Skin detection optical sensor and wearable device

Abstract

The utility model provides a kind of skin detection optical sensor and wearable equipment, on structure, two transmitting chips are designed integrated in a packaging device with a receiving chip, and adopt hemispherical lens to package, enhance transmitting and receiving signal strength;While using light-tight package to separate transmitting chip and receiving chip horizontally, it is beneficial to the miniaturization of sensor.In detection scheme, the difference of the skin reflection intensity of 1050nm wavelength transmitting chip and 1450nm wavelength transmitting chip is utilized, and the reflection signal received by receiving chip is processed and calculated, whether the reflection object is skin can be accurately identified.

Description

Technical Field

[0001] This utility model relates to the field of sensor technology, and in particular to a skin detection optical sensor and wearable device. Background Technology

[0002] In wearable electronic devices such as TWS (True Wireless Stereo) earphones and VR (Virtual Reality) / AR (Augmented Reality) glasses, wear detection sensors are commonly built-in to reduce power consumption. These sensors currently all use 940nm infrared sensors, which work by detecting the intensity of reflected signals to determine the presence of obstructions: a strong signal is received when there is an obstruction, and a weak signal is received when there is no obstruction, thus achieving automatic control of "turning on when worn and turning off when removed".

[0003] However, infrared sensors have significant limitations. They can only identify whether an object is present, but cannot distinguish whether the object is a living being (such as human skin) or a non-living being (such as a tabletop or clothing). This directly leads to the device being prone to misjudgment. For example, if the device is placed on a table or in a pocket, it may be mistakenly identified as "being worn" and automatically turned on, ultimately causing unnecessary power consumption. Utility Model Content

[0004] To overcome the above shortcomings, this utility model provides a skin detection optical sensor and wearable device.

[0005] The technical solution provided by this utility model is as follows: On the one hand, this utility model provides a skin detection optical sensor, including: A substrate with conductive lines is formed, and the surface has an emitter die-bonding region and a receiver die-bonding region. The emitter die-bonding area is provided with at least two emitter chips; the receiver die-bonding area is provided with a receiver chip; Lenses are formed above the emitter and receiver die-bonding areas on the substrate surface, respectively, corresponding to the emitter and receiver chips within the coverage area; An opaque package is disposed on the surface of a substrate in a region other than the emitter die-bonding region and the receiver die-bonding region, and the thickness of the opaque package is not less than the thickness of the lens.

[0006] More preferably, the substrate is square, with the emitter die-bonding area and the receiver die-bonding area located on opposite sides of the central axis of the long side.

[0007] More preferably, the emitter die-bonding region and the receiver die-bonding region are circular.

[0008] More preferably, the lens includes a planar segment and a hemispherical lens with a protrusion on the surface of the planar segment along the thickness direction.

[0009] More preferably, on the surface of the planar segment, the opaque package extends laterally by a predetermined width into the emitter die-bonding area and the receiver die-bonding area.

[0010] More preferably, the minimum size of the skin detection optical sensor is 3.0mm × 1.6mm × 1.0mm.

[0011] More preferably, the at least two emitting chips include emitting chips with emission wavelengths of 1050nm and 1450nm, respectively.

[0012] On the other hand, this invention also provides a wearable device, including the aforementioned skin detection optical sensor.

[0013] This invention provides a skin detection optical sensor and wearable device. Structurally, it integrates two emitting chips and one receiving chip into a single packaged device, encapsulated with a hemispherical lens to enhance the strength of both emitted and received signals. Simultaneously, an opaque package horizontally isolates the emitting and receiving chips, facilitating sensor miniaturization. In terms of detection, it utilizes the difference in skin reflection intensity between the 1050nm and 1450nm wavelength emitting chips to process and calculate the reflected signals received by the receiving chip, accurately identifying whether the reflecting object is skin. Attached Figure Description

[0014] Figure 1 This is a top view schematic diagram of a skin detection optical sensor in one embodiment of the present invention; Figure 2 for Figure 1 The diagram shows a cross-sectional view of the skin detection optical sensor along line AA. Figure 3 The curves showing the output current ratio of the optical sensor for skin detection as a function of distance are shown for both skin and gray card.

[0015] Figure label: 1 / 2 - Transmitter chip, 3 - Receiver chip, 4 - Lens, 5 - Opaque package, 10 - Substrate, 11 - Transmitter die bonding area, 12 - Receiver die bonding area. Detailed Implementation

[0016] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the specific embodiments of this utility model will be described below with reference to the accompanying drawings. Obviously, the accompanying drawings described below are merely some embodiments of this utility model. For those skilled in the art, other drawings and other embodiments can be obtained based on these drawings without creative effort. Furthermore, in this application, directional terms such as "front," "rear," "upper," "lower," "left," and "right" are defined relative to the indicated placement of the components in the drawings. It should be understood that these directional terms are relative concepts, used for relative description and clarification, and can change accordingly depending on the placement of the components in the drawings.

[0017] One embodiment of this utility model discloses a skin detection optical sensor, comprising: a substrate with conductive lines formed thereon, having an emission bonding region and a receiving bonding region on its surface; at least two emission chips are disposed in the emission bonding region; a receiving chip is disposed in the receiving bonding region; a lens is formed above the emission bonding region and the receiving bonding region on the surface of the substrate, respectively, corresponding to the emission chip and the receiving chip in the respective coverage area; and an opaque package is disposed on the surface of the substrate excluding the emission bonding region and the receiving bonding region, the thickness of the opaque package being not less than the thickness of the lens.

[0018] The substrate is flat, providing physical support for other structures within the sensor while also providing circuit support for the transmitting and receiving chips via conductive lines. Materials can include PCB, BT, FR4, and copper. Its shape can be designed according to the available space in the wearable device; for example, it can be square, circular, elliptical, polygonal, or even irregular in shape. The substrate thickness is also rigorously calculated and optimized to minimize thickness while ensuring mechanical strength, thus meeting the requirements for thinner and lighter wearable devices.

[0019] The emitter and receiver die-bonding areas are located on the same side surface (i.e., the top surface) of the substrate. These areas are used to mount the emitter chip and receiver chip, respectively. To prevent interference with the receiver chip, a specific distance is designed between the emitter and receiver die-bonding areas, ensuring they do not contact each other. This distance is the optimal value obtained through extensive optical simulations and experimental verification, taking into account the emitter chip's emission angle, emission intensity, receiver chip's receiving range, and the attenuation characteristics of light propagation.

[0020] The sensor's detection principle is as follows: when light emitted by the transmitting chip shines on a reflecting object, some of the light is absorbed, and the remaining light is reflected off the surface of the reflecting object before propagating to the receiving chip and being received. The receiving chip converts the received light signal into a corresponding electrical signal. These electrical signals are then transmitted to an external signal processing module through conductive lines on the substrate. The signal processing module amplifies, filters, and performs analog-to-digital conversion on the two wavelength electrical signals, calculates the ratio of the two signals, and compares it with a preset skin recognition threshold to determine whether the detected object is skin. Generally, if the electrical signal amplitude exceeds the set threshold, it is determined to be in a wearing state; otherwise, if the reflected light signal is weak, it is determined to be in a non-wearing state, thus achieving the purpose of skin detection. To avoid interference from other light sources, especially from the transmitting chip, in addition to designing a certain distance between the transmitting and receiving die-bonded areas to prevent them from contacting each other, an opaque package is also needed to isolate the two areas.

[0021] To minimize the sensor's size and space requirements, this embodiment encapsulates lenses in both the emitter and receiver die-bonding areas, ensuring their independence. In the emitter die-bonding area, the emitting chip can be an LED or a VCSEL, as long as it emits light of a specified wavelength. A single lens covers all the internal emitting chips, focusing the divergent light emitted into a directional beam, reducing light diffusion loss and ensuring more light reaches the skin detection area. Similarly, the lens in the receiver die-bonding area covers the internal receiver chip, converging the divergent light reflected from the skin onto the photosensitive surface of the receiver chip, improving light signal acquisition efficiency. The lens is made of highly transparent resin or silicone material. Along the height direction, a planar segment of a certain thickness can be included at the bottom of the hemispherical lens. The size of this planar segment is larger than the hemispherical lens. The overall size and height of the lens must be precisely calculated based on the chip's emission angle, photosensitive angle, and detection distance to ensure the final signal strength of the emitting and receiver chips meets the detection requirements.

[0022] The substrate surface, excluding the circular emitter and receiver die-bonding areas, including the areas surrounding the emitter and receiver die-bonding areas and the areas between them, is equipped with an opaque encapsulation. This encapsulation can be made of black light-shielding resin or silicone, such as BT, PP, PC, or PET, as long as it can isolate light. This serves to prevent lateral light emission from the emitter chip and absorb stray light, preventing interference with detection performance. The opaque encapsulation can extend a certain width into the emitter and receiver die-bonding areas on the planar surface of the lens. This design makes the sensor structure more stable. It should be noted that the opaque encapsulation does not touch the hemispherical lens, especially not covering it. To ensure isolation of lateral light emission from the emitter chip, the thickness of the opaque encapsulation is not less than the thickness of the hemispherical lens, and can be consistent with the highest point of the hemispherical lens or slightly exceed its height.

[0023] The following example will illustrate this in detail: like Figure 1 and Figure 2 As shown, the skin detection optical sensor uses a square substrate 10 with a long side of 3mm and a short side of 1.6mm. The emitter bonding area 11 and the receiver bonding area 12 are circular, located on opposite sides of the central axis of the long side, with their centers located on the central axis of the short side, and arranged symmetrically along the central axis of the short side; however, their sizes are different, with the diameter of the emitter bonding area 11 being smaller than that of the receiver bonding area 12. A combination of a 1050nm emitter chip 1 and a 1450nm emitter chip 2 is arranged side by side on the surface of the emitter bonding area. The receiver chip 3 in the receiver bonding area is an InGaAs photodiode. The emitter bonding area and the receiver bonding area contain positive and negative electrode pads. One electrode of the emitter / receiver chip is bonded to the surface of one of the pads, and the other electrode is connected to the pad of the opposite polarity via a bonding wire.

[0024] In actual detection, these two wavelength signals are emitted alternately, and the photodiode receives these two reflected signals respectively. By calculating the ratio of the two reflected signals, a skin recognition threshold can be defined, thus achieving the purpose of skin detection. Based on the reflected photocurrent (1050nm) / photocurrent (1450nm) value, it can be determined whether it is skin; for example... Figure 3As shown, the red curve represents the change in the reflected photocurrent (1050nm) / photocurrent (1450nm) value with the wearing distance (i.e., the distance between the sensor and the reflecting object) when the reflecting object is skin. Under normal wearing conditions (e.g., the distance between the sensor and the reflecting object is greater than 0 and less than 4mm), the ratio is greater than 4. The blue curve represents the change in the reflected photocurrent (1050nm) / photocurrent (1450nm) value with the wearing distance (i.e., the distance between the sensor and the reflecting object) when the reflecting object is a gray card used for photometry. Under normal wearing conditions, the ratio is less than 4. Therefore, in this embodiment, the sensor threshold is 4. When the calculated photocurrent (1050nm) / photocurrent (1450nm) value received by the sensor is greater than 4, it can be determined that the sensor is in the wearing state.

[0025] The lens 4, comprising the emitter / receiver bonding area and the receiver / receiver bonding area, includes a planar segment of a certain thickness and a hemispherical lens protruding from the surface of the planar segment. The thickness of the planar segment exceeds the thickness of the emitter / receiver chip, and the size of the planar segment is larger than that of the hemispherical lens. Therefore, an annular horizontal step is formed between the planar segment and the hemispherical lens. The opaque package 5 covers the area of ​​the substrate surface excluding the circular emitter / receiver bonding area. It extends a certain width (i.e., covering part of the horizontal step) into the circular emitter / receiver bonding area from the surface of the planar segment of the lens, near the emitter / receiver bonding area. The extended width only covers part of the planar segment at the bottom of the hemispherical lens, without touching the hemispherical lens itself. The upper surface of the opaque package is flush with the highest point of the hemispherical lens. The overall dimensions of the sensor are 3.0 mm × 1.6 mm × 1.0 mm.

[0026] In the fabrication process of this skin detection optical sensor, the transmitting chip and the receiving chip are first die-bonded onto the substrate surface and wire bonded. Then, lenses are fabricated by molding transparent resin onto the transmitting and receiving die-bonded areas on the substrate surface, and a first cut is performed to remove the resin connecting strips between adjacent unit lenses and the excess transparent resin covering non-die-bonded areas (such as substrate edges and unit spacing areas). Next, an opaque encapsulation is fabricated on the substrate surface, which can be fabricated by molding with black resin or by directly bonding a pre-prepared black plastic frame to the substrate. Finally, the entire substrate is cut into individual pieces to obtain a single skin detection optical sensor.

[0027] In another embodiment of this utility model, a wearable device includes the aforementioned skin detection optical sensor. After the skin detection optical sensor is installed in a suitable position, the sensor's detection results can be used to determine whether the wearable device is in a wearing state or a removed state. This allows for better on / off activation or deactivation of various system functions within the wearable device, saving unnecessary energy loss. Furthermore, the emitter bonding region in the skin detection optical sensor can also employ other suitable emitter chips to simultaneously realize other functions of the wearable device; this embodiment does not impose any limitations on this.

[0028] It should be noted that the above embodiments can be freely combined as needed. The above are merely preferred embodiments of this utility model. It should be pointed out that for those skilled in the art, several improvements and modifications can be made without departing from the principle of this utility model, and these improvements and modifications should also be considered within the protection scope of this utility model.

Claims

1. A skin detection optical sensor, characterized in that, include: A substrate with conductive lines is formed, and the surface has an emitter die-bonding region and a receiver die-bonding region. The emitter die-bonding area is provided with at least two emitter chips; the receiver die-bonding area is provided with a receiver chip; Lenses are formed above the emitter and receiver die-bonding areas on the substrate surface, respectively, corresponding to the emitter and receiver chips within the coverage area; An opaque package is disposed on the surface of a substrate in a region other than the emitter die-bonding region and the receiver die-bonding region, and the thickness of the opaque package is not less than the thickness of the lens.

2. The skin detection optical sensor as described in claim 1, characterized in that, The substrate is square, with the emitter die-bonding area and the receiver die-bonding area located on both sides of the central axis of the long side.

3. The skin detection optical sensor as described in claim 1, characterized in that, The emitter die-bonding region and the receiver die-bonding region are circular.

4. The skin detection optical sensor as described in claim 1, characterized in that, The lens, along its thickness direction, includes a planar segment and a hemispherical lens with a protrusion on the surface of the planar segment.

5. The skin detection optical sensor as described in claim 4, characterized in that, On the surface of the planar segment, the opaque package extends laterally with a predetermined width into the emitter die-bonding area and the receiver die-bonding area.

6. The skin detection optical sensor as described in claim 1, characterized in that, The minimum size of the skin detection optical sensor is 3.0mm × 1.6mm × 1.0mm.

7. The skin detection optical sensor as described in any one of claims 1-6, characterized in that, The at least two emitting chips include emitting chips with emission wavelengths of 1050nm and 1450nm, respectively.

8. A wearable device, characterized in that, Including the skin detection optical sensor as described in any one of claims 1-7.

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