Views: 0 Author: Site Editor Publish Time: 2026-08-31 Origin: Site
An endoscope camera can show curved edges, dark corners or uneven brightness for very different reasons. Calling all of these effects ‘lens distortion’ makes it difficult to decide whether the camera head is unsuitable, the field of view is intentionally wide, the LEDs are not illuminating the target evenly, or the probe structure is blocking part of the image.
The useful question is not whether the image looks perfectly flat on its own. It is whether the complete probe gives the device enough coverage, usable detail and stable illumination at the actual working distance.
· Barrel distortion makes straight features near the boundary bow outward. It is more common in very wide-angle optics, but a wide FOV does not prove that the lens has a fixed amount or sign of distortion.
· Pincushion distortion makes boundary lines bend inward. It may occur in some longer-focus optical designs, but endoscope-lens behavior still depends on the complete optical structure.
· A fisheye-like view may be an intentional projection that captures more of a cavity, pipe wall or surrounding structure. It should be judged against the observation task, not automatically treated as a defect.
· Dark corners may be optical or mechanical vignetting, but they may also come from uneven LED illumination, a cover window or steel shell entering the light path, contamination, or the target geometry itself.
Under a common TV-distortion convention, barrel distortion is normally negative and pincushion distortion positive. Because some software reports calibration or correction coefficients differently, endoscope specifications should state the formula and test conditions rather than rely on ‘positive’ or ‘negative’ alone.
A wide or fisheye-style view can help an operator see side walls and surrounding structures without moving the probe as much. The trade-off is that objects may occupy fewer pixels, edge shapes may be strongly compressed, and measurements taken near the boundary may be unreliable without calibration or dewarping.
A narrower view can place more pixels on a small feature at the same output resolution, but it may miss nearby walls or make navigation more difficult. FOV therefore needs to be evaluated together with focus distance, depth of field, viewing direction and the target size—not selected as the largest available number.
Device task | What matters most | Main image risk |
Pipe or borescope inspection | Wall coverage, orientation and navigation | Wide edge curvature can affect shape judgment; LEDs may create uneven reflection |
Dental or oral imaging device | Useful detail at a short, defined distance | Excessive FOV can reduce target size; wet or reflective surfaces change illumination |
Medical or veterinary device development | Device-specific viewing, illumination and validation targets | Image acceptance must be verified at complete-device level |
Confined-space industrial inspection | Feature visibility through the final probe and window | Shell or window may cause corner cut-off after assembly |
Miniature endoscope optics operate inside a tight tolerance stack. Lens diameter, sensor size, lens-to-window distance, steel-shell opening, LED position, sealing structure and assembly alignment can all change the final view. A lens that looks acceptable before installation may develop corner shading or partial obstruction after it is placed inside the final probe.
Evaluation should use the intended probe diameter and viewing direction, the final cover window or shell, the planned number and position of LEDs, and the actual cable structure. It should also include the required working distance, target material, moisture or sealing condition, and the lowest practical illumination level. Lens-shading correction may compensate for gradual brightness fall-off, but it cannot restore content hidden by a mechanical opening or correct an unsuitable lighting layout.
A useful endoscope-camera request should include the device type, maximum camera-head diameter, straight or side-view direction, target working distance, required FOV, minimum visible feature size, LED and dimming requirement, cable length and flexibility, output interface, protection requirement and whether image correction is available on the host.
With these conditions, barrel distortion, fisheye projection and vignetting can be judged as device-level trade-offs. The goal is not the lowest possible distortion value in isolation, but a camera head that fits the probe and provides a view the device can actually use.
