JP2013070078A - Reflection type sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a reflection type sensor that can totally reflect divergent light from a light source at the boundary surface with the outside of a package without any light shielding means, thereby preventing the divergent light from entering a light receiving element.SOLUTION: A light beam L0 is a light beam group out of light beams emitted from a light emitting element 23, which is refracted and passes at a boundary surface 53, is reflected at a reflection scale 21 and is guided to a light receiving area S2, and this optical path is effective light to obtain a sensor signal. A light beam La is a light beam which is totally reflected at the boundary surface 53 and propagates in a package. This light beam La is noise light irrelevant to sensor signal light, and a light beam which should not be received. When the light beam La enters a light receiving area S2, S/N of the sensor signal is reduced. Furthermore, a light beam Lb passes through the boundary surface 53 and emits to the outside without reaching the reflection scale 21, and thus it does not substantially affect the precision or the like. The light receiving area S2 is determined on the basis of a light emission area S1 of the light emitting element 23 so that an unnecessary light beam La is not incident to the light receiving area S2 of a light receiving element 24.

Description

  The present invention relates to a reflective sensor that projects light projected from a light emitting element onto a measurement object, receives reflected light with a light receiving element, and detects displacement of the measurement object based on a change in the amount of light.

  FIG. 23 is a perspective view of a conventional reflective encoder, FIG. 24 is an XZ sectional view thereof, and FIG. 25 is a YZ sectional view orthogonal to a displacement detection axis which is an X axis. Of the radiated light from the light emitting element 1 composed of LED chips, the reflected light from the reflection scale 2 is received by the light receiving element 3 composed of a photo IC chip incorporating a signal processing circuit. The semiconductor elements of the light emitting element 1 and the light receiving element 3 are die-bonded on the printed circuit board 4 and further covered with a transparent member made of a translucent resin 5 and a transparent glass substrate 6. The light emitting element 1, the light receiving element 3, the substrate 4, the resin 5, and the transparent glass substrate 6 constitute a detection head 7. On the other hand, the reflective scale 2 includes a reflective layer forming portion 11 including a reflective scale substrate 8, a reflective layer 9, and a reflective layer 10. Such a reflective encoder is disclosed in Patent Document 1, for example.

  26 is a perspective view of a detection head portion of another conventional reflective encoder disclosed in Patent Document 2, and FIG. 27 is a cross-sectional view. A circuit pattern 12a having a predetermined shape is formed on the substrate 12, and a light-emitting element 13 having a light-emitting area 13a and a light-receiving element 14 having a light-receiving area 14a and incorporating a signal processing circuit are die-bonded to the circuit pattern 12a. ing. The terminals of the light emitting element 13 and the light receiving element 14 are connected by a wire 15.

  The light emitting element 13, the light receiving element 14, and the wire 15 are covered with an enclosing member 16 and a transparent glass substrate 17 formed of a transparent resin material. As shown in FIG. 27, the surrounding member 16 needs to be at least as high as the height of the components of the light emitting element 13 and the light receiving element 14, and further considers the loop height of the wire 15 and the joining margin of the optical semiconductor component to the substrate 12. Thus, the thickness of the surrounding member 16 is determined.

  As shown in FIGS. 26 and 27, a light shielding wall 18 is formed at a substantially intermediate position between the light emitting element 13 and the light receiving element 14, and a circuit pattern 12 a is disposed immediately below the light shielding wall 18. As shown in FIG. 27, the light shielding wall 18 is formed by filling a light-blocking resin into a groove having a width W, and the depth of the groove before filling the light-shielding resin is determined between the surrounding member 16 and the transparent glass substrate 17. The circuit pattern 12a on the substrate 12 is protected by being slightly shallower than the thickness.

  By providing the light shielding wall 18, light emitted from the light emitting region 13 a of the light emitting element 13 is prevented from propagating through the surrounding member 16 and entering the light receiving region 14 a of the light receiving element 14.

  For such light-shielding means between the light-emitting element 13 and the light-receiving element 14, various methods have been proposed for reflection-type sensors, reflection-type photointerrupters, and the like that are used for general purposes. Has been.

JP 2003-337052 A JP 2004-6753 A JP 2000-277796 A Japanese Patent No. 3782489 Japanese Patent No. 3261280

  Conventional optical semiconductor packages in reflective encoders and sensors have the following problems. For example, in FIG. 25, the light beam included in the angle θ1 is an effective light beam that is guided from the light emitting region of the light emitting device 1 to the light receiving region of the light receiving device 3 via the reflection scale 2. In this case, when the light emitting element 1 is greatly inclined at an angle of θ2 from the principal ray axis a1 indicating the maximum intensity, the light ray in the angle range θ1 centered on the inclined light ray is the total radiation ray emitted by the light emitting element 1. Very few of them. Therefore, most of the light rays are ineffective components, and there is a problem that the light use efficiency is extremely poor.

  In FIG. 28 showing a part of FIG. 25 in an enlarged manner, when attention is paid to the action of light rays between the light-emitting element 1 and the light-receiving element 3 in the package, the light is emitted from the light-emitting element 1 and on the surface portion 6 a of the transparent glass substrate 6. There is a ray path as typified by the reflected ray L. When the angle θ3 exceeds the critical angle (= θi), the light beam L is totally reflected and enters the light receiving element 3, and becomes a large bias component light and is superimposed on the sensor signal. A problem occurs.

  In such a case, the substantial S / N of the sensor signal is greatly reduced due to the fact that the effective reflected light is small and the bias component light is large. In order to expand the effective light beam, the effective light beam can be obtained by using a lens. However, when the lens is used, the characteristics of the sensor vary due to the positional deviation between the optical axis of the lens and the light emitting element 1 and the light receiving element 3. It will end up.

  Although a means for enlarging the light receiving area of the light receiving element 3 can be considered easily, a large amount of totally reflected light from the surface portion 6a of the transparent glass substrate 6 is received at the same time, and a substantial S as a sensor signal is received. There is almost no improvement effect of / N. Further, the entire detection head 7 becomes large, which further increases costs and has an economical disadvantage.

  In order to compensate for the slight amount of light reaching the light receiving element 3, it is easy to increase the light emission amount of the light emitting element 1. In this case, however, the power consumption increases and an excessive current flows to the light emitting element 1. Thus, there arises a problem that the life of the light emitting element 1 is shortened. Furthermore, a means for amplifying the signal in the signal processing circuit is also conceivable. However, this method also increases the electric noise component, which is not a practically effective means and affects the position detection accuracy, which is not preferable.

  Does any of the above measures such as adoption of the lens, enlargement of the light receiving area, increase of the light quantity of the light emitting element 1, and improvement of the signal amplification factor in the signal circuit section on the light receiving element 3 lead to significant improvement in characteristics? Or, variation in characteristics becomes large.

  Next, the method using the light shielding means of FIGS. 26 and 27 prevents the light of the bias component, which is one of the problems in the above-described prior art, and has a great improvement effect. However, when these light shielding means are used, as shown in the graph of FIG. 29, the output voltage V of the analog output reflection type sensor corresponds to the distance G between the reflection type sensor and the reflection sample to be measured. Change.

  That is, the individual reflection type sensors have different positions up to the reflection sample shown in FIG. 27 depending on the mounting position of the light emitting element 13 and the light receiving element 14 and the variation in the position of the light shielding wall 18 disposed between them or the variation in the light receiving sensitivity. The output voltage V with respect to the distance d is not equal. That is, the output voltage obtained by the individual difference is a variable value such as v1, v2, and v3 as shown by the vertical axis in FIG.

  In addition, when used in an area of distance G1 or less, the distance sensitivity between the reflective sensor and the reflective sample is increased, so use in such a close distance area must be avoided in practice. Only an extra space area will be required.

  Furthermore, since a light-shielding body as a light-shielding means is disposed at an intermediate position between the light-emitting element 13 and the light-receiving element 14, the interval between the light-emitting element 13 and the light-receiving element 14 must be increased, and the mounting of the element The area increases and hinders downsizing of the reflective sensor. In addition, an increase in cost due to the use of the light shielding means is inevitable.

  The object of the present invention is to solve the above-mentioned problems, and to prevent the diverging light from the light source from being totally reflected at the boundary surface with the outside of the package without using the light shielding means and to be incident on the light receiving element. It is to provide a sensor.

  Another object of the present invention is to provide a reflective sensor that improves the S / N as a sensor signal by increasing the light intensity of an effective reflected light beam from the object to be measured.

  Still another object of the present invention is to provide a reflective sensor that improves signal characteristics in a close distance region with a device under test and ensures stable quality and reliability with little variation in characteristics.

  In order to achieve the above object, the technical feature of the reflective sensor according to the present invention is a reflective sensor in which a light emitting element and a light receiving element disposed on a substrate are covered with a transparent member, and is emitted from the light emitting element. Among the light rays, a light receiving region by the light receiving element is provided closer to the light emitting element than a light ray that is totally reflected at the boundary surface with the outside of the transparent member and returns into the transparent member.

The technical feature of the reflective sensor according to the present invention is a reflective sensor in which a light-emitting element and a light-receiving element are juxtaposed on a substrate and covered with a transparent member, and a boundary surface between the substrate and the outside world is defined. The transparent member has a refractive index Ni, an external medium refractive index No, a distance from the light emitting region of the light emitting element to the boundary surface D1, and a distance from the light receiving region of the light receiving element to the boundary surface D2. When
R = D1 / tan {sin ⁻¹ (No / Ni)} + D2 / tan {sin ⁻¹ (No / Ni)} The light reception is located inside a circle centered on the light emitting region of radius R determined by the above formula. The area is arranged.

According to the reflective sensor of the present invention, the following effects can be obtained.
(1) Since a light-shielding member between the light-emitting element and the light-receiving element is not required, the light-emitting element and the light-receiving element can be mounted close to each other, the mounting area is reduced, the size is reduced, and the light-shielding means is used. Variations in characteristics are eliminated.
(2) Since the number of steps for forming the light shielding function is reduced and the package is further downsized, the production efficiency is greatly improved, the manufacturing cost can be reduced, and the quality and reliability are greatly improved.
(3) By mounting the light emitting element and the light receiving element close to each other, it is possible to receive the emitted light beam in the vicinity of the optical axis among the light beams from the light emitting element, so that the S / N of the sensor signal is improved. In addition, the light use efficiency is improved, the driving current of the light emitting element is reduced, and low power consumption is effective.
(4) Compared with the conventional method using the light shielding means, the gap characteristics are greatly improved, and an effective sensor signal can be obtained even in the state of being close to the object to be measured.

1 is a schematic configuration diagram of a reflective encoder according to Embodiment 1. FIG. It is sectional drawing before joining of a reflective scale. It is sectional drawing of a reflection scale. It is a top view of the main components of a detection head. It is explanatory drawing of a current confinement type light emitting element. It is a signal processing circuit diagram of a reflective encoder. It is explanatory drawing of a light beam path. It is the illumination intensity distribution figure in PL section with respect to the distance from a light ray, and an illumination intensity graph figure. It is sectional drawing of a simulation model. It is an illuminance distribution diagram. It is explanatory drawing of the optical path by the difference in the gap of a reflective encoder. It is a graph of the illumination intensity when the gap of a light emitting element is used as a parameter. It is a graph of the relationship between internally reflected light and effective light. It is the graph which compared the gap characteristic of the reflective encoder of an Example, and the gap characteristic of a conventional system. It is sectional drawing of the simulation model of Example 2. FIG. It is an illuminance distribution diagram. 6 is a cross-sectional view of a simulation model of Example 3. FIG. It is explanatory drawing of an optical path. It is an illuminance distribution diagram. 6 is a cross-sectional view of a simulation model of Example 4. FIG. It is an illuminance distribution diagram. FIG. 10 is an illuminance distribution diagram of Example 5. It is a perspective view of the conventional reflective encoder. It is the XZ sectional view. It is the YZ sectional view. It is a perspective view of another conventional reflective encoder. FIG. It is sectional drawing to which a part of FIG. 25 was expanded. It is a graph of the output voltage with respect to the gap of another conventional reflective encoder.

  The present invention will be described in detail based on the embodiment shown in FIGS.

  FIG. 1 is a schematic configuration diagram of the embodiment. A reflection scale 21 on which a lattice with equal intervals is formed is fixed to a moving object to be measured and is movable in the X-axis direction that is a lattice arrangement direction. A detection head 22 is arranged facing the reflection scale 21.

  The detection head 22 includes a light emitting element 23 composed of an LED chip, a light receiving element 24 having a photodiode array as a light receiving portion, a semiconductor element composed of a photo IC chip 26 incorporating a signal processing circuit unit 25, a substrate 27 on which these are mounted, and the like. It is comprised by.

  As shown in FIG. 2, the reflective scale 21 includes a pattern forming sheet 31 and a reflective layer forming portion sheet 32. The pattern forming sheet 31 is, for example, a transparent PET film for industrial photoengraving film, has a thickness of about 0.1 to 0.2 mm, and is subjected to an exposure / development process by the emulsion layer of the industrial photoengraving film. Necessary patterns are formed. On the base material portion 31a of the pattern forming sheet 31, a pattern composed of the non-reflecting portion 31b and the light transmitting portion 31c of the light absorbing portion is alternately provided.

  On the other hand, in the reflection layer forming sheet 32, a reflection layer 32b made of a vapor deposition film is formed on the lower surface of the reflection layer 32a made of a PET film as a base material. The reflective scale 21 has a structure in which the pattern forming sheet 31 and the reflective layer forming sheet 32 are joined together by an adhesive layer 33 made of a transparent adhesive as shown in FIG.

  FIG. 4 is a plan view of the light emitting element 23 and the light receiving element 24 which are main components of the detection head 22. The light emitting element 23 is a point light emitting LED having a current confinement structure, the effective light emitting region S1 is a red LED having a circular light emitting window of about φ80 μm and an emission wavelength of 650 nm.

  As one countermeasure for preventing light from the light emitting element 23 from directly entering the light receiving region of the light receiving element 24, a current confining type LED chip is used without using a normal LED chip formed by epitaxial growth as the light emitting element 23. Is used. As shown in FIG. 5, the intensity distribution of the emitted light is completely different between the normal LED chip T shown in (a) and the current confinement type light emitting element 23 shown in (b). In the normal LED chip T, The amount of light emitted in the lateral direction is large, and there is a high possibility that the light is directly incident on the light receiving region. On the other hand, in the current confinement type light emitting element 23, it is unlikely that the light is concentrated and emitted in one forward direction and the light is directly incident on the light receiving region.

  As shown in FIG. 4, a photo IC chip 26 is disposed in the vicinity of the light emitting element 23. The photo IC chip 26 includes a light receiving region S2 formed by a light receiving element 24 disposed on the side close to the light emitting element 23 and a signal processing circuit unit 25. In the light receiving region S2, 16 photodiodes 24a, 24b, 24c, 24d,..., 24m, 24n, 24o, 24p are arranged at equal intervals as the light receiving element 24 in the horizontal direction.

  The photodiodes 24a, 24e, 24i, and 24m are electrically connected, and this set is referred to as a phase, the set of photodiodes 24b, 24f, 24j, and 24n is referred to as b phase, and so on.

  When each of the a-phase, b-phase, c-phase, and d-phase photodiode groups receives light, it outputs a photocurrent corresponding to the amount of light. As the reflection scale 21 moves, the a-phase to d-phase photodiode group outputs a current that varies with a phase relationship of 90 degrees for the b-phase, 180 degrees for the c-phase, and 270 degrees for the d-phase. .

  In the signal processing circuit unit 25 on the photo IC chip 26, the output current is converted into a voltage value by a current-voltage converter, and thereafter, differential components of a phase and c phase and b phase and d phase are respectively obtained by a differential amplifier. Are obtained, and A and B phase displacement output signals having a 90 ° phase shift are output.

  FIG. 6 shows the signal processing circuit unit 25, which includes a light emitting circuit 41 of the light emitting element 23 and an analog signal processing unit 42. Based on the A and B phase analog signals from the analog signal processing unit 42, a position calculation unit 43 is provided that calculates the amount of movement of the reflection scale 21 to obtain the position of the measurement object.

  The first stage amplifiers 44, 45, 46 and 47 are I / V amplifiers for current-voltage conversion of photocurrents generated in the photodiode groups of the a-phase, b-phase, c-phase and d-phase, and the potential of Vf1 is changed. As a reference, potentials V1, V2, V3, and V4 are generated.

  From the a-phase and c-phase photodiode groups, an A-phase signal with Vf2 as a bias potential is obtained by a differential output amplifier 48 that obtains the difference between the outputs V1 and V3. Similarly, the outputs V2 and V4 are differentially amplified by the differential output amplifier 49 from the b-phase and d-phase photodiode groups to obtain a B-phase signal.

  The output signals VA and VB from the analog signal processing unit 42 are superimposed on the AC components Va and Vb, respectively, and output to the position calculation unit 43. The position calculation unit 43 counts the signal peak from the output signal of the A phase (VA = Va + Vf2) or B phase (VB = Vb + Vf2), and is formed on the light receiving region S2 by the reflected diffracted light from the reflection scale 21. Get the number of interference fringes. By multiplying the pitch of the interference fringes by the counted number, the amount of movement of the reflection scale 21 is calculated.

  Furthermore, by calculating the phase angle between the A phase and the B phase based on the AC component of the output signals of the A phase and the B phase, it is possible to calculate the amount of movement below the interference fringe pitch.

  FIG. 7 is an explanatory diagram of an optical path of a light beam in a state cut by the S plane shown in FIG. In addition to the light emitting element 23 and the light receiving element 24, the detection head 22 is disposed on the substrate 27, a light-transmitting sealing resin 51 sealed so as to cover the light emitting element 23 and the light receiving element 24, and the sealing resin 51. The transparent glass 52 is provided. Since the sealing resin 51 and the transparent glass 52 have substantially the same refractive index, they can be regarded as optically substantially integrated members, and the boundary line between them can be ignored.

  The flat reflective scale 21 is irradiated with the divergent light from the light emitting element 23, and the interference fringes are formed on the light receiving region S 2 of the photo IC chip 26 by the reflected diffracted light from the reflective scale 21.

  As shown in FIG. 7, the detection head 22 and the reflection scale 21 are arranged with a gap G therebetween. Assuming that the pitch of the reflection scale 21 is Ps, interference fringes having a period (Pf = 2 × Ps) twice the pitch Ps are formed on the light receiving region S2. The movement of the interference fringes accompanying the movement of the reflection scale 21 is obtained as A-phase and B-phase analog signals as displacement signals by the signal processing circuit unit 25 described above.

  FIG. 7 shows representative light rays L0, La, and Lb related to the present embodiment among the light rays emitted from the light emitting element 23. FIG. The light beam L0 indicates a group of light beams that are refracted and transmitted by the boundary surface 53 and reflected by the reflection scale 21 among the light beams emitted from the light emitting element 23, and finally guided to the light receiving region S2. It becomes effective light to obtain.

  On the other hand, a light beam La is a light beam that is emitted from the light emitting element 23 and totally reflected by the boundary surface 53 and propagates in the package. The light beam La is noise light that is not related to the sensor signal light and is not to be received with respect to the effective light corresponding to the sensor signal of the light beam L0 described above. When incident, the S / N of the sensor signal will decrease. In addition, the light beam Lb is emitted outward without passing through the boundary surface 53 and reaching the reflection scale 21, so that there is almost no influence on the measurement accuracy and the like.

  In this embodiment, the position of the light receiving region S2 of the light receiving element 24 is determined using the light emitting region S1 of the light emitting element 23 as a reference position so that unnecessary light beam La does not enter the light receiving element 24.

  FIG. 8 shows the result of simulating the illuminance distribution of the reflected light from the boundary surface 53 on the PL cross section shown in FIG. 7 on a wide plane including the light receiving region S2. In this simulation, the reflection scale 21 is removed so that the effective light component from the reflection scale 21 does not overlap the observation plane (PL cross section).

  In FIG. 8A, the light emitting area S1 is located at the position indicated by the white square in the center of the illuminance distribution, and the position corresponding to the left light receiving area S2 is indicated by a dotted line. In this illuminance distribution diagram, a ring-shaped bright portion which is a white portion indicates a portion where the illuminance is high due to a reflected light from the boundary surface 53, and a dark portion which is a black portion indicates that the illuminance is low. In particular, a region exhibiting high illuminance is distributed in a ring shape around the light emitting region S1 of the light emitting element 23.

  FIG. 8B shows an illuminance profile in XZ including the centers of the light emitting element 23 and the light receiving element 24. From this illuminance profile, there is a low illuminance area in the inner area of the radius Ri with the light emitting area S1 as a reference. By arranging the light receiving area S2 in this area, the influence of unnecessary light rays can be avoided without using a light shielding means. It is possible to obtain a sensor signal that is not received. Thus, without using a conventional light shielding means, the light receiving region S2 can be installed in the low illuminance region, and an effective reflected light beam from the object to be measured can be obtained with a high S / N.

  In FIG. 8B, avoid the annular zone formed by the high-intensity total reflection light at the boundary surface 53, and not only inside (<Ri) but also outside the high-illuminance region by the high-intensity reflection light. It is also possible to arrange the light receiving region S2 at (> Ro).

The arrangement condition of the light receiving region S2 is expressed by the package main dimensions. In FIG. 7, the refractive index of the sealing resin 51 is Ni, the refractive index of the package external environment is No, the distance from the light emitting region S1 to the boundary surface 53 is D1, the distance from the light receiving region S2 to the boundary surface 53 is D2, and the total reflection region Let Rmax be the radius. The radius Rmax is determined by the radial position with the position where the total reflected light beam reflected at the boundary surface 53 exceeding the critical angle is irradiated as the reference of the light emitting region S1, as shown in the equation (1).
^{Rmax = D1 / tan {sin -1} (No / Ni)} + D2tan {sin -1 (No / Ni)} ··· (1)
Since the illuminance shows the maximum value at the radius Rmax, the arrangement condition of the light receiving region S2 is a position inside the illuminance peak position. If the area where the intensity level of the reflected light can be arranged with a threshold value of about 15% of the total reflected light intensity is determined, the radius Ri of the circular area where the light receiving area S2 can be arranged is expressed by Expression (2).
Ri≈Rmax × 0.85 (2)
On the other hand, when paying attention to the effective ray L0, the effective ray L0 is inclined from the principal ray having the maximum intensity at an angle θ0 with respect to FIG. In order to obtain more intensity as effective light from the reflection scale 21, it is advantageous to use light rays closer to the principal ray axis of the light emitting element 23. For this purpose, the value of the angle θ0 can be reduced by bringing the light receiving region S2 close to the light emitting region S1, leading to an improvement in the S / N of the sensor signal.

  As described above, the means applied in the present embodiment is arranged so that the light emitting region S1 and the light receiving region S2 are arranged as close as possible for the above reasons, and within the radius Ri while avoiding the annular region indicating the high illuminance region. The following conditions are established. (A) Height D1 and D2 of the boundary surface 53 with respect to the light emitting element 23 and the light receiving element 24, (b) mounting position of the light receiving element 24, (c) arrangement of the light receiving region S2 on the light receiving element 24, (d) light receiving region The shape of S2, the light receiving area, and (e) the refractive index of the material of the boundary surface 53 are appropriately determined.

  As specific numerical examples in this embodiment, D1 = D2 = 0.70 mm, Ni = 1.54 (epoxy resin), No = 1.00 (air), and Ri≈ 1.05 mm. The light receiving region S2 has a rectangular shape of 0.5 × 1.0 mm, and the chip interval between the light emitting element 23 and the light receiving element 24 is 0.2 mm.

  FIG. 9 is a cross-sectional view of the simulation model described above, and FIG. 10 shows an illuminance distribution diagram on the observation plane PL by superimposing the effective reflected light from the reflection scale 21 and the reflected light from the boundary surface 53. Yes. It can be seen that the scale pattern of the reflective scale 21 is projected into the annular zone in the high illuminance region, and the sensor signal is obtained with a high S / N.

  In FIG. 11, (a) G = 1.5 mm, (b) 1.0 mm, (c) 0.5 mm, (d) 0 for the gap G between the reflective scale 21 and the detection head 22 in this embodiment. The optical path when installed at a value of 2 mm is shown. In any of the states (a) to (d), since the totally reflected light beam at the boundary surface 53 is not incident on the light receiving region S2, a good S / N sensor signal is obtained.

  FIG. 12 shows the illuminance distribution on the line connecting the light emitting region S1 and the light receiving element 24. FIG. The horizontal axis indicates the distance in the direction of the light receiving element 24 with the position of the light emitting element 23 as the origin. Two types of illuminance distribution on the line are plotted: (1) effective light from the reflection scale, (2) reflected light from the boundary surface 53, and total reflected light. The results are shown with the gap G between the reflection scale 21 and the detection head 22 as a parameter.

  From the square of distance, the illuminance due to the effective reflected light decreases as the value of the gap G increases. On the other hand, the reflection from the boundary surface 53 and the total reflection light are naturally independent of the gap parameter of the reflection scale 21 and do not change with respect to the change in the gap G.

  FIG. 13 shows the optical S / N of the sensor signal as “effective light / noise light” in the same manner as before, and shows the fluctuation of the S / N with the gap change as a parameter from the result of FIG. As a characteristic to be noted here, in the reflection type sensor using the conventional light shielding means, the effective light beam is kicked by the light shielding means at G = 0.2 mm, so that it is not a practically usable region. . It can be seen that the sensor signal can be obtained with a very high optical S / N in the proximity gap region in the reflective sensor of this embodiment. In addition, even when G = 2.0 mm, since an S / N value of 3 or more is obtained, it can be seen that the effective range of gap fluctuation in which an effective signal is obtained is wide.

  FIG. 14 shows the difference between the gap characteristics of the reflective sensor using such a conventional light shielding means and the gap characteristics in this embodiment. Looking at the graph of the conventional example in FIG. 14A, the distance sensitivity between the reflective sensor and the reflective sample is high when the conventional gap region is used. Therefore, the use in such a close distance area must be avoided in practice, and an extra space area is required accordingly.

  However, in the reflection type sensor according to the present embodiment shown in FIG. 14B, the element interval between light receiving and emitting is reduced, and the light rays near the optical axis of the light emitting element 23 are used. This is an improvement over the conventional method. Since there is no kicking characteristic that occurs due to the light shielding means in the conventional method, the effective signal range in the proximity gap region is widened, and the mounting tolerance is relaxed. In addition, since it can be used in the proximity gap, it is advantageous for miniaturization and space saving.

  In the first embodiment, it is possible to obtain a high S / N sensor signal without using a light shielding unit in the reflective encoder, and the characteristics in the close gap region between the reflective scale 21 and the detection head 22 are greatly improved. Is done. Further, the light use efficiency is improved by mounting the light emitting element 23 and the light receiving element 24 closer than the conventional one, and the current consumption of the light emitting element 23 can be reduced. In addition, it contributes to downsizing and can simultaneously achieve stable quality and lower prices.

  FIG. 15 is a cross-sectional view of the simulation model of the second embodiment. The height of the boundary surface 53 is larger than that of the first embodiment, and the annular radius Rmax indicating the high illuminance region by total reflected light is increased. ing. Specifically, D1 = D2 = 0.90 mm, Ni = 1.54 (epoxy resin), and No = 1.00 (air). From these values, Ri≈1.45 mm.

  As a result, as shown in the illuminance distribution diagram of FIG. 16, the allowable circle that can be arranged is enlarged, and the light receiving area of the light receiving region S2 can be made larger than in the case of the first embodiment. For example, in this case, it is rectangular and can be enlarged to about 0.7 × 1.4 mm.

  FIG. 17 is a cross-sectional view of the simulation model of Example 3. Regarding the height of the boundary surface 53 with respect to Example 1, the values of the height D1 on the light emitting element 23 side and the height D2 on the light receiving element 24 side are shown. Have different values. Specifically, D1 = 0.3 mm, D2 = 0.7 mm, Ni = 1.54 (epoxy resin), and No = 1.00 (air). From these values, Ri≈0.85 mm.

  In Example 3, the upper part of the light emitting element 23 is covered with the sealing resin 51 and the transparent glass 52 up to a height of 0.3 mm, and the upper part is a cylindrical shape having a diameter of 0.6 mm and a depth of 0.4 mm. It has a cut-out shape.

  FIG. 18 is an optical path diagram of the effective reflection light and the total internal reflection light of Example 3. The light receiving region S2 is disposed at a position where the totally reflected light does not enter.

  As shown in the illuminance distribution diagram of FIG. 19, the allowable circle that can be arranged is reduced, and it becomes difficult to arrange the light receiving region S2 inside the allowable circle as in the first and second embodiments. However, in this case, the same effect as in the first and second embodiments can be obtained by arranging the light receiving region S2 outside the circle.

  Since the mounting area is large, the configuration is disadvantageous for downsizing, but the degree of freedom of the arrangement position of the light receiving region S2 on the light receiving element 24 is increased, and the size of the light receiving portion is less limited. In such a point, when it is arranged inside the allowable circle in the first and second embodiments, an impossible arrangement is possible.

  FIG. 20 is a cross-sectional view of the simulation model of the fourth embodiment. As in the third embodiment, the height of the boundary surface 53 is a value of the height D1 on the light emitting element 23 side and the height D2 on the light receiving element 24 side. Have different values. Specifically, D1 = 0.3 mm, D2 = 0.7 mm, Ni = 1.54 (epoxy resin), and No = 1.00 (air). From these values, Ri≈0.85 mm.

  As shown in the illuminance distribution diagram of FIG. 21, in this case, the illuminance distribution is complicated. However, by arranging the light receiving region S2 at the position indicated by the dotted line, the same effect as in the first embodiment can be obtained.

  FIG. 22 is an illuminance distribution diagram of the fifth embodiment, in which the light receiving shape of the light receiving region S2 is changed with respect to the first embodiment. The height of the boundary surface 53 is based on a model in which the height D1 on the light emitting element 23 side and the height D2 on the light receiving element 24 side are set to the same value. Specifically, D1 = 0.7 mm, D2 = 0.7 mm, Ni = 1.54 (epoxy resin), and No = 1.00 (air). From these values, Ri≈1.05 mm.

  When the light receiving area S2 is arranged as effectively as possible within the radius Ri, the shape of the light receiving area S2 is formed in a fan shape or an arc shape along an allowable circle. Thereby, substantially more effective reflected rays from the reflection scale 21 can be taken into the light receiving region S2. As a result, the S / N of the sensor signal can be improved.

  In addition, although the surface shape of the boundary surface 53 in this embodiment can be variously modified, the light emission is performed so that the totally reflected light from the boundary surface 53 does not enter the light receiving region S2 regardless of the surface shape of the boundary surface 53. The position of the light receiving element 24 relative to the element 23 and the height of the boundary surface 53 can also be changed.

  In the above description of the embodiment, the case of the reflective encoder has been mainly described. However, the present invention can be substantially applied to a reflective photointerrupter or the like.

DESCRIPTION OF SYMBOLS 21 Reflective scale 22 Detection head 23 Light emitting element 24 Light receiving element 25 Signal processing circuit part 26 Photo IC chip 27 Substrate 51 Sealing resin 52 Transparent glass 53 Interface surface S1 Light emitting area S2 Light receiving area

In order to achieve the above object, a reflective sensor according to the present invention includes a substrate, a light-emitting element provided on the substrate and having a light-emitting region that emits light, and a light-emitting element provided on the substrate and emitted from the light-emitting element. In a reflective sensor having a light receiving element having a light receiving region for receiving light reflected by a reflective sample and a light transmitting part for sealing both the light emitting element and the light receiving element, the light transmitting part is made of resin. A transparent resin part that seals both the light emitting element and the light receiving element; and a transparent glass formed on the transparent resin part. The light receiving region is emitted from the light emitting element and transmits the light. It is characterized by being provided at a position closer to the light emitting element than a region irradiated with light totally reflected at the boundary surface between the portion and the outside . Here, it is desirable that the refractive index of the transparent resin portion and the refractive index of the transparent glass are substantially the same.
The reflective sensor according to another aspect of the present invention is a reflective sensor in which a light emitting element and a light receiving element disposed on a substrate are covered with a transparent member, and the light receiving element is emitted from the light emitting element. It is characterized in that the light beam is disposed on the light emitting element side of the light beam that is totally reflected at the boundary surface with the outside of the transparent member and returns to the substrate side.

The apparatus according to the present invention includes an object to be measured, a scale fixed to the object to be measured, a light emitting element that emits light to the scale, and a light receiving element that receives light from the scale. And a reflection type sensor as described above.

According to the reflective sensor of the present invention, the following effects can be obtained.
Since a light-shielding member between the light-emitting element and the light-receiving element is not required, the light-emitting element and the light-receiving element can be mounted close to each other, the mounting area is reduced and the size is reduced, and the characteristics caused by the light-shielding means are reduced. There is no variation .
Compared to the conventional method using the light shielding means, the gap characteristics are greatly improved, and an effective sensor signal can be obtained even in the state of being close to the object to be measured.

Claims (7)

  A reflective sensor in which a light-emitting element and a light-receiving element disposed on a substrate are covered with a transparent member, and the light emitted from the light-emitting element is totally reflected at the boundary surface with the outside of the transparent member, and A reflection type sensor, wherein a light receiving region by the light receiving element is provided on the light emitting element side with respect to a light beam returning into the transparent member.   The reflective sensor according to claim 1, wherein the light emitting element is an LED having a current confinement structure.   The reflective sensor according to claim 1, wherein the transparent member is provided with a transparent resin and a transparent glass.   The reflective sensor according to claim 1, wherein a step is provided at an intermediate position between the light emitting element and the light receiving element on the boundary surface.   The reflective sensor according to claim 1, wherein the shape of the light receiving region is a sector shape or an arc shape. A reflective sensor in which a light-emitting element and a light-receiving element are juxtaposed on a substrate and covered with a transparent member, the refractive index of the transparent member having a boundary surface with the external world parallel to the substrate being Ni, and the refractive index of the medium of the external world When the rate is No, the distance from the light emitting region of the light emitting element to the boundary surface is D1, and the distance from the light receiving region of the light receiving element to the boundary surface is D2,
R = D1 / tan {sin ⁻¹ (No / Ni)} + D2 / tan {sin ⁻¹ (No / Ni)} The light reception is located inside a circle centered on the light emitting region of radius R determined by the above formula. A reflective sensor characterized in that a region is arranged.   7. The reflection type sensor according to claim 6, wherein the light receiving element has a light receiving portion as a photodiode array, and is constituted by a photo IC together with a signal processing unit including a plurality of first-stage amplifiers and differential amplifiers.