JP2014002077A - Position detector using reflective photosensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve detection of a specific position like an origin position with a simple configuration at a low cost.SOLUTION: At, for example, each of both end parts of a reflecting plate 10 having reflecting surfaces sa and non-reflecting surfaces sb alternately arranged in a movement direction of a moving object, a wide reflecting surface Twider than the reflecting surface (or the non-reflecting surface) in the movement direction is provided as a peculiar pattern where an alternation pattern is peculiarly varied. A photodetector 14 of a reflective photosensor 12 is provided with three light receiving parts 14a to 14c having light receiving areas different in a movement direction of the reflecting plate 10, so that outputs signals A to C different in phase difference can be obtained from the three light receiving parts 14a to 14c. A movement position of the reflecting plate 10 is detected by outputs A and B having a 90° phase difference, and a midpoint potential is calculated from outputs A and C having a 180° phase difference, and an end position of the reflecting plate 10 (for example, a start point and an end point of a lens barrel) is detected by the wide reflecting surfaces T.

Description

  The present invention relates to a position detection apparatus using a reflective photosensor, and more particularly to an apparatus for detecting the position and amount of movement of a movable body in an apparatus such as a digital still camera, a lens interchangeable camera, a camcorder, and a surveillance camera.

  Conventionally, for example, in digital still cameras, interchangeable lens cameras, camcorders, surveillance cameras, etc., lenses are driven using various actuators, and position detection devices (sensors) are used to perform position sensing of these movable lenses. ) Is used.

  For example, as a detection device for the position and amount of movement of a movable lens for focusing and zooming, a type using a pulse generator such as a stepping motor method, or an analog change using an optical sensor or a magnetic sensor in a piezo motor method There is a type that detects the amount. Examples of the former include Japanese Patent Laid-Open No. 04-9712 (Reference 1), and examples of the latter include Japanese Patent Laid-Open No. 05-45179 (Reference 2) and Japanese Patent Laid-Open No. 2002-357762. No. (Reference 3), Japanese Unexamined Patent Application Publication No. 2009-38321 (Reference 6), and the like.

  For example, in digital still cameras, etc., the stepping motor method has been the mainstream until now, but in recent years, in order to emphasize the avoidance of audio noise during movie shooting and the speeding up of autofocus, etc., in recent years, the piezo motor method and VCM (voice coil) The motor) method is used. The range of position detection required by such a method varies depending on application specifications, but high-end models of digital still cameras, single-lens reflex cameras, camcorders, surveillance cameras, etc. generally require long distance detection of 10 mm or more. Is done.

  In order to detect the position of a moving object (movable body) with the above-described piezo motor type or VCM type camera, a magnetic sensor is generally used as shown in Patent Document 4 below.

  FIG. 9 shows a configuration for position detection of a conventional digital still camera or the like. In this camera or the like, a lens barrel (lens barrel) 2 that holds a lens 1 is front and rear with respect to a main body 3 as shown in the figure. It is arranged to move forward and backward. A magnet (magnetic generating member) 4 is attached to the side surface of the lens tube 2 and a magnetic sensor (MR element or Hall element) 5 for detecting the magnetic field of the magnet 4 is disposed on the main body 3 side. By detecting and calculating a change in the magnetic field from the magnet 4 by the magnetic sensor 5, the position of the moving lens cylinder 2 (magnet 4) is detected.

Japanese Patent Laid-Open No. 04-9712 JP 05-45179 A JP 2002-357762 A JP 2006-292396 A JP 2006-173306 A JP 2009-38321 A

  By the way, in detecting the lens position of the digital still camera or the like, in order to accurately grasp and use the position of the moving object, it is important to accurately grasp the origin (reference) position. In position detection using a sensor, the origin position cannot be grasped. Therefore, in order to detect the origin position, in this example, both end positions of the lens movable range, as shown in FIG. 9, the reflection type photosensor 6a and the tip end portion are located at the base of the movable range of the lens tube 2 on the main body 3 side. A similar reflection type photosensor 6b is disposed. These reflection type photosensors 6a and 6b can detect the rear end position of the lens tube 2. According to the photosensor 6b, the maximum extension position (advance end) of the lens tube 2 in the state shown in FIG. 9B. The photo sensor 6a detects the origin (reference) position (storage end) of the lens barrel 2 in the state shown in FIG. 9C. In addition, as said reflection type photo sensor, there exist some which are shown by Unexamined-Japanese-Patent No. 2006-173306 (reference 5) and Unexamined-Japanese-Patent No. 2009-38321 (reference 6).

  However, in order to detect a specific position such as the origin position in addition to the magnet 4 and the magnetic sensor 5 for position detection, the arrangement of the position detection becomes complicated because the photosensors 6a and 6b are arranged. There is a problem of high costs. In addition, when using a magnetic sensor, it is difficult to improve the linearity of the signal because of the magnetic field detection, and there is a problem that malfunction occurs due to the influence of magnetic fogging.

  The present invention has been made in view of the above-described problems, and the object thereof is position detection using a reflective photosensor that can achieve detection of a specific position such as an origin position at a low cost with a simple configuration. To provide an apparatus.

  In order to achieve the above object, a position detection apparatus using a reflective photosensor according to the first aspect of the invention arranges reflective surfaces and non-reflective surfaces alternately in the moving direction of the moving object, And a light-emitting element and a light-receiving element that emit / receive light to / from the reflection part, and each light-receiving element has a moving direction of the reflection part. A reflection type photosensor provided with a plurality of light receiving portions having different light receiving areas, and outputs signals having different phase differences from the plurality of light receiving portions, and detects the position of the moving object from these output signals. In addition, the specific position is detected by the specific pattern.

  Invention of Claim 2 makes the said specific pattern only a reflective surface or only a non-reflective surface, outputs two signals with a 90-degree phase difference from said several light-receiving part, and this output is made into A and B, By performing the calculation of (A−B) / (A + B) and (A + B) / (A−B), the position of the moving object is detected, and two signals having a phase difference of 180 degrees from the plurality of light receiving units are detected. When the signal is output and the outputs are A and C, the midpoint potential is obtained by performing the calculation of (A + C) / 2, and the determination level (threshold value) set in advance with reference to the midpoint potential is set to the above. When the output of the light receiving unit exceeds or falls, the presence of the specific position is detected.

  According to the configuration of the first aspect, for example, a reflecting part (plate) in which a reflecting surface and a non-reflecting surface are alternately formed is attached to a moving object such as a movable lens of a camera, and the state of light reflection from the reflecting part is set. By receiving light at a plurality of (for example, three) light receiving portions (each having a different light receiving area), a plurality of signals having different phase differences are output, and the position and amount of movement of the moving object are detected from the plurality of signals. Can do. In addition, the reflection part has a unique pattern formed on one end, both ends, the center, etc., and by receiving the reflected light from this unique pattern, a specific position of the reflection part, that is, one end The position of the part (origin), both ends (end point, wide angle end, telephoto end), center point, etc. are detected.

  According to the configuration of the second aspect, for example, three signals (outputs A to C) are output by the light receiving element divided into three, and the calculation for detecting the moving position by the signal outputs A and B having a phase difference of 90 degrees ( Linear value calculation) is performed, and the midpoint (center) potential is calculated from the signal outputs A and C having a phase difference of 180 degrees. That is, the midpoint potential is obtained at the same time as the detection. Then, a predetermined determination level (threshold value) is set from this midpoint potential, and when the output (value) of the light receiving unit exceeds or falls below this determination level, the specific position is detected, and the temperature Even when the output signal fluctuates due to a change or the like, the position and amount of movement of the moving object can be accurately detected with the midpoint voltage kept constant.

According to the position detection device of the present invention, detection of a specific position such as the origin can be achieved with a simple configuration at low cost, and a photo added for detection of the origin position or the like in the conventional position detection device. There is an advantage that a sensor or the like becomes unnecessary.
Further, even when there is an application where it is desired to separate the position detection distance into a plurality of positions, it is possible to detect a desired position by providing a specific pattern at an arbitrary location on the reflector.

  Moreover, the disadvantages of using a conventional magnetic sensor are eliminated. That is, it is not affected by magnetic fog, etc., and it is not necessary to amplify the detection output by an operational amplifier, and a detection error occurs due to variations in magnetization of the S pole and N pole in the magnet and uneven magnetic field strength, There is also an advantage that the performance is prevented from being deteriorated due to the oxidation.

  According to the configuration of the second aspect, since the midpoint potential can be kept constant, the photosensor has temperature dependence or the output signal from the photosensor varies due to temperature change. Even if the midpoint voltage level changes, the result (linear characteristic) obtained from the arithmetic expression is not affected, and long-range position detection can be performed satisfactorily. In addition, there is also an effect that the midpoint potential for obtaining the linear characteristics can be taken out at the same time during detection.

The structure of the position detection apparatus using the reflective photosensor which concerns on 1st Example of this invention is shown, A figure (A) is a block diagram of the 1st example of a reflection part (reflector) mainly, A figure (B) is It is a general view of a detection arithmetic circuit including a reflective photosensor. It is a figure which shows the output waveform from the light receiving element of 1st Example. 1 shows a configuration when the position detection device of the first embodiment is applied to a lens module for a camera, where FIG. (A) is a diagram during normal operation, and FIG. (B) is a diagram when the lens barrel is moved to the tip. FIG. 4C is a view when the lens barrel is moved to the rear end, and FIG. 4D is an enlarged view of the detection portion of the D portion in FIG. It is a figure which shows the structure [Figure (A)] of the 2nd example of the reflecting plate in an Example, and the output waveform [Figure (B)] from the light receiving element at that time. It is a figure which shows the structure [figure (A)] of the 3rd example of the reflecting plate in an Example, and the output waveform [figure (B)] from the light receiving element at that time. It is a figure which shows the structure of the position detection apparatus (detection arithmetic circuit) of 2nd Example. It is a wave form diagram which shows the calculated value of the sensor position (movement position) in 1st, 2nd Example. It is a figure which shows the midpoint electric potential and determination level which are calculated in the 1st, 2nd Example. It is a figure which shows a structure when the position detection apparatus using the conventional magnetic sensor is applied to the lens module for cameras.

FIGS. 1 to 3 show the configuration of a position detection apparatus using a reflective photosensor according to a first embodiment of the present invention (applied to a lens driving unit of a digital still camera). As shown in FIG. 1A, a reflecting plate (optical reflecting portion) 10 and a reflective photosensor 12 that emits light to the reflecting plate 10 and receives the reflected light are provided. The reflection plate 10 is formed with a stripe pattern in which, for example, a reflective surface (mirror surface) sa and a non-reflective surface sb having an extremely thin strip shape of about several hundred μm are arranged alternately (in a vertical stripe shape). In the embodiment, a wide reflection surface T _sa having a width wider than the width of the reflection surface _sa is provided as a unique pattern at both ends of the reflection plate 10, and the reflection due to the presence of the wide reflection surface T _sa is reflected. The end position (end point) of the plate 10, that is, the moving object (movable body) is detected. Note that the non-reflective surface sb may be formed of a slit space.

  As shown in FIG. 1B, the reflective photosensor 12 includes a light-emitting element 13 and a light-receiving element 14 having three light-receiving portions 14a, 14b, and 14c. The reflector 10 is arranged on the side so as to move in a direction 100 that is parallel to the light emitting / receiving surface and substantially perpendicular to the arrangement direction of the light emitting elements 13 and the light receiving elements 14 (vertical direction in the figure). The reflecting plate 10 is attached so as to move integrally with a moving object (movable body) such as a lens tube. That is, the light receiving portions 14a to 14c of the light receiving element 14 are obtained by dividing the light receiving area so as to be different areas in the moving direction 100, and the widths of the reflecting surface sa and the non-reflecting surface sb of the reflecting plate 10. By adjusting the size, shape, and arrangement of the three light receiving portions 14a to 14c, the three outputs from the photosensor 12 are designed to be shifted in a desired phase. In the embodiment, for example, assuming that the output A from the light receiving unit 14a is a reference (0 degree), the output B from the light receiving unit 14b is 90 degrees, and the output C from the light receiving unit 14c is advanced by 180 degrees. Designed to be

  A detection control circuit (LSI) 15 to which the light receiving element 14 is connected has buffer amplifiers 16a to 16c that receive outputs from the three light receiving units 14a to 14c, and analog / digital conversion of outputs from the amplifiers 16a to 16c. A / D converter 17 that performs, a processor (arithmetic circuit) 18 that obtains a moving position by performing calculations for linear detection based on the output of the A / D converter 17, and offset correction output from the processor 18 A D / A converter 19 and an actuator driver 20 are provided for digital-analog conversion of signals and control signals. The actuator driver 20 outputs a drive signal to an actuator 21 for driving a lens cylinder in a camera or the like. The D / A converter 19 supplies an offset correction signal for correcting the amplitudes and reference levels of the outputs A to C to the buffer amplifiers 16a to 16c.

  FIG. 3 shows a configuration applied to a lens module for a digital still camera or the like. In the embodiment, a reflector 10 is provided on the side of the lens tube 2 that holds the lens 1, and the lens tube 2 is A reflective photosensor 12 is attached to the side of the main body 3 that can move back and forth.

  The first embodiment has the above-described configuration. In the embodiment, the light receiving element 14 is changed to 3 by periodically reflecting light from the reflecting surface sa based on the light emission from the light emitting element 13 of the reflective photosensor 12. Outputs A, B, and C are obtained by the divided light receiving portions 14a to 14c. As shown in FIG. 2, the outputs A, B, and C are sine wave (sin) or cosine wave (cos) signals, and the output B is 90 degrees out of phase with respect to the output A. On the other hand, the output C has a phase angle shifted by 90 degrees.

  The signals of the outputs A to C are supplied to the processor 18 via the buffer amplifiers 16a to 16c and the A / D converter 17, and the processor 18 detects, calculates, and determines the end point (origin, etc.) and the moving position. Is done. For example, as shown in FIG. 2, when the potential determination level (threshold value) is set to Ea, when both the outputs A and C (B and C may be used) exceed this Ea level [High When the level is reached], the end points at both ends of the reflecting plate 10, that is, the start point and end point of the moving operation are determined. In the case of the configuration of FIG. 3, as shown in FIG. 3B, the lens barrel 2 is extended to the maximum position (for example, the telephoto end) or as shown in FIG. A position (for example, the wide-angle end) in a state where is returned to the origin (reference) position is detected.

  Although details will be described later, on the basis of the signals of outputs A and B, the processor 18 performs calculations for position detection and the like, thereby detecting the movement positions of the reflecting plate 10 and the lens barrel 2. . Then, the processor 18 supplies a control signal for driving the lens cylinder 2 to the actuator driver 20 based on the detected end point signal and movement position signal, so that the actuator 21 drives the lens cylinder 2. The

FIG. 4 shows the configuration and output waveform when the second example of the reflector is used. As shown in FIG. 4A, in this example, the reflection surface sa and the non-reflection surface sb are shown. The arrangement positions are opposite to those in FIG. 1, and a wide non-reflective surface T _sb having a width wider than the width of the non-reflective surface _sb is provided as a unique pattern at both ends of the reflector 24.

  According to the reflector 24 of the second example, the outputs A to C from the light receiving portions 14a to 14c of the reflective photosensor 12 are as shown in FIG. 4B, and the determination level is set to Eb. In this case, for example, when any two signals of A, B, and C fall below this Eb level [when it becomes a low level], the end points at both ends of the reflector 24 (the start point of the movement operation) End point) is determined.

FIG. 5 shows a configuration and an output waveform when the third example of the reflector is used. As shown in FIG. 5A, in this example, the center of the reflector 26 is used as a unique pattern. A wide reflection surface C _sa having a width wider than that of the reflection surface _sa is provided in the part. The reflecting surface sa and the non-reflecting surface sb of the reflecting plate 26 may be reversed, and a wide non-reflecting surface having a width wider than the width of the non-reflecting surface sb may be provided at the center.

  According to the reflector 26 of the third example, the outputs A to C from the light receiving portions 14a to 14c of the reflective photosensor 12 are as shown in FIG. 5B, and the signal level is maximum at the center. The detection area of the state that becomes will appear. In this case, for example, when any two signals of A, B, and C exceed the determination level Ec (when the signal becomes high level), the center point of the reflector 26 (the center point of the movement range) is determined. Is done. When a wide non-reflective surface is provided at the center, a detection region in which the signal level is minimum appears at the center.

  In the third example of the reflecting plate, not only the center point of the reflecting plate 26 (or moving object) but also a specific point set arbitrarily can be detected, and the position detection distances are separated into a plurality. The present invention can be applied to the case where the separation point is detected or the case where two drive systems are connected to a single moving object and the switching point of the two drive systems is detected.

FIG. 6 shows the circuit configuration of the position detection device of the second embodiment. This second embodiment is a configuration for detecting an end point (the reflectors of the first and second examples). The detection speed is made faster than that of the configuration of FIG.
As shown in FIG. 6, a comparator 31 for inputting the output A from the light receiving unit 14a, a comparator 32 for inputting the output C from the light receiving unit 14c, an AND circuit 33, and an end point control circuit (or shutdown circuit) 34 are provided. At the same time, the processor 35 outputs the determination (reference) level signals of the comparators 31 and 32 via the D / A converter 19.

  According to the second embodiment, the comparators 31 and 32 determine whether or not the outputs A and C are equal to or higher than the determination level. Both the outputs A and C are equal to or higher than the determination level. By outputting, it is detected that the reflectors 10 and 24 (moving objects such as the lens barrel 2) are at the end points. This end point detection signal is supplied to an end point control circuit (or shutdown circuit) 34, and actuator control of the lens barrel 2 and the like is performed based on the end point. Further, when 34 is a shutdown circuit, this end point signal can be used as a trigger signal for a fail-safe system, thereby performing power control, abnormality display, and the like.

  According to such a detection process, there is an advantage that the time required for detection / determination is increased because it does not depend on a control circuit composed of an LSI as shown in FIG. The configuration of the second embodiment can also be applied to the case where the center point is detected using the reflection plate 26.

  1 and 6, the processors 18 and 35 perform calculation for position detection. As this calculation, outputs (values) having a phase difference of 90 degrees output from the two light receiving units 14a and 14b. Using A and B, as shown in FIG. 7, (A−B) / (A + B) and (A + B) / (A−B) are calculated.

  FIG. 7 shows the calculated values of the sensor positions (movement positions) in the first and second embodiments. In the processors 18 and 35, (A−B) / (A + B) [= b] and ( By performing the calculation of (A + B) / (A−B) [= a], as shown in FIG. 7, a triangular waveform is obtained that repeats the upward inclined portion a and the downward inclined portion b with respect to the reflector coordinates. This calculation makes it possible to detect the moving position while improving the linearity of the detection output of the photosensor 12.

  According to the above arithmetic expression, the temperature characteristics of the reflective photosensor 12 can be completely canceled. For example, when there is no influence of temperature and A = 0.4 (V) and B = 0.1 (V), the value according to the above equation (A−B) / (A + B) is 0.6. On the other hand, if there is a 10% fluctuation due to the temperature, A = 0.44 and B = 0.11. In this case as well, the calculated value is 0.6, and the fluctuation is cancelled. Therefore, there is no need to provide a circuit for monitoring the internal temperature of the apparatus with a thermistor for feedback and a special temperature characteristic cancel circuit.

  In the first and second embodiments, the midpoint potential is calculated by (A + C) / 2 based on the outputs (values) A and C having a phase difference of 180 degrees as shown in FIG. The potential (voltage) is corrected. That is, in the above position detection calculation, calculation processing based on the midpoint potential of the output signal from the light receiving element 14 is required, but the level of the midpoint potential changes due to the temperature dependence of the reflective photosensor 12. In such a case, the linearity of the calculation result is lost. Therefore, in the embodiment, the sensor position and the specific position are reliably detected by obtaining the midpoint potential from the outputs A and C and correcting each midpoint potential.

  FIG. 8 shows the midpoint potential and the determination level (threshold) corresponding to the reflector 10 of the first example and the reflector 26 of the third example (only A is displayed for output). Thus, when the midpoint potential is calculated by (A + C) / 2, the midpoint potential of the outputs A to C (reference point) is corrected to match the midpoint potential, and the calculated midpoint Determination levels (midpoint potential + predetermined predetermined potential) Ea, Ec are set based on the potential. In the case of the reflecting plate 10, when the outputs A to C (at least one of them) exceed the determination level Ea, it is determined that the end point is at both ends. In the case of the reflecting plate 26, the moving range is determined. The center point of is detected. In the case of the reflector 24 of the second example, a determination level (middle point potential−predetermined predetermined potential) Eb is set based on the calculated midpoint potential, and when the determination level Eb falls below the determination level Eb, End points at both ends are detected.

  The present invention can be applied to a long-distance detection actuator such as a digital still camera, a single-lens reflex camera, a camcorder, or a CCTV that requires high-magnification zoom as a position detection device that performs long-distance detection with high resolution.

2 ... lens tube, 6a, 6b, 12 ... reflection type photo sensor,
10, 24, 26 ... reflector (reflector),
13 ... Light emitting element, 14 ... Light receiving element,
14a to 14c ... light receiving part, 15 ... detection control circuit (LSI),
16a to 16c: buffer amplifier,
18, 35 ... processor, 31, 32 ... comparator,
33 ... AND circuit, 34 ... End point control circuit,
sa ... reflective surface, sb ... non-reflective surface,
T _sa , C _sa ... Wide reflecting surface, T _sb ... Wide non-reflecting surface.

Claims (2)

The reflective part and the non-reflective surface are alternately arranged in the moving direction of the moving object, and the reflective part having a unique pattern that changes specifically with respect to the alternating pattern,
A reflective photosensor having a light-emitting element and a light-receiving element that emits / receives light with respect to the reflection part, and the light-receiving element includes a plurality of light-receiving parts each having a different light-receiving region in the moving direction of the reflection part; With
A reflection type photosensor that outputs signals having different phase differences from the plurality of light receiving units, detects a position of the moving object from these output signals, and detects a specific position by the specific pattern is used. The position detection device. The unique pattern is only a reflective surface or only a non-reflective surface,
When two signals having a phase difference of 90 degrees are output from the plurality of light receiving units and the outputs are A and B, the calculation of (A−B) / (A + B) and (A + B) / (A−B) is performed. By performing the position detection of the moving object,
Two signals having a phase difference of 180 degrees are output from the plurality of light receiving units, and when these outputs are A and C, a midpoint potential is obtained by performing (A + C) / 2,
2. The reflective photosensor according to claim 1, wherein when the output of the light receiving unit exceeds or falls below a predetermined determination level with reference to the midpoint potential, the reflection photosensor is detected at the specific position. The position detector used.

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