JPH0760090B2 - Optical distance detection method - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an optical distance detecting method using a semiconductor image position detecting element, and in particular, it enables a wide range of detection required as a probe for a three-dimensional shape measuring instrument. The present invention relates to an optical distance detection method using a semiconductor image position detection element suitable for realizing a range detection characteristic with a range and high measurement accuracy.

(Prior Art) A mechanical contact method is widely used as a probe for a three-dimensional shape measuring instrument, but it is possible to measure an object that is deformed or destroyed by the contact method and to improve the measurement speed. Therefore, a light beam is projected onto the object to generate a bright spot, the image position of the bright spot is detected by a semiconductor image position detecting element, and the distance to the object surface is determined based on the principle of triangulation. A type of optical distance detecting device is used.

In FIG. 6, the light beam B is projected onto the surface of the object O (O ′) by the light beam projector S to generate a bright spot T (T ′), which is arranged on the observation surface by the observation lens L. The position X (X ') of the image I (I') is projected on the semiconductor image position detecting element D and the distance Z (Z'Z) to the object surface is detected based on the principle of triangulation. The typical configuration of the optical distance detection device for measuring

FIG. 7 shows a conical mirror M between the object O and the observation lens L.
FIG. 2 is a conceptual diagram of an optical distance detection device based on the RIKEN-type small range detection method (RORS) in which a device has been inserted to realize a remarkable size reduction of the device. The image I has an annular shape, and the distance r to the object surface can be obtained by detecting the radial position r by the semiconductor image position detecting element D.

FIG. 8 shows the distance detection characteristics (relationship between the image detection position X (r) and the distance Z) of the optical distance detection device shown in FIGS. 6 and 7. As an image position detecting element in such an optical distance detecting device, a semiconductor image position detecting element whose typical structure is shown in FIG. 9 is exclusively used. This semiconductor image position detecting element is configured by laminating a conductive layer C, a photoelectric film layer P, and a resistance layer R, and providing output electrodes T _A and T _B at both ends of the resistance layer R,
A bias voltage is applied to the conductive layer C via the terminal C _B. When the light L _B is incident on the semiconductor image position detecting element configured as described above, a photocurrent is generated in the photoelectric film layer P at the position where the light is incident, passes through the resistance layer R, and is output from the output electrodes T _A and T _B. Output currents I _A and I _B are detected. Detection currents I _A and I _B
Is a value obtained by dividing the photocurrent according to the resistance ratio of the resistance layer between the incident position of light and the output electrodes T _A and T _B, and the difference (I _B −I _A ) in the output current value is the output current. The value divided by the sum of the values (I _A + I _B ) is a value proportional to the distance from the center to the light incident position. After performing this calculation with the analog signal calculation circuit, the A / D
By inputting to the converter (analog / digital converter), the information on the incident position of light can be acquired as a digital value.

(Problems to be solved by the invention) In the image position detection method in the optical distance detector of the conventional method, the image position detection accuracy (resolution in the detection range) is mainly determined by the analog signal arithmetic processing system and the A / D conversion. It is limited by the accuracy (resolution) of and becomes a value obtained by dividing the detection range by the resolution. Therefore, since the detection error increases in proportion to the size of the detection range and the detection accuracy decreases, it is difficult to realize high-accuracy image position detection over a wide range, and in the end, a wide distance detection range. In principle, it was difficult to realize both high-precision distance measurement and high-precision distance measurement at the same time. Specifically, when it is used as a distance detection probe of a three-dimensional measuring machine or the like, the detection accuracy may be low at the time of surface tracking but has a wide distance detection range, and at the time of measurement, the measurement range may be narrow but high accuracy. However, it was extremely difficult to realize this.

(Means for Solving Problems) The above problems are avoided, that is, the limit of the image position detection accuracy due to the accuracy of the power supply system and the signal processing system and the resolution of the A / D converter is relaxed to detect a wide distance. In order to realize a range and high measurement accuracy, the present invention is characterized in that the position of an optical image is roughly detected over a wide range and the image position is detected with high accuracy in a limited area.

(Operation and Effect of the Invention) When high-precision measurement is not required as in the case of surface tracking, the first semiconductor image position detecting element capable of detecting the image position over a relatively wide range is operated to operate in a wide range. The distance is detected, and it is detected whether or not the distance to the object is within a range in which highly accurate measurement can be performed, and in which direction the distance must be moved to be within the highly accurate measurement section. During high-accuracy measurement, after confirming that an image exists in the high-accuracy measurement section by the operation of the first semiconductor image position detection element capable of measuring a wide range, the image position can be detected over a relatively narrow range for high-accuracy measurement. The second semiconductor image position detecting element is operated to detect the image position in this section, and the overall image position is determined from the installation position of the semiconductor image position detecting element for high precision measurement. This allows the distance to the surface of the object to be measured with high accuracy by the principle of triangulation. The image position in the high-accuracy measurement section can be detected with an accuracy obtained by dividing the section by the resolution of the signal processing system, and the position of the semiconductor image position detection element for high-accuracy measurement can be physically and extremely accurately arranged. Since the stability is extremely high, even if the accuracy of the signal processing system is the same as that of the conventional method, it is possible to detect the distance with extremely high accuracy as compared with the conventional method.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings. 1A and 1B are a plan view and a cross-sectional view showing an arrangement row of semiconductor image position detecting elements for wide area detection and measurement based on the present invention. Distance information is obtained as follows using the semiconductor position detector D _C. When performing wide-range distance detection first, output electrodes provided at both ends
_A rough position was detected using T _A and T _B , and then it was detected that the image position was between the output electrodes T _MA and T _MB between the output electrodes T _A and T _B. In this case, the position X _M of the image is detected with high accuracy by these output electrodes T _MA and T _MB . That is, a part of the first semiconductor position detector that detects the position of the image over a wide range is used as the second semiconductor position detector that measures the position in a limited range within a wide range with high accuracy. To be The actual image position X can be determined as the sum of the electrode positions X _MA and X _M. Since the position X _MA of the electrode can be physically arranged with high accuracy and is extremely stable, the position detection accuracy is actually determined by the accuracy of X _M.

FIG. 2 is an embodiment of a signal processing circuit for operating the semiconductor image position detecting element shown in FIGS. 1A and 1B as shown in the method of the present invention. The output electrode pair T _A , T _B or T _MA , T _MB connected to this signal processing circuit is a switch.
Switched by SW. That is, the output electrodes T _A and T _B are connected to this signal processing circuit during wide range measurement, and the output electrodes T _MA and T _MB are connected during high precision measurement. After the current from the selected electrodes once amplified by the buffer amplifier B _1, B _2, by the operational amplifier _{A 1, A 2 (I B} -I A) and (I _A +
I _B ) is obtained, and this output current difference (I _B
The value obtained by dividing −I _A ) by the sum of output currents (I _A + I _B ) is obtained. This value is digitized by the A / D converter A / D to obtain the distance to the object. In the case of the type in which a point image is obtained on the observation surface as shown in FIG. 5, as compared with the case where two semiconductor position detecting elements for a wide area and a narrow area are installed in parallel, the present invention is It does not require a beam splitter and is in good condition.

FIG. 3 shows a conventional output electrode so that the measurement section can be set to an arbitrary section on the semiconductor image position detecting element by selecting the output electrode so that high accuracy measurement can be performed over a wide range.
An example of the cross-sectional structure of the semiconductor image position detecting element having a structure in which a large number of output electrodes T ₁ , T ₂ ... T _n are added between T _A and T _B has been shown. Fourth
In combination with the signal processing circuit having the output electrode disconnection selection switch shown in the figure, first, the output electrodes T _A and T _B are selected and operated as a semiconductor image position detecting element capable of detecting a wide range, and an image exists. The section is obtained, and then the output electrodes at both ends of the continuous section including the image position are selected to operate as a semiconductor image position detecting element in a narrow range, the image position in this section is obtained, and the output electrodes of the section are determined. Confirm the image position from the position,
Find distance information. Since the position of the output electrode can be physically manufactured accurately and the stability is extremely high, the image position detection accuracy is almost equal to the image position detection accuracy in the measurement section. With this method, it is possible to realize high-precision measurement because the entire detection section is shattered.

As described above, by adopting the usage method of the semiconductor image position detecting element based on the present invention, the accuracy of the signal processing system and the resolution of the A / D conversion are limited to the conventional semiconductor image position detecting range during measurement. Since the image position detection accuracy can be remarkably improved, it is possible to realize an optical distance detection device having a wide detection area and high measurement accuracy.

[Brief description of drawings]

1A and 1B are a plan view and a cross-sectional view showing an arrangement row of semiconductor image position detecting elements for wide area detection and measurement according to the present invention, and FIG. 2 is shown in FIGS. 1A and 1B. FIG. 3 is a block diagram of a signal processing system for the semiconductor image position detecting element shown in FIG. 3, FIG. 3 is a conceptual diagram of a sectional structure of the semiconductor image position detecting element which can be divided into several sections, and FIG. 5 is a block diagram of a signal processing system for the semiconductor image position detector of FIG. 5, FIG. 5 is a conceptual diagram of a conventional optical distance detecting device, and FIG. 6 is a distance detecting method based on the RIKEN compact optical distance detecting method (RORS). FIG. 7 is a conceptual diagram of the apparatus, FIG. 7 is a graph showing the relationship between the distance and the image position detecting apparatus, and FIG. 8 is a conceptual diagram of the sectional structure of the semiconductor image position detecting element used for image position detection. (Explanation of symbols) S ... Light beam projection device, B ... Light beam, T, T '... Bright spot, O, O' ... Object, R ... Resistive layer, P ... Photoelectric film layer, L ...... Observation lens, I, I '... Image, M ... Cone mirror, C ... Bias film layer, C _B ...... Bias electrode, T _A , T _B , T _MA , T _MB , T ₁ , T ₂ … T _n …… Output electrode, D _C …… Semiconductor position detection element for wide range and integrated measurement, A ₁ , A ₂ …… Operational amplifier, ÷ …… Divider, B ₁ , B ₂ … … Buffer amplifier, L _B …… Optical image, A / D …… Analog / digital converter, I _A , I _B …… Output current, S _W …… Output electrode selection switch circuit, X _D …… Selected section Detection position in.

Claims (1)

[Claims] 1. A bright image produced on the surface of an object by projecting a light beam is projected onto an observation plane, and 3 from the position of this projected image.
In the optical distance detection method that acquires the distance information to the surface of the object based on the principle of angular measurement, the first semiconductor position that can detect the image position over a wide range on the observation surface by the electrode pair provided at both ends. A second semiconductor position detecting element capable of highly accurately detecting an image position in a limited range within the wide range by using a detecting element and an electrode provided between the electrode pair of the first semiconductor position detecting element. And the image position determined by the second semiconductor position detecting element with high accuracy, by obtaining the approximate distance information to the object surface by the first semiconductor image position detecting element. An optical distance detection method, characterized in that the image position on the observation surface is determined from the set position in the limited range, and the distance information to the surface of the object is acquired with high accuracy.