Glossary

○Resolution(μm)

Resolution is a measure of how closely spaced two points may be before they cannot be distinguished.For example, 1μm resolution means that two points that are 1μm away from each other can be distinguished. Resolution values in this catalog are lenses' theoretical resolutions. The following is a formula to calculate theoretical resolution based on an aplanatic lens's ray diffraction. (Rayleigh formula)　Wavelength＝0.61×λ／NA

○Resolving power(line/mm)

Resolving power indicates the number of black and white lines distinguished within 1mm in an image through a black and white grid-like chart lens. It is expressed by line/mm.
For example, 100 line/mm means that black and white pitch 1/100mm(10μ) can be distinguished. The width of both the black and white lines is 1/200mm(5μ).

○Horizontal TV resolution

The total number of black and white horizontal stripes on a TV monitor screen. It is expressed in TV lines.
For example, 200TV lines of horizontal TV resolution means that 100 white horizontal lines is counted as one line. However, for TV lines, one pair is counted as 2 TV lines. For example, if a 1/2-inch CCD camera is used with a lens of 50 lines/mm resolving power, horizontal TV resolution on a TV monitor screen is calculated as follows; 50×6.4(CCD width)×2=640TV

○Distortion

Optical distortion
Lens's aberration where a straight object outside of the optical axis appears curved.

TV distortion
Image distortion on a TV monitor. The closer to zero, the better the performance.

○Aperture efficiency/Marginal light quantity (%)

Aperture efficiency indicates the brightness difference between the optical axis of the image formation plane and its surrounding area when an evenly bright object is captured with a lens. It is expressed by percent(%) assuming that the center brightness is 100. It is one of a lens's optical characteristics.

○Shading (%)

Shading is the brightness difference between TV monitor's center and its edges when an evenly bright object is captured with a lens and CCD-TV camera. Shading indicates comprehensive performance of a lens and TV camera.

○Chromatic aberration

In lenses' optional systems, positions where images are formed and image magnification differ according to light's wavelength. Rays with different wavelengths have different colors. This is called chromatic aberration. Aberration on the optical axis is called chromatic aberration on the axis and magnification difference is called magnification chromatic aberration.

○FNO

The value indicates a lens's brightness. It is calculated by dividing the lens's focal length by the lens's effective diameter(entrance pupil D mm) looking from object side. It can be also calculated by NA and lens's optical magnification( ). The smaller the number, the brighter the lens is. FNO=f/D

○Effective FNO

The value indicates a lens's brightness. It is calculated by dividing the lens's focal length by the lens's effective diameter(entrance pupil D mm) looking from object side. It can be also calculated by NA and Lens's optical magnification(). The smaller the number, the brighter the lens is.　Effective FNO=(1+M)xFNO

○Numerical aperture

The higher the NA, the greater the resolution and brightness are.
When the half angle that an image makes on exit pupil is u' and refractive index is n', n' xsin u' is called image side numberical aperture, NA'.
NAs in this catalog indicate object side numerical apertures.

○MTF

It provides a graph analyzing a lens’ ability to resolve sharp details in very fine sets of parallel lines, and a lens’ contrast or ability to provide a sharp transfer between light and dark areas in sets of thicker parallel lines.

○Depth of field

Images through lenses theoretically form as points. Acceptable blur on an acceptably clear image is called the permissible circle of confusion.
Depth is the distance between the nearest and farthest points that appear in acceptably sharp focus when an object is shifted back and force from the best focal point. Depth range of the object side is called depth of field.
Depth of field=2(permissible circle of confusion×effective FNO/magnification2)

○Depth of focus

Depth is the distance between the nearest and farthest points that appear in acceptably sharp forcus when a CCD is shifted back and force from the best focal point. Depth range of the image side is called depth of focus.

○Angle of view

The angle formed by imaginary lines connecting the lens second principal point with both ends of the image diagonal. Angle of view is directly associated with lens focal length. As the focal length is longer, the angle of view is narrower.
Angle of view＝2xtanー1D（Image size）／2 f（Focal length）

○WD

Distance from the front end of a lens system to the object under inspection.

○OI

Distance from the object to the image sensor.

○Focal length

Focal length is the distance from the optical system's principle point to the focal point. Distance from the vertex of the last lens to the back focal point is called back length. Distance from the vertex of the first lens to the front focal point is called front focal length.

○Image size

The diameter of the sharp image circle formed by a lens. Area sensor is expressed by inch, and diameter of image circle is equal to diagonal of sensor. Image circle of diameter for line sensor is equal to the maximum sensor size. It is expressed by pixel size x resolution.

■Lamp

○Xenon Lamp

A point source arc lamp filled with high pressure Xenon gas. Xenon arc lamps have no filament. The arc is formed by electric current flowing through the Xenon gas between two tungsten electrodes. Used mainly in motion picture and slide projectors and follow spotlights for medium and high intensity.

○Metal halide lamp

A high-intensity discharge light source in which the light is produced by the radiation from mercury, plus halides of metals such as sodium, scandium, indium and dysprosium.

○Halogen lamp

A halogen lamp is an incandescent lamp with a filament that is surrounded by halogen gases, such as iodine or bromine. The halogen participates in a tungsten transport cycle, returning tungsten to the filament and prolonging lamp life. It is more stable and longer life time, compared to xenon and metal halide lamp.

■Fiber

○Optical Fiber

Optical fiber consists of two fields: the core that light goes through and the clad that surrounds the core. Material is plastic, multi-component glass, and quartz glass.

○Numerical aperture NA

Numerical aperture NA: The light - gathering ability of a fiber, the maximum angle to the fiber axis at which light will be accepted and propagated through the fiber. It is calculated by refractive index of core and clad that compose optical fiber.

○Lighting-receiving angle

An angle that optical fiber can receive rays

■LED

○LED element

Stands for light emitting diode. Semiconductor element that emits the light by the flow of current.
Features of Led are small dimension, low power consumption, and long life, compared to other light sources. Wave length can be chosen from UV to IR.

■Luminous quantity

○Beam (lm)

Indicates light quantity outputted from light source. It is expressed by lm (lumen).

○Luminous intensity

Light quantity outputted from a light source is indicated the amount of beam per unit solid angle. It is expressed by cd(candela) = lm/sr (solid angle).

○Brightness

Luminous intensity of a light source per unit area. It is expressed by nit = cd/m2 or stilb=cd/cm2

○Luminosity

Object's surface brightness when light outputted from a light source illuminates it. It is expressed by lx (lux) = lm/m2.m2 indicates the object's surface area.