Film-coating-free high-precision illuminance sensor

Abstract

The invention discloses a coating-free high-precision illuminance sensor, and belongs to the technical field of illuminance sensors. The sensor comprises a channel I and a channel II; the first channel is a traditional illuminance detection scheme, and a photodiode in the second channel is shielded by a metal layer on the basis of a traditional photodiode. During detection, firstly, output data of the first channel and the second channel under different light sources are obtained; and then different light sources can be distinguished through the output data ratio of the channel I and the channel II during subsequent detection, and the detection value of the illumination intensity is obtained after data fitting is performed according to the light sources, so that the method can overcome the defect that the detection accuracy is high due to the deviation between the spectrum of the PN junction and the visual spectrum of human eyes. And therefore, the detection precision of the illumination sensor can be obviously improved, and the detection precision of the illumination sensor can be improved. And compared with the traditional solution, the invention does not bring extra cost and yield loss.

Description

Technical Field

[0001] The present invention belongs to the technical field of light intensity sensors, and in particular, relates to a high-precision light intensity sensor that does not require coating. Background Art

[0002] Smartphones and other mobile devices have quickly become ubiquitous around the world. It is common to see mobile phones and tablet computers in use in restaurants, waiting rooms, or on street corners. Mobile devices are used to play games, take photos, and make phone calls.

[0003] In the field of mobile phones and tablets, high-performance light intensity sensors are used as standard configurations to detect the intensity of ambient light. System designers can dynamically adjust the screen brightness of mobile phones and other display devices according to the intensity of ambient light to achieve the best display effect. Traditional CMOS-based light intensity detection solutions such as Figure 1 As shown in the figure, the photodiode is implemented by the PN junction inside the CMOS. When the device is exposed to light, it will generate a photocurrent, which is read by the amplifier and converted into a digital signal by the ADC (analog-to-digital converter). The size of the digital signal reflects the intensity of the light. Since the spectrum of the PN junction deviates from the visual spectrum of the human eye, Figure 2 In order to compare the spectral curves of PD and human vision, this solution will cause deviations between the intensity perceived by the human eye and the light intensity detection value under different light sources. To solve this problem, the traditional solution adds a layer of filter to the photosensitive area of ​​the chip to filter out the spectrum that the human eye cannot perceive, but this solution will bring additional costs and yield loss. Summary of the invention

[0004] The purpose of the present invention is to provide a high-precision illuminance sensor that does not require coating, and to provide a new idea for solving the problem of deviation between the intensity perceived by the human eye and the value of light intensity detection under different light sources.

[0005] The purpose of the present invention can be achieved by the following technical solutions:

[0006] A high-precision light intensity sensor without coating, comprising a channel one and a channel two;

[0007] The channel 1 includes a first photodiode, and the photocurrent generated by the first photodiode is read out by an amplifier 1 and then converted into a digital signal by an analog-to-digital converter 1;

[0008] The channel 2 includes a second photodiode, and the photocurrent generated by the second photodiode is read out by the amplifier 2 and converted into a digital signal by the analog-to-digital converter 2;

[0009] The first photodiode is a full spectrum structure;

[0010] The second photodiode has a metal layer laid between the photosensitive region and the SIO2 buffer layer to shield the visible light portion.

[0011] Furthermore, the metal layer is made of aluminum or copper.

[0012] Furthermore, the total thickness of the metal layer is 1-2 um.

[0013] Furthermore, the area of ​​the metal layer is larger than the area of ​​the PD, and the edge of the metal layer is extended by more than 20 um compared to the photosensitive area of ​​the second photodiode.

[0014] Furthermore, the working method of the light intensity sensor is:

[0015] Get the output data of channel 1 and channel 2 under different light sources;

[0016] Different light sources can be distinguished by the output data ratio of channel one and channel two, and then the detection value of light intensity can be obtained after data fitting based on the light source.

[0017] Furthermore, the data fitting method is: the correction coefficients of different light sources are calculated according to the data of channel one and channel two, and the calculation result of the data of channel one is multiplied by the correction coefficient to obtain the light intensity detection value.

[0018] Beneficial effects of the present invention:

[0019] 1. The present invention can overcome the problem of deviation between the intensity perceived by the human eye and the value of light intensity detection under different light sources due to the deviation between the spectrum of the PN junction and the visual spectrum of the human eye, thereby significantly improving the detection accuracy of the light sensor.

[0020] 2. Compared with the traditional method of adding a layer of filter to the photosensitive area of ​​the chip to filter out the spectrum that cannot be perceived by the human eye, the present invention does not bring additional costs and yield loss. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] The present invention will be further described below in conjunction with the accompanying drawings.

[0022] Figure 1 It is a traditional light intensity detection solution based on CMOS technology;

[0023] Figure 2 It is a comparison chart of the spectral curves of PD and human vision;

[0024] Figure 3 It is a structural schematic diagram of a high-precision light intensity sensor that does not require coating according to the present invention;

[0025] Figure 4 It is the spectrum curve of channel one and channel two;

[0026] Figure 5 It is a simplified structural diagram of the first photodiode and the second photodiode. DETAILED DESCRIPTION

[0027] 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.

[0028] A high-precision light sensor that does not require coating, such as Figure 3 As shown, it includes channel one and channel two;

[0029] The channel 1 includes a first photodiode. When the first photodiode is irradiated by light, a photocurrent is generated. The current is read by an amplifier 1 and converted into a digital signal by an analog-to-digital converter (ADC) 1. The magnitude of the digital signal reflects the intensity of the light.

[0030] The first photodiode is a conventional photodiode, where conventional refers to a photodiode implemented using a PN junction inside a CMOS;

[0031] The second channel includes a second photodiode. When the second photodiode is irradiated by light, a photocurrent is generated. The current is read by the second amplifier and converted into a digital signal by the second analog-to-digital converter.

[0032] The second photodiode is shielded by a metal layer on the basis of a traditional photodiode;

[0033] The spectra of the two channels are as follows: Figure 4 As shown in the figure, it can be seen that channel 1 can detect all light from 300 to 900 nm, while channel 2 is insensitive to the visible light part and can detect the non-visible light part;

[0034] like Figure 5 As shown, the first photodiode is a full-spectrum structure, and only a SIO2 buffer layer is retained above its photosensitive area;

[0035] The second photodiode has a metal layer between the photosensitive area and the SIO2 buffer layer to block the visible light. The material of the metal layer is compatible with the traditional CMOS process and can be made of aluminum or copper.

[0036] The total number of metal layers can be selected to be 1-3 layers, and the total thickness of the metal layer should be kept between 1-2um;

[0037] In addition, in order to ensure sufficient light shielding, the size of the metal layer should be larger than the area of ​​the PD. Specifically, the edge of the metal layer should extend beyond the photosensitive area of ​​the second photodiode by more than 20 um.

[0038] The method for detecting illuminance by using the above-mentioned high-precision illuminance sensor without coating is as follows:

[0039] Get the output data of channel 1 and channel 2 under different light sources;

[0040] Different light sources can be distinguished by the output data ratio of channel one and channel two, and then the detection value of light intensity can be obtained after data fitting based on the light source.

[0041] like Figure 4 As shown in the figure, due to the different spectral responses of the two channels, the main response area of ​​channel one is in the visible light region, and it will have a weak response to the infrared light source. The main response interval of channel two is above 850nm, which is the non-visible light and infrared light region. The two channels have obvious differences under different types of light sources.

[0042] Get the output data of channel 1 and channel 2 under the three light sources of CWF, A light, and D65. The specific results are as follows:

[0043] CWF CWF A light D65 Light intensity 500lux 1352lux 2340lux 1210lux Channel 1 940 2525 15129 4949 Channel 2 32 81 19463 4860 Channel 1 / Channel 2 ratio 29.37 31.17 0.7773 1.018

[0044] Since CWF light has the least infrared interference component, the basic light intensity parameters are calculated based on the channel 1 data and light intensity value under CWF light, and the light intensity value that can be represented by the channel 1 data is quantified. However, since channel 1 also has a certain response to the infrared region, the light intensity calculation results have a large deviation under the light sources D65 and A light with strong infrared light.

[0045] Through the data ratio of channel 1 and channel 2, the interference intensity of the infrared light in the light source on channel 1 can be clearly distinguished. The correction coefficients of different light sources are calculated according to the data of channel 1 and channel 2. The data calculation result of channel 1 is multiplied by the correction coefficient to obtain the light intensity detection values ​​of the three light sources of CWF, A light, and D65. The specific results are as follows:

[0046]

[0047] From the comparison data between the detection values ​​and the actual values ​​in the above table, it can be seen that the two-channel detection solution without coating proposed in the present invention can meet higher detection accuracy under different light sources, and can achieve a wider range of detection in conjunction with AFEs with different gains.

[0048] The above contents are merely examples and explanations of the present invention. Those skilled in the art may make various modifications or additions to the specific embodiments described or replace them in a similar manner. As long as they do not deviate from the invention or exceed the scope defined by the claims, they shall all fall within the protection scope of the present invention.

Claims

1. A high-precision light intensity sensor without coating, characterized in that: Includes channel one and channel two; The channel 1 includes a first photodiode, and the photocurrent generated by the first photodiode is read out by an amplifier 1 and then converted into a digital signal by an analog-to-digital converter 1; The channel 2 includes a second photodiode, and the photocurrent generated by the second photodiode is read out by the amplifier 2 and converted into a digital signal by the analog-to-digital converter 2; The first photodiode is a full spectrum structure; The second photodiode has a metal layer laid between the photosensitive region and the SIO2 buffer layer to shield the visible light portion.

2. A high-precision illuminance sensor without coating according to claim 1, characterized in that: The material of the metal layer is aluminum or copper.

3. A high-precision illuminance sensor without coating according to claim 2, characterized in that: The total thickness of the metal layer is 1-2 um.

4. The high-precision illuminance sensor without coating according to claim 3, characterized in that: The area of ​​the metal layer is larger than the area of ​​the PD, and the edge of the metal layer is extended by more than 20 um compared to the photosensitive area of ​​the second photodiode.

5. The high-precision illuminance sensor without coating according to claim 1, characterized in that: The working method of the light intensity sensor is: Get the output data of channel 1 and channel 2 under different light sources; Different light sources can be distinguished by the output data ratio of channel one and channel two, and then the detection value of light intensity can be obtained after data fitting based on the light source.

6. The high-precision illuminance sensor without coating according to claim 5, characterized in that: The data fitting method is: according to the data of channel one and channel two, the correction coefficients of different light sources are calculated, and the calculation result of the data of channel one is multiplied by the correction coefficient to obtain the light intensity detection value.

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