JP2012233783A - Optical detecting device and electronic equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical detecting device that, as a compact and low-cost approach/direction sensor of a simple configuration using a single light receiving element, detects changes in the approaching/non-approaching state of an object body and a shifting direction orthogonal thereto at the same time and most efficiently to follow movement of a human body sufficiently.SOLUTION: A light receiving element 200 comprises a first well 301 on which a reflected light beam 103 comes directly incident, and a second well 302 and a third well 303 that are opposed to each other with the first well 301 in-between and are shielded from the reflected light beam 103, which therefore does not come incident on the second and third wells. A reception signal received by the light receiving element 200 is outputted to give alternately on a time axis the sum of the outputs of the first well 301 and of the second well 302 and the sum of the outputs of the first well 301 and of the third well 303. On the basis of this reception signal, the approaching state of an object body along a first axial direction, which is the normal vector line of the top face of the optical detecting device, and the shifting direction of the object body when its approaching state has changed are determined.

Description

  The present invention relates to a light detection device for detecting the proximity state and moving direction of an object.

  In an electronic device having a display screen such as a liquid crystal display, such as a mobile phone, a smartphone, a tablet information terminal, or a digital camera, various controls are performed by detecting the proximity of a human body to the device. The display screen of these devices also serves as an information input function as a touch panel. When an object comes close to the touch panel, such as when a call is started or the device is inserted into a pocket, the malfunction is prevented by turning off the function. There are scenes that need to be done. In the digital camera, control is performed such that the brightness of the liquid crystal screen is automatically reduced when the user moves his / her eyes from the liquid crystal screen to the viewfinder. For such applications, small and inexpensive optical proximity sensors that determine the proximity of the target object by detecting the pulsed light from the target object by itself and widely emitting light are widely used.

  By the way, when a display having a touch panel function is used, there are not a few users who feel that the screen itself is unclean due to the operation itself and frequently needs to be wiped off. In particular, an operation such as page feed, a so-called swipe operation causes the oil stains to be stretched, which is not preferable.

  Since the proximity sensor is for detecting the approach of an object (human body, for example, ear or cheek) to the screen, it is mounted in the same XY plane as the display, and the proximity of the object in the normal Z direction of the display surface A state is detected. Here, when the object (finger) approaches the sensor, if the function of simultaneously detecting the moving direction of the object in the XY plane is provided, the swipe operation can be made touchless. Since the swipe operation itself is a rough operation for switching the display content of the entire screen along the X or Y axis direction, it does not strongly restrict the mounting position of the sensor on the display plane. In addition, it is not desirable to increase the cost of an information terminal by arranging a plurality of proximity sensors, distance measuring sensors, or expensive imaging devices only to achieve such an object.

  For this reason, it is required to easily integrate the direction detection function in the proximity sensor to provide a small and inexpensive proximity / direction sensor. Thereby, for example, the touchless swipe operation of the portable information terminal can be easily realized, and the problem of the dirt on the touch panel is solved. Of course, the present invention is not limited to this, and can be developed for various other uses as a motion sensor.

  In making a proximity sensor and a direction sensor monolithic, the first thing that comes to mind is a photodetection device using a split photodiode. In such an apparatus, the moving direction of the signal light spot size on the photodiode surface can be known based on the output difference between the divided photodiodes. Here, when the total output of the entire divided photodiode is used as the signal light of the proximity sensor, the output signal of each divided photodiode is necessarily smaller than that. Even in a system in which feedback control is continuously performed so as to minimize an error signal generated from each output signal, such as tracking control of an optical disk, the function is sufficiently performed.

  However, when the split photodiode is used as a proximity / direction sensor, it is possible to determine the moving direction, that is, to detect a change in the proximity state from the front (only in the Z direction) although there is no movement in the XY direction. Needed. In such a system, in order to avoid an indefinite state (a state in which the determination result of the XY movement direction is chattered), it is necessary to perform threshold determination with sufficient S / N even for signal light used for direction detection.

  Therefore, in order to add a direction detection function to the proximity sensor by dividing the photodiode as described above, the area of the entire photodiode must be increased, or otherwise, the amount of light emission signal must be increased accordingly. As a result, the size and cost of the proximity / direction sensor increases.

  Further, in order to realize the proximity / direction detection function using a single light emitting / receiving element, the structure in the depth direction of the photodiode can be used. As a related art related to this, Patent Document 1 is cited.

  In Patent Document 1, i) light having a longer wavelength has a relatively small absorption coefficient, and a phenomenon of deeply penetrating into the photodiode; and ii) carriers generated by the light absorption are incident on the incident direction ( It is disclosed that the wavelength distribution spectrum of incident light is estimated using a phenomenon of diffusing in the XY direction perpendicular to the (Z direction).

  Although Patent Document 1 itself does not give any suggestion to the applicability of the above phenomenon to the proximity / direction sensor, the proximity / direction sensor can be realized using the above phenomenon. In that case, a light emitting device having an emission spectrum peak in the near-infrared region of a specific wavelength band (approximately 800 nm or more, more desirably 900 nm to 980 nm) that enters closer to the sensitivity peak wavelength of a silicon photodiode that is normally used. Is used. That is, carriers generated by near-infrared signal light that has entered deeply in the substrate thickness direction (Z direction) of a single silicon photodiode diffuse in the in-plane XY direction outside the photodiode while drifting. The carriers can be collected and taken out as a current in a collector region arranged outside the photodiode. By dividing the collector region, in principle, a signal used for detecting the moving direction of the detected object can be obtained without causing a significant increase in the photodiode area itself.

US Pat. No. 6,596,981 (July 22, 2003)

  However, when a proximity / direction sensor is to be realized using the above-described phenomenon disclosed in Patent Document 1, in order to realize a proximity / direction sensor that actually follows the movement of the human body and does not malfunction, the following is described. There are important conflicting issues. For this reason, the configuration itself of the proximity sensor utilizing the above phenomenon is not obvious at all.

  The first problem is that it is necessary to sample information on the proximity / movement direction so as to sufficiently follow the movement speed of the human body, which is on the order of approximately 1 m / s. In general, the size of a light receiving element used for such an application is about 100 μm to several hundreds μm square, and therefore the measurement cycle necessary for detecting the movement of the human body is about 100 μs to several hundreds μs or less. . In a measurement cycle that greatly exceeds this, information on the moving direction of the target object when the proximity / non-proximity state is switched is missed.

  On the other hand, at the moment when the proximity / non-proximity state of the target object changes and the proximity / direction sensor detects the change, and the time before and after that, the signal level is determined because the movement of the human body is relatively slow. It can be considered that the state is almost stagnant in the vicinity of the reference threshold level. As a result, the sensor is inevitably exposed to a very weak state against optical or electrical noise mixed from the signal processing circuit itself or from the outside of the circuit. For this reason, the second problem is the stability of the determination result. Whether this is a sensor that directly amplifies and reproduces the pulse waveform and counts the number of pulses, or a digital sensor that uses an A / D converter that uses an integrator and counter to integrate the pulse waveform, As long as the determination for the threshold value is made, this may be a problem.

  In the proximity sensor, the stability of the determination result is generally obtained by increasing the number of persistences (making the final determination result based on the same determination result that is repeated a plurality of times). However, increasing the number of persistences imposes a constraint contradicting the response time of the sensor, which is the first problem, and the tradeoff between response time and determination accuracy / stability is close / It becomes a more important problem in the direction sensor.

  The present invention has been made in view of the above problems, and as a small and low-cost proximity / direction sensor having a simple configuration using a single light receiving element, changes in the proximity / non-proximity state of a target object and the change thereof. An object of the present invention is to provide a photodetecting device for detecting the orthogonal moving directions at the same time most efficiently and sufficiently following the movement of the human body.

  In order to solve the above-described problems, the present invention provides a light detection device including a light-emitting element and a light-receiving element that receives reflected light when light emitted from the light-emitting element is reflected by a target object. The light receiving element is opposed to the first well to which the reflected light is directly incident with the first well sandwiched along the outer periphery of the first well, and the light from the light emitting element is blocked and incident. A second well and a third well, and a sum of an output of the first well and an output of the second well, and an output of the first well and the first well. The sum of outputs from the three wells is alternately signal-processed on the time axis, and a first determination representing the proximity state of the target object along the first axis direction that is the normal direction of the top surface of the light detection device. When the result and the proximity state of the target object change, the target object A signal processing circuit that outputs a second determination result representing either one of the three states of orientation or no directionality moved along the second axial direction connecting the second and third wells; It is characterized by.

  According to the above configuration, the light receiving element of the photodetection device has the first to third wells, and the first well reflects light emitted from the light emitting element by the target object. Light enters directly. The second and third wells face each other across the first well along the outer periphery of the first well. Thereby, the second and third wells can collect the carriers generated by the reflected light incident on the first well and take them out as current.

  The output currents in the first to third wells are the sum of the output of the first well and the output of the second well, and the output of the output of the first well and the third well. Signal processing is performed so that the sums alternate on the time axis. That is, the processed signal always contains the output of the first well. For this reason, in the proximity / direction sensor using a single light receiving element, it is possible to obtain good response characteristics while achieving both the functions of the proximity sensor and the direction sensor without causing an increase in the entire light receiving area. In addition, this response characteristic is such that even if the persistence for obtaining stability is set, a sufficient response characteristic that sufficiently follows the human body's operating speed can be obtained. Response time and determination accuracy / stability Can be compatible.

  In the photodetector, the light receiving element is formed on a silicon substrate, and an emission spectrum of the light emitting element has a maximum intensity at a wavelength of 900 nm to 980 nm, and the first well and the second well have a maximum intensity. The interval and the interval between the first well and the second well may be equal to or less than 10 μm.

  According to the above configuration, a silicon photodiode is used as the light receiving element, and a light emitting element having an emission spectrum peak in a wavelength band that is closer to the sensitivity peak wavelength of the silicon photodiode and enters deeper is used. Can be detected. Further, by setting the interval between the first well and the second well and the interval between the first well and the second well as described above, the carrier collection efficiency by the second and third wells is improved. You can do it.

  In the photodetector, the signal processing circuit includes a sum of an output of the first well and an output of the second well, and a sum of an output of the first well and an output of the third well. And a comparator having a multi-value output of three or more values using the same set of threshold values, and the first determination result is alternately signal-processed on the time axis. Each of the sums is determined based on whether or not they are the same as a result of comparison with any one of the set of thresholds by the comparator in succession multiple times regardless of order, The second determination result is that each of the signals subjected to signal processing immediately before the first determination result is determined is one of the set of threshold values by the comparator and used for the first determination. Judgment based on the result compared with a different threshold It is possible to adopt a configuration that.

  According to said structure, the change of the proximity | contact / non-proximity state of a target object and the moving direction orthogonal to it can be simultaneously detected efficiently using said 1 set of threshold value.

  In the photodetector, the signal processing circuit includes a sum of an output of the first well and an output of the second well, and an output of the first well and an output of the third well. An integrator that integrates the sum of the above, a comparator that compares the output of the integrator with a threshold voltage to generate a binary digital pulse signal, and an up / down counter that counts the number of pulse occurrences of the digital pulse signal (A) Up-counting or down-counting the sum of the output of the first well and the output of the second (or third) well in a state where the light-emitting element emits light, and then (B) The sum of the output of the first well and the output of the third (or second) well in the state where the light emitting element emits light is down-counted or up-counted in the opposite direction to (A), and the first The result of 1 is (A) It is determined based on whether or not the count value at the time exceeds the first threshold value, and the second determination result is (B) whether or not the count value at the end time is between the second and third threshold values. It can be set as the structure determined based on.

  According to the above configuration, using the count value of the up / down counter and the first to third thresholds, the change in the proximity / non-proximity state of the target object and the movement direction orthogonal thereto can be efficiently detected simultaneously. Can do. Further, the above-described configuration using an integrator has an advantage that the circuit block can be shared with the illuminance sensor and the RGB sensor in addition to being advantageous in S / N because the signal band is narrow.

  The photodetector includes an output terminal for outputting the second determination result. The second determination result can be any of three states of a high level, a low level, and an internally generated pulse train. It can be set as the structure output as this.

  According to the above configuration, it is possible to determine the three states related to the movement direction (the movement direction (two directions) and no movement) from the outside of the light detection device, for example, by detecting the average value of the output signals.

  In the above-mentioned photodetection device, communication means with the outside, an output terminal that outputs based on the state change of the first and second determination results, and the first and second determination results are stored, and the communication And a register that can be read from the outside by means, and the first determination result is stored in the register as 1-bit information and the second determination result is stored as 2-bit information.

  According to the above configuration, it is possible to determine the three states related to the movement direction (movement direction (two directions) and no movement) by reading the information stored in the register from the outside of the light detection device. Further, in order to detect the output signal outside, it is possible to obtain the proximity information and the information on the moving direction of the target object without generating an additional cost factor such as averaging, a window comparator, or an A / D converter. .

  Further, the photodetection device may be configured such that the light receiving element and the signal processing circuit are integrated.

  Moreover, in the said photodetection apparatus, the package of the said photodetection apparatus can be set as the structure which does not contain the lens for the said light receiving elements.

  The photodetection device of the present invention has an effect that a good response characteristic can be obtained without causing an increase in the entire light receiving area in a proximity / direction sensor using a single light receiving element. In addition, this response characteristic is such that even if the persistence for obtaining stability is set, a sufficient response characteristic that sufficiently follows the human body's operating speed can be obtained. Response time and determination accuracy / stability The effect that both can be achieved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 illustrates an embodiment of the present invention, in which (a) is a plan view of a light receiving unit of a light detection device, and (b) is a cross-sectional view of the light receiving unit. It is a perspective view explaining the use condition of the photon detection apparatus of this invention. (A), (b) is a figure explaining the whole structure of the photon detection apparatus of this invention. It is a figure explaining the whole structure of the photon detection apparatus which concerns on Embodiment 1. FIG. FIG. 4 is a waveform diagram for explaining an outline of signal processing of the photodetecting device according to the first embodiment. 3 is a circuit diagram showing a configuration of an amplifying unit of the photodetecting device according to Embodiment 1. FIG. It is a figure explaining the non-proximity → proximity and direction detection determination method of the photodetection device according to the first embodiment. It is a figure explaining the proximity | contact non-proximity and direction detection determination method of the photon detection apparatus which concerns on Embodiment 1. FIG. 6 is a circuit diagram illustrating a configuration of an amplifying unit of the photodetecting device according to Embodiment 2. FIG. FIG. 10 is a diagram for explaining a signal processing method of the photodetector according to the second embodiment. FIG. 6 is a circuit diagram illustrating a configuration of an output unit of a light detection device according to a third embodiment. FIG. 6 is a circuit diagram illustrating a configuration of an output unit of a light detection device according to a fourth embodiment. It is a figure which shows a part of portable terminal carrying the photon detection apparatus of this invention, and its use condition.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In addition, this invention is limited to description content of each embodiment shown below, and is not interpreted. It will be readily appreciated by those skilled in the art that various changes and modifications can be made without departing from the spirit and scope of the present invention. In the configuration of the present invention described below, the same components are denoted by common reference numerals, and detailed description of the same portions or portions having similar functions is omitted.

[Embodiment 1]
FIG. 2 is a diagram for explaining a situation where the light detection device 100 according to the present invention is used. In FIG. 2, a human finger 101 that is a detection target object starts to come into contact with a near-infrared beam cone 102 emitted from a light emitting element (not shown in detail) of the light detection device 100, and reflected light 103 is generated. Is drawn. The beam cone 102 is radiated along the first axis 106 that is the normal line of the top surface of the light detection device 100. Here, the light detection device 100 is illustrated as a light receiving / emitting integrated package, but the present invention is not limited to this form, and is applicable to any form such as a light receiving / emitting separate type. It will be obvious from the above.

  Further, the function as a proximity sensor in the light detection apparatus 100 is that the target object 101 is in proximity / non-proximity along the first axis 106 direction, that is, the optical axis direction of the light emitting element (or the normal direction of the light receiving element surface). Detect state. 2 shows a light emitting element and a light receiving element (details not shown) with respect to the moving direction of the target object 101 along the second axis (that is, the 105 direction) to be detected as the direction sensor. ) Is shown as an example in which the axis 104 connecting them is vertically arranged. This example is a convenient arrangement for easy understanding of the following description, and the second axis 105, the detection direction, and the axis 104 connecting the light emitting element and the light receiving element are not necessarily perpendicular to each other. There is also no need to be strictly vertical or parallel. The second axis 105 is an axis determined as a specification of a host system on which the photodetection device 100 is mounted regardless of the photodetection device. The definition of the axial direction unique to the present photodetection device to be associated with the second axis 105 will be described in more detail later with reference to FIG.

  3A and 3B show details of the internal structure of the photodetecting device 100 of FIG. FIG. 6A shows the axis 104 in the horizontal direction of the drawing, and FIG. 6B shows the axis 104 in the normal direction of the drawing. The light detection device 100 includes a light receiving element 200 and a light emitting element 202, and the light receiving element 200 is integrated as a part of the signal processing circuit 201. A driving circuit for the light emitting element 202 can also be included in the signal processing circuit 201. FIGS. 3A and 3B show a state where the finger 101 further moves in the 105 direction from the state of FIG. 2 and the reflected light 103 from the finger 101 enters the light receiving element 200 provided. In addition, the mutual wiring, terminal wiring, and the like inside the light detection device 100 are arbitrary and are omitted because they can be easily conceived by those skilled in the art.

  A structure having a lens action is not provided around the light receiving portion of the light detection device 100, and a mold made of a flat resin that absorbs less infrared rays is applied. This is the simplest and most reliable design among the desirable designs in a situation where the target object moves in the direction 102 while approaching the light detection device 100. The desirable design here is a design in which the reflected light 103 starts to enter from the end of the light receiving element 200 and the amount of incident light monotonously increases as the target object 101 moves. Of course, a lens structure may be provided above the light receiving element 200. In this case, however, the reflected light 103 obliquely incident on the light receiving element 200 from a portion other than the lens and the reflected light 103 imaged through the lens are received by light. Since the incident position differs greatly with respect to the element 200, it is necessary to design carefully.

  Further, around the light emitting element 202 of the package of the light detection device 100, a beam shaping lens 203 and a light absorbing portion 204 for avoiding direct incidence to the light receiving portion are provided. The design details of these structures are arbitrary, and various modifications such as the absence of the light-absorbing portion 204 or the absence of a beam shaping lens on the light-emitting side are possible by a separate light receiving and emitting (separate) package.

  FIG. 1A shows a more detailed structure of the light receiving element 200 as a cross section similar to FIG. FIG. 1B is a top view of the light receiving element 200. As shown in FIGS. 1A and 1B, the light receiving element 200 is configured by providing a first well 301, a second well 302, and a third well 303 on a p-type silicon substrate 300. Has been. The first well 301 functions as a photodiode. The second well 302 and the third well 303 have a stacked structure similar to that of the first well 301, and are arranged to face each other with the first well 301 sandwiched along the outer periphery of the first well 301. .

  In the light receiving element 200, the axis connecting the second well 302 (center of gravity) and the third well 303 (center of gravity) is made to coincide with the second axis 105 where the moving direction of the target object 101 should be detected. .

  In the example of FIGS. 1 and 3, the emission spectrum of the light emitted from the light emitting element 202 is close to the sensitivity peak wavelength of the silicon photodiode used for the light receiving element, and enters a specific wavelength band that enters deeper (approximately 800 nm or more, more Desirably, it has a maximum intensity of 900 nm to 980 nm. For this reason, the emission spectrum of the light emitting element 202 has an intensity peak at a wavelength of 940 nm, and the thickness of the p-type silicon substrate 300 is set to 400 μm so as to absorb almost 100% of incident light. The first to third wells have n-type conductivity, and the depth of the junction surface with the p substrate is about 4 μm.

  The second well 302 and the third well 303 are shielded by an optically thick metal layer 304 (for example, an Al layer having a thickness of 1 μm) so that light from the upper surface of the silicon substrate 300 does not enter. Insulating layers used in a normal silicon process are formed above and below and around the metal layer 304 (detailed structure is not shown).

  On the other hand, the first well 301 has a structure in which the reflected light 103 from the target object 101 is optically opened including the insulating layer. This does not necessarily mean that there is no metal layer above the first well. For example, a stacked body (not shown) in which a dielectric having a thickness of several hundred nm is sandwiched between a pair of noble metal layers (for example, Ag) having a thickness of several tens of nm is used as a Fabry-Perot etalon at a specific wavelength, that is, the light emitting element 202. It is well known that it can be designed to be almost transparent with respect to the wavelength peak, and the combination with the light receiving part mold using the flat plate resin shown in FIG. 3 is also preferable for the present invention.

  Here, the distance 305 between the first well 301 and the second well 302 or the third well 303 is all within 10 μm (here, 5 μm), and the width 306 of each well is 20 μm. The diffusion length of electrons, which are minority carriers in the p-type silicon substrate 300, is approximately 5 to 10 μm. With the above structure, carriers generated by light absorption immediately below the first well 301, that is, the most peripheral part of the photodiode, are The second well 302 or the third well 303 in the vicinity is efficiently collected. This is a structure necessary for direction detection with a single photodiode.

In the above example, the width 306 of the second well 302 or the third well 303 is desirably about 10 to 100 μm. This means that the selection may be made within the range of the reciprocal of the absorption coefficient (about 120 cm ⁻¹ ) at the wavelength of the signal light (here, 940 nm) or about 1/10 thereof. However, if the width 306 is too small, the above-described collection efficiency is lowered, and if it is too large, the overall size of the light receiving element 200 is increased. As a result of detailed studies, for example, for near infrared light of 900 to 940 nm, the width 306 of the second and third wells is more preferably set to about 20 to 50 μm, and signal processing described below is used. As a result, it was found that a practically sufficient direction detecting action can be obtained. Similarly, for other wavelengths, good direction detection characteristics can be obtained by selecting the width 306 of the second and third wells with a range from the reciprocal of the absorption coefficient at the wavelength to 1/10 thereof as a guide.

  The width 307 of the first well 301 can be arbitrarily set as long as it is larger than the widths of the second and third wells. This is because, as will be described in detail later, the action of the direction detection described above is to collect carriers generated immediately below the second or third well in a situation where signal light is incident only on the outermost peripheral portion of the photodiode. It is because it is obtained by doing. As is clear from this reason, it is desirable that the lengths of the first to third wells shown in FIG. 1B in the direction of the axis 104 are equal to each other. The size is approximately the same as the width 307. For the purpose of improving the direction detection characteristic, the shape of the first well may be rectangular or other shapes. However, the second and third wells always have the distance 305 to the first well. By contacting the boundary, the detection effect of the moving direction of the target object 101 along the second axial direction connecting the second and third wells, that is, the direction 105 perpendicular to the axis 104, maintains high area use efficiency. Realized.

  An example of details of signal processing in the photodetection device 100 described so far with reference to FIGS. 1 to 3 will be described with reference to FIGS.

  Currents are output from the first to third wells 301 to 303 to the signal processing circuit 201, respectively. However, the output currents 402 and 403 of the second well 302 and the third well 303 are connected to the signal processing circuit 201 via the switches 404 and 405, respectively. Similarly, the output current 401 of the first well 301 may be connected via a switch. However, as long as the light detection device 100 operates as a proximity sensor, it is only necessary to maintain the connection state. Here, the switch corresponding to the first well is omitted. In order to simplify the notation, in FIG. 4, the diodes formed by the first to third wells 301 to 303 and the substrate 300 are denoted by the same numbers as the wells, and are placed on the second and third wells. The formed metal layer 304 is also shown schematically. However, from the viewpoint of electromagnetic noise resistance, the actual metal layer 304 is normally given a GND potential, and the potential is different from each current output node.

  Here, the switches 404 and 405 are respectively controlled by control signals 408 and 409 generated by the control unit 407 of the signal processing circuit 201, and are opened and closed in a sequence as shown in FIG. That is, the sum of the output current 401 and the output current 402 and the sum of the output current 401 and the output current 403 are alternately input on the time axis to the amplifying unit 406 in the signal processing circuit 201 for signal processing. . As shown in the figure, hereinafter, each of the signal processing periods is referred to as an [A] phase and a [B] phase. Details of this signal processing will be described later with reference to FIGS. When this signal processing is performed and the detection result of proximity / non-proximity or movement direction is determined, a signal 413 for driving the output unit 412 is output from the control unit 407 and output signal 414 to the outside of the light detection apparatus 100. Is output. The light emitting element 202 is also driven by a control signal 410 sent from the control unit 407 to the light emitting element driving circuit 411. Each of the signals shown in FIG. 5 is a digital signal of H level or L level, and the pulse width of the control signal 410 is typically 10 μs and the repetition period is about 100 μs.

  Next, an amplification unit 601 is shown in FIG. 6 as one specific example of the amplification unit 406. The amplifying unit 601 amplifies the ON / OFF waveform of the transmission light pulse from the received light signal 600 and reproduces it to a binary digital level. As described above, the light reception signal 600 is either the sum of the output current 401 and the output current 402 or the sum of the output current 401 and the output current 403 that are alternately input on the time axis. The received light signal 600 is converted into a voltage signal 603 by a transimpedance amplifier 602, and after being AC-coupled, is branched into two (signal 604), and is compared with threshold voltages 605 and 606 by comparators 607 and 608, respectively. Digital pulse signals 609 and 610 are reproduced. As a whole, the comparator 611 is a 2-bit multi-value output. The reproduction signals 609 and 610 are held by a flip-flop (FF) included in the control unit 407.

  Here, the manner in which the received light signal 600 to each of the amplified signals change in accordance with the situation of FIG. 3 and the signal processing performed by the control unit 407 will be described with reference to FIG. In the situation of FIG. 3, the target object 101 moves in the direction 105 in FIG. 1 while the train of light pulses emitted based on the driving waveform 410 of the light emitting element described in FIG. Proximity to the photodetection device 100.

  In this situation, as shown in FIG. 7, the amplitude of the output pulse voltage 603 of the transimpedance amplifier 602 increases with time. In the optical system having no lens function in the light receiving section as shown in FIG. 2, the reflected light 103 starts to enter from the second well side shown in FIG. 3 or FIG. Therefore, as a result of the signal switching process by the control signals 408 and 409 shown in FIG. 4 or FIG. 7, the amplitude of the signal 603 in FIG. 7 increases in the [A] phase before the [B] phase. However, since the output current 401 of the first well is commonly included in the output of any phase, the amplitude of the signal 603 is maintained at about [A] phase / [B] phase ratio of about 2 at the maximum. Increase. In FIG. 7, the signal amplitude is abruptly increased for the sake of clarity. However, as described above, the slope at which the amplitude of the signal 603 increases in the actual operation depends on the moving speed of the human body and the light receiving unit 200. This time scale is so gentle that it is hardly understood from the size relationship.

  In this situation, the threshold 605 and the threshold 606 given to the comparators 607 and 608 as reference voltages are the non-proximity → proximity detection threshold, and the threshold 606 is a threshold for detecting the moving direction. As can be seen from FIG. 7, the control unit 407 continuously monitors whether the signal 609 reproduces the light emission pulse three times in succession, and the first determination result of non-proximity → proximity is obtained (persistence). Example of stance = 3).

  Here, the second determination, that is, the determination of the moving direction is performed from the output (signal 610) of the comparator 608 in each phase [A] and [B] immediately before the first determination is performed. Note that the output immediately before the comparator 608 is held in the flip-flop of the control unit 407. In FIG. 7, the first determination occurs at the end of the [A] phase, the [A] phase comparator output at that time has pulse regeneration, and the immediately preceding [B] phase comparator output has no pulse regeneration. .

  As described above, when a transition is made from non-proximity to proximity, and the presence or absence of pulse regeneration differs between the previous [A] phase and [B] phase, it can be determined that the moving direction has occurred in the direction from the presence or absence of pulse regeneration. That is, in the above example, the direction from the second well to the third well (the direction from the first and second sum [A] side to the first and third sum [B] side), and accordingly, the axis 105 2 can be determined to have occurred in the right direction of FIG. In addition, when a transition is made from non-proximity to proximity, and the presence or absence of pulse regeneration in the immediately preceding [A] phase and [B] phase is equal, the target object is in the direction connecting the second and third wells perpendicular to the proximity direction. It can be determined that there was no movement. The area for determining that there is no directionality (the lateral movement is not accompanied by the proximity movement) can be adjusted by the difference between the threshold values 606 and 605. For example, by reducing the difference between the thresholds 606 and 605, the lateral movement of the finger 101 along the axis 105 in FIG. 2 is much slower than the proximity speed along the axis 106, that is, the finger 101 moves along the axis 106. Even in the case where the angle between the two is close from a small distance, direction detection is possible (the angle range in which it is determined that there is no directionality becomes narrow). Conversely, by increasing the difference between the thresholds 606 and 605, the angle range for determining that there is no movement in the direction of the axis 105 (no directionality) when the angle between the finger 101 and the axis 106 is small.

  Next, the case where the target object 101 in the proximity state moves away from the light detection apparatus 100 will be described with reference to FIG. The moving direction in the plane is also directed from the third well to the second well, contrary to the example of FIG. In this case, as shown in FIG. 8, the amplitude of the output pulse voltage 603 of the transimpedance amplifier 602 decreases with time. For the same reason as described in FIG. 7, the amplitude of the signal 603 in FIG. 8 decreases in the [B] phase before the [A] phase, and the [A] phase / [B] phase of the amplitude of the signal 603 The ratio is kept at about 2 at the maximum.

  Here, in a situation where the proximity state of the target object 101 is determined, it should be noted that the meanings of the threshold values 605 ′ and 606 ′ illustrated in FIG. 8 are changed as follows. Here, the threshold value 605 ′ is a criterion for the determination of proximity to non-proximity, and the threshold value 606 ′ is a threshold value for determining the direction of movement. The magnitude relationship between the threshold value for direction determination and the threshold value for non-proximity detection is different from the non-proximity → proximity case in FIG. 7, and the threshold value 606 ′ for direction determination is different from that for non-proximity detection. It is smaller than the threshold value 605 ′.

  This is an essential change in order to detect a difference in signal amplitude between the [A] phase and the [B] phase immediately before the first determination is made. As is apparent from a comparison between FIGS. 7 and 8, in FIG. 8, after it is determined that there is no three-time continuous pulse regeneration, the signal amplitude decreases to an extent that it can no longer be detected. For this reason, it is necessary to make the threshold value 606 'for direction determination smaller than the threshold value 605' for non-proximity detection.

  As can be seen from FIG. 8, the control unit 407 continuously monitors whether the signal 609 is detected three times in succession to detect the absence of the light emission pulse, and the first determination result of proximity → non-proximity is obtained. (Example of persistence = 3). Then, the second determination, that is, the determination of the moving direction is performed from the output (signal 610) of the comparator 608 in each phase [A] and [B] immediately before the first determination is performed. In FIG. 8, the first determination occurs at the end of the [B] phase, the [B] phase comparator output at that time has no pulse regeneration, and the immediately preceding [A] phase comparator output has pulse regeneration. .

  As described above, when the state transitions from proximity to non-proximity and the presence / absence of pulse regeneration differs between the immediately preceding [A] phase and [B] phase, it can be determined that the moving direction has occurred in a certain direction from the absence of pulse regeneration. In other words, in the above example, it can be determined that it has occurred in the direction from the third well to the second well, in the left direction in FIG. Further, when the state transitions from proximity to non-proximity and the previous [A] phase and [B] phase have the same pulse reproduction presence / absence, the target object is in the direction connecting the second and third wells perpendicular to the proximity direction. It can be determined that there was no movement. The region where it is determined that there is no directionality (the lateral movement is not accompanied by the proximity movement) can be adjusted by the difference between the threshold values 606 'and 605'.

  As described above, when the four threshold values shown in FIGS. 7 to 8 satisfy the following relationship, malfunction of the photodetection device 100 is prevented and the operation is stable.

606 (non-proximity → direction determination when approaching)> 605 (proximity → non-proximity determination)
> 605 ′ (non-proximity → proximity determination)> 606 ′ (proximity → non-proximity direction determination)
Note that the difference between the above set of threshold values (606, 605, 605 ′, 606 ′) or the minimum value of the threshold value 606 ′ is the actual in-circuit noise described in detail in the second and subsequent embodiments. Needless to say, it should be set within a range in which malfunction due to noise does not occur.

  As described above, in the photodetecting device 100 according to the first embodiment, the determination of proximity / non-proximity and directionality can be stably completed with three persistences, and the movement of the target object is about 300 μs. It is possible to respond to

  As described above, as a small and low-cost proximity direction sensor with a simple configuration using a single light receiving element, the proximity / non-proximity change of the target object and the direction of movement perpendicular to it can be detected efficiently at the same time. As a result, a light detection device for sufficiently following the movement of the human body could be realized.

[Embodiment 2]
In the second embodiment, an amplification unit 901 is shown in FIG. 9 as another specific example of the amplification unit 406. As will be described below, the amplifying unit 901 converts the received light signal 900 into a voltage pulse train corresponding to its intensity, and is used to configure an A / D converter, more specifically, a VFC (voltage-frequency converter). It has been. Hereinafter, as in the description of FIG. 7, the target object 101 moves in the direction 105 of FIG. 1 while the train of light pulses emitted based on the drive waveform 410 of the light emitting element is reflected by the target object 101, and the light Description will be made assuming a situation in which the detection apparatus 100 is approaching.

  First, the operation of the amplifier 901 will be described with reference to FIG. As described above, the light reception signal 900 is either the sum of the output current 401 and the output current 402 that are alternately input on the time axis, or the sum of the output current 401 and the output current 403. The received light signal 900 is converted into a voltage ramp waveform 903 by an integrator 902 and compared with a threshold voltage by a comparator 904. When the lamp output 903 exceeds the threshold voltage, a binary digital pulse signal 905 having a very short constant width is generated (one shot). This pulse is used for resetting the integrator 902 and is input to the up / down counter of the control unit 407 to count the number of pulse generations.

  Next, as in the case of the pulse regeneration type amplifier of FIGS. 7 to 8, when the [A] phase and [B] phase are alternately amplified (integrated), as shown in FIG. Switch between up and down and count. That is, the first determination of proximity / non-proximity is performed from the count value at the time of switching between the [A] phase and the [B] phase. The threshold value used for this determination is 906 in the figure. In addition, a second determination regarding directionality is performed from the count value at the end of the [B] phase. The threshold values used for this determination are 907 and 909 in the figure. In FIG. 10, the count of the [A] phase is counted up and the count of the [B] phase is counted down, but these count directions may be reversed.

  In the proximity / direction according to the second embodiment, the counter is reset to the reset value 908 before the start of the [A] phase. Then, the count value at the time of switching between the [A] phase and the [B] phase, that is, the count value based only on the [A] phase is compared with the threshold value 906. The count value increases when the reflected light 103 is received by the first well 301 increases. Therefore, if the count value is larger than the threshold value 906, it is determined that the proximity state of the target object 101 has occurred at that time. .

  When the proximity of the target object 101 is detected, directionality determination is subsequently performed at that time. Here, since the directionality determination is completely different from the examples of FIGS. The threshold values 907 and 909 for determining the directionality are set symmetrically in the ± direction with respect to the reset value 907. If the count value at the end of the [B] phase is between the threshold values 907 and 909, it is determined that there is no directionality. This is due to the following reason. If the count value at the end of the [B] phase is between the threshold values 907 and 909, it is considered that the count number in the [A] phase and the count number in the [B] phase are substantially equal. In this case, since it is considered that the reflected light 103 is received at substantially the center of the first well 301, it is determined that the proximity of the target object 101 is not due to the movement along the second axis 105. .

  Next, consider a case where the target object 101 moves along the second axis 105 in a direction from the second well toward the third well. In this case, as the target object 101 approaches the first well, the received light amount of the reflected light 103 increases, so that the number of counts in the [A] phase increases, and the proximity according to the first determination is eventually reached. Detected. At this point, the reflected light 103 has a strong intensity on the second well side, and it is considered that the count number in the [A] phase is large and the count number in the [B] phase is small. Therefore, if the count value at the end of the [B] phase is larger than the threshold value 907, it is determined that there is a movement from the [A] phase to the [B] phase, that is, from the second well to the third well. To do.

  On the other hand, when the target object 101 moves along the second axis 105 in the direction from the third well toward the second well, the reflected light 103 is reflected at the time of detection of proximity according to the first determination. 3 well side has strong strength. For this reason, the count number in the [A] phase is small, and the count number in the [B] phase is large. Therefore, if the count value at the end of the [B] phase is smaller than the threshold value 909, it is determined that there has been a movement from the [B] phase to the [A] phase, that is, from the third well toward the second well. .

  The comparison of the count values is performed by digital calculation (not shown) in the control unit 407, and the entire circuit scale of the amplifier and the control unit related to the series of signal processing is shown in FIGS. Compared with the case of using the described pulse regenerative amplifier (601), the size can be significantly reduced. On the other hand, in the second embodiment, it is necessary to set the drive pulse width of the light emitting element and the generation pulse width of the [A] phase [B] phase to a longer time than in the first embodiment. For example, it takes 100 μs to generate an output voltage of 1 V in the integrator 902 having a feedback capacitance of 1 pF with the received light signal 900 of 10 nA. If a time of 100 μs is given to each phase of [A] and [B] in FIG. 10, it takes 200 μs for one measurement, and even if the light emitting element is driven at a duty of 50%, the response time when persistence = 3 is set. Is as long as 1.2 ms. However, it can be said that the response time of 1.2 ms can sufficiently follow the movement of the human body as a proximity direction sensor, although the power consumption due to this increases. Further, the second embodiment using an integrator is useful because there is a merit that a circuit block can be shared with an illuminance sensor and an RGB sensor in addition to being advantageous in S / N because the signal band is narrow. .

  9 to 10, the photodetector 100 using the VFC type A / D converter has been described. However, the present invention is not limited to this, and an arbitrary charge balance type, ΣΔ type, or the like can be used. The present invention can be applied to A / D converters. Further, the signal processing method of FIG. 10 can be modified within a range that does not impair the feature of efficiently performing proximity detection and direction detection by alternately performing signal processing of the [A] phase and [B] phase with an up / down counter. Is possible. For example, one integration period is provided for each of the [A] phase and the [B] phase, but the [A] phase and the [B] phase are further divided into [A1], [B1], [B2], If the symmetry is enhanced as [A2], it is possible to more efficiently reduce the influence of fluctuation components of DC to extremely low frequency such as background light.

  As described above, as a small and low-cost proximity direction sensor with a simple configuration using a single light receiving element, the proximity / non-proximity change of the target object and the direction of movement perpendicular to it can be detected efficiently at the same time. Thus, a light detection device for following the movement of the human body could be realized.

[Embodiment 3]
In the first and second embodiments, a binary or ternary state is respectively set for the proximity / non-proximity state that is the first determination result or the movement direction in the proximity / non-proximity state that is the second determination result. The means for detecting has been described in detail. In the third embodiment, a means for outputting the determination result to the outside of the light detection apparatus 100 will be described. This means can be applied to any of the above embodiments,
FIG. 11 shows a detailed configuration example of the output unit 412 described in FIG. In this example, an output stage 412a for the first determination result and an output stage 412b for the second determination result are provided separately, and both are configured as CMOS inverters. The circuit configuration of the output stage 414a or 414b is not limited to the CMOS inverter shown in FIG. 11, and may be a general open drain output.

  The output signal 414a of the output stage 412a can represent two states, for example, a non-proximity state when H and a proximity state when L. Alternatively, the output signal 414a of the output stage 412a is preferably an alert signal to the outside. For example, the output signal 414a transitions from H to L only when a change occurs in the first determination result, and outputs a One Shot pulse that transitions from L to H again after a predetermined time. For such an output signal 414a, the output signal 414a can be externally counted by a 1-bit counter to obtain a proximity / non-proximity determination result. Alternatively, the output signal 414a of the output stage 412a is a so-called interrupt output that holds the L level until the output signal 414a transitions from H to L only when the first determination result changes and is cleared from the outside. You can also Also in this case, a proximity / non-proximity determination result can be easily obtained from the outside by counting the output signal 414a with a 1-bit counter.

  On the other hand, the output stage 412b needs to represent three states: the direction of movement of the symmetrical object, or no directionality. For this reason, it is possible to correspond to the output signal 414b as follows. That is, when the output signal 414b is fixed at the high level, it indicates that the target object has moved in the direction from the second well 302 to the third well 303 in accordance with the proximity / non-proximity state change. If fixed, it indicates that there was a reverse movement. Further, when an internal clock signal used for timing generation in the control unit 407 inside the light detection device is output as the output signal 414b, the target object moves in the in-plane direction due to the proximity / non-proximity state change. It shall indicate that there was no movement. Alternatively, a periodic pulse train in which the duty is changed may be output instead of the clock signal itself. By configuring the output stage 412b that outputs the second determination result in this way, the three states related to the moving direction are determined from the outside of the light detection device 100 by detecting, for example, the average value of the output signal 414b. be able to.

  As described above, a photodetecting device for efficiently detecting the change in the proximity / non-proximity state of the target object and the movement direction orthogonal thereto simultaneously and following the movement of the human body has been realized.

[Embodiment 4]
In the fourth embodiment, another configuration example of the output unit 412 described in FIG. 4 will be described with reference to FIG.

  This configuration example can also be easily applied to the embodiment described in Embodiments 1 and 2 or any embodiment derived therefrom. In this configuration, general-purpose serial communication is used as a communication means between the light detection apparatus 100 and the outside. For example, a serial bus standard such as I2C can be used. However, in addition to the two terminals SDA and SCL as communication means with the outside, an interrupt output circuit 414 for alerting a change in the state of the determination result is usually required. This situation also applies to a single proximity sensor, and is not a problem specific to the configuration of the proximity direction sensor.

  With the above configuration, a 1-bit register can be allocated to the first determination result and a 2-bit register can be allocated to the second determination result to enable external reading. For example, for the 2-bit register for the second determination result, 11: no directionality, 10: movement from the third well to the second well, 01: the second well to the third well It is possible to map the determination result such as moving in the direction of, 00: no directionality.

  In the above configuration, the external device is notified of the state change of the determination result by the output signal 414 from the output terminal 412. The external device that has received this notification accesses the register in the control unit 407 from the SDA and SCL terminals, and reads the determination result stored in this register. Therefore, in order to detect the output signal 414 of the output terminal 412 externally, the proximity information of the target object and the information on the moving direction are not generated without generating an additional cost factor such as averaging, a window comparator, or an A / D converter. Can be obtained.

  In this way, as a small and low-cost proximity direction sensor with a simple configuration using a single light receiving element, the proximity / non-proximity change of the target object and the direction of movement perpendicular to it can be detected efficiently at the same time. In this way, a photodetection device can be configured to sufficiently follow the movement of the human body.

[Embodiment 5]
A portable terminal (electronic device) 110 on which the photodetector 100 described in Embodiments 1 to 4 is mounted is illustrated in FIG. In FIG. 13, the terminal 110 includes a multi-touch display (touch panel) 111, and the light detection device 100 is embedded in the lower part of the display as viewed from the user of the terminal 110. The longitudinal axis of the photodetecting device 100 in FIG. 13 is 90 degrees different from the example shown in FIGS. 1 to 3, but the second and third wells of the light receiving element 200 mounted therein are arranged. If the connecting axis substantially coincides with the direction 105 in FIG. 13, there is no problem and it is merely a modification.

  With such a configuration of the mobile device, at least the swipe operation in the direction 105 in FIG. 13 can be made touchless. In particular, since the direction is detected only when the output as the proximity sensor is changed, an extra direction detection output is not generated, and the malfunction as a device is not caused. In this way, the problem of the oil and dirt on the display due to the swipe operation has been solved by a single proximity sensor that is extremely low cost and space-saving.

  As is apparent from the above description, it is easy to extend the light detection device 100 according to the present invention to XYZ, 3-axis proximity sensor (Z: proximity, X, Y: direction). That is, the fourth and fifth wells are arranged to face each other across the first well so as to be perpendicular to the axis connecting the second and third wells, and in signal processing, the second and third wells are arranged. In addition to the [A] phase and [B] phase signal processing for the wells of [5], the [C] phase and [D] phase signal processing for the fourth and fifth wells are performed, and the determination result output is the same. In addition, it is only necessary to add the ternary state by using the fourth to fifth embodiments. As a result, the photodetection device of the present invention can be used not only for a single-axis swipe operation but also for sensing various user motions in the mobile terminal 110.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  INDUSTRIAL APPLICABILITY The present invention can provide a small and low-cost proximity direction sensor with a simple configuration using a single light receiving element, and can be used for an electronic device such as a mobile phone, a smartphone, a tablet information terminal, or a digital camera. it can.

100 Photodetector 101 Target object 111 Multi-touch display (touch panel)
200 light receiving element 201 signal processing circuit 202 light emitting element 300 p-type silicon substrate 301 first well 302 second well 303 third well 406 amplifying unit 407 control unit 412 output unit

Claims (9)

A light detection device comprising: a light emitting element; and a light receiving element that receives reflected light when light emitted from the light emitting element is reflected by a target object.
The light receiving element is opposed to the first well into which the reflected light is directly incident with the first well sandwiched along the outer periphery of the first well, and the light from the light emitting element is blocked. A second well and a third well not incident,
Further, the sum of the output of the first well and the output of the second well and the sum of the output of the first well and the output of the third well are alternately signaled on the time axis. A first determination result representing a proximity state of the target object along the first axial direction that is a normal direction of the top surface of the light detection device, and the target object when the proximity state of the target object changes Includes a signal processing circuit that outputs a second determination result representing either one of the three states of orientation or no directionality moved along the second axial direction connecting the second and third wells. A photodetection device. The light receiving element is formed on a silicon substrate,
The emission spectrum of the light emitting element has a maximum intensity at a wavelength of 900 nm to 980 nm,
The distance between the first well and the second well and the distance between the first well and the second well are equal to or less than 10 μm, respectively. Photodetector. The signal processing circuit includes:
The same set of outputs for the sum of the output of the first well and the output of the second well and the sum of the output of the first well and the output of the third well A comparator having a multi-value output of three or more values using a threshold;
The first determination result is that each of the sums subjected to signal processing alternately on the time axis is continuously repeated a plurality of times regardless of the order, and any one of the threshold values of the set of threshold values is compared by the comparator. As a result of the comparison, it is determined based on whether or not they are the same,
The second determination result is obtained by calculating whether each of the sums subjected to signal processing immediately before the determination of the first determination result is one of the set of threshold values by the comparator and performing the first determination. The photodetection device according to claim 1, wherein the photodetection device is determined based on a result of comparison with a threshold different from that used. The signal processing circuit includes:
An integrator for integrating the sum of the output of the first well and the output of the second well, and the sum of the output of the first well and the output of the third well;
A comparator for comparing the output of the integrator with a threshold voltage to generate a binary digital pulse signal;
An up / down counter for counting the number of times the digital pulse signal is generated,
(I) Up-counting or down-counting the sum of the output of the first well and the output of the second or third well in a state where the light-emitting element emits light,
(II) The sum of the output of the first well and the output of the third or second well in a state where the light emitting element emits light, down-counts or up-counts in the opposite direction to (I),
The first determination result is determined based on whether (I) the count value at the end time exceeds a first threshold value,
The second determination result is determined based on (II) whether or not the count value at the end time is between the second and third threshold values. Light detection device. An output terminal for outputting the second determination result;
5. The light according to claim 1, wherein the second determination result is output as one of three states of a high level, a low level, and an internally generated pulse train. 6. Detection device. A means of communication with the outside;
An output terminal for outputting based on a state change of the first determination result and the second determination result;
The first determination result and the second determination result are stored, and at least a register readable from the outside by the communication unit,
5. The photodetection device according to claim 1, wherein the first determination result is stored in the register as 1-bit information and the second determination result is 2-bit information. 6. .   The photodetection device according to claim 1, wherein the light receiving element and the signal processing circuit are integrated.   The light detection device according to claim 7, wherein the package of the light detection device does not include a lens for the light receiving element.   An electronic device comprising a touch panel, wherein at least a swipe operation on the touch panel is made touchless by mounting the photodetection device according to any one of claims 1 to 8. machine.

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