3D Scanner Rolling Shutter Synchronization for Dental Scanning
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing 3D scanners struggle to create digital 3D representations of objects within a short time period while maintaining sufficient image quality, particularly in dental technology where rapid and accurate scanning is crucial for efficient dental restoration production.
Innovation Solution
A 3D scanner design that projects light patterns at a frame rate N times the camera's frame rate, using a rolling shutter mode to expose and read out pixel rows sequentially, interleaving exposures with different light patterns to enhance scanning speed and quality.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the frame rate of the projection unit is increased to N times the camera's frame rate to improve scanning speed, then productivity is improved, but device complexity increases due to the need for precise synchronization and interleaved pattern projection
Solution Approach 1:
The projection process is segmented into multiple interleaved patterns projected at different time intervals. Instead of projecting one complete pattern at a time, the system divides the projection into N segments that are interleaved with camera exposures, allowing parallel processing and improved throughput while maintaining manageable complexity through structured segmentation
Solution Approach 2:
The system employs periodic projection of light patterns at a frame rate N times the camera frame rate. This periodic action creates a synchronized rhythm between projection and capture operations, where patterns are projected periodically and camera exposures are timed to capture specific phases of the periodic projection sequence, enabling high-speed scanning through rhythmic, predictable timing
2Productivity
If rolling shutter mode is used to sequentially expose and read out pixel rows for faster data processing, then productivity is improved, but measurement precision deteriorates due to time offsets between different pixel rows
Solution Approach 1:
Multiple light patterns are projected in advance at different time intervals before the camera completes its readout sequence. The projection unit prepares and projects patterns for multiple rows simultaneously at different times, so that when each pixel row is read out sequentially, the corresponding light pattern has already been projected and is captured, eliminating the precision loss that would otherwise occur from time offsets
Solution Approach 2:
The system replaces the traditional mechanical approach of capturing all pixels simultaneously (which would require complex global shutter hardware) with an electronic timing solution. By using the rolling shutter's sequential readout characteristic and substituting it with electronically controlled periodic pattern projection, the system achieves both high-speed data processing and maintained measurement precision through software-timed coordination rather than mechanical synchronization
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
Enables the creation of high-quality digital 3D representations of objects in a very short time, facilitating efficient and accurate dental scanning.
Implementation Method 1
The light beam reflected from the surface of the object is captured by one or more cameras with an image sensor and converted into an electrical signal. Each pixel comprises at least one light-sensitive element for generating electrical charge from light incident along an exposure direction
Data Source
Figure 1
Figure 2
Figure 3
AI summary
The invention relates to a 3D scanner (1) for optically scanning the surface (7) of an object (8), comprising at least one scan unit (3) which has a projection unit (4) for projecting images containing light patterns onto the object (8) and at least one camera (5) for capturing the images, wherein a frame rate of the projection unit (4) corresponds to N times a frame rate of the at least one camera (5), where N is a natural number greater than 1, wherein each camera (5) has an image sensor (9) with a plurality of pixel rows (11) arranged in a row, wherein the pixel rows (11) are exposed successively in each pass and read out line by line, wherein in a direction associated with the line-by-line readout of the pixel rows (11), images have an image dimension SF, image areas have an image area dimension SR, and light patterns have a light pattern dimension SP.and a control unit (2) for controlling the at least one scan unit (3), wherein the control unit (2) is configured such that - per pass a set of N+1 images (1A, 1B, 1C; 2A, 2B, 2C; 3A, 3B, 3C) is projected onto the surface (7) of the object (8), wherein the light patterns are projected such that the light pattern dimension SP is: SP ≥ SF * 2/(N+2), - wherein in each image (1A, 1B, 1C; 2A, 2B, 2C; 3A, 3B, 3C) of a respective set a light pattern is projected such that an image area with the image area dimension SR is at least covered, wherein SR = SF * 2/(N+2), wherein the image area in each subsequent image (1B, 1C; 2B, 2C; 3B, 3C) of a respective set is shifted by SF * 1/(N+2) along the direction assigned to the line-by-line reading of the pixel rows, and - wherein in at least one set (1A, 1B, 1C; 2A, 2B, 2C), in one to at most N-1 consecutive images (1C, 2C), ending with the (N+1')th image,Each time, one or more additional light patterns belonging to subsequent cycles are projected.