Photogrammetric camera and method for the two-dimensional measurement of objects
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Solution Overview
Problem
Existing photogrammetric cameras face challenges in efficiently measuring surfaces with different properties due to limitations in illumination modes and the need for complex, space-consuming pupil filter systems, leading to inaccurate measurements and slow switching between illumination types.
Innovation Solution
A photogrammetric camera with a micromirror device in the pupil plane allows for quick switching between coaxial dark field and coaxial reflected light illumination modes by controlling micromirrors to adjust illumination angles within a range of 70° to 90°, enabling efficient two-dimensional measurement and potential three-dimensional measurement by combining images with different illumination settings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If automated interchange units (turret mounts) are used to accommodate different stop elements in the pupil plane, then variable pupil filtering is achieved, but the device becomes mechanically complicated and requires a lot of installation space
Solution Approach 1:
The patent replaces the mechanical automated interchange unit (turret mount) with an LCD panel that uses electrical control to achieve pupil filtering. The LCD panel can be switched between different illumination modes (dark field, reflected light, etc.) through electrical signals, eliminating the need for mechanical movement and complex interchange mechanisms while maintaining the ability to vary pupil filtering settings
2Adaptability or versatility
If automated interchange units are used for pupil filtering, then variable filtering is possible, but the switching between illumination types is slow
Solution Approach 1:
The patent replaces mechanical interchange units with an electrically controlled LCD panel that can switch between different illumination modes almost instantaneously. The LCD panel's electrical switching mechanism eliminates the time required for mechanical movement and positioning, enabling rapid transitions between dark field, reflected light, and other illumination types
3Productivity
If LCD panels are used for pupil filtering, then installation space is reduced and switching speed is increased, but the incident light is polarized causing intensity losses
Solution Approach 1:
The patent employs a telecentric lens system with dynamically adjustable aperture settings that can adapt to different illumination modes. The lens maintains telecentricity while allowing the aperture to be adjusted electrically, optimizing light transmission and reducing intensity losses associated with fixed aperture designs. This dynamic adjustment compensates for the polarization-related intensity losses by optimizing the optical path for each illumination mode
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
The camera achieves rapid and accurate two-dimensional measurement, with the ability to highlight or suppress imaged structures, and when combined with focal plane distance information, enables three-dimensional measurement, overcoming the limitations of traditional systems.
Implementation Method 1
A micromirror in the first tilt position reflects light produced by the illumination system so that the light cannot reach the object. By contrast, light reflected at the object is reflected by a micromirror in the first tilt position so that the light can reach the image sensor. A micromirror in the second tilt position reflects light produced by the illumination system so that the light can reach the object. By contrast, light reflected at the object is reflected by a micromirror in the second tilt position so that the light cannot reach the image sensor.
Implementation Method 2
an object-side telecentric lens with a pupil plane, a two-dimensional image sensor
Implementation Method 3
an illumination system configured to produce light and, with the aid of the micromirror device, direct said light at the object to be measured
Data Source
AI summary
A photogrammetric camera for the two-dimensional measurement of objects has a lens, an image sensor and a pupil filter configured as a micromirror, each of which is transferable into a first and second tilted position. An illumination system produces light. A micromirror in the first tilt position reflects light produced by the illumination system such that the light cannot reach the object while light reflected at the object is guided to the image sensor. Conversely, a micromirror in the second tilt position reflects light such that the light can reach the object while light reflected at the object is supplied to the image sensor. To implement a recording of an image with coaxial dark or coaxial reflected light illumination, the micromirror device is controlled such that the light produced by the illumination system is incident on the surface at different angles within an angular range of at least arcsin(NA).