Optical isolation apparatus

Abstract

The present invention discloses an apparatus comprising: an optical emitter (104) mounted to a substrate (202); a transparent emitter housing portion (204) enclosing the optical emitter; a sensor (106) for detecting light, the sensor being mounted to the substrate; and a transparent sensor housing portion (206) enclosing the sensor; wherein the transparent emitter housing portion and the transparent sensor housing portion are horizontally separated on the substrate by an air gap.

Description

[Technical Field] The present invention relates to providing optical isolation between an optical transmitter and a photosensor. [Previous Technology] Mobile phones and other portable computing devices typically include sensors to determine when an object is near the device. For example, many mobile phones use infrared proximity sensors to determine when a user holds the phone close to their head to make a call, allowing the screen to be turned off to save power and the touchscreen to be disabled. A proximity sensor module, for example, uses a transmitter to bounce light off a nearby object and a sensor to detect the reflected light. Mobile phone proximity sensors are very small modules, and the transmitter is typically placed quite close to the sensor. If the transmitter signal is not attenuated or optically isolated from the sensor, the light emitted by the transmitter may blind the sensor. Figure 1 illustrates a known proximity sensor module 102. The proximity sensor module 102 includes an optical emitter 104 configured to emit light. The proximity sensor module 102 additionally includes a sensor 106 for detecting light reflected from an object 100. The proximity sensor module 102 includes an opaque optical barrier 108 positioned between the optical emitter 104 and the optical sensor 106 to optically isolate the optical emitter 104 from the sensor 106. [Summary of the Invention] The inventors have determined that the known method of optically isolating an optical emitter from a sensor by adding an opaque optical barrier between the two devices complicates the manufacturing process and requires additional materials to produce the device. According to one aspect of the present invention, an apparatus (e.g., in the form of an optical sensor module) is provided, the apparatus comprising: an optical emitter mounted to a substrate; a transparent emitter housing portion enclosing the optical emitter; a sensor for detecting light, the sensor being mounted to the substrate; and a transparent sensor housing portion enclosing the sensor; wherein the transparent emitter housing portion and the transparent sensor housing portion are horizontally separated on the substrate by an air gap. By avoiding the need for an opaque optical barrier between the optical transmitter and the sensor, the manufacturing process is simplified and the amount of material required to produce the optical sensor module is reduced, while ensuring optical isolation between the optical transmitter and the optical sensor. In some embodiments, the transparent emitter housing portion includes a sidewall adjacent to the air gap that extends perpendicular to the substrate, and the transparent sensor housing portion includes a sidewall adjacent to the air gap that extends perpendicular to the substrate. The inventors have determined that by introducing a ramp to the opposite sidewall of the transparent emitter housing and / or the transparent sensor housing adjacent to the air gap, the horizontal separation distance between the transparent emitter housing and the transparent sensor housing can be reduced. This advantageously enables a reduction in the size of the optical sensor module. That is, the transparent emitter housing portion may include one of the sloping sidewalls adjacent to the air gap. Additionally or alternatively, the transparent sensor housing portion may include one of the sloping sidewalls adjacent to the air gap. To optimize optical isolation and simplify the manufacturing process, the inclined sidewalls of the transparent emitter housing may be at an angle of 45 degrees or less, preferably 30 degrees or less, more preferably 15 degrees or less, and even more preferably 10 degrees or less, relative to a vertical axis. Similarly, the inclined sidewalls of the transparent sensor housing may be at an angle of 45 degrees or less, preferably 30 degrees or less, relative to a vertical axis. In some embodiments, the sloping sidewalls of the transparent emitter housing portion are coupled to one edge of the substrate. In other embodiments, the sloping sidewalls of the transparent emitter housing portion are coupled to one edge of the transparent sensor housing portion. In other embodiments, the sloping sidewalls of the transparent emitter housing portion are coupled to one edge of a transparent intermediate housing portion that connects the transparent emitter housing portion and the transparent sensor housing portion. Advantageously, the horizontal separation distance between the transparent emitter housing and the transparent sensor housing is minimized, thereby minimizing the size of the optical sensor module. However, the inventors have determined that if the horizontal separation distance between the transparent emitter housing and the transparent sensor housing is reduced too much, light emitted by the optical emitter may leave the transparent emitter housing portion and hit the transparent sensor housing portion, thereby causing it to be reflected back into the transparent sensor housing portion and incident on the sensor. To address this problem, the inventors have determined that adding a chamfer to the sidewalls on one or both sides of the air gap improves optical isolation, thereby maintaining a smaller horizontal separation distance between the transparent emitter housing and the transparent sensor housing. Therefore, in an embodiment where the transparent emitter housing portion includes an inclined sidewall adjacent to the air gap, the transparent emitter housing portion may include a further inclined sidewall adjacent to the air gap, the further inclined sidewall extending from the inclined sidewall of the transparent emitter housing portion to an upper surface of the transparent emitter housing portion. The further inclined sidewall of the transparent emitter housing portion may form an angle relative to the vertical axis, the angle being greater than the angle of the inclined sidewall of the transparent emitter housing portion relative to the vertical axis. Specifically, the further inclined sidewall of the transparent emitter housing portion may form an angle relative to the vertical axis in the range of 30 degrees to 60 degrees. Furthermore, in an embodiment where the transparent sensor housing portion includes a sloping sidewall adjacent to the air gap, the transparent sensor housing portion may include a further sloping sidewall adjacent to the air gap, the further sloping sidewall extending from the sloping sidewall of the transparent sensor housing portion to an upper surface of the transparent sensor housing portion. The further sloping sidewall of the transparent sensor housing portion may form an angle relative to the vertical axis, the angle being greater than the angle of the sloping sidewall of the transparent sensor housing portion relative to the vertical axis. Specifically, the further sloping sidewall of the transparent sensor housing portion may form an angle relative to the vertical axis in the range of 30 degrees to 60 degrees. In some implementations, the horizontal separation distance between the optical transmitter and the sensor is in the range of 1.5 mm to 3 mm, preferably in the range of 2 mm to 3 mm. The optical emitter can be a laser diode, such as a vertical-cavity surface-emitting laser. The sensor can be a photodiode. According to another aspect of the present invention, an action computing device including the means described herein is provided. These and other variations will become apparent from the embodiments described below. The scope of the invention is not intended to be limited by this [Summary], nor is it limited to embodiments that necessarily address any or all of the disadvantages pointed out.

Implementation Method

Claims

1. An optical isolation device, comprising: An optical transmitter (104) is mounted to a substrate (202); A transparent emitter housing portion (204) enclosing the optical emitter; a sensor (106) for detecting light, the sensor being mounted to the substrate; a transparent sensor housing portion (206) enclosing the sensor; wherein the transparent emitter housing portion and the transparent sensor housing portion are horizontally separated on the substrate by an air gap; wherein the transparent emitter housing portion includes an inclined sidewall (302) adjacent to the air gap; wherein the inclined sidewall of the transparent emitter housing portion is at an angle of 45 degrees or less relative to a vertical axis; wherein the transparent emitter housing portion includes a further inclined sidewall (402) adjacent to the air gap, the further inclined sidewall (402) extending from the inclined sidewall of the transparent emitter housing portion to an upper surface of the transparent emitter housing portion; The further inclined sidewall of the transparent emitter housing portion forms an angle relative to the vertical axis, the angle being greater than the angle of the further inclined sidewall of the transparent emitter housing portion relative to the vertical axis; and the further inclined sidewall of the transparent emitter housing portion forms an angle relative to the vertical axis in the range of 30 degrees to 60 degrees, wherein a horizontal separation distance between the optical emitter and the sensor is in the range of 1.5 mm to 3 mm, wherein the further inclined sidewall of the transparent emitter housing portion has a vertical height, the vertical height being measured between: (i) a lower edge of the further inclined sidewall coupled to the inclined sidewall; and (ii) an upper edge of the further inclined sidewall coupled to the upper surface of the transparent emitter housing portion, and the vertical height being approximately 0.15 mm or less.

2. The apparatus of claim 1, wherein the inclined sidewall of the transparent emitter housing portion has coupling to one edge of the substrate.

3. The apparatus of claim 1, wherein the inclined sidewall of the transparent emitter housing portion has an edge coupled to one edge of the transparent sensor housing portion.

4. The apparatus of claim 1, wherein the inclined sidewall of the transparent emitter housing portion has an edge coupled to a transparent intermediate housing portion, the transparent intermediate housing portion connecting the transparent emitter housing portion and the transparent sensor housing portion.

5. The device of claim 1, wherein the transparent sensor housing portion includes an inclined sidewall (304) adjacent to the air gap.

6. The device of claim 5, wherein the inclined sidewall of the transparent sensor housing portion is at an angle of 45 degrees or less relative to a vertical axis.

7. The apparatus of claim 5 or 6, wherein the transparent sensor housing portion includes a further inclined sidewall (404) adjacent to one of the air gaps, the further inclined sidewall (404) extending from the inclined sidewall of the transparent sensor housing portion to one of the upper surfaces of the transparent sensor housing portion.

8. The apparatus of claim 6, wherein the further inclined sidewall of the transparent sensor housing portion forms an angle relative to the vertical axis, the angle being greater than the angle of the inclined sidewall of the transparent sensor housing portion relative to the vertical axis.

9. The device of claim 6, wherein the further inclined sidewall of the transparent sensor housing portion forms an angle with respect to the vertical axis in the range of 30 to 60 degrees.

10. The apparatus of claim 1, wherein the transparent emitter housing portion includes a sidewall (208) adjacent to the air gap extending perpendicularly to the substrate, and the transparent sensor housing portion includes a sidewall (210) adjacent to the air gap extending perpendicularly to the substrate.

11. The apparatus of claim 1, wherein no opaque barrier is provided in the air gap to optically isolate light emitted from the optical emitter and incident on the sensor.

12. The apparatus of claim 1, wherein the optical transmitter is a laser diode.

13. The apparatus of claim 1, wherein the sensor is a photodiode.

14. An action computing device (602) comprising the means as claimed in claim 1.

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