CN118431210A - Wearable device - Google Patents

Abstract

The present application provides a wearable device, which relates to the field of terminal technology. The wearable device includes a PPG module; the PPG module includes a light-emitting unit, and the light-emitting unit includes a packaging substrate, a light-emitting chip layer, and a packaging adhesive layer arranged along a first direction; the light-emitting unit also includes a first microlens layer arranged on the side of the packaging adhesive layer away from the light-emitting chip layer, and/or, a second microlens layer arranged on the side of the light-emitting chip layer away from the packaging substrate; the first microlens layer and the second microlens layer are both used to enhance the luminous flux and change the light shape. The wearable device improves the light output efficiency by adding the first microlens layer and/or the second microlens layer in the light-emitting unit.

Description

Wearable device

Technical Field

The present application relates to the field of terminal technology, and in particular to a wearable device.

Background technique

With the explosive growth of wearable devices such as smart watches and sports bracelets, more and more functions are integrated into wearable devices. For example, users can use wearable devices to measure vital signs such as heart rate, pulse or blood oxygen saturation.

When measuring vital signs, wearable devices can use photoplethysmography (PPG) based on light-emitting units and light-receiving units to measure the attenuated light after reflection and absorption by human blood vessels and tissues, record the pulsation state of blood vessels and measure pulse waves.

In the above method, the light extraction efficiency of the light emitted by the light-emitting unit through the back cover of the wearable device is a key parameter affecting the PPG performance. However, in the prior art, this light extraction efficiency is not high, and a new design solution is urgently needed.

Summary of the invention

The present application provides a wearable device, which achieves the purpose of improving the light output efficiency of a light-emitting unit by adding one or more layers of microlens arrays in the light-emitting unit.

In a first aspect, a wearable device is provided, wherein the wearable device includes a PPG module;

The PPG module includes a light-emitting unit, and the light-emitting unit includes a packaging substrate, a light-emitting chip layer and a packaging glue layer arranged along a first direction;

The light-emitting unit further comprises a first microlens layer disposed on a side of the packaging glue layer away from the light-emitting chip layer, and/or a second microlens layer disposed on a side of the light-emitting chip layer away from the packaging substrate;

The first microlens layer and the second microlens layer are both used to enhance light flux and change light shape.

The first direction in the embodiment of the present application indicates the thickness direction of the light emitting unit, that is, direction z.

The embodiment of the present application provides a wearable device, wherein the light-emitting unit included in the PPG module of the wearable device includes, in addition to a packaging substrate, a light-emitting chip layer and a packaging adhesive layer, one or more layers of microlens arrays. The one or more layers of microlens arrays are arranged on the light-emitting side of the light-emitting chip layer, for example, on the light-emitting surface of the light-emitting chip layer, or on the packaging adhesive layer, to enhance the light-emitting efficiency of the light-emitting unit, or in other words, to enhance the luminous flux of the light-emitting unit.

Since the microlens array can also change the light path, it is also possible to adjust the light shape of the light-emitting chip layer, such as adjusting the light angle, light density distribution, etc.

In combination with the first aspect, in some implementations of the first aspect, the first microlens layer includes a plurality of first microlenses, and the first microlenses are first convex lenses composed of a first plane and a first convex surface;

The first plane is located at a side close to the packaging glue layer, and the first convex surface is located at a side away from the packaging glue layer.

In this implementation, since the first microlens is a first convex lens, the first plane is located on the side close to the encapsulation glue layer, and the first convex surface is located on the side away from the encapsulation glue layer, the surface area of the first microlens close to the air side is increased relative to the plane area, thereby enhancing the light extraction efficiency.

In combination with the first aspect, in some implementations of the first aspect, the refractive index of the first microlens layer is greater than the refractive index of air, and is less than or equal to the refractive index of the encapsulation glue layer.

In this implementation, when the refractive index of the first microlens is equal to the refractive index of the encapsulation glue layer, when the light is emitted from the encapsulation glue layer to the first microlens, the light undergoes a certain refraction and no total reflection occurs; and when the refractive index of the first microlens is less than the refractive index of the encapsulation glue layer, when the light is emitted from the relatively high refractive index encapsulation glue layer to the relatively low refractive index first microlens, the light undergoes refraction and total reflection, and the total reflection causes a certain reduction in the amount of light emitted; however, because the additional first microlens is in the shape of a convex lens, that is, because of the curvature of the first microlens, when the light is emitted from the relatively high refractive index first microlens to the relatively low refractive index air, the total reflection is destroyed relative to the plane emitted light, thereby improving a certain light output efficiency.

It should be understood that the “high” and “low” in the high refractive index and low refractive index described in the present application are relative and not fixed.

In combination with the first aspect, in some implementations of the first aspect, the plurality of first micro lenses are arranged in a first array on the encapsulation glue layer.

In this implementation, when arranged in the first array, the light shape of the light emitted into the air, such as the light emission angle and the density distribution of the light, can be adjusted by utilizing the array arrangement relationship between the plurality of first micro lenses.

In combination with the first aspect, in some implementations of the first aspect, the second microlens layer includes a plurality of second microlenses, and the second microlenses are second convex lenses composed of a second plane and a second convex surface;

The second plane is located at a side close to the light emitting chip layer, and the second convex surface is located at a side away from the light emitting chip layer.

In this implementation, since the second microlens is a second convex lens, the second plane is located on the side close to the light-emitting chip layer, and the second convex surface is located on the side away from the light-emitting chip layer, the surface area of the second microlens close to the encapsulation layer is increased relative to the plane area, thereby enhancing the light extraction efficiency.

In combination with the first aspect, in some implementations of the first aspect, the refractive index of the second microlens layer is greater than the refractive index of the encapsulation glue layer, and is less than or equal to the refractive index of the light-emitting chip layer.

In this implementation, when the refractive index of the second microlens is equal to the refractive index of the LED chip layer, when the light is emitted from the LED chip layer to the second microlens, the light undergoes a certain refraction and no total reflection occurs; and when the refractive index of the second microlens is less than the refractive index of the LED chip layer, when the light is emitted from the relatively high refractive index LED chip layer to the relatively low refractive index second microlens, the light undergoes total reflection, resulting in a certain reduction in the amount of light emitted. However, because the added second microlens is in the shape of a convex lens, that is, because of the curvature of the second microlens, when the light is emitted from the relatively high refractive index second microlens to the relatively low refractive index packaging glue layer, relative to the plane emitted light, the total reflection is destroyed, thereby also improving a certain light output efficiency.

In combination with the first aspect, in some implementations of the first aspect, the light-emitting chip layer includes a plurality of light-emitting chips arranged at intervals;

The plurality of second micro lenses are arranged in a second array on the light emitting chip.

In this implementation, when the second array arrangement is present, the light shape of the light emitted into the encapsulation glue layer, such as the light emission angle and the light density distribution, can be adjusted by utilizing the array arrangement relationship between the plurality of second micro lenses.

In combination with the first aspect, in some implementations of the first aspect, the first array type and the second array type are respectively at least one of the following:

Multi-row and multi-column style, circular ring form.

In combination with the first aspect, in some implementations of the first aspect, the light emitting chip is an LED chip, and the LED chip is at least one of the following:

Yellow LED chip, green LED chip, blue LED chip, red LED chip, cyan LED chip, orange LED chip, infrared LED chip;

Among them, the yellow LED chip is used to emit yellow light with a peak wavelength range of 550.0nm to 579.9nm; the green LED chip is used to emit filtered light with a peak wavelength range of 510.0nm to 549.9nm; the cyan LED chip is used to emit cyan light with a peak wavelength range of 480.0nm to 509.9nm; the blue LED chip is used to emit blue light with a peak wavelength range of 450.0nm to 479.9nm; the red LED chip is used to emit red light with a peak wavelength range of 610.0nm to 699.9nm; the orange LED chip is used to emit a peak wavelength range of 580.0nm to 609.9nm; the infrared LED chip is used to emit infrared light with a peak wavelength range of 700.0nm to 1100.0nm.

It should be understood that in the embodiment of the present application, when the light-emitting chip is an LED chip, the light-emitting chip layer can also be referred to as an LED chip layer.

In this implementation, the light-emitting chip can be used to realize the emission of light of various colors. Based on this, the characteristic dimensions of the first microlens and the second microlens can be adaptively adjusted and prepared according to the wavelength of the light, so as to achieve the purpose of improving the light output efficiency of light of different wavelengths, wherein the characteristic dimensions include curvature, diameter and filling ratio.

In combination with the first aspect, in some implementations of the first aspect, the first microlens array is prepared by a mold forming process.

In this implementation, the preparation method is simple and quick, and the characteristic size of the first microlens layer can be flexibly adjusted by adjusting the transfer size of the mold.

In combination with the first aspect, in certain implementations of the first aspect, the second microlens array is prepared by an etching and stripping process or an annealing process.

In this implementation, both the etching and stripping process and the annealing process are graphic processes. This application can prepare the second microlens on the LED chip on a large scale through the graphic process. The technology is mature, easy to implement, and low in cost.

In combination with the first aspect, in some implementations of the first aspect, the packaging substrate may be at least one of an epoxy molding compound substrate, a ceramic substrate, an aluminum substrate, a copper substrate, a silicon substrate, and the like.

In combination with the first aspect, in some implementations of the first aspect, when the packaging substrate is the ceramic substrate, the light-emitting chip layer is fixed on the ceramic substrate by flip-chip bonding.

In this implementation, the LED chip is fixed using flip-chip technology, the interconnection line between the LED chip and the driving circuit in the packaging substrate is short, and the parasitic capacitance and parasitic inductance are very small.

In combination with the first aspect, in some implementations of the first aspect, the PPG module further includes a light receiving unit; the light emitting unit and the light receiving unit are arranged in the same layer on a plane perpendicular to the first direction.

In this implementation, since the light-emitting unit and the light-receiving unit are at the same distance from the human body, the light-receiving unit will not be affected by other factors such as distance when detecting vital sign information.

In combination with the first aspect, in some implementations of the first aspect, the wearable device is a smart watch or a smart bracelet.

An embodiment of the present application provides a wearable device, which includes a PPG module, the PPG module includes a light-emitting unit, the light-emitting unit includes a packaging substrate, a light-emitting chip layer (LED chip layer) and a packaging glue layer. The present application increases the amount of light output by adding a plurality of second microlenses arranged in a second array on the LED chip layer, utilizing the shape of each second microlens; and utilizing the array arrangement relationship between the plurality of second microlenses to adjust the light shape of the light emitted into the packaging glue layer, thereby adjusting the light shape of the light subsequently emitted into the air.

In addition, the embodiment of the present application also increases the light output by adding a plurality of first microlenses arranged in a first array on the encapsulation glue layer, utilizing the shape of the first microlenses; and utilizing the array arrangement relationship between the plurality of first microlenses to adjust the light shape of the light emitted into the air, such as the light output angle and the light density distribution.

It should be understood that the light output and light shape of the light finally emitted into the air will be affected by both the second microlens and the first microlens.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG1 is a usage state of a wearable device provided in an embodiment of the present application;

FIG2 is a schematic diagram of the structure of a wearable device provided in an embodiment of the present application;

FIG3 is a schematic top view of the PPG module shown in FIG2 ;

FIG4 is another schematic top view of the PPG module shown in FIG2 ;

FIG5 is a schematic diagram of the working principle of the PPG module provided by the related art;

FIG6 is a schematic structural diagram of a light emitting unit in the PPG module shown in FIG5 ;

FIG7 is a schematic diagram of a first structure of a light emitting unit provided in an embodiment of the present application;

FIG8 is a schematic structural diagram of the first microlens layer in FIG7;

FIG9 is a schematic diagram of a second structure of a light emitting unit provided in an embodiment of the present application;

FIG10 is a schematic structural diagram of the second microlens layer in FIG9 ;

FIG11 is a schematic diagram of a third structure of a light-emitting unit provided in an embodiment of the present application;

FIG12 is a schematic top view of the first microlens layer and the second microlens layer in FIG11 ;

FIG13 is a diagram of light output and light simulation corresponding to a light emitting unit provided in the related art;

FIG. 14 is a diagram showing the light output and light simulation corresponding to the light emitting unit provided in an embodiment of the present application.

Reference numerals:

1-wearable device; 2-skin; 10-PPG module; 11-light-emitting unit; 110-packaging substrate; 111-LED chip layer; 1110-LED chip; 112-packaging adhesive layer; 113-first microlens layer; 1130-first microlens; 114-second microlens layer; 1140-second microlens; 115-blocking wall; 12-light collecting unit.

Detailed ways

In order to make the purpose, technical solution and advantages of the embodiments of the present application clearer, the technical solution in the embodiments of the present application will be clearly and completely described below in conjunction with the drawings in the embodiments of the present application. Obviously, the described embodiments are part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

The term "and/or" in this article is a description of the association relationship of associated objects, indicating that there can be three relationships. For example, A and/or B can represent: A exists alone, A and B exist at the same time, and B exists alone. The symbol "/" in this article indicates that the associated objects are in an or relationship, for example, A/B means A or B.

The terms "first" and "second" in the specification and claims herein are used to distinguish different objects rather than to describe a specific order of objects. In the description of the embodiments of the present application, unless otherwise specified, the meaning of "multiple" refers to two or more than two, for example, multiple processing units refer to two or more processing units, etc.; multiple elements refer to two or more elements, etc.

FIG1 shows a use state of a wearable device provided in an embodiment of the present application. As shown in FIG1 , the wearable device 1 may be a smart watch. When the user wears the smart watch, the bottom of the smart watch (the side opposite to the display screen) may contact the user's skin 2. The embodiment of the present application does not specifically limit the form of the wearable device 1. For example, the wearable device 1 in the embodiment of the present application may also be a sports bracelet, a smart wristband, a smart ring, etc. The following embodiments are described by taking the wearable device 1 as a smart watch as an example.

Fig. 2 shows a schematic diagram of the structure of a wearable device 1 provided in an embodiment of the present application. As shown in Fig. 2, the wearable device 1 includes a PPG module 10, which can be arranged on the side of the wearable device 1 in contact with the human body, and is used to implement photoplethysmography, measure the attenuated light reflected and absorbed by human blood vessels and tissues, record the pulsation state of blood vessels, and measure vital signs such as pulse waves.

As shown in FIG. 2 , the PPG module 10 may include a light emitting unit 11 and a light receiving unit 12 .

The light-emitting unit 11 is used to emit light. For example, the light-emitting unit 11 may include one or more light-emitting diode (LED) chips, or the light-emitting unit 11 may include an LED chip (not shown in FIG. 2 ) and other devices. One LED chip may emit light of one color, and multiple LED chips may emit light of multiple colors or light of the same color. If the light-emitting unit 11 includes multiple LED chips, when the multiple LED chips emit light of a single color, the light-emitting unit 11 emits light of the same color; when the multiple LED chips emit light of multiple colors, the light-emitting unit 11 emits a mixture of multiple colors. The embodiment of the present application does not limit the light emission color of the LED chip and the light-emitting unit 11.

The light receiving unit 12 is used to receive light. It should be understood that the light received by the light receiving unit 12 in the PPG module 10 is the attenuated light after the light emitted by the light emitting unit 11 is reflected and absorbed by the blood vessels and tissues of the human body. The light receiving unit 12 can also be called a detector.

The above is an example of the PPG module 10 and the wearable device 1, and does not limit the PPG module 10 and the wearable device 1 of the present application. The PPG module 10 may also include other units, and the wearable device 1 may also include other modules.

In order to further illustrate the structure of the PPG module 10, FIG3 shows a schematic top view of a PPG module 10 provided in an embodiment of the present application; FIG4 shows a schematic top view of another PPG module 10 provided in an embodiment of the present application.

For example, if the wearable device 1 is a circular structure when viewed from a top view, the light-emitting unit 11 and the light-receiving unit 12 may be arranged around the center of the circle.

For example, as shown in FIG3 , the PPG module 10 in the wearable device 1 includes three light-emitting units 11 and three light-receiving units 12. The three light-emitting units 11 and the three light-receiving units 12 are arranged around the center of a circle. In addition, in order to emit and receive light evenly and obtain more accurate data during subsequent light receiving, the three light-emitting units 11 and the three light-receiving units 12 can be arranged at intervals.

For example, if the wearable device 1 has a rectangular structure when viewed from a top view, the light-emitting units 11 and the light-receiving units 12 may be arranged in rows or columns, or may be arranged in an array.

For example, as shown in FIG4 , the PPG module 10 in the wearable device 1 includes two light emitting units 11 and one light receiving unit 12 . The two light emitting units 11 are distributed on both sides of the light receiving unit 12 .

In the above two examples, each light-emitting unit 11 may include, for example, three LED chips, which may emit red light, green light and blue light respectively, and each LED chip is square in shape in the above top view.

FIG5 is a schematic diagram showing the working principle of the PPG module 10 provided by the related art.

1 to 5 , when the user wears the wearable device 1, the bottom of the wearable device 1 contacts the user's skin 2, and it can be considered that the PPG module 10 contacts the user's skin 2. When actually worn, there may still be a certain gap between the PPG module 10 and the skin 2 shown in FIG. 5 , and the gap is filled with air.

As shown in FIG5 , when the PPG module 10 is used for measurement, the multiple LED chips included in the light-emitting unit 11 can emit light toward the side of the skin 2, and the angle of the light is not limited. After the light enters the skin 2, due to changes in the blood flow dynamics of the human body, such as changes in heart rate or blood volume, the light entering the skin 2 will be scattered, thereby affecting the transmission and reflection of the light entering the skin 2; therefore, when the light passes through the skin 2 and then emits to the light receiving unit 12 in the PPG module 10, the light will be attenuated to a certain extent; the attenuated light can be converted into an electrical signal after being processed by the light receiving unit 12, and can be further used to analyze the fluctuation state of the blood vessels, measure pulse waves and other vital signs information; subsequently, the user can perform health management based on the vital signs information obtained from the above measurements.

Based on FIG5 , FIG6 shows a schematic diagram of the structure of the light-emitting unit 11 in the PPG module 10 shown in FIG5 . As shown in FIG6 , the light-emitting unit 11 is generally composed of a packaging substrate 110, an LED chip layer 111 and a packaging adhesive layer 112 in the direction toward the bottom of the wearable device 1, that is, in the direction toward the human skin (direction z shown in FIG5 and FIG6 ).

Among them, the packaging substrate 110 is used to provide support and drive. For example, the packaging substrate 110 may include multiple thin film field effect transistor (TFT) circuits (such as the black lines in the packaging substrate 110 shown in Figures 5 and 6) for driving the LED chip layer 111. The TFT circuit drives the LED chip layer 111 to emit light.

The encapsulation adhesive layer 112 is used to protect the LED chip layer 111 , and the encapsulation adhesive layer 112 is in a transparent state and is used to emit light emitted by the LED chip layer 111 .

The LED chip layer 111 may include, for example, three LED chips 111; on a plane perpendicular to the direction z, the three LED chips 111 are arranged at intervals, and the three LED chips 111 may respectively emit light of different colors or light of the same color. In the area on the packaging substrate 110 where the LED chips 111 are not arranged, the packaging glue layer 112 is in direct contact with the packaging substrate 110.

In addition, as shown in Figures 5 and 6, baffles 115 are provided on the left and right sides of the encapsulation glue layer 112, and the baffles 115 are used to block light and prevent the light emitted by the LED chip 111 from leaking from the left and right sides. The left and right sides refer to the left and right sides in a direction perpendicular to the direction z.

As shown in FIG. 5 and FIG. 6, when the wearable device 1 including the PPG module 10 structure is used to measure vital sign information, the higher the light output efficiency of the light emitting unit 11, the more attenuated light is received by the light receiving unit 12, and the higher the accuracy of the measured vital sign information; the lower the light output efficiency of the light emitting unit 11, the less attenuated light is received by the light receiving unit 12, and the lower the accuracy of the measured vital sign information. It can be seen that the light output efficiency of the light emitting unit 11 is a key parameter affecting the performance of PPG. However, in the prior art, due to the limitations of materials, structures, etc., a large amount of total reflection is generated inside the light emitting unit 11, resulting in a low light output efficiency of the light emitting unit 11, which in turn results in a low accuracy rate of measuring vital sign information. A new solution is urgently needed to solve this problem.

In view of this, an embodiment of the present application provides a wearable device, in which the light-emitting unit included in the PPG module of the wearable device includes not only a packaging substrate, an LED chip layer and a packaging adhesive layer, but also one or more layers of microlens arrays. The one or more layers of microlens arrays are arranged on the side of the LED chip layer where light is emitted, for example, on the surface where the LED chip layer emits light, or on the packaging adhesive layer, to enhance the light-emitting efficiency of the light-emitting unit, or in other words, to enhance the luminous flux of the emitted light.

Since the microlens array can also change the light path, it is also possible to adjust the light shape of the LED chip, such as adjusting the light angle, light density distribution, etc.

The structure of the light-emitting unit 11 in the wearable device provided in the embodiment of the present application is described in detail below in conjunction with Figures 7 to 12. Figures 7, 9 and 11 respectively show three structures of the light-emitting unit 11 provided in the embodiment of the present application. Figure 8 is a schematic diagram of the structure of the first microlens layer 113 in Figure 7; Figure 10 is a schematic diagram of the structure of the second microlens layer 114 in Figure 9; Figure 12 is a schematic diagram of a top view of the first microlens layer 113 and the second microlens layer 114 in Figure 11.

As shown in FIG. 7 , the light-emitting unit 11 of the first structure provided in the embodiment of the present application includes, in the direction z toward the bottom of the wearable device 1 , a packaging substrate 110 , an LED chip layer 111 and a packaging adhesive layer 112 .

Exemplarily, the packaging substrate 110 can be at least one of an epoxy mold compound (EMC) substrate, a ceramic substrate, an aluminum substrate, a copper substrate or a silicon substrate; in addition, other introductions to the packaging substrate 110 can refer to the introductions to the packaging substrate 110 in Figures 5 and 6, which will not be repeated here.

Exemplarily, the LED chip layer 111 may include three LED chips 1110, and each LED chip 1110 may be a yellow LED chip, a green LED chip, a blue LED chip, a red LED chip, a cyan LED chip, an orange LED chip, an infrared LED chip, etc. Among them, the yellow LED chip is used to emit yellow light with a peak wavelength range of 550.0nm to 579.9nm; the green LED chip is used to emit filtered light with a peak wavelength range of 510.0nm to 549.9nm; the cyan LED chip is used to emit cyan light with a peak wavelength range of 480.0nm to 509.9nm; the blue LED chip is used to emit blue light with a peak wavelength range of 450.0nm to 479.9nm; the red LED chip is used to emit red light with a peak wavelength range of 610.0nm to 699.9nm; the orange LED chip is used to emit a peak wavelength range of 580.0nm to 609.9nm; and the infrared LED chip is used to emit infrared light with a peak wavelength range of 700.0nm to 1100.0nm.

Exemplarily, the shape of each LED chip 1110 in the top view may be square, rectangular, circular or irregular, etc. In addition, the LED chip 1110 may also be changed to other non-LED light-emitting chips, and the embodiments of the present application do not impose any limitation on this.

For example, when the package substrate 110 is a ceramic substrate, the LED chip 1110 can be fixed on the ceramic substrate by flip-chip bonding. It should be noted that flip-chip bonding refers to a technology that directly interconnects the LED chip 1110 and the ceramic substrate, also known as flip-chip bonding.

The thickness of the encapsulation layer 112 along direction z (the dimension from the interface between the LED chip layer 111 and the encapsulation layer 112 to the interface between the encapsulation layer 112 and the air) is higher than the thickness of the LED chip layer 111. For other introductions, please refer to the introduction of the encapsulation layer 112 in the above Figures 5 and 6, which will not be repeated here.

On the basis of the above structure, as shown in FIG7 , the light-emitting unit 11 of the first structure provided in the embodiment of the present application, in addition to including a packaging substrate 110, an LED chip layer 111 and a packaging glue layer 112 in sequence, is also provided with a first microlens layer 113 on the side of the packaging glue layer 112 away from the LED chip layer 111.

The first microlens layer 113 includes a plurality of first microlenses 1130 . The plurality of first microlenses 1130 are arranged in a first array on a surface of the encapsulation layer 112 away from the LED chip layer 111 .

It should be understood that the first array arrangement refers to the arrangement of the plurality of first microlenses 1130 in a certain arrangement order, which may include, for example, multiple rows and columns, a circumferential ring, etc. There may be no gap between two adjacent first microlenses 1130, or there may be a certain gap. The specific arrangement of the first microlenses 1130, whether there is a gap, and the size of the gap can be set as needed, and the embodiment of the present application does not impose any limitation on this.

Each first microlens 1130 is in a transparent state, so that the light emitted from the LED chip layer 111 and transmitted through the packaging glue layer 112 is transmitted through the first microlens 1130 and then emitted into the air, and then transmitted to the user's skin 2.

The first microlens layer 113 also has an adjustable characteristic size, which may include a curvature, a diameter, a filling ratio, etc. corresponding to the first microlens 1130 .

It should be understood that in order to increase the surface area of the first microlens 1130 close to the air side and enhance light emission, each first microlens 1130 may be convex, that is, the first microlens 1130 may be called a first convex lens, and the first convex lens is composed of a first plane and a first convex surface. For example, as shown in (a) of FIG8 , the first convex surface of the first microlens 1130 is a hemispherical surface, and the curvature of the first microlens 1130 is γ ₁ .

For example, as shown in (a) of FIG. 7 and FIG. 8 , the shape of the first microlens 1130 may be a hemisphere, wherein the bottom surface (circular in the top view) of the hemisphere contacts the encapsulation glue layer 112 , and the hemispherical surface of the hemisphere is close to the air side.

As shown in (b) of FIG8 , the diameter of the hemispherical first microlens 1130 may be d ₁ ; when the length of the package substrate 110 is represented by L _x1 , the width is represented by L _y1 , and the plurality of first microlenses 1130 are arranged in a multi-row and multi-column manner, M _x1 first microlenses 1130 with a diameter of d ₁ may be arranged in the length direction, and N _y1 first microlenses 1130 with a diameter of d 1 may be arranged in the width direction. At this time, the filling ratio T ₁ of the first microlens 1130 may be calculated according to the following formula:

T ₁ =(πd ₁ ² ×M _x1 ×N _y1 )/(4×L _x1 ×L _y1 );

Assuming that the package substrate 110 is square, L _x1 =L _y1 , the filling ratio T ₁ of the first microlens 1130 can be:

T ₁ =(πd ₁ ² ×M _x1 ×N _y1 )/(2L ₁ ) ² ;

It should be understood that, since the amount of light output needs to be increased, a material with a first refractive index can be selected to make the first microlens 1130, so that the light can be refracted at least on the surface of the first microlens 1130 close to the air, and the incident angle of the light is smaller than the refraction angle. Then, the first refractive index needs to meet the conditions of being greater than the refractive index of air and less than or equal to the refractive index of the encapsulation glue layer 112.

For example, if the refractive index of the encapsulation layer 112 is 1.6 and the refractive index of air is 1, the first refractive index corresponding to the first microlens 1130 must satisfy the condition of being greater than 1 and less than or equal to 1.6. For example, the refractive index of the first microlens 1130 can be 1.4, 1.5, 1.6, etc.

It should be understood that when the refractive index of the first microlens 1130 is equal to the refractive index of the encapsulation layer 112, when the light is emitted from the encapsulation layer 112 to the first microlens 1130, the light undergoes a certain refraction and no total reflection occurs; and when the refractive index of the first microlens 1130 is less than the refractive index of the encapsulation layer 112, when the light is emitted from the relatively high refractive index encapsulation layer 112 to the relatively low refractive index first microlens 1130, the light undergoes refraction and total reflection, and the total reflection causes a certain reduction in the amount of light emitted; however, because the additional first microlens 1130 is in the shape of a convex lens, that is, because of the curvature of the first microlens 1130, when the light is emitted from the relatively high refractive index first microlens 1130 to the relatively low refractive index air, the total reflection is destroyed relative to the plane emitted light, thereby improving a certain light extraction efficiency.

Exemplarily, when the first refractive index corresponding to the first microlens 1130 is between the range of 1.4 and 1.6, the first microlens 1130 can be at least one of a polycarbonate lens, a polymethyl methacrylate lens, a glass lens, a silicone lens or an epoxy resin lens; of course, the first microlens 1130 can also be other lenses that meet the first refractive index requirements, and the embodiments of the present application do not impose any limitations on this.

In the embodiment of the present application, the first microlens layer 113 can be transferred onto the surface of the encapsulation glue layer 112 by using a molding process, which is simple and quick. Subsequently, the first microlenses 1130 with different characteristic sizes can be adjusted by adjusting the transfer size of the molding mold, thereby achieving flexible adjustment of the first microlens layer 113.

The light-emitting unit 11 provided in the embodiment of the present application increases the light output by adding a plurality of first micro-lenses 1130 arranged in a first array on the encapsulation glue layer 112, and utilizes the shape of the first micro-lenses 1130; and utilizes the array arrangement relationship between the plurality of first micro-lenses 1130 to adjust the light shape of the light emitted into the air, such as the light output angle and the light density distribution.

As shown in FIG. 9 , the light-emitting unit 11 of the second structure provided in the embodiment of the present application includes, in the direction z toward the wearable device 1 , a packaging substrate 110 , an LED chip layer 111 and a packaging adhesive layer 112 .

For the introduction of the packaging substrate 110 , the LED chip layer 111 and the packaging adhesive layer 112 , reference may be made to the introduction in FIG. 7 and FIG. 8 , which will not be described in detail herein.

On the basis of the above structure, as shown in FIG9 , the light-emitting unit 11 of the second structure provided in the embodiment of the present application, in addition to including a packaging substrate 110, an LED chip layer 111 and a packaging glue layer 112 in sequence, is also provided with a second microlens layer 114 on the side of the LED chip layer 111 away from the packaging substrate 110, that is, between the LED chip layer 111 and the packaging glue layer 112.

The second microlens layer 114 includes a plurality of second microlenses 1140 arranged in a second array on the surface of the LED chip layer 111 away from the package substrate 110. It should be understood that the second microlens layer 114 can be disposed only in the region where the LED chip layer 111 is disposed.

It should be understood that the second array arrangement refers to the plurality of second microlenses 1140 being arranged in a certain arrangement order, for example, it may include: multiple rows and columns, circumferential rings, etc.; there is no gap between two adjacent second microlenses 1140, or there may be a certain gap. The specific arrangement of the second microlenses 1140, whether there is a gap, and the size of the gap can be set as needed, and the embodiment of the present application does not impose any limitation on this.

Each second microlens 1140 is in a transparent state, so that the light emitted from the LED chip layer 111 is transmitted through the second microlens 1140 and then emitted into the packaging glue layer 112. Subsequently, it is transmitted through the packaging glue layer 112 and then emitted into the air, and then transmitted to the user's skin 2.

The second microlens layer 114 also has an adjustable characteristic size, which may include a curvature, a diameter, a filling ratio, etc. corresponding to the second microlens 1140 .

It should be understood that in order to increase the surface area of the second microlens 1140 close to the encapsulation glue layer 112 and enhance light emission, each second microlens 1140 may be convex, that is, the second microlens 1140 may be called a second convex lens, and the second convex lens is composed of a second plane and a second convex surface. For example, as shown in (a) of FIG. 10 , the convex side of the second microlens 1140 is a hemispherical surface, and the curvature of the second microlens 1140 is γ ₂ .

Exemplarily, as shown in (a) of Figures 9 and 10, the shape of the second microlens 1140 can be a hemisphere, the bottom surface (circular in the top view) included in the hemisphere is in contact with the LED chip layer 111, and the hemispherical surface included in the hemisphere is close to the side of the encapsulation glue layer 112.

As shown in (b) of FIG. 10 , the diameter of the hemispherical second microlens 1140 may be d ₂ ; when the length of the packaging substrate 110 is represented by L _x2 , the width is represented by L _y2 , and the plurality of second microlenses 1140 are arranged in a plurality of rows and columns, M _x2 second microlenses 1140 with a diameter of d ₂ may be arranged in the length direction, and N _y2 second microlenses 1140 with a diameter of d 2 may be arranged in the width direction. At this time, the filling ratio T ₂ of the second microlens 1140 may be calculated according to the following formula:

T ₂ =(πd ₂ ² ×M _x2 ×N _y2 )/(4×L _x2 ×L _y2 );

Assuming that the package substrate 110 is square, L _x2 =L _y2 , the filling ratio T ₂ of the second microlens 1140 can be:

T ₂ =(πd ₂ ² ×M _x2 ×N _y2 )/(2L ₂ ) ² ;

The embodiment of the present application may use an etching and stripping process or an annealing process to prepare the second microlens layer 114 ; the embodiment of the present application may also use other graphic processes to prepare the second microlens layer 114 , and the specific selection of the process depends on the material properties of the LED chip 111 .

Exemplarily, the etching and stripping process is applicable to any LED chip material; if the etching and stripping process is used, the LED chip layer 111 and the second microlens layer 114 need to be made separately. For example, a lens film including the second microlens layer 114 can be prepared on a base substrate (such as a glass substrate) by an etching method, and then the lens film can be stripped from the base substrate by a laser stripping method, and transferred to the LED chip layer 111 for bonding and dicing, so that LED chip layers 111 with the second microlens layer 114 can be obtained one by one.

Exemplarily, the annealing process can be applied to LED chip materials with a passivation layer on the surface; for example, GaN LED chips can be annealed, and polystyrene can be annealed at 150 degrees. If the annealing process is used, the second microlens layer 114 can be directly prepared on the LED chip layer 111. For example, a cylindrical array with a diameter of _d2 can be etched on the surface of the LED chip layer 111, and then annealing is used to make the cylindrical array become a tiny hemisphere under the action of thermal stress, so that the LED chip layer 111 with the second microlens layer 114 can be obtained.

It should be understood that since it is necessary to increase the amount of light output, a material with a second refractive index can be selected to make the second microlens 1140, so that the light can be refracted at least on the surface of the second microlens 1140 close to the encapsulation layer 112, and the incident angle of the light is less than the refraction angle. Then, the second refractive index needs to meet the conditions of being greater than the refractive index of the encapsulation layer 112 and less than or equal to the refractive index of the LED chip layer 111. It should be noted that the refractive index of the LED chip layer 111 refers to the refractive index of the light-emitting surface included in the LED chip 1110 itself.

For example, if the refractive index of the LED chip layer 111 is 2.6 and the refractive index of the encapsulation glue layer 112 is 1.5, the second refractive index corresponding to the second microlens 1140 needs to satisfy the condition of being greater than 1.5 and less than or equal to 2.6. For example, the refractive index of the second microlens 1140 can be 1.6, 1.8, 2.5, etc.

It should be understood that when the refractive index of the second microlens 1140 is equal to the refractive index of the LED chip layer 111, when the light is emitted from the LED chip layer 111 to the second microlens 1140, total reflection does not occur; and when the refractive index of the second microlens 1140 is less than the refractive index of the LED chip layer 111, when the light is emitted from the relatively high refractive index LED chip layer 111 to the relatively low refractive index second microlens 1140, total reflection will occur, resulting in a decrease in the amount of light emitted. However, because the additional second microlens 1140 is in the shape of a convex lens, that is, because of the curvature of the second microlens 1140, when the light is emitted from the relatively high refractive index second microlens 1140 to the relatively low refractive index packaging glue layer 112, relative to the plane emitted light, total reflection is destroyed, thereby also being able to improve a certain light extraction efficiency.

For example, when the second refractive index corresponding to the second microlens 1140 is in the range of 1.5 to 2.6, the second microlens 1140 may be at least one of a silicon oxide lens, a silicon carbide lens, and a silicon nitride lens. Of course, the second microlens 1140 may also be other silicon-based lenses that meet the second refractive index requirements, and the present application embodiment does not impose any limitation on this.

The light-emitting unit 11 provided in the embodiment of the present application, by adding a plurality of second microlenses 1140 arranged in a second array on the LED chip layer 111, can increase the light output by utilizing the shape of each second microlens 1140; and utilize the array arrangement relationship between the plurality of second microlenses 1140 to adjust the light shape of the light emitted into the encapsulation glue layer 112, and further can adjust the light shape of the light subsequently emitted into the air, such as the light emission angle of the light and the density distribution of the light.

In addition, the second microlens 1140 can be prepared on a large scale on the LED chip 1110 through a patterning process, which has mature technology, is easy to implement, and has low cost.

As shown in FIG. 11 , the light-emitting unit 11 of the third structure provided in the embodiment of the present application includes, in the direction z toward the wearable device 1 , a packaging substrate 110 , an LED chip layer 111 and a packaging adhesive layer 112 .

For the introduction of the packaging substrate 110 , the LED chip layer 111 and the packaging adhesive layer 112 , reference may be made to the introduction in FIG. 7 and FIG. 8 , which will not be described in detail herein.

On the basis of the above structure, as shown in FIG11 , the light-emitting unit 11 of the third structure provided in the embodiment of the present application includes, in addition to the packaging substrate 110, the LED chip layer 111 and the packaging glue layer 112 in sequence, a first microlens layer 113 is further provided on the side of the packaging glue layer 112 away from the LED chip layer 111; and a second microlens layer 114 is further provided on the side of the LED chip layer 111 away from the packaging substrate 110, that is, between the LED chip layer 111 and the packaging glue layer 112.

For the introduction of the first microlens layer 113 , reference may be made to the introduction in FIGS. 7 and 8 , and for the introduction of the second microlens layer 114 , reference may be made to the introduction in FIGS. 9 and 10 , which will not be described in detail herein.

It should be understood that the array arrangement of the plurality of first microlenses 1130 included in the first microlens layer 113 and the array arrangement of the plurality of second microlenses 1140 included in the second microlens layer 114 may be the same or different. For example, the first microlens layer 113 is arranged in a first array of multiple rows and columns, and the second microlens layer 114 is arranged in a second array of a circumferential ring. The specific arrangement of the first microlens layer 113 and the second microlens layer 114 can be set as needed, and the embodiment of the present application does not limit this in any way.

It should be understood that the adjustable characteristic sizes of the first microlens layer 113 and the second microlens layer 114 can be the same or different. For example, as shown in FIG12, when setting, the curvature corresponding to the second microlens 1140 can be smaller than the curvature corresponding to the first microlens 1130, the diameter corresponding to the second microlens 1140 can also be smaller than the curvature corresponding to the first microlens 1130, and the filling ratio corresponding to the second microlens 1140 is greater than the filling ratio corresponding to the first microlens 1130. The specific setting can be as needed, and the embodiment of the present application does not impose any limitation on this.

The technology for preparing the first microlens layer 113 and the second microlens layer 114 in the embodiment of the present application can refer to the description in the above two embodiments, which will not be repeated here.

It should also be understood that the first microlens 1130 in the first microlens layer 113 and the microlens 1140 in the second microlens layer 114 are both in a transparent state, and the second refractive index corresponding to the second microlens 1140 needs to be greater than the refractive index of the encapsulation layer 112, and less than or equal to the refractive index of the LED chip 1110. The first refractive index corresponding to the first microlens 1130 needs to be greater than the refractive index of air, and less than or equal to the refractive index of the encapsulation layer 112. It can be seen that the second refractive index corresponding to the second microlens 1140 is greater than the first refractive index corresponding to the first microlens 1130.

For example, if the refractive index of the LED chip 1110 is 2.6, the refractive index of the encapsulation layer 112 is 1.5, and the refractive index of air is 1, then the second refractive index corresponding to the second microlens 1140 can be 1.8, and the first refractive index corresponding to the first microlens 1130 can be 1.5, and the second refractive index is greater than the first refractive index.

It should be understood that since the second microlens 1140 is added to the LED chip layer 111 and the first microlens 1130 is added to the packaging glue layer 112, the second microlens 1140 and the first microlens 1130 both destroy the total reflection, so that the increased light output is stronger than the increased light output by only destroying it once in the above two embodiments.

The light-emitting unit 11 provided in the embodiment of the present application increases the light output by adding a plurality of second microlenses 1140 arranged in a second array on the LED chip layer 111, and uses the shape of each second microlens 1140 to increase the light output; and uses the array arrangement relationship between the plurality of second microlenses 1140 to adjust the light shape of the light emitted into the encapsulation layer 112, thereby adjusting the light shape of the light subsequently emitted into the air. In addition, the embodiment of the present application also increases the light output by adding a plurality of first microlenses 1130 arranged in a first array on the encapsulation layer 112, and uses the shape of the first microlenses 1130 to increase the light output; and uses the array arrangement relationship between the plurality of first microlenses 1130 to adjust the light shape of the light emitted into the air, such as the light output angle and the light density distribution.

It should be understood that the light output and light shape of the light finally emitted into the air will be affected by both the second microlens 1140 and the first microlens 1130 .

Subsequently, when the light-emitting unit 11 provided in the embodiment of the present application is applied to the PPG module 10 in the wearable device 1 described above, the accuracy of the PPG module 10 in measuring vital sign information can be improved by improving the light-emitting efficiency of the light-emitting unit 11, thereby improving the user's experience of wearing the wearable device 1 for health management.

It should be noted that the three light emitting unit 11 structures provided above are only three examples, and the microlens array provided in the light emitting unit 11 may also be provided in other interlayer relationships, or a multi-layer microlens array may also be provided.

For example, a plurality of second microlens layers 114 may be added on the LED chip 111 , and a plurality of second microlenses 1140 in the plurality of second microlens layers 114 may overlap with each other in the direction z, or may be arranged in a staggered manner.

For another example, a plurality of first microlens layers 113 may be disposed on the encapsulation glue layer 112 , and a plurality of first microlenses 1130 in the plurality of first microlens layers 113 may overlap with each other in the direction z, or may be arranged in a staggered manner.

In addition, in the light-emitting unit 11 provided in the embodiment of the present application, retaining walls 115 are also provided on the left and right sides of the packaging glue layer 112 .

The above text describes the use state and internal structure of the wearable device 1 provided in the embodiment of the present application in combination with Figures 1 to 12. The following text will introduce the simulated effects of the structure of the light-emitting unit 11 provided by the related art and the structure of the first type of light-emitting unit 11 provided in the embodiment of the present application in combination with Figures 6, 7, 13 and 14.

For example, taking the structure of the light emitting unit 11 provided by the related art shown in FIG6 as an example, the parameters provided in Table 1 and other parameters except the first microlens layer 113 provided in Table 2 are set. Taking the structure of the light emitting unit 11 provided by the embodiment of the present application shown in FIG7 as an example, the parameters provided in Tables 1 and 2 are set.

interface Reflectivity Transmittance Retaining wall coating 0.88 0.12 Encapsulation glue bottom coating 0.92 0.08 LED chip bottom coating 0.95 0.05

Table 1

Material Refractive Index Absorption rate (mm ^-1 ) First microlens layer 1.51 0.05 LED chip light emitting surface 2.5 5 Encapsulation glue layer 1.51 0.05

Table 2

In Table 1, the bottom coating of the encapsulation layer refers to a coating applied between the encapsulation substrate 110 and the encapsulation layer 112 in an area on the encapsulation substrate 110 where no LED chip 111 is disposed, and the coating is used to block light leakage.

The LED chip bottom coating refers to a coating applied between the packaging substrate 110 and the LED chip 111 in the region where the LED chip 111 is disposed on the packaging substrate 110, and the coating is used to block light leakage. The LED chip bottom coating may be a reflector made of silver (Ag).

In combination with the above-set parameters, for the light-emitting unit 11 provided by the related art shown in FIG. 6 , the distribution of the simulated light output is shown in FIG. 13 (a), and the light shape is shown in FIG. 13 (b).

In (a) of FIG. 13 , the horizontal coordinate X and the vertical coordinate Y are used to indicate the size, in millimeters; the bar graph on the left is used to indicate the corresponding relationship between color and luminous flux, in W/m ² . In conjunction with (a) of FIG. 13 , it can be seen that for the light-emitting unit 11 provided by the related art, the simulation can obtain that the total luminous flux corresponding to the light-emitting unit 11 is 0.43167W, and the ratio of the luminous flux to the emitted luminous flux is 0.43167. Therefore, it can be seen that the light extraction rate of the light-emitting unit 11 is about 43.1%.

It should be understood that the emitted luminous flux can be understood as the luminous flux emitted by the LED chip 1110, corresponding to a light power of 1W.

In (b) of FIG13 , the left rectangle is the light-emitting unit 11, the right rectangle is used to indicate the user's skin 2, and the line between the light-emitting unit 11 and the skin 2 is used to indicate light. It can be seen that due to the total reflection inside the light-emitting unit 11, the light after multiple reflections is absorbed by the barrier coating and the bottom coating of the encapsulation glue layer, so that a large amount of light is not emitted; the light after emission is partially sparse and partially dense, and the distribution is uneven.

Combined with the above-set parameters, for the light-emitting unit 11 provided in the embodiment of the present application shown in FIG7, the distribution of the simulated light output is shown in FIG14 (a), and the light shape is shown in FIG14 (b). The coordinates and lines in FIG14 and FIG13 have the same meanings and are not repeated here.

Combined with (a) in Figure 14, it can be seen that for the light-emitting unit 11 provided in the embodiment of the present application, the simulation can obtain that the total luminous flux corresponding to the light-emitting unit 11 is 0.70526W, and the ratio of the luminous flux to the emitted luminous flux is 0.70526. It can be seen that the light output rate of the light-emitting unit 11 is approximately 70.5%.

In (b) of FIG. 14 , the light emitting unit 11 is provided with a first microlens layer, which can effectively reduce the total internal reflection, so that more light is emitted and the distribution is more uniform.

By comparing FIG. 13 and FIG. 14 , it can be seen that the light-emitting unit 11 provided in the embodiment of the present application improves the light efficiency by more than 70%, and the luminous flux and light shape of the emitted light are better.

The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto. Any person skilled in the art who is familiar with the present technical field can easily think of changes or substitutions within the technical scope disclosed in the present application, which should be included in the protection scope of the present application. Therefore, the protection scope of the present application should be based on the protection scope of the claims.

Claims (15)

1. A wearable device, characterized in that the wearable device comprises a PPG module;

The PPG module comprises a light-emitting unit, wherein the light-emitting unit comprises a packaging substrate, a light-emitting chip layer and a packaging adhesive layer which are arranged along a first direction;

The light-emitting unit further comprises a first micro-lens layer arranged on one side of the packaging adhesive layer, which is far away from the light-emitting chip layer, and/or a second micro-lens layer arranged on one side of the light-emitting chip layer, which is far away from the packaging substrate;

the first microlens layer and the second microlens layer are used for enhancing luminous flux and changing light shape.

2. The wearable device of claim 1, wherein the first microlens layer comprises a plurality of first microlenses, the first microlenses being first convex lenses comprised of a first plane and a first convex surface;

The first plane is positioned at one side close to the packaging adhesive layer, and the first convex surface is positioned at one side far away from the packaging adhesive layer.

3. The wearable device of claim 2, wherein the refractive index of the first microlens layer is greater than the refractive index of air and less than or equal to the refractive index of the encapsulation glue layer.

4. The wearable device of claim 3, wherein the plurality of first microlenses are arranged in a first array on the encapsulation adhesive layer.

5. The wearable device of claim 4, wherein the second microlens layer comprises a plurality of second microlenses, the second microlenses being second convex lenses comprised of a second plane and a second convex surface;

the second plane is positioned at one side close to the light-emitting chip layer, and the second convex surface is positioned at one side far away from the light-emitting chip layer.

6. The wearable device of claim 5, wherein a refractive index of the second microlens layer is greater than a refractive index of the encapsulation glue layer and less than or equal to a refractive index of the light emitting chip layer.

7. The wearable device of claim 6, wherein the light emitting chip layer comprises a plurality of light emitting chips arranged at intervals;

The plurality of second microlenses are arranged in a second array on the light-emitting chip.

8. The wearable device according to claim 7, wherein the first array and the second array are each at least one of:

in the form of a plurality of rows and columns, and a circumferential ring.

9. The wearable device according to claim 7 or 8, wherein the light emitting chip is an LED chip, the LED chip being at least one of:

Yellow LED chip, green LED chip, blue LED chip, red LED chip, cyan LED chip, orange LED chip, infrared LED chip;

the yellow LED chip is used for emitting yellow light with the peak wavelength range of 550.0-579.9 nm; the green LED chip is used for filtering light with the emission peak wavelength range of 510.0-549.9 nm; the cyan LED chip is used for emitting cyan light with a peak wavelength range of 480.0 nm-509.9 nm; the blue LED chip is used for emitting blue light with the peak wavelength range of 450.0 nm-479.9 nm; the red LED chip is used for emitting red light with the peak wavelength range of 610.0 nm-699.9 nm; the orange LED chip is used for emitting light with the peak wavelength range of 580.0 nm-609.9 nm; the infrared LED chip is used for emitting infrared light with the peak wavelength range of 700.0 nm-1100.0 nm.

10. The wearable device according to any of claims 5-9, wherein the first microlens array is prepared by a mold forming process.

11. The wearable device according to any of claims 1 to 10, wherein the second microlens array is prepared by an etching lift-off process or an annealing process.

12. The wearable device of any of claims 1-11, wherein the packaging substrate is at least one of an epoxy molding compound substrate, a ceramic substrate, an aluminum substrate, a copper substrate, or a silicon substrate.

13. The wearable device of claim 12, wherein when the package substrate is the ceramic substrate, the light emitting chip layer is fixed on the ceramic substrate by flip chip bonding.

14. The wearable device of any of claims 1-13, wherein the PPG module further comprises a light receiving unit; the light emitting unit and the light receiving unit are arranged on the same layer on a plane perpendicular to the first direction.

15. The wearable device of any of claims 1-14, wherein the wearable device is a smart watch or a smart bracelet.