Project Name: Imaging Experiment Report on Same-Color Red Beans and Pebbles Using a SWIR033AU SWIR Camera
Test Date: May 2026
I. Test Objective
To verify the imaging capability of the Attostek SWIR033AU SWIR camera in distinguishing organic material (red beans) from inorganic material (stones), and to compare the results with those of a visible-light camera.
II. Application Background and Principle
2.1 Application Background
In industries such as food processing, agricultural product sorting, and mineral detection, there is often a need to quickly and non-contact distinguish materials that are similar in appearance but different in nature. For example, during grain processing, inorganic impurities such as small stones may become mixed into the grain. Traditional visible-light imaging struggles to effectively distinguish them, posing a food safety risk. SWIR imaging technology offers an effective solution to this problem.
2.2 Detection Principle
The imaging range of SWIR cameras is mostly 400 nm–1700 nm, capturing images through infrared light. Organic red beans and inorganic stones have different absorption levels in the SWIR band. Stones have a higher absorption rate in the SWIR band and appear dark in the image, while red beans absorb less and appear bright, thus allowing the two to be distinguished. An external infrared light source can be added to enhance the reflection intensity difference between different regions.
2.3 Camera Performance Requirements
- High signal-to-noise ratio (SNR)
- High quantum efficiency (QE), especially near 1300 nm
Specifications of the SWIR033AU camera used in this report:
- Maximum SNR at low conversion gain: 48.45 dB
- Quantum efficiency at 1300 nm wavelength: approximately 73%
III. Test Equipment and Parameters
| Equipment/Component | Model/Specification |
|---|---|
| SWIR Camera | Attostek SWIR033AU |
| Light Source | 1300 nm infrared light source |
| Test Samples | Red beans and small stones of similar color |
IV. Test Procedure
- Mix the red bean and stone samples and place them at the center of the SWIR033AU camera’s lens field of view.
- Manually adjust the focus and aperture of the SWIR033AU camera to obtain a clear image.
- Select an appropriate exposure time (manual or automatic mode).
- Capture images with the SWIR033AU camera under the following conditions: no fill light or filter, with 1300 nm light source, and with both 1300 nm filter and light source.
- Compare the imaging differences between red beans and stones under different conditions.
V. Test Results
5.1 Image Observation Results
- Visible-light camera capture: Due to the lack of obvious visual differences, it is difficult to distinguish the same-color stones mixed in with the red beans.
- SWIR033AU direct capture: The imaging difference between red beans and stones can be directly observed and is significant. Stones appear as darker gray areas in the image due to their lower reflectivity in SWIR light, while red beans appear as brighter gray areas due to their lower absorption of infrared light.
- With 1300 nm fill light: Overall image brightness is improved, and the contrast between red beans and stones is enhanced.
5.2 Quantitative Contrast Analysis
To quantitatively evaluate the discriminative capability, contrast was calculated using the following formula:
Contrast = (I_red beans − I_stones) / Gray Scale Range
The contrast values for the captured images are shown in the table below:
| Capture Condition | Stone Gray Value | Red Bean Gray Value | Calculated Contrast |
|---|---|---|---|
| SWIR033AU direct capture | 75.6 | 133.0 | 0.23 |
| With 1300 nm fill light | 80.8 | 141.9 | 0.24 |
VI. Result Analysis
The SWIR033AU camera can effectively distinguish between red beans and stones as two different types of materials. In SWIR imaging, the gray value difference between the two is significant. The camera’s high signal-to-noise ratio meets the requirements of this application scenario. When using a 1300 nm infrared light source for fill light, the contrast is higher and the distinction between red beans and stones is more effective. In production line applications, it is recommended to use a 1300 nm infrared light source to achieve higher contrast and thereby improve detection stability.
VII. Conclusion
The Attostek SWIR033AU SWIR camera can reliably distinguish organic red beans from inorganic stones, two materials of different natures. In the test, red beans appeared as distinct bright areas in the SWIR band, while stones appeared as dark areas. The clear grayscale contrast between the two demonstrates the good applicability of the SWIR033AU SWIR camera in grain processing and food foreign object detection. With 1300 nm fill light, imaging contrast is further improved, significantly enhancing the accuracy of impurity detection on production lines.
