JP3398777B2 - Displacement sensor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a displacement sensor using a triangulation method. 2. Description of the Related Art A displacement sensor irradiates a measuring object with light from a light projecting means, receives reflected light from the measuring object with a light receiving optical system, and forms a condensing surface of the light receiving optical system. A pair of position signals corresponding to the position of the spot moving on the light-collecting surface is output by a position sensor (PSD) arranged at a position corresponding to the distance of the measurement object, and the position of the object is determined based on the position signal. There is a displacement sensor adopting a triangulation method that calculates a position. In this type of displacement sensor, when the amount of light is out of the measurement range or the amount of light is insufficient, either the clamp mode or the analog mode is employed depending on the output form. [0003] clamping mode, as shown in FIG. 3, when the measurement range, an output mode to lock the analog output at a constant value V _R, the hold mode as shown in FIG. 4, out of the measurement range At this point, the immediately preceding value (the lower limit value V _L immediately before the lower limit is exceeded when the value is out of the lower limit, and the upper limit value V _H immediately before the value is out of the range than the upper limit) is held. . [0004] The output modes of the clamp mode and the hold mode have advantages and disadvantages in the application form of the displacement sensor. First, in the clamp mode, as shown in FIG. 5, when measuring a connector pin, an IC lead, or the like, a burn-out occurs between the pins as shown in FIG. Position is easy to understand and suitable for determining the height of a workpiece such as a connector pin. However, in a step measurement as shown in FIG. 6 or a flatness measurement of a work having a rough surface, as shown in FIG. 8A, an analog output burns out due to excessive or insufficient light amount in a step portion, and the like. There is a problem that a measurement error occurs. On the other hand, in the hold mode, the immediately preceding value is held even if the light amount is excessive or insufficient due to a step portion such as a step measurement. Therefore, as shown in FIG. 8B, it is suitable for an application such as a step measurement in which a measurement error does not occur and a light amount changes. However, in measuring the height of a connector pin or the like, as shown in FIG. 7B, the value between the pins is held at a value immediately before, that is, a value close to the level of the pin portion. There is a problem that it is difficult to determine the height. As described above, since the conventional displacement sensor employs only the clamp mode or the hold mode, if the mode of the displacement sensor happens to correspond to an inappropriate application, the measurement error will be reduced. When it occurs, or when used, it is necessary to search for a displacement sensor in a mode suitable for the application, and there is a problem that it is difficult to use. The present invention has been made in view of the above problems, and has as its object to provide a displacement sensor that can be used for various applications with one displacement sensor. [0008] A displacement sensor according to the present invention comprises: a light projecting means for irradiating light to an object to be measured; a light receiving optical system for receiving light reflected from the object to be measured; A position detection unit that is arranged on a light-collecting surface of the optical system and outputs a pair of position signals corresponding to the position of a light-converging spot that moves within the light-collecting surface according to the distance of the measurement object; A displacement sensor having two analog output forms, a clamp mode and a hold mode, and a switching means, wherein the switching means selects either the clamp mode or the hold mode output form. I'm trying to get. Embodiments of the present invention will be described below in more detail with reference to the embodiments. FIG. 1 is a block diagram showing a configuration of a displacement sensor according to an embodiment of the present invention. This displacement sensor includes a sensor section 31 and an amplifier section 32. The sensor unit 31 includes a light emitting element 1 composed of a semiconductor laser, a semiconductor laser driving circuit 1a for driving the light emitting element 1, a light emitting lens 2, a light receiving lens 3, and a position detecting element (PSD) 4. And current-voltage converters 6 and 7 for converting the currents I ₁ and I ₂ output from the position detecting element 4 into voltages, and a subtractor 8 for subtracting both outputs of the current-voltage converters 6 and 7 And an adder 9 for adding both outputs. The amplifier unit 32 includes amplifiers 10 and 11 for amplifying the outputs of the subtractor 8 and the adder 9 of the sensor unit 31, sample-hold circuits 12 and 13 for sampling and holding the outputs of the amplifiers 10 and 11, A divider 14 that receives the outputs X and Y of the sample and hold circuits 12 and 13 as inputs and performs division, a comparator 15 that compares the output Z of the divider 14 with a reference value, and an output Y of the sample and hold circuit 13
A comparator 16 for comparing the reference value with a reference value;
AND circuit 17 which receives both outputs of the above as inputs, a clamp circuit 18, a hold circuit 19 which receives an output Z of the divider 14 as an input, an output of the clamp circuit 18 and the hold circuit 1
9 and the output Z of the divider 14 and the output of the AND circuit 17 as inputs. The output of the divider 14 and the output of the clamp circuit 18 or the hold circuit 19 depend on the state of the input signal. An output control circuit 21 for selecting and outputting an output and an output circuit 22 are provided. The clamp circuit 18 is a constant voltage circuit that outputs a constant voltage (for example, 5 V). In the displacement sensor of this embodiment, a laser beam emitted from the light projecting element 1 irradiates a measuring object 5 through a light projecting lens 2. The laser light is reflected by the measuring object 5, collected by the light receiving lens 3, and received by the position detecting element 4. When the laser beam is received by the position detecting element 4, the currents I ₁ and I ₂ are output from the position detecting element 4. The current outputs I ₁ and I ₂ are voltage-converted by the current-voltage converters 6 and 7, and subtraction and addition are performed by the subtracter 8 and the adder 9. The processed signals are supplied to the amplifier 1 respectively.
The signal is amplified by 0 and 11 and further converted into DC from the pulse signal by the sample and hold circuits 12 and 13. The outputs X and Y of the sample-and-hold circuits 12 and 13 that have been subjected to the DC conversion are subjected to the calculation of X / Y = Z by the divider 14, and the distance output Z is output. The calculated distance output Z and the output Y from the position detecting element 4 are compared with comparators 15 and 16 respectively.
To compare with the reference value to judge the inside and outside of the measurement range and the excess and deficiency of light. The comparator 15 inputs the output “H” (high) to the AND circuit 17 when the distance output Z is within the measurement range, and the comparator 16 ANDs the output “H” when the light amount is stable.
Input to the circuit 17. The AND circuit 17 inputs the output “H” to the output control circuit 21 when both inputs are “H”. The output control circuit 21 receives this “H” and outputs the distance output value Z from the divider 14 to the output circuit 22. When the output of the AND circuit 17 is "L", that is, when the output is out of the measurement range or the amount of light is excessive or insufficient, the output control circuit 21 receives this "L" output, In the clamp mode, the constant voltage from the clamp circuit 18 is output to the output circuit, and in the hold mode, the voltage held in the hold circuit 19 is output to the output circuit 22 in accordance with the input state of. Note that the hold circuit 19 is constituted by a sample hold circuit,
The output value output from the divider 14 is held at a timing synchronized with the light emission pulse of the light emitting element 1. According to the displacement sensor of this embodiment, the output form of the analog output can be switched by the changeover switch according to the application, so that an output error due to the output form can be eliminated and the measurement can be facilitated. In another embodiment, a portion surrounded by a broken line in FIG. 1 can be replaced with a microcomputer or the like as a displacement sensor. FIG. 2 shows a circuit portion which is replaced by the broken line portion. In this embodiment, an A / D conversion circuit 41 receives the output X from the sample hold circuit 12 and converts it into a digital signal, and an A / D conversion circuit receives the output Y from the sample hold circuit 13 and converts it into a digital signal. And a CPU (microcomputer) that receives the digital X and Y signals from the A / D conversion circuits 41 and 42 and calculates the distance output Z
43, a changeover switch 44 for switching between a clamp mode and a hold mode, and a D / A for converting an output such as a distance output value Z from the CPU 43 into an analog signal and outputting the analog signal.
And a converter 45. [0015] In CPU 43, software means performs calculation of the following equation to calculate the distance output value Z _n. Z _n = a · X _n / Y _n + b (a and b are constants) Here, when the input Y is 0.2 <Y ≦ 5, the light amount is in a stable state, and when the calculation result Z is 1 ≦ Z _n <3. The measurement range.
In this state, CPU 43 controls to output an operation result Z _n. Also, the changeover switch 44 is ON,
When the clamp mode is set, input Y is 0.2
<Y _n ≦ 5 or the distance output value Z is 1 ≦ Z _n
If not <3, the CPU 43 controls to output the output value 5. When the changeover switch 44 is OFF and the hold mode is set, the input Y becomes 0.2 <Y _n
When ≦ 5 or when the distance output value Z is not 1 ≦ Z _n <3, the CPU 43 is controlled to output the immediately preceding distance output value Zn _-1 . In this embodiment, since the microcomputer is used for the calculation unit and the discrimination unit, both the clamp mode and the hold mode can be set without increasing the number of circuits (the number of chips). . According to the present invention, the analog output mode has two modes, a clamp mode and a hold mode, and can be switched to one of the modes by a changeover switch. For example, for an application such as a height measurement of a connector pin or an IC lead or a step measurement, a measurement error can be reduced in an output form and measurement can be facilitated.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram showing a configuration of a displacement sensor according to an embodiment of the present invention. FIG. 2 is a circuit block diagram for explaining a displacement sensor according to another embodiment of the present invention. FIG. 3 is a diagram showing an analog output inside and outside a measurement range in a clamp mode of a displacement sensor. FIG. 4 is a diagram showing an analog output inside and outside a measurement range in a hold mode of a displacement sensor. FIG. 5 is a diagram illustrating measurement of the height of a connector pin by a displacement sensor. FIG. 6 is a diagram illustrating measurement of a step of an article using a displacement sensor. FIG. 7 is a diagram showing an analog output when measuring a connector pin in the clamp mode and the hold mode of the displacement sensor. FIG. 8 is a diagram illustrating an analog output at the time of measuring a level difference in the clamp mode and the hold mode of the displacement sensor. [Description of Signs] 4 Position detecting element 14 Dividers 15 and 16 Comparator 18 Clamp circuit 19 Hold circuit 20 Switch 21 Output control circuit

────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Toshitaka Sato 10 Okado Dodocho, Ukyo-ku, Kyoto, Kyoto Prefecture (56) References JP-A-5-149722 (JP, A) JP-A-58- 168904 (JP, A) Japanese Utility Model 3-16017 (JP, U) (58) Fields surveyed (Int. Cl. ⁷ , DB name) G01B 11/00-11/30 G01C 3/00-3/32

Claims (1)

(57) [Claims] 1. A light projecting means for irradiating light to an object to be measured, a light receiving optical system for receiving light reflected from the object to be measured, and a condensing light of the light receiving optical system. A position detection unit that is arranged on the surface and outputs a pair of position signals corresponding to the position of the condensed spot that moves within the condensing surface according to the distance of the measurement target; and a unit that calculates the output signal. A displacement sensor having an output form of two analog outputs of a clamp mode and a hold mode, and having a switching means, wherein the switching means can select either the clamp mode or the hold mode. A displacement sensor.