JPS6026166B2 - Photoelectric position detection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for photoelectrically tracking and detecting the position of a rotating or rotationally vibrating object.

First, the direct background leading to this invention will be explained.

In a typical spectrometer, the output wavelength is changed by rotating and displacing a spectroscopic element such as a diffraction grating or prism, but in this case, the output wavelength is indirectly determined from the position of the spectroscopic element. ing. The position detecting means for the spectroscopic element in a conventional spectrometer is a mechanism that uses a potentiometer or the like to detect the position of a feed screw or a cam of a sine bar mechanism that is mechanically connected to the spectroscopic element. With this mechanism, the spectroscopic element cannot be rotated and displaced at high speed, so only slow wavelength scanning can be performed. 'Due to a certain need, the present inventors developed a spectrometer in which a spectroscopic element is supported by a torsion bar, and this is rotated and vibrated at high speed by an electromagnetic drive mechanism (for example, about the IK ratio), so that wavelength scanning is repeated at high speed. was developed.

In the case of this spectrometer, the above-mentioned conventional techniques could not be used at all to detect the position of the spectroscopic element, and the development of a new position detection device was required. The purpose of the present invention is to
An object of the present invention is to provide a position detection device that detects its position in a non-contact manner.

By the way, a photoelectric mechanism that uses light is known as a technique for detecting the displacement or position of a moving object in a non-contact manner.

For example, for an object that rotates or reciprocates linearly, 9
A slit plate with two systems of slit rows with a phase difference of 0 degrees is installed, and a light emitter and two systems of light receivers are fixedly arranged with the slit plate in between, and the displacement of the object,
That is, there is a mechanism for detecting the direction of displacement by distinguishing the phase difference between pulse signals obtained from the two systems of light receivers as the slit plate is displaced, and for detecting the amount of displacement by counting the number of pulses. In addition, a single slit other than the one described above is formed at an appropriate position on the slit plate, and a corresponding emitter and receiver are fixedly arranged, and the pulse signal obtained from this receiver is transmitted. By using the position reference signal, not only the displacement amount of the slit plate but also the position information can be obtained. This mechanism is very suitable for large objects, large drive mechanisms, and large displacements.

However, like the above-mentioned diffraction grating, the target object is small and the amount of displacement is small, and there are many problems in detecting the displacement with high resolution. That is, if the target object is small, the size of the slit plate that can be attached to it is extremely limited, and a small slit plate must be provided with very thin rows of slits at a small pitch. Then, the amount of light received by the light receiver through this slit becomes very small, and the light cannot be detected unless a highly sensitive but expensive light receiver such as a photomultiplier tube is used. In other words, if an inexpensive and low-sensitivity photodetector is used, there is a limit to how small the slit width can be, and therefore it is difficult to achieve high resolution. This invention solves the above problems by providing a light reflecting surface on the target object, magnifying the displacement using the principle of an optical lever, and changing the incident optical path and reflected optical path to this light reflecting surface. The present invention provides a position detecting device in which a sufficient amount of detection light can be obtained for a light receiver by providing a slit plate for each and devising the arrangement of the slit rows of the slit plate.

Hereinafter, an embodiment in which the present invention is applied to the wavelength control mechanism of a spectrometer as described above will be described in detail based on the drawings.

FIG. 1 is a schematic diagram of a spectrometer and an overall plan view of the apparatus of the present invention, and FIG. 2 is a perspective view showing the apparatus of the present invention in more detail. First of all, the part surrounded by the two-dot chain line in Fig. 1 is a spectroscope.To explain it briefly, white light emitted from a light source is collected into a slit 3 by a lens 2, and the light passing through the slit 3 is reflected by a plane mirror. 4, the light reaches a collimating mirror 5, which is then irradiated onto a diffraction grating 6. The light of a certain wavelength that is separated there reaches a focusing mirror 7, passes through a plane mirror 8, and then passes through a slit 8.
This means that the light is emitted from the device. The diffraction grating 6 has an axis 10
The wavelength of the light emitted from the slit 9 corresponds to the angular position of the diffraction grating 6 about the axis 10. The device of the present invention detects the angular position of the diffraction grating 6 in a non-contact manner, and will be described next. In FIGS. 1 and 2, light emitted from a light source 11 passes through a lens 12 and is irradiated onto a first slit plate 13, and slit rows 20, 23 are provided on this slit plate 13 in two stages, upper and lower. The light that has passed through the diffraction grating 6 is reflected by a plane mirror 14 provided on the back surface of the diffraction grating 6, passes through a lens 15, and reaches a second slit plate 16.

This optical system, which consists of lenses 12, 15, etc., displays bright and dark images by the slit array of the slit plate 13 on the slit plate 16.
It is set to form an image at a magnification of 1:1. The slit plate 16 has slit rows 31, 32 in three stages: upper, middle, and lower.
33 are provided, and each stage has a slit row 31332,
The light leaking from 33 passes through separate lenses 41 and 4, respectively.
2 and 43, and is introduced into separate light receivers (phototransistors, etc.) 51, 52, and 53, respectively.
Detailed aspects of the slit rows of the two slit plates 13 and 16 are shown in FIGS. 3 and 4, respectively (note that this does not correspond to the schematic diagram in FIG. 2).

First, in the upper slit row of the slit plate 13, a large number of slits each having a length of about 2 sleeves and a width d are arranged at a pitch of 2 d. In addition, the slit rows 3 in the upper and middle rows of the slit plate 16
1 and 32, a plurality of slits having a length and a width d are arranged at a pitch 2d equal to the above, and in particular, the slit row 3
1 and 32, the slit arrangement is shifted by 1/4 pitch. Furthermore, the slit row 1 at the lower stage of the slit plate 13
3 and the lower slit row 33 of the slit plate 16 are exactly the same, and a plurality of slits having length and width d are arranged at irregular intervals without periodicity. Then, by the optical system, a bright and dark image of the slit plate 13 is formed on the slit plate 16, as if the slit plate 13 in FIG. 3 were superimposed on the slit plate 16 in FIG. 4. That is, the contrast image of the slit row 20 with a length of 2 corresponds to the upper slit row 31 and the middle slit row 32 of the length on the slit plate 16, and the brightness and darkness image of the slit row 23 corresponds to the slit row 33. corresponds to In the above configuration, the diffraction grating 6 is moved along the axis 1 by a drive mechanism (not shown).
The plane mirror 14, which is integrated with the diffraction grating 6, rotates and oscillates within an appropriate angular range around 0. At this time, the plane mirror 14 integrated with the diffraction grating 6 also rotates, so that the optical axis A of incidence from the lens 12 and the slit plate 13 to the plane mirror 14 and the plane mirror 14 15 mustard beans, 1 slit plate
The angular relationship with the reflection optical axis B toward the 6th side changes.

This is optically equivalent to rotating the slit plate 13 about an axis that passes through the intersection of the optical axis A and the plane mirror 14 and is perpendicular to the plane of the paper in FIG. (It is curved in an arc shape centered on the axis.) Therefore, when the plane mirror 14 is rotated by a slight angle around the axis 10, the bright and dark image of the slit plate 13 formed on the slit plate 16 is aligned with the optical axis B. It moves in a direction perpendicular to and parallel to the paper plane of FIG. 1, that is, in the direction in which the slits are arranged.

This phenomenon is illustrated in FIGS. 3 and 4 by a slit plate 13,
16, the contrast image of the slit plate 13 in FIG. 3 is formed on the slit plate 16 in FIG. 4 as described above,
The bright and dark image moves on the slit plate 16 in the horizontal direction of the drawing. Therefore, when observing the light caused by the image (bright part) of the slit array 20 passing through the slit array 31, one brightness and darkness can be observed for each pitch of the image of the slit array 20. This is the translation. Similar brightness and darkness can be observed for the light passing through the slit row 32, but since the slit arrangement in the slit row 31 and the slit row 32 are shifted by 1/4 pitch, the continuous brightness and darkness observed as described above is Also, the slit row 31 side and the slit row 32 side are shifted by 1/4 period. In other words, plane mirror 1
4 is rotated in a certain direction, the receiver 51
and 52 outputs are waveform-shaped, respectively.
As shown in a and b in the figure, the pulse signals correspond to the above-mentioned brightness and darkness, and moreover, they are signals with a phase difference of 90 degrees.

As is well known, by distinguishing the phase difference between these two systems of signals (which phase is leading), the direction of displacement of the plane mirror 14 can be determined, and the number of output pulses of the light receiver 51 or 52 can be adjusted in the direction of displacement. The amount of displacement (position) of the plane mirror 14 is determined by counting up or down accordingly.
can be detected. This circuit technology is well known and will not be described in detail. Further, the reference position of the plane mirror 14 can be detected as follows.

The slit row 23 and the slit row 33 have the same pattern,
Moreover, since it is an irregular arrangement pattern with no periodicity,
Only when the plane mirror 14 comes to a certain position, the brightness image of the slit row 23 matches the slit row 33, and at that time the output level of the light receiver 53 becomes extremely high. Even if it passes through, the amount of light is very small. 5c shows the change in the output level of the light receiver 53, and as is clear from this figure, when the output level of the light receiver 53 exceeds the appropriately set reference level S, an output signal is emitted. In this way, when the plane mirror 14 comes to the predetermined reference position, the world force signal is generated. Returning the explanation to the spectrometer, when the reference position signal is output from the light receiver 53 side, the output wavelength determined by the position of the diffraction grating 6 at that time (checked and set in advance) is preset in the counter. If this preset value is configured to sequentially count up or down by a value corresponding to the direction and amount of displacement of the diffraction grating 6 as described above, the count will be counted every time the diffraction grating 6 passes the reference position. Mistakes are corrected and accurate wavelength readings can be performed. Regarding the drive mechanism of the diffraction grating 6, as a mechanism for rotating and vibrating the diffraction grating at high speed, the diffraction grating is supported by a torsion bar or the like, and the electromagnetic drive mechanism and the vibration system of the diffraction grating are related, and the vibration of the diffraction grating is A method of exciting the system using its natural frequency is known.

In this mechanism, if the displacement direction detection signal obtained by phase difference discrimination of the outputs of the light receivers 51 and 52 is used as a signal to detect the vibration state of the diffraction grating and switch the drive direction of the electromagnetic drive mechanism, There is no need to provide a separate detection system. Next, other embodiments of the present invention will be described.

In the above embodiment, the magnification of the optical system is 1, but if this magnification is not 1, the contrast image of the slit row of the slit plate 13 on the slit plate 16 will be different from that of the slit plate 1.
The size and spacing of the slits on both slit plates may be appropriately different so that the width and spacing of the slits are equal to the slit width and spacing of the slit row No. 6. That is, the slit rows of both slit plates form similar patterns with appropriate ratios in accordance with the magnification of the optical system. In addition, in the above embodiment, there are two slit rows of the slit plate 13 and two slit rows of the slit plate 16.
1 and 32, but it goes without saying that the slit row 20 may be separated into a portion corresponding to the slit row 31 and a portion corresponding to the slit row 32. In this case, a phase difference is created only on the slit rows 31 and 32 side of the slit plate 16, but this can also be created by the separated slit rows 20 as described above. It is the same even if you create it with As explained in detail above,
According to the photoelectric position detection device of the present invention, it is only necessary to attach a reflecting mirror to the target object or form a reflecting mirror surface, and it is not necessary to attach a reflecting mirror to the target object, or to form a reflecting mirror surface on the target object. , the present invention can be applied to objects moving at high speed without any problems.

Furthermore, the size of the slit plate is not limited by the size of the target object, and the displacement of the target object is magnified by the principle of optical levers. Furthermore, on the receiver side, rather than detecting the light leaking from a single slit, the light leaking from a plurality of slits is collected and detected, so that a sufficient number of light stars can be obtained. These work effectively in detecting minute displacements of a target object using a high-resolution chamber.

[Brief explanation of drawings]

The drawings show one embodiment of the present invention, and FIG. 1 is a schematic plan view of a spectrometer and an overall plan view of the device of the present invention, and FIG. 2 is a perspective view showing the device of the present invention in more detail. , FIGS. 3 and 4 are detailed views of the slit plate in the same device, and FIG.
The figure is an explanatory diagram of the output of the same device. 6...Target object (diffraction grating), 12, 15, 41, 42,
43... Lens, 13... First slit plate, 14... Reflector, 16... Second slit plate, 51, 52, 53
...Receiver. Fig. 1 Fig. 2 Fig. h Lacquer painting Fig. 5

Claims (1)

[Claims] 1. A reflecting mirror is provided on a target object that rotates or rotationally vibrates, and a first slit plate is interposed in the optical path of incidence from the light source to the reflecting mirror, and a second slit plate is interposed in the optical path of reflection from the reflecting mirror. and the bright and dark images of the first slit plate are focused on the second slit plate by appropriate lens systems provided in these optical paths; Three systems of slit rows corresponding to each other are provided, and three systems corresponding to each of the three systems of slit rows are provided on the output side of the second slit plate to condense and receive light emitted from each slit row.
The slit rows of the first system of the two slit plates have similar patterns, and a plurality of slits are arranged in an irregular pattern with no periodicity. Only when it reaches a certain position, the first
configured such that the contrast image of the first system of slit rows of the slit plate matches the first system of slit rows of the second slit plate so that an output signal is emitted from the first system of light receivers;
The second and third slit rows of the first slit plate have a large number of slits of equal width arranged at equal pitches, and the second and third slit rows of the second slit plate have slits arranged at equal pitches. The slit rows of the second and third systems of the first slit plate have a plurality of slits arranged in a similar pattern, and when the target object is displaced, the first system of light receivers and the first system of slit rows are arranged in a similar pattern. Approximately 90
configured to output a pulse train with a phase difference of degrees;
A photoelectric type that detects the reference position of the target object from the output of the first system of light receivers, and detects the displacement direction and displacement amount of the target object from the outputs of the second and third systems of light receivers. Position detection device.