Brightfield Illumination and Darkfield Illumination are two common illumination techniques used in microscopes and machine vision systems, which provide different visual effects and contrast when observing and analysing samples.

Bright field lighting:

1, Bright field illumination is an illumination method in which the illumination light directly transmits the sample or is reflected by the sample into the objective lens, thus displaying the image of the dark-coloured sample on the bright background.

2, Principle of illumination: bright field illumination is mainly divided into two kinds, one is the transmitted light bright field of view illumination, light through the transparent object (such as transparent glass grating, etc.), the light is modulated by the transparent grating with different transmission ratios. If the light passes through the glass plate without defects, it produces a uniform bright field of view.

3, Application Scene: Bright field illumination is the most commonly used illumination method in machine vision applications, with clear image details and obvious contrast, suitable for detection and identification of edge, texture and pattern features. It is suitable for the occasions that need to clearly show the surface details and texture of the illuminated objects.

Dark field lighting:

1、Dark field illumination is a method of illumination in which only the beam of light scattered by the object particles enters the objective lens and forms a bright image of the object in the dark field of view, generally used to improve the contrast of unstained transparent samples.

2, Principle of illumination: In optical microscopy, dark field describes an illumination technique used to enhance the contrast of unstained samples. Its main working principle is that the light illuminating the sample will not be collected through the objective lens and therefore will not form part of the image, resulting in a dark, almost black background and the appearance of bright objects.

3. Application Scenario: When dark field illumination is used, the image edges are clear but the details are not obvious, which is suitable for vision applications that focus on edge feature detection. Suitable for occasions where the shape and outline of the illuminated object needs to be highlighted, etc.