JPH03229113A - Distance measuring instrument - Google Patents

Abstract

PURPOSE:To accurately measure the distance to a body to be measured under proper conditions at all times by leading the detection signal of a position detecting element to a focus adjusting means when the distance is measured, and adjusting an irradiation light beam automatically so that the beam is correctly put in focus on a measurement area of the body to be measured. CONSTITUTION:When the position of the body 5 to be measured is measured, the body 5 to be detected is irradiated with irradiation light 4 from a semiconductor laser 11 while a projection lens 12 and, therefore, an actuator 8 is set at a standard position, and the detection signal outputted by the position detector 13 of a signal processing part 3 is inputted to a driving circuit 9 in this state through the position detecting element 22 of a photodetection part 2. The driving circuit 9 drives the movable bobbin of the actuator 8 so that the irradiation light 4 is focused in a minimum- diameter spot 6 on the surface of the body 5 to be measured. When the body 5 to be measured is displaced and the irradiation light 4 comes to out of focus, the exciting current supplied from the driving circuit 9 to the actuator 8 varies to move and correct the position of the projection lens 12, so that the distance is measured while the minimum-diameter light spot 6 is formed on the surface of the body 5 to be measured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rechargeable distance measuring device known as a laser displacement meter.

[Conventional technology]

The above-mentioned distance measuring device focuses the reflected light of the light beam of a laser beam irradiated from a light projecting unit toward the object to be measured through a light projecting lens, and forms an image on the light receiving surface of a semiconductor device detection element through a light receiving lens. Furthermore, a device that measures the distance to the object to be measured or its displacement by processing the detection signal of the position detection element is well known as a laser displacement meter, for example, as disclosed in Japanese Patent Laid-Open No. 119006/1983. It is widely used as a distance and displacement sensor in product processing and inspection processes.

[Problem to be solved by the invention]

By the way, the distance measuring device described above has the following problems in terms of its use. In other words, when the target of the measurement area defined on the object to be measured has an extremely small area, but the spot diameter of the light beam irradiated from the light projector toward the object to be measured is larger than the target. In this case, the reflected light irradiated onto a region other than the target is also distributed and received on the light receiving surface of the position detection element. For this reason, the energy center of gravity of the reflected light from the target cannot be detected accurately, and as a result, highly accurate measurement becomes impossible. In other words, when measuring in a so-called out-of-focus state, in which the focus of the light beam irradiated from the light projecting unit through the light projecting lens is not focused on the surface of the measured object, reflected light that forms an image on the light receiving surface of the position detection element Distance because the spots are spread out instead of concentrating on one point.

The measurement accuracy of displacement amount decreases.

Therefore, to improve measurement accuracy, it is important to minimize the spot diameter of the light beam irradiating the object to be measured, that is, to ensure that the light beam that passes through the projection lens is focused on the target surface of the object to be measured. It is necessary to measure the conditions. Conventional distance measuring devices are constructed using a fixed focus system in which the light projecting lens of the light projecting section is fixedly mounted and the relative distance to the light source is constant. For this reason, if the position of the object to be measured deviates from the standard position, the light beam irradiated onto the surface of the object becomes out of focus and the diameter of the light spot increases, resulting in a decrease in measurement accuracy as described above. problem occurs.

The present invention was conceived in consideration of the above points, and the distance to the object to be measured is always accurately determined under appropriate conditions by automatically adjusting the irradiation light beam to correctly focus on the measurement area of the object to be measured during measurement. .

It is an object of the present invention to provide a distance measuring device capable of measuring the amount of displacement.

[Means to solve the problem]

In order to solve the above problems, the distance measuring device of the present invention is provided with a focus adjustment means for moving the projection lens along the optical axis, and the detection signal of the position detection element is focused at the time of measurement. The light beam is taken into the adjusting means and the position of the projection lens is corrected based on this so that the light beam is focused on the surface of the object to be measured.

[Effect]

The focusing means for the light projecting lens in the above configuration includes, for example, an electromagnetic actuator that moves the light projecting lens in its front axis direction, and a drive circuit for the actuator. In addition, the relationship between the detection signal of the position detection element corresponding to the distance and displacement of the object to be measured and the drive current of the actuator under measurement conditions in which the irradiation beam from the light projector is correctly focused on the object to be measured is It is stored in advance in a ROM table attached to the drive circuit.

Then, at the beginning of actual measurement, the detection signal output from the position detection element of the light receiving section is input into the actuator drive circuit, and the focus of the projected beam is correctly aligned on the surface of the object to be measured by referring to the ROM table mentioned above. After determining whether or not the light is connected, if the light is out of focus, the light projecting lens is controlled to be corrected and moved in the optical axis direction via the actuator.

As a result, the irradiation light beam is correctly focused on the object to be measured, and the light spot formed there has the smallest diameter. In this state, the reflected light from the object to be measured is concentrated and received at one point on the light receiving surface of the position detection device element. Therefore, after establishing such measurement conditions, the detection signal of the position detection element is processed into the position and displacement amount in the subsequent signal processing section. can always be measured with high measurement accuracy.

〔Example〕

Embodiments of the present invention will be described below based on the drawings.

First, Figure 1 is a block diagram of the entire distance measuring device.
In the figure, l is a light projecting section, 2 is a light receiving section, and 3 is a signal processing section, and the irradiation light 4 emitted from the semiconductor laser 11 of the light projecting section l is irradiated onto the object to be measured 5 through the projecting lens 12. A light spot 6 is formed on the surface. Further, the reflected light 7 of the light spot 6 reflected on the surface of the object to be measured 5 passes through the light receiving lens 21 of the light receiving section 2 and passes through the semiconductor device detection element (PSD) 2.
The image is formed on the light receiving surface of 2. Note that this position detection element 22
is a diffused type PIN photodiode, and a current 11 corresponding to the image formation position on the light receiving surface is generated from the electrodes at both the left and right ends of the diode.
+ Output Ig. This output current 1. .
Output to 2. Further, the computing unit 32 performs predetermined arithmetic processing after sampling and holding the detection signal, and outputs a measurement signal representing the distance or displacement amount from the object to be measured 5 as an analog quantity or a digital quantity. Note that 33 is a driver for the semiconductor laser 11, and 34 is a driver 33. for the semiconductor laser. and an oscillator that provides a clock signal to the arithmetic unit 32. As for the light receiving section 2, it is assumed that the optical system between the light receiving lens 21 and the position detecting element 22 and the light projecting section 1 is installed so as to satisfy the so-called Scheimpflug condition.

The configuration up to this point is the same as that of the conventional distance measuring device, but new parts have been newly added according to the present invention. That is, the light projecting unit 1 is equipped with an actuator 8 that supports a light projecting lens 12 and moves the nuclear lens back and forth along the optical axis, and an actuator drive circuit 9 that controls the actuator 8 performs signal processing. It is incorporated in part 3. Here, the structure of the actuator 8 is shown in FIG. 2. That is, the actuator 8 includes a fixed yoke 82 that includes a magnet 81 and constitutes a magnetic circuit, and is guided and supported by a support shaft 83 parallel to the optical axis and attached to the yoke 82. It consists of a combined movable bobbin 84, a drive coil 85 wound around the movable bobbin 84, and a spring member 86 fixed at one end and connected to the movable bobbin 84. It is installed,
Further, an excitation current to be passed through the coil 85 is provided from the actuator drive circuit 9.

With this configuration, when the coil 85 is excited, the movable bobbin 84 is driven along the support shaft 83 together with the light projecting lens 12 due to the electromagnetic force acting between it and the fixed side magnetic circuit, and the electromagnetic force and the spring member 86 It comes to rest at a position where the spring force is balanced. By changing the magnitude of the excitation current flowing through the coil 85, the movable bobbin 84° and therefore the light emitting lens 1
The resting position of 2 will also change.

When actually measuring the position of the object to be measured 5, the projection lens 12. Therefore, with the actuator 8 set at the standard position, one irradiation light 4 emitted from the semiconductor laser 11 is emitted from the semiconductor laser 11 through the projection lens 12 toward the object 5 to be measured, and in this state, the position of the light receiving section 2 is detected. Element 22
The detection signal output from the position detector 31 of the signal processing section 3 is taken into the drive circuit 9 via the drive circuit 9.
The actuator 8 generates an excitation current necessary for focusing the irradiation light 4 projected from the light projecting unit 1 through the light projecting lens 12 onto the surface of the object to be measured 5 to form a light spot 6 with the minimum diameter. The movable bobbin 84 is driven. Repeat this action in the third
In FIG. 3(a), the object to be measured 5 is at the standard position, and the focus of the irradiation light 4 transmitted through the projection lens 11 is on the surface of the object to be measured 5. This shows a measurement state in which a light spot 6 with the smallest diameter is formed. On the other hand, when the object to be measured 5 is displaced and the distance increases as shown in FIG. As a result, a light spot 6 is formed on the object to be measured 5.
becomes larger in diameter. In this case, as will be described later, the excitation current applied from the drive circuit 9 to the actuator 8 is changed, the position of the light projection lens 12 is corrected and moved, and the irradiation light 4 transmitted through the light projection lens 12 is as shown in FIG. The focus is on the object to be measured 5 to form a light spot 6 with the smallest diameter.

That is, the actuator drive circuit 9 is equipped with a ROM table, and the actuator 8 is supplied with an appropriate excitation current corresponding to the position of the object to be measured 5, f: position, and the position detector is detected via the position detection element 22 under these measurement conditions. Data related to the signal output from 31 is stored in advance in a ROM table, and during actual measurement, the initial actuator excitation current is used.

The detection signal obtained under these conditions is compared with the data contents of the ROM table to determine whether the focus of the irradiation light 4 matches the position of the object to be measured 5, and it is determined that the focus is out of focus. If it is determined, the projection lens 12 is corrected and moved to a new position, and the excitation current of the actuator 8 is controlled to increase or decrease so that the irradiation light 4 is correctly focused on the object to be measured 5.

Then, under conditions in which it is confirmed that the focus of the irradiation light 4 is correctly focused on the object to be measured 5, a measurement signal is output from the computing unit 32 based on the detection signal of the position detector 31.

As a result, measurement can be performed under conditions in which the irradiation light 4 is focused on the surface of the object to be measured 5 to form a light spot 6 with the minimum diameter, regardless of changes in the distance and displacement of the object to be measured. High measurement accuracy is always achieved within the measurement range.

〔Effect of the invention〕

Since the distance measuring device according to the present invention is configured as described above, it exhibits an outstanding effect.

(1) The position of the object to be measured within the entire measurement range of the distance measuring device.

Focusing of the projection lens is performed using a focusing means so that the irradiation light transmitted through the projection lens forms a light spot with the minimum diameter on the object to be measured, regardless of the amount of displacement. It can be performed.

C2) Therefore, the distance and displacement of the object to be measured are always measured under optimal measurement conditions, and thereby, for example, even if the target in the measurement area is small, measurement can be performed with high measurement accuracy.

[Brief explanation of drawings]

Figure 1 is a block diagram showing the configuration of an embodiment of the present invention, Figure 2 is a perspective view of the configuration of the actuator in Figure 1, and Figure 3 (
In Figure 0, which is an explanatory diagram of focusing operation, a) and (b) are as follows: 1: Light projecting section, 11: Semiconductor laser (light source), 12: Light projecting lens, 2: Light receiving section, 21: Light receiving lens, 22 : Position detection element, 3: Signal processing section, 4: Irradiation light, object to be measured, 6: Light spot, : Reflected light, ! P10 2 Figure 2 ((1) 3rd

Claims (1)

[Claims] 1) a light projecting section that irradiates a light beam from a light source to a measured object through a light projecting lens; a light receiving section that forms an image of reflected light from the measured object on a light receiving surface of a position detection element through a light receiving lens;
In a distance measuring device comprising a signal processing section that calculates the distance or displacement to the object to be measured based on the detection signal of the position detection element, a focal point for moving the lens along the optical axis with respect to the projection lens; The apparatus is equipped with an adjustment means, and is configured such that the detection signal of the position detection element is taken into the focus adjustment means during measurement, and the position of the light projection lens is corrected based on this, so that the light beam is focused on the surface of the object to be measured. A distance measuring device featuring: