| Object-Space Telecentric Lens | Chief rays are parallel in object space, so the measured image size changes very little when the object moves along the optical axis. | Low perspective error, stable dimensional measurement, and reduced sensitivity to object-height variation. | Requires sufficient working distance and a large entrance pupil; usually larger and more expensive than standard lenses. | Precision inspection of molded parts, machined components, connectors, wafers, and dimensional features. | Choose this type when object-side dimensional accuracy and repeatability are the primary requirements. |
| Image-Space Telecentric Lens | Chief rays are parallel in image space, allowing the sensor to receive rays with nearly constant angular geometry. | Useful for controlling image-side magnification behavior and maintaining consistent illumination or sensor coupling in specialized systems. | Does not by itself eliminate object-side perspective error; system performance depends strongly on the object-side optical design. | Specialized imaging systems, sensor-side optical alignment, and applications requiring controlled image-space ray geometry. | Consider it when the detector-side geometry is critical, rather than selecting it solely for ordinary dimensional measurement. |
| Bi-Telecentric Lens | Chief rays are telecentric in both object space and image space. | Very low perspective distortion, high dimensional stability, and reduced sensitivity to object and sensor position changes. | Typically has a large optical envelope, limited field of view for a given package size, and higher cost. | High-accuracy metrology, gauging, semiconductor inspection, and critical machine-vision measurement. | Use it when both object-side measurement stability and image-side alignment tolerance are important. |
| Fixed-Magnification Telecentric Lens | The lens is optimized for one nominal magnification and a defined working distance or object range. | Usually provides better measurement consistency, resolution, and distortion control than a variable-magnification solution. | Less flexible when the part size or inspection format changes. | Repeatable production lines with a known part size and stable inspection geometry. | Select the magnification from the required field of view and sensor size, then verify the usable object-space range. |
| Zoom or Variable-Magnification Telecentric Lens | Magnification can be adjusted over a specified range while maintaining telecentric behavior within the lens design limits. | Supports multiple part sizes and reduces the need to change lenses between inspection tasks. | Often has a narrower performance envelope, more complex setup, and potentially lower consistency than a dedicated fixed lens. | Flexible inspection cells, laboratory systems, and production lines handling several component formats. | Confirm telecentricity, distortion, resolution, and working-distance specifications at every intended zoom setting. |
| Required Field of View | The visible object-space area must contain the complete part, feature, or measurement region. | A correctly sized field of view prevents cropping and supports efficient single-image inspection. | A field of view that is too large reduces the number of pixels available per feature and can lower measurement resolution. | Any application where the full component or target feature must be captured in one image. | Define the required field of view first; allow practical clearance around the part without adding unnecessary area. |
| Magnification and Sensor Matching | Magnification determines how object dimensions map to sensor pixels and affects the achievable sampling resolution. | Proper matching improves feature visibility and helps use the sensor area efficiently. | Excessive magnification may crop the part; insufficient magnification may leave too few pixels across a critical feature. | Dimensional gauging, edge detection, defect inspection, and optical measurement. | Use the relationship: magnification ≈ sensor dimension ÷ required field-of-view dimension. |
| Working Distance | Working distance is the nominal distance from the lens reference position to the object plane at focus. | Adequate distance allows room for lighting, fixtures, protective windows, and moving parts. | Longer working distance can increase lens size and reduce available numerical aperture or resolution for a given design. | Robotic inspection, enclosed machinery, hot or delicate parts, and systems requiring coaxial lighting. | Choose a working distance that clears the mechanics while remaining within the lens specification. |
| Resolution and Numerical Aperture | Resolution describes the smallest distinguishable detail; numerical aperture influences light collection and diffraction-limited performance. | Higher optical performance can reveal small edges, gaps, scratches, and dimensional features. | Higher resolution may reduce depth of field and increase sensitivity to focus, vibration, and lighting quality. | Fine-feature inspection, precision gauging, and applications with strict minimum-feature requirements. | Verify lens resolution against sensor pixel size and the smallest feature that must be measured or detected. |
| Depth of Field | Depth of field is the object-space range over which features remain acceptably sharp for the intended measurement or inspection task. | A suitable depth of field accommodates part-height variation and improves production robustness. | Increasing depth of field may require more illumination or a smaller aperture, which can affect image brightness and resolution. | Uneven parts, assemblies with height variation, and automated lines with imperfect fixturing. | Compare the specified depth of field with the actual height variation, not just the nominal working distance. |
| Distortion and Measurement Accuracy | Distortion changes the relationship between object position and image position; telecentric designs are intended to minimize perspective-related errors. | Improves dimensional repeatability across the field when calibration, focus, and lighting are properly controlled. | Low lens distortion does not guarantee total system accuracy; sensor calibration, mechanics, temperature, and algorithms also matter. | Dimensional inspection, profile measurement, and pass/fail gauging. | Review distortion maps or accuracy data across the entire field of view at the required working conditions. |
| Lighting Compatibility | Telecentric systems commonly work with backlights, coaxial lights, ring lights, or telecentric illuminators depending on the feature being inspected. | Correct lighting can create clean silhouettes and high-contrast edges for reliable measurement. | Poor illumination can dominate system error even when the lens has excellent optical specifications. | Silhouette gauging, surface inspection, printed-feature inspection, and component alignment. | Select the lens and light together; verify clearance, aperture compatibility, uniformity, and glare control. |
| Camera and Interface Compatibility | The lens image circle, mount, sensor format, back focal distance, and mechanical interface must match the camera system. | Correct matching avoids vignetting, mechanical interference, focus limitations, and unused sensor area. | A mismatch can reduce the effective field of view or prevent the lens from reaching its specified performance. | Area-scan and line-scan machine-vision systems, depending on the lens design. | Check sensor dimensions, pixel pitch, mount standard, image circle, and available mechanical space before purchase. |
| Budget, Size, and Integration | Telecentric performance generally requires additional optics and a larger entrance pupil compared with conventional lenses. | The investment can be justified when measurement stability and reduced rejection risk are important. | Higher cost, weight, and installation space may affect camera brackets, stages, enclosures, and cycle-time design. | Production equipment where optical repeatability is more important than minimum package size. | Compare total system cost, including lighting, mounting, calibration, protection, and maintenance—not lens price alone. |
