JPH0868665A - Position detector - Google Patents

Abstract

PURPOSE: To prevent generation of error signal by subjecting the inner face of a holding member to antireflection processing. CONSTITUTION: A luminous flux generated from a light emitting element 2 impinges on the light receiving face of a position detecting device 1 through primary reflection on the inner face of a holding member 5, or reaches a device 2 through plural reflection on the member 5 and the arm of a moving member 3, or an external light intruded through an opening of the member 5 reaches the device 1 directly or through reflection on the inner wall of the member 5, the arm of the member 3, etc. In this regard, a divider does not output a correct value proportional to the shift of a slit 3a but outputs the weighted mean of a spot produced through the slit 3a and a spot of received light produced through reflection on the inner face or extrusion of external light thus generating an error signal. When shade lines A are provided on the inner wall of the member 5 and at the arm part of the member 3, the light reflected on the inner face, the externally intruded light, and the luminous flux reaching the device 1 through reflection are scattered and generation of error signal is prevented.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a position detector for detecting, for example, a one-dimensional minute deviation amount in a non-contact manner by using a light emitting element and a light receiving element. It is a thing.

[0002]

2. Description of the Related Art Conventionally, a photoelectric conversion type position detector having a light emitting element and a light receiving element has been used as a position detector for detecting a one-dimensional minute deviation without contact.

The light emitting element is, for example, an infrared light emitting diode (i
As the light receiving element, a position detecting device (PSD) that outputs a current according to the position of the light receiving spot is used. The light emitting element and the light receiving element are fixed by a fixed member so as to face each other, and a mask having a thin slit is arranged at an intermediate position between the light emitting element and the light receiving element. Then, the photoelectric conversion is performed to generate a photocurrent corresponding to the light intensity and the spot position, that is, the relative position between the light receiving element and the slit, and measurement is performed.

There is also a structure without a mask having slits, in which the light emitting element is directly fixed to the movable member and a photocurrent is generated according to the relative position of the light receiving element.

[0005]

In the position detector, however, it is said that a part of the light beam generated from the light emitting element is reflected by the inner wall of the fixing member and is incident on the light receiving element to generate an erroneous signal. There was a problem. Further, the fixing member needs an opening for securing a movable space of the mask having a slit, and it is inevitable that outside light enters from there, and there is a problem that an erroneous signal is generated by this outside light. there were.

[0006]

According to the present invention, a light emitting means for generating a light beam, a photoelectric conversion means for generating an electric signal according to a received light beam, and either or both of the light emitting means and the photoelectric conversion means are held. In a position detector provided with a holding member, and depending on the structure, a displacement means that is movable relative to the holding means and is illuminated by a light beam, the inner surface of the holding means is subjected to antireflection treatment. .

[0007]

Embodiments of the present invention will be described below with reference to the drawings.

1 and 2 are views showing a first embodiment of the present invention.

In FIG. 1, 1 is a PSD (position
A light receiving element such as a sensing device). 2 is IR
A light emitting element such as an ED (infrared light emitting diode). A moving member 3 has an arm protruding in one direction, and has a narrow slit hole 3a at its tip. 4a and 4b are guide bars, and the moving direction of the moving member 3 is one-dimensionally regulated by this. 5 is a holder, PSD1 on the top
The IRED 2 is adhered and fixed to the lower part so that the light-receiving surface and the light-emitting surface face each other, and the slit 3a of the moving member 3 is positioned exactly between the IRED 2 and the PSD 1. A is a light-shielding line having irregularities.

In FIG. 2, 6a and 6b are current-voltage conversion circuits for converting two photocurrents output from the PSD 1 into voltage signals. 7 is the current-voltage conversion circuit 6
Reference numeral 8 is a subtraction circuit for obtaining the difference between the output signals of a and 6b, and reference numeral 8 is an addition circuit for obtaining the sum of the output signals of the current-voltage conversion circuits 6a and 6b. Reference numeral 9 is a division circuit for obtaining the ratio of the outputs of the subtraction circuit 7 and the addition circuit 8. This output has a value proportional to the displacement amount of the spot position irradiated on the PSD 1.

Next, the operation of the above configuration will be described step by step.

It is assumed that the moving member 3 has moved a minute amount in the direction regulated by the guide bars 4a and 4b. Then, since the slit 3a also moves at the same time, the position of the spot where the luminous flux emitted from the IRED 2 passes through the slit 3a and is irradiated on the PSD 1 also changes. The PSD 2 outputs a pair of photocurrent signals having a size corresponding to the position of the spot from the two terminals, respectively. The pair of photocurrent signals are converted into voltage signals by the current-voltage conversion circuits 6a and 6b, respectively, and the difference between the two signals is added by the subtraction circuit 7 to the addition circuit 8
The sum of both is calculated by. The division circuit 9 outputs a ratio with the output of the addition circuit 8 as the denominator and the output of the subtraction circuit 7 as the numerator, so that this output voltage has a value proportional to the amount of movement of the moving member 3 described above.

However, the luminous flux generated from IRED2 is
External light that has reached the light-receiving surface of the PSD 1 by the primary reflection on the inner surface of the holder 5 or has reached the PSD 1 by the n-order reflection on the holder 5 and the arm of the moving member 3 or has entered through the opening of the holder 5. May reach the PSD 1 directly or by being reflected by the inner wall of the holder 5 or the arm of the moving member 3. At this time, the output of the division circuit 9 is the slit 3a.
Does not output the correct value proportional to the movement amount of the slit 3a
Since a weighted average of the spot generated in 1) and the light receiving spot generated by internal reflection or external light intrusion is output, an erroneous signal occurs. Therefore, a light shielding line as shown in FIG. 1 is provided on the inner wall of the holder 5 and the arm portion of the moving member 3. By doing so, the PSD1 is affected by internal reflection and external light penetration and reflection.
The light fluxes reaching the distance are scattered, and as a result, generation of false signals can be avoided.

FIG. 3 is a diagram showing a second embodiment of the present invention.

A portion 5a in FIG. 3 is a light flux limiting portion that projects into the holder 5. The light flux limiting portion of the holder 5 projects from the left and right sides in the moving direction of the moving member 3 toward the center, and the narrowest interval is such that the light flux emitted from the IRED moves through the slit 3a even when the moving member 3 is maximally moving. It is a necessary and sufficient distance that cannot prevent the light from passing through and reaching the light receiving surface of PSD1. However, due to this overhang, it becomes difficult for the light reflected on the inner surface of the holder 5 to reach the light receiving surface of the PSD 1, and the occurrence of an erroneous signal is avoided.

FIG. 4 is a diagram showing a third embodiment of the present invention.

Reference numerals 3b and 5b in FIG. 4 are matte paints having a very small reflectance applied to the arm of the moving member 3 and the inner surface of the holder 5, and thereby the generation of an erroneous signal due to the inner surface reflection or the reflection of the external light. It is something to avoid.

FIG. 5 is a diagram showing a fourth embodiment of the present invention.

Reference numerals 3c and 5c in FIG. 5 denote satin finish applied to the arm of the moving member 3 and the inner surface of the holder 5. This can be realized without increasing the manufacturing cost by giving a suitable draft taper to the mold in advance when performing the molding of the moving member 3 and the holder 5 and performing the satin finish. This satin scatters the reflected light of the inner surface reflected light and the reflected light of the external light, and the light quantity reaching the PSD 1 can be remarkably reduced, so that an erroneous signal can be avoided.

The example in which the moving member has the slit and the light emitting element and the light receiving element are fixed has been described above. However, one of the light emitting element and the light receiving element is attached to the moving member and the other is fixed. It is needless to say that the same effect can be obtained in the position detector having the structure by the completely same implementation. Further, the predetermined purpose can be achieved even if some of the above Examples 1 to 4 are used in combination.

[0021]

According to the present invention, it is possible to prevent the luminous flux emitted from the light emitting means from being reflected by the inner surface of the holding means to become stray light, and to prevent external light from entering and becoming harmful light. There is an effect that a position detector excellent in linearity that does not generate an erroneous signal can be obtained.

[Brief description of drawings]

FIG. 1 is a perspective view showing a first embodiment of the present invention.

FIG. 2 is a diagram showing a circuit configuration of a first embodiment.

FIG. 3 is a perspective view showing a main part of the second embodiment.

FIG. 4 is a perspective view showing a third embodiment.

FIG. 5 is a perspective view showing a fourth embodiment.

[Explanation of symbols]

 1 Light receiving element (iRED) 2 Position detection device (PSD) 5 Holding member A Light-shielding line

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location G02B 5/00 B 5/02 B

Claims (5)

[Claims] 1. A position detection device comprising: a light emitting unit for generating a light beam; a photoelectric conversion unit for generating an electric signal according to the received light beam; and a holding unit for holding either or both of the light emitting unit and the photoelectric conversion unit. A position detector characterized in that an inner surface of the holding means is provided with an antireflection structure. 2. The position detector according to claim 1, wherein the antireflection structure is an uneven light-shielding line. 3. The position detector according to claim 1, wherein the antireflection structure is projected to the inside of the holding means. 4. The position detector according to claim 1, wherein the antireflection structure is a matte paint layer. 5. The position detector according to claim 1, wherein the antireflection structure is satin finished.