There are different versions of endoscopes, ranging from rigid “boroscopes” to pliable “flexoscopes”, as well as “fiberscopes” which are comprised of a flexible bundle of optical fibers.

The emergence of miniaturized cameras has transformed the nature of endoscopes, which were once only optical but have now become videoscopes which also integrate a lighting solution.

PISÉO, an innovation platform in optics-photonics, provides characterization services for endoscopes that embed cameras – and more particularly, medical endoscopes. The tests carried out by PISÉO, which are done fully independently, are recognized and based on international standards. PISÉO’s tests make it possible to demonstrate regulatory compliance of tested devices, as well as to obtain certifications – for example, CE certification or FDA approval for the American market.

Measuring and analysis equipment for endoscopes

The PISÉO optical imaging laboratory is equipped with all of the equipment necessary to carry out the measurements mentioned above. The following list provides an overview:

• Image quality analysis software IMATEST v22.1
• Standard sights produced according to the ISO 12233 standard, or following a specific protocol defined with our client
• IMATEST light sources with luminance uniformity greater than 90%, in the visible range (color temperature 3100K)
• Binder climatic chamber, reference MK115

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All ADAS systems mix sensors of different technologies, ranging from ultrasonic proximity detectors for parking assistance to blind-spot RADAR detectors and even LiDAR for the detection of obstacles in front of the vehicle. Moreover, camera-based ADAS sensors, such as the front camera system, provide a 360° view around the vehicle – and when installed inside the cabin, such as DMS and OMS, provide information on the driver’s state of alertness, the number of occupants, and whether their seat belts are properly fastened. To complement the camera-based ADAS systems, electronic rearview mirrors, or e-mirrors, offer the driver a better view of the outside environment from the cabin. These systems (also called CMS or SRVM according to car manufacturers) consist of a monitor in addition to a camera to present a field of observation to the driver in the best conditions.

Additionally, some ADAS sensors with cameras are being considered for installation in aircraft.

In all cases, these systems contribute to increasing the level of active and passive safety of a vehicle, and must ensure reliable and repeatable detection or measurement of their environment, in all conditions of use. They also must meet regulatory requirements and applicable standards.

To guarantee a high level of performance in increasingly broad uses, the needs for characterizing the performance of these systems are increasing.

PISÉO, an innovation and expertise center in optics and photonics, offers characterization services in our laboratory for ADAS systems that embed cameras.

Front camera system

• The “front camera” system is a device which is positioned behind the windshield, at the level of the interior mirror. It observes the space in front of the vehicle to read road signs such as speed limit, no overtaking, or end of construction. This system also makes it possible to provide information at night to the adaptive high-beam management system, by detecting entry into a built-up area and the presence of other vehicles coming in the opposite direction (or traveling in the same direction) in order to lower the headlight beams so as not to distract other drivers. Moreover, the front camera system can also detect lane markings to warn the driver of an unintentional crossing of a solid or dotted line. Finally, the system allows the detection of an obstacle which may appear in front of the vehicle, such as a pedestrian emerging from a line of vehicles parked alongside the road.

The tests and characteristics measured for these systems are described below. Some of the tests are performed in the visible and near IR ranges:

• • System field of view (FOV): controls the observation and detection space of the system.
• • Spatial resolution of the system: allows for measuring the spatial resolution of the system – that is to say, to determine the dimensions of the smallest object detectable by the system. This measurement is done through the measurement of the MTF.
• • The signal-to-noise ratio of the system: measures the detection power of the system according to the signal level it receives. This measurement is done by measuring the SNR.
• • Distortion: allows for measuring the distortion of the image delivered by the camera in order to take it into account in the detection algorithms. This is measured using a checkerboard pattern.
• • Color rendering – colorimetry: the colorimetry is measured on a Rezchcker chart. The color differences of the colored areas of the target are measured, and the values  DeltaE₀₀ and  DeltaC₀₀ are calculated.

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Standards & regulations

To carry out the characterizations, PISEO experts rely on recognized test methods (international standards). We are also able to develop protocols and scripts in Python for carrying out specific tests. The list below presents a non-exhaustive list of standards controlled by our laboratory.

• ISO 12233: Electronic camera imaging — resolution and spatial frequency responses

• ISO 15739: Electronic camera imaging — noise measurements

• ISO 14524: Electronic cameras — methods of measurement of opto-electronic conversion functions

• ISO 7589: Photography — sensitometric illuminants — specifications for daylight, artificial light, and printer

Measurement and analysis equipment for cameras

PISEO’s test laboratory is equipped with all the equipment necessary to carry out the measurements mentioned above. The list below gives an overview:

• IMATEST v22.1 image-quality analysis software.

• Standard targets produced according to the ISO 12233 standard, or according to a specific protocol defined with our customer.

• IMATEST light sources with luminance uniformity greater than 90%, in the visible range (color temperature 3100K) and in the near IR (940 nm) for the backlighting of the test patterns.

• Collimators with 70° and 150° field-of-view angle, allowing measurements to be taken on staffs located at distances between 400 mm and infinity.

Camera monitor system & smart rear virtual mirror ( CMS & SRVM)

The CMS system (camera monitor system), also known as SRVM (smart rear virtual mirror), or even electronic mirror (e-mirror), generally consists of two cameras, display screens inside the cockpit, and an electronic control unit. It replaces traditional exterior mirrors to provide the driver with a better in-cabin view of the outside environment. The field of vision is wider, which improves visibility in poor weather or lighting conditions, and also helps to give safety alerts. Thanks to its lightness and streamlined shape, it also helps to reduce CO2 emissions and save energy.

The tests and characteristics measured on these systems are as follows:

• Magnifications: a measure of system magnification and aspect ratio.

• Sharpness and depth of field: determined by MTF measurement.

• Resolving power: the resolving power is measured by measuring MTF at several points in the field of view.

• Distortion: the geometric distortion measurement is performed on a checkerboard pattern.

• Contrasts: contrasts are measured in different camera illumination conditions (e.g., under glare) and different screen illumination conditions.

• Uniformity: directional uniformity and lateral uniformity are measured under daytime conditions with diffuse daylight.

• Artifacts: the analysis of the number of spots that appear on the screen when the camera is dazzled by an intense light source.

• Color rendering – colorimetry: the colorimetry is measured on a Rezchcker chart. The color differences of the colored areas of the target are measured, and the values ?E00 and ?C00 are calculated.

• Shades of gray: eight levels of gray are measured, and an analysis of their perception is carried out.

• Flicker: flicker measurement according to ISO 13406-2:2001.

• Latency time: measurement of the time between the appearance of a light signal in front of the camera, and its appearance on the system screen.

• Image formation time: the measurement of the image formation time is carried out according to the ISO 9241-305:2008 standard.

Standards and regulations

To carry out the characterizations, PISEO’s experts rely on recognized test methods (international standards). We are also able to develop protocols and scripts in Python for carrying out specific tests. The list below presents a non-exhaustive list of standards controlled by our laboratory:

Regulation No 46 of the Economic Commission for Europe of the United Nations (UNECE) — Uniform provisions relating to the approval of indirect vision systems and of motor vehicles with regard to the installation of such systems

ISO 16505: road vehicles — ergonomics and performance aspects of on-board cameras — requirements and test procedures

• ISO 15008: road vehicles — ergonomic aspects of transport information and control systems — specifications and compliance procedures for in-vehicle visual presentation

• ISO 15008: road vehicles — ergonomic aspects of transport information and control systems — specifications and procedures for visual presentation in the vehicle

• ISO 9241-305: ergonomics of human-system interaction — optical laboratory test methods for electronic display screens

• ISO 13406-2: ergonomic requirements for working on flat-panel display screens — ergonomic requirements for flat-panel displays

• ISO 12233: electronic camera imaging — resolution and spatial frequency responses

• ISO 14524: electronic cameras — methods of measurement of opto-electronic conversion functions

Measurement and analysis equipment for CMS systems

The PISEO test laboratory is equipped with all the equipment necessary to carry out the measurements mentioned above. The list below gives an overview:

• IMATEST v22.1 image-quality analysis software.

• Standard targets produced according to ISO 16505 or ISO 12233 standards, or according to a specific protocol defined with our customer.

• Multispectral lighting systems uniform in luminance and standard illuminants D55, D65. Direct lighting or backlighting.

• Westboro Photonics P1230U 12 Mpx video luminance meter, lenses, and Photometrika analysis software.

• Collimators with 70° and 150° field-of-view angle, allowing measurements to be taken on staffs located at distances between 400 mm and infinity.

• Agilent DSOX2004A-ATO-8966 70 MHz oscilloscope for latency measurement.

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It is important to know the optical characteristics of an AR, VR or MR system to properly develop the software application that will be associated with it to obtain maximum performance.

For a customer in the medical field, PISÉO has developed a test protocol to know the actual optical performance of the AR system selected in connection with its software application, with a view to US Food and Drug Administration (FDA) certification for the American market. The measurements of the optical performance of these systems were carried out in the PISÉO test lab, in a controlled environment and with test equipment calibrated under ISO 17025 accreditation. They follow the recommendations given by the IEC 63145-20-20 standards and IDMS v1.1a.

AR for augmented reality makes it possible to superimpose digital content on the real world to introduce virtual objects and information. The user still sees the real environment, superimposed with this layer of digital content. The display takes place on a screen visible to the user, most often via augmented reality glasses or via a smartphone with a specific application offering AR capabilities.

Unlike AR, VR encompasses all the immersive experiences available via a VR headset or head-mounted display (HMD). The user is completely cut off from the real world, in a virtual environment visible through the VR headset.

Particularly used in the medical field to assist pre-operative teams, VR totally immerses the user into a 3D virtual environment via a VR headset. The user can thus turn their head 360° around themselves, move in space and interact with the virtual environment thanks to joysticks, for example.

VR is based on 3 pillars: interaction, immersion and the feeling of presence which work together to create a realistic virtual environment.

MR combines several technologies. An MR headset makes it possible to integrate virtual elements into the real world by allowing these elements to interact with the environment. The user is not cut off from the real world, they can see through the headset or mixed reality glasses.

This technology mixes AR and VR, which increases its potential compared to VR alone.

AR, VR or MR systems present themselves in different sectors. Some are connected to a PC and are controlled by a Windows MR type application, while others are autonomous. Still others use a smartphone with a dedicated application.

AR VR System performance testing protocols

Various performance tests are performed on these systems, but many of them are performed with protocols that are poorly defined or not defined at all. These measurements are frequently carried out with poorly controlled and uncontrolled experimental conditions. The lack of rigor when carrying out these measurements or checks can also distort their results. Under these conditions, it is difficult to compare the systems marketed objectively. With its long experience in optical system performance measurement and its ISO 17025 accreditation, PISÉO can develop protocols to test AR and VR systems.

Laboratory performance tests at PISÉO

At the request of a customer in the medical field, performance tests were carried out on Microsoft Hololens2 mixed reality glasses in the PISÉO laboratory. These tests were the subject of a prior analysis of the FDA specifications and the definition of a rigorous repeatable and reproducible protocol. The latter is based on specific internationally recognized test methods and the practice of PISÉO image quality measurement. The tests carried out focused on the following aspects:

• The measurement of the spatial resolution of the glasses by measuring the Michelson contrast on vertical and horizontal grid patterns according to the recommendations of the IEC 63145-20-20:2019 standard. These measurements were carried out in the dark and for several levels of ambient light illumination. The light levels were generated by a PISÉO laboratory illuminator and measured by a PISÉO laboratory device calibrated under ISO 17025 accreditation.

• Contrast measurement on a checkerboard pattern according to IEC 63145-20-20:2019, for several levels of ambient light.

• Measurement of luminance and luminance uniformity according to standard IEC 63145-20-20:2019.

• Geometric distortion measurement according to IEC 63145-20-20:2019.

• Spatial persistence measurement for which the protocol was established by PISÉO. Spatial persistence is the difference in the speed of movement between a real object perceived through the Hololens2 glasses, and a virtual object projected on the screen of the glasses. If the spatial persistence is too much, it can make the user of Hololens2 uncomfortable.

Given the display technology of the Hololens2 screen using the scanning of a laser beam, it was necessary to adapt the acquisition frequency of the measuring camera or Light Measuring Device (LMD) to the scanning frequency of the laser beam.

Each of the measurements presented above was carried out on each of the eyepieces of the Hololens2 glasses.

The alignment of the LMD matrix camera was carried out according to the recommendations described in the chapter dedicated to the tests on the Near Eye Display (NED) of the IDMS v1 standard 1a.

The laboratory measurements allowed the customer to qualify different parameters of the Hololens and thus ensure the performance of their VR system. Ultimately, the tests carried out by PISÉO enabled the client to obtain FDA certification to sell its application on the American market.

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