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Scan Lens

Features

• Constant Magnification Over Entire Field of View (FOV)
• Constant Spot Size
• Flat Image Plane
• Excellent Coupling Efficiency
• Large Field of View

These scan lenses are telecentric objectives that are ideal for use in laser scanning applications like Optical Coherence Tomography (OCT). Telecentric objectives are used in OCT and other laser imaging systems because of the advantages of a flat imaging plane when used in applications that scan the laser across the sample being imaged. A flat imaging plane minimizes image distortion, which in turn allows for the creation of geometrically correct images without the need for extensive post image processing. A telecentric scan lens also maximizes the coupling of the light scattered or emitted from the sample (the signal) into the detection system. In addition, the spot size in the image plane is nearly constant over the entire FOV so that resolution of the image is constant.

This type of objective lens is usually called a scan lens because a laser beam is scanned across the back aperture of the objective lens in order to form the image of the sample. Each position that the laser is scanned over corresponds to one point in the image formed. This approach results in a focal spot on the sample that is not, in general, coincident with the optical axis of the scan lens. In traditional lenses, this would result in the introduction of severe aberrations that would significantly degrade quality of the resulting image. However the scan lenses were designed to create a uniform spot size and optical path length for the laser for every scan position, which allows a uniform, high-quality, image of the sample to be formed.

* Scanning Distance (SD): Distance between the galvo mirror pivot point and the back mounting plate of the objective. The galvo mirror pivot point is located at the back focal plane of the objective in order to maximize image resolution.

* Pupil Size (EP): The size of the EP determines the ideal 1/e2 collimated beam diameter that should be used for the beam of light used to image the sample in order to maximize the resolution of the imaging system.

* Working Distance (WD or LWD): The distance between the tip of the scan lens housing and the front focal plane of the scan lens is defined as the WD.

* Depth of View (DOV): The DOV parameter reported for these scan lenses corresponds to the distance between the front focal plane and a parallel plane where the beam spot area has increased by a factor of 2.

* Field of View (FOV): The FOV is the maximum size of the area on the sample that can be imaged with a resolution equal to or better than the stated resolution of these scan lenses. In order to meet this specification the imaging system must be designed to properly utilize these scan lenses in the system.

* Parafocal Distance (PD): The PD is the distance from the scan lens mounting plane to the front focal plane of these scan lenses.

* Curvature (C): The curvature is the maximum distance between the front focal surface and an ideal plane.

* Scan Angle: The maximum allowed angle (in the X or Y direction) between the beam and the optical axis of an scan lens after being reflected off of the galvo mirror.