Digital Holographic Camera with HOE for Large Object Recording
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Solution Overview
Problem
Current digital holography systems are limited by the insufficient resolution of digital recording devices, which restricts the recording of holograms to small size objects, and are sensitive to vibrations, making them impractical for non-laboratory environments and larger objects.
Innovation Solution
A portable digital holographic camera system using a combination of concave and convex lenses with a holographic optical element (HOE) for compactness and vibration isolation, along with a neutral density filter for high contrast interference fringes, allowing the recording of larger objects and reducing sensitivity to environmental vibrations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If digital recording devices with insufficient resolution are used, then the system remains simple and portable, but the recording is limited to small size objects only
Solution Approach 1:
The patent introduces a diverging lens to create a virtual image of the object at a different spatial location, effectively changing the dimensional relationship between object and sensor. This allows larger objects to be recorded by forming their virtual images within the sensor's resolution capabilities, overcoming the limitation of small object recording without requiring higher resolution sensors.
Solution Approach 2:
The diverging lens acts as an intermediary optical element between the object and the digital sensor. It transforms the light rays from the object to form a virtual image that the sensor can capture, enabling the recording of larger objects that would otherwise exceed the sensor's resolution limits.
2Area of stationary object
If a diverging lens is used to reduce distance and record larger objects, then the field of view increases, but the exposure time increases due to reduction in photons reaching the sensor
Solution Approach 1:
The patent combines multiple optical elements (diverging lens, convex lens, HOE) into an integrated optical system. The convex lens and HOE work together to concentrate and redirect light, compensating for the photon loss caused by the diverging lens. This merging of optical functions allows increased field of view without excessive exposure time penalty.
Solution Approach 2:
The Holographic Optical Element (HOE) is used to modify the optical parameters of the system, specifically to concentrate and redirect light rays. By changing the light distribution parameters through the HOE, the system recovers photons that would otherwise be lost, reducing the exposure time increase that would normally result from using a diverging lens for extended field of view.
3Manufacturing precision
If conventional holographic recording materials are used, then the system can record high quality holograms, but the system becomes complex and not portable
Solution Approach 1:
The patent replaces the mechanical and chemical processing system of conventional analog holography with a digital optical system. Instead of using photographic films and chemical development processes, the system uses digital sensors to capture holographic interference patterns and processes them computationally. This substitution dramatically simplifies the system architecture and enables portability while maintaining hologram quality.
Solution Approach 2:
The patent uses digital copying and processing of holographic data instead of physical film processing. The interference patterns are captured as digital signals and can be stored, processed, and reconstructed without physical manipulation of the recording medium. This digital copying approach eliminates the complexity of chemical processing equipment while preserving hologram quality.
4Ease of operation
If the system is made portable for non-laboratory environment, then the ease of operation improves, but the sensitivity to vibrations increases
Solution Approach 1:
The patent uses pulsed laser illumination to capture holographic data in periodic, short-duration bursts. By confining the exposure to brief pulses, the system minimizes the time window during which vibrations can affect the interference pattern. This periodic action approach allows portable operation while mitigating vibration sensitivity during the critical exposure moments.
Solution Approach 2:
The system uses short pulse lasers to rapidly capture the holographic interference pattern before vibrations can significantly degrade the recording. By rushing through the exposure process in brief pulses rather than using continuous illumination, the system minimizes vulnerability to environmental vibrations while maintaining portability and ease of operation.
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 recording of high-quality digital holograms of larger objects with increased field of view and reduced exposure time, making the system compact, portable, and suitable for non-destructive testing and analysis in various environments.
Implementation Method 1
Holographic Optical Element (HOE) for controlling directions and divergences of light beams
Implementation Method 2
coherent superposition of object wave with a reference wave... hologram recording process is based on the principle of generation and recording of interference fringes
Implementation Method 3
a diverging lens can be used to reduce distance by creating a reduced in size virtual image of the object
Implementation Method 4
path difference between interfering coherent beams should not exceed more than 1⁄4th of the wavelength of light source during exposure time. Thus vibration isolation platforms... are used for hologram recording
Data Source
AI summary
A method for optimally producing a holographic image using a Holographic Optical Element (HOE) and the HOE meant for controlling directions and divergences of light beams to impart system compactness. The system uses concave and convex lenses and other beam expanding, splitting, modulating and combining optics for realization of compactness and high throughput. The thin laser beam is split using a holographic optical element and a conventional beam splitter. A neutral density filter adjusts the intensity of a reference beam to match the intensity of an object beam so that high quality digital holograms can be recorded. Effects of vibrations are minimized by the compact optical design, by anti-vibration mounts, by mounting all the opto-mechanical components on a single rigid platform and by enclosing the system. An electro-optical sensor array records holograms digitally and an algorithm numerically reconstructs and further quantifies the results using a personal computer/laptop/tablet etc.