Successful Light Polarization Techniques
Edmund Optics Inc.

Successful Light Polarization Techniques

Understanding Polarization Axis

Video and machine vision systems rely on electronic imagers that typically exhibit anywhere from eight-bit to twelve-bit signal-to-noise ratio. Although sufficient for many applications, cameras in this category may be problematic in cases where the field of view includes extremely bright regions or hot spots. Some objects have certain features that are extremely reflective, or objects may be illuminated from an angle that produces intense reflection. Light polarization filters offer solutions to these and other common imaging problems.

Understanding Polarization Axis

By considering light as an electromagnetic wave, we realize that in three-dimensional space a wave can oscillate up and down, side to side, or anywhere in between. Incandescent, fluorescent, LED, and many laser light sources are randomly polarized. In other words, the oscillating angle or plane of light from each point on the light source is varying with time. Taken as a time average, therefore, randomly polarized light sources continuously output all angles of polarization.

Polarizers absorb incident light oscillating in all but one plane - its polarization axis - yielding linear polarization. Another example of polarization is the partial polarization of light reflecting from a plane surface, an effect less dramatic than a polarizer element. Linear polarization of a randomly polarized light source reduces the intensity of the source theoretically by 50%, and in practice closer to 60-65%. Light that passes through two polarizers with orthogonal polarizing axes will be completely attenuated. However, the almost total elimination of hot spots and glare is exactly what makes a polarizer effective in evening out illumination levels within a field.

Application Examples

Shown are examples of some common polarization of light techniques used in imaging applications. By utilizing a linear polarizer over the light source, the lens, or both, it is possible to eliminate glare from a reflective surface, bring out surface defects or show stress in a transparent object. More detailed information on which type of polarizer is right for your application can be found in our Polarizer Selection Guide.

Eliminating Hot Spots: Hot spots are highly reflective areas within a more diffuse reflecting field. Polarizing the light that strikes these reflective areas, and using a crossed polarizer over the lens, effectively eliminates the hot spots, while evenly illuminating the rest of the field.

Eliminating Hot Spots: Without a Polarizer
Without Polarizer
Eliminating Hot Spots: Polarizers over Light Source and Lens
Polarizers over Light Source and Lens

Glare From a Plane Surface: Glare from highly reflective surfaces or optical windows is removed by putting a polarizer over the lens. Due to partial polarization of light, the light source may or may not require a polarizing filter in this scenario.

Glare From a Plane Surface: Without Polarizer
Without Polarizer
Glare From a Plane Surface: Polarizer over Light Source or Lens
Polarizer over Light Source or Lens

Contrast Enhancement: Ring light guides are popular for their even, diffuse illumination. However, glare or reflection of the ring itself may occur. Polarizing the ring output and the lens separately can reduce these effects, and bring out surface details.

Contrast Enhancement Without Polarizer
Without Polarizer
Contrast Enhancement: Polarizers over Ring Light and Lens
Polarizers over Ring Light and Lens

Stress Evaluation: Stress, or unwanted refractive index variations, causes a rotation in the angle of polarization. Viewing an unstressed clear object between crossed polarizers should yield a completely dark field. However, when stress is present, the localized changes in refractive index actually rotate the angle of polarization to give varying degrees of transmission - even different amounts of transmission for different colors.

Stress Evaluation: Without Polarizer
Without Polarizer
Stress Evaluation: Polarizers Before and After Transparent Object
Polarizers Before and After Transparent Object
본 콘텐츠가 도움이 되었습니까?


Linear polarization을 처음 접하시나요? Polarization 용어, 기본적인 관계, 편광 상태, 그리고 polarizer 종류를 검토합니다.

Need to alter or select a specific light polarization state? Check out our selection of dichroic, crystalline, or wire grid polarizers to get started.

UV, 가시광, 백색광 및 IR 파장의 LED, 광섬유, 형광 조명 기술 제공

많은 사람들이 이미징 시스템에서 적절한 조명이 갖는 힘을 과소평가합니다. 올바른 조명 선택이 어떻게 모든 차이를 만들 수 있는지 설명해 드리겠습니다. 

Edmund Optics에 연락할 일이 있으신가요? 여러분의 필요에 맞는 당사의 빠르고 친절한 서비스를 이용하십시오.

영업 & 기술 지원
혹은 지사별 연락처 확인
사용이 간편한
견적 도구
재고번호 입력 후 바로 시작