JPS61104202A - Optical displacement meter - Google Patents

Abstract

PURPOSE:To detect change of a solid angle between specimen and incident light ray axis, by making an input signal level of an arithmetic circuit computing a displacement in an optical displacement meter constant and providing a feedback controlling circuit for stabilizing measuring accuracy. CONSTITUTION:Change of relative solid angle between specimen 5 and incident light ray, changes also light-receiving quantity on a PSD surface obtained from the source of the constant output. A feedback circuit 13, after correcting this, sends an output 15 to a driving circuit 1 in such a way that the light-receiving quantity on the surface PSD is always constant through an arithmetic circuit 9. The circuit 13, upon decreasing of the light-receiving quantity on the surface PSD, increases the output of the source and in case when change of the solid angle increases the light-receiving quantity, it functions that the output of the source is decreases inversely. Consequently, by indication by an output level 13a of the feedback circuit 13 and reading this output level, change of the solid angle in process of measurement can be detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an improvement in the posture control method of a sensor head of an optical displacement meter.

[Conventional technology]

FIG. 3 is a block diagram of a conventional non-contact displacement measuring device disclosed in, for example, Japanese Patent Publication No. 56-10561. In the figure (
1) is a light source drive circuit, (2) is a light source, (3) is a projection lens, (4) is a light spot projected onto the object to be measured, and (5) is a light source drive circuit.
) is the object to be measured, (6) is the light receiving lens, (7) is the light receiver,
(8a) and (8b) are the outputs, (9) is the arithmetic circuit, α
O is a timing circuit, and (11) is a calculation output.

Next, the operation will be explained. The light emitted from the light source (2) driven by the light source drive circuit (1) passes through the light projecting lens (3).
) is focused to create a light spot (4) on the object to be measured (5).
to project. This light spot (4) is further focused by a light receiving lens (6) and projected onto a light receiver (7),
The image is formed on a light receiver (7). For example, if a semiconductor device detection element (hereinafter abbreviated as PSD) is used as the light receiver (7),
Current value i6 h i output from both ends of the photoreceiver (7)
b changes depending on the position of the received light image on the PSD. That is, when the received light image is at the center of the PSD, 1a = 11°, but when the received light image moves toward Ia side, as i and L increase, Ib becomes smaller, and conversely, when the received light image moves toward lb, 1b becomes like a dog and ta becomes smaller.

Therefore, the displacement of the object to be measured (5), that is, the light spot (4)
The change in the position of P is calculated using the following equation (1) as the distance from the center position of the PSD of the received light image on the PSD.
It can be calculated as η multiplied by a certain conversion coefficient.

This calculation is performed in the calculation circuit (9) shown in Fig. 4, and the result is output (lυ) as the displacement of the object to be measured (5). In equation (1), l and L + ib are proportional to the incident sight to the PSD. amount.

[Problem that the invention seeks to solve]

By the way, the conventional optical displacement meter is constructed as described above, but when measuring displacement, the light source (2), light emitting lens (3), light receiving lens (6), and light receiver (7) shown in Fig. 6 are used. In order to maintain the sensor head in the most suitable measurement posture for measurement, the solid angle formed by the object to be measured (5) and the optical axis of the optical displacement meter must be determined visually or using other jigs or devices. However, if the shape of the object to be measured (5) becomes complicated, it is difficult to measure it, and it is not easy to control the optimum measurement posture.
Therefore, there is a drawback that measurement takes time.

SUMMARY OF THE INVENTION An object of the present invention has been made to eliminate such drawbacks of conventional devices. The objective is to provide an optical displacement meter that can determine the optimal measurement posture for the object.

[Means and actions for solving the problem] In order to achieve the above object, a feedper is provided for stabilizing the measurement accuracy by keeping the input signal level of the arithmetic circuit that calculates the displacement constant in the optical displacement meter.

By providing a feedback control circuit to keep the input level to the arithmetic circuit constant and displaying the output of this feedback control circuit externally, it is possible to prevent the difference between the object to be measured and the projection optical axis caused by changes in measurement conditions. The purpose is to detect changes in solid angle.

[Embodiments of the invention]

Figure @1 is a configuration diagram of an optical displacement meter showing an embodiment of the present invention. In the figure, (1) to (11) are the same as the conventional device. O2 is a timing pulse output, n31u feedback control circuit, (9a) is an input signal to feedback circuit 03, (13a) is an output of feedback circuit (131), and a4fi is its display device.

In the figure, when the relative solid angle between the object to be measured (5) and the light emitting optical axis changes, the light receiver on the PSD surface obtained from the light source of constant output also changes. The feedback circuit 03 corrects this and sends an output of +15 to the 2 drive circuit (1) via the arithmetic circuit (9) so that the light receiver ◆ on the PSD surface is always constant.
For example, if the light-receiving area on the PSD surface decreases, the output of the light source increases, and in the case of three-dimensional keratinization, where the amount of light received increases, the output of the light source decreases. Function. Therefore, if such control is performed while keeping the distance to the object to be measured constant, the light receiving section will remain constant, but the change in the solid angle between the object to be measured and the emitting optical axis will be reflected as the output of the feedback circuit. This is detected as a change in the resulting light source drive level signal. Therefore, by displaying the output level (13a) of the feedback circuit Oj, the measurer can detect changes in the solid angle during measurement by reading this output level, and easily know the measurement attitude of the sensor head. Can be done.

In addition, if you first find the optimal solid angle for the object to be measured (5), then you can perform measurements by keeping the output of the feedback circuit (13) constant.
It is possible to maintain the optimum posture for measurement.

In the above embodiment, the semiconductor device detection element (
PSD), but other C, C, D or photodiode arrays may be used.

In the above embodiment, the driving level of the light source is controlled by the feedback circuit a3, but as shown in FIG. A similar function can be obtained by controlling the amplification degree using the feedback circuit α3).

It is also possible to directly measure the output of the light beam and detect a change in the solid angle between the light emitting axis of the sensor head and the object to be measured from the measured value.

〔Effect of the invention〕

The present invention provides an optical displacement meter that is equipped with a feedback circuit to control the drive level of the light source in order to keep the input signal of the arithmetic circuit constant, and displays the output of the feed bank circuit at that time to display the output of the feed bank circuit to control the light emitting optical axis of the sensor head. Since the sensor head is designed to be able to detect the solid angle formed by the object and the object to be measured, it is now possible to set the sensor head to the optimal posture when measuring the displacement of the object to be measured.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing one embodiment of the present invention, FIG. 2 is a block diagram showing another embodiment, and FIG. 6 is a block diagram of a conventional device. In the figure, (1) is the drive circuit for the optical name, (2) is the light source, (3) is the projection lens, (4) is the light spot, (5) is the object to be measured,
(6) is a light receiving lens, (7) is a light receiver, (9) is an arithmetic circuit, αJ is a feedback circuit, and 0 is a display device of the feedback circuit. Note that the same reference numerals in the figures indicate the same or equivalent parts.

Claims (2)

[Claims] (1) A light source, a light projecting lens that focuses a radiation beam of light from the light source, a light receiving lens that captures an image of the radiation beam on the object to be measured, and a light receiving surface on the image forming surface of the light receiving lens. an optical displacement meter comprising: a photodetector arranged to transmit an electrical signal corresponding to the imaging position of the radiation beam on the light-receiving surface; and an arithmetic circuit that calculates the displacement of the object to be measured based on the electrical signal. An optical displacement meter comprising: a feedback circuit for controlling an input signal level to the arithmetic circuit to a constant level; and a display for displaying an output signal of the feedback circuit. (2) A patent claim characterized in that the display device that displays the output signal of the feedback circuit is configured to display the attitude of a sensor head that includes a light source, a light projecting lens, a light receiving lens, and a light receiver. The optical displacement meter according to item 1.