Thermal current produced in an operating photodetector device when no optical radiation impinges on the detector.
See also Threshold Current
현미경 용도에서 렌즈와 직각을 이루는 가장자리를 통해 반투명한 피사체로 들어오는 빛을 말합니다. 머신 비전 용도의 조명 형태에서는 대부분의 빛이 피사체를 투과하지 못합니다. 이로 인해 가장자리와 결함이 있는 표면 쪽에 위치한 빛은 detector 방향으로 분산이 일어나, 고대비 고휘도의 스팟이 발생하게 됩니다.
A logarithmic measure of relative power levels. It is used to specify the amount of attenuation in optical fibers.
Depth of Field (DOF)
특정 spatial frequency 혹은 resolution에서 수용 가능한 수준의 contrast는 유지하면서, 이미지 처리되는 피사체가 best focus plane 내외로 이동하는 거리.
Depth of Focus (초점 심도)
Depth of field와 동일한 이미지 공간. 피사체가 일정한 거리에 있는 경우, best focus plane에서 최대 위치 이동 시 특정 spatial frequency에서도 이미지는 각각의 contrast를 유지합니다.
Design Wavelength (DWL)
A common specification for optical components describing the specific wavelength of light at which the components are intended to be used, or the wavelength of light used in specifying or testing an optical component for a wavelength dependent specification such as reflectivity or transmission. Optical components used over a range of wavelengths will typically have optimal performance at the DWL and decreasing performance as the wavelength moves further away from the design wavelength. DWL has units of length and is most commonly reported in nanometers (nm) or microns (μm).
See also: Wavelength.
A measure of the detecting ability or sensitivity of a photodiode. The reciprocal of noise equivalent power (NEP).
A type of plate beamsplitter that splits incident light based on wavelength.
Dichroic Coating (이색성 코팅)
A filter or mirror coating that transmits or reflects light depending on wavelength rather than polarization. The color varies with angle of incidence and thickness of deposition material. Metallic coatings tend to be more spectrally flat.
A type of filter coated with thinfilms to achieve a desired transmission and reflection percentage across a given spectrum. It is often used as a color filter (both additive and subtractive). A dichroic filter is slightly angle sensitive but is much more forgiving than an interference filter.
See also Filter
A type of coating consisting of materials that are electrical insulators. The reflective coatings consist of alternating layers of higher and lower index materials (compared to the substrate) in order to achieve a certain reflectivity over a certain wavelength region.
파동(wave)이 장애물을 만날 경우, 간섭(interference)의 생성 여부에 의해 intensity distribution에 생기는 변화로서 입사 웨이브 프런트와는 다른 distribution을 만들어 냅니다.
See also Diffraction Grating
An optical component used to disperse light into its individual wavelengths. As incident light strikes a transmission grating's groove spacing, it is dispersed on the opposite side of the grating at a fixed angle. As incident light strikes a reflective grating's groove spacing, it is reflected and dispersed on the same side of the grating at a fixed angle.
Diffraction Limit (회절 제한)
광학 혹은 이미징 시스템에서 확보할 수 있는 resolution의 최대치를 결정짓는 이론적 제한 요인이며, 렌즈의 F/# 값을 곱한 광파장의 역(inverse)으로 계산됩니다.
See also Modulation Transfer Function (MTF)
대형 광원에서 비롯된 빛으로서 확산성을 띄나 공간적으로 균일성을 갖습니다. 피사체의 균일한 조도를 위해 사용됨.
The effect of light scattering over a large solid angle. Light is diffused by reflecting from or transmitting through an irregular (rough) surface. Typically, precautions are taken to remove diffusion in applications; however, diffusers can be utilized to introduce a specific amount of diffusion in order to create a desired effect (i.e. minimizing glare, homogenating a beam, removing speckle in a laser application, etc).
A signal that changes in regular steps. The signal level at each step is represented by a number.
Digital Signal Processing (DSP)
Found often in high-end industrial cameras, it involves analog-to-digital conversion of all or part of a standard video signal to enhance/change the resulting signal recovered upon digital-to-analog conversion. Enhancements usually pertain to RGB balancing for more accurate color reproduction.
DIN (Deutsche Industrie Norm)
현미경의 대물렌즈와 접안렌즈 설계를 위한 산업 표준 규격. DIN 표준 현미경은 160mm의 튜브 길이를 갖습니다.
Unit of optical measurement of a lens that equals the inverse of the focal length of the lens in meters.
단일 혹은 다중 광원의 점광원(point source) 조명
A measure of how much the index of refraction of a material changes with respect to wavelength. It also determines the separation of wavelengths known as chromatic aberration. Quantitatively, dispersion is inversely given by the Abbe number.
Nonlinear geometrical aberration in which magnification changes with field height (i.e. no distortion at center), defined at maximum field. If imaging a square grid, positive distortion gives a pincushion effect while negative distortion yields a barrel effect.
이미지 전반의 징후 및 규모를 변화시키는 왜곡으로서 wave 혹은 mustache distortion으로도 불립니다.
A term that describes the degree to which a light source expands as the distance from the laser increases. Divergence is generally specified as a full angle and can be used to predict spot sizes at a given distance through tangent calculation. Beam divergence can be reduced for long distance uses by expanding the diameter of the beam.
Double Gauss Design
An imaging lens design that employs low f/# imaging lenses that provide superior overall correction and produce less distortion than standard fixed focal length lenses. However, this design can be subject to residual oblique spherical aberration. Two Gauss lenses, each comprised of a negative doublet and a positive singlet, are situated symmetrically in the design. Double Gauss lenses are commonly used in machine vision applications.
Double-Concave (DCV) Lens
A type of singlet lens with two inward, equally curved surfaces and a negative focal length. Optimized for infinite/ infinite conjugates and ideal for image reduction and to spread light.
Double-Convex (DCX) Lens
A type of singlet lens with two outward, equally curved surfaces and a positive focal length. Optimized for finite/ finite conjugate imaging and ideal for electronic imaging, relay systems and image projection.
Also known as a doubler, an imaging lens adapter that consists of a negative focal length achromatic lens that doubles the magnification for a specified working distance by giving half the field of view.
A lens with two optical components such as an achromatic lens.
A type of prism that inverts an image by rotating it by twice the prism rotation angle. It is available in two versions: uncoated and coated. An uncoated dove prism is used for image rotation. A coated dove prism retroreflects an image.
See also Retroreflector
In motorized stages, the ratio of motor revolutions per leadscrew revolution.
빛을 감지할 수 있는 가장 높은 레벨과 가장 낮은 레벨의 차이. 이러한 차이는 개별 픽셀의 saturation capacity, dark current 혹은 dark noise, ADC circuit 및 gain 설정에 의해 물리학적으로 측정됩니다.