Abstract:
An optical encoder including a leadframe substrate, an emitter, and a detector is disclosed. The leadframe substrate bent to include a base portion, an emitter portion and a detector portion. The emitter, for emitting light, is mounted on the emitter portion. The detector, for detecting light, is mounted on the detector portion. The emitter portion lies at an emitter angle relative to the base portion such that light emitted by the emitter is generally directed at a desired direction. The detector portion lies at a detector angle relative to the base portion such that reflected light is captured by the detector. Due to the angles at which the emitter and the detector are mounted, lenses are not necessary; however, even if lenses are used, the encoder is more robust towards manufacturing tolerances of the lenses.

Description:
BACKGROUND  
       [0001]     The present invention relates generally to optical encoders. More particularly, the present invention relates to optical encoders having various die orientations.  
         [0002]     Optical encoders detect motion and typically provide closed-loop feedback to a motor control system. When operated in conjunction with a code scale, an optical encoder detects motion (linear or rotary motion of the code scale), converting the detected motion into digital signal that encode the movement, position, or velocity of the code scale. Here, the phrase “code scale” includes code wheels and code strips.  
         [0003]     Usually, motion of the code scale is detected optically by means of an optical emitter and an optical detector. The optical emitter emits light impinging on and reflecting from the code scale. A typical code scale includes a regular pattern of slots and bars that reflect light in a known pattern. Light is either reflected or not reflected from the code scale. The reflected light is detected by the optical detector. As the code scale moves, an alternating pattern of light and dark corresponding to the pattern of the bars and spaces reaches the optical detector. The optical detector detects these patterns and produces electrical signals corresponding to the detected light, the electrical signals having corresponding patterns. The electrical signal, including the patterns, can be used to provide information about position, velocity and acceleration of the code scale.  
         [0004]      FIG. 1A  illustrates a cross sectional side view schematic of a known optical encoder  100  and a code scale  120 .  FIG. 1B  is the code scale  120  as viewed from the optical encoder  100 .  FIGS. 1A and 1B  include orientation axes legend for even more clarity.  
         [0005]     Referring to  FIGS. 1A and 1B , the encoder  100  includes an optical emitter  102  and an optical detector  104  mounted on a substrate  106  such as a lead frame  106 . The optical emitter  102  and the optical detector  104  as well portions of the lead frame  106  are encapsulated in an encapsulant  108  including, for example, clear epoxy. The encapsulant  108  defines a first dome-shaped surface  110  (first lens  110 ) over the optical emitter  102  and a second dome-shaped surface  112  (second lens  112 ) over the optical detector  104 .  
         [0006]     The optical emitter  102  emits light  114  that leaves the encapsulant  108  via the first lens  110 . The first lens  110  concentrates or directs the emitted light  114  toward the code scale  120 , the light reflecting off of the code scale  120 . The reflected light  116  reaches the optical detector  104  via the second lens  112 . The second lens  112  concentrates or directs the reflected light toward the optical detector  104 . The optical detector  104  can be, for example only, photo detector that converts light into electrical signals.  
         [0007]     The shape and the size of the first lens  110  and the second lens  112  are dictated by various factors such as, for example only: the distance of the code scale  102  from the lenses  110  and  112  and the characteristics of the emitter  102  and the detector  104 . Often, space  118  between the lenses  110  and  112  is filled with the same encapsulant  108  material and has a flat surface  117 .  
         [0008]     There exists an ever increasing demand for increasing performance, which, in turn, requires smaller packaging, higher resolution, and tighter tolerances. Using the prior art configuration, it is difficult to achieve higher performances because, for example, the performance of the encoders are sensitive to the size and the shape of the lenses; however, it is difficult to consistently produce the desired size and the desired shape of the lenses  110  and  112  using current molding techniques. Furthermore, the lenses require a separation distance  130  between the location of emitter and the detector and the code scale  120 . This is to accommodate the bulk of the lenses  110  and  112  as well as for focal distance between the emitter-detector pair and the code scale  120 , the focal distance determined by the lenses  110  and  112 .  
         [0009]     Accordingly, there remains a need for improved optical encoder that alleviates or overcomes these shortcomings.  
       SUMMARY  
       [0010]     The need is met by the present invention. In a first embodiment of the present invention, optical encoder includes a leadframe substrate, an emitter, and a detector. The leadframe substrate includes a base portion, an emitter portion and a detector portion. The emitter is operable to emit light. The emitter is mounted on the emitter portion of the leadframe substrate. The detector is operable to detect light. The detector is mounted on the detector portion of the leadframe substrate. The emitter portion of the leadframe substrate lies at an emitter angle relative to the base portion such that light emitted by the emitter is generally directed at a desired direction.  
         [0011]     The detector portion of the leadframe substrate lies at a detector angle relative to the base portion such that light reflected from a code scale is generally directed toward the detector. In fact, the emitter angle and the detector angle have same absolute value.  
         [0012]     The emitter and the detector are encapsulated by encapsulant. The encapsulant can be formed to define an emitter lens adapted to direct light from the emitter toward a desired direction. Further, the encapsulant can be formed to define a detector lens adapted to direct reflected light toward the detector.  
         [0013]     In a second embodiment of the present invention, an optical encoder includes a substrate defining a cavity having surfaces. An emitter, operable to emit light, is mounted on a first surface of the cavity. A detector, operable to detect light, is mounted on a second surface of the cavity.  
         [0014]     The substrate can be, for example, can be a leadframe substrate or a silicon substrate, depending on desired implementation. The emitter is positioned such that emitted light is generally directed up and toward the center of the cavity. The detector is positioned generally facing up and center of the cavity.  
         [0015]     In a third embodiment of the present invention, a method of manufacturing an apparatus is disclosed. First, a leadframe substrate is provided. An emitter is mounted on the leadframe substrate. A detector is mounted on the leadframe substrate. The leadframe is bent such that a base portion and an emitter portion are formed, the emitter portion resulting at an emitter angle relative to the base portion.  
         [0016]     When the substrate is bent, a detector portion is also formed, the detector portion resulting at a detector angle relative to the base portion. The emitter angle and the detector angle can have the same absolute value. The emitter and the detector is encapsulated using clear encapsulant.  
         [0017]     In a fourth embodiment of the present invention, a method of manufacturing an apparatus is disclosed. A substrate is provided. A cavity is fabricated in the substrate, the cavity defining surfaces. An emitter is mounted on a first surface of the cavity. A detector is mounted on a second surface of the cavity.  
         [0018]     The emitter is positioned such that emitted light is generally directed up and toward the center of the cavity. The detector is positioned generally facing up and center of the cavity.  
         [0019]     Other aspects and advantages of the present invention will become apparent from the following detailed description, taken in conjunction with the accompanying drawings, illustrating by way of example the principles of the invention. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0020]      FIG. 1A  illustrates a cut away side view of a prior art optical encoder and a sample code scale;  
         [0021]      FIG. 1B  illustrates the sample code scale of  FIG. 1A  as viewed from the optical encoder of  FIG. 1A ;  
         [0022]      FIG. 2  illustrates an optical encoder in accordance with a first embodiment of the present invention;  
         [0023]      FIG. 3  illustrates an optical encoder in accordance with a second embodiment of the present invention;  
         [0024]      FIG. 4  illustrates an optical encoder in accordance with a third embodiment of the present invention;  
         [0025]      FIG. 5  illustrates an optical encoder in accordance with a fourth embodiment of the present invention;  
         [0026]      FIG. 6  is a flowchart illustrating another aspect of the present invention;  
         [0027]      FIGS. 7A and 7B  illustrate portions of the first embodiment of the present invention during various stages of manufacture; and  
         [0028]      FIG. 8  is a flowchart illustrating yet another aspect of the present invention. 
     
    
     DETAILED DESCRIPTION  
       [0029]     The present invention will now be described with reference to the Figures which illustrate various embodiments of the present invention. In the Figures, some sizes of structures or portions may be exaggerated and not to scale relative to sizes of other structures or portions for illustrative purposes and, thus, are provided to illustrate the general structures of the present invention. Furthermore, various aspects of the present invention are described with reference to a structure or a portion positioned “on” or “above” relative to other structures, portions, or both. Relative terms and phrases such as, for example, “on” or “above” are used herein to describe one structure&#39;s or portion&#39;s relationship to another structure or portion as illustrated in the Figures. It will be understood that such relative terms are intended to encompass different orientations of the device in addition to the orientation depicted in the Figures.  
         [0030]     For example, if the device in the Figures is turned over, rotated, or both, the structure or the portion described as “on” or “above” other structures or portions would now be oriented “below,” “under,” “left of,” “right of,” “in front of,” or “behind” the other structures or portions. References to a structure or a portion being formed “on” or “above” another structure or portion contemplate that additional structures or portions may intervene. References to a structure or a portion being formed on or above another structure or portion without an intervening structure or portion are described herein as being formed “directly on” or “directly above” the other structure or the other portion. Same reference number refers to the same elements throughout this document.  
         [0031]      FIG. 2  illustrates an optical encoder  200  in accordance with one embodiment of the present invention. Referring to  FIG. 2 , the optical encoder  200  includes a leadframe substrate  206  having a base portion  205 , an emitter portion  207 , and a detector portion  209 . An optical emitter  202  is operable to emit light. The emitter  202  is mounted on the emitter portion  207  of the substrate  206 . An optical detector  204  is mounted on the detector portion  209  of the leadframe substrate  206 . The detector  204  is operable to detect light to generate electrical signal in response to the detected light.  
         [0032]     The emitter portion  207  of the leadframe substrate  206  lies at an emitter angle  207 A relative to the base portion  205  such that light  214  emitted by the emitter  202  is generally directed at a desired direction. In the illustrated example, the desired direction is toward a code scale  120  and generally in the direction toward the detector  204 . Light rays  214  and similar indicators in the Figures are used to illustrate general direction of the light; these ray indicators are not intended to be trace rays oft used in the field of optics.  
         [0033]     The detector portion  209  of the leadframe substrate  206  lies at a detector angle  209 A relative to the base portion  205  such that reflected light  216  (light reflected from a code scale  120 ) is generally directed toward the detector  204 . In the illustrated example, the emitter angle  207 A and the detector angle  209 A have opposing direction; however, the absolute value of the emitter angle  207 A and the absolute value of the detector angle  209 A. The emitter  202  and the detector  204  are encapsulated by encapsulant  208  material.  
         [0034]     As illustrated, due to the angled mounting of the emitter  202  and the detector  204 , the emitted light  214  and the reflected light  216  are directed in the desired direction without requiring lenses as required in the optical encoder  100  of  FIG. 1 . For at least this reason, separation distance  230  between the emitter  202  and the code scale  120  can be much less than the separation distance  130  of  FIG. 1 . Accordingly, the device including the optical encoder  200  and the code scale  120  can be packaged in a smaller package.  
         [0035]     Furthermore, since the code scale  120  is closer to the emitter  202  and the detector  204 , either less light is needed to realize the same contrast and resolution compared to the prior art encoder  100  of  FIG. 1 , or the same amount of light provides higher contrast and resolution compared to the prior art encoder  100  of  FIG. 1 .  
         [0036]     Further increases in performances can be realized by adding lenses even to the present invention.  FIG. 3  illustrates an optical encoder  300  in accordance with another embodiment of the present invention. Portions of the optical encoder  300  are similar to corresponding portions of the optical encoder  200  illustrated in  FIG. 2  and discussed above. To avoid repetition and clutter, the reference numerals for some similar portions are not repeated in the drawing and not discussed herein.  
         [0037]     Referring to  FIG. 3 , the encoder  300  includes encapsulant  308  that defines an emitter lens  310  adapted to direct light from the emitter  202  toward the desired direction. Further, the encapsulant  308  defines a detector lens  312  adapted to direct reflected light  216  from the code scale  120  toward the detector  204 . Using the lenses  310  and  312 , separation distance  330  between the emitter-detector plane and the code scale  120  can be further decreased leading to even tighter packaging.  
         [0038]     The emitter side and the detector side of the optical encoder need not be symmetrical. For example,  FIG. 4  illustrates an optical encoder  400  in accordance with yet another embodiment of the present invention. Portions of the optical encoder  400  are similar to corresponding portions of the optical encoder  200  illustrated in  FIG. 2  and to corresponding portions of the optical encoder  300  illustrated in  FIG. 3 . To avoid repetition and clutter, the reference numerals for some similar portions are not repeated in the drawing and not discussed herein.  
         [0039]     Referring to  FIG. 4 , the encoder  400  includes encapsulant  408  includes a leadframe substrate  406  having an emitter portion  207  that lies at an emitter angle  207 A relative to the base portion  205  such that light  214  emitted by the emitter  202  is generally directed at a desired direction. This is similar to the optical encoder  200  of  FIG. 2 . However, in the encoder  400 , the detector portion  409  of lies horizontally as with the leadframe  206 . Depending on the desired application, this configuration may be useful.  
         [0040]     The present invention is adaptable to many other applications and implementations. For example,  FIG. 5  illustrates an optical encoder  500  including yet another embodiment of the present invention. Referring to  FIG. 5 , a substrate  506 , for example a silicon substrate is fabricated to include a cavity  507  having surfaces  503  and  505 . An emitter  202  is mounted on the first surface  503  of the cavity  501 , the emitter being operable to emit light. The emitter  202  is positioned such that emitted light is generally directed up and toward the center of the cavity  501 . A detector  204  is mounted on the second surface  503  of the cavity  501 , the detector being operable to detect light. The detector  204  is positioned generally facing center of the cavity so as to detect reflected light  216 .  
         [0041]     Here, the substrate  506  is a solid silicon substrate. This is an alternative implementation of the present invention compared to the implementations illustrated in  FIGS. 2 through 4  where leadframe substrates  206  and  406  are used.  
         [0042]     Another aspect of the present invention is a method of manufacturing an apparatus including an optical encoder such the encoder  200  of  FIG. 2 .  FIG. 6  illustrates a flow chart  600  including the steps of the method in accordance with yet another aspect of the present invention. Referring to  FIG. 6 , a leadframe substrate is provided. Step  602 . The leadframe substrate  206  is, at this stage of manufacture, a flat piece of leadframe having one or more connection traces. A cutaway side view of the provided leadframe  206  is illustrated in  FIG. 7A .  
         [0043]     Referring to  FIGS. 6 through 7 B, an emitter  202  is mounted on the leadframe substrate  206 . Step  604 . Also, a detector  204  is mounted on the leadframe substrate  206 . Step  606 . Then, the leadframe  206  is bent to form base portions  205  and an emitter portion  207 . Step  608 . The resulting shape of the bent leadframe is illustrated in  FIGS. 7B and 2  as the leadframe  206 . Portions of  FIG. 2  including the leadframe  206  are reproduced as  FIG. 7B  for convenience of discussion. The bent leadframe  206  includes the base portions  205 , the emitter portion  207 , and the detector portion  209 . The emitter portion is at the emitter angle  207  relative to the base portion  205 . Finally, the emitter  202 , the detector  204 , and portions of the substrate  206  are encapsulated using encapsulant  208  such as clear epoxy, resulting in the optical encoder  200  of  FIG. 2 .  
         [0044]     In alternative embodiments, the steps of the flowchart  600 , with slight modifications, can be use to manufacture the optical encoder  300  of  FIG. 3  and the optical encoder  400  of  FIG. 4 . For example, to manufacture the optical encoder  300  of  FIG. 3 , during the encapsulation step, the encapsulant is used to form the lenses  310  and  312  of  FIG. 3 .  
         [0045]     Yet another aspect of the present invention is a method of manufacturing an apparatus including an optical encoder such the optical encoder  500  of  FIG. 5 .  FIG. 8  illustrates a flow chart  800  including the steps of the method in accordance with yet another aspect of the present invention. Referring to  FIGS. 5 and 8 , a substrate is provided. Step  802 . The substrate  506  can be, for example, a silicon substrate. A cavity  501  is formed in the substrate  506 , the cavity  501  defines surfaces  503 ,  505  and opens to one surface (the top surface in the illustrated embodiment). Step  804 . The, the emitter  202  and the detector  204  are formed on the surfaces  503  and  505  of the cavity  501 . Steps  806  and  808 . As illustrated and also discussed above, the emitter  202  is mounted such that emitted light is generally directed up and toward the center of the cavity  501 . The detector  204  is positioned generally facing center of the cavity so as to detect reflected light  216 .  
         [0046]     From the foregoing, it will be apparent that the present invention is novel and offers advantages over the current art. Although specific embodiments of the invention are described and illustrated above, the invention is not to be limited to the specific forms or arrangements of parts so described and illustrated. For example, differing configurations, sizes, or materials may be used but still fall within the scope of the present invention. The invention is limited by the claims that follow.