JPS6183912A - Signal detection mechanism for optical type displacement measuring apparatus - Google Patents

Abstract

PURPOSE:To obtain a large quality detection signal, by outputting a detection signal cleared of DC components from an amplifier when an interfering light is made incident into a polarization beam splitter. CONSTITUTION:An interfering light 1 is divided into two 1A and 1B with a half-mirror 2, which are further divided into two in the direction separated by 90 deg. from each other with polarized beam splitters 8 and 9 to be incident into photo detectors 10-13 and then, enters a canceling circuit provided corresponding to the splitters 8 and 9. In the case of the splitter 8, the first photo diode D3 is arranged at the position of the detector 10 while the second diode D4 at the position of the detector 11. First and second diodes D3 and D4 are connected in series: the connection point G is connected to an input terminal of an amplifier AMP4 and moreover, a reverse bias power source is connected to the first and second diodes D3 and D4. This cancels DC components of the diodes D3 and D4 at the connection point G to obtain a large detection signal. In the case of the splitter 9, likewise, the detection signal differed by 90 deg. therefrom in the phase is obtained.

Description

[Detailed Description of the Invention] [Field of Industrial Application] Is the present invention an original interference? A signal detector of an optical displacement measuring device that is used to detect the movement of a scale (regarding 14, a signal detection mechanism that can obtain a detection signal excluding the q\n and C components) ].

[Hihiro technology]

A moving diffraction grating? Used as a scale to interfere with diffracted light to change the position of the diffraction grating (distance traveled)? As an optical displacement measuring device designed to detect 1-
Interference between diffracted lights of two beams as shown in Japanese Patent Application Laid-Open No. 510 or Japanese Patent Application Laid-Open No. 191907? The technology used is known.

Changes in the position of the diffraction grating in such a measuring device? As a signal detection mechanism for detection, a structure as shown in Fig. 5 is often used. In Fig. 5, l indicates interference light of two beams, and 2 indicates a half mirror.
13 and 4 are IIi elements, 1s is λ/4&, and 6.7 is a photodetector.

The purpose of the above is to obtain detection signals A and B with different phases of 90' in order to determine the direction as shown in Figure 6 (aL (hJ). The above interference ft,i is divided into two by the -7 mirror 2 and emitted to the m element +f13.4.

By the way, Figure 6 (at r f
b) Detection No. 18 A and H are caused by external light, dust, etc.
Because of the large number of components included, a TKli' component circuit as shown in FIG. 7 was used as a DC 6 component canceling circuit.

In FIG. 7, DI + D2 is a photodiode,
A to IPI to MF is k) by an amplifier.

[Problem that the invention attempts to solve] However, in the above cancellation circuit, the gain of the first stage amplifier?
It is difficult to increase the signal, and gain variation and offset occur, making it impossible to obtain a high-quality detection signal. Since there is a necessity for dividing into 1, the detection signal was in the direction of 1 song where it became even smaller.

〔problem? Means for vivid colors]

The present invention has been made in response to the above-mentioned problems, and is intended to provide an optical displacement measuring device capable of receiving a large detection signal. It is.

In order to achieve such an object, the present invention provides interference light of two beams to be incident and this incident ft? A first optical path in the direction in which the human incident occurs, and a second optical path in a direction far away from the incident source.
a one-dimensional beam nuplitter for dividing into two optical paths and emitting the beam, and a first beam nucleator located in the fifth optical path connected in series.
and a second photodiode located in the second optical path, a reverse bias power supply connected to these first and second photodiodes, and input to the connection point of the first and @2 photodiodes. With the amp connected at the end? The present invention provides a signal detection mechanism for an optical displacement measuring device configured to detect (g @ k) output from the amplifier by removing the DC component Y when the interference light enters the tlia'/l beam splitter. .

[For production]

According to the above configuration, the respective photodiode components at the connection point of the first and second photodiodes are canceled, and the gain of the amplifier can be increased, so that a large detection signal can be obtained.

〔Example〕

Is the drawing below? Refer to the embodiment of the present invention? explain.

Fig. 1 shows a signal detection mechanism according to an embodiment of the present invention? In the configuration diagram shown, 8 and 9 are tuning beam splitters, and 10 to 13 are photodetectors. Figure 2 shows the deflection beam splinter 8
, the specific structure of 9? It shows.

After the interference light 1 from the two beams is split into two by a half mirror 2, each of IA and 1B is further split into two by I#i source beam splitters 8 and 9 in a direction separated from each other [and sent to photodetectors 10 to 13]. It is incident. 'f
That is, a component parallel to the abrasive surface in the direction of the photodetector 10 and a component perpendicular to the plane of the paper interfere in the direction of the photodetector 11 and are emitted.

Here, the phases of the two interference signals differ by 180° and the intensities are almost equal.

On the other hand, the light incident on the half mirror 2 through λ14&5\ is also detected at the detectors 12 and 13 at the angle of 10°11.
There is a similar relationship.

Is Fig. 3 the cancellation circuit of the present invention? Since it is shown, D3
+D4 is a photodiode, and AMP4 is an amplifier. This cancellation circuit is a polarizing beam splitter 8.9
Two pieces are prepared correspondingly.

For explanation, let's take an example of IJiii source beam splitter 8. When taken, the first photodiode D3 is placed at the position of the photodetector IO, and the second photodiode D3 is placed at the position of the photodetector IO.
4 is placed at the position of the photodetector 11.

Moreover, these first and second photodiodes D3 t
D4 is connected in series and connection point G is connected to amplifier A.
It is connected to the input terminal of MP4, and furthermore, a reverse bias power supply is connected to the first and second diodes D3 e D4.

In the above, the first and second photodiodes D3*
At the connection point G of D4, each photodiode's D-C,
Since the component is canceled, the amplitude is multiplied and the fourth
A large detection signal (g) is output from the amplifier AMP4 as shown in Figure (a).

Since the same operation is performed in the case of the polarizing beam splitter 9, a large detection signal having a different phase from lal is output as shown in FIG. 4(b).

In the present invention, the characteristics of the two photodiodes connected in series are made uniform, and unpleasant components such as the 1f1 original qq acid component and dark current are removed (g is the amplifier AM).
P vc large input, output signal because it is amplified with high gain? It can be taken in large quantities.

Further, as shown in Fig. 8, two
Two photodetectors? When used, it is possible to obtain even better quality signals.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, photodiodes 5-[Fe and 5-Fe are connected to each other in the first and second output optical paths of the beam splitter, and these two photodiodes 5-[Fe]
Connect in series and add an amplifier at the connection point? Since each photodiode is connected to a reverse bias electrode, a large detection signal can be obtained.

! Samurai with Iiii'IQ optical parts and cancellation circuit? Few parts required just by combining, C0 component? Detection No. 18 that is not only large but also of good quality because it can be canceled? So vulnerabilities that can be obtained? It can be improved.

[Brief explanation of drawings]

1 and 3 are block diagrams and circuit diagrams showing the present invention (+Ilx), and FIGS. 2 and 4 (aJ + (b
j is a perspective view and characteristic diagram for explaining the present invention, No. 5
Are all of Figures 7 to 7 conventional examples? FIG. 2 is a perspective view, a characteristic diagram, and a circuit diagram shown in FIG. Fig. 8 shows a photodetector fabricated on one substrate of the present invention? Indicates the column when used. 1... Interference light, 2... Half mirror 18, 9...
114ft. Beam splitter, 10 to 13... Photodetector, DI%D4... Photodiode, AMPl to AM
P4... Amplifier. Fig. 1' Fig. 2 Fig. 5 Fig. 6 Fig. 6 1 grain 'B'
Name of the invention: Optical displacement measurement! F- Direct Signal Detection Mechanism 3, Relationship with the Amendment Person Case Patent Dispatch Type Address Name Name Sony Magne School Co., Ltd. 4, Agent Address: 1
05 Address Pill 5, Shiba 3-chome, 3-2-14 Shiba, Minato-ku, Tokyo Specifications to be amended 1 - No. ff Visit IILg Box 1 Detailed description of the invention and drawings (1) Claims of the present application Correct the range as follows. [1. Interfering light from two beams is incident, and the -1 beam splitter splits the incident light into two into a first optical path in the straight direction of the incident light and a second optical path separated from the incident light and outputs it. a first photodiode located in the first optical path and a second photodiode located in the second optical path connected in series;
and an amplifier whose input end is connected to the connection point of the first and second photodiodes, and when the interference light is incident on the beam splitter, the amplifier is connected to the first and second photodiodes. , C. A signal detection mechanism for an optical displacement measuring device, characterized in that it is configured to output a detection signal excluding components. ” (2) “Solution” in line 18 of page 3 of Specification V of the present application is amended to “solution”. (31, page 4, line 6, ``direction'' is deleted. (4) Correct the instructions in the attached sheet of Figure 7.

Claims (1)

[Claims] 1. Polarized light for inputting interference light from two beams and dividing the incident light into two into a first optical path in the straight direction of the incident light and a second optical path in a direction separated by 90 degrees from the incident light. a beam splitter; a first photodiode located in the first optical path and a second photodiode located in the second optical path connected in series; and a beam splitter connected to the first and second photodiodes. and an amplifier whose input end is connected to the connection point of the first and second photodiodes, and when interference light is incident on the beam splitter, a D. C. A signal detection mechanism for an optical displacement measuring device, characterized in that it is configured to output a detection signal excluding components.