WO2024055233A1

WO2024055233A1 - Optical sensor for proximity and ambient light detection under display

Info

Publication number: WO2024055233A1
Application number: PCT/CN2022/118994
Authority: WO
Inventors: Jun Liu; Chunming SHEN
Original assignee: Fingerprint Cards Anacatum Ip Ab
Priority date: 2022-09-15
Filing date: 2022-09-15
Publication date: 2024-03-21

Abstract

An optical sensor (100) for proximity and ambient light detection under a display (104), the optical sensor (100) comprising: a matrix (108) of photosensitive pixels, wherein a first set (200) of pixels covered by bandpass filters in the visible range of light, the first set (200) of pixels are configured for ambient light detection, wherein at least one subset of the first set (200) of pixels is covered by a bandpass filter that excludes at least part of an emission spectrum from the display (104), and wherein a second set (300) of pixels is arranged along a perimeter surrounding the first set (200) of pixels, the second set (300) of pixels being covered by an IR-bandpass filter, and an IR-light source (110) for emitting light towards the display (104) for reflection by an object (111) on the opposite side of the display (104), wherein the second set (300) of pixels are configured to detect the reflected light for object (111) proximity detection.

Description

AN OPTICAL SENSOR FOR PROXIMITY AND AMBIENT LIGHT DETECTION UNDER A DISPLAY

Field of the Invention

The present invention relates to an optical sensor for proximity and ambient light detection under a display. The present invention further relates to an electronic device comprising such optical sensor.

Background of the Invention

In newly released consumer electronic devices, such as mobile phones having large displays it is common to include proximity sensing capabilities for sensing the proximity of an object to the display. The proximity sensing is used for preventing unintended touch actions on the display as may occur when talking on the phone with a person’s face close to or even in contact with the display. Furthermore, ambient light sensing may be implemented to adjust display light settings depending on the ambient light conditions.

The trend in consumer electronic devices is to increase the size of the display and full OLED or AMOLED screens are becoming common.

However, as the size of the displays increase, the task of integrating optical sensors under the displays become more challenging.

Summary

In view of above-mentioned and other drawbacks of the prior art, it is an object of the present invention to provide an optical sensor that at least alleviates some of the drawbacks of prior art.

According to a first aspect of the invention, there is provided an optical sensor for proximity and ambient light detection under a display. The optical sensor comprises a matrix of photosensitive pixels.

The matrix comprises a first set of pixels that are covered by bandpass filters in the visible range of light. The first set of pixels are configured for ambient light detection, wherein at least one subset of the first set of pixels is covered by a bandpass filter that excludes at least part of an emission spectrum of light emitted by the display.

A second set of pixels are arranged along a perimeter surrounding the first set of pixels, the second set of pixels being covered by an infrared (IR-) bandpass filter.

In addition, an IR-light source is arranged for emitting light towards the display for reflection by an object on the opposite side of the display, wherein the second set of pixels are configured to detect the reflected light for object proximity detection.

The present invention is partly based on the arrangement of the IR channel as the outer channel surrounding the first set of pixels and with a subset of pixels with low contribution from the display emission colour. Thus, the subset of pixels in the first subset can avoid detecting the emission from the display in wavelength ranges excluded by the bandpass filter while at the same time allow for ambient light detection a least nearly independent of the emission from the display.

An improvement of the present invention is with the bandpass filters of the first set of pixels to be adapted to at least partly exclude the spectrum from emission of the display. Thus, each of the bandpass filters are adapted with wavelength transmission bands that partly, or fully, enable to prevent that the light emitted from the display emission reaches the first set of pixels. In other words, the bandpass filters that cover the first set of pixels are tailored so that the transmission peaks of the bandpass filters fall in between emission peaks of the display. Preferably, there is no overlap of transmission peaks and emission peaks at half maximum of the peaks. This further allows for improved distinction between ambient light and display emission.

Ambient light detection generally includes detecting the light conditions such as intensity, spectrum, colour temperature of the light surrounding, or in the vicinity of the sensor. Ambient light detection may be used for tuning display emission settings such as intensity and colour temperature. The ambient light detection may be given as a luminance or intensity value at different wavelengths.

Proximity detection is detection of objects near the surface of the display, or near the sensor. This may be realized by analysing the reflected light from the IR-source. For example, a strong reflection intensity indicates that an object is closer than if the reflection intensity is weaker.

The photodetectors, or generally pixels, of the light sensor are individually controllable photodetectors configured to detect an amount of incoming light and to generate an electric signal indicative of the light received by the detector. The photodetectors may be based on thin-film transistor (TFT) technology. Other suitable types of photodetector technology include CMOS or CCD technology with associated control circuitry. The operation and control of such photodetectors can be assumed to be known and will not be discussed in detail herein.

The light source may be for example a light-emitting diode (LEDs) , organic light-emitting diode (OLEDs) , or other equally applicable light emitters or light sources.

In one embodiment, the optical sensor may comprise a third set of pixels arranged along a perimeter surrounding the first set of pixels, the third set of pixels being covered by an UV-bandpass filter. The third set of pixels is preferably configured for ambient ultraviolet (UV) light detection. The third set of pixels may fully enclose the first set of pixels with no gaps between neighbouring pixels.

The third set of pixels for UV light detection allows for improved characterization of the ambient light, especially related to sun light detection which contain a high UV-light component. It further provides the ability for the optical sensor to separately detect the UV-light from other wavelengths of light. In this way, there is no need to separate the contributions of display light and sunlight on the visible channels to calculate the ambient light signal. Instead, one can use a known, predetermined, ratio between the UV component in a full wavelength signal of ambient light to calculate the ambient light value or level or intensity.

The third set of pixels may be arranged along a perimeter between the perimeters of the second set of pixels and the first set of pixels. Thus, the second set of pixels may be located closer to the edges of the pixel matrix compared to the third set of pixels. Alternatively, the second set of pixels may be arranged along a perimeter between the perimeters of the third set of pixels and the first set of pixels so that the third set of pixels may be located closer to the edges of the pixel matrix compared to the second set of pixels.

In one embodiment, the optical sensor may comprise a fourth set of pixels arranged along a perimeter surrounding the first set of pixels, the fourth set of pixels being covered by a bandpass filter in the red range of wavelengths. For example, the bandpass filter in the red may have a centre wavelength around 710 nm. The bandpass filter covering the fourth set of pixels should be configured to prevent most of the display emission to reach the fourth set of pixels while allowing most of the contribution from ambient light in the bandpass filter transmission range.

The sequence of the second set, the third set, and the fourth set of pixels depends on the specific application at hand. Any one of the second set, the third set, and the fourth set of pixels may be arranged along a perimeter closest to the first set of pixels. Similarly, any one of the second set, the third set, and the fourth set of pixels may be arranged along a perimeter second closest to the first set of pixels. Any one of the second set, the third set, and the fourth set of pixels may be arranged along a perimeter closest to the edge of the pixel array, i.e., furthest from the first set of pixels.

In one example implementation, the second set of pixels may be arranged along the edge of the pixel array to surround the first set of pixels. For example, the second set of pixels may be arranged at the outmost areas of the pixel matrix. The further out the IR-pixels, i.e., the second set of pixels are located, the perimeter become larger thereby allowing more pixels in the second set. A larger sensing area is advantageously provided for the lower quantum efficiency channel, the IR-channel, compared with the visible channels of the first set of pixels. A larger sensing area thereby provides to compensate for a lower photoelectron transfer efficiency, or quantum efficiency, of a sensor for a specific wavelength range.

Any one of the second set, the third set, and the fourth set of pixels sets of pixels may fully enclose the first set of pixels with no gaps between neighbouring pixels in the respective set.

Preferably, the first set of pixels are covered by at least three different types of bandpass filters with different wavelength transmission bands. This allows for three different channels in the visible range of wavelengths that can be configured for ambient light luminance and colour temperature detection.

In one embodiment, adjacent sets of pixels are separated by pixel channel without any optical filter or a black channel with no signal output. This advantageously reduces the risk of manufacture induced crosstalk between channels.

In a further embodiment, the optical sensor may comprise pixels not covered by optical filters or black pixels with no signal output at the corners of the pixel matrix.

In one embodiment, the second set of pixels may be configured as multiple IR-channels for the optical sensor, wherein the optical sensor is configured to process detection signals from the multiple IR-channels for gesture detection. Thus, the second set of pixels may advantageously provide for both proximity detection and gesture detection due to the multiple IR-channels. For example, the IR-channels may constitute the pixels of the second set along a respective edge of the sensor chip or pixel matrix. Gesture detection may be used for detecting a movement or gesture made by a hand or object detectable by the optical sensor.

In one embodiment, the optical sensor may comprise an optical refractive index film on the bandpass filters to reduce the maximum incident angle on the pixels to less than 30 degrees. The transmittance of bandpass filters at the designed peak transmission wavelength typically varies depending on incident angles, and the variation is especially large for incident angles larger than 30 degrees. To avoid this, adding high refractive index on bandpass filter, e.g., SiNx with refractive index of 2.02, can reduce the maximum incident angle on the bandpass filter to less than 30 degrees.

In one embodiment, the bandpass filters with different transmission wavelength bands are configured so that they have no overlap at wavelengths with half maximum intensity. This advantageously provides for reduced or no crosstalk between different channels.

In one embodiment, the second set of pixels and a subset of the first set of pixels covered by a bandpass filter in the green range of wavelengths are jointly configured for heartrate and blood oxygen signal detection of an object. Advantageously, the optical sensor with several herein described channels also allow for further functions and analysis, such as heartrate and blood oxygen signal detection which can be used for liveness detection or health analysis tasks for living beings.

Preferably, the second set of pixels is further configured for ambient IR light detection.

In one example embodiment, the first set of pixels may be covered by the bandpass filters to form RGBY-blocks, each comprising a red channel, a green channel, a blue channel, and a yellow channel.

The bandpass filters have a spectral transmission band corresponding to a color of light thereby being configured to allow the transmission of light in a specific spectral band.

According to a second aspect of the invention, there is provided an electronic device comprising: an at least partly transparent display panel; and the optical sensor according to any one of the herein described embodiments.

The display may for example be based on OLED, pol-less OLED or OLED with circular polarizer, AMOLED, LCD, μLED and similar technologies.

The electronic device may be e.g., a mobile device such as a mobile phone (e.g., Smart Phone) , a tablet, a phablet, etc.

Further effects and features of the second aspect of the invention are largely analogous to those described above in connection with the first aspect of the invention.

Further features of, and advantages with, the present invention will become apparent when studying the appended claims and the following description. The skilled person realize that different features of the present invention may be combined to create embodiments other than those described in the following, without departing from the scope of the present invention.

Brief Description of the Drawings

These and other aspects of the present invention will now be described in more detail, with reference to the appended drawings showing an example embodiment of the invention, wherein:

Fig. 1 schematically illustrates an example of an electronic device according to embodiments of the invention;

Fig. 2 is a schematic box diagram of an electronic device according to embodiments of the invention;

Fig. 3 conceptually illustrates an optical sensor arranged under an at least partially transparent display panel according to an embodiment of the invention;

Fig. 4A conceptually illustrates an example pixel layout according to an embodiment of the invention;

Fig. 4B conceptually illustrates an example pixel layout according to an embodiment of the invention;

Fig. 4C conceptually illustrates an example pixel layout according to an embodiment of the invention;

Fig. 5 is a conceptual cross-section of a pixel matrix covered by bandpass filters;

Fig. 6 conceptually illustrates gesture detection according to an embodiment of the invention;

Fig. 7 is a conceptual side-view of the pixel array having a bandpass filter arrangement covering the pixel array; and

Fig. 8 shows an example spectrum for a multiple bandpass filter optical sensor according to an embodiment of the invention.

Detailed Description of Example Embodiments

In the present detailed description, various embodiments of the optical sensor according to the present invention are mainly described with reference to an optical sensor arranged under a display panel. However, it should be noted that the described optical sensor also may be used in other applications such as in an optical sensor located under other types of covers including light emitting pixels.

Turning now to the drawings and in particular to Fig. 1, there is schematically illustrated an example of an electronic device configured to apply the concept according to the present disclosure, in the form of a mobile device 101 with an under-display optical sensor 100 and a display panel 104 with a touch screen interface 106. The optical proximity sensor 100 may, for example, be used for detecting the presence of an object to stop a touch function of the touch screen interface 106 in case of a detected object near the display panel 104 and for ambient light detection.

It should furthermore be noted that the invention may be applicable in relation to any other type of electronic devices comprising display panels, such as a laptop, a tablet computer, etc.

Fig. 2 is a schematic box diagram of an electronic device according to embodiments of the invention. The electronic device 20 comprises a display panel 24 and an optical sensor 100 conceptually illustrated to be arranged under the display panel 24 according to embodiments of the invention. Furthermore, the electronic device 20 comprises processing circuitry such as control unit 22. The control unit 22 may be stand-alone control unit of the electronic device 202, e.g., a device controller. Alternatively, the control unit 22 may be comprised in the optical sensor 100.

The control unit 22 is configured to receive a signal indicative of a detected object from the optical sensor 100 or indicative of ambient light conditions.

Based on the received signal the control unit 22 is configured to determine if a detected object is near the surface of the display panel 24, and if this is case, disable a touch function of the display panel 24. Still further, based on a received signal the control unit 22 is configured to determine ambient light conditions and to adjust display emission settings based on the detected ambient light conditions.

Fig. 3 conceptually illustrates an optical sensor 100 arranged under an at least partially transparent display panel 104. The display panel 104 comprises a display substrate 104a including display pixels and a cover glass 104b arranged to cover the display substrate 104a. The cover glass 104b provides protection for the pixels of the display substrate 104a.

The optical sensor 100 is arranged on one side the display panel 104 to detect the presence of an object 111 on the opposite side of the at least partially transparent display panel 104.

The optical sensor may be for example a TFT, CMOS, or CCD sensor and comprises an array or matrix of photodetectors configured to detect light transmitted from the object 111 on the opposite side of the at least partially transparent display panel 104. The configuration and layout of the pixels of the pixel matrix 108 will be described with reference to subsequent drawings. For completeness, the matrix 108 of photodetectors and a light source 110 are here shown on a sensor die 112 supported or arranged on an optical sensor module substrate 113 attached to a bracket 114 holding the optical sensor 100 mechanically in place under the display panel 104.

The light source 110 is arranged to transmit light towards the at least partially transparent display panel 104 for reflection by the object 111 on the opposite side of the display panel 104. The light source 110 is an infrared light source and may for example be a light emitting diode.

Although not shown in the figures, the optical sensor 100 may comprises a lenses or collimators arranged between the pixel matrix 108 and the at least partly transparent display panel 104 to focus light onto the pixel matrix 108.

Similarly, to narrow the beam and tailor the field of illumination, collimators or similar light redirecting elements may be arranged between the light source 110 and the at least partially transparent display panel 104. The collimator may cover the light source 110 and may be attached to the light source 110.

In the example embodiment, the optical sensor 100 includes an opaque layer 116 between the display substrate 104a and the bracket 114. The opaque layer 116 is arranged between the light source 110 and the display panel 104 and between the pixel matrix 108 and the at least partially transparent display panel 104. The opaque layer 116 comprises an opening 142 aligned with the light source 110 and an opening 143 aligned with the pixel matrix 108 to allow for emitted light to reach the at least partially transparent display panel 104 and the object 111 and to reach the pixel matrix 108 from the ambient environment. The opaque layer 116 may be a so-called cushion layer which is used as a protection film between the display and sensor bracket 114 to dampen mechanical impacts on the display 104.

An opaque light blocking element 117, or wall, is arranged on the die 112 between the pixel matrix 108 and the light source 110 to separate the light source 110 from the pixel matrix 108. This prevents or reduces direct stray light from the light source 110 from reaching the pixel matrix 108.

In use, the light source 110 is configured to emit light towards the at least partly transparent display panel 104, and one set of pixels of the pixel matrix 108 is configured to detect reflections of the emitted light transmitted from an object 111 at the at least partly transparent display panel 104. An intensity level of the detected reflected light is indicative of the presence of an object 111 on the opposite side of the at least partly transparent display panel 104 touching or being close to a sensing surface 121 of the cover glass 104b. Further, a first set of pixels are configured to detect ambient light.

Fig. 4A conceptually illustrates an example pixel layout according to embodiments of the invention.

The pixel matrix 108 comprises a first set 200 of pixels covered by bandpass filters in the visible range of light. The first set 200 of pixels are configured for ambient light detection and at least one subset of the first set of pixels is covered by a bandpass filter that excludes at least part of an emission spectrum from the display. In other words, the bandpass is adapted or designed based on the emission spectrum of the display pixels.

The first set 200 of pixels are in the centre area or centre portion of the pixel matrix 108. Although here only indicated by dashed lines, the first set

200 of pixels preferably cover the entire centre portion of the pixel matrix in a repetitive pattern of pixel blocks 202. It is preferred that the pixels of the first set of pixels 200 are covered by at least three different types of bandpass filters with different wavelength transmission bands. Thus, the first set 200 of pixels may form three different channels, such as the common RGB channels.

In a preferred embodiment, the bandpass filters of the first set of pixels 200 are adapted to at least partly exclude the spectrum from display emission of the display. In other words, the bandpass filters of the first set 200 of pixels are tailored so that the emission from the display 104 is prevented from reaching the pixels of the first set, or at such that a majority of the intensity of the light emitted from the display 104 is not detected by the pixels of the first set 200. For example, the peaks of the bandpass transmission spectrum for the first set of pixels fall between peaks of the emission spectrum of the display.

In this example embodiment, the pixel blocks 202, formed by having different bandpass filters covering the pixels of the pixel block, are RGBY-blocks, each being comprised in a respective red channel, green channel, blue channel, and a yellow channel. Each channel includes pixel with a respective bandpass filter element covering the pixel with the respective bandpass transmission wavelength band. For example, the red channel may have pixels covered by a bandpass filter with transmission peak at about 623 nm, the green channel may have pixels covered by a bandpass filter with transmission peak at about 523 nm, the blue channel may have pixels covered by a bandpass filter with transmission peak at about 450 nm, and the yellow channel may have pixels covered by a bandpass filter with transmission peak at about 580 nm.

The first set 200 of pixels may be configured for ambient light luminance and colour temperature detection. However, as will be described further below, other pixel sets may contribute to ambient light detection.

Generally, the control unit 22 shown in fig. 2 is configured to receive a sensing signal from the optical sensor 100 indicating the intensity of light of the different colors as detected by the photodetector pixels of for example the first set, or a combination of pixel sets. The control unit 22 calculates the color temperature and ambient light intensity based on the sensing signals received from the optical sensor 100. The control unit 22 evaluates the color temperature and ambient light intensity in view of predetermined display settings that are preferred for a given color temperature and/or ambient light intensity according to a model or look-up table. Subsequently, the control unit 22 controls a display intensity and/or display color temperature based on the sensing signal by sensing control signals to the display. More precisely, the control unit 22 controls the pixels of the display 104 to adjust the display intensity and/or display color temperature.

Turning again to fig. 4A, the pixel matrix comprises a second set 300 of pixels arranged along a perimeter surrounding the first set 200 of pixels. The second set of pixels being are covered by an IR-bandpass filter. The IR-bandpass filter may have a transmission peak at about 940 nm. In use, the control unit 22 may be configured to control the infrared light source 110 to emit infrared light. The second set of pixels 300 of the optical sensor 100 detects reflected light caused by the emitted infrared light. The control unit 22 of fig. 2 is configured to receive a signal from the optical sensor 100 indicating the intensity of the detected infrared light as detected by the IR channel formed from the second set of pixels 300. If the detected infrared intensity exceeds a threshold, the control unit 22 may be configured to control a touch display of the at least partially transparent display panel 104 to disable a touch function.

In other words, the IR-light source 110 in fig. 3 emits light towards the display 104 for reflection by an object 111 on the opposite side of the display. The second set 300 of pixels are configured to detect the reflected light for object proximity detection. The second set of pixels may additionally be configured for ambient IR light detection in conjunction with proximity sensing.

Further, a third set 400 of pixels arranged along a perimeter surrounding the first set 200 of pixels, the third set 400 of pixels being covered by an UV-bandpass filter. The third set 400 of pixels is preferably configured for ambient UV light detection. The UV bandpass filter may have a transmission peak at about 380 nm.

Still further, in this example embodiment, a fourth set 500 of pixels arranged along a perimeter surrounding the first set of pixels, the fourth set 500 of pixels being covered by a bandpass filter in the red range of wavelengths. The bandpass filter of the fourth set 500 of pixels may have a transmission peak at about 710 nm.

At least one of the second set 300, the third set 400 and the fourth set 500 of pixels are arranged along the edge of the pixel array. In this example embodiment, each of the sets 300-500 are arranged along the edges, parallel with the edges of the pixel matrix 108 at the outermost areas of the pixel matrix 108 so that all the

sets

300, 400, 500 surround the first set 200 of pixels located in the central areas of the pixel matrix 108. The second set 300, the third set 400, and the fourth set 500 are concentrically arranged in the pixel matrix with the first set 200 of pixels in the centre.

One of the second set, the third set and the fourth set of pixels is arranged at the outmost areas of the pixel matrix 108. In this example embodiment of fig. 4A the second set 300 of pixels are located at the outermost areas, closest to the outer edges 130 of the pixel matrix. The second set 300 of pixels may be the outermost pixels of the pixel matrix 108.

Fig. 5 is a conceptual cross-section of a set of pixels matrix 108

However, any one of the second set, the third set and the fourth set of pixels may be arranged at as the outermost pixels of the pixel matrix 108. As shown in fig. 4B, the third set 400 of pixels are arranged as the outermost pixels of the pixel matrix 108 and the second set 300 of pixels being interleaved between the third set 400 and the fourth set 500 with the fourth set being the innermost set closest to the second set 300.

Alternatively, as shown in fig. 4C, the fourth set 500 of pixels are arranged as the outermost pixels of the pixel matrix 108 with the second set 300 of pixels being the innermost set closest to the first set of pixels 200. The third set of pixels 400 are interleaved between the innermost second set 300 and the outermost fourth set 500. Other configurations and relative orders of the set of pixels are also envisaged.

To reduce or avoid crosstalk between the sets of

pixels

100, 200, 300, 400, 500, adjacent sets of pixels are separated by a pixel channel 600 without any optical filter or a black channel with no signal output. If the channel is a clear channel without any optical filter can detect the full range of wavelengths. For example, the second set 300 of pixels and the third set 400 of pixels are separated by black pixels 600 so that the second set 300 of pixels and the third set 400 of pixels are not directly adjacent. Similarly, the third set 400 of pixels and the fourth set 400 of pixels are separated by black pixels 600. Analogously, the pixel matrix 108 comprises corner pixels 150 not covered by optical filters or black pixels 150 with no signal output at the corners of the pixel matrix 108. The size of the gap provided by the black pixels 600 between sets of pixels may be in the other of 1, 2, 3, 4, or 5 pixels. The width w of the band of pixels for each of the second set, third set, and fourth set of pixels that surround the first set of pixels, may be in the order of 5-20 pixels, such as 8, 9, 10, 11, or 12 pixels. Furthermore, the pixels of the first set 200 of pixels, here exemplified by

pixels

200a, 200b, 200c, and 200d are separated by black or clear pixels 600. It should further be noted that further black or clear areas surrounding the illustrated pixel matrix 108 are envisaged and its size and configuration depend on the specific implementation at hand.

Fig. 5 is a conceptual cross-section of part of a pixel matrix covered by bandpass filters. The pixels 301 of the second set of pixels 300 are covered by bandpass filter 301a with wavelength transmission band that is associated with the second set 300 of pixels to form the intended channel. The black pixels 600 that are interleaved between the second set 300 of pixels 301 and the third set of pixels 401 may or may not be covered by a filter.

Adjacent the black pixels 600 is the third set of pixels 401 covered by its respective bandpass filter 401a. The black pixels 600 that are interleaved between the third set 400 of pixels 301 and the fourth set of pixels 501 may or may not be covered by a filter. Adjacent the black pixels 600 is the fourth set of pixels 501 covered by its respective bandpass filter 501a.

The pixel block 202 of the first set 200 here only indicates two

pixels

200a and 200b, however, as indicated in fig. 4A, the block 202 includes

additional pixels

200c and 200d not visible in fig. 5. Each of the

pixels

200a, 200b, 200c, and 200d of the block are covered by a

respective bandpass filter

201a, 201b, 201c, 201d, having distinctly different transmission bands so that four different channels are formed. The

bandpass filters

301a, 401a, 501a, 201a, 201b, 201c, 201d covering the respective different sets of pixels, and the pixels of the block 202 preferably have distinctly different transmission bands so that seven different channels are formed. Note that the cross-section does not cover the entire side-to-side of the pixel matrix 108 but is cut at the pixel 200b in fig. 4A.

The black corner pixels 150 separates subsets of the second set of pixels or whichever set being arranged at the outermost areas of the pixel matrix 108. In this way, multiple channels of the second set of pixels, or whichever set being arranged at the outermost areas of the pixel matrix 108 are formed. In this example embodiment, the second set 300 of pixels 300 are interrupted by the corner pixels 150 and is configured as multiple IR-channels for the optical sensor. In this case four

channels

300a, 300b, 300c, 300d, pairwise vertically and horizontally oriented across the pixel matrix. The outermost pixels here being the second set 300 provides the best candidate set for gesture detection since the channels can be most displaced from each other compared to channels of the other sets. Using the

channels

300a, 300b, 300c, 300d, the optical sensor is configured to process detection signals from the multiple IR-channels for gesture detection.

Gesture detection can be implemented using different schemes, but for the sake of completeness, example gesture detection is conceptually laid out in fig. 6.

With a coordinate system where the light source 110 is in the centre at origin (0, 0, 0) , the object gesture is defined by object 111 centre position (x, y, z) and a tilt gesture is a rotation with rotation angle in relation to x axis (rx) and y axis (ry) following right-handed spiral rule. The reflected IR light from an object surface is captured by the

IR receiver channels

300a, 300b, 300c, and 300d which are located at different positions (up/down/left/right) in the pixel array 108. The object gesture can be estimated based on detecting differences in intensities between the channels and time variations in the detected signals based on a prior made signal calibration for different predefined gestures.

In some embodiments, the second set 300 of pixels covered by IR bandpass filter are used together with a subset of the first set of pixels covered by a bandpass filter in the green range of wavelengths for heartrate and blood oxygen signal detection of an object. Green light, e.g., in the approximate wavelength range of 495 nm to 570 nm, is suitable for heartrate detection since it is well absorbed by haemoglobin (hg) Hb absorption detection. Furthermore, the absorption of IR light in blood depends on the oxygen level in the blood. Thus, the amount of IR light reflected by the user’s body can be used for blood oxygen level detection.

A typical bandpass filter has a dependence of its transmittance as a function of incident angle. Fig. 7 is a conceptual side-view of the pixel array 108 having a bandpass filter arrangement 602 covering the pixel array 108. The bandpass filter arrangement represents one or all the herein discussed bandpass filters and the illustration is only conceptual. Further, an optical refractive index film 604 is arranged on the bandpass filters 600. The optical refractive index film which may for example be a silicon-nitride film may have a refractive index of at least 2 to reduce the maximum incident angle on the pixels 108 to less than 30 degrees, thereby eliminating or reducing the effect of the incident angle dependence of the bandpass filter 602

Fig. 8 shows an example spectrum for a multiple bandpass filter optical sensor 100 having seven channels. Firstly, in the first set 200 of pixels the bandpass filters provide the transmission peaks at 450nm, 523nm, 580nm, and 623nm of a RGBY-block 202 of pixels. In other words, the first set 200 of pixels provides four distinct channels for the multiple bandpass filter optical sensor 100.

Further, the second set 300 of pixels are covered by an IR bandpass filter with transmission peak at 940 nm, providing an IR channel.

In the third set 400 of pixels the respective bandpass filter provides the transmission peak at 380nm thereby providing an ultraviolet channel for the multiple bandpass filter optical sensor 100.

In the fourth set 400 of pixels the respective bandpass filter provides the transmission peak at 710nm thereby providing a further red channel for the multiple bandpass filter optical sensor 100. This further red channel is operative at longer wavelengths than the red channel of the first set 200 of pixels.

With further reference to fig. 8, the bandpass filters of the optical sensor 100 with different transmission wavelength bands are configured so that they have no overlap at wavelengths with half maximum intensity indicated by the dashed line 702.

In preferred embodiments, at least one channel in the visible range has low contribution from display emission colour. The transmission peaks at 580nm and 710nm for the subset of the first set of pixels and the fourth set of pixels have low contribution from typical display emission, but instead with a majority of signal contribution from ambient light. The peaks at 380nm and 940nm for the third set of pixels and the second set of pixels respectively, can differentiate if the ambient light source is daylight with high UV and IR components, or white LED and fluorescent light with negligible UV and IR components.

Overall, the herein described optical sensor with an especially advantageous layout and combination of multiple bandpass filters provides for a vast number of applications in ambient light detection, proximity detection, and liveness detection.

The IR light source 110 preferably has the emission peak wavelength at or near the transmission peak wavelength of the bandpass filter of the second set 300 of pixels.

A control unit may include a microprocessor, microcontroller, programmable digital signal processor or another programmable device. The control unit may also, or instead, include an application specific integrated circuit, a programmable gate array or programmable array logic, a programmable logic device, or a digital signal processor. Where the control unit includes a programmable device such as the microprocessor, microcontroller or programmable digital signal processor mentioned above, the processor may further include computer executable code that controls operation of the programmable device. It should be understood that all or some parts of the functionality provided by means of the control unit (or generally discussed as “processing circuitry” ) may be at least partly integrated with the optical sensor.

Even though the invention has been described with reference to specific exemplifying embodiments thereof, many different alterations, modifications and the like will become apparent for those skilled in the art. Also, it should be noted that parts of the imaging device and method for manufacturing the imaging device may be omitted, interchanged or arranged in various ways, the imaging device yet being able to perform the functionality of the present invention.

Sizes and dimensions of various components and elements shown in the drawings are not necessarily to scale and are generally selected for clarity in the drawings. For example, the thickness of filters, displays, opaque layers, etc., may not correspond to a real implementation.

Additionally, variations to the disclosed embodiments can be understood and effected by the skilled person in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims. In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain measures are recited in mutually different dependent claims does not indicate that a combination of these measures cannot be used to advantage.

Claims

An optical sensor for proximity and ambient light detection under a display, the optical sensor comprising:

a matrix of photosensitive pixels, wherein

a first set of pixels covered by bandpass filters in the visible range of light, the first set of pixels are configured for ambient light detection, wherein at least one subset of the first set of pixels is covered by a bandpass filter that excludes at least part of an emission spectrum from the display, and wherein

a second set of pixels is arranged along a perimeter surrounding the first set of pixels, the second set of pixels being covered by an IR-bandpass filter, and

an IR-light source for emitting light towards the display for reflection by an object on the opposite side of the display, wherein the second set of pixels are configured to detect the reflected light for object proximity detection.
The optical sensor according to claim 1, comprising a third set of pixels arranged along a perimeter surrounding the first set of pixels, the third set of pixels being covered by an UV-bandpass filter.
The optical sensor according to claim 2, wherein the third set of pixels is configured for ambient UV light detection.
The optical sensor according to any one of the preceding claims, comprising a fourth set of pixels arranged along a perimeter surrounding the first set of pixels, the fourth set of pixels being covered by a bandpass filter in the red (710nm) range of wavelengths.
The optical sensor according to claim 4, wherein at least one of the second set, the third set and the fourth set of pixels are arranged along the edge of the pixel array.
The optical sensor according to any one of claims 4 and 5, wherein one of the second set, the third set and the fourth set of pixels is arranged at the outmost areas of the pixel matrix.
The optical sensor according to any one of the preceding claims, wherein the first set of pixels are covered by at least three different types of bandpass filters with different wavelength transmission bands.
The optical sensor according to any one of the preceding claims, wherein adjacent sets of pixels are separated by pixel channel without any optical filter or a black channel with no signal output.
The optical sensor according to any one of the preceding claims, comprising pixels not covered by optical filters or black pixels with no signal output at the corners of the pixel matrix.
The optical sensor according to any one of the preceding claims, wherein the second set of pixels is configured as multiple IR-channels for the optical sensor, wherein the optical sensor is configured to process detection signals from the multiple IR-channels for gesture detection.
The optical sensor according to any one of the preceding claims, comprising an optical refractive index film on the bandpass filters to reduce the maximum incident angle on the pixels to less than 30 degrees.
The optical sensor according to any one of the preceding claims, wherein bandpass filters of the optical sensor with different transmission wavelength bands are configured so that they have no overlap at wavelengths with half maximum intensity.
The optical sensor according to any one of the preceding claims, wherein the first set of pixels are configured for ambient light luminance and colour temperature detection.
The optical sensor according to any one of the preceding claims, wherein the second set of pixels and a subset of the first set of pixels covered by a bandpass filter in the green range of wavelengths are configured for heartrate and blood oxygen signal detection of an object.
The optical sensor according to any one of the preceding claims, wherein the second set of pixels is configured for ambient IR light detection.
The optical sensor according to any one of the preceding claims, wherein the first set of pixels are covered by the bandpass filters to form RGBY-blocks, each comprising a red channel, a green channel, a blue channel, and a yellow channel.
The optical sensor according to any one of the preceding claims, wherein the bandpass filters of the first set of pixels are adapted to at least partly exclude the spectrum from display emission of the display.
An electronic device comprising:

an at least partly transparent display panel; and

the optical sensor according to any one of the preceding claims.
The electronic device according to claim 18, being a mobile device.