Compound Microscope and Digital Camera Microscope

What is the compound microscope?

·         Microscope is a tool which has the ability to magnify objects which cannot be seen by human necked eyes.

·         We observe the images of specimen aid in microscope but not the specimen.

·         More than one lens is used for a compound microscope.

·         Convex lenses are placed aligned named as object lens which is closer to the object and eyepiece (Ocular) lens which is closer to the observer’s eye.

·         Compound the microscope has usually two-step magnification. At first, the object is magnified by the object lens. Then images formed by object lenses are magnified by eyepiece (ocular) lenses.

What are the functions of the microscope?

1)      Magnification: Magnify the image of the objects.

         2)      Resolution: It is the ability to see two objects separately by the human eye. (With increasing of magnification, the resolution is also increased.) 

        Importance of compound microscope/ Digital camera microscope

               Measurement of parasite stages can be done by using a compound microscope/ Digital camera microscope. The family name or species name of a particular parasite can be identified by measuring the length and the width of the parasite stages (Eggs or larval). Therefore a particular parasite can be identified accurately by using a reference book so morphologically identification of the parasite is necessary for correct diagnosis.

            Parts of the compound microscope:

·         Stage: It is the surface where the slides are placed. It is a stationary stage. Slides are fixed into the stage aid in the clips on the stage.   

·         Sub stage: It is placed under the stage. It is comprised of a diaphragm or a condenser lens or both.

·         Diaphragm: The amount of light from the source is passed through the stage is regulated by the diaphragm.

·         Condenser lens: It is placed under the stage in order to focus light from the source. It does not involve magnifying the objects.

·         Objective lenses: They are attached to the nosepiece of the microscope.  A compound microscope is usually made of 3 objective lens such as scanning lens(x4),low power lens(x10)) and high power lens(x40).These 3 lenses are used with air.  Some microscopes also have oil immersion objective lens(x100) which is used with a drop of immersion oil between the lens and the slide.

·         Eyepiece (Ocular) lenses: It exists close to the observer’s eyes. It may be monocular and binocular. Eyepiece lenses magnify the image which proceeded by the objective lenses.

Total magnification= Magnification of objective lens x Magnification of eyepiece lens 

·         Coarse and fine adjustments: The stage of body is raised or lowered by using Coarse and fine adjustments. With the high power objective lenses, coarse adjustment must not be used.

Measurements of objects

Why calibration is requiring before measurement?

          We don’t know the value of a division of the eyepiece micrometer scale. Therefore eyepiece micrometer scale is calibrated by using a stage micrometer scale.

Stage micrometer scale: It is a normal microscopic slide which is marked with scale. The scale is divided into 100 divisions and one division is equal to 10µm.

Calibration of eyepiece microscope:

              After inserting eyepiece micrometer scale into eyepiece lens and placing stage micrometer scale in the stage, the microscope is adjusted to 0 line of both scale as in exact alignment. Then aligned divisions of both scales are detected. 

Let’s take an example.

10 division of stage micrometer scale is equivalent to 16 divisions of eyepiece micrometer scale.

10 SCD = 16 EMD

1 SCD= 10 µM

10 SCD= 10 X 10 µM= 100 µM

100 µM= 16 EMD

1 EMD= 100 µM/16

1 EMD= 6.25 µM

                 

Digital camera microscope:

A digital camera microscope is a microscope combined with a digital camera. The image of the objects is viewed by using the computer’s monitor.

It is allowed the observer to store the image on the computer. The magnification of the image depends on the size of the monitor.

Differences between the digital camera microscope the compound microscope

Compound microscope	Digital camera microscope
Focusing of microscope differs with people to people.	Focusing is constant.
Photograph of image cannot be taken.	Photograph of image can be taken.
It is time consuming method.	It is a time-saving method.
Length of width of organisms is taken by counting no of divisions.	Direct value of Length of width of organisms is taken without counting no of divisions.