Understanding Optical Images and Their Applications

What is an Image in Optics?

In optics, an image is a reproduction of an object formed by a lens or mirror system from reflected, refracted or diffracted light waves. An optical image can be real or virtual.

In geometric optics (as in flat mirrors), a point image is considered to be real. However, when the wave nature of light is taken into consideration a point image is actually a complex diffraction pattern.

Definition

An optical image is a representation of a real object or scene formed by optical instruments that manipulate and focus light waves. This includes cameras, microscopes, telescopes and other optical devices. An optical image can be projected onto a screen or recorded on film or an electronic sensor (such as in a digital camera).

The science of optics is concerned with the nature and properties of light, the changes it undergoes, and the principles that govern the image-forming capabilities of lenses and mirrors. One branch of the field is physical optics, which deals primarily with the physical properties of light and the physics of its propagation. The other is geometrical optics, which studies the image-forming properties of optical systems.

Optical imaging is the basis of visual perception. However, it is important to realize that a virtual optical image may be created even when no light rays ever reach the optical surface, because the rays that do appear to pass through the lens or mirror are dispersed in their path and never collect on a screen or photographic film.

Principles

In general, an optical image is an apparent reproduction of an object produced by a lens or mirror system using reflected, refracted or diffracted light. It can be either real or virtual, real if all the light rays converge at the point of the image and virtual if they scatter in all directions.

The maximum correspondence between an image and the object is achieved when each point of the object is represented by a point in the image. However, this is not possible for all points in an optical system, because the refractions and reflections introduce aberrations.

One of the most important is the angular aberration caused by the fact that an object point lies to one side of the optical axis. This causes the corresponding image point to be at a transverse distance from the axis, which can be approximated by the formula x’ = 2f h0’2S3 for a paraxial lens in air. This produces a circular ellipse in the image, with its major axis three times its minor axis.

Applications

Optical imaging provides a useful tool for determining multiple properties of soft tissue. It can be used to measure metabolic changes, which are early indicators of disease. It is a preferred technique for preclinical studies of new drugs, because it does not require radioactive exposure or radiation safety precautions.

The images of an object are created by a lens, which collects and reconstructs the light that strikes it. This information is stored on a light-sensitive surface, which is called the image sensor. Usually, the image sensors are CCD or CMOS-based.

Unlike other neuroimaging modalities, optical imaging of intrinsic signals offers both spatial and temporal resolutions that are optimal for examining cortical columns and their vascular supply. It is a user-friendly method, and initial data files can be analyzed without the need for special processing programs. Optical imaging can also be used to visualize gases that are not visible to the naked eye. This is important in industrial and environmental applications.

Equipment

A wide range of imaging devices is available. Some use specialized lenses to create images. Others, such as endoscopes and borescopes, provide images based on light transmitted through rigid tubes. Videoscopes and fiberscopes offer views based on infrared light. Image-processing systems can make an image of a part of a larger object and can even assemble several images into one picture.

In medical applications, optical technology provides advantages over X-ray and radiology imaging. It can use non-ionizing radiation and allow a physician to see at the molecular level, potentially helping them better understand biological processes and predict results of treatment.

A typical optical system includes lenses, mirrors, light sources and detectors. Optical detectors create an electrical signal based on the intensity of light detected, and may include photodiodes that convert light into electric current and a semiconductor that detects wavelengths. Light sources can be lamps, lasers and fluorescence. Relay lenses may be included to invert the field of view and extend the length of the system, such as in a military periscope.

Travel back to the main page

Leave a Reply

Your email address will not be published. Required fields are marked *