Industrial cameras don't need to continuously capture images.

In most automated inspection projects, the frame at which the product reaches the inspection position is truly useful.

If the timing of data acquisition is inaccurate, even if the camera is running continuously, issues such as image blurring, excessive bandwidth usage, or excessive processing load may occur.

Therefore, industrial cameras typically employ two types of imaging methods:

Hard triggerSoft trigger.

01 Hard trigger: Photo capture is controlled by an external signal.

A hard trigger sends an electrical signal to the camera via a sensor, PLC, or other device.

The typical process is:

Product in place → Sensor output signal → Camera exposure → Image processing.

Common trigger settings include:

• Rising-edge trigger;

• Falling edge trigger;

• Single-frame acquisition;

• Continuous trigger acquisition.

The primary advantage of hard triggering is its direct response and relatively deterministic timing, as it does not rely on the communication process with the host computer.

Therefore, it is more suitable for:

• Production takt time is fixed;

• Product location is clearly defined;

• Has high requirements for photo-taking timing;

• A production line that requires the camera and light source to work in synchronization.

It’s important to note that the stability of hard triggering doesn’t depend solely on the camera.

The sensor installation location, the quality of the trigger signal, the product speed, and the trigger delay can all affect the final shooting position.

02 Soft trigger: The acquisition command is sent by the program.

Soft triggering is initiated by the host computer program sending a capture command via the camera SDK.

The process is typically:

Program judgment condition → Send trigger instruction → Camera exposure → Return image.

Its advantage is flexible control.

The program can determine when the camera should capture images based on the product model, inspection process, or different tasks.

Soft triggering is more suitable:

• The detection logic is relatively complex;

• There are many product models;

• The image capture time is not fixed.

• A system that requires unified control by software.

However, software triggering depends on the computer, operating system, and communication link.

When the system load is high or communication delays occur, the actual photo-taking time may fluctuate.

03 How do you choose between hard triggering and soft triggering?

Simply put:

Pay attention to the timing and stability of shooting, and prioritize hard triggering.

By emphasizing procedural control and task flexibility, soft triggering can be considered.

04 Why is it not recommended to take consecutive images blindly during detection?

Continuous capture mode allows the camera to continuously output images at the set frame rate.

This approach is convenient for debugging and also suitable for applications that require continuous observation or continuous processing.

However, in projects that only require detecting the moment a product arrives, continuous image capture may pose several issues.

Occupies bandwidth and computing resources

The camera continuously transmits images to the computer.

Even if most of these images are not involved in detection, they still consume interface bandwidth, memory, and processor resources.

Add invalid image

Images captured when the product is not in place, positioned incorrectly, or in an unstable motion state typically have no detection value.

The program also needs to identify valid frames from a large number of images, increasing the processing complexity.

The timing of the shot may not be accurate.

Continuous data collection does not necessarily mean you’ll be able to capture the product in the optimal position.

If the exposure time, product speed, and capture frame rate are mismatched, positional deviation or motion blur may still occur.

Therefore, for fixed-station inspection, key frames should typically be captured based on the product-in-place signal rather than relying on continuous image acquisition to detect timing.

05 The core value of keyframe capture

The difference between continuous acquisition and trigger-based acquisition isn't just the number of images.

The key lies in whether the timing of data collection is controllable.

• Continuous acquisitionThe camera continuously outputs images, making it suitable for debugging, observation, and continuous analysis.

• Trigger collectionTake photos only when the set conditions are met; suitable for automated detection.

What industrial vision typically focuses on is not how many images are captured, but rather whether it can consistently obtain a clear, accurately positioned image when the target is in place.

Summary

Hard triggering, soft triggering, and continuous acquisition don't have any absolute advantages or disadvantages; the choice depends on the specific project requirements.

• Hard triggerSuitable for production lines with fixed rhythms and high requirements for timing and stability;

• Soft trigger: Suitable for systems with complex logic that require flexible program control;

• Continuous acquisitionSuitable for applications requiring debugging, continuous observation, or situations where frame-by-frame processing is essential.

For most fixed-position inspection applications, accurately controlling the timing of image capture is often more important than continuously generating a large volume of images.

An industrial camera isn't about taking as many pictures as possible; rather, it's about capturing the right image at the right location and the right time.