Patent ID: 12196584

DETAILED DESCRIPTION OF THE EMBODIMENT

It should be noted that, wherever possible, the same reference numbers will be used throughout the drawings to refer to the same or like parts.

The optical encoder of the present disclosure is adaptable to a reflective type optical encoder having multiple tracks for balancing reflective light intensity from different tracks. Furthermore, a light source and a light sensor of the present disclosure are arranged at different surfaces of a substrate to prevent interfering to reflective light from emission light of the light source. The optical encoder of the present disclosure can reduce assembling complexity and has lower interference to the chip due to heating of the light source in operation.

Please referring toFIG.2, it is a cross sectional view of an optical encoder200according to a first embodiment of the present disclosure. The optical encoder200includes an encoding medium22and a sensing device arranged opposite to each other. The encoding medium22is, for example, a code disk or a code strip that rotates or linearly moves with respect to the sensing device depending on different applications.

The encoding medium22includes a first track A and a second track B. For example, the first track A is a position track for generating reflective light to determine a current position or angle of the encoding medium22. For example, the second track B is an index track for determining an absolute position or angle of the encoding medium22, e.g., an original position or 0 degree. The first track A and the second track B are located at different tracks of the encoding medium22. For example, when the encoding medium22is a code disk, the first track A and the second track B are located at different radial positions. In the present disclosure, a number of and a shape of slits or reflective stripes included in the first track A and the second track B are not particularly limited.

InFIG.2, the sensing device is referred to a package or a chip under the encoding medium22. The sensing device includes a substrate215, a light source111and a front side illuminated (FSI) sensor213, e.g., CMOS image sensor. In some aspects, the sensing device further includes a filter219arranged on the substrate215(e.g.,FIG.2showing the filter219being attached to the substrate215at the edge thereof) to block light outside an emission spectrum of the light source111and to protect components in the sensing device.

The substrate215is selected from a printed circuit board (PCB), a ceramic substrate or a flexible board without particular limitations. The substrate215has a first surface (e.g., an upper surface inFIG.2) and a second surface (e.g., a lower surface inFIG.2) opposite to each other, wherein the first surface faces the encoding medium22. The substrate215further includes a first opening and a second opening for the reflective light from the first track A and the second track B to pass through. The shapes of the first opening and the second opening are not particularly limited.

The light source211is, for example, a light emitting diode for emitting light of an identifiable spectrum, e.g., red light and/or infrared light. The light source211is arranged at the first surface of the substrate215, and located between the first track A and the second track B. Preferably, the first track A and the second track B are within an emission angle of the light source211. In this way, the light source211illuminates both the first track A and the second track B. Preferably, the light source211is located at a center position between (in the transverse direction) the first track A and the second track B so as to uniformly illuminate the first track A and the second track B, but the present disclosure is not limited thereto. In the scenario that the emission angle of the light source211has special configuration, the light source211is not located at a center between the first track A and the second track B but located at a position that causes the first track A and the second track B to be uniformly illuminated.

An active region (or called light sensing region)213sof the FSI sensor213is located at a side close to the substrate215, and the FSI sensor213is attached to the second surface of the substrate215via conductive bumps217. The method of combining a sensor to a substrate using conductive bumps is known to the art, and thus details thereof are not described herein. In order not to degrade the operation of the active region213s, the conductive bumps217are arranged outside the active region231s.

The FSI sensor213is arranged at the second surface of the substrate215, and has a first light sensing region (e.g., left part of active region inFIG.2) and a second light sensing region (e.g., right part of active region inFIG.2), each having at least one photodiode, respectively for detecting reflective light LAfrom the first track A and reflective light LBfrom the second track B. In one aspect, the FSI213has a single light sensing region213s(e.g., shown as dashed block), and because a part of the single light sensing region213sis blocked by the substrate215, a first light sensing region and a second light sensing region is divided during operation. Meanwhile, the first opening and the second opening of the substrate215are respectively aligned with the first light sensing region and the second light sensing region of the FSI sensor211to allow the reflective light LAand LBrespectively from the first track A and the second track B to pass through.

In one aspect, the optical encoder200further includes a processor (e.g., MCU or ASIC) to respectively identify the intensity variation detected by the first light sensing region and the second light sensing region to identify the position signal and the index signal generated thereby.

As shown inFIG.2, as the light source211fairly illuminates the first track A and the second track B, the intensity difference between the reflective light LAand LBis eliminated such that it is not required to consider the interference caused by the intensity difference in regulating the emission light intensity of the light source211.

Please referring toFIG.3, it is a cross sectional view of an optical encoder300according to a second embodiment of the present disclosure. The optical encoder300also includes an encoding medium32and a sensing device arranged opposite to each other. The encoding medium32also includes a first track A and a second track B, and the first track A and the second track B are located at different tracks of the encoding medium32. The difference between the optical encoder300and the optical encoder200of the first embodiment is that the FSI sensor213is replaced by a backside illuminated (BSI) sensor313, e.g., CMOS image sensor, but other components are identical to the first embodiment.

An active region (e.g., shown by dashed block)313sof the BSI sensor313is located at a side far from the substrate315. The reflective light LAand L B from the first track A and the second track B penetrate into a light sensing region (i.e. the active region)313sfrom a back side of the BSI sensor313. The BSI sensor313is attached to the second surface of the substrate315via bonding wires317. The method of combining a light sensor to a substrate using bonding wires is known to the art, and thus details thereof are not described herein.

Similarly, in this embodiment, a part of the light sensing region313sis blocked by the substrate315such that the reflective light LAand LBpropagates to a first light sensing region (e.g., left part of active region313s) and a second light sensing region (e.g., right part of active region313s) of the BSI sensor313via a first opening and a second opening of the substrate315.

In one aspect, the optical encoder300includes a processor to respectively identify the intensity variation detected by the first light sensing region and the second light sensing region of the BSI sensor313to identify the position signal and the index signal generated thereby. The method of identifying an angle of the encoding medium32by a processor according to the position signal (associated with reflective light LA) and the index signal (associated with reflective light LB) is known to the art and not a main objective of the present disclosure, and thus details thereof are not described herein.

The optical encoder300also includes a filter319for the purpose of light filtering and structure sealing.

Similarly, in the second embodiment ofFIG.3, as the light source311uniformly illuminates the first track A and the second track B, the intensity difference between reflective light LAand LBis effectively eliminated.

Please referring toFIG.4, it is a cross sectional view of an optical encoder400according to a third embodiment of the present disclosure. The optical encoder400also includes an encoding medium42and a sensing device arranged opposite to each other. The encoding medium42also includes a first track A and a second track B located at different tracks of the encoding medium32. The encoding medium42of the third embodiment is identical to the encoding mediums22and32in the above first and second embodiments and thus details thereof are not repeated herein.

The sensing device includes a substrate415, a first light source411A, a second light source411B and a light sensor413. The substrate415is also selected from a PCB, a ceramic substrate or a flexible board that has a first surface (e.g., an upper surface inFIG.4) and a second surface (e.g., a lower surface inFIG.4) opposite to each other, wherein the first surface faces the encoding medium42.

The first light source411A and the second light source411B are, for example, light emitting diodes, and are used to emit light of an identifiable spectrum, e.g., red light and/or infrared light. The first light source411A and the second light source411B are arranged at the first surface of the substrate415, and emit light respectively toward the first track A and the second track B, wherein the first track A and the second track B are located between (e.g., in a transverse direction ofFIG.4) the first light source411A and the second light source411B. Preferably, the first track A is located within an emission angle of the first light source411A, and the second track B is located with an emission angle of the second light source411B. Preferably, the first track A and the second track B are symmetrically arranged between the first light source411A and the second light source411B. For example, a central line between the first track A and the second track B has the same distance D from the first light source411A and the second light source411B.

InFIG.4, the light sensor413is shown as the FSI sensor whose active region (or called light sensing region)413sis located at a side close to the substrate415, and the light sensor413is attached to the second surface of the substrate415using conductive bumps417, but the present disclosure is not limited thereto. In another aspect, the light sensor413is a BSI sensor, similar to that shown inFIG.3, and said BSI sensor is attached to the second surface of the substrate415using bonding wires.

In the third embodiment, the substrate415has an opening aligned with the first track A and the second track B as well as the light sensing region413sof the light sensor413such that reflective light from the first track A and the second track B can propagate to the light sensing region413svia the opening. The first light source411A and the second light source411B are preferably arranged at two opposite sides of the opening.

In some aspects, the optical encoder400further includes a filter419configured for the purpose of light filtering and structure sealing.

Similarly, in the third embodiment ofFIG.4, because the first light source411A and the second light source411B uniformly illuminate the first track A and the second track B, the intensity difference between reflective light is effectively eliminated. Preferably, the emission intensity of the first light source411A and the second light source411B are substantially identical.

As mentioned above, the optical encoder of the present disclosure includes an encoding medium a substrate, a light source and a light sensor. The substrate includes a through hole, a first surface and a second surface opposite to the first surface. The light source is arranged at the first surface of the substrate. The light sensor is arranged at the second surface of the substrate, and has a first light sensing region and a second light sensing region for receiving light passing through the through hole. The light source of the present disclosure is an FSI sensor or a BSI sensor according to different applications.

It should be mentioned that although the above embodiments of the present disclosure show that the light sensor has a single active region (e.g., shown by dashed block), the present disclosure is not limited thereto. In another aspect, the light sensor of the present disclosure includes two separated active regions respectively for receiving reflective light from different tracks.

As mentioned above, because different tracks in the conventional optical encoder have different transverse distances from a light source, the light intensity reflected from the different tracks and received by a light sensor is also different to make it difficult to determine a suitable emission light intensity of the light source when the emission light intensity of the light source needs to be regulated (e.g., due to distance deviation between the encoding medium and the light source in assembling). Accordingly, the present disclosure further provides an optical encoder (e.g.,FIGS.2-4) that can eliminate the intensity difference of reflective light of different tracks by arranging the light source between said different tracks to balance the reflective light intensity. Furthermore, by arranging the light source and the light sensor at different sides of a substrate, the thermal effect of the light source to the light sensor during operation is prevented and the assembling complexity is reduced. Meanwhile, an additional light blocking wall is no longer necessary between the light source and the light sensor.

Although the disclosure has been explained in relation to its preferred embodiment, it is not used to limit the disclosure. It is to be understood that many other possible modifications and variations can be made by those skilled in the art without departing from the spirit and scope of the disclosure as hereinafter claimed.