JPS6020784B2 - Pattern reading method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a pattern reading method, and is particularly suitable for application to, for example, an optical encoder, a pattern scanning device, etc. that detects whether a Z pattern to be read matches a predetermined reference pattern. It is something that has been trained.

For example, in a rotary Z-encoder used to control a rotating system, a black and white pattern to be read 2 is used, as shown in Figure 6.
The rotary plate on which is printed is rotated, the light emitting section 8 emits light, and the light transmitted through the pattern to be read 2 is received by the light receiving section 9.

The light receiving section 9 has a function of generating an electric signal in response to the pattern 2 to be read. Since the pattern to be read 2 is made with a highly accurate constant pitch, the generated electric pulses accurately reflect the rotational speed of the rotary plate 1. However, this pattern 2 to be read often includes minute errors, and in order to eliminate this, an optical system as shown in FIG. 1 is used to generate pulses corresponding to the average pitch. In FIG. 1, the light emitting section 8 is provided on the same side as the light receiving section 9, but they are essentially the same device. The light receiving section 9 in FIG. 6 includes the lens system 4 in FIG. 1, the mask 6,
A light sensor 5 is built-in. As shown in FIG.
An illumination light 3 is irradiated onto the object, and the reflected light is inputted through a lens system 4 to an image sensor 5 having a photodetector configuration.

A mask 7 having an aperture 6 formed therein is arranged between the lens system 4 and the optical sensor 5 as a reference pattern to be compared with the pattern to be read 2 . However, when the pattern formed by the bright part of the pattern to be read 2 and the aperture part of the mask 7 match, the detection output signal DT obtained by the image sensor 5 becomes maximum.

In order to obtain the maximum output in this way, in an encoder designed to take a regular striped pattern as the pattern to be read 2, it is sufficient to select a reference pattern having the same regular striped pattern as the mask 6, and thus the pattern to be read is can detect what is. Incidentally, an encoder that reads regular striped patterns has the advantage that even if there is pitch unevenness in the encoder, as long as the mask 7 has a reference pattern with an accurate pitch, the pitch unevenness in the detection signal DT will be extremely small. .

Furthermore, since the mask 7 has a plurality of apertures, the amount of light incident on the image sensor 5 is greater than in the case of a single slit, which has the advantage of making detection easier. However, in the case of relying on the method shown in FIG. 1, high-precision processing is required for manufacturing the mask 7, and it is inevitable that the position adjustment of the mask 7 with respect to the reflected light becomes complicated.

In addition to this, when the mask 7 requires halftones (in other words, when a pattern with halftones must also be detected), there is a problem that the mask 7 cannot be manufactured easily. be. In consideration of the above points, the present invention is an attempt to solve the disadvantages of the conventional methods all at once while making use of the advantages of the above-mentioned conventional methods without impairing them. An interference or diffraction pattern is generated, and based on the correlation with this interference or diffraction pattern, it is possible to detect whether the pattern to be read matches a reference or not.

An example of the present invention will be described in detail with reference to the drawings below.
, reference numeral 11 denotes a pattern to be read formed on the rotary plate 12, which includes a bright pattern section 11a and a daylight pattern section 11b.
It becomes.

An interference pattern is formed on the pattern to be read 11 by the interference light 14 from the interference light generating section 13.

Here, the interference pattern refers to a pattern caused by interference with light, and includes a so-called diffraction pattern. The interference light generating section 13 includes an interference pattern mask 1 having two slits 15 illuminated by the light source light 17.
6, and interference light 14 is formed by the light transmitted through the slit 15. The reflected light 18 resulting from the interference light 14 irradiated onto the rotating plate 12 is applied to the image sensor 20 via the lens system 19, where it is converted into an electrical detection signal DT.

In the interference generating section 13 described above, if the slit interval of the interference pattern mask 16 is d, the period of the interference pattern 11 on the rotating plate 12 is D, and the distance between the rotating plate 12 and the interference pattern mask 16 is L, then D Miyoshi ^……
Bright and dark interference fringes are generated at a position on the surface of the rotary plate 12 (in other words, on the pattern to be read 11) where the relationship [11] holds.

However, ^ is the wavelength of light. Therefore, the distance L between the rotating plate 12 and the interference pattern mask 16 is adjusted so that the pitch of the pattern to be read 11 and the pitch of the interference pattern almost match. Then, when the rotary plate 12 moves in the direction of the arrow 21, if the contrast pattern 11 and the interference pattern match, strong reflected light will be incident on the image sensor 20, and if they do not match, the reflected light will be almost zero. Become. Therefore, according to the detection output DT of the image sensor zero, the pattern 1 is
1 can be read. Note that in order to obtain the interference light 14, it is desirable to use a single-wavelength beam that is intersectable as the light source light 17.

Note that the optical system shown in FIG. 2B may be used instead of the configuration shown in FIG. 2A.

In other words, in the case of FIG. 2A, the interference pattern 14 may be slightly shifted at the periphery of the image, but in order to make the pattern pitch even more accurate, the interference pattern mask 16 is changed as shown in FIG. 2B. The passing light is sent to the original 1 via the lens 25.
2. In this way, when the focal length of the lens 25 is F, the formula {1) becomes D=Teiiri.
‐‐‐‐‐‐‐‐‐‐‐‐‐‐‐■It can be expressed as.

Next, FIG. 3 shows another embodiment of the present invention.

In this case, the interference light generating section 13 causes the light source light 32 emitted from the light source 31 to pass through the half mirror 33 and irradiate it onto the surface of the rotating plate 12, and also reflects the reflected light from the half mirror 33 by the mirror 34 to rotate it. The surface of the plate 12 is irradiated. In this way, an interference pattern is formed by the interference light on the surface of the rotary plate 12.

Next, FIG. 4 shows still another embodiment of the present invention.

In this case, diffracted light is used as the irradiation light for the pattern to be read. In FIG. 4, reference numeral 42 represents a reference pattern generating member, for example, a hologram.

In this case, a laser beam is used as the light source light 41, the light source light 41 is irradiated onto the pattern to be read on the rotating plate 12 via the hologram 42, and the reflected light from the surface of the rotating plate 12 is reflected via the lens system 43. It is detected by the image sensor 44.

In FIG. 4, the size and shape of the irradiation area 45 onto the rotary plate 12 are stored in the hologram 42 in advance.
If the shape of the discussion pixel of the rotary plate 12 changes, it can be easily detected by converting the hologram 42 accordingly. That is, image information can be read reliably and easily by comparing and comparing the hologram memories. However, at this time, high positional accuracy of the hologram 42 is not required, and moreover, it is not affected much by defects in the hologram recording body.

Therefore, the method of FIG. 4 can provide a particularly practical pattern cutting device. Here, if pattern 1
2 is a regular grating pattern, the reference pattern generating member 42 can use a normal diffraction grating.

In this case, the member 42 may be a reflection type diffraction grating or a reflection type hologram. As described above, according to the present invention, an interference or rotational pattern is used as a reference pattern for detecting a pattern to be read.
The pitch of the interference or rotational pattern is extremely accurate because it is produced by physical development. Therefore, the pattern to be read can be read extremely easily and with extremely high accuracy without preparing a highly accurate mask as in the conventional case. Furthermore, when the hologram 42 is used as described above with reference to FIG. 4, it becomes easy to project a half-tone pattern, and therefore the readable range of the pattern to be read can be further expanded.

As shown in FIG. 5, the halftone pattern projection is such that the light intensity is strongest in the darkly expressed peripheral area 51, and the intensity of the light is gradually weakened from this peripheral area 52 toward the center. This means using irradiated light that is

If the irradiation light shown in FIG. 5 is used in the system shown in FIG. 4, it is possible to provide a detection result in which the information on the periphery of the square aperture included in the pattern to be read is greatest.

[Brief explanation of the drawing]

1 and 6 are systematic diagrams showing a conventional pattern reading method, FIGS. 2A and 2B are systematic diagrams showing an example of a pattern reading method according to the present invention, and FIGS. FIG. 4 is a systematic schematic diagram showing another example of the present invention, and FIG. 5 is a zero schematic diagram showing irradiation light that can be used in the system of FIG. 1, 12... Original, 2, 11... Pattern to be read, 3... Illumination light, 4, 19, 43... Lens system, 5, 20, 44... Image sensor, 7...Mask, 13...Interference light generating section, 14...Interference light, 15...Slit, 16...Mask for interference pattern, 17, 32 , 41... Light source light, 18... Reflected light, 31... Light source, 33
...Half mirror, 34...Mifu,
42...Reference pattern generation member (hologram)
, 45...irradiation area. Figure 1 Figure 2 A Line 2 Figure B Figure 3 Groove 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. Interfering or diffracting light irradiated onto the pattern to be read to generate an interference or diffraction pattern that is substantially the same as the pattern to be read, and irradiating this interference or diffraction pattern onto the pattern to be read to eliminate the interference. Alternatively, a pattern reading method characterized in that the pattern to be read is read depending on whether a diffraction pattern matches the pattern to be read.