CN118731914A - An adaptive proximity light detection sensor - Google Patents

Abstract

The application discloses a self-adaptive proximity light detection sensor, wherein a receiving end of the self-adaptive proximity light detection sensor is provided with a current source array and a first digital calibration module, the current source array and a photodiode are arranged in parallel and are connected to a non-inverting input end of an integrator, the first digital calibration module is used for collecting digital signals and carrying out feedback calibration on current of the current source array, the self-adaptive proximity light detection sensor is provided with a matching capacitor and a second digital calibration module, and the second digital calibration module is used for collecting digital signals and carrying out noise calibration on the matching capacitor. The application can adaptively eliminate the component of the structural light interference, reduce the noise close to the optical sensor, increase the consistency of the optical sensor chip in application, and is suitable for the mass production of mobile phones.

Description

An adaptive proximity light detection sensor

Technical Field

The present invention relates to the field of optical sensors, and in particular to an adaptive proximity light detection sensor.

Background Art

In the field of mobile phones and tablets, high-performance optical sensor chips are used as standard configuration for proximity light detection. System designers can automatically adjust the brightness of the display screen according to the distance between the display screen and the object being measured, thereby reducing system power consumption. In actual under-screen application scenarios, due to the attenuation of infrared light by the display screen and the screen's requirements for the LED light on time, the proximity light detection sensor needs to be able to distinguish weak infrared reflection signals of objects.

In the existing technical solution, the proximity light detection system consists of an LED transmitter and a proximity light detection receiver. The LED light is controlled by controlling the on and off of the LED switch. When the photodiode receives the reflected light signal of the object, the light signal is converted into an electrical signal by the analog front-end circuit AFE, and then converted into a digital signal Data by the analog-to-digital converter ADC for system-level digital signal processing.

In actual applications, due to the influence of the internal structure of the mobile phone on the optical path of the optical sensor chip, structured light interference will cause sensor output deviation, thereby affecting the optical sensor chip's judgment of the proximity and distance of the measured object. The existing technical solution reduces the impact of structured light interference by eliminating fixed deviations, that is, by adding a fixed digital offset to the output of the digital-to-analog converter ADC to reduce structured light interference. However, in actual applications, the consistency of optical sensor chips at the application end is poor. At the same time, due to differences in mobile phone structures, the added digital deviation value of the elimination amount will also be different, which is not suitable for mass production of mobile phones.

Summary of the invention

The purpose of the present invention is to provide an adaptive proximity light detection sensor that can adaptively eliminate structured light interference, increase the consistency of optical sensor chips in applications, and is suitable for mass production of mobile phones. At the same time, it can adaptively reduce proximity light sensor noise and improve and optimize optical sensor performance.

To achieve the above technical objectives, the present invention provides an adaptive proximity light detection sensor, wherein the receiving end of the sensor includes: a photodiode, an integrator and an analog-to-digital converter, the digital signal output by the analog-to-digital converter contains data of structured light interference, wherein: the receiving end also includes a current source array and a first digital calibration module, the current source array and the photodiode are arranged in parallel and connected to the non-inverting input terminal of the integrator, the first digital calibration module collects the digital signal and performs feedback calibration on the current of the current source array to reduce the component of the structured light interference in the digital signal.

The present invention provides an adaptive proximity light detection sensor, which collects the digital signal through a first digital calibration module and performs feedback calibration on the current of a current source array. This feedback calibration form enables the current signal to form an adaptive calibration form to the digital signal, can adaptively eliminate structured light interference, increase the consistency of the optical sensor chip in the application, and is suitable for mass production of mobile phones.

As a further improvement, the feedback calibration includes: the digital signal passes through the first digital calibration module, first adjusting the current intensity of the current source array to perform a coarse calibration on the current flowing into the integrator, and then adjusting the current width of the current output by the current source array to perform a fine calibration on the current flowing through the integrator.

As a further improvement, the transmitting end of the sensor is an LED transmitting end, and the LED transmitting end has an LED switch to turn on and off the LED lamp in the LED transmitting end to control the light emission. The integrator has a negative feedback circuit at the positive input end, and the negative feedback circuit at the positive input end is an integrating capacitor. The receiving end also includes a comb filter, and the digital signal is connected to the first digital calibration module after passing through the comb filter.

As a further improvement, the photodiode receives the reflected light from the LED emission end and converts it into a current signal, the current signal flows out through the integrator and the integrating capacitor and is converted into a voltage signal, and the voltage signal flows out through the analog-to-digital converter and the comb filter and is converted into the digital signal.

As a further improvement, a first switch is arranged between the photodiode and the integrator, and the first switch controls the current signal converted by the photodiode to the integrator; one end of the current source array is connected to the power supply terminal VDD, and a second switch array corresponding to the current source array is arranged between the other end of the current source array and the non-inverting input terminal of the integrator, and the first digital calibration module controls the reduction of the current intensity and the width of the current output by the current source array through the second switch array.

As a further improvement, the digital signal Data<15:0>, the current strength selection signal Isrc_sel<3:0>, in the first coarse adjustment calibration, when the digital signal Data<15:0> decreases to less than the threshold value d0, the first digital calibration module stops working, and the current strength selection signal Isrc_sel<3:0> is locked to d2, and in the subsequent fine adjustment calibration, as the width of the current width signal decreases, the digital signal Data<15:0> gradually increases, and when the requirement that the structured light threshold is greater than 0 and less than d20 is met, the first digital calibration module stops working, and at this time the current width signal width is locked, and the structured light interference elimination is completed.

As a further improvement, the receiving end also includes: a matching capacitor and a second digital calibration module, the matching capacitor is connected to the negative phase input terminal of the integrator, the integrator has a negative feedback circuit at the negative phase input terminal, the negative feedback circuit at the negative phase input terminal is a capacitor, and the second digital calibration module collects the digital signal and performs noise calibration on the matching capacitor to reduce the proximity light sensor noise.

As a further improvement, the noise calibration is that the digital signal calibrates the matching capacitor through the second digital calibration module, and the matching capacitor is matched with the parasitic capacitance of the photodiode by adjusting the capacitance of the negative feedback circuit at the negative phase input end, thereby reducing the noise interference of the integrator and reducing the noise jump of the digital signal.

As a further improvement, the parasitic capacitor is arranged in parallel with the photodiode and has a grounding end, the other end of the parasitic capacitor connected in parallel with the photodiode is connected to the first switch, one end of the matching capacitor is grounded, and a third switch array corresponding to the matching capacitor is arranged between the other end of the matching capacitor and the negative phase input end of the integrator, and the second digital calibration module acts on the third switch array.

As a further improvement, the present invention provides an adaptive proximity light detection sensor for application in the field of mobile phones or tablet computers, with an LED driving current of 100mA, an LED on time of 1ms, an analog-to-digital converter full scale of 65535Code, proximity light response data at a distance of 3cm is 38000Code, the air structured light data is reduced to less than 20Code, and the noise jump is 10Code.

The adaptive proximity light detection sensor provided by the present invention is particularly applicable to the mass production of mobile phones or tablet computers, and can adaptively reduce the proximity light sensor noise, and improve and optimize the optical sensor performance.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a schematic diagram of the system framework of the present invention;

FIG2 is a schematic diagram of a timing diagram of structured light interference elimination calibration according to the present invention;

FIG. 3 is a schematic diagram of reducing the noise of a proximity light sensor according to the present invention.

Figure numerals: photodiode 1; current source array 2; matching capacitor array 3; integrator 4; analog-to-digital converter ADC; comb filter 5; first digital calibration module 6; second digital calibration module 7; current signal 8; integrating capacitor 9; capacitor 10; parasitic capacitor 11, power supply terminal VDD, first switch Sw1; second switch array Sw2 Array; third switch array Sw3 Array.

DETAILED DESCRIPTION

The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

As shown in Figures 1 to 3, in order to achieve the above-mentioned technical objectives, the present invention provides an adaptive proximity light detection sensor, wherein the receiving end of the sensor includes: a photodiode 1, an integrator 4 and an analog-to-digital converter ADC, the digital signal output by the analog-to-digital converter ADC contains data of structured light interference, wherein: the receiving end also includes a current source array 2 and a first digital calibration module 6, the current source array 2 and the photodiode 1 are arranged in parallel and connected to the non-inverting input terminal of the integrator 4, the first digital calibration module 6 collects the digital signal and performs feedback calibration on the current of the current source array 2 to reduce the component of the structured light interference in the digital signal.

The present invention provides an adaptive proximity light detection sensor, which collects the digital signal through a first digital calibration module and performs feedback calibration on the current of a current source array. This feedback calibration form enables the current signal to form an adaptive calibration form to the digital signal, can adaptively eliminate structured light interference, increase the consistency of the optical sensor chip in the application, and is suitable for mass production of mobile phones.

As a further improvement, the feedback calibration includes: the digital signal passes through the first digital calibration module 6, first adjusting the current intensity of the current source array 2 to perform a coarse calibration on the current flowing into the integrator 4, and then adjusting the current width of the current output by the current source array 2 to perform a fine calibration on the current flowing through the integrator 4.

As a further improvement, the transmitting end of the sensor is an LED transmitting end, and the LED transmitting end has an LED switch to turn on and off the LED lamp in the LED transmitting end to control the light emission. The integrator 4 has a negative feedback circuit at the positive input end, and the negative feedback circuit at the positive input end is an integrating capacitor 9. The receiving end also includes a comb filter 5, and the digital signal is connected to the first digital calibration module 6 after passing through the comb filter 5.

As a further improvement, the photodiode 1 receives the reflected light from the LED emission end and converts it into a current signal. The current signal flows out through the integrator 4 and the integrating capacitor 9 and is converted into a voltage signal. The voltage signal flows out through the analog-to-digital converter ADC and the comb filter 5 and is converted into the digital signal.

As a further improvement, a first switch Sw1 is arranged between the photodiode 1 and the integrator 4, and the first switch Sw1 controls the current signal converted by the photodiode 1 to the integrator 4; one end of the current source array 2 is connected to the power supply terminal VDD, and a second switch array Sw2 Array corresponding to the current source array 2 is arranged between the other end of the current source array 2 and the non-inverting input terminal of the integrator 4, and the first digital calibration module 6 controls the reduction of the current intensity and the width of the current output by the current source array 2 through the second switch array Sw2 Array.

As a further improvement, the digital signal Data<15:0>, the current strength selection signal Isrc_sel<3:0>, in the first coarse adjustment calibration, when the digital signal Data<15:0> decreases to less than the threshold value d0, the first digital calibration module 6 stops working, and the current strength selection signal Isrc_sel<3:0> is locked to d2, and in the subsequent fine adjustment calibration, as the width of the current width signal decreases, the digital signal Data<15:0> gradually increases, and when the requirement that the structured light threshold is greater than 0 and less than d20 is met, the first digital calibration module 6 stops working, and at this time the current width signal width is locked, and the structured light interference elimination is completed.

As a further improvement, the receiving end also includes: a matching capacitor 3 and a second digital calibration module 7, the matching capacitor 3 is connected to the negative phase input terminal of the integrator 4, the integrator 4 has a negative feedback circuit at the negative phase input terminal, the negative feedback circuit at the negative phase input terminal is a capacitor 10, and the second digital calibration module 7 collects the digital signal and performs noise calibration on the matching capacitor 3 to reduce the proximity light sensor noise.

As a further improvement, the noise calibration is that the digital signal calibrates the matching capacitor 3 through the second digital calibration module 7, and the matching capacitor 3 is matched with the parasitic capacitance 11 of the photodiode 1 by adjusting the capacitor 10 of the negative feedback circuit at the negative phase input end, thereby reducing the noise interference of the integrator 4 and reducing the noise jump of the digital signal.

As a further improvement, the parasitic capacitor 11 is arranged in parallel with the photodiode 1 and has a grounding end, the other end of the parasitic capacitor 11 connected in parallel with the photodiode 1 is connected to the first switch Sw1, one end of the matching capacitor 3 is grounded, and a third switch array Sw3 Array corresponding to the matching capacitor 3 is arranged between the other end of the matching capacitor 3 and the negative phase input end of the integrator 4, and the second digital calibration module 7 acts on the third switch array Sw3 Array.

As a further improvement, the present invention provides an adaptive proximity light detection sensor for application in the field of mobile phones or tablet computers, with an LED driving current of 100mA, an LED on time of 1ms, an analog-to-digital converter full scale of 65535Code, proximity light response data at a distance of 3cm is 38000Code, the air structured light data is reduced to less than 20Code, and the noise jump is 10Code.

The adaptive proximity light detection sensor provided by the present invention is particularly applicable to the mass production of mobile phones or tablet computers, and can adaptively reduce the proximity light sensor noise, and improve and optimize the optical sensor performance.

In the preferred embodiment of the present invention, the system framework is shown in Figure 1, and the sensor receiving end is composed of a photodiode 1 (Photodiode), a current source array 2 (Isrc), a matching capacitor array 3 (Cdummy), an integrator 4 (Integrator), an analog-to-digital converter ADC, a comb filter 5 (CIC filter) and a first digital calibration module 6 and a second digital calibration module 7.

The working principle of the present invention is as follows: the photodiode 1 receives the reflected light of the LED and converts it into a current signal 8 (Ipd), the current signal 8 flows out of the integrator 4 and the integrating capacitor 9 (Cint) and is converted into a voltage signal, which is converted into a digital signal Data<15:0> by the analog-to-digital converter ADC and the comb filter 5. The digital signal Data<15:0> adjusts the current intensity selection signal Isrc_sel<3:0> of the current source array 2 respectively through the first digital calibration module to roughly adjust the current flowing into the integrator 4, and then finely adjusts the current flowing through the integrator 4 through the current width Isrc_width, so as to reduce the structured light interference component in the digital signal Data<15:0>.

At the same time, the digital signal Data<15:0> is calibrated on the matching capacitor 3 through the second digital calibration module 7. The matching capacitor 3 is matched with the parasitic capacitance 11 (Cpd) of the photodiode 1 by adjusting the capacitance selection signal Cd_sel<3:0> of the capacitor 10 which is the negative feedback circuit at the negative phase input end, thereby reducing the noise interference of the integrator 4 and achieving the purpose of reducing the noise jitter of the digital signal Data<15:0>.

In a preferred embodiment of the present invention, as shown in FIGS. 1 and 2 , adaptive structured light interference elimination is divided into two parts: coarse calibration and fine calibration. The calibration process is explained by taking the analog-to-digital converter ADC output digital signal Data<15:0>, the current source array 2 intensity selection signal Isrc_sel<3:0> and the current source array 2 current width Isrc_width control signal as examples. The calibration timing is shown in FIG. 2 .

Coarse adjustment calibration: When the current intensity selection signal Isrc_sel<3:0>=d0, the current source array is disconnected, and the analog-to-digital converter outputs the digital signal Data<15:0>=d8000 containing structured light interference, which exceeds the threshold d0. At this time, the first digital calibration module 6 starts to work, and the coarse adjustment calibration starts, increasing the current intensity selection signal Isrc_sel<3:0> to d1. At the same time, the switching timing of the first switch Sw1 is the same as the LED pulse (LEDPulse) of the LED transmitting end. The current source array 2 compensates the structured photocurrent, and the digital signal Data<15:0> decreases from d8000 to d5000. Since it is still greater than the threshold value d0, the current intensity selection signal Isrc_sel<3:0> continues to increase to d2, and the digital signal Data<15:0> decreases to -1000. At this time, the digital signal Data<15:0> is less than the threshold value d0, and the first digital calibration module 6 stops working, and the current intensity selection signal Isrc_sel<3:0> is locked to d2;

Fine-tuning calibration: When the coarse-tuning calibration is completed and the current intensity selection signal Isrc_sel<3:0> is locked to d2, the fine-tuning calibration begins. By gradually reducing the width of the control signal current width Isrc_width of the second switch array Sw2 Array, the current source of the current source array 2 flowing into the integrator 4 is fine-tuned to compensate for the structured light current. As the current width Isrc_width signal width decreases, the digital signal Data<15:0> gradually increases in steps of d100. When the digital signal Data<15:0>=d5, it meets the requirement that the structured light threshold is greater than 0 and less than d20, and the first digital calibration module 6 stops working. At this time, the current width Isrc_width signal width is locked, and the structured light interference elimination is completed.

In the preferred embodiment of the present invention, it also has the function of a low-noise proximity light sensor, which controls the size of the matching capacitor array 3 through the second digital calibration module 7 to match the parasitic capacitance 11 of the photodiode 1, thereby reducing the integrator noise. The calibration timing is shown in FIG3:

When the matching capacitor array Cdummy<3:0>=d0, the initial noise jitter of the digital signal Data<15:0> is 200, and the second digital calibration module determines that its value exceeds the jitter threshold 10, and the second digital calibration module starts working. The matching capacitor array Cdummy<3:0> starts to increase gradually, and the capacitance value gradually increases. When its value increases to d3, the digital signal noise jitter (Data jitter) decreases to 8, and its value is less than the jitter threshold 10. The second digital calibration module stops working, and the matching capacitor array Cdummy<3:0> is locked to d3, and the noise calibration is completed.

The present invention provides an adaptive proximity light detection sensor for use in the field of mobile phones or tablet computers, wherein the LED driving current is 100mA, the LED on time is 1ms, the full scale of the analog-to-digital converter is 65535Code, the proximity light response data at a distance of 3cm is 38000Code, the data for the air structured light is reduced to less than 20Code, and the noise jump is 10Code. After actual testing, the test results of the preferred embodiment of the present invention are compared with the prior art. In the prior art, the digital signal output by the analog-to-digital converter ADC is 8000LSB, and the digital signal noise jump is 200LSB, while the corresponding values of the present invention are 5LSB and 8LSB. It can be seen that the scheme and embodiments disclosed in the present invention have obvious technical progress, and are an adaptive proximity light detection sensor, which is particularly applicable to the mass production of mobile phones or tablet computers, and can adaptively reduce the proximity light sensor noise, and improve and optimize the performance of the optical sensor.

It should be understood that the scope of the present invention is not limited to the non-limiting embodiments, and it should be understood that the non-limiting embodiments are only described as examples. The substantial protection scope required by this application is more reflected in the scope provided by the independent claims, as well as its dependent claims.

Claims (10)

1. An adaptive proximity light detection sensor, the receiving end of the sensor comprising: a photodiode, an integrator and an analog-to-digital converter, the digital signal output by the analog-to-digital converter contains data of structured light interference, characterized in that: the receiving end also includes a current source array and a first digital calibration module, the current source array and the photodiode are arranged in parallel and connected to the non-inverting input end of the integrator, the first digital calibration module collects the digital signal and performs feedback calibration on the current of the current source array to reduce the component of the structured light interference in the digital signal. 2. An adaptive proximity light detection sensor according to claim 1, characterized in that: the feedback calibration includes: the digital signal passes through the first digital calibration module, first adjusting the current intensity of the current source array to perform a coarse calibration on the current flowing through the integrator, and then adjusting the current width of the current output by the current source array to perform a fine calibration on the current flowing through the integrator. 3. An adaptive proximity light detection sensor according to claim 2, characterized in that: the transmitting end of the sensor is an LED transmitting end, the LED transmitting end has an LED switch to turn on and off the LED lamp in the LED transmitting end to control the light emission, the integrator has a negative feedback circuit at the positive input end, the negative feedback circuit at the positive input end is an integrating capacitor, the receiving end also includes a comb filter, and the digital signal is connected to the first digital calibration module after passing through the comb filter. 4. An adaptive proximity light detection sensor according to claim 3, characterized in that: the photodiode receives the reflected light from the LED transmitting end and converts it into a current signal, the current signal flows out through the integrator and the integrating capacitor and is converted into a voltage signal, and the voltage signal flows out through the analog-to-digital converter and the comb filter and is converted into the digital signal. 5. An adaptive proximity light detection sensor according to claim 4, characterized in that: a first switch is arranged between the photodiode and the integrator, and the first switch controls the current signal converted by the photodiode to the integrator; one end of the current source array is connected to the power supply terminal VDD, and a second switch array corresponding to and matching the current source array is arranged between the other end of the current source array and the non-inverting input terminal of the integrator, and the first digital calibration module controls the reduction of the current intensity and the width of the current output by the current source array through the second switch array. 6. An adaptive proximity light detection sensor according to claim 5, characterized in that: the digital signal Data<15:0>, the current strength selection signal Isrc_sel<3:0>, in the first coarse adjustment calibration, when the digital signal Data<15:0> decreases to less than the threshold value d0, the first digital calibration module stops working, and the current strength selection signal Isrc_sel<3:0> is locked to d2, and in the subsequent fine adjustment calibration, as the current width signal width decreases, the digital signal Data<15:0> gradually increases, and when the requirement that the structured light threshold is greater than 0 and less than d20 is met, the first digital calibration module stops working, and at this time, the current width signal width is locked, and the structured light interference elimination is completed. 7. An adaptive proximity light detection sensor according to claim 1, characterized in that: the receiving end further includes: a matching capacitor and a second digital calibration module, the matching capacitor is connected to the negative phase input terminal of the integrator, the integrator has a negative feedback circuit at the negative phase input terminal, the negative feedback circuit at the negative phase input terminal is a capacitor, and the second digital calibration module collects the digital signal and performs noise calibration on the matching capacitor to reduce the noise of the proximity light sensor. 8. An adaptive proximity light detection sensor according to claim 7, characterized in that: the noise calibration is that the digital signal is calibrated on the matching capacitor through the second digital calibration module, and the matching capacitor is matched with the parasitic capacitance of the photodiode by adjusting the capacitance of the negative feedback circuit at the negative phase input end, thereby reducing the noise interference of the integrator and reducing the noise jump of the digital signal. 9. An adaptive proximity light detection sensor according to claim 8, characterized in that: the parasitic capacitor is arranged in parallel with the photodiode and has a ground terminal, the other end of the parasitic capacitor connected in parallel with the photodiode is connected to the first switch, one end of the matching capacitor is grounded, and a third switch array corresponding to the matching capacitor is arranged between the other end of the matching capacitor and the negative phase input terminal of the integrator, and the second digital calibration module acts on the third switch array. 10. An adaptive proximity light detection sensor according to any one of claims 7 to 9, characterized in that: it is applied to the field of mobile phones or tablet computers, the LED driving current is 100mA, the LED turn-on time is 1ms, the full scale of the analog-to-digital converter is 65535Code, the proximity light response data at a distance of 3cm is 38000Code, the air structured light data is reduced to less than 20Code, and the noise jump is 10Code.