JP2577283B2 - Laser ranging sensor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a laser distance measuring sensor capable of measuring a distance at high speed with high accuracy.

[0002]

2. Description of the Related Art As shown in FIG. 4, a conventional laser distance measuring sensor emits a laser beam whose intensity is modulated. A light receiving unit 101 for receiving the incoming laser light and converting it into an electric signal, an analog signal processing unit 102 for converting an analog signal converted into an electric signal by the light receiving unit 101 into a digital signal, and an analog signal processing unit 102 The configuration includes an arithmetic processing unit 103 that performs arithmetic processing on the output digital signal, and an output unit 104 that outputs the displacement distance arithmetically processed by the arithmetic processing unit 103 as digital data.

FIG. 5 shows a principle of distance measurement in such a distance measuring sensor. In such a sensor, an optical triangular distance measuring method using a semiconductor laser or the like as a light emitting element is adopted. Therefore, when the light emitted from the light projecting element 200 is narrowed down by the light projecting lens 201 and then irradiated onto the object OB for distance measurement, the light is emitted to the object OB for distance measurement.
After being diffusely reflected on the surface B, the angle θ with respect to the projection axis X
Light receiving element 204 (semiconductor position detecting device (hereinafter referred to as PSD)) by light receiving lens 203 installed at an angle only
Imaged on top.

In such a laser distance measuring sensor, when the object to be measured is displaced by Δr, the position of the light spot on the light receiving element 204 moves by Δx. Is established. Therefore, if the movement amount of the light spot on the PSD {x is detected, the displacement amount of the object to be measured can be calculated by the following formula:
r will be known.

The PSD used in such a distance measuring sensor is a photovoltaic element having output electrodes at both ends belonging to a photodiode having a pin structure. When the light reflected from the surface of the object OB for distance measurement is irradiated as a light spot on the PSD, the high-resistance p-layer is divided in inverse proportion to the luminance center of gravity of the light and the distance between both electrodes. ,
Assuming that the length of the PSD is L, the outputs I1 and I2 are: It is expressed by both equations. Therefore, from equations (2) and (3), Is obtained.

In such a laser distance measuring sensor, the distance measuring range is ± 6 degrees from the reference position of the object to be measured.
mm, and in order to realize a distance measuring sensor having a distance measuring resolution of 0.2 μm, it is necessary to express 60,000 or more in its output. If the object to be measured is 0.2μ
In the case of displacement by m, the output changes by 8.3 × 10 −5 V. In such a distance measuring sensor,
A measuring device for knowing the output value is required, and it is more advantageous to carry out digital processing from the viewpoint of easy handling of data for enhancing the function of the distance measuring sensor. However, in order to digitally display the distance to be measured, a numerical value of 60,000 or more is required in an integer representation. Therefore, the word length must be 16 bits or more, and the output data of the output unit is 16 bits. A word length is required, and in order to secure this resolution, data input to the arithmetic processing unit, that is, output data of the analog signal processing unit also needs a 16-bit length. Therefore, 16
Since it is necessary to handle bit-length data and perform calculations at high speed, a CPU capable of high-speed processing in which one word has a 16-bit length is used.

Normally, division performed by the CPU is performed in the form of 1 word = 2 words ÷ 1 word. Therefore, when calculating equation (4), the number of bits of the denominator Ι1 + Ι2 is a problem. Ι
Since 1 and 2 are 16-bit input data (positive), the sum of the denominator values, that is, 1 + 2, may overflow the expression range of 16-bit data. Therefore, in the conventional method, in order to avoid such an overflow, the data # 1 and # 2 are dropped into 15-bit data or the like so as not to overflow in advance. Even if it is $ 1, $ 2, the bit is dropped. Even if the overflow does not occur, the input data is at most a 15-bit numerical value.
There was a problem that the precision of the bit operation was reduced.

[0008]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and provides distance measurement data as digital data having a specific number of bits so as to minimize loss of precision in arithmetic operation processing. An object of the present invention is to provide a laser distance measuring sensor capable of performing high-speed calculation and outputting digital data of a specific bit required for distance measuring.

[0009]

According to the present invention,
In order to achieve the above object, an arithmetic processing unit comprises: an N-bit arithmetic and logic unit; and a first unit that shifts digital data of a specific number of bits output from an AD converter in bit units into N-bit data. A second bit shift unit, a sign flag register for storing whether or not the overflow of the arithmetic operation processing result is stored, and an accumulator for storing the result of the arithmetic operation in the arithmetic and logic operation unit. The presence / absence of an overflow resulting from the arithmetic operation processing of the data stored in the second bit shift device is determined by referring to the sign flag stored in the sign flag register. If no overflow has occurred, While the obtained operation result is output as digital data through the accumulator, overflow occurs. If that is, after performing the right logical shift with respect to the operation result, after executing the arithmetic processing for correcting the right logical shift is performed, and has a configuration for outputting digital data.

[0010]

According to the distance measuring sensor of the present invention, the distance measuring data detected by the light receiving element and digitized by the AD converter is subjected to arithmetic processing in the arithmetic processing section, and at that time, it is determined whether or not overflow has occurred. Only when an overflow occurs, the operation result is right-shifted logically and corrected at the end. If an overflow occurs in the operation result, the distance measurement data is dropped before the calculation process The calculation process can be performed at higher speed and with higher accuracy than the calculation method of redoing the calculation.

[0011]

FIG. 3 is a block diagram showing an embodiment of a distance measuring sensor according to the present invention. A laser diode LD is used as a light emitting element, and a PSD is used as a light receiving element. The laser diode driving unit DC intermittently drives the laser diode LD with a timing pulse sent through the timing circuit TC to perform modulated light emission in a predetermined pattern. The laser light emitted through the light-receiving element PS is radiated toward the measurement target object OB, and is diffusely reflected on the surface of the measurement target object OB.
D is received. Optical signals received by the light receiving element PSD are output as position currents I1 and I2, each of which is converted into a voltage signal by an IV converter I / V (# 1) or (# 2). Thereafter, after the first-stage gain adjustment is performed by the programmable gain amplifiers PGA1 (# 1) and (# 2),
The second-stage gain adjustment is performed by GA2 (# 1) and (# 2). The signal amplified to a predetermined level in this manner is further sampled and held by S & H (# 1),
After being sampled and held in (# 2), the AD converter A /
D (# 1) and (# 2) convert the digital data into 16-bit digital data. The converted 16-bit digital data is sent to the latch circuit LATCH, read by the DSP constituting the arithmetic processing unit, and After the arithmetic processing described later is performed, the digital data is output as 16-bit digital data. If necessary, the digital signal is converted into an analog signal by the D / A converter DA and output. In addition,
OSC is a crystal oscillator that generates a basic clock necessary for arithmetic processing, TC is a timing circuit, and a laser diode driving unit DC, a sample and hold circuit S & H (#
1), (# 2) and AD converters A / D (# 1), (#
Synchronized with the operation of 2).

In such a distance measuring sensor, the latch circuit L
16-bit data latched by ATCH
1 and Ι2 are read by a DSP constituting an arithmetic processing unit, and an arithmetic process as described later is executed to obtain an equation (1):
The displacement Δr of the object to be measured is obtained from the equation (4), and is output as digital data.

FIG. 1 is a block diagram showing only a main part of an arithmetic processing unit for performing arithmetic processing in a distance measuring sensor according to the present invention. The AD converters A / D (# 1), ( #
2) first and second bit shifters 2 for shifting the 16-bit digital data output from the 16-bit latch circuit 1 for taking in and temporarily storing the 16-bit data output from 2), 6, an arithmetic and logic unit 3, an accumulator 5 for temporarily storing the arithmetic result processed by the arithmetic and logic unit 3, and a determination as to whether or not an overflow has occurred in the arithmetic result in the arithmetic and logic unit 3. And a sign flag register 4.

Steps 300 to 304 in FIG. 2 are performed according to the present invention using the hardware configuration shown in FIG.
A flowchart for calculating the expression, particularly for calculating the value of the denominator Ι1 + Ι2, is shown. In order to determine the displacement Δr of the object to be measured by the distance measuring sensor of the present invention, it is necessary to first determine the light spot displacement Δx on the light receiving element PSD. When used to calculate equation (4), the value of the denominator Ι1 + Ι2 must be 16 bits. Therefore, even if arithmetic logic unit 3 has a bit length of 16 bits or more, it is necessary to arrange data $ 1 + $ 2 in the upper 16 bits. This way,
When $ 1 + $ 2 overflows the range of 16-bit data, the content of the sign flag register 4 is "1".
(The same sign bit as the most significant bit of the arithmetic and logic unit 3 is included). Therefore, by referring to the contents of the sign flag register 4 immediately after the arithmetic and logical operation device 3 calculates Ι1 + Ι2, it is possible to easily determine the overflow of the operation result (step
301) . In other words, if the content of the sign flag register 4 is "0", there is no overflow, so the operation result accumulated in the accumulator 5 is output as it is as digital data, and the operation proceeds to the next data operation process. 4 is "1", it is determined that an overflow has occurred, and a rightward logical shift is performed on the operation result, that is, the data of $ 1 + $ 2 .
Step 303) . Here, performing a 1-bit right logical shift is equivalent to halving the operation result, so that the entire expression (4) obtained by executing the 1-bit right logical shift is finalized. Specifically, since it is necessary to perform the correction by multiplying by 1/2, such a correction may be performed at the end after performing the 1-bit right logical shift. Step 3
Numeral 04 is for storing the executed rightward logical shift in order to perform such correction.

The manner in which the above-described arithmetic processing is performed is as follows. Data # 1 is latched from the 16-bit bus and stored in 16-bit latch 1.
The first bit shift device 2 converts the read 16-bit data I1 into N-bit data. That is, 16
'0' is assigned to (N-16) bits other than the bit in which the bit data is assigned. At this time, data $ 1 is assigned to the upper 16 bits, and '0' is assigned to the lower (N-16) bits. Deploy. This result is stored in the accumulator 5. Next, the data # 2 is similarly stored in the 16-bit latch 1 from the 16-bit bus and converted into N-bit data by the first bit shifter 2. The data # 2 thus converted into N-bit data is stored in the accumulator. 5 to the second bit shift device 6. Next, in the arithmetic and logic unit 3, the data # 1
And Ι2 are added. When the arithmetic and logic unit 3 performs the addition in this way, the same bit as the sign bit which is the most significant bit of the added value is transferred to the sign flag register 4, and the operation result of the arithmetic and logic unit 3 is stored in the accumulator 5. Stored again.

Next, the content of the sign flag register 4 is referred to. If the content is "0", the accumulator 5 is read.
Is output, and the processing proceeds to the next operation processing. When the contents of the sign flag register 4 referred to are "1",
If so, a rightward logical shift is performed on the operation result stored in the accumulator 5. However, the operation result obtained by executing the rightward logical shift in this way is finally stored in the accumulator 5 after performing an operation for correcting the executed rightward logical shift. Move on to

[0017]

As will be understood from the above description, according to the laser distance measuring sensor of the present invention, when an arithmetic operation is performed, the presence or absence of an overflow is determined, and only the sensor that has caused an overflow is determined. Thus, the drop of bits is allowed, so that an arithmetic processing method with high calculation accuracy can be realized.

[Brief description of the drawings]

FIG. 1 is a hardware configuration diagram of a main part of an arithmetic processing unit in a laser distance measuring sensor according to the present invention.

FIG. 2 is a flowchart illustrating a calculation processing procedure executed in a calculation processing unit.

FIG. 3 shows a block diagram of a laser distance measuring sensor of the present invention.

FIG. 4 is a block diagram showing a basic configuration of a laser distance measuring sensor according to the present invention.

FIG. 5 is a diagram illustrating the principle of triangular ranging of a laser ranging sensor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... 16-bit latch 2, 6 ... 1st, 2nd bit shift device 3 ... Arithmetic logic operation device 4 ... Sine flag register 5 ... Accumulator

Claims (1)

(57) [Claims] 1. A laser light emitted by a laser light emitting element is reflected by an object to be measured, the reflected light is received by a position detecting element, and an output from the position detecting element is digitally converted by an AD converter. In a laser distance measuring sensor in which an arithmetic processing unit performs arithmetic processing and outputs a displacement distance to a test object as digital data, the arithmetic processing unit includes an N-bit arithmetic logic unit and the AD conversion. First and second bit shifters for shifting digital data of a specific number of bits output from a unit into N-bit data by shifting the digital data in units of bits, and a sign flag register for storing whether an arithmetic operation processing result overflows or not And an accumulator for storing the result of the arithmetic operation in the arithmetic and logic operation device. The data stored in the first and second bit shift devices are provided. The presence or absence of overflow of data results of the arithmetic operations to determine by referring to the sign flag stored in the sign flags register, if not cause overflow,
While the obtained operation result is output as digital data through the accumulator, if an overflow has occurred, the operation result is subjected to a rightward logical shift, and then the executed rightward logical shift is corrected. A laser ranging sensor configured to output digital data after executing a calculation process.