WO2021159298A1

WO2021159298A1 - Method of driving display device, display device driving apparatus, display device, and display method

Info

Publication number: WO2021159298A1
Application number: PCT/CN2020/074841
Authority: WO
Inventors: Yasuyuki Teranishi; Hiroshi Mizuhashi
Original assignee: Huawei Technologies Co., Ltd.
Priority date: 2020-02-12
Filing date: 2020-02-12
Publication date: 2021-08-19
Also published as: CN115066720A

Abstract

A method of driving a display device(100) that improves the quality of a captured image while maintaining the resolution of OLEDs is provided. The display device(100) includes a storage unit storing a plurality of frame patterns to be displayed in an object sensing zone where an object is detected, and light receiving elements that detect the object based on light from the light emitting elements. The method includes, for each of the plurality of frame patterns: scanning the pattern image, the scanning including stopping emission of light emitting elements on a part of emission signal lines arranged along a first axis within a displayed frame pattern, and shifting the emission signal lines to be disabled for emission along a second axis within the displayed frame pattern; and by the light receiving elements, measuring reflected light from the object based on the emission of the light emitting elements.

Description

METHOD OF DRIVING DISPLAY DEVICE, DISPLAY DEVICE DRIVING APPARATUS, DISPLAY DEVICE, AND DISPLAY METHOD

TECHNICAL FIELD

Embodiments of the present application relate to an image sensing function, and in particular, to a method of driving a photo detector, a photo detector driving apparatus, a method of display and a display device.

BACKGROUND

Currently, pixel unit driving circuits used for OLEDs of portable terminals include a 6T1C (6 transistors and 1 capacitor) circuit and a 7T1C (7 transistors and 1 capacitor) circuit for each pixel. As the number of transistors implemented for one pixel increases in this way, the degree of integration increases and the corresponding resolution decreases.

In addition, an image sensor that converts light into an electrical signal is mounted in a portable terminal. Specifically, an in-cell image sensor in which a part (or all) of an image sensor mechanism for converting light into an electrical signal, such as a CMOS sensor, is incorporated in a TFT of the OLED is known. Typically, an image sensor includes an active pixel sensor (APS) that increases the gain of the signal on a pixel-by-pixel basis to increase the signal to noise ratio (S/N ratio) . The structure of the APS includes, for each pixel, three TFTs: a reset transistor for resetting the voltage of a photodiode (PD) as a light receiving element, an amplifier transistor for amplifying the gain, and a transistor for reading a signal (or a reading transistor) . Therefore, when a pixel circuit is configured by implementing both of a pixel unit driving circuit, such as a 6T1C circuit or a 7T1C circuit, and an image sensor for one pixel of the OLED, the degree of circuit integration is further increased. Such a complicated circuit configuration adversely affects the corresponding resolution and reduces the space for adding other devices. Therefore, in order to simplify the circuit configuration, referring to FIG. 2, it is known to remove the reset transistor and the amplifier transistor from the image sensor to provide a configuration (1T1PD) including only the read transistor and the photodiode. However, the configuration without the amplifier transistor reduces the S/N ratio.

SUMMARY

It is an object of the present disclosure to improve the quality of a captured image while maintaining the resolution of the OLED.

A first aspect provides a method of driving a display device, wherein the display device includes a plurality of emission signal lines that are arranged along a first axis and each supplies an emission signal to a plurality of light emitting elements, a plurality of data signal lines that are arranged along a second axis and supply a data signal to cause each of the plurality of light emitting elements to emit light, a storage unit that are storing a plurality of frame patterns to be displayed in an object sensing zone where an object is detected, and light receiving elements that detect the target based on light from the light emitting elements, wherein the plurality of frame patterns is designed according to the object, and wherein the first axis and the second axis are perpendicular, the method including, for each of the plurality of frame patterns:

scanning the pattern image, the scanning including

disabling emission of light emitting elements arranged along a part of the emission signal lines within the displayed frame pattern, and

shifting the emission signal lines to be disabled for emission along the second axis within the displayed frame pattern; and

by the light receiving elements, measuring reflected light from the object based on the emission of the light emitting elements.

According to this implementation, for each of the plurality of frame patterns, at the time of scanning the pattern image, emission of the light emitting elements arranged along a part of the emission signal lines is stopped within the displayed frame pattern, and the emission signal lines to be disabled for emission are shifted along the second axis within the displayed frame pattern. Therefore, the combination of the pattern lighting technique and the CDM driving method improves the quality of a captured image while maintaining the resolution of the OLEDs.

With reference to a possible implementation of the first aspect, the scanning includes scanning the pattern image by only light emitting elements within the object sensing zone.

According to this implementation, since patterns are scanned only by the light emitting elements in the object sensing zone, wasteful power consumption is avoided.

With reference to a possible implementation of the first aspect, the stopping emission includes disabling light emitting elements outside the object sensing zone.

According to this implementation, wasteful power consumption is avoided by disabling the emission signal lines outside the object sensing zone.

With reference to a possible implementation of the first aspect, reading of the light receiving elements is controlled in response to a signal from a scan signal line for reading, and the stopping emission includes disabling scan signal lines outside the object sensing zone.

According to this implementation, reading of the light receiving elements is controlled in response to a signal from a scan signal line for reading, and wasteful power consumption is avoided by disabling the scanning signal lines outside the object sensing zone at the time of stopping light emission.

With reference to a possible implementation of the first aspect, the stopping emission includes simultaneously disabling emission of light emitting elements in the pattern image arranged along at least two adjacent emission signal lines.

According to this implementation, since the emission of the light emitting elements in the pattern image arranged along at least two adjacent emission signal lines is stopped, the CDM driving method is realized by shifting the control to disable a bundle of a plurality of emission signal lines.

With reference to a possible implementation of the first aspect, the light receiving element is connected to a switch, and the measuring controls the switch in such a way that the plurality of light receiving elements connected to one data signal line are simultaneously connected to a photometric device.

According to this implementation, a simpler configuration can be realized by removing one TFT from the PD circuit and connecting the PD circuit to an external switch.

A second aspect provides a display device including:

a plurality of emission signal lines that are arranged along a first axis and each supplies an emission signal to a plurality of light emitting elements;

a plurality of data signal lines that are arranged along a second axis and supply a data signal to cause each of the plurality of light emitting elements to emit light, wherein the first axis and the second axis are perpendicular;

a storage unit storing a to be displayed in an object sensing zone where an object is detected, wherein the plurality of frame patterns is designed according to the object;

light receiving elements that detect the object based on light from the light emitting elements;

a controller that displays the plurality of frame patterns, for each of the plurality of frame patterns, the controller displaying the pattern image, the displaying including

stopping emission of light emitting elements arranged along a part of the emission signal lines within a displayed frame pattern, and

a photometric unit that measures reflected light from the object based on the emission of the light emitting elements detected by the light receiving elements.

With reference to a possible implementation of the second aspect, the controller scans the pattern image by only light emitting elements within the object sensing zone.

With reference to a possible implementation of the second aspect, the controller disables light emitting elements outside the object sensing zone.

With reference to a possible implementation of the second aspect, the controller includes a plurality of gate on arrays (GOAs) , and enables only a GOA that drives light emitting elements within the object sensing zone.

According to this implementation, the controller is constituted by a plurality of GOAs, and power consumption can be reduced by enabling only those GOAs which drive the light emitting elements within the object sensing zone and disabling the other GOAs.

With reference to a possible implementation of the second aspect, reading of the light receiving elements is controlled in response to a signal from a scan signal line for reading, and the controller disables scan signal lines outside the object sensing zone.

With reference to a possible implementation of the second aspect, the controller simultaneously disables emission of light emitting elements in the pattern image arranged along at least two adjacent emission signal lines.

With reference to a possible implementation of the second aspect, the light receiving element is connected to a switch, and the controller controls the switch in such a way that the plurality of light receiving elements connected to one data signal line are simultaneously connected to a photometric device.

BRIEF DESCRIPTION OF DRAWINGS

To describe the technical solutions in the embodiments of the present invention or in the background more clearly, the following briefly describes the accompanying drawings required for describing the embodiments of the present invention or the background in which:

Fig. 1 is a block diagram showing a configuration example of a display device according to an embodiment;

Fig. 2 is a diagram showing a configuration example of a pixel circuit used in an OLED;

Fig. 3 is a timing chart illustrating an example of drive control for the pixel circuit shown in Fig. 2;

Fig. 4 is a perspective view showing a combination of a display and an image sensor;

Fig. 5 is a diagram showing a relationship between an array of OLEDs and PDs, and a subject;

Fig. 6 is a diagram showing an example in which the patterned light shown in Fig. 4 is shifted in the horizontal direction;

Fig. 7 is a diagram showing an example of a frame pattern used for pattern lighting;

Fig. 8 is a diagram showing an example of pixel driving in fingerprint authentication;

Fig. 9 is a diagram showing the cross-sectional structure of a display in which a finger is placed on a display surface;

Fig. 10 is a diagram virtually showing the strengths of lights received by PDs shown in Fig. 9;

Fig. 11 is a diagram showing the cross-sectional structure of the display in which a finger is placed on a display surface according to the embodiment;

Fig. 12 is a diagram showing a curve in which the strengths of lights received by the PDs in Fig. 11 are plotted;

Fig. 13 is a diagram showing a frame pattern according to the embodiment;

Fig. 14 is a diagram showing an example of pixel driving in fingerprint authentication according to the embodiment;

Fig. 15 is a diagram showing an example of pixel driving in fingerprint authentication according to an embodiment;

Fig. 16 is a diagram showing temporal changes of frame images according to the embodiment;

Fig. 17 is a timing chart showing an example of drive control for a pixel circuit according to the embodiment;

Fig. 18 is a diagram showing a configuration example of a gate driving circuit;

Fig. 19 is a diagram showing a configuration example of the gate driving circuit;

Fig. 20 is a diagram showing a configuration example of the pixel circuit;

Fig. 21 is a timing chart showing drive control for a pixel circuit according to an embodiment;

Fig. 22 is a diagram showing a relationship between an array of OLEDs and PDs, and a subject; and

Fig. 23 is a top view of an array of PDs in an image sensor according to an embodiment.

DESCRIPTION OF EMBODIMENTS

Terms used in the embodiments of this application are merely used to explain specific embodiments of this application, but are not intended to limit this application. (First Embodiment)

The following describes the first embodiment of the present disclosure. In this embodiment, a CDM (Code Division Multiplexing) driving method for driving an image sensor is combined with pattern lighting technique.

Fig. 1 is a block diagram showing a configuration example of a display device according to a first embodiment of the present disclosure. A display device 100 includes a driving circuit 1. A pixel array 104 included in the driving circuit 1 has a plurality of pixel circuits arranged in a two-dimensional form (matrix form) of N rows by M columns. A vertical scanning circuit 101 that supplies a pixel drive signal is arranged on one end side (left side in the figure) of the pixel array 104. The pixel array 104 and the vertical scanning circuit 101 are connected by signal lines 102. In addition, a signal converter 106 connected to signal lines 105 for respective columns, and a horizontal scanning circuit 107 are arranged on a lower end side (lower side in the figure) of an imaging region.

The display device 10 includes a controller 103. The controller 103 generates and outputs a master clock or a clock obtained by dividing the master clock, based on the master clock. The vertical scanning circuit 101, the signal converter 106, and the horizontal scanning circuit 107 are controlled in synchronization with the clock output from the controller 103. The controller 103 is connected to a memory 109, and performs control based on data stored in the memory 109.

The vertical scanning circuit 101 sets an address, and drives emission signal lines to perform vertical scanning. The emission signal lines are arranged along an x-axis, and each supplies emission signals to a plurality of OLEDs. The signal converter 106 performs signal conversion processing such as converting an analog output of a pixel into a digital output, and outputs the digital output to an output circuit 108. Also, the horizontal scanning circuit 107 sequentially selects each signal conversion unit of the signal converter 106 in synchronization with the clock output from the controller 103, and controls the signal converter 106 to read signals from signal lines 105 and output the signals to the output circuit 108. The horizontal scanning circuit 107 drives the data signal lines. The data signal lines are arranged along a y-axis, and supply a data signal for causing emission of each of the plurality of OLEDs, which are a plurality of emission signal elements. In one embodiment, the signal converter 106 may include an AFE (Analog Front End) . The AFE is a photometric device, and functions as a detection unit that detects, through PDs, reflected light from a subject originated from emission of OLEDs.

The pixel circuit constituted by a combination of an OLED and APS according to the present embodiment may be applied to, but is not limited to, various electronic devices such as a cellular phone, a smartphone, a personal digital assistant (PDA) , and a PC.

Fig. 2 shows a configuration example of a pixel circuit used for an OLED. The pixel circuit is configured as a 7T1C+1T+PD circuit, and includes a pixel unit driving circuit 2 and a PD driving circuit 3.

In the pixel array 104, each line includes multiple pixel units. The pixel unit driving circuit 2 drives and controls a pixel for each pixel unit in an n ^th line, and one subpixel corresponds to a pixel unit in the following description. The pixel unit driving circuit 2 includes one OLED, seven transistors, and one capacitor. One OLED corresponds to a subpixel of one color in red (R) , green (G) , and blue (B) constituting one pixel.

The pixel unit driving circuit 2 includes a switch transistor T2 for switching a Data Write signal which is a data signal applied to the corresponding data line in response to a Write Signal which is a scan signal applied to the n ^th write line. The pixel unit driving circuit 2 also includes a drive transistor T4 and a compensation transistor T3. The drive transistor T4 is supplied at a gate with a charge voltage corresponding to a data signal input to a capacitor C1 via the switch transistor T2, and supplies a drive current for the organic EL element. The compensation transistor T3 compensates for a threshold voltage of the drive transistor T4. The pixel unit driving circuit 2 also includes the capacitor C1 for storing a data signal having a voltage level applied to the gate of the drive transistor T4, and an organic EL element OLED that emits light corresponding to the applied drive current.

The pixel unit driving circuit 2 also includes a switch transistor T6 for supplying a power supply voltage ELVDD to the drive transistor T4 in response to an emission signal Em, and a switch transistor T5 for supplying the drive current from the drive transistor T4 to the OLED in response to the emission signal Em. The pixel unit driving circuit 2 also includes a reset transistor T1 for initializing a data signal stored in the capacitor C1 in response to an Init signal which is a scan signal for an (n-1) ^th line. Further, the pixel unit driving circuit 2 includes a reset transistor T7 that has a source connected to a line of an initialization voltage VINI, a gate connected to a line of a Write signal, and a drain connected to the OLED. The transistors T1 to T7 are configured as p-type thin film transistors (TFTs) .

The switch transistor T2 has a gate to which the Write signal to be applied to the corresponding scan line is applied, a source to which the Data Write signal which is a data signal to be applied to the corresponding data line is applied, and a drain connected to a source of the drive transistor T4.

The drive transistor T4 has the gate connected to one terminal of the capacitor C1, and a drain connected to one terminal of the OLED via the switch transistor T5. The compensation transistor T3 has a drain and a source respectively connected to the gate and drain of the drive transistor T4, and a gate to which the Write signal is applied. A high-level power supply voltage ELVDD is supplied from the corresponding power supply to the other terminal of the capacitor C1.

The switch transistor T5 has a gate to which the emission signal Em is applied, a source connected to the drain of the drive transistor T4, and a drain connected to one end of the OLED. The other end of the OLED is connected to a power supply of a voltage ELVSS.

The PD driving circuit 3 includes a photodiode PD, which is a light receiving element, and a transistor T8. In the PD, a PN junction is formed by a p-type semiconductor layer on the light reception side and an n-type semiconductor layer on the substrate side. When a reverse bias is applied to the PN junction, the PN junction where there are almost no carriers becomes a depletion layer. When light having energy larger than the forbidden band width of the semiconductor is irradiated in the vicinity of the depletion layer, carriers are generated. The PD may usually be configured as a PIN photodiode. The PIN photodiode includes three layers, that is, p ⁺-Si, i-Si, and n ⁺-Si, and electrodes arranged in between this layer structure. In the case of the PIN photodiode, the presence of the i-Si layer widens the width of the depletion layer obtained when the reverse bias is applied, thus ensuring the use of the photodiode with a high reverse bias voltage. The high reverse bias voltage in the wide depletion layer moves carriers quickly, enhancing the response speed.

The transistor T8 has a gate connected to a Sense signal which is a scan signal for reading data, a source connected to the anode of the PD, and a drain connected to a read line Data Sense. The transistor T8 is configured as a p-type thin film transistor (TFT) .

Next, the operation of the 7T1C+1T+PD circuit shown in Fig. 2 is described with reference to an example of a timing chart in Fig. 3.

It is assumed that the 7T1C+1T+PD circuit is driven by an (n-1) ^th scan signal Init1, an n ^th scan signal Init2 (i.e, Write1) , an emission signal Em1, and a switch signal Sense1. A period from time t1 to time t2 is an initialization period during which the scan signal Init1 is low, and the scan signal Write1, the emission signal Em1, and the switch signal Sense1 are high.

The reset transistor T1 is turned on by the scan signal Init1, and the other transistors T2 to T7 are turned off by the high-level scan signal Write1 and the emission signal Em1. Therefore, the data signal stored in the capacitor C1 is initialized, and the gate voltage of the drive transistor T4 is initialized.

Next, in a precharge period from t3 to t4, the scan signal Init1 is high, the scan signal Write1 is low, and the emission signal Em1 and the switch signal Sense1 are high. The reset transistor T1 is turned off, the compensation transistor T3 and the switch transistor T2 are turned on by the low-level scan signal Write1, and the switch transistors T5 and T6 are turned off by the emission signal Em1. Therefore, the voltage level of the Data Write signal, which is the data signal applied to the corresponding data line, is applied to the source of the drive transistor T4, so that the gate voltage of the drive transistor T4 is stabilized via the compensation transistor T3 to a voltage Vdata of the Data Write signal plus a threshold voltage Vth of the drive transistor T4, and is stored in the capacitor C1, which completes the precharge operation.

A period after t4 inclusive is an emission period during which the scan signal Init1 is high, and the emission signal Em1 becomes a low level after the scan signal Write1 goes high. The switch transistors T5 and T6 are turned on by the low-level emission signal Em1, the reset transistor T1 is turned off by the high-level scan signal Init1, and the compensation transistor T3 and the switch transistor T2 are turned off by the high-level scan signal Write1. Therefore, ELVDD is applied to the source of the drive transistor T4, and a gate-source voltage Vgs of the drive transistor T4 becomes Vgs=Vdata+Vth-ELVDD, and a current I flowing through the OLED is

I=k· (Vgs-Vth) ²

=k (Vdata+Vth-ELVDD-Vth) ²

=k (Vdata-ELVDD) ²

so that the current that does not depend on the threshold voltage flows through the OLED to emit light.

In a read period from t5 to t6, the scan signals Init1 and Write1 are high, and Em1 and Sense1 are low. Therefore, the transistor T8 is turned on, so that the signal from the PD is read out by the read line Data Sense.

In the case of a frame of 8 by 8 pixels, the above-described process is performed for eight lines. Therefore, eight scan signals Write1 to Write8 (i.e. Init2 to Init9) , eight emission signals Em1 to Em8, and eight switch signals Sense1 to Sense8 are applied to PDs for eight lines.

The above-described combination of the OLED and the PD has two problems, namely, a reduction in S/N ratio and blurring. The following describes these problems.

First, a reduction in S/N ratio is described. The 7T1C+1T+PD circuit is less integrated than the 7T1C+APS circuit, and a reduction in the corresponding resolution is mitigated. However, since the 7T1C+1T+PD circuit does not have an amplifier transistor, the S/N ratio drops. For example, when performing authentication based on a captured image such as fingerprint authentication, a very small difference in reflected light from the object must be detected for each frame, which requires a high S/N ratio. When the S/N ratio is low, a noise-full fingerprint image is given, which adversely affects authentication.

As a method for improving the S/N ratio, a method of applying the CDM driving method to driving of an image sensor is known. Since the CDM driving method turns on a plurality of gate lines at the same time, a large amount of data should be collected at the same time. This complicates the circuit configuration for CDM driving. In this respect, the CDM driving method is implemented with a simple configuration in this embodiment.

The following describes the problem of blurring. In the case of a display including an image sensor, it is necessary to mount an optical device for the image sensor. The optical device for the image sensor is arranged on the pixel unit included in the display. In the case where the optical device is a lens, for example, a microlens for collecting more light on the light receiving element is arranged on the pixel unit, and a focus lens is arranged on the microlens. For the display, however, it is desirable to diffuse light in order to ensure a wide viewing angle. Since the optical device for the image sensor adversely affects the diffusion of light, the quality of the displayed image acquired is deteriorated, resulting in blurring.

As a method for eliminating blurring, a lensless camera technique in which the lattice of coded masks is arranged on the surface of an image sensor without using a focus lens is known. The light reflected from a subject passes through the lattice and thus reaches the image sensor in a slightly different combination. The image captured by the image sensor, after being synthesized and analyzed, becomes an image of the subject. However, the coded mask should be prepared with a complicated pattern. In addition, it is difficult to prepare an coded mask that does not degrade the display quality.

In order to improve blurring, the present embodiment uses a pattern lighting technique. Specifically, in order to avoid crosstalk of received light, patterned light that changes with time is output from the display, and light reflected from the subject is detected.

Next, the pattern lighting technique is described with reference to Figs. 4 to 6.

Fig. 4 is a perspective view showing a combination of a display and an image sensor. As shown in Fig. 4, in case of mounting an image sensor on a display, a structure where a display 1102 shown in Fig. 4 (a) is overlaid on an image sensor 1104 shown in Fig. 4 (b) is employed. Fig. 5 is a diagram showing a relationship between an array of combinations of OLEDs and PDs in a display device and a subject. As shown in Fig. 5, the image sensor 1104 has an array of PDs 1204, and the display 1102 includes an array of OLEDs 1202. For example, when light is emitted from a column of red (R) sub-pixels according to light patterned on the display 1102, red light strikes a subject 1203 as shown in Fig. 5 (a) . The light reflected from the subject 1203 is diffused and hits each of the plurality of PDs 1204. The light emitted from the OLED 1202 is reflected in different directions depending on the position on the subject 1203, and one PD 1204 receives lights reflected from various positions. In this way, the PD 1204 detects the subject 1203 based on the light from the OLED 1202.

As shown in Fig. 4, an array 1106 of lights perpendicular to the x-axis is an example of patterned light, and various patterns can be applied to the patterned light. For example, for the patterned light, patterns such as an array of lights horizontal to the x-axis, a grid pattern of the light array, a plurality of columns having a predetermined angle to the x-axis, a dotted grid pattern, and a checkerboard pattern, etc can be used.

In pattern lighting, a patterned light array 1106 is varied over time. Fig. 6 shows an example in which the patterned light shown in Fig. 4 is shifted in the horizontal direction (that is, the x-axis direction) . In the example shown in Fig. 6, the OLED 1202 positioned immediately below the subject 1203 emits light, and the reflected light from the subject 1203 is less spread than that in Fig. 5. Accordingly, the PD 1204 in the vicinity of the OLED 1202 positioned directly below the subject 1203 receives stronger reflected light. Thus, based on the strength of the reflected light received by each PD, the shape of the subject 1203 may be acquired by, for example, the AFE connected to the PD.

Fig. 7 shows an example of a frame pattern used for pattern lighting. The frame pattern is a pattern image that is displayed in an object sensing zone where an object which is in close proximity of the display surface of the display device is detected. A size of the frame patterns are designed according to the object to be detected. Each frame pattern shown in Fig. 7 is a frame of 8 by 8 pixels, and a white portion indicates a pixel that emits light and a gray portion indicates a pixel that does not emit light. In the example shown in the figure, eight types of frame patterns are prepared in which one frame is composed of six light emitting pixels. These frame patterns are stored in the memory 109 of the display device 100. The controller 103 sequentially reads out and uses the individual frame patterns from the memory 109 to control light emission of the pixels.

However, in pattern lighting, it is necessary to prepare a complex frame pattern or various frame patterns in order to reduce crosstalk. In this respect, a reduction in crosstalk is achieved with fewer frame patterns in the present embodiment.

Fig. 8 is a diagram showing an example of pixel driving in fingerprint authentication. In Fig. 8, a frame pattern composed of a non-light emitting portion 1902 shown in gray and a light emitting portion 1904 shown in white are displayed on a display 1901. The emission signal lines for controlling the emission of the display 1901 extend along the x axis, and the data signal lines through which data signals flow extend along the y axis. With the frame pattern in use, all the emission signal lines are enabled to let the emission signals flow, and the emission of the pixels of the portion 1904 that emits light is controlled by the data signals from the data signal lines. A user places a finger on the light emitting portion 1904 for authentication processing.

Next, the principle of fingerprint authentication is described with reference to Fig. 9. Fig. 9 shows the cross-sectional structure of a display in which a finger 901 is placed on a display surface 902, and drive control proceeds along a time axis t. In Fig. 9 (a) , a PD a1 is connected to AFE at the beginning. All of seven OLEDs a2 to g2 emit lights, and the PD a1 receives light reflected from the finger 901, and passes a current corresponding to the strength of the light to the AFE.

Next, in Fig. 9 (b) , a PD b1 is connected to the AFE. The seven OLEDs a2 to g2 all emit lights, and the PD b1 receives light reflected from the finger 901, and passes a current corresponding to the strength of the light to the AFE. Likewise, with the PDs connected to the AFE being sequentially shifted, and the light strength is measured based on the current flowing from each PD in the AFE. The above processing is likewise performed for the OLEDs and PDs arranged in the direction perpendicular to the surface of the sheet of Fig. 9.

Fig. 10 is a diagram virtually showing the strengths of lights received from the PD a1 to PD g1 shown in Fig. 9, where the horizontal axis indicates the positions of the OLEDs. For example, the PD a1 receives strongly reflected light based on the OLED a2, and then strongly receives reflected light based on the OLED b2, but hardly receives reflected light based on the OLEDs c2 to g2. Further, in view of the relationship with the finger 901, the light received by the PD positioned directly below a valley of the fingerprint is weaker than the light received by the PD positioned directly below a ridge of the fingerprint. Since the strength of light received by each PD is the sum of the reflected lights from all the OLEDs, it is understood that the light received by the PD d1 is weak with reference to Fig. 10 (a) . Fig. 10 (b) shows a curve 1002 in which the strengths of lights received by the PDs are plotted. Here, the horizontal axis indicates the relative positions of the PDs. With reference to Fig. 10 (b) , the values of the results of measurement of the valley portions are low compared with a curve 1001 of the measurement results when there are no valleys. Therefore, it is understood that a valley exists in the vicinity of the PD d1. However, the relative difference between the measured values of the ridge and the valley of the fingerprint is 0.1, which indicates that the S/N ratio is low, causing blurring.

Next, a method of driving the display device according to the present embodiment is described with reference to Fig. 11 using fingerprint authentication as an example. Fig. 11 shows the cross-sectional structure of the display in which the finger 901 is placed on the display surface 902, and drive control proceeds along the time axis t. The drive control shown in Fig. 11 employs the CDM driving method, and all of the PDs a1 to g1 are connected to the AFE in all states shown in Figs. 11 (a) and 11 (b) . First, in Fig. 11 (a) , all the OLEDs except the OLED a2 emit lights, and lights received by all the PDs are measured by the AFE. Next, in Fig. 11 (b) , all the OLEDs except the OLED b2 emit lights, and lights received by all the PDs are measured by the AFE. Likewise, the OLEDs to be disabled for emission are sequentially shifted in the y-axis direction, the emission of the OLED g2 is stopped in Fig. 11 (g) , and the lights received by all the PDs are measured by the AFE. The above processing is likewise performed for those OLEDs and the PDs which are arranged in the direction perpendicular to the surface of the sheet of Fig. 11. In this way, the process of shifting the stopping of emission of the OLEDs, arranged along the emission signal line, along the y axis is implemented.

Next, the CDM driving method is specifically described. In Fig. 11, voltages related to outputs from the PDs a1, b1, ..., g1 are represented as Va1, Vb1, ..., Vg1. In addition, in Figs. 11 (a) , 11 (b) , ..., and 11 (g) , voltages measured by the AFE are expressed as Va, Vb, ..., Vg. The voltage output to the AFE is the sum of the voltage Va1 related to the output from the PD a1 to the voltage Vg1 related to the output from the PD g1. In the case of Fig. 11 (a) , the voltage Va1 related to the output from the PD a1 located immediately below the OLED a2 that is not emitting light is zero. Therefore, the voltage Va can be expressed as Va=Vb1+Vc1+Vd1+Ve1+Vf1+Vg1.

In the case (b) where the second OLED b2 from the left is not emitting light, the voltage Vb1 from the PD b1 located directly below the OLED b2 is zero. Therefore, the voltage Vb output to the AFE can be expressed as Vb=Va1+Vc1+Vd1+Ve1+Vf1+Vg1. Likewise, when the voltages c to g output to the AFE by sequentially shifting non-emitting OLEDs are measured, the voltages Va to Vg measured by the AFE can be expressed by the following determinant.

In the above determinant, the following matrix is called "CDM code. "

To obtain output voltages Va1 to Vg1 from the individual PDs, an inverse matrix should be applied to [Va, Vb, Vc, Vd, Ve, Vf, Vg] as follows.

The strength of light received by each PD can be obtained in this manner.

Fig. 12 shows a curve 1003 in which the strengths of lights received by the PDs in Fig. 11 are plotted. The relative difference between the measurements at the ridge and valley of the fingerprint is 0.5, indicating a significant improvement on the S/N ratio and blurring.

Fig. 13 shows a frame pattern used in the pattern lighting according to this embodiment. A size of the frame patterns are designed according to the object to be detected. Each of a first frame pattern and a second frame pattern shown in Fig. 13 is a frame of 8 by 8 pixels in which a white portion indicates pixels that emit light and a gray portion indicates pixels that do not emit light. In the example shown in the figure, a frame pattern in which one frame is composed of eight pixels is prepared. These frame patterns are stored in the memory 109 of the display device 100, and the controller 103 sequentially uses the individual frame patterns from the memory 109 to control emission of the pixels. In this embodiment, the emission of the OLEDs is controlled using these two types of frame patterns to generate patterns similar to the eight types of frame patterns shown in Fig. 7.

Fig. 14 is a diagram showing an example of pixel driving in fingerprint authentication according to the present embodiment. A display 1401 displays a frame pattern including non-light emitting portions 2102 and 2014 shown in gray and light emitting portions 2016 shown in white. The frame pattern displayed on the display 1401 varies along the time axis t. Emission signal lines for controlling emission of the display 1401 extend along the x axis, and data lines through which data signals flow extend along the y axis. With the frame patterns used, all the emission signal lines are enabled to let the emission signals flow, so that the emission control of the pixel portions 2106 that emit light according to the data signals from the data signal lines is performed. The user places a finger on the light emitting portion 2106 for authentication processing.

Fig. 15 is a diagram showing an example of pixel driving in fingerprint authentication according to another embodiment. With the frame patterns used, only the emission signal lines of the portion 2104 having the light emitting portion 2106 are enabled to let the emission signals flow, so that the emission control of the pixel portion 2106 to emit light based on the data signals from the data signal lines is performed. The user places a finger on the light emitting portion 2106 for authentication processing. In this case, the other emission signal lines are disabled, so that wasteful power consumption can be avoided.

Fig. 16 shows temporal changes of frame images displayed on the display device in the embodiment shown in Fig. 15. In the photodiode driving process according to the present embodiment, the first frame pattern having eight subframes is displayed, and scanning is performed in a 4 by 4 pixel portion indicated by a solid line 1501. In the display processing of the first to fourth subframes, the first frame pattern is displayed, and the first subframe is formed by disabling the third emission signal line from the top of the figure. Next, the second subframe is formed by disabling the fourth emission signal line from the top of the figure. Likewise, the third and fourth subframes are formed by sequentially shifting the emission signal lines to be disabled. Next, the second frame pattern is displayed, and the fifth subframe is formed by disabling the third emission signal line from the top of the figure. Then, the sixth subframe is formed by disabling the fourth emission signal line from the top of the figure. Likewise, the seventh and eighth subframes are formed by sequentially shifting the emission signal lines to be disabled.

According to the embodiment described above, it is possible to increase the S/N ratio and reduce blurring by combining the CDM driving method with pattern lighting. Further, the combination of the CDM driving method with pattern lighting can simplify the drive control.

The above-described embodiments can be applied to both of the configuration in which the PD circuit has the amplifier transistor and the configuration in which the PD circuit does not have the amplifier transistor to demonstrate the same effects.

(Second Embodiment)

The following describes a second embodiment of the present disclosure. In this embodiment, at least two adjacent emission signal lines are simultaneously enabled. Then, the emission signal lines that are disabled are sequentially shifted with time. For example, in an array of nine OLEDs and nine PDs, in case of performing drive control to disable two adjacent emission signal lines, the CDM code used to express the voltage output to the AFE can be expressed as follows:

In the CDM driving method according to the present embodiment, as described in the first embodiment, the voltage output to the AFE is measured nine times while sequentially shifting two PDs that stop emission to acquire the measurement voltages Va, Vb, Vc, Vd, Ve, Vf, Vg, Vh, and Vi. The voltage from each of the nine PDs can be obtained by applying the inverse matrix of the aforementioned CDM code to [Va, Vb, Vc, Vd, Ve, Vf, Vg, Vh, Vi] .

(Third Embodiment)

The following describes a third embodiment of the present disclosure. In the present embodiment, only the emission signal lines including a light emitting portion is enabled by using the frame pattern to let the emission signal flow, and the emission control of the pixel portions that emit light based on the data signals from the data signal lines is performed. Meanwhile, the other emission signal lines are disabled. At this time, power consumption can be further reduced by also disabling the Sense signal lines for reading data.

Fig. 17 shows an example of a timing chart in the case of performing drive control for disabling the emission signal lines in an array of nine OLEDs and nine PDs. When fingerprint authentication is performed on the first to ninth emission signal lines, only the emission signals Em1 to Em9 are switched on or off, and the emission signals Em10 to EmN of the tenth and subsequent emission signal lines are all disabled. As for the Sense signal which is a scan signal for reading data, only the first to ninth signals Sense1 to Sense9 are enabled or disabled, and the emission signals Sense10 to SenseN of the tenth and subsequent emission signal lines are all disabled.

A gate driver on array (GOA) may be adopted for the gate driving circuit according to the present embodiment. The GOA uses a driving method in which a gate driving circuit is directly integrated on an array substrate without being externally connected, and progressive scanning for the gates is implemented. The GOA technique can increase the degree of integration to thereby reduce the manufacturing process and increase the product cost. Fig. 18 shows a configuration example of the GOA of the display device. In the GOA, an Emit Scan GOA and a Gate Scan GOA are arranged in between an active region included in the pixel array. The Emit Scan GOA is a GOA that drives an emission signal. The Gate Scan GOA is a GOA that drives scan signals (Init signal, Write signal, and Sense signal that is a scan signal for reading data) . The Emit Scan GOA is connected to odd-numbered lines on the active region and sequentially drives the emission signal lines. The Gate Scan GOA is connected to even-numbered lines on the active region and sequentially drives the Sense signal lines. In the present embodiment, only the emission signal lines for the part that is used for fingerprint authentication are scanned, while for the scan signal lines, only the emission signal lines for the part that is used for fingerprint authentication are scanned.

Fig. 19 is a diagram showing another configuration example of the gate driving circuit. As shown in Fig. 19, the GOA driving circuit may be composed of a plurality of Emit Scan GOAs and a plurality of Gate Scan GOAs. In this case, drive control is performed so as to scan only the Emit Scan GOAs connected to the emission signal lines of the part used for fingerprint authentication and the Gate Scan GOAs connected to the scan signal lines. Other GOAs are always disabled during authentication process. In this way, power consumption in authentication processing can be reduced. (Fourth Embodiment)

The following describes a fourth embodiment of the present disclosure. In the above embodiment as shown in Fig. 2, there is a transistor T8, and the transistor T8 is connected between the PD and the read line Data Sense when reading data. Then, scanning for data reading is performed by applying the Sense signal as a scan signal to the gate of T8. In the case of the CDM driving method, however, all the PDs are connected to the AFE along the vertical direction of the display in one data reading from the PDs. This eliminates the need for scanning along the vertical direction of the display. In this embodiment, therefore, the transistor T8 is removed, and drive control is performed so that all the PDs are simultaneously connected to the AFE along the vertical direction of the display. In the 7T1C+PD circuit shown in Fig. 20, a switch 2001 is provided between the anode of the PD and the AFE. The switch 2001 is controlled by the Switch signal so as to connect the anode to the ELVDD when fingerprint detection is not performed, and so as to connect the anode to the AFE when fingerprint detection is performed. Other PDs along the vertical direction of the display are likewise controlled by the Switch signal. The removal of one TFT from the 7T1C+1T+PD circuit in this way can provide a simpler configuration.

Fig. 21 shows an example of a timing chart in the case where the emission signal lines are driven and controlled in an array composed of nine OLEDs and nine PDs. The Switch signal for switching the switch 2001 may be controlled so as to periodically connect the PD to the power supply voltage ELVDD or the AFE.

(Fifth Embodiment)

The following describes a fifth embodiment of the present disclosure in which pattern lighting and a mask are combined. Fig. 22 is a diagram showing a relationship between an array of combinations of OLEDs and PDs in a display device and a subject. In Fig. 22, the OLEDs 1202 and the PDs 1204 are alternately arranged. In Fig. 22 (a) , a mask 1206 for an image sensor is provided on the PD 1204. The mask 1206 blocks the light path of a part of the reflected light from the subject. In Fig. 22 (b) , arrows indicated by broken lines indicate light that is blocked by the mask and does not reach the PD 1204. The effect of a complicated mask that reduces crosstalk can be improved by shifting the column of OLEDs that emit light in this manner, for example, in the horizontal direction in Fig. 4 or Fig. 5. In addition, an image can be easily reconstructed.

Fig 23 is a top view of the arrangement of PDs in the image sensor, showing the positional relationship between the PDs and masks. An example of the masks is described with reference to Fig. 23. Masks indicated by black dots or lines may be configured as a plurality of vertical linear masks as shown in Fig. 23 (a) , or lattice-like masks arranged at the same position on the individual PDs as shown in Fig. 23 (b) . Further, the masks may be vertical linear masks arranged at different positions on the PDs for each PD column, as shown in Fig. 23 (c) . Furthermore, the masks may be arranged at different positions on the individual PDs as shown in Fig. 23 (d) .

As another example, a collimator or a pinhole may be used on the image sensor without using a lens to reduce blurring in the combination of the image sensor and display.

In the above-described embodiment, the pixel unit driving circuit is exemplified to be comprised of seven transistors and one capacitor. However, the quantities of transistors and capacitors and the circuit configuration may be varied in use regardless of the above-described examples.

In conclusion, what is described above is merely examples of embodiments of the technical solutions of the present application, but is not intended to limit the protection scope of the present application. Any modification, equivalent replacement, or improvement made without departing from the principle of the present application shall fall within the protection scope of the present application.

Claims

A method of driving a display device, wherein the display device includes a plurality of emission signal lines that are arranged along a first axis and each supplies an emission signal to a plurality of light emitting elements, a plurality of data signal lines that are arranged along a second axis and supply a data signal to cause each of the plurality of light emitting elements to emit light, a storage unit that are storing a plurality of frame patterns to be displayed in an object sensing zone where an object is detected, and light receiving elements that detect the object based on light from the light emitting elements, wherein the plurality of frame patterns is designed according to the object, and wherein the first axis and the second axis are perpendicular, the method comprising, for each of the plurality of frame patterns:

scanning the pattern image, the scanning including

stopping emission of light emitting elements arranged along a part of the emission signal lines within a displayed frame pattern, and

shifting the emission signal lines to be disabled for emission along the second axis within the displayed frame pattern; and

by the light receiving elements, measuring reflected light from the object based on the emission of the light emitting elements.
The method according to Claim 1, wherein the scanning includes scanning the pattern image by only light emitting elements within the object sensing zone.
The method according to Claim 2, wherein the stopping emission includes disabling light emitting elements outside the object sensing zone.
The method according to Claim 1, wherein reading of the light receiving elements is controlled in response to a signal from a scan signal line for reading, and the stopping emission includes disabling scan signal lines outside the object sensing zone.
The method according to Claim 1, wherein the stopping emission includes simultaneously disabling emission of light emitting elements in the pattern image arranged along at least two adjacent emission signal lines.
The method according to Claim 1, wherein the light receiving element is connected to a switch, and the measuring controls the switch in such a way that the plurality of light receiving elements connected to one data signal line are simultaneously connected to a photometric device.
A display device comprising:

a plurality of emission signal lines that are arranged along a first axis and each supplies an emission signal to a plurality of light emitting elements;

a plurality of data signal lines that are arranged along a second axis and supply a data signal to cause each of the plurality of light emitting elements to emit light, wherein the first axis and the second axis are perpendicular;

a storage unit storing a to be displayed in an object sensing zone where an object is detected, wherein the plurality of frame patterns is designed according to the object;

light receiving elements that detect the object based on light from the light emitting elements;

a controller that displays the plurality of frame patterns, for each of the plurality of frame patterns, the controller displaying the pattern image, the displaying including

stopping emission of light emitting elements arranged along a part of the emission signal lines within a displayed frame pattern, and

shifting the emission signal lines to be disabled for emission along the second axis within the displayed frame pattern; and

a photometric unit that measures reflected light from the object based on the emission of the light emitting elements detected by the light receiving elements.
The display device according to Claim 7, wherein the controller scans the pattern image by only light emitting elements within the object sensing zone.
The display device according to Claim 8, wherein the controller disables light emitting elements outside the object sensing zone.
The display device according to Claim 9, wherein the controller includes a plurality of gate on arrays (GOAs) , and enables only a GOA that drives light emitting elements within the object sensing zone.
The display device according to Claim 7, wherein reading of the light receiving elements is controlled in response to a signal from a scan signal line for reading, and the controller disables scan signal lines outside the object sensing zone.
The display device according to Claim 7, wherein the controller simultaneously disables emission of light emitting elements in the pattern image arranged along at least two adjacent emission signal lines.
The display device according to Claim 7, wherein the light receiving element is connected to a switch, and the controller controls the switch in such a way that the plurality of light receiving elements connected to one data signal line are simultaneously connected to a photometric device.