JPH0267911A - Distance measuring apparatus - Google Patents

Abstract

PURPOSE:To measure the distance with high accuracy by so arranging light beams as to be incident upon the surface to be measured at right angles and receiving light reflected at said surface to be measured from a perpendicular direction. CONSTITUTION:When light beams are found at one end on a light receiving surface of a photoreceptor 5, the one end on the receiving surface of the receptor 5 is conjugate with a position at a height H1 where incident light is radiated to a surface to be measured. On the other hand, when the light beams are found at the other end on the light receiving surface of the photoreceptor 5, the other end is conjugate with a position at a height H2 where the incident light is radiated to the surface to be measured. In the above condition, when a rotary reflecting mirror 4 is rotated in a direction shown by an arrow A to move the light beams from the one end to the other end on the receiving surface of the photoreceptor 5, one indicent position is found on the receiving surface of the photoreceptor 5 which is conjugate with an incident position of light beams on the surface to be measured having the height H1 to H2. Therefore, the height of the surface to be measured can be obtained in the range from H1 to H2 from the position on the receiving surface where the largest value of signals is received from the photoreceptor 5.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a distance measuring device, and particularly to one that measures the distance to a surface to be measured using a light beam.

(Prior Art) As a conventional technology related to this type of device, there is Japanese Patent Application Laid-Open No. 162911/1983 based on triangulation.

This is a lens that emits laser light from a laser light source.
A light projection optical system that projects light onto the surface to be measured from an oblique direction via a swinging mirror, a light receiving lens whose optical axis is provided almost perpendicular to the surface to be measured, and a laser beam focused by the light receiving lens. a light-receiving optical system that includes a photoelectric conversion element that photoelectrically converts the
, and by rotating the swinging mirror to change the angle of incidence of the laser beam on the surface to be measured, and finding the rotation angle θ of the t3 moving mirror when the signal obtained from the light-receiving element becomes maximum, Letting d be the distance between the center of the light receiving lens and the center of rotation of the swinging mirror, the distance between the center of the light receiving lens and the surface to be measured can be determined by d/lanθ.

(Problem to be Solved by the Invention) In a device based on such triangulation, the direction in which the laser beam is projected onto the surface to be measured and the optical axis of the light receiving optical system are at a certain angle. If the target surface is a mirror surface or has small surface roughness (ground surface or lapped surface), the reflected light may return to the receiving optical system, making measurement impossible, or even if it does return, the S/N may be low. This resulted in very poor measurements and large errors.

Therefore, the present invention does not select the surface properties of the surface to be measured, that is, the surface to be measured can be not only a diffusive surface, but also a metal with a strong specular reflection component, or a mirror surface such as glass. The purpose of this invention is to provide a device that can achieve high precision measurement without contact.

(Means for Solving the Problems) The present invention includes a beam splitter (1), an objective lens (2) disposed between the beam splitter (1) and a surface to be measured (6), A light device (3) that projects a light beam onto the surface to be measured (6) via the beam splitter (1) and the objective lens (2), and a light beam projected by the light source device (3). a rotating reflector that allows the light beam reflected by the surface to be measured (6) to enter through the objective lens (2) and the beam block (1), and continuously changes the direction of the reflected beam; (4), a light-receiving bag W (5) that receives the beam reflected by the rotating reflector (4) and outputs a signal representing the size of the incident beam; The position of the incident beam at that time is determined, and from this position the measurement target surface (6
) detecting devices (20) to (20) that output signals related to the position of (
27).

(Function) The present invention includes a light projection optical system (light source device, beam splitter, objective lens) that projects a light beam onto a surface to be measured, and a light receiving optical system that receives reflected light from the surface to be measured. By using a common objective lens, the system (objective lens, beam splinter, rotating reflector, light receiving device) can be made coaxial. It has the advantage of being able to measure metals such as metals with high accuracy, and with respect to the diffusion surface, there is a large tolerance for the inclination of the surface.

(Embodiment) FIGS. 1(a) and 1(b) are diagrams showing an optical system according to an embodiment of the present invention. Objective lens 2 installed
a light source device 3 that projects a light beam onto a surface to be measured 6 via a beam splitter 1 and an objective lens 2; The light enters through the objective lens 2 and the beam splitter l, and the reflected beam is reflected by the rotary reflector 4, which continuously changes the direction of the reflected beam, and the rotary harp reflector 4. A light-receiving bag 'It5 is shown that outputs a signal representing the brightness.

As the beam splitter 1, a light splitting member such as a half prism is used, and as the light source device 3, a laser light source and the laser light from the laser light source are converted into a narrow parallel beam as shown in FIG. 1 together with an objective lens 2. A lens system is provided to project light onto the surface to be measured, and a rotational reflection 14
As a light receiving device, one that is rotationally driven by a known drive device such as a motor or a galvanometer is used so as to be rotated or oscillated by a rotation center ρ.
Position detection members such as CCD and PSD are used.

Then, as shown in FIG. 1(a), the light beam reaches the light receiving device 5.
When the light-receiving surface of the light-receiving device 5 is located at one end of the light-receiving surface, one end of the light-receiving surface of the light-receiving device 5 is conjugate with the position of the surface to be measured at the height H, which is hit by the incident light. Figure 1 (b)
As shown in FIG. If the positions are conjugate, the rotating reflector 4 rotates in the direction of arrow A from the state shown in FIG.
When moving from one end to the other end (direction B) on the light-receiving surface of , the height changes from Hl to H! There is one light beam incident position on the light receiving surface of the light receiving device 5 that is conjugate to the light beam incident position on the surface to be measured located at . The diameter becomes the minimum, and if the light receiving device W5 has a light receiving width narrower than the diameter of this minimum light beam, the output signal from the light receiving device 5 becomes the maximum.

Therefore, the position on the light-receiving surface that gives the maximum value of the signal from the light-receiving device or the rotational position of the rotating reflector 4! (angle), the height of the surface to be measured is from height Hl to H! It will be found within the range of .

FIG. 2 is a block diagram of an electrical circuit used with the optical system of FIG. 1.

In FIG. 2, 1, the pulse from the pulse generator 20 is
The driving device 21 inputs a start pulse S and a scanning pulse S2 following the start pulse S1 to the CCD 50, as is well known. As a result, the CCD 50 is sequentially scanned from one end of the photoelectric conversion section to the other end, and the photoelectric conversion signals of these photoelectric conversion sections are outputted from the CCD 50 in time series.

On the other hand, the start pulse S from the drive device ff21.

and scanning pulse S2 are also input to the counter 22, where the former is used as a reset pulse and the latter number is used as a value indicating the position of the photoelectric conversion section of the CCD 50. That is, the count value of the counter 22 after being reset by the start pulse is nothing but the address of the charge conversion section from which the charge conversion signal outputted from the CCD 50 was obtained.

The output signal of the CCD 50 is input to a sample-and-hold circuit and a low-pass filter 23, and is an analog signal having a peak at a time corresponding to the position of the photoelectric conversion unit when the size of the incident beam is the smallest. becomes. The output signal of the low-pass filter 23 is transmitted to the differentiating circuit 24.
and is converted into a differential signal that crosses zero at the peak position.

This differential signal is input to the waveform shaping circuit 25, and the waveform shaping circuit 25 generates one pulse at the zero-crossing point of the human input signal. The pulses output from the waveform shaping circuit 25 are input to the gate terminal of the gate circuit 26 to control opening and closing of the gate circuit 26.

Since the count value of the counter 22 is input to the input terminal of the gate circuit 26, the gate circuit 26 outputs the signal when a pulse is generated from the waveform shaping circuit 25, that is, when the size of the incident beam becomes the smallest. A count value corresponding to the address of the photoelectric conversion unit at the incident position of the incident beam is output.

The count value output from the gate circuit 26 is converted into the height of the surface to be measured by an arithmetic device 27 such as a micro convenience store. The address of the photoelectric conversion unit, that is, counter 2
Since there is a one-to-one correspondence between the counted value in step 2 and the height of the surface to be measured, the arithmetic unit 27 is provided with a correspondence table between the counted value and the height of the surface to be measured in advance, and the inputted measured value is The height of the surface to be measured corresponding to the numerical value is read out from the correspondence table. The height of the surface to be measured calculated in this way is displayed on the display device 28.

In addition, in the above embodiment, the CCD 50 is used as the light receiving device 5.
Although we have given an example using a CCD50 as the light receiving device 5,
It is not limited to those that can detect both the amount of light and the position of incidence of the light. In other words, a photoelectric conversion element such as a solar cell may be used so that the range of the light receiving surface scanned by the light beam is covered by the rotation of the rotating reflecting mirror 4. In this case, the rotational position of the rotating reflecting mirror 4 may be To know this, it is sufficient to provide a rotation detector such as a rotary encoder on the rotating reflector 4, and if the rotational position of the rotating reflector 4 at the peak position of the output signal of the light receiving device N5 is determined, this rotational position is Since it corresponds to the height of the surface to be measured, the height of the surface to be measured at the peak position of the output signal of the light receiving device '115 can be determined. In such a configuration, the light receiving device 5 only needs to be able to obtain an output according to the amount of incident light, inexpensive solar cells, etc. can be used instead of expensive CODs and PSDs, and the signal processing system can also be simplified. This has the advantage that the entire device is inexpensive.

Furthermore, in the above embodiments, the measurement sensitivity (resolution) can be easily changed by changing the inclination of the light-receiving surface of the light-receiving device 5; However, it is only necessary to increase the swinging range of the rotating reflecting mirror 4, and there is no need to change other components such as the optical system.

(Effect of the invention) As described above, according to the present invention, for the surface to be measured,
The configuration is such that the light beam is incident vertically and the reflected light from the surface to be measured is received from the perpendicular direction, so it can be used against rough surfaces such as metal processed surfaces from mirror or near-mirror surfaces. It is possible to measure surfaces with various surface properties.

Furthermore, in the present invention, even if the position of the surface to be measured changes and the measurement distance changes, there is always a position where the image of the reflected beam is formed on the light receiving surface, and the state where the image is always formed is maintained. Since the distance measurement is performed using the same method, the influence of the surface texture (speckle pattern, etc.) of the object to be measured can be minimized, and highly accurate measurement can be performed.

[Brief explanation of the drawing]

FIGS. 1(a) and 1(b) are diagrams showing optical systems of a distance measuring device according to an embodiment of the present invention, in which each optical system is placed in a conjugate state with a different measured object surface. FIG. 2 is a block diagram of an electric circuit used together with the optical system shown in FIGS. 1(a) and 1(b). (Explanation of symbols of main parts) 1... Beam splitter, 2... Objective lens, 3... Light source device, 4... Rotating reflector, 5 ...... Light receiving device.

Claims (1)

[Claims] a beam splitter, an objective lens disposed between the beam splitter and the surface to be measured, and a light source device that projects a light beam onto the surface to be measured via the beam splitter and the objective lens; , a rotating reflector that allows the reflected light of the light beam projected by the light source device on the surface to be measured to enter through the objective lens and the beam splitter, and continuously changes the direction of the reflected beam; , a light receiving device that receives the beam reflected by the rotating reflecting mirror and outputs a signal representing the size of the incident beam, and a light receiving device that determines the position of the incident beam when the size of the incident beam becomes the smallest; A distance measuring device comprising: a detection device that outputs a signal related to the position of the surface to be measured from a position.