IV. Issue 4: Image blurriness during dynamic detection (the object on the production line exhibits a “smear” effect)

In high-speed inline inspection applications such as new‑energy battery electrode sheets and smartphone screens, objects move at speeds of 1 to 3 meters per second. If the images exhibit motion blur, defect edges become indistinct, and dimensional measurement errors exceed 0.1 mm, rendering the system incapable of reliable detection.

1. 3 A common reason

• Core Reason 1: Strobe function is not enabled.

When the light source is continuously on, objects in motion continuously reflect light, and during the camera’s exposure period, their movement results in image trailing. In contrast, a strobe light can illuminate only at the instant of the camera’s exposure, effectively “freezing” the object’s motion and eliminating trailing artifacts.

• Core Reason 2: The flicker frequency does not match the camera’s frame rate.

When the strobe frequency is too high or too low, “sync failure” can occur—for example, with a camera frame rate of 30 fps and a strobe frequency of 25 Hz, some frames may appear underexposed, while others exhibit motion blur.

• Core Cause 3: Vibration of the Light Source Bracket

Vibrations generated during conveyor‑belt operation cause the light source to shift, resulting in unstable illumination angles and blurred images in some frames due to light‑source misalignment.

2. Step-by-step solution

• Step 1: Activate strobe mode and match the frequency.

In the light source controller, enable “Strobe Mode” and set the strobe frequency to “Camera Frame Rate + 2” (to allow for a margin and avoid synchronization errors): for example, if the camera frame rate is 30 fps, set the strobe frequency to 32 Hz; if the camera frame rate is 60 fps, set the strobe frequency to 62 Hz. If possible, use “External Trigger Synchronization”—let the camera’s trigger signal synchronize with the strobe control—to ensure that the light source illuminates precisely at the start of each exposure.

• Step 2: Reinforce the light source bracket.

Select a metal‑material light source bracket and secure it to the assembly line frame with screws (rather than using a plastic bracket or temporary fasteners). If vibration is significant, install vibration‑damping pads—such as rubber pads—between the bracket and the frame to reduce vibration transmission. For example, on an automotive parts assembly line, fixing the light source with a stainless steel bracket and adding a 5 mm‑thick rubber vibration‑damping pad completely eliminates blur caused by vibration.

• Step 3: Increase the light source brightness to enhance the instantaneous light intensity.

If slight blurriness persists, you can appropriately increase the light source brightness—for example, from 60% to 80%—to boost the peak intensity of the strobe and further “freeze” the object’s motion. For instance, when inspecting a battery electrode that moves at 2 meters per second, increasing the strobe brightness from 70% to 90% eliminates trailing artifacts entirely, making the electrode edges clearly discernible.

5. Issue 5: Defects are visible, but the detection accuracy is insufficient (large dimensional measurement errors).

In high-precision inspections of semiconductor chip pins, precision connectors, and similar components, defects can be detected, but dimensional measurement errors exceed 0.001 mm, failing to meet industrial requirements. This is often due to the light source, resulting in “blurred edge contours” or “grayscale fluctuations.”

1. 3 A common reason

• Core Reason 1: Improper light source angle

The light source angle fails to produce a sharp boundary between the object’s edge and the background, resulting in a gradual gray‑level transition at the edge. Consequently, the algorithm cannot accurately locate the edge, leading to increased measurement errors in dimension estimation.

• Core Reason 2: Unstable Brightness

The light source’s brightness varies with voltage fluctuations and temperature increases, causing grayscale values to fluctuate across different frames and resulting in measurement discrepancies exceeding 0.005 mm for the same dimension.

• Core Reason 3: Not paired with a telecentric lens

Standard lenses exhibit “distortion” (where the magnification at the edges differs from that at the center); if the light source angle is not compensated for, this distortion can further exacerbate errors in dimensional measurement.

2. Step-by-step solution

• Step 1: Adjust the light source angle to emphasize the edges.

Select the appropriate light source angle based on the object’s shape: For flat components (such as chips), use a backlight to illuminate them, creating a sharp contrast between a bright background and dark edges; for three-dimensional parts (such as connectors), employ ring lighting at a 45° angle to accentuate edge contours. For example, when inspecting chip pins, a backlight is used, causing the grayscale value at the pin edges to drop sharply from 255 (background) to 50 (pin), with an edge‑location error of ≤0.0005 mm.

• Step 2: Replace the constant-current driver light source.

Abandoning conventional voltage‑driven light sources in favor of industrial‑grade constant‑current‑driven illumination—constant‑current drive ensures stable current control, eliminating brightness fluctuations caused by voltage variations, with brightness stability within ±2%. For example, when inspecting precision connectors, a strip‑light source driven by constant current can operate continuously for 8 hours, exhibiting only a ±1% variation in luminance, while dimensional measurement errors are kept below 0.001 mm.

• Step 3: Use a telecentric lens to reduce distortion.

If the required measurement accuracy is ≥0.001 mm, a telecentric lens (with distortion ≤0.1%) must be used, and the illumination angle should be adjusted to ensure that light strikes the object parallel to its optical axis, thereby aligning with the telecentric lens’s optical path. For example, when inspecting semiconductor wafers, pairing a telecentric lens with a parallel backlit source reduces the dimensional measurement error from 0.003 mm to 0.0008 mm.

6. Issue 6: The light source suddenly goes out or its brightness drops sharply (the system shuts down immediately)

When the production line is running continuously, a sudden loss of light or a sharp drop in brightness can disrupt inspection, resulting in losses exceeding thousands of yuan per minute. Such issues are typically caused by hardware failures and require prompt troubleshooting and repair.

1. 3 A common reason

• Core Cause 1: Power cable / Sync cable is loose

Vibration from the production line and accidental contact by personnel can cause the power cable and synchronization cable connectors of the light source to become loose, resulting in poor electrical contact. Consequently, the light source may fail to receive proper power or synchronize signals.

• Core Cause 2: Light Source Controller Failure

The internal fuse in the controller has blown (due to excessive current), and the capacitor is damaged, resulting in an inability to deliver a stable current; consequently, the light source either fails to illuminate or experiences a sudden drop in brightness.

• Core Reason 3: Light Source Aging

The light source has exceeded its rated lifespan (industrial-grade LED light sources typically have a lifespan of 30,000 to 50,000 hours), and the LED chips have degraded, causing the luminance to drop below 50% of its initial value, thus failing to meet inspection requirements.

2. Step-by-step solution (with a priority on rapid production recovery)

• Step 1: Check the cable connections.

First, disconnect the power supply, then unplug and reinsert the power cable and sync cable of the light source, making sure the connectors are fully seated—you should hear a distinct “click.” If the connectors show signs of oxidation, wipe them clean with an alcohol swab before reconnecting. For example, at one electronics factory, a light source suddenly stopped working. Upon inspection, the sync‑cable connector was found to be oxidized; after wiping it down and reconnecting, the light returned to normal—entirely within five minutes.

• Step 2: Repair or replace the controller.

If the cable connection is normal, inspect the light source controller: open the controller’s housing and check whether the fuse has blown (for transparent housings, the internal metal filament can be directly observed; if blown, it will be broken). If the fuse is blown, replace it with a fuse of the same rating (e.g., 2 A/250 V). If the fuse is intact, try replacing it with a spare controller. If the light source returns to normal operation, this indicates that the original controller is faulty, and you should contact the supplier for repair or replacement.

• Step 3: Replace the aged light source.

If the light source has been in use for more than 30,000 hours, or if its brightness drops to less than 50% of its initial level, replace it with a new unit. (It is recommended to keep 1–2 spare light sources of the same model on hand to avoid delays due to production discontinuation.) After replacement, recalibrate the light source’s position and parameters to ensure that the inspection results remain consistent with the original settings.

VII. Essential Post-Commissioning Steps: Two Key Procedures to Ensure Long-Term Stability

Many people find that after resolving lighting issues, the problems recur within a few days. The root cause is failing to conduct “stability testing” and “parameter recording.” These two steps can prevent subsequent issues arising from environmental changes or equipment maintenance.

1. Stability Test (Continuous Operation for 30 Minutes)

After debugging is complete, allow the system to run continuously for 30 minutes, capturing an image every 5 minutes, with particular attention to:

• Brightness stability: Use software to analyze the image’s average gray level; the variation should be ≤ ±5%. If it exceeds this range, check whether the light source is overheating (use an infrared thermometer to measure the surface temperature of the light source; if it exceeds 60°C, install a cooling fan).

• Defect ContrastObserve the difference in grayscale values between the defect area and the background. If the difference decreases, check whether the light source bracket is loose (re‑secure it) and whether ambient light is causing interference (install a light shield).

For example, after debugging, a certain automotive parts factory ran continuously for 30 minutes, during which the average image gray-level fluctuated by only ±3%, and the defect contrast remained stable, indicating that the lighting system has achieved stability.

2. Parameter Documentation (to Avoid Repeated Debugging)

Record all calibrated parameters in the “Light Source Calibration Parameter Table,” including:

• Light source parameters: type (ring light / backlight), model, power, luminance value, polarization state, strobe frequency;

• Installation parameters: light source angle, distance from the object, and whether to install a lens hood.

• Camera parameters: exposure time, gain (a parameter matched to the light source).

When replacing parts or performing equipment maintenance, these parameters can be directly reused, eliminating the need for repeated debugging and saving time and costs. For example, after a PCB manufacturer has recorded the relevant parameters, it can simply recall them when switching to a new batch of PCBs, reducing the debugging time from two hours to just ten minutes.

Conclusion: The core of light source tuning is “precise matching.”

Adjusting machine‑vision lighting is not a “trial-and-error game”; rather, it involves precisely matching the light source type, angle, and parameters to the object’s material, defect type, and motion state. When issues arise, follow this logical sequence: first troubleshoot the hardware (position and connections), then optimize the settings (brightness and frequency), and finally consider replacing the equipment—this approach ensures efficient problem resolution. Once debugging is complete, conduct stability tests and document the settings to guarantee reliable long‑term operation.

Remember: Proper lighting can help both the camera and the algorithms achieve twice the results with half the effort— even a standard camera, when paired with the right light source, can deliver high‑precision inspection. Conversely, no matter how advanced the camera, it cannot perform effectively if the lighting is not properly calibrated.