WO2025233262A1

WO2025233262A1 - Method and apparatus for calibrating and testing an optical sensor

Info

Publication number: WO2025233262A1
Application number: PCT/EP2025/062170
Authority: WO
Inventors: Werner Rauch
Original assignee: Ams Osram AG
Current assignee: Ams Osram AG
Priority date: 2024-05-07
Filing date: 2025-05-05
Publication date: 2025-11-13
Anticipated expiration: 2026-11-07

Abstract

According to the invention, a method for calibrating and testing an optical sensor device, comprises the steps of : - providing information on a property of optical sensor device samples derived from preliminary testing the optical sensor device samples, - choosing at least two stimuli for applying on the optical sensor device samples, - applying the at least two stimuli on the optical sensor device samples using a LED, - determining a calibration function for calibrating the optical sensor device, - measuring readings when both stimuli are applied on the optical sensor device samples, - calculating a calibration factor for each optical sensor device sample, - calculating a variable of a calibration function, - setting up of the calibration function of the acquired calibration factors, - determining property of the optical sensor device with a production test, - applying the at least two stimuli on the optical sensor device using a LED, - measuring the production test readings when both stimuli are applied on the optical sensor device, - calculating the ratio of the production test reading of stimuli 1 to the production test reading of stimuli 2, - determining a correction factor with inserting the ratio of the production test reading of stimuli 1 to the production test reading of stimuli 2 in the calibration function, - determining the optical sensor device property by multiplying the response of the LED used with the correction factor. Furthermore, a corresponding apparatus for calibrating and testing an optical sensor device is disclosed.

Description

METHOD AND APPARATUS FOR CALIBRATING AND TESTING AN OPTICAL

SENSOR

DESCRIPTION

TECHNICAL FIELD

The present invention relates to a method for calibrating and testing an optical sensor device and an apparatus for calibrating and testing an optical sensor device .

BACKGROUND

Optical sensors are devices that have the ability to trans form light into electronic signals and have become an integral part of numerous applications . These range from monitoring environmental conditions , such as light intensity and color, to medical diagnostics where they can help detect and monitor various health conditions . They are also used in industrial automation to ensure processes are running smoothly and ef ficiently .

Despite their use across various fields , one of the primary challenges faced in the deployment of these sensors is ensuring their accuracy and reliability .

Therefore , the calibration and testing of optical sensors are important steps in their production and usage .

Calibration is a process that involves fine-tuning the sensor' s response so that it aligns with a known standard or reference . This ensures that the readings obtained from the sensor are not only accurate but also consistent across di fferent operating conditions and over time . Without proper calibration, the sensor' s readings could vary, leading to erroneous results or interpretations .

The calibration of optical sensors typically involves several steps . First , the sensor is exposed to a light source with known properties . This could be a light source of a speci fic intensity or color, or a series of light sources that cover a range of intensities or colors . The sensor' s response to this known light source is then measured .

Next , the sensor' s response is compared to the known properties of the light source . Any discrepancies between the sensor' s response and the known properties of the light source indicate an error in the sensor' s readings . This error is then used to adj ust the sensor' s response . The goal is to minimi ze the error, thereby aligning the sensor' s response with the known properties of the light source .

This calibration process may be repeated under various conditions to account for factors such as temperature and humidity, which can af fect the sensor' s performance . The calibration data is then stored and used to correct the sensor' s readings in real-time during its operation .

Testing, on the other hand, is a comprehensive evaluation of the sensor' s performance under a variety of conditions . This includes inter alia testing of optical sensors with regard to channel sensitivity and filter position .

The latter involves a series of steps designed to evaluate the sensor' s functionality : Firstly, the sensor' s channel sensitivity is tested . Channel sensitivity refers to the ability of a channel in an optical sensor to accurately detect and measure its respective color or light intensity . The sensor is exposed to varying intensities or colors of light , and its response is measured for each channel . The goal is to ensure that each channel can accurately detect and measure these changes .

Next , the impact of the filter position on the sensor' s readings is evaluated . The filter in an optical system is used to selectively allow light of certain wavelengths to pass through while blocking others . The position of the filter can af fect which wavelengths are allowed to pass and which are blocked . The filter position is therefore to be evaluated .

Above discussed testing and calibrating can be done with stimuli . With this , the optical sensor is exposed to a series of controlled light stimuli , each with known properties . These stimuli could vary in terms of intensity, color, or spectral characteristics . The sensor' s response to each stimulus is then measured and compared to the known properties of the stimulus .

Typically, such a test setup is referred to as " static" calibration . Such a single calibration factor is only valid for one dedicated filter position . To render the calibration valid for all devices under test ( DuT ) , one dedicated calibration factor for each filter position would be needed . Therefore , this type of calibration requires broad limits to accommodate the impact based on the filter position .

On top, static calibrations can lead to signi ficant variations when di f ferent equipment is used, necessitating substantial guard banding . Also , In the context of the sputter process , there is a notable fluctuation in the filter position, speci fically in the wavelength, which can vary by as much as +/- 10% . This variation has a profound impact on the readings obtained from the devices . When only a single stimulus is used for testing, it becomes challenging to distinguish the ef fects caused by the filter position from those caused by the channel sensitivity .

These factors can signi ficantly influence the results , but their ef fects are often intertwined and di f ficult to separate when using traditional testing methods .

Furthermore , in order to gather comparable information about a device ' s filter channel , the most feasible technique is a measurement conducted with a monochromator . This method, however, is notably time-consuming, with the testing duration being much longer than other methods . Additionally, it requires the deployment of high-priced equipment . Despite these challenges , this method is still considered a " static" approach .

These challenges highlight the need for more cost-ef fective , and user- friendly method for calibrating and testing optical sensors . This invention aims to address these challenges .

SUMMARY

The obj ect or the present invention is therefore to provide a method for calibrating and testing an optical sensor device and apparatus for calibrating and testing an optical sensor device , which solves the above addressed problems and presents a simpler, faster and more cost-ef fective method and apparatus for calibrating and testing an optical sensor device . According to the invention, the obj ect is met by a method with the steps speci fied in claim 1 and an apparatus as speci fied in claim 15 .

Therefore , a method for calibrating and testing an optical sensor device is proposed by the invention, the method comprising the following steps :

- providing information on a property of optical sensor device samples derived from preliminary testing the optical sensor device samples ,

- choosing at least two stimuli for applying on the optical sensor device samples ,

- applying the at least two stimuli on the optical sensor device samples using a LED,

- determining a calibration function for calibrating the optical sensor device ,

- measuring readings when both stimuli are applied on the optical sensor device samples ,

- calculating a calibration factor for each optical sensor device sample ,

- calculating a variable of a calibration function,

- setting up of the calibration function of the acquired calibration factors ,

- determining property of the optical sensor device with a production test ,

- applying the at least two stimuli on the optical sensor device using a LED,

- measuring the production test readings when both stimuli are applied on the optical sensor device ,

- calculating the ratio of the production test reading of stimuli 1 to the production test reading of stimuli 2 , determining a correction factor with inserting the ratio of the production test reading of stimuli 1 to the production test reading of stimuli 2 in the calibration function,

- determining the optical sensor device property by multiplying the response of the LED used with the correction factor .

This method allows for the testing of properties of the optical device such as channel sensitivity independent of the filter position and also for the filter position itsel f . This is a signi ficant advantage as it provides flexibility in testing and reduces dependency on speci fic conditions .

The testing and calibrating is less time consuming and more cost-ef fective than testing and caliobrating e . g . with a monochromator .

Less wider guard banding can be used .

Furthermore , the method enables the use of cost-ef fective equipment in production .

The calibration function that has been obtained is tailored and is speci fic to the setup of the optical sensor device setup . This implies that the calibration function is intrinsically linked to the unique characteristics of the setup, including the type of optical sensor device , the LED used, and the speci fic conditions under which the stimuli are applied . With this , the calibration function accurately reflects the unique interactions and responses within this particular setup, thereby enhancing the precision and reliability of the measurements and calculations derived from it . As the channel sensitivity is an integral attribute of the sensor due to its relation to the sensor' s capacity to discern variations in the optical signal it is speci fically engineered to measure , the property of the optical sensor device may be a channel sensitivity .

The channel sensitivity dictates the sensor' s proficiency in detecting and responding to changes in the optical signal . Calibration and testing of this attribute can ascertain that the sensor is operating at its maximum ef ficiency . This implies that the sensor is not only functioning as anticipated but is also responsive to the speci fic fluctuations it is designed to detect .

In a preferred embodiment of the invention, the property of the optical sensor device is a filter position .

Filter position determines the wavelengths of light the sensor can detect . By calibrating and testing this property, it can be ensured that the sensor is accurately detecting light at the intended wavelengths . This can lead to more accurate data collection, improved performance of the optical sensor device , and ultimately, more accurate results in the application where the sensor is used .

Furthermore , for the preliminary testing of the optical sensor device samples a monochromator may be used .

Testing and calibrating with a monochromator provides highly accurate and precise measurements .

A monochromator is a device that can isolate individual wavelengths of light from a broader spectrum . By using a monochromator in the preliminary testing phase , it is possible to assess the sensor' s response to speci fic wavelengths of light . This method ensures that the sensor is accurately calibrated for each wavelength it is designed to detect , leading to more reliable data collection and improved performance of the optical sensor device in its intended application .

In another preferred embodiment of the invention, for the preliminary testing of the optical sensor device samples a spectrally flat light source is used .

Testing and calibrating of the optical sensor device samples with a spectrally flat light source provides comprehensive and uni form testing across a wide range of wavelengths .

A spectrally flat light source emits light with a uni form intensity across a broad spectrum of wavelengths . By using such a light source in the preliminary testing phase , it ' s possible to assess the sensor' s response to a wide range of light conditions in a single test .

This approach guarantees that the sensor is precisely adj usted for every wavelength it is intended to detect , resulting in more dependable data gathering and enhanced functionality of the optical sensor device for its speci fic use .

In a further preferred embodiment of the invention, the calibration function is polynomial .

A polynomial function is a speci fic kind of mathematical function distinguished by its form . It is composed of variables and coef ficients , and it only employs the mathematical operations of addition, subtraction, multiplication, and non-nega- tive integer exponents of variables . A polynomial function for a correction coef ficient in calibrating and testing is very flexible and adaptable .

A polynomial function can model complex relationships between variables due to its ability to take on a variety of shapes depending on the degree and coef ficients of the polynomial . This makes it a versatile tool for calibration, as it can accurately model the behavior of the sensor across a wide range of conditions .

In another embodiment of the invention, an individual calibration function is assigned to each optical sensor device setup .

With this , a tailored calibration is provided for each speci fic setup . Assigning an individual correction factor to each setup allows for the unique characteristics and variations of each sensor device setup to be taken into account . This can include factors such as manufacturing di f ferences , environmental conditions , or the speci fic application in which the sensor is used .

Furthermore , a ratio between the readings , when the stimuli are applied during the determination of the coef ficients of the calibration function, and the filter position is steady . When the ratio between the device readings and the filter position is steady, it indicates that the sensor is responding predictably to changes in the filter position . This means that for any given filter position, the sensor will always produce the same reading . This consistency is crucial for ensuring the reliability of the sensor' s measurements .

This steady ratio also simpli fies the calibration process . Since the relationship between the device readings and the filter position is known and constant , it ' s easier to predict how the sensor will respond to di f ferent filter positions . This leads to more accurate calibrations and, ultimately, more accurate sensor readings .

Furthermore , a light source used for testing and calibrating the optical sensor device may be a white LED .

A white LED as a light source for testing and calibrating the optical sensor device is ef ficient , stable and has a broadspectrum coverage .

White LEDs are energy ef ficient and have a long li fespan, which makes them a cost-ef fective choice for testing and calibration processes . They can operate for extended periods without signi ficant degradation in performance , ensuring consistent and reliable results during the calibration and testing process .

In addition, white LEDs produce a stable and continuous light output , which gives accurate and consistent sensor readings . Furthermore , white LEDs cover a broad spectrum of light , including both visible and some non-visible wavelengths . This broad-spectrum coverage allows the sensor to be tested and calibrated across a wide range of light conditions , enhancing its versatility and applicability in di f ferent scenarios .

In another embodiment of the invention, a light source for testing and calibrating the optical sensor device may be a color LED .

Color LEDs as a light source for testing and calibrating the optical sensor device are able to provide speci fic wavelengths of light , energy ef ficiency, and have a long li fespan .

Color LEDs are capable of emitting light at speci fic wavelengths . This allows for targeted testing and calibration of the optical sensor device , ensuring that it is accurately calibrated for the speci fic wavelengths it will encounter in its intended application .

They can operate for extended periods without signi ficant degradation in performance , making them a cost-ef fective choice for the calibration and testing process . This ensures consistent and reliable results during the calibration and testing process .

Furthermore , the use of color LEDs allows for flexibility in testing conditions . Di f ferent color LEDs can be used to simulate a variety of lighting conditions , enhancing the versatility of the calibration and testing process .

The light source for testing and calibrating the optical sensor device may also be a combination of a color LED and a white LED . By using both a color LED and a white LED, the sensor can be tested and calibrated under a variety of light conditions , enhancing its versatility and applicability in di fferent scenarios . This can lead to more accurate data collection, improved performance of the optical sensor device , and ultimately, more accurate results in the application where the sensor is used .

In a further preferred embodiment of the invention, a light source for testing and calibrating the optical sensor device is a combination of at least two color LEDs .

Color LEDs are capable of emitting light at speci fic wavelengths . By combining at least two color LEDs , it ' s possible to cover a broader range of wavelengths . This allows for more comprehensive testing and calibration of the optical sensor device . In addition, the use of a combination of color LEDs increases the versatility of the testing and calibration process . Di fferent combinations of color LEDs can be used to simulate a variety of lighting conditions , enhancing the adaptability of the calibration and testing process to di f ferent scenarios .

Furthermore , using a combination of color LEDs allows for precise control over the light spectrum used in testing and calibration . This can be particularly useful in applications where the sensor needs to be tested under very speci fic light conditions .

The light source for testing and calibrating the optical sensor device may also be a combination of more than one color LED and a white LED .

Each color LED can emit light at speci fic wavelengths , allowing for targeted testing and calibration of the sensor' s response to these wavelengths . The white LED, on the other hand, emits light across a broad spectrum, providing a uni form intensity across a wide range of wavelengths . The combination of two color LEDs with a white LED allows for a more thorough and diverse testing and calibration process .

Utili zing this combination allows the sensor to undergo testing and calibration under a diverse range of light conditions , thereby boosting its adaptability and relevance in various situations . This can result in more precise data gathering, enhanced functioning of the optical sensor device , and in the end, more accurate outcomes in the context where the sensor is deployed .

Furthermore , the method may be conducted at least two times on the same optical sensor device and the average of the resulting properties may be taken as the optical sensor device property .

With this , the accuracy and reliability of the calibration and testing process is enhanced .

Repeating the calibration and testing process multiple times on the same device allows for the collection of more data points , which can help to minimi ze the impact of random errors or anomalies that may occur in a single test run . This leads to more accurate and consistent results , improving the performance of the optical sensor device in its intended application .

Taking the average of the results further enhances the accuracy of the calibration and testing process . The average can help to smooth out any outliers or fluctuations in the data, providing a more accurate representation of the sensor' s performance .

In a further preferred embodiment of the invention, the variable of the calibration function is calculated by determining the ratio of the reading of stimuli 1 to the reading of stimuli 2 of each optical sensor device sample .

With this , a normali zed and relative measure of the sensor' s response is provided .

By using a ratio , the calibration function takes into account the relative response of the sensor to the two stimuli , rather than their absolute values . This mitigates the impact of external factors , such as environmental conditions or sensor manufacturing variations , that might af fect the absolute readings of the stimuli . In another embodiment of the invention, the variable of the calibration function is calculated by determining the average of the reading of stimuli 1 and the reading of stimuli 2 of each optical sensor device sample .

Using the average of the two stimuli can help to mitigate the impact of extreme values or outliers , which could skew the results i f a ratio was used . This can lead to more accurate and reliable calibration and testing results , improving the performance of the optical sensor device in its intended application .

Furthermore , the use of an average is a simple and straightforward statistical measure that can be easily understood and interpreted . This can facilitate the analysis of the calibration and testing results , and aid in the identi fication of any trends or patterns in the sensor' s performance .

Furthermore , the invention proposes an apparatus for calibrating and testing an optical sensor device , the apparatus comprising :

An apparatus for calibrating and testing an optical sensor device , the apparatus comprising : a LED configured to apply at least two stimuli on the optical sensor device , a measurement unit configured to measure the readings and the production test readings when both stimuli are applied on the optical sensor device , and a processing unit configured to calculate a variable of a calibration function, and to determine a correction factor by inserting the ratio of the production test readings into a calibration function and to determine a property of the optical sensor device by multiplying the response of the LED with the correction factor . What has been said with respect to the method may analogously be applied to the apparatus and therefore need not be repeated there . Apparatus embodiments and details have a counterpart in the method and vice versa .

BRIEF DESCRIPTION OF THE DRAWINGS

In the following, the invention will be described in further detail with reference to the accompanying drawings , wherein :

FIG . 1 depicts a flowchart according to an embodiment of the invention .

DETAILED DESCRIPTION

The present invention relates to a method for calibrating and testing an optical sensor device and a corresponding apparatus .

With said method, accuracy and reliability of the optical sensor device is to be enhanced with not only one calibration factor, which is valid for one dedicated filter position only, but a function rendering the calibration valid for all filter positions of the device under test ( DuT ) .

In the context of optical testing, usually a stimulus is applied to the device under test . The optical sensor device ' s response is contingent upon the interplay between the spectral shape of the stimulus and the spectral shape of the device ' s sensitivity curve . Due to the sputter process, the filter position in the optical sensor devices exhibits a notable variation within a range of +/-10 nm. Despite this variation, the shape of the curve remains relatively stable. This shift in filter position induces a corresponding variation in the optical sensor device's response .

Existing calibration methods for a test setup utilize single factors to either adjust the light source or correct the device reading. Such a "static" calibration is only valid for a specific point on the curve, corresponding to a dedicated device filter position.

If the filter position shifts, a systematic error is introduced into the measurement. The potential error resulting from the filter shift varies for each filter channel, with the worst-case scenario being in the range of +/-17 % of the device reading.

An additional factor to consider is that at the filter position of the calibration, it is to compensate for the variation of the optical stack and light-source of our setups. However, if the filter position is shifted, the differences in the setups lead to different readings, introducing an additional source of error.

As a result of this filter shift-induced error, large guard bands in the test limits must be introduced.

To avoid this, the present invention introduces a dynamic calibration method involving a series of technical steps.

The process may begin with the preliminary step of collecting samples, e.g. from a lab, which provide information about the sensor's property to be determined, e.g. the channel sensitivity and/ or the filter position of the DuT , as to be seen in FIG . 1 as S I .

Those pre-measurements of these samples are conducted using e . g . a calibrated monochromator, a device that isolates a narrow band of wavelengths from a broader spectrum of light . The use of a calibrated monochromator ensures that the measurements are precise and consistent , thereby enhancing the reliability of the calibration process .

Alternatively, for the preliminary testing of the optical sensor device samples a spectrally flat light source is used .

To achieve stable results , the so acquired measurement data, either with a monochromator or with a spectrally flat light source , typically undergoes a process of mathematical smoothing . This post-processing step involves the use of mathematical techniques to reduce noise and variability in the data .

The property of the optical sensor device to be determined can be the channel sensitivity and/or the filter position .

In the context of optical sensors , the term "channel sensitivity" denotes the degree of reactivity of the sensor to variations in the parameters it is engineered to monitor . These parameters could encompass factors such as temperature , refractive index (RI ) , and others . Typically, sensitivity is expressed as the alteration in the sensor' s output (which could be a shi ft in wavelength or intensity) per unit modi fication in the parameter under observation . Furthermore , the device reading depends on the combination of the spectral shape of the stimuli used and the spectral shape of the device sensitivity curve . This quanti fication provides a measure of how ef fectively the sensor can detect and respond to changes in the parameter it is designed to measure .

Whereas the term " filter position" is typically used to describe the speci fic location of an optical filter within the overall structure of the sensor system . Optical filters have the ability to selectively transmit light of certain wavelengths while blocking others . This selective transmission is key to the operation of many optical systems , allowing them to respond to speci fic wavelengths of light while ignoring others .

In the process of conducting optical sensor measurements , i f the lab provides information about the filter position for each calibration sample , it becomes possible to determine the filter position preliminary . Hereby, its position, be it absolute or relative ( relative being in relation to the theoretical mean value of the filter channel position) , does not affect this determination .

In a second step S2 of the method, at least two stimuli are chosen and in a third step S3 applied on samples of the optical sensor device using a LED . These stimuli could vary in nature , such as light of di f ferent wavelengths , intensities , or other properties . In the context of optical sensors, stimuli often refer to light signals or pulses. E.g., a Light Emitting Diode (LED) can be used to generate these light signals. The LED can produce different stimuli, such as varying the intensity, color, or duration of the light, and these stimuli can be applied to the optical sensor for various purposes, such as testing or calibration .

Utilizing a white LED is a viable approach, given that the channel sensitivity variation of the white LED is already relatively low. It is therefore reasonable to use this reading as a baseline for sensitivity measurements. For numerous other filter shapes, the best outcomes may be obtained by employing a combination of a white LED and a color LED. Therefore, any kind of combination of those might be used. Any readings obtained from the device when subjected to these stimuli will be adjusted accordingly by the calibration function.

The selection of the stimuli can be done with a simulation tool based on real measured spectral shapes of the device filter channel and of the stimuli, which might be selected.

The at least two stimuli for each optical test are to meet certain criteria. The accuracy that can be achieved is contingent on the selection of these stimuli. Typically, a pair of stimuli can be utilized for multiple filter channels simultaneously. For the highest level of accuracy, the number of stimuli used may be greater, e.g. three or more.

After that, in a step S4, a calibration function for calibrating the optical sensor device is determined.

Instead of employing a singular factor for calibration or adjustment of the setup, a mathematical function to encapsulate this behavior is utili zed . This function furnishes an optimal calibration factor for every conceivable filter position .

Each individual setup is characteri zed by a unique function for each optical test .

In the course of the production test , these functions then are employed to adj ust the device readings in a manner that mitigates the impact of filter shi ft and the influence of the individual optical properties of the setup and the spectral shape of the stimuli .

Firstly, the readings when both stimuli are applied on the optical sensor device samples , are measured . These readings provide the foundational data required for calibration .

Once the readings have been measured, a calibration factor for each sample of the optical sensor device is calculated . This involves using the measured readings and applying speci fic mathematical formulas or algorithms to determine the calibration factor . Each sample may have a unique calibration factor, which is indicative of its speci fic characteristics and response to the stimuli .

Following the calculation of the calibration factors , a variable of a calibration function is calculated .

This can be done either by determining the ratio of the reading of stimuli 1 to the reading of stimuli 2 of each optical sensor device sample or by determining the average of the reading of stimuli 1 and the reading of stimuli 2 of each optical sensor device sample .

Herewith, the correlation between the ratio of the device readings and the filter position must be steady . The range of this ratio should be reasonably extensive . Both readings ought to fall within a range that permits a signi ficant degree of accuracy in the device reading . The device reading, derived from one of the stimuli or the average of readings from both stimuli , should already exhibit minimal variation across the filter position range .

Alternatively, the variable of the calibration function can be calculated by determining the average of the reading of stimuli 1 and the reading of stimuli 2 of each optical sensor device sample .

For each calibration sample , two values are obtained : Y, representing the individual calibration factor, and X, representing the variable .

Finally, a calibration function is set up . This function is set up using the calibration factors that have been acquired . The calibration function serves as a mathematical model that represents the relationship between the stimuli and the response of the optical sensor device .

This can be e . g . a polynomial function . This relationship can be used to calibrate the optical sensor, ensuring that the sensor readings are adj usted during the operational phase .

Each setup, each tester site , will receive dedicated coef ficients for their individual calibration function .

The method then involves as a step S5 the determination of the property of the optical sensor device with a production test .

The process begins by applying at least two stimuli to the optical sensor device using an LED . When both stimuli are applied to the optical sensor device , production test readings are measured . Following this , the ratio of the production test reading of the first stimulus to the production test reading of the second stimulus is calculated . This ratio is then inserted into the calibration function to determine a correction factor . Finally, the property of the optical sensor device is determined by multiplying the response of the used LED with the correction factor .

This can be the device channel sensitivity independent of the filter position on a DuT . This provides a measure of the actual sensitivity of the optical sensor, which can be used to accurately interpret the readings of the optical sensor in practical applications .

Alternatively, or on top it can be the filter position using the device readings and the calibration function on a DuT in said production test .

Ultimately, for each ATE setup ( including each individual site on these setups ) , a set of coef ficients is obtained . These coef ficients are used for the calibration function of the sensitivity and the calibration function for the filter position . This comprehensive approach allows for accurate calibration of both the sensitivity and filter position for each setup .

To reduce the impact of the repeatability due to the noise of the light source , the measurements could be made several times and the average for each optical measurement could be computed .

The implementation of this method is possible even without reference samples from the laboratory from a monochromator . As described above , a spectrally flat light source can be used in this .

A spectrally flat light source enables the measurement of sensitivity with minimal impact on the filter position, applicable to most filters in the visible range . The spectrally flat light source is capable of measuring thousands of calibrated samples at a single ATE site . However, this does not permit the estimation of the filter position . Therefore , i f the filter position is the required property of the optical sensor device , a monochromator still has to be used . This method is only applicable for filter channels that fall within the light source ' s flat area . With the spectrally flat light source , the channel sensitivity can be measured with a very low impact of the filter position (below +/- 0 . 5 % ) . For the WB channel , the positive ramp of the spectrally flat light source appears to provide the best results . The increased noise of the spectrally flat light source can be of fset by averaging several measurements ( 10-30 ) for the generation of the calibration samples . With these calibration samples , all setups can be calibrated to display the same readings as the reference measurement with the spectrally flat light source . This method enables the application of the new approach independently of the support with reference samples from the laboratory .

To of fset the repeatability impact due to the light source ' s noise , multiple measurements can be conducted and the average for each optical measurement can be computed .

The creation of all samples must occur simultaneously . The measured sensitivity value for each sample and each optical test is documented in a database . Using these calibration samples , all setups can be calibrated with the new method, ensuring uni form values across all devices .

The method is applicable to all types of Ambient Light Sensors , Color, and Spectral Sensors . The precision of these sensors can be enhanced, which then can be reflected in the narrower boundaries speci fied in the Data Sheets . Furthermore , individual channels can be trimmed .

It shall be noted that the steps given above do not neces- sarily have to be carried out in the given order . The provided steps may be carried out in any other suitable order or even some or all of them at the same time . List of abbreviations :

Claims

1 . A method for calibrating and testing an optical sensor device , the method comprising the following steps :

- calculating a calibration factor for each optical sensor device sample ,

- calculating a variable of a calibration function,

- setting up of the calibration function of the acquired calibration factors ,

- determining property of the optical sensor device with a production test ,

- applying the at least two stimuli on the optical sensor device using a LED,

2 . The method for calibrating and testing an optical sensor device according to claim 1 , wherein the property of the optical sensor device is a channel sensitivity .

3 . The method for calibrating and testing an optical sensor device according to claim 1 , wherein the property of the optical sensor device is a filter position .

4 . The method for calibrating and testing an optical sensor device according to any of the preceding claims , wherein for the preliminary testing of the optical sensor device samples a monochromator is used .

5 . The method for calibrating and testing an optical sensor device according to any one of claims 1 to 3 , wherein for the preliminary testing of the optical sensor device samples a spectrally flat light source is used .

6 . The method for calibrating and testing an optical sensor device according to any one of the preceding claims , wherein the calibration function is polynomial .

7 . The method for calibrating and testing an optical sensor device according to any one of the preceding claims , wherein an individual calibration function is assigned to each optical sensor device setup .

8 . The method for calibrating and testing an optical sensor device according to any one of the preceding claims , wherein a ratio between the readings , when the stimuli are applied during the determination of the coef ficients of the calibration function, and the filter position is steady .

9 . The method for calibrating and testing an optical sensor device according to any one of the preceding claims , wherein a light source used for testing and calibrating the optical sensor device is a white LED .

10 . The method for calibrating and testing an optical sensor device according to any one of the preceding claims , wherein a light source for testing and calibrating the optical sensor device is a color LED .

11 . The method for calibrating and testing an optical sensor device according to any one of the preceding claims , wherein a light source for testing and calibrating the optical sensor device is a combination of at least two color LEDs .

12 . The method for calibrating and testing an optical sensor device according to any one of the preceding claims , wherein the method is conducted at least two times on the same optical sensor device and the average of the resulting properties is taken as the optical sensor device property .

13 . The method for calibrating and testing an optical sensor device according to any one of the preceding claims , wherein the variable of the calibration function is calculated by determining the ratio of the reading of stimuli 1 to the reading of stimuli 2 of each optical sensor device s amp 1 e .

14 . The method for calibrating and testing an optical sensor device according to any one of claims 1 to 12 , wherein the variable of the calibration function is calculated by determining the average of the reading of stimuli 1 and the reading of stimuli 2 of each optical sensor device sample .

15 . An apparatus for calibrating and testing an optical sensor device , the apparatus comprising : a LED configured to apply at least two stimuli on the optical sensor device , a measurement unit configured to measure the readings and the production test readings when both stimuli are applied on the optical sensor device , and a processing unit configured to calculate a variable of a calibration function, and to determine a correction factor by inserting the ratio of the production test readings into a calibration function and to determine a property of the optical sensor device by multiplying the response of the LED with the correction factor .