JP2007218755A - Alignment angle inspection device of photoelectric encoder - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To evaluate alignment deviation in the rotation direction easily, quantitatively and highly accurately. <P>SOLUTION: This photoelectric encoder for detecting relative displacement between a scale 10 and a detection head 20 is provided with inspection lattices 42a, 42b having plus and minus angle offset θof to reference lattices 26, 12, and angle deviation between the lattices is detected based on a light receiving signal acquired by interaction between an inspection lattice and a reference lattice or a reference lattice for inspection disposed at the same angle as the reference lattice. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an alignment angle inspection apparatus for a photoelectric encoder for detecting a relative position between a scale and a detection head, and in particular, an evaluation of a rotational direction alignment between a light receiving element and a detection substrate, and an evaluation of a rotational direction alignment between a scale and a detection head. It is related with the alignment angle test | inspection apparatus of the photoelectric encoder suitable for using for this.

  Among the photoelectric encoders for detecting the relative displacement between the scale 10 and the detection head 20, in the three-grating reflective encoder configuration as shown in FIG. 1, the light source 22 generates a COG (Chip On Glass) substrate or the like. Light reception in which a third grating 29 is integrally formed to receive light that has been subjected to the action of the first grating 26 on the detection substrate 24 and the second grating (also referred to as a scale grating) 12 on the scale 10. An element array (PDA) chip 28 is mounted on the detection substrate 24. In addition, as shown in FIG. 2, the first grating 26 is formed as a pattern on the detection substrate 24. Accordingly, the relative positions of the first grating 26 and the PDA chip 28 are shifted in X, Y, and θ as shown in FIG. 3 according to the mounting position accuracy.

  When the relative angle between the PDA chip 28 and the first grating 26 is deviated, as shown in FIG. 3, the signal amount decreases or a signal of another phase enters at the end of the PDA chip 28, and the direct current component increases. Accuracy deteriorates. The finer the scale scale pitch, the greater the effect of misalignment. For example, in a 4/4 μm scale where both bright stripes and dark stripes are 4 μm, a long rotation error of 0.2 ° in the moire direction (θ) An inclination of about 3.5 μm per 1 mm occurs, and a positional shift that cannot be ignored in terms of characteristics occurs. Therefore, the alignment of the grid is very important.

  On the other hand, although not a photoelectric encoder, Patent Documents 1 and 2 describe an alignment technique for an exposure mask using comb-like marks.

JP-A-3-262901 JP-A-4-7814

  However, it was not suitable for evaluating the rotational alignment of the photoelectric encoder.

  Note that the deviation in the X and Y directions can be evaluated by the degree of overlap of the pad portions 30 shown in FIG. 4, but in order to quantitatively determine the rotation direction, the deviation amounts at a plurality of points must be measured. .

  Further, as shown in FIG. 4, since there are solder bumps 32 between the detection substrate 24 and the PDA chip 28 and they are separated by several tens of μm, it is difficult to focus on both at the same time with a high magnification microscope. At low magnifications, the resolution of reading is poor, and it is difficult to obtain an accurate position error for determining the adjustment amount.

  The present invention has been made to solve the above-described conventional problems, and it is an object of the present invention to make it possible to easily, quantitatively and accurately evaluate misalignment in the rotational direction.

  In the photoelectric encoder for detecting the relative displacement between the scale and the detection head, the present invention provides an inspection grating having positive and negative angular offsets with respect to a reference grating, and the inspection grating and the reference A photoelectric system characterized in that an angular deviation between the gratings can be detected based on a received light signal obtained by the interaction of a grating or an inspection reference grating arranged at the same angle as the reference grating. The problem is solved by an encoder alignment angle inspection device.

  The reference grating is a first grating formed on the detection substrate, and an angular deviation between the first grating and the light receiving element is detected.

  Further, the reference grating is used as a scale grating to detect an angular deviation between the scale and the detection head.

  The inspection grating is a light receiving element array.

  The present invention also provides a photoelectric encoder comprising the alignment angle inspection apparatus.

  Further, the present invention provides a chip mounting apparatus in which the mounting angle of the light receiving element chip on the detection substrate is controlled by the output of the alignment angle inspection apparatus.

  According to the present invention, the amount of angular deviation between the gratings can be determined based on the received light signal obtained by the interaction between the inspection grating and the reference grating or the inspection reference grating arranged at the same angle as the reference grating. Highly accurate and quantitative measurement can be easily performed.

  Therefore, it is possible to perform the positional deviation inspection work between the PDA chip and the detection substrate, which has been conventionally performed under a microscope, only by monitoring the electric signal, and the time required for the assembly process can be shortened while improving the assembly accuracy.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  In the first embodiment of the present invention, the present invention is applied to the rotational direction alignment evaluation of the PDA chip 28 and the detection substrate 24. As shown in FIG. 5, the first lattice (on the detection substrate 24) is a reference lattice. 16), a main signal detecting light-receiving element integrally formed with the third grating 29 on the PDA chip 28, and an angular offset ± θof with respect to the first grating 16 on the PDA chip 28. The inspection PDAs 42a and 42b are composed of two gratings each having a light receiving portion, and the inspection PDAs 42a and 42b detect the signals of the first grating for inspection extended from both sides of the first grating 16, and the first grating 16 16 and a signal corresponding to the angular deviation between the PDA chip 28 are output.

  In the present embodiment, one PDA 42a and 42b for inspection each having an offset angle ± θof with respect to the first grating 26 is arranged in the PDA chip 28, and at a position overlapping with the PDAs 42a and 42b for inspection, A feature is that a pattern of the first lattice 26 serving as a reference is arranged. Since the other points are the same as the conventional ones, detailed description thereof is omitted.

  Thereby, when there is no rotational deviation, the light receiving areas of the left and right inspection PDAs 42a and 42b are the same, but when a rotational deviation occurs, the difference between the left and right light receiving areas becomes large. Accordingly, if the output of the inspection PDAs 42a and 42b can be drawn from the terminals of the detection substrate 24, and the output difference between the right and left inspection PDAs 42a and 42b is monitored by applying a predetermined amount of light, the amount of rotational deviation can be determined. .

  Here, it is desirable that the offset angle θof be 8 ° or less, preferably 5 ° or less, in which the change of the light receiving area = (signal amount) is large.

As shown in FIG. 6, FIG. 7A shows the result of conceptual calculation of the effective light receiving portion area through which light formed by the rotation amount and the overlap between the gratings can be transmitted. PD offset angle is ± θof, rotation deviation angle is θ, grating width is W, overlap length is L (= W / sin (θof + θ)), and effective light receiving area is S (= L × W = W ² / sinθ) ), One set of effective light receiving area difference is as shown in the following equation.

^{S1-S2 = W 2 / [} 1 / sin (θof + θ) + 1 / sin (-θof-θ)] ... (1)

  Since the optical signal amount is proportional to the effective light receiving area, as shown in FIG. 7B, the change in the signal amount (| S1-S2 |) increases rapidly as the angular deviation increases.

  In actual measurement, as shown in FIG. 8, after the PDA chip 28 is mounted on the detection substrate 24, parallel light is irradiated from the light receiving surface side by the illumination light source 50 and the collimator lens 52. The output signals of the inspection PDAs 42a and 42b on the lower surface on the side are taken out by the evaluation circuit 60 by the output pad 56, the probe 58, etc., and subjected to calculation processing.

  Specifically, the outputs of the inspection PDAs 42a and 42b are input via IV (current / voltage) conversion amplifiers (IVA) 62a and 62b of the evaluation circuit 60, and the difference is calculated by the differential amplifier 64. Based on the data as shown in FIG. 7B acquired in advance, the rotation amount calculator 66 calculates the rotation amount and outputs the result. In this way, if a plurality of chips in the detection substrate 24 are monitored, the overall tendency can be understood and the measurement accuracy can be improved.

  Further, if the offset control of the chip mounting apparatus 72 is electrically performed, the correction value is calculated by the mounting apparatus correction value calculation unit 68, and the rotation amount is supplied to the chip mounting apparatus 72 via the interface (I / F) 70. Can be fed back to the condition setting of the chip mounting apparatus 72, or incorporated into the chip mounting apparatus 72.

  A general optical overlay inspection method can be applied to the feedback method and the sampling method. The same effect can be obtained regardless of whether the PDA or the first grating has the offset angle θof.

  Next, a second embodiment of the present invention applied to a moire check of a separate photoelectric encoder will be described in detail with reference to FIG.

  In this embodiment, instead of the first grating 26, a rotational deviation between the scale grating 12 (scale 10) and the PDA chip 28 (detection head 20) is detected, and the principle is substantially the same as that of the first embodiment. An arithmetic circuit for calculating signals from the inspection PDAs 42a and 42b and a rotation amount alarm are provided.

  Further, when the detection substrate 24 is not a transparent body such as glass, windows 44a and 44b are provided at positions where illumination light to the inspection PDAs 42a and 42b passes, as indicated by broken lines in FIG.

  According to the present embodiment, the rotational deviation of the detection head 20 with respect to the scale grid 12 (scale 10) can be detected and used for position adjustment.

  Not only the inspection patterns (42a and 42b) are placed in the main signal light receiving element, but the inspection pattern and the light receiving element may be separate IC chips.

  Further, a combination of the third grating and a separate light receiving element may be used instead of the light receiving element array.

  In the above embodiment, the present invention is applied to a three-grating reflective encoder, but the application target of the present invention is not limited to this, and the present invention can be similarly applied to a two-grating or transmissive encoder.

Sectional drawing which shows the general structure of the conventional reflective encoder Similarly, a plan view showing the detection substrate Similarly, a plan view showing an example of rotational direction misalignment Similarly, a cross-sectional view showing a PDA chip on a detection substrate The top view which shows the structure of 1st Embodiment of this invention. Plan view showing overlap of slits for explaining the principle of the present invention Diagram showing the relationship between offset angle, area and rotational deviation Block diagram showing a measurement example according to the first embodiment The top view which shows 2nd Embodiment of this invention

Explanation of symbols

10 ... Scale 12 ... Scale lattice (second lattice)
DESCRIPTION OF SYMBOLS 20 ... Detection head 22 ... Light source 24 ... Detection board 26 ... 1st grating | lattice 28 ... Light receiving element array (PDA) chip | tip 42a, 42b ... PDA for test | inspection
58 ... Probe 60 ... Evaluation circuit 66 ... Rotation amount calculation unit 72 ... Chip mounting device

Claims (6)

In the photoelectric encoder for detecting the relative displacement between the scale and the detection head,
An inspection grid with positive and negative angular offsets is provided for the reference grid,
The angle deviation between the gratings can be detected on the basis of the light reception signal obtained by the interaction between the inspection grating and the reference grating or the inspection reference grating arranged at the same angle as the reference grating. An alignment angle inspection device for a photoelectric encoder.   2. The photoelectric encoder according to claim 1, wherein the reference grating is a first grating formed on a detection substrate, and an angular deviation between the first grating and the light receiving element is detected. Alignment angle inspection device.   2. The alignment angle inspection apparatus for a photoelectric encoder according to claim 1, wherein the reference grating is a scale grating and detects an angular deviation between the scale and the detection head.   4. The photoelectric encoder alignment angle inspection apparatus according to claim 1, wherein the inspection grid is a light receiving element array.   A photoelectric encoder comprising the alignment angle inspection device according to claim 1.   5. A chip mounting apparatus, wherein the mounting angle of the light receiving element chip on the detection substrate is controlled by the output of the alignment angle inspection apparatus according to claim 2 or 4.

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