Endoscope Measurements Services

Endoscope Measurements Services by Lighthouse Imaging

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The following endoscope measurements are available:

Modulation Transfer Function: Studies have shown that a user’s perception of image quality correlates to a large value of MTF at a low spatial frequency of the image. MTF testing measures the low frequency square wave modulation transfer function of the endoscope on axis and at the edge of the real field of view in the four quadrants. Measurements are conducted at an average spatial frequency of 6 cycles/degree (distortion of the endoscope is usually not considered).

Vignetting: Vignetting is defined as the ratio of the central transmission with the transmission at the edge of the apparent field of view. Large values of vignetting are particularly objectionable with video-endoscopes and in severe cases lead to “white-out” where the central image area is saturated when the light source is adjusted for adequate edge illumination.

Apparent Field of View/Alignment: Apparent field of view is defined as the angle between the right and left sides of the field stop as subtended by the eye. Apparent field of view (together with camera coupler lens focal length) controls the size of the image circle on a video monitor. Alignment of apparent field of view is the percent movement of the field stop as the endoscope is rotated in the camera coupler. This defect is caused by a lack of perpendicularity between the eyecup mounting plane and the optical axis of the endoscope.

Image Transmission: Image transmission is defined as the ratio of the central optical transmission with the central optical transmission of a master reference endoscope or internal calibration standard.

Coloration: Coloration is quantified by the ratios of central transmission of blue/green and red/green illumination. This is most often seen as a yellowish tint to the image.

Real Field of View: Real field of view is the actual angular extent of an object visible through the endoscope as subtended by the tip (entrance pupil) of the endoscope.

Distortion: Distortion is the percent change in magnification between the center of the field of view and the right and left off-axis positions at the edge of the real field of view.

Fiber-optic Illumination Distribution: Fiberoptic illumination distribution measures the percent decrease in illumination from the center of the field of view to the edge of the apparent field of view. Fiberoptic transmission is defined as the ratio of the peak fiberoptic transmission (along the direction of view) with the peak fiberoptic transmission of a master reference endoscope or internal calibration standard.