1, the bright field of view is to let the light beam pass through the specimen and directly enter the objective lens, and the field of view is bright.

2. The dark field is a strong and narrow beam illuminating the specimen, which prevents the beam from directly entering the objective lens, but the particles in the specimen can scatter light, and some of these scattered light enters the objective lens, so you can also see the particles in the specimen glow on the dark background.

Extended data:

Dark field advantage:

1. Due to the large inclination angle of the incident beam in the dark field, the effective numerical aperture of the objective lens is increased, so the resolution of the objective lens is also improved. Observing under dark field illumination, even very fine wear marks are easy to distinguish.

2. Different from bright-field illumination, the light incident on the ground surface does not pass through the objective lens first, thus significantly reducing the reflection and glare caused by light passing through the glass-air interface for many times and improving the contrast of the final image.

3. Dark field observation can correctly identify the color of transparent nonmetallic inclusions. For example, copper oxide appears light blue when observed in the bright field of white light, but it can be seen as real ruby red when observed in the dark field. Therefore, dark field observation is extremely important in identifying nonmetallic inclusions.

Baidu encyclopedia-dark field