Camera Focus Adjustment Using Distance Sensor
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Solution Overview
Problem
In industrial camera systems, particularly those mounted on conveyor belts, there is a challenge in achieving sharp image focus quickly enough during the relative motion of objects, as the available focusing time is often insufficient due to late distance measurement, especially when objects of different heights are moving closely together.
Innovation Solution
A camera system with a focus-adjustable reception optics and an integrated distance sensor measures the distance to the object, allowing a control and evaluation unit to set the focus position based on the measured distance value, accepting a focus deviation within a defined range to achieve sharper images quickly, even if the ideal focus position is not perfectly set.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the focus position is adjusted to the ideal position based on distance measurement, then image sharpness is improved, but the focusing time becomes too long for moving objects
Solution Approach 1:
The patent applies partial action by intentionally introducing a focus deviation that remains within the depth of field range. Instead of achieving perfect focus at the ideal position, the system accepts a controlled imperfection (focus deviation) that is sufficient for the application requirements. This allows the focusing process to complete faster while still producing usable images for tasks like code reading, where perfect sharpness is not critical.
Solution Approach 2:
The system performs preliminary distance measurement using a time-of-flight sensor before the object reaches the optimal capture position. This early measurement allows the control unit to calculate the ideal focus position in advance and begin the focusing process earlier, maximizing the available focusing time while still achieving acceptable image quality within the depth of field constraints.
2Loss of time
If a laser scanner is used for distance measurement beforehand, then focus adjustment time is sufficient, but device complexity and cost increase
Solution Approach 1:
The patent merges the distance measurement function into the camera system by integrating a time-of-flight sensor directly with the image sensor. This combination allows both distance measurement and image capture to be performed by a single integrated device rather than requiring separate laser scanner and camera systems. The time-of-flight sensor shares the optical path and processing electronics with the image sensor, reducing overall system complexity while maintaining sufficient focus adjustment time.
Solution Approach 2:
The integrated time-of-flight sensor serves multiple functions: it provides distance measurement for focus adjustment, enables depth information for the image processing unit, and can potentially be used for other measurements. This multi-functionality eliminates the need for dedicated separate devices like laser scanners, reducing system complexity while achieving the same timing benefits.
3Device complexity
If distance measurement is performed late in the process, then device complexity is reduced, but sufficient focusing time is not available
Solution Approach 1:
The time-of-flight sensor is positioned to perform distance measurement as objects enter the measurement range, well before they reach the camera's detection area. This preliminary measurement allows the control unit to calculate the ideal focus position early and initiate the focusing process with maximum available time. The early timing is achieved by optimizing the sensor placement and triggering sequence without adding complex measurement systems.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach shortens focusing times, ensuring sufficient image sharpness for applications like code reading, increasing the success rate of image evaluations and maintaining the intended purpose, even under time constraints.
Implementation Method 1
a distance sensor measures a distance value between the camera and the object to be recorded, in particular by means of a time-of-flight method
Implementation Method 2
a focus-adjustable receiving optic, i.e. a receiving lens that, depending on the quality requirements, has one or more lenses and other optical elements
Data Source
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AI summary
A camera (10) for detecting an object (48) moving through a detection area (14) is specified, which has an image sensor (18) for recording image data, a receiving optic (16) with a focus adjustment unit (17) for setting a focus position, a distance sensor (24) for measuring a distance value to the object (48) and a control and evaluation unit (38) connected to the distance sensor (24) and the focus adjustment unit (17) in order to set a focus position depending on the distance value and to trigger the recording of image data in a focus position in which there is a focus deviation from an ideal focus position according to the measured distance value, wherein the focus deviation remains small enough for a required image sharpness of the image data.