Reticle is generally also referred to as eyepiece reticle, or reticule, graticule, cross hair.
Reticle is any optical component with a certain mark placed inside the eyepiece. Base on different applictions, reticle can be used for measurement, calibration or aiming.
Reticle is mainly used for the measurement of length, angle or area of the object to be measured under the microscope. The reticle measurement is a non-contact measurement. that is, the measurement value is obtained by measuring the optical image without touching the object to be measured, which is very suitable for some small specimens, organisms, and irregular objects.
Eyepiece reticle has patterns of various shapes and sizes. Common types of eyepiece reticle are : straight, cross, mesh, circle, angle or combination shape. Between each grid it is also equidistant. However, for eyepiece reticle, one cannot read directly the number under the microscope, but convert firstly the multiple after magnification of the microscope objective lens. In short, after the object is being magnified by the objective lens, the real image of the object reached the focal length of the eyepiece (10mm below the fixed surface of the eyepiece), which is exactly the position of the eyepiece reticle, and what the eyepiece reticle reads is actually the image of the object after being magnified by the objective lens. Therefore, for the actual numerical value, the actual size of the image should be divided by the magnification of the objective lens.
In addition, for eyepiece reticle measurement, it can also be calibrated first by the objective micrometer before measurement. The method is: firstly, place an objective micrometer on the stage, after the focus is clear, record the magnification number of the objective. Then, the eyepiece reticle is overlapped with the scale pattern of the objective micrometer, so the the 0 points of the two are aligned, a scale value with a completely coincident scale is found backward, the grid values of the reticle eyepiece and the objective micrometer are respectively read and converted, and then the calibration value is used as the actual measurement value of the eyepiece reticle.
This method is relatively more complicated. First, it is necessary to constantly convert the reading and the calibration value of the eyepiece. Secondly, each time when the objective lens with different magnifications for observation is changed, it needs to be re-calibrated. This is only suitable for use in strongly repetitive microscope observations and work in order to be efficient.
