What is the function of a microscope objective?
(1) According to the length of the microscope tube (in mm): use a 160 tube for transmitting light, with a 0.17mm thick or thicker cover glass; Reflected light using a 190 lens tube, not
Cover glass slide; Transmitted and reflected light are transmitted through a lens tube with an infinite length.
⑵ According to the characteristics of immersion method: non immersion (dry), immersion (oil immersion, water immersion, glycerol immersion, and other immersion methods).
⑶ According to optical devices: transmissive, reflective, and catadioptric.
(4) According to numerical aperture and magnification: low magnification (NA ≤ 0.2 vs β≤ 10X), medium magnification (NA ≤ 0.65 vs β≤ 40X), high magnification (NA>0.65 vs
β> 40X).
(5) According to the different situations of correcting aberration, it is usually divided into achromatic objective, semi achromatic objective, achromatic objective, flat field achromatic objective, and flat field achromatic objective
Field of view apochromatic objective and monochromatic objective.
Achromatic objective is a common type of objective (Table 1-1), which is composed of several sets of surfaces with different radii, one positive and one negative, glued through
Mirror composition can only correct the axial color difference between red and blue light in the spectral line. Simultaneously corrected for both on axis point spherical aberration and near axis point coma aberration, this type of objective cannot
Eliminate the secondary spectrum, only correct the spherical and chromatic aberration in the yellow and green wave regions, without eliminating the remaining chromatic aberration and spherical and chromatic aberration in other wave regions, and image distortion
The song is still very large, which means that only a clear image in the middle range of the field of view can be obtained. When using, it is advisable to use yellow green light as the lighting source or insert it in the optical path
Yellow green filter. This type of objective has a simple structure, is economical and practical, and is often used in conjunction with Fugen eyepieces and correction eyepieces. It is widely used in China
On a low magnification microscope. In black and white photography, a green filter can be used to reduce residual axial color difference and obtain a photo with good contrast.
2. Apochromatic objective is a combination of multiple sets of advanced lenses made of special optical glass and fluorite. Add red, blue
The yellow light corrects the axial color difference and eliminates the secondary spectrum, resulting in good image quality. However, there are many lenses and it is difficult to process and calibrate. Correction of color difference
All wave regions of visible light. If a blue or yellow filter is added, the effect is better. It is the best objective lens in a microscope, which is sensitive to both spherical and chromatic aberration
It has good correction and is suitable for high magnification. However, it still needs to be used in conjunction with compensating eyepieces to eliminate residual color differences.
The Plana chromatic objective adopts a complex optical structure composed of multiple lenses, which can effectively correct astigmatism and image field curvature,
Enable clear display of the entire field of view, suitable for micrography. The correction of spherical and chromatic aberration by this objective is still limited to the yellow green wave region, and there is still room for improvement
Color difference.
4. Planapochromat objective lenses (PF, Planapochromat), except for further image field bending correction, all other aberrations are corrected to the same degree as those of apochroma
The objective lens is the same, making the image clear and flat; But the structure is complex and manufacturing is difficult.
5. Half apochromatic objective: Some lenses are made of fluorite, so it is also known as fluorite objective, and its performance is better than that of apochromatic objective,
Price ratio
