JP4521260B2 - Absolute position detector - Google Patents

Description

  The present invention relates to an absolute position detection device, and more particularly to an absolute position detection device capable of detecting an absolute position on a straight line.

  Conventionally, for example, an absolute linear encoder is known as an absolute position detection device that detects an absolute position on a straight line. As shown in FIG. 8, this absolute type linear encoder has a serial absolute scale 1200 on which an absolute code (ABS code) 1205 representing position information of a predetermined word length is recorded in the X direction, and a scale 1200 facing each other. The ABS code detector 101 that detects the transmitted light that is transmitted through the metal vapor deposition film portion 1205a or the non-vapor deposition portion 1205b of the absolute code 1205 on the scale 1200, and the transmitted light detected by the ABS code detector 101 is bright and dark. Conversion circuit 104 for converting to binary information in response to this, a shift register 103 for storing binary information from the output of the conversion circuit 104, and a computer for processing based on the binary information stored in the shift register 103 (FIG. And a slider (not shown) ) Is stationary relative to the scale 1200, the ABS code detector 101 is displaced by a distance corresponding to a predetermined word length along the X direction together with the detection head 100 to detect binary information. The binary information detected by the ABS code detector 101 is sequentially stored in the shift register 103 via the conversion circuit 104, and the ABS code detector 101 is based on the binary information (position information) stored in the shift register 103. Has been proposed in which the initial position of the slider is detected by subtracting the displacement amount from the initial position of the slider movement (see Patent Document 1).

JP 2002-168655 A (pages 4 to 5, FIGS. 1 to 4)

  In the prior art, when obtaining the absolute position on the straight line, the binary information array stored in the shift register 103 is converted into a serial absolute signal representing the position information, and the computer is initialized based on the converted serial absolute signal. An operation for obtaining the position must be performed, or the ABS code 1205 must be recorded on the scale 1200. Therefore, even if the configuration of the prior art is applied to the absolute position on the straight line of the moving body, for example, the absolute position on the straight line of the focusing lens used in the autofocus mechanism of the surveying instrument, It is not sufficient for obtaining the position at high speed or increasing the resolution of the position information.

  The present invention has been made in view of the above-described conventional problems, and an object thereof is to obtain an absolute position on a straight line with high resolution and at high speed.

In order to achieve the object, a plurality of photoelectric conversion elements are linearly arranged at equal intervals, and a signal accompanying photoelectric conversion of each photoelectric conversion element in response to a shift clock generated corresponding to each photoelectric conversion element A linear image sensor that sequentially outputs electrical signals according to electric charge; and the linear image sensor disposed opposite to the linear image sensor and arranged to be relatively movable along an arrangement direction of the plurality of photoelectric conversion elements. A light source that emits light toward one of the photoelectric conversion elements of the sensor, a collimator lens disposed between the light source and the linear image sensor, and disposed between the collimator lens and the linear image sensor. A light branching means for branching the light generated from the light source into a plurality of lights, and outputting the outputs of the plurality of photoelectric conversion elements to the linear image A comparator that sequentially captures the first photoelectric conversion elements on the sensor in accordance with the arrangement order and compares them with the determination level, and monitors the comparison result of the comparator, and the output of any one of the photoelectric conversion elements is the determination level. Rising edge detecting means for detecting that the output exceeds one of the above, and a falling edge detecting means for monitoring the comparison result of the comparator and detecting that the output of any one of the photoelectric conversion elements is below the determination level And a first storage means for counting the number of shift clocks in response to the shift clock and storing the count value every time a detection output is generated from the rising edge detection means, and in response to the shift clock. A second storage means for counting the number of shift clocks and storing the count value every time a detection output is generated from the falling edge detection means; Based on the plurality of count values stored in the storage means and the plurality of count values stored in the second storage means, the irradiation position of the light on the linear image sensor is referred to the first photoelectric conversion element. And a position detecting means for detecting as described above.

  (Operation) When light is emitted from a light source toward a linear image sensor in which a plurality of photoelectric conversion elements are linearly arranged at equal intervals, the output of each photoelectric conversion element is synchronized with a shift clock on the linear image sensor. Are taken in order from the first photoelectric conversion element according to the arrangement order and compared with the determination level, the number of shift clocks is counted, and the count value of the number of shift clocks is stored each time a detection output is generated from the rising edge detection means. At the same time, each time a detection output is generated from the falling edge detection output, it is stored, and the irradiation position of light on the linear image sensor based on each stored count value is on a straight line with the first photoelectric conversion element as a reference. Since it is detected as an absolute position, the light irradiation position on the linear image sensor is made an absolute position on a straight line by simple calculation. It is possible to determine the speed, when the abnormality in the detection value occurs, dust between the light source and the linear image sensor can be determined to be present. Moreover, since the resolution of the light irradiation position increases in proportion to the number of photoelectric conversion elements, the resolution related to the light irradiation position can be increased by increasing the number of photoelectric conversion elements.

As shown in FIG. 1C, when there are two slits as the light branching means, the number of shift clocks when the output of the photoelectric conversion element first exceeds the determination level is C1, and the output of the photoelectric conversion element After the first exceeds the judgment level, the number of shift clocks when the level falls below the judgment level is C2, and the number of shift clocks when the output of the photoelectric conversion element second exceeds the judgment level is C3. When the number of shift clocks when the output of the element exceeds the determination level for the second time and then becomes equal to or less than the determination level is C4, and the element interval of each photoelectric conversion element is P, the first photoelectric on the linear image sensor. The first rising edge position with respect to the conversion element (the distance from the reference position when the output of the photoelectric conversion element first exceeds the determination level) L1 is obtained as L1 = C1 × P. The first falling edge position with respect to the first photoelectric conversion element on the image sensor (from the reference position when the output of the photoelectric conversion element first exceeds the determination level and then falls below the determination level) The distance (L2) is obtained as L2 = C2 × P, and the second rising edge position with the first photoelectric conversion element on the linear image sensor as a reference (the output of the photoelectric conversion element has exceeded the determination level second) (Distance from the reference position) L3 is obtained as L3 = C3 × P, and the second falling edge position (the output of the photoelectric conversion element is 2 based on the first photoelectric conversion element on the linear image sensor) The distance from the reference position (L4) when L4 exceeds the determination level and then falls below the determination level) is determined as L4 = C4 × P, and the center position of the light irradiated on the linear image sensor The device Psn is obtained as Psn = (L1 + L2 + L3 + L4) / 4.

As is apparent from the above description , according to the invention of claim 1, the light irradiation position can be obtained at high speed as an absolute position on a straight line with a simple calculation, and according to the number of photoelectric conversion elements. The resolution can be increased. In particular, the output of each photoelectric conversion element and the determination level can be compared more accurately, and the absolute position detection accuracy can be increased. Furthermore, when an abnormality occurs in the detection value, it can be determined that dust or the like exists between the light source and the linear image sensor.

  Next, embodiments of the present invention will be described based on examples. FIG. 1A is a schematic configuration diagram of an absolute position detection device showing an embodiment of the present invention, and FIG. 1B shows a slit plate having one slit disposed between a light source and a linear image sensor. 1C is a side view when a slit plate having two slits is arranged between the light source and the linear image sensor, and FIG. 2 is a block diagram of the absolute position detection device shown in FIG. FIG. 3 is a waveform diagram for explaining the operation of the absolute position detecting device shown in FIG.

  In these drawings, the absolute position detection device includes a base 10 formed in a rectangular shape as, for example, an absolute linear encoder, and a linear image sensor (line sensor) 12 is fixed to the base 10. The linear image sensor 12 includes a semiconductor element such as a charge coupled device (CCD) or a complementary metal oxide semiconductor (CMOS), and a plurality of photoelectric conversion elements S1 to Sn among these semiconductor elements include, for example, 5,000 to 10,000 are linearly arranged at equal intervals (for example, 7 μm pitch).

  On the other hand, a moving body 14 is disposed opposite to the linear image sensor 12, and a light source 16 is fixed at a substantially central portion of the front surface of the moving body 14 (surface facing the linear image sensor 12). The moving body 14 is arranged in parallel with the base 10 and can be reciprocated linearly along the arrangement direction of the photoelectric conversion elements (Si) by driving means such as a motor or a link mechanism (not shown). Has been. Light is irradiated from the light source 16 to the linear image sensor 12 through the collimator lens 17.

  When light from the light source 16 is irradiated to any one of the photoelectric conversion elements (Si) of the linear image sensor 12 via the collimator lens 17, a clock driver is used to detect the light irradiation position as an absolute position on a straight line. A shift pulse SP is output from the linear image sensor 12 to the linear image sensor 12 and the CPU (microprocessor) 20 every frame, for example, every 1 ms. In the meantime, the shift clock SC is sequentially output at regular intervals corresponding to each photoelectric conversion element. The shift pulse SP is used as a timing signal that prescribes the start or end of reading of data to the CPU 20, and after the shift pulse SP is generated, when the shift clock SC is sequentially input to the linear image sensor 12, From the image sensor 12, in response to the rise or fall of the shift clock SC, an electric signal corresponding to the signal charge accompanying the photoelectric conversion of each photoelectric conversion element is sequentially amplified from the first photoelectric conversion element S1 according to the arrangement order. 22 is output. The amplifier 22 sequentially amplifies the electric signal output from the linear image sensor 12 and outputs the amplified signal to the comparator 24. The comparator 24 sequentially takes in an electric signal from the output of the amplifier 22 and compares it with a determination level (edge determination level voltage) 26, and outputs each comparison result to the rising edge detection circuit 28 and the falling edge detection circuit 30. It has become.

  The rising edge detection circuit 28 monitors the comparison result of the comparator 24. When the output of the amplifier 22 exceeds the determination level 26, the rising edge detection circuit 28 determines that the output of any one of the photoelectric conversion elements has exceeded the determination level 26. The rising edge detection means is configured to output an edge detection output to the counter value latch circuit 32. On the other hand, the falling edge detection circuit 30 monitors the comparison result of the comparator 24, and when the output of the amplifier 22 falls below the judgment level 26, the output of any one of the photoelectric conversion elements falls below the judgment level 26. The falling edge detection means for outputting the falling edge detection output to the counter value latch circuit 34 is configured.

  The counter value latch circuit 32 counts the shift clock SC in response to the rise and fall of the shift clock SC, and stores this count value (counter value) in response to the rising edge detection output from the rising edge detection circuit 28. The stored count value is output to the adder circuit 36 as first recording means. For example, as shown in FIG. 3, the counter value latch circuit 32 latches the count value (number of shift clocks) C1 at the timing t1 when the rising edge detection output is generated from the rising edge detection circuit 28 at the timing t1, The latched count value (number of shift clocks) C1 is output to the adder circuit 36. The counter value latch circuit 34 counts the shift clock SC in response to the rise and fall of the shift clock SC, and responds to the count value (counter value) in response to the falling edge detection output from the falling edge detection circuit 30. And a second recording means for outputting the latched count value to the adding circuit 36. For example, as shown in FIG. 3, the counter value latch circuit 34 obtains the count value (the number of shift clocks) C2 at the timing t2 when the falling edge detection output is generated from the falling edge detection circuit 30 at the timing t2. The latched count value (the number of shift clocks) C2 is output to the adder circuit 36.

  The addition circuit 36 adds the count value (shift clock number) C1 latched by the counter value latch circuit 34 and the count value (shift clock number) C2 latched by the counter value latch circuit 34, and bit-shifts the addition value. The signal is output to the circuit 38. In the bit shift circuit 38, an operation for dividing the added value by 2 is performed, and data based on the calculated value is used as data relating to the light irradiation position on the linear image sensor 12, that is, data relating to the center position Psn of the light spot. The data is output to the CPU 20. In the CPU 20, the light irradiation position on the linear image sensor 12 is calculated as an absolute position on a straight line based on data from the bit shift circuit 38.

  Specifically, the shift clock SC is sequentially output corresponding to the first photoelectric conversion element S1 to the nth photoelectric conversion element Sn, and the number of shift clocks C1 latched in the counter value latch circuits 32 and 34, C2 corresponds to the number of elements based on the first photoelectric conversion element S1. Therefore, the CPU 20 sets the number of shift clocks C1 when the output of the amplifier 22 exceeds the determination level 26, that is, when the light spot light quantity distribution characteristic rises, and the output of the amplifier 22 becomes the determination level 26 or less. In other words, the number of shift clocks when the light spot light quantity distribution characteristic falls is C2, the dimension of the element spacing of the photoelectric conversion elements is P, and the rising edge from the first photoelectric conversion element S1 on the linear image sensor 12 The position (distance from the reference position) L1 is calculated as L1 = C1 × P, and the falling edge position (distance from the reference position) L2 from the first photoelectric conversion element S1 on the linear image sensor 12 is calculated as L2. = C2 × P, and the light irradiation position on the linear image sensor 12, that is, the center position Psn of the light spot is expressed as Psn = (L1 + L2) / 2 is calculated.

  In this case, the adder circuit 36, the bit shift circuit 38, and the CPU 20 change the center position Psn of the light spot, which is the light irradiation position on the linear image sensor 12, based on the shift clock numbers C1 and C2 to the first photoelectric conversion element S1. It is configured as position detecting means for detecting as a reference. Further, the rising edge detection circuit 28, the falling edge detection circuit 30, and the counter value latch circuits 32 and 34 monitor the comparison result of the comparator 24 in association with each photoelectric conversion element, and the plurality of photoelectric conversion elements S1 to Sn are monitored. Among them, the photoelectric conversion element specifying means for specifying the photoelectric conversion element whose output first exceeds the determination level 26 and the photoelectric conversion element whose output first falls below the determination level 26 after exceeding the determination level 26 is configured. become.

  In the present embodiment, a linear image sensor 12 having a plurality of photoelectric conversion elements arranged at intervals of several micrometers is used, and light from the light source 16 is directed to each photoelectric conversion element via a collimator lens 17. The linear image sensor 12 outputs an electrical signal corresponding to the brightness, determines whether the level of the electrical signal exceeds the determination level 26, and based on the determination result, the rising edge position and the rising edge position of the light spot. Since the down edge position is calculated and the center position of the light spot is calculated from the calculation result, the center position of the light spot can be obtained as an absolute position on the linear image sensor 12 by a simple calculation. This can contribute to higher resolution.

In the above description , the light source 16 that merely forms a light spot has been described. As a device for sharpening the edge of the light amount distribution of the light spot, for example, a collimator lens between the collimator lens 17 and the linear image sensor 12 is used. in front of 17, the Lupi Nhoru or slits be emitted by limiting a light flux of light generated from the light source 16 may be provided one or more than one. For example, as shown in FIG. 1 (b), to indicate when Ru slits plate 19 having a slit SL1, the level of the electric signal output from the linear image sensor 12 is a steep characteristic with respect to changes in luminance, Edge determination can be performed more accurately, and an accurate position on a straight line can be obtained.

In this embodiment, as a light branching means for splitting the light from the light source 16 into a plurality of lights between the collimator lens 17 and the linear image sensor 12, for example, as shown in FIG. The slit plate 21 that takes in the light from the light source 16 through the collimator lens 17 and splits it into two lights along the arrangement direction of the photoelectric conversion elements is arranged to form two light spots on the linear image sensor 12. Adopt the configuration to do .

  In this case, as the two light beams are irradiated onto the linear image sensor 12, the linear image sensor 12 outputs two pulses (first pulse and first pulse) corresponding to the interval between the slits SL1 and SL2 of the slit plate 21. As a counter value latch circuit that latches the number of shift clocks in response to the rise and fall of each pulse, the second pulse is output in response to the rising and falling edges of the first pulse, respectively. A latch circuit that latches the number of shift clocks is provided, and a latch circuit that latches the number of shift clocks in response to the rising edge and falling edge of the second pulse is provided, and the center of the light spot obtained from the first pulse By calculating an average value of both from the position and the center position of the light spot obtained from the second pulse, the entire light spot is obtained. It is possible to obtain the center position of the.

  Specifically, the CPU 20 sets the number of shift clocks C1 when the output (first pulse) of the amplifier 22 first exceeds the determination level 26 (when the light spot light quantity distribution characteristic first rises), and thereafter When the output of the amplifier 22 falls below the determination level 26 (when the light spot light quantity distribution characteristic falls), the shift clock number is C2, and then the output (second pulse) of the amplifier 22 is the second. When the judgment level 26 is exceeded (when the light spot light quantity distribution characteristic rises second), the number of shift clocks is C3, and then when the output of the amplifier 22 falls below the judgment level 26 (light spot light quantity distribution characteristic). The number of shift clocks at the time of the second falling) is C4, the dimension of the element spacing of the photoelectric conversion elements is P, and the first photoelectric conversion element S1 on the linear image sensor 12 The first rising edge position (distance from the reference position) L1 is calculated as L1 = C1 × P, and the first falling edge position from the first photoelectric conversion element S1 on the linear image sensor 12 ( (Distance from the reference position) L2 is calculated as L2 = C2 × P, and the second rising edge position (distance from the reference position) L3 from the first photoelectric conversion element S1 on the linear image sensor 12 is calculated as L3 = C3 × P, the second falling edge position (distance from the reference position) L4 from the first photoelectric conversion element S1 on the linear image sensor 12 is calculated as L4 = C4 × P, and linear The light irradiation position on the image sensor 12, that is, the center position Psn of the light spot as a whole, is expressed as Psn = {(L1 + L2) / 2 + (L3 + L4) / 2} / 2 = (L1 + L2 + L3 + L ) / 4 is adapted to calculate a.

  In this case, since the center position of the light spot is obtained by two pulses, the absolute position can be obtained with higher accuracy than when the center position of the light spot is obtained from a single pulse. Further, when an abnormality occurs in the detected value, for example, when the center position of the light spot by one pulse cannot be obtained, an error that dust or the like exists between the light source 16 and the linear image sensor 12 is caused. Detection can also be performed.

  In this embodiment, the counter value latch circuits 32 and 34, the adder circuit 36, and the bit shift circuit 38 are configured by hardware. However, these are configured by a microcomputer having a counter function of an external clock. You can also.

  In this embodiment, the light source 16 is moved. However, a configuration in which the light source 16 is fixed and the linear image sensor 12 is reciprocated along the arrangement direction of the photoelectric conversion elements may be employed. That is, the center position of the light spot can be obtained as the absolute position on the linear image sensor 12 by relatively moving the light source 16 and the linear image sensor 12.

  Next, an embodiment when the absolute position detection apparatus according to the present invention is applied to a surveying instrument, for example, an electronic level autofocus mechanism will be described. FIG. 4 is a longitudinal sectional view of the electronic level autofocus mechanism, and FIG. 5 is a block diagram of the electronic level.

  In these drawings, an electronic level 50 includes a telescope 52 as a surveying instrument equipped with an absolute position detection device. An objective lens 56 and a focusing lens 58 are provided in a cylindrical telescope barrel 54. , An automatic correction mechanism 60, a beam splitter 62, a focusing screen 64, an eyepiece lens 66, and an autofocus detection light receiving sensor 68 are housed. The plate 64 is arranged linearly along the optical axis L. The light incident on the objective lens 56 enters the beam splitter 62 via the focusing lens 58 and the automatic correction mechanism 60, and the incident light is branched to the focusing screen 64 and the light receiving sensor 68. An image of the object collimated by the telescope 52 is formed on the focusing screen 64, and the image of the object can be confirmed through the eyepiece 66. That is, when the focusing lens 58 is disposed at a position where the focusing lens 58 is in focus, an image of the object when focused is formed on the focusing screen 64. A light receiving sensor 68 is arranged at a position conjugate with the focusing screen 64, and an image related to the object is detected by the light receiving sensor 68, and distance measurement is performed based on the detected image.

  The focusing lens 58 is disposed so as to reciprocate along a predetermined range along the optical axis L. The focusing lens 58 is fixed to the focusing lens frame 70. A rack 72 as a focusing lens drive transmission mechanism is fixed to the focusing lens frame 70, and a pinion (not shown) is connected to the rack 72. The pinion is connected to a manual focusing operation knob 76 via a shaft 74, and the shaft 74 is rotatably supported by a bearing 78. A clutch mechanism 80 is provided around the shaft 74, and the clutch mechanism 80 is connected to a drive motor 84 via a reduction gear mechanism 82. The reduction gear mechanism 82 is fixed to the telescope frame 54, and the driving force generated by the rotational drive of the drive motor 84 is transmitted to the shaft 74 via the reduction gear mechanism 82 and the clutch mechanism 80. That is, the shaft 74 and the clutch mechanism 80 are brought into contact with each other by a frictional force. When the drive motor 84 is driven to rotate forward or reversely, the shaft 74 rotates forward according to the driving force accompanying the rotational drive of the drive motor 84. Alternatively, when the rotation of the shaft 74 is reversed and the rotational motion of the shaft 74 is transmitted to the rack 72 via the pinion 79, the rack 72 moves linearly along the optical axis L. For this reason, the focusing lens 58 can be moved along the optical axis L by rotationally driving the drive motor 84. When the manual focusing operation knob 76 is rotated and this operating force is larger than the frictional force acting between the shaft 74 and the clutch mechanism 80, the manual focusing operation knob 76 is rotated to perform focusing. The lens 58 can be moved along the optical axis L. Further, the rotational speed of the drive motor 84 is detected by a rotational speed detector 86 constituted by, for example, an incremental encoder.

  On the other hand, in order to detect the relative positional relationship between the focusing lens 58 and the telescope barrel 54 as an absolute amount, the telescope barrel 54 has a long hole 88 having a length corresponding to the amount of movement of the focusing lens 58. The rod 90 connected to the focusing lens frame 70 is inserted into the elongated hole 88. The axial end of the rod 90 is fixed to the case 92, and the light source 16 is fixed in the case 92. For example, a light emitting diode is used as the light source 16. A slit 94 is formed on the front surface of the case 92, and light emitted from the light source 16 is irradiated onto the linear image sensor 12 through the slit 94. That is, the light source 16 is connected to a focusing lens 58 as a moving body, and reciprocates along the optical axis L as the focusing lens 58 moves. The linear image sensor 12 is sequentially irradiated with light according to the position of the focusing lens 58. The linear image sensor 12 is fixed to a case 96, and the case 96 is disposed so as to surround the periphery of the elongated hole 88 and is fixed to the telescope barrel 54. In this case, the effective length of the photoelectric conversion element on the linear image sensor 12 is set to a length that can cover the moving range of the light source 16, that is, the focusing range of the focusing lens 58.

  A drive motor 84 coupled to the telescope barrel 54 is connected to the CPU 20 via a drive motor control circuit 98, a rotation speed detector 86 is connected to the CPU 20, and a light receiving sensor 68 in the telescope barrel 54 is connected to the drive circuit 100. It is connected to the CPU 20 via the amplifier 102 and the A / D converter 104. A light source 16 is connected to the CPU 20 via a light source drive circuit 106, and a RAM 108 and a ROM 110 are connected as memories. Further, a display device 112 is connected to the CPU 20 and an input key 114 for inputting an instruction related to autofocus start / stop is connected.

  The CPU 20 performs a distance measurement calculation when the object is collimated based on the image data received by the light receiving sensor 68, displays the calculation result on the screen of the display device 112, and detects the rotation number detector 86. Based on the output, the drive amount and drive speed of the drive motor 84 are controlled via the drive motor control circuit 98, and the drive of the light source 16 is controlled via the light source drive circuit 106. Further, the CPU 20 calculates the data from the bit shift circuit 38 for each frame in response to the shift pulse SP generated from the clock driver 18 and calculates the current position of the focusing lens 58 on the optical axis L. It has become. Note that image data and data related to various calculation variables received by the light receiving sensor 68 are stored in the RAM 108, and various constants and programs necessary for autofocus control are stored in the ROM 110.

  Next, the electronic level autofocus operation will be described with reference to the flowchart of FIG. First, the telescope 52 is directed to the bar code measure of the measurement object with the approximate electronic level. When the start of the autofocus operation is instructed by the operation of the input key 114, the arithmetic processing by the CPU 20 is started, the shift pulse SP and the shift clock SC are output from the clock driver 18, and the light source 16 supplies the linear image sensor 12. Light is emitted toward the camera. Thereby, the CPU 20 acquires the current position of the focusing lens 58 based on the data from the bit shift circuit 38 (step S1). Next, in the CPU 20, the moving direction of the focusing lens 58 and the speed of the drive motor 84 are set based on the current position of the focusing lens 58 and predetermined setting conditions (step S2), and the drive motor 84 is driven according to this setting. Is started (step S3). When the drive motor 84 is driven forward or backward, the focusing lens 58 moves along the optical axis L along with this rotational drive. At this time, image data corresponding to the position of the focusing lens 58 is acquired by the light receiving sensor 68 (step S4), and surveying of the object is performed based on the acquired image data (step S5). For example, when collimating as a target a standard with a plurality of black marks printed on the surface of a white background at an equal pitch in the vertical direction, the pitch from the pitch of the pattern on the standard formed by the plurality of marks to the standard The distance is determined by the stadia survey method. Thereafter, it is determined whether or not the distance measurement is completed from the distance measurement result (step S6). When the distance measurement is not completed, that is, from the distance measurement result, the focusing lens 58 is not at the focus position. When the determination is made, the current position of the focusing lens 58 is acquired (step S7), and it is determined whether or not the search range has ended from the current position of the focusing lens 58 (step S8). That is, the current position of the focusing lens 58 is obtained, and it is determined whether or not the focusing lens 58 needs to be further moved. When the search range has not ended, the current position of the focusing lens 58 is obtained, the moving direction of the focusing lens 58 and the speed of the drive motor 84 are set (step S9), and the drive motor 84 is driven according to this setting. (Step S10), the process returns to Step S4, and the process proceeds to the process for acquiring the next image data.

  On the other hand, when it is determined in step S8 that the search range has ended, the drive of the drive motor 84 is stopped in order to stop the drive of the focus lens 58, assuming that the focus lens 58 has moved all within the movement range ( Step S11). At this time, the in-focus lens 58 is not in the in-focus position, that is, the in-focus state is not completed, and the processing in this routine is terminated.

  If it is determined in step S6 that the distance measurement is completed, the drive motor 84 is stopped to stop driving (moving) the focusing lens 58 (step S13). The in-focus lens position of the in-focus lens 58 is calculated (step S14), a process for positioning the in-focus lens 58 at the calculated position is performed (step S15), and the focusing operation is completed (step S16). . That is, since a calculation formula showing the relationship between the focusing lens position determined from the optical system of the telescope 52 and the distance to the object is set, when the distance measurement is completed, the distance measurement value is substituted into the calculation formula. By doing so, the focal lens position of the focusing lens 58 can be calculated from the distance measurement value. The focus lens 58 can be positioned at the focus position by rotating the drive motor 84 so that the difference between the calculated focus lens position and the current position of the focus lens 58 becomes zero. it can.

  Specifically, when positioning the focusing lens 58 at the focusing lens position, as shown in FIG. 7, the current position of the focusing lens 58 is acquired (step S21), and the current position of the focusing lens 58 is obtained. The difference from the in-focus lens position is calculated (step S22), and it is determined whether or not this difference is 0 (step S23). If the difference is not 0, the difference is set to 0 to drive the difference to the drive motor 84. (Step S24), the drive motor 84 is driven according to the converted rotation amount (step S25), and the process returns to step S21. By repeating these processes, the focusing lens 58 can be positioned at the focusing lens position.

  At this time, since the reduction gear mechanism 82 and the clutch mechanism 80 have a mechanical clearance, even if the drive motor 84 is driven according to the specified rotation amount, the rotation amount of the drive motor 84 and the focusing lens 58 are actually Although there may occur a phenomenon in which the amount of movement when moving is not always the same, the absolute position of the focusing lens 58 can always be detected instantaneously, that is, for each frame. Positioning processing for 58 can be performed quickly and reliably.

  In the present embodiment, the absolute position of the focusing lens 58 on the optical axis L can be quickly obtained, and the focusing lens 58 can be positioned at the focusing lens position, so that the autofocus operation for the focusing lens 58 can be performed quickly. And can be done accurately.

(A) is a schematic block diagram of the absolute position detection apparatus which shows one Example of this invention, (b) is a side surface when the slit board which has one slit is arrange | positioned between a light source and a linear image sensor. FIG. 3C is a side view when a slit plate having two slits is disposed between the light source and the linear image sensor. It is a block block diagram of the absolute position detection apparatus which shows one Example of this invention. It is a wave form diagram for demonstrating operation | movement of the absolute position detection apparatus shown in FIG. It is a longitudinal cross-sectional view of an electronic level autofocus mechanism and a telescope. It is a block block diagram of an electronic level. It is a flowchart for demonstrating the autofocus operation | movement of an electronic level. It is a flowchart for demonstrating positioning control of a focusing lens. It is a block block diagram of the conventional absolute linear encoder.

Explanation of symbols

12 linear image sensor 14 moving body 16 light source 17 collimator lens 18 clock driver 20 CPU
DESCRIPTION OF SYMBOLS 21 Slit plate 22 Comparator 28 Rising edge detection circuit 30 Falling edge detection circuit 32, 34 Counter value latch circuit 36 Addition circuit 38 Bit shift circuit 52 Telescope 56 Objective lens 58 Focusing lens 62 Beam splitter 64 Focusing mirror 66 Eyepiece lens 68 Light receiving sensor 80 Clutch mechanism 82 Reduction gear mechanism 84 Drive motor

Claims (1)

A plurality of photoelectric conversion elements are linearly arranged at equal intervals, and in response to a signal charge accompanying photoelectric conversion of each photoelectric conversion element in response to a shift clock (SC) generated corresponding to each photoelectric conversion element A linear image sensor (12) for sequentially outputting electrical signals; and the linear image sensor arranged opposite to the linear image sensor and arranged to be relatively movable along an arrangement direction of the plurality of photoelectric conversion elements. A light source that emits light toward any one of the photoelectric conversion elements, a collimator lens disposed between the light source and the linear image sensor, and disposed between the collimator lens and the linear image sensor. A light branching means for branching light emitted from the light source into a plurality of lights, and outputs of the plurality of photoelectric conversion elements on the linear image sensor A comparator that sequentially captures from the second photoelectric conversion element according to the arrangement order and compares it with the determination level, and the comparison result of the comparator is monitored, and the output of any one of the photoelectric conversion elements exceeds the determination level A rising edge detection means for detecting the comparison result of the comparator, a falling edge detection means for detecting that the output of any one of the photoelectric conversion elements is equal to or lower than the determination level, and the shift A first storage means for counting the number of shift clocks in response to the clock and storing the count value every time a detection output is generated from the rising edge detection means; and a shift clock number in response to the shift clock. The second storage means for counting and storing the count value every time a detection output is generated from the falling edge detection means, and the first storage means Based on the plurality of stored count values and the plurality of count values stored in the second storage means, the irradiation position of the light on the linear image sensor is detected using the first photoelectric conversion element as a reference. An absolute position detection device comprising position detection means.

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