These parameters of industrial lenses are interrelated and constrained each other, in the actual selection and application, it is necessary to take into account the specific needs of industrial production, environmental conditions, cost budgets and other factors, and carefully select the appropriate lens, in order to build a highly efficient and accurate industrial vision system!

Focal Length

1、Definition: The focal length is the distance from the optical center of the lens to the imaging plane, usually measured in millimeters (mm). It determines the magnification of the object and the range of viewing angles of the lens.

2、Impact:

① Short focal length lenses (such as wide-angle lenses, focal length is generally less than 35mm) have a larger angle of view, can capture a wider scene, but the relative size of the object in the image is smaller, suitable for monitoring large areas of production lines, warehouses and other scenes, can capture multiple target objects at once.

② Long focal length lens (such as telescope head, focal length greater than 70mm) narrower angle of view, can be drawn closer to the distant objects and magnified, so that the target object occupies a larger proportion of the image, often used for small or long-distance objects for high-precision detection, measurement, such as electronic chip pin detection, long-distance identification of defects in the workpiece.

③ Medium focal length lens (35mm - 70mm) in the angle of view and magnification to achieve a certain balance between the generality of relatively strong, suitable for a variety of conventional industrial inspection tasks.

Aperture
 

1、Definition: The aperture is the device inside the lens that controls the amount of light passing through it, usually expressed in terms of F, which is calculated as F = focal length of the lens ÷ diameter of the aperture. For example, F2.8 means that the aperture is relatively large, allowing more light to pass through; F16 is a smaller aperture, allowing less light to pass through.

2、Impact:

① The size of the aperture directly affects the brightness of the image. In low-light industrial environments, such as outdoor equipment inspections at night and indoor precision assembly shops with low light, a larger aperture (smaller F value) is needed to increase the amount of incoming light to ensure that the image is clear and bright, and to avoid the increase in image noise and loss of detail due to insufficient light.

② Aperture also affects the depth of field. Depth of field refers to the imaging plane, can maintain a clear image of the front and back of the object range of distance. Large aperture (small F value) when the depth of field is shallow, only the focus plane near the object is clear, the background and foreground blurring is obvious, this feature can be used to highlight the main details of the object being detected, such as a specific chip on the circuit board to detect the macro photography; small aperture (large F value) is a greater depth of field, can be made from the nearer to the farther a range of objects are relatively clear for the need for the need to see before and after the scene of different distances from the object Smaller apertures (larger F-values) have a greater depth of field, making objects from nearer to farther away relatively clear, which is suitable for scenes where objects at different distances from the front and back need to be seen at the same time, such as the overall appearance of multi-layer stacked products.

Field of View，FOV

1、Definition: Field of view is the range of angles, usually in degrees (°), that a lens can cover horizontally or vertically. It is closely related to the focal length of the lens and the size of the imaging sensor.

2、Impact:

① For a given imaging sensor size, the shorter the focal length, the larger the field of view; the longer the focal length, the smaller the field of view. When designing an industrial vision system, it is necessary to select a lens with a suitable field of view according to the size of the object to be detected and the working distance (the distance from the lens to the object). For example, to detect the paint quality on the surface of a large automobile body, a wide-angle lens is required to provide a large field of view to ensure that most of the body can be covered in a single shot; while for the detection of tiny parts inside a watch, a telephoto lens with a narrow field of view can focus on the details of the parts to meet the demand for high-precision detection.

② Different shapes of sensors (such as rectangular, square), the horizontal field of view and vertical field of view is calculated slightly differently, need to take into account the specifications of the sensor and the actual requirements of the inspection, to ensure that the lens field of view angle and the target object to ensure that the lens field of view angle and the target object, to avoid the emergence of the edge of the image of the part of the object is missing or deformation of the situation.

Resolution

1、Definition: The resolution of a lens refers to its ability to resolve details of an object, usually measured in line pairs per millimeter (lp/mm). It reflects how well a lens reproduces minute details in the imaging process.

2、Impact:

① High-resolution lenses are able to capture finer object features, such as tiny scratches on the surface of electronic products and fine textures on precision mechanical parts, which are critical for high-precision industrial inspection. In industries such as semiconductor chip manufacturing and high-end medical device production, the requirements for lens resolution are extremely high, as even extremely small defects can lead to product failure.

② The lens resolution needs to match the resolution of the imaging sensor. If the lens resolution is too low, even if the sensor performance is excellent, it will not be able to give full play to its ability to capture details; conversely, if the lens resolution is too high and the sensor can not keep up, it will also result in a waste of resources, and may introduce unwanted noise, affecting the image quality. In general, the two should be synergistically optimized to achieve the best imaging results.

Depth of Field，DOF

1、Definition: As mentioned earlier, depth of field is the range of distances before and after the subject to obtain a clear image on the image plane. It is affected by a combination of factors such as the focal length of the lens, the size of the aperture, and the object distance.

2、Influence:

① In industrial inspection, reasonable control of the depth of field is very critical. For example, when measuring the size of mechanical parts with a certain thickness, if the depth of field is insufficient, it may lead to blurring of some areas on the front and back surfaces of the parts, and inaccurate measurement data; and for the detection of welded joints on multilayered circuit boards, the appropriate depth of field ensures that welded joints on different layers are clearly imaged, which facilitates the rapid discovery of defects such as false welds and leaks.

② By adjusting parameters such as focal length, aperture and object distance, the depth of field can be enlarged or reduced according to actual needs. When it is necessary to highlight the details of objects in a particular plane, a shallow depth of field is utilized; if it is necessary to take into account the clarity of objects in different depths within a certain range, a large depth of field is utilized, which provides a flexible imaging solution for diversified inspection tasks in complex industrial scenarios.

Working Distance，WD

1、Definition: The working distance is the distance from the front of the lens to the surface of the object to be detected. It is one of the parameters to focus on when actually installing and using the lens.

2、Impact:

① Different industrial inspection scenarios have different requirements for working distance. In the automated assembly line, due to the limitations of the space layout and production rhythm, the lens may be required to work at a certain distance to avoid interference with the normal operation of the production line, but also to ensure that the product is clearly imaged, at this time it is necessary to choose the appropriate focal length and working distance to meet the conditions of the lens, such as the conveyor belt on the high-speed movement of bottled beverages labeling inspection.

② For some high temperature, high pressure, strong radiation or chemical contamination risk of special industrial environments, such as iron and steel smelting plant, nuclear facilities detection area, often require the lens working distance as far as possible, in order to protect the lens from damage to the harsh environment, and at the same time, through the remote imaging to achieve the monitoring and analysis of the target object. On the contrary, in the microscopic detection of small objects, such as biological cell observation, nano-materials research, the working distance is usually closer, need to rely on specialized close-up lenses or macro lenses to meet the short working distance under the high magnification imaging needs.

Distortion

1、Definition: Aberration refers to the deviation in shape between the image and the actual object due to the design of the optical system of the lens, manufacturing defects or light propagation characteristics. Common types of aberrations are barrel and pincushion aberrations.

2、Impact:

① In industrial vision inspection, aberrations can seriously affect measurement accuracy. For example, for the size measurement of precision mechanical parts, if the image has aberrations, the length, angle and other data obtained from the measurement will have a large deviation from the actual value, which may lead to the product being misjudged as qualified even though it is unqualified, causing quality problems. For vision-guided robot gripping operations, distorted images may make the robot inaccurate positioning and unable to accurately grasp the target object.

② In order to reduce the impact of aberrations, on the one hand, we can choose lenses with good optical performance and strong aberration correction ability; on the other hand, in the image post-processing, the aberrations can be corrected by algorithms to restore the real shape of the object, but this requires a certain amount of computational resources and time costs, which need to be weighed carefully in the industrial scenarios with high real-time requirements.

Magnification

1、Definition: Magnification is the ratio of the size of the object imaged by the lens to the size of the actual object. It intuitively reflects the magnification effect of the lens on the object, usually used for macro photography or detection of tiny objects scene.

2、Impact: In electronic manufacturing, biomedical and other fields, it is often necessary to observe, detect and operate on tiny objects. For example, in the semiconductor chip packaging process, the fine welding quality inspection of the chip pins, high magnification lens can zoom in on the tiny solder joints, clearly presenting welding defects, such as false soldering, bridging, etc., to help workers find the problem in a timely manner and rework; in the cell culture experiments, scientific researchers use high magnification lenses to observe the cellular morphology, structural changes, to provide a microscopic basis for medical research. Different magnification lenses are suitable for different scales of tiny objects detection tasks, reasonable choice can improve detection efficiency and accuracy.