The primary functions of an aperture in an optical system encompass limiting beam aperture, restricting field of view, enhancing image quality, and eliminating stray light, among others. Specifically:
1. Limiting Beam Aperture: The aperture determines the amount of light flux entering the system, thereby influencing the illuminance and resolution of the image plane. For example, the circular diaphragm on a camera lens (commonly referred to as the aperture) serves as an aperture diaphragm that restricts the size of the incident beam.
2. Restricting Field of View: The field of view diaphragm is employed to limit the extent of the image. In photographic systems, the film frame acts as the field diaphragm, constraining the range of the image that can be formed in object space.
3. Enhancing Imaging Quality: By appropriately positioning the diaphragm, aberrations such as spherical aberration and coma can be minimized, thus improving imaging quality.
4. Eliminating Stray Light: The diaphragm blocks non-imaging light, thereby enhancing contrast. An anti-stray diaphragm is utilized to obstruct scattered or multiply reflected light and is commonly found in complex optical systems.
The classification of diaphragms includes the following:
Aperture Diaphragm: This directly determines the aperture angle of the imaging beam at a point on the axis and is also known as the effective diaphragm.
Field Diaphragm: This limits the spatial range of the image that can be formed, such as in the case of a camera film frame.
Anti-Noise Diaphragm: This is used to block scattered light or multiply reflected light, thereby improving the contrast and clarity of the system.
The working principle and function of a variable diaphragm are based on its ability to control the amount of light passing through by adjusting the aperture size. By rotating or sliding the diaphragm blades, the aperture size can be continuously adjusted, enabling precise control over the amount of light. The functions of a variable diaphragm include adjusting exposure, controlling depth of field, protecting the lens, and shaping the beam, among others. For instance, under strong light conditions, appropriately reducing the aperture can decrease the amount of light entering the lens, thereby preventing damage caused by overexposure.
Post time: Jun-21-2025