Streamlined Ghost Image Analysis Using a New Ghost Path Drawing Tool: GhoView
As image sensors become more sensitive and offer higher pixel counts, Keysight customers have requested simple ghost image calculation tools. Illumination design and analysis software such as LightTools can perform high-precision ghost analysis, but the setup overhead may be too much for initial ghost image analysis in early design stages.
To facilitate improved ghost image control, we have devised a tool to help optical design engineers visualize two-surface ghost images early in the design process. The newly released GhoVie tool consists of a set of macros and python code that enables engineers to easily check ghost optical paths directly within the CODE V optical design and analysis software.
Introducing the GhoView tool
While not as comprehensive as illumination design and analysis tools, GhoView is easy to set up and fast to use. It provides an efficient first look for designers during the early lens design phase — identifying ghost problems earlier in the optical design process to reduce rework and streamline the design process.
The GhoView tool helps users visualize ghosts created by two-surface reflections in their design. By offering an optical path diagram of the YZ section of the ghost rays with a specified surface pair and angle of incidence, GhoView simplifies the designer’s task of identifying harmful ghost images from surfaces in the optical design. GhoVie has the following advantages over other CODE V tools (like Ghost View) to perform ghost image analysis:
- Analysis is possible even if the principal rays do not reach the image plane.
- Compatible with light sources outside the design angle of view, such as exceeding 90 degrees.
- Compatible with complex aspherical surfaces, such as camera lenses for smartphones.
- Can include the image plane (sensor plane), which is the main stray light source, in the presence of a ghost source, without the need to modify the lens data.
- Displays the same surface number as is in the lens data.
The following figures show examples of the output of the GhoView tool applied to a few lens designs in CODE V.
Figure 1. Example of GhostVie output applied to lens designs in CODE V
As an optional input, you can specify the semi-diagonal length of the sensor to color code the displayed rays that intersect on the image sensor and the rays that reach the sensor plane outside of the active sensor area. Red colored rays in the example above intersect the active sensor area, and black rays intersect the sensor plane outside the active area. In addition, you can specify the aspect ratio of the sensor to perform lighting analysis and perform evaluation of the ghost image.
The following figure shows example output for the optical path diagram and lighting analysis when these optional inputs are enabled.
Figure 2. Example output for optical path diagram and lighting analysis when optional inputs are enabled
To further streamline ghost image analysis, multiple ghost light path diagrams can be displayed in a tile pattern overview on a single chart. This chart equips engineers with a view of all the main surface contributors to stray light generation in their design.
Figure 3. Multiple ghost light path diagrams displayed in a tile pattern overview on a single chart
As part of the GhoView tool, we provide a Python script that runs the main GhoView functions with interactive input from each user.
Keyboard shortcuts allow you to quickly switch between stray light generation conditions and drawing a full ghost light path diagram, so you can quickly compare designs.
Figure 5. Keyboard shortcuts allow you to quickly switch between stray light generation conditions and drawing
Summary
Ghost images in optical systems have always presented design challenges for engineers. In recent years, image recognition technology combined with artificial intelligence (AI) has been developing, but ghost images can lead to false positives in image pattern recognition and analysis systems. With GhoView, early ghost analysis and countermeasures for two-surface reflection ghosts can be performed from the pre-design stage. This early-stage ghost image analysis and reduction help engineers avoid design rework and wasted design cycles. To support our CODE V optical design engineering community, we have made GhoView available for immediate use.
Obtaining the GhoView tool to support your engineering design and analysis
If you are using CODE V
If you are already using CODE V, you can obtain the GhoView tool from Keysight Support Portal. Visit the Optical Design Engineering support page to register and access the portal.
If you are not using CODE V
Even if you are not using CODE V, you can try this tool. For any questions, visit Keysight Support.