Let me tell you the advantages and disadvantages of glass turntables used for detection - Xiang Hongyu

1. Lighting design

Merit:

• Good light transmission: The glass is transparent, and it can be illuminated directly from the bottom during inspection, illuminating the details of the back of the product (such as the internal structure of the phone case or the scorch marks on the bottom of the cookie), as clearly as looking through the glass plate with a flashlight.

• Uniform light: The flat glass surface reflects light evenly and reduces shadow interference (similar to filling in with a reflector in a studio).

Shortcoming:

• Reflective interference: The glass itself reflects bright light (like mirror reflections), which can cause the camera to misjudge scratches or colors on the surface of the product, requiring light angles or polarizing filters to eliminate reflections.

• Light scattering: If the glass is scratched or stained, the light will scatter (similar to frosted glass blurred light transmission), affecting the detection accuracy and requiring frequent cleaning.

2. Camera setup

Merit:

• Fixed camera position: The turntable rotates automatically, and the camera only needs to be fixed in one position, which can take 360-degree shots of the whole body of the product (similar to shooting a rotating display toy with a mobile phone), saving the cost of setting up the camera from multiple angles.

• Overhead Stabilization: The camera can be positioned vertically and downward to the center of the dial (like an aerial camera hovering to take pictures) to reduce image distortion caused by angle tilt.

Shortcoming:

• Height restrictions: The camera needs to be set directly above the turntable, and if you inspect oversized products (such as long parts), you may not be able to capture the details due to insufficient height.

• Vibration impact: Slight vibration when the turntable rotates (like an electric fan shaking the head), which may blur the picture of high-speed photography, and anti-shake equipment needs to be installed.

3. Take a photo with the bottom camera

Merit:

• Direct Bottom Shooting: Using the transparency of the glass, the bottom camera can directly capture the bottom of the product (such as engraving on the back of the tablet or biscuit baking marks) through the turntable, without flipping the product, and the inspection is faster.

• Double-sided simultaneous inspection: It can be shot with both top and bottom cameras (similar to a double-sided scanner) at the same time, and the efficiency is doubled.

Shortcoming:

• Glass scratch interference: After long-term use of the turntable, the bottom camera will take pictures of small scratches on the glass surface (like scratches on mobile phone film), which may be misjudged as product defects.

• Differences in light transmission: Different light transmittance rates of different materials (such as metal opacity, plastic translucent) may lead to uneven brightness at the bottom and need to dynamically adjust the light source.

Summarize applicable scenarios

Glass turntables are particularly suitable for small products (e.g., electronic components, tablets, food) that require double-sided inspection or bottom detail inspection, but are less effective for reflective-sensitive, overweight, or oversized items (e.g., automotive parts). In actual use, it is necessary to adjust the lighting, camera parameters and turntable speed according to the product characteristics!