(1) According to the length of the microscope barrel (in mm): 160 lens barrel for transmitted light with a cover glass of 0.17mm thick or thicker; 190 lens barrel for reflected light, no
With cover glass; tube for transmitted light and reflected light, the tube length is infinite.
(2) According to the characteristics of the immersion method: non-immersion (dry), immersion (oil immersion, water immersion, glycerin immersion and other immersion methods).
(3) According to the optical device: transmission type, reflection type and catadioptric type.
⑷ According to numerical aperture and magnification: low magnification (NA≤0.2 and β≤10X), medium magnification (NA≤0.65 and β≤40X), high magnification (NA>0.65 and β≤40X)
β>40X).
⑸According to the situation of correcting aberrations, it is usually divided into achromatic objectives, semi-apochromatic objectives, apochromatic objectives, flat-field achromatic objectives, and flat-field achromatic objectives.
Field Apochromatic Objectives and Monochromatic Objectives.
⒈Achromatic objective lens (Achromatic) is a relatively common objective lens (Table 1-1), which consists of several groups of different surface radii, one positive and one negative glued together.
It is composed of mirrors that can only correct the axial chromatic aberration of red and blue light in the spectral lines. Both on-axis spherical aberration and paraxial point coma are corrected at the same time. This objective lens cannot
Eliminate the secondary spectrum, only correct the spherical aberration and chromatic aberration in the yellow and green wave regions, but not eliminate the residual chromatic aberration and spherical aberration and chromatic aberration in other wave regions, and the image field is curved.
The curvature is still very large, that is, only a clear image in the middle of the field of view can be obtained. When using, it is advisable to use yellow-green light as the illumination light source, or insert it in the light path
Yellow-green filter. This type of objective lens is simple in structure, economical and practical, and is often used in conjunction with Forgan eyepieces and correction eyepieces.
on a low-power microscope. In black and white photography, a green color filter can be used to reduce residual axial chromatic aberration and obtain photos with good contrast.
⒉ Apochromatic objective lens (Apochromatic) It is composed of several groups of special optical glass and advanced lens groups made of fluorite. red, blue,
The yellow light corrects the axial chromatic aberration and eliminates the secondary spectrum, so the image quality is good, but there are many lenses, and it is difficult to process and align. Chromatic aberration correction in
All wavelengths of visible light. It will be better if you add a blue or yellow filter. It is the best objective lens in the microscope, and it is resistant to spherical aberration and chromatic aberration.
It has better correction and is suitable for high magnification. However, it still needs to be used in conjunction with compensating eyepieces to eliminate residual chromatic aberration.
3. Plana chromatic objective lens (Plana chromatic) adopts a complex optical structure of multi-lens combination, which can better correct astigmatism and curvature of field.
The entire field of view can be clearly displayed, suitable for photomicrography. The correction of spherical aberration and chromatic aberration by this objective is still limited to the yellow-green wave region, and there are residual
chromatic aberration.
⒋Plana apochromat objective (PF, Planapochromat) Except for further correction of field curvature, other aberration correction degrees are the same as those of apochromat.
The difference objective lens is the same, so that the image is clear and flat; but the structure is complicated and the manufacturing is difficult.
⒌Halfapochromatic objective lens is made of fluorite, so it is also called fluorite objective lens. Its performance is better than that of achromatic objective lens.
Cheaper than apochromatic objectives. The degree of correction of aberration is between achromatic and apochromatic objectives, but other optical properties are the same as the latter
Similar; inexpensive, best used with compensating eyepieces.
6. Special objective lens The so-called special objective lens is specially designed to achieve certain effects on the basis of the above objective lens. There are mainly the following according to the use
Several:
1) The phase contrast objective is a special lens for phase contrast microscopes (of course, it can also be used routinely).
The characteristic is that a phase plate is installed at the rear focal plane of the objective lens, which has achieved the purpose of delaying the light wave.
2) The correction collar objective has an annular adjustment ring in the objective. Adjustable when turning the adjusting ring
The distance between the lens groups (usually the second and third group lenses) within the objective lens, thereby correcting for coverage caused by non-standard cover glass thicknesses
Difference.
3) The iris diaphragm objective is equipped with an iris diaphragm in the upper part of the objective lens barrel, and there is also a rotatable outside.
The adjustment ring can adjust the size of the aperture of the diaphragm when it is rotated. This structure is the most advanced oil immersion objective.
4) The strain-free objective lens overcomes the existence of stress in the assembly of the lens group, and is specially designed for transmission type.
The objective lens for polarizing microscopy can achieve better polarizing microscopy results.
5) A non-fluorescing objective is an objective lens dedicated to epi-fluorescence microscopes. This objective lens is subject to
It does not fluoresce even when a strong excitation light source is used.
6) No cover objective (no cover objective) Some objects to be inspected, especially smear films, etc., cannot be covered with a cover glass, so that
A cover-free objective lens should be used during microscopy, otherwise the image quality will be significantly degraded, especially at high magnification.
