inserting accessories in the light path above the nosepiece, spherical aberrations will occur unless the accessories include the proper optical corrections.
With an infinity-corrected objective, light rays emerge in parallel projected toward infinity. Such an objective requires a tube lens in the light path to converge the parallel rays so that they come into focus at the eyepiece diaphragm.
A plan objective projects a flat image of the entire field of view.
With standard colors for most manufacturers, these rings make it easy to identify the magnification of the objective:
- A red ring means 4X or 5X.
- A yellow ring means 10X
- A green ring means 20X
- A blue ring means 40X, 50X or 60X
- A white ring means 100X
These letters identify long or ultra-long working distance objectives where the working distance is much longer than standard objectives of similar magnification.
These letters designate an objective designed especially for use in Nomarski or differential interference microscopy. Meiji does not currently offer either method.
These letters designate an objective designed especially for use in Nomarski or differential interference microscopy. Meiji does not currently offer either method.
These objectives will have a very short working distance. To protect your microscope objective and your specimen, a spring-loaded front lens assembly retracts upon gentle contact with the stage or specimen. The retractable lens will not, however, protect against rough and continuous contact also known as “crashing” the objective.
The specimen may have a thicker cover glass than the standard 0.17mm, or you may have a thicker than normal glass slide. To improve the image, you might try using a dry objective with a correction collar, or you can try using 40X or 50X "oil immersion" objectives, since the immersion objective has less sensitivity to variations in cover glass thickness.
Yes. Just move the phase condenser to the brightfield or “empty” position and employ the standard Koehler illumination procedure.
No, because the finite system does not include a tube lens to focus parallel rays.
Microscope objectives do not include correction for lateral chromatic aberration and require a compensating eyepiece (labeled "C" or "K") to provide correction. "WF" signifies "widefield," meaning you can see more of the specimen at a given time. "H" signifies "high eyepoint," which means you don't have to put your eyes so close to the eyepiece during observation. These are typically meant for users who wear eyeglasses but anyone can use them.
Used for photomicrography rather than observation, a photo-eyepiece picks up the image delivered by the objective and projects it onto the film plane inside the camera. Photo-eyepieces usually come with low magnification power to lessen the chance of empty magnification when the images they project onto film are magnified.
To maintain useful magnification with satisfactory clarity and resolution, you must avoid empty magnification or making the specimen appear bigger but not clearer. In general, total magnification should not exceed 750X-1000X the N.A. of the objective. For example, with a 40X, N.A. 0.65 objective, the total magnification should be between 480X and 650X.
Neutral density filters absorb light evenly across the visible spectrum, thus lowering the intensity of light without changing its color temperature.
A "daylight blue" filter absorbs some of the yellow to red light from the microscope lamp, resulting in coloration much closer to natural daylight which is beneficial comfortable viewing.
Use of a daylight blue filter is intended for observation purposes only, providing a pleasant background to the field of view. Do not use this filter for photomicrography or with daylight color film.
Human eyes see the color green the best. And, since monochromatic light eliminates chromatic aberration, a green filter markedly improves the performance of achromats. In addition, phase contrast objectives give their best images with green light.
Objectives are corrected for field curvature and color aberration. The difference between Achromats and Plan Achromats is the degree of the flatness of field. When the image is in focus from the center towards its edges; the field is said to be "flat". In general, the flatter the field of an objective, the more lenses it contains and the more expensive the cost.
"DIN" is an abbreviation of "Deutsche Industrial Normen." This is a German standard that has been adopted internationally as an optical standard used in most quality microscopes. The focal tube length of a DIN objective is 160mm. The former standard was RMS ("Royal Microscope Society"), which had a longer tube length (170mm). Most DIN optics can be interchangeable. However, DIN and RMS objectives are not interchangeable.
A number usually engraved on an eyepiece, which refers to the diameter of a baffle or raised ring inside the eyepiece. The "FN" of “field number” determines the viewing field for the eyepiece.
Proper illumination is critical to obtain a good image through any microscope so this topic deserves some time to research. Meiji Techno offers several options from which to choose. Whatever your specimen may be, Meiji has the appropriate illumination source to help to produce the best image possible.
- Incandescent - Standard bulb filament, usually 6 -120V, 20 - 60W. Color temperature is "warm" and tends to look yellow.
- Halogen - Usually low voltage, cooler, more intense illumination. Temperature is ideal for color photography.
- Fluorescent - A "cool" system which produces more light and has longer bulb life than incandescent bulbs. Fluorescent illumination offers a more desirable color temperature (4100º Kelvin) with a "whiter" field of view and is more comfortable to the eyes.
Coaxial refers to the movement of coincident axes or gears that share one common axis. On the coaxial controls of a graduated mechanical stage, one knob controls the "X axis" movement and the other controls the "Y axis" movement. On a coaxial focusing system the fine focus control is inside of the coarse focus control.
Darkfield Microscopy is a method by which the specimen (transparent or semi-transparent) is seen as a bright object against a dark, usually black, background.
Brightfield is perhaps the most common type of microscopy found in schools, industry and medical fields. In brightfield microscopy, a transparent or translucent specimen either naturally colored or stained appears dark against a bright background or field.
A technique for revealing the structural features of microscopic transparent objects that cannot otherwise be accomplished with brightfield microscopy. Phase appears to achieve the same effect as staining a specimen (which would kill a live specimen).
Oil immersion is used with high power objective lens (usually 100X) as a medium between the lens and the cover slip. Because oil has the same light transmitting properties as glass, it cuts down the refraction of light rays. Other requirements include the use of a 1.25 Abbe condenser to be used.
A mechanical stage can be added to most Meiji Microscope models.
Yes. Video cameras, as long as they are the common "C-mount" type, can be used with most Meiji Microscope models.
Yes, with a universal adapter and “T-Mount” matched to your camera brand and model.
Yes, but some digital cameras require a special adapter to allow so. Depending on the threading. For more information please visit out main site HERE.
Blurred images are usually the result of a dirty, scratched or broken objective. "Black spots" are dirt particles in the eyepiece or dirt particles on head prism or mirrors. The following method works on them all:
The front lens of the objectives (particularly the 40X) should be cleaned after use by first brushing with a soft camel-hair brush to remove particles of dust, then by wiping gently with soft lens tissue, moistened with Xylene or clean distilled water and drying with clean lens paper immediately following. The objective should never be taken apart except by a qualified repair person. If dust is seen on the back lens of the objective, an all-rubber ear syringe or enema tube may be utilized to blow the dust out.
The eyepiece may be cleaned in the same manner as the objectives, except in most cases Xylene will not be required. In most instances breathing on the lens to moisten it, then wiping dry with clean lens tissue will be sufficient to clean the surface.
The finish of Meiji microscopes is hard epoxy and is resistant to acids and reagents. Clean this surface with a damp cloth and mild detergent.
Note: Use alcohol for difficult cleaning and as a last resort Xylene or Acetone. Be forewarned that use of these chemical cleaners will destroy lens coatings!
If the problem requires more than a simple cleaning, your Meiji Techno Representative can refer you to an experienced microscope service dealer in your area.
Whats the differences between a CCD and a CMOS camera?
CCD vs CMOS
Meiji Techno America allows Digital / Analog CCD and CMOS cameras to be mounted directly to a microscopes trinocular port using the proper C” mount adapter that match’s the chip size of the camera. Any digital or video camera with a “C” mount ( 1” diameter thread) can be mounted on any Meiji Techno Trinocular microscope ( 25.2 tube ) by using these “ C”- mount attachments. They are available with projection lenses of different powers allowing some control over the magnification and the field view. “CS” mount cameras with require part number V-5MM to be threaded on prior to installing the adapter. Meiji Techno America’s adapters depend on the quality of our Japanese lenses. Our microscope adapters are designed and developed individually for each camera’s lens system and therefore it effectively eliminates vignetting and minimizes optical errors often associated with photomicrography by a consumer digital /analog camera. The image quality, peripheral resolution and color rendering is optimum as you would expect for a high quality Japanese C” mount adapter from Meiji Techno.
Generally low end adapters in the market have one or more of the following problems often associated with photomicrography:
- Vignetting: Magnification, optical design error, or fundamental structural defect causes vignetting
- Linearity: Image may look distrorted (barrel distortion) especially at the peripheral area in focus
- Light and Shade Gap: Brightness between center and peripheral area looks different even if lighting is even
- Geometry Distortion: Compare to the center area, image is distorted and lower resolution in the peripheral area
- Luminous Point: White/Black spot may appear on the image because of the internal-reflection in the lens and lens tube
Introduction to Image Sensors
Since every Digital camera has a sensor, it is usually either a CCD or a CMOS type chip sensor. All sensors are analog devices, converting photons into electrical signals. The process by which the analog information is changed to digital is called Analog to Digital conversion. When an image is being captured by a network camera, light passes through the lens and falls on the image sensor. The image sensor consists of picture elements, also called pixels, that register the amount of light that falls on them. They convert the received amount of light into a corresponding number of electrons. The stronger the light, the more electrons are generated. The electrons are converted into voltage and then transformed into numbers by means of an A/D-converter. The signal constituted by the numbers is processed by electronic circuits inside the camera. Presently, there are two main technologies that can be used for the image sensor in a camera, i.e. CCD(Charge-coupled Device) and CMOS (Complementary Metal-oxide Semiconductor). Their design and different strengths and weaknesses will be explained in the following sections.
Image sensors register the amount of light from bright to dark with no color information. Since CMOS and CCD image sensors are ‘color blind’, a filter in front of the sensor allows the sensor to assign color tones to each pixel. Two common color registration methods are RGB (Red, Green, and Blue) and CMYG (Cyan, Magenta, Yellow, and Green). Red, green, and blue are the primary colors that, mixed in different combinations, can produce most of the colors visible to the human eye.
In a CCD sensor, the light (charge) that falls on the pixels of the sensor is transferred from the chip through one output node, or only a few output nodes. The charges are converted to voltage levels, buffered, and sent out as an analog signal. This signal is then amplified and converted to numbers using an A/D-converter outside the sensor. The CCD technology was developed specifically to be used in cameras, and CCD sensors have been used for more than 30 years. Traditionally, CCD sensors have had some advantages compared to CMOS sensors, such as better light sensitivity and less noise. In recent years, however, these differences have disappeared. The disadvantages of CCD sensors are that they are analog components that require more electronic circuitry outside the sensor, they are more expensive to produce, and can consume up to 100 times more power than CMOS sensors. The increased power consumption can lead to heat issues in the camera, which not only impacts image quality negatively, but also increases the cost and environmental impact of the product. CCD sensors also require a higher data rate, since everything has to go through just one output amplifier, or a few output amplifiers.
Early on, ordinary CMOS chips were used for imaging purposes, but the image quality was poor due to their inferior light sensitivity. Modern CMOS sensors use a more specialized technology and the quality and light sensitivity of the sensors have rapidly increased in recent years. CMOS chips have several advantages. Unlike the CCD sensor, the CMOS chip incorporates amplifiers and A/D-converters, which lowers the cost for cameras since it contains all the logics needed to produce an image. Every CMOS pixel contains conversion electronics. Compared to CCD sensors, CMOS sensors have better integration possibilities and more functions. However, this addition of circuitry inside the chip can lead to a risk of more structured noise, such as stripes and other patterns. CMOS sensors also have a faster readout, lower power consumption, higher noise immunity, and a smaller system size. It is possible to read individual pixels from a CMOS sensor, which allows ‘windowing’, which implies that parts of the sensor area can be read out, instead of the entire sensor area at once. This way a higherframe rate can be delivered from a limited part of the sensor, and digital PTZ (pan/tilt/zoom) functions can be used. It is also possible to achieve multi-view streaming, which allows several cropped view areas to be streamed simultaneously from the sensor, simulating several ‘virtual cameras’.
A CMOS sensor incorporates amplifiers, A/D-converters and often circuitry for additional processing, whereas in a camera with a CCD sensor, many signal processing functions are performed outside the sensor. CMOS sensors have a lower power consumption than CCD image sensors, which means that the temperature inside the camera can be kept lower. Heat issues with CCD sensors can increase interference, but on the other hand, CMOS sensors can suffer more from structured noise. A CMOS sensor allows ‘windowing’ and multi-view streaming, which cannot be performed with a CCD sensor. A CCD sensor generally has one charge-to-voltage converter per sensor, whereas a CMOS sensor has one per pixel. The faster readout from a CMOS sensor makes it easier to use for multi-megapixel cameras. Recent technology advancements have eradicated the difference in light sensitivity between a CCD and CMOS sensor at a given price point.
CCD and CMOS sensors have different advantages, but the technology is evolving rapidly and the situation changes constantly. Using the proper C” mount adapter from Meiji Techno America will maximize your image quality that you are seeing through your microscope lens.
Note: Reduction lenses (i.e. magnification factors less than 1.0x) are commonly used to compensate for the increased magnification factor inherent with cameras used on microscopes.
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