JPH01295114A - Absolute position detector - Google Patents

Abstract

PURPOSE:To shorten the read time of one frame and to improve the response by connecting and reading only lines which include picture elements required to find absolute position information. CONSTITUTION:Signal charges from a photodiode 1 are transferred to vertical shift registers 2D...2U...2E. Head charges of the registers 2D and 2U are supplied to comparing circuits 10D and 10U through charge voltage converting circuits 9D and 9U and their output signals are supplied to an exclusive OR gate 11. The output signal of the gate 11 is supplied to an OR gate 14 through an AND gate 12. When the output signal of the OR gate 14 is 1, a decision circuit 16 transfers signal charges of lines including the head charges of the registers 2D and 2U are transferred to a horizontal shift register 3. Further, when the output signal of the OR gate 14 is 0, signal charges of lines including the head charges of the registers 2D and 2U are swept out through a ground line 4 and discarded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an absolute position detection device suitable for use, for example, in detecting the angle of an arm of an industrial robot or detecting the position of a machine tool when feeding a table.

[Summary of the invention]

In this invention, a code plate on which both a numerical pattern area and a striped pattern area are formed is imaged by a two-dimensional image sensor, and by tilting the arrangement relationship between the code plate and the image sensor, the captured image is In an absolute position detection device that generates a stepped portion at the edge of a striped pattern, detects a position with coarse accuracy from the imaging output of a numerical pattern area, and detects a position with precise accuracy from the stepped portion of the striped pattern, an image sensor By reading out only the lines that include the step part necessary for absolute position detection,
The reading time for one frame is shortened, and the delay time in detecting the absolute position is shortened.

[Conventional technology]

Absolute position detection devices are often used for detecting the angle of industrial robots and the feed position of machine tool tables.
As described in the specification of No. 26, a numerical pattern is formed on a code plate serving as a scale plate, and a striped pattern is also formed, and this code plate is read by a two-dimensional image pickup device composed of a CCD, We have proposed an absolute position detection device that detects a position with coarse precision from a numerical pattern and a position with precision from a striped pattern by processing the output signal of an image sensor.

FIG. 4 shows a schematic configuration of the above-mentioned absolute position detection device, which includes a code plate 20 as a scale plate, and a code plate 20 as a scale plate.
At least one of the image sensors 21 disposed opposite to the image sensor 0 is movable. The code plate 20 has a fifth
As shown in the figure, numerical pattern area 2 showing gray code
2 and a striped pattern area 23 are provided. Gray code is one of the codes that express binary numbers, and is also called alternating binary code or reflective binary code, and has the characteristic that only one bit always changes between two adjacent numbers. are doing. Striped pattern area 23
A plurality of striped patterns P each having a width W are formed parallel to each other and spaced at equal intervals. The arrangement direction Z of these striped patterns P is orthogonal to the extending direction of the pattern P, and the arrangement pitch is Pz. Gray codes in the numerical pattern area 22 are attached corresponding to each pattern P, and by reading these gray codes, the absolute position in the Z direction can be known.

An image sensor 21 disposed facing the code plate 20 described above
is a two-dimensional imaging device using a CCD. code board 2
The direction of relative movement between 0 and the image sensor 21 is parallel to the arrangement direction Z. The axial direction of the image sensor 21 itself is provided so as to have a slight inclination angle θ with respect to the arrangement direction Z. In FIG. 5, the angle between the horizontal and vertical coordinate axes 11 of the image sensor 21 and the vertical axis (■) in the arrangement direction Z is θ.
It is said that

The image sensor 21 is arranged in each pattern area 22 .
23 at the same time, and sends the imaging signal to the detection circuit 24 shown in FIG. The coordinates of a predetermined point are read from the shaped pattern P, as will be described later. These read data are supplied to the coordinate conversion circuit 25. The coordinate conversion circuit 25 calculates absolute position information in the Z-axis direction based on the value of the gray code and the coordinates of a predetermined point of the striped pattern P. That is, according to the Gray code, the pattern P
Positional information with relatively coarse accuracy is obtained using the array pitch Pz as a unit, and by coordinate transformation based on the coordinates of a predetermined point of the pattern P, positional information with even higher accuracy can be obtained.

In addition, in FIG. 4, the LE is connected from behind the code board 20.
Light from a light source 21 such as D is irradiated, and an example is shown in which a so-called transmissive type code plate 20 is used. good.

FIG. 7 shows a part of the image captured by the image sensor 21 in an enlarged manner. The pattern P of the striped pattern area 23 is a video pattern that is binarized for each pixel (cell) S of the image sensor 21. In this case, the image sensor 2
Since the V-axis direction of No. 1 and the arrangement direction Z of the striped pattern P have an angle θ, the edge E of the pattern P has a stepped shape as shown in FIG. This stepped boundary line E occurs at the upper edge Ea and lower edge Eb of the pattern P. Pixels Sal, Sa2, etc. on the stepped portion of the upper edge Ea can be detected as pixels that change from white to black when scanning in the H direction, and pixels Sb1, Sb2, etc. on the stepped portion of the lower edge Eb can be detected as pixels that change from white to black when scanning in the H direction. It can be detected as a pixel that changes from black to white during scanning.

Here, when the coordinates in the H-axis and V-axis directions of the image sensor 21 are expressed in units of the number of pixels S, the coordinates of the pixel Sal at a predetermined stepped portion of the upper edge Ea are (Ha 1.Va 1
), and the coordinates of the pixel Sbl of the stepped portion of the lower edge Eb corresponding to this pixel Sal are (Hbl, Vbl). The coordinates (Hl) of the center position of the line segment connecting these pixels Sal and Sbl.

Vl) is H1=(Ha l+Hbl)/2 V1-(Val+Vbl)/2 becomes.

The point of this coordinate (Hl, Vl) is, as shown in Fig. 7,
It is located on the center line C of the striped pattern P, and the absolute position Zc of this pattern center line C in the Z direction can be read from the gray code.

Furthermore, since each coordinate value is expressed using the number of pixels S as a unit, if each pitch of the pixel S in the H-axis and V-axis directions is Po and Pv, respectively, it becomes a reference point for reading the position of the image sensor 21. Coordinates (Hl, Vl) relative to the origin (0, O)
The actual distance in the H-axis direction is HIP, and in the ■-axis direction is ■IPv. Therefore, the absolute position Z of the origin (0, O) in the Z-axis direction. is the absolute position Zc of the pattern P, each coordinate value H1, Vl, each pitch P, , Pv of the pixel S, and the inclination angle θ, Zo = Z c − (HIPH sin θ + VIPvc
osθ). As a result, in principle, the absolute position can be read with an accuracy of the minimum unit PH5 in θ.

Note that the coordinates of each pixel S are all expressed as integer values, but the coordinates of the center position (Hl, Vl), etc. are values that are integral multiples of 0°5.

[Problem to be solved by the invention]

In the above-mentioned absolute position detection device, since the image sensor 21 reads out all pixels, the readout time for one frame becomes long.
There was a problem that the output delay time of the current position information became long.

If the output delay time is long, the range of use will be limited. The output delay time is expressed by the following formula.

(Output delay time) - % (Exposure time) + (Pixel signal transfer processing communication time) When the image sensor 21 is of an interline type, the order of reading out the charges of each pixel is as follows.

■Transfer the charge of the photosensor diode to the vertical shift register.

■Execute the shift operation of the vertical shift register.

At the same time, the first horizontal line charge is transferred to the horizontal shift register.

■Execute the shift operation of the horizontal shift register.

At the same time, the leading charge is read out.

The above operations are executed in the order shown in FIG. In FIG. 8, Nh indicates the number of horizontal pixels, and Nv indicates the number of vertical pixels. Let T1 be the shift time required for the operation (2), T2 be the shift time required for the operation (2), and T3 be the shift time required for the operation (2), then T1 is sufficiently short compared to T2 and T3 and can be ignored. , the time T required to read out the charges of all pixels of the CCD image sensor 21 is T'; (T2+T3xNh)·Nv.

As an example, if the horizontal shift operating frequency is 10MHz (T
3 = 0.1 μsec), the vertical shift operating frequency is I MHz (T 2 = 1 #5ec), and (30
When reading out 90,000 pixels of 0x300), the readout time T of the frame is approximately 9.3 m, as shown in the formula below.
It will be 5ec.

(1μsec +0.1μsec x300)X30
0 = 9.3 m5ec By the way, when paying attention to the image of the image sensor 21, the portions that provide the information necessary to output absolute position information are only a small portion such as the edges of the striped pattern P. That is, the coordinate values of points that change from white to black or from black to white at the edges of the striped pattern P, and the pixel data values (0 or 1) near the center of each track of the numerical pattern on the horizontal line where the change point is located. ) is required.

Therefore, an object of the present invention is to provide an absolute position detection device that does not read out all pixels but only reads out necessary pixels, thereby shortening the readout time for one frame and improving responsiveness.

[Means to solve the problem]

In this invention, the transfer register 2D is connected to the horizontal shift register 3 of the two-dimensional image sensor 21.

A discrimination circuit 16 is provided at the exit of 2U to determine whether the signal charge is required or not.The output of the discrimination circuit 16 indicates that when the signal charge is required, after confirming that the horizontal shift register 3 is in the accepting state, the vertical shift register 3 is A shift operation is executed, the first charge is transferred to the horizontal shift register 3, the address of the horizontal line is held, and the vertical shift operation is executed when the signal charge is not needed according to the output of the discrimination circuit 16, and the first charge is transferred to the horizontal shift register 3. is swept away.

[Effect]

When reading out the stripe pattern area of the two-dimensional image sensor 21, the information necessary to detect the absolute position is contained in the lines of the stepped portion. Therefore, if only the line including the stepped portion is read out, the time required to read out one frame of the image sensor can be shortened compared to reading out all pixels. Whether or not a stepped portion is included can be detected by the discrimination circuit 16 from the coincidence and mismatch of the binarized image signals of the pixels at both ends of the stripe pattern. That is, if the two match, the line does not include a stepped portion and does not require reading, and if the two do not match, the line requires reading. Charges on lines that do not need to be read are not supplied to the horizontal shift register 3, but are discarded through the ground line.

The charges on the line that need to be read are supplied to the horizontal shift register 3, and taken out to the output terminal by a horizontal shift operation.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. This embodiment is an application of the present invention to the previously proposed absolute position detection device mentioned above.

With this absolute position detection device, an image, a part of which is shown in FIG. 2, can be obtained. In FIG. 2, × represents a stepped portion generated at the edge of the pattern P in the striped pattern area 23,
. represents the reading point of the numerical pattern area 22. Gl,
G2. G3...G10 indicate gray code values that are a collection of pixel data values (0 or 1) near the center of each track. In the example shown in FIG. 2, change point coordinate values and gray code values corresponding to 10 sets of step portions are obtained, and 10 pieces of absolute position information are obtained by the above-described calculation.

That is, to obtain absolute position information, only the output signal of the horizontal line where the coordinate change point is located is required.

FIG. 1 shows a configuration for reading out only horizontal lines containing necessary information. In FIG. 1, the signal charge from the photodiode 1 marked with diagonal lines is transferred to the vertical shift register 2U.
・2D...Transferred to 2E. Vertical shift register 2U
and 2D are for transferring the signal charges of the pixels 23D and 23U at both the left and right ends of the pattern P of the striped pattern area 23 in FIG. Compatible.

The signal charges at the head of the vertical shift registers other than the vertical shift registers 2D and 2U are transferred to the horizontal shift register 3 line by line, or are swept out through the ground line 4. In FIG. 1, a circuit for switching between transfer to the horizontal shift register 3 and sweeping out through the ground line 4 is omitted. The output charge of the horizontal shift register 3 is converted into a signal voltage by a charge-voltage conversion circuit 5, and is supplied to a comparison circuit 6. A threshold voltage is supplied to the comparator circuit 6 from a terminal 7, and a binarized output signal is obtained at an output terminal 8 of the comparator circuit 6.

The first charge of the vertical shift register 2D is supplied to the comparison circuit 1OD via the charge-voltage conversion circuit 9D, and the first charge of the vertical shift register 2U is supplied to the comparison circuit 10U via the charge-voltage conversion circuit 9U.

A threshold voltage from the terminal 7 is supplied to these comparison circuits 10D and IOU. Comparison circuit 10D
and 10U output signals (0 or 1) are supplied to exclusive OR gate 11.

-14=The output signal of the exclusive OR gate 11 is supplied to the AND gate 12, and the output signal of the AND gate 12 is
The signal is supplied to the R gate 14. A read inhibit signal is supplied from a terminal 13 to the AND gate 12, and the OR gate 1
4, a forced read signal is supplied from the terminal 15.

The output signal of the OR gate 14 is supplied to the determination circuit 16,
When the output signal of the OR gate 14 is 1, the signal charges of the line containing the head charges of the vertical shift registers 2D and 2U are transferred to the horizontal shift register 3, and when the output signal of the OR gate 14 is 0, the signal charges of the line containing the head charges of the vertical shift registers 2D and 2U are transferred to the horizontal shift register 3. The signal charges of the lines containing the leading charges of the shift registers 2D and 2U are swept out through the ground line 4 and discarded.

In other words, the presence or absence of a coordinate change point is determined by the stripe pattern area 2.
This can be determined from the binarized values of pixels 23D and 23U at both the left and right ends of 3. If the values of the pixels in both columns are different, it can be determined that there is a coordinate change point, and if the values of both pixels are the same, it can be determined that there is no coordinate change point. If the determination circuit 16 determines that there is no coordinate change point, the signal charge of that line is discarded. On the other hand, if the determination circuit 16 determines that there is a coordinate change point, it confirms that the horizontal shift register 3 has stopped operating (acceptable state), executes the vertical shift operation, and simultaneously transfers the leading charge to the horizontal shift register 3.
Transfer to. At the same time, the vertical address of the line determined to have a coordinate change point is transferred to a vertical address register (not shown).

When the read prohibition signal supplied from the terminal 13 to the AND gate 12 is set to 0, reading is forcibly prohibited regardless of the presence or absence of a coordinate change point.

This read prohibition operation is used to limit the number of lines to be read and to keep the read time of one frame within a predetermined time. Also, the terminal 1 is connected to the OR gate 14.
When the forced readout signal supplied from 5 is set to 1, all pixels are forcibly read out regardless of the presence or absence of a coordinate change point.

This forced read operation is used for quality inspection of the image sensor 21, etc.

When the image sensor 21 is of an interline type, the order in which the charges of each pixel are read out is as follows.

■Transfer the charge of the photosensor diode to the vertical shift register.

■Execute the shift operation of the vertical shift register.

At the same time, the first horizontal line charge is transferred to the horizontal shift register.

■Execute the shift operation of the horizontal shift register.

At the same time, the leading charge is read out.

In one embodiment of the invention, each of the above operations is performed in the order shown in FIG. The first vertical shift operation (2) is an operation performed until a coordinate change point is detected for the first time. When the coordinate change point reaches a certain line, a transfer operation (2) through the horizontal shift register 3 is performed. In parallel with this, a vertical shift operation (2) is performed to detect the line where the next coordinate change point is located.

Shift time required for operation ① is T2 (for example, 1/Is)
Let the shift time required for the operation ① be T3 (for example, 0.
17I5) and the number of horizontal pixels and vertical pixels is 100, the time T required to read out the charge of the pixel with the necessary information of the CCD image sensor 21 is Too~9 + (1+0.I X100) X10 =1
The time is 10 to 119 μs. Therefore, compared to reading out all pixels of the image sensor 21, the reading time for one frame is shorter.

Note that the present invention can also be applied to CCD image pickup devices other than the interline type.

〔Effect of the invention〕

Since this invention continuously reads out only the lines that include the pixels necessary to obtain absolute position information, the readout time for one frame is shortened compared to reading out all the pixels of the image sensor, resulting in output delay. It can save you a lot of time. Furthermore, if the readout time is set to be the same time as reading out all pixels, the clock frequency of the shift operation will be lower, which has the advantage of reducing power consumption.

[Brief explanation of the drawing]

FIG. 1 is a connection diagram of an embodiment of the present invention, FIG. 2 is an enlarged view showing a part of the image of the image sensor, FIG. 3 is a route diagram used to explain the operation of the embodiment of the invention, and FIG. The figure is a block diagram showing a schematic configuration of an absolute position detection device to which the present invention can be applied, FIG. 5 is a plan view showing an example of a code plate pattern, and FIG. 6 is an enlarged view of a striped pattern P imaged by an image sensor. The plan view shown in FIG. 7 is a route map for explaining the coordinate conversion operation. Explanation of main symbols in the drawings 2D, 2U, 2E: Vertical shift register, 3: Horizontal shift register, 4: Ground line, 11: Exclusive OR gate, 16: Judgment circuit, 21: Image sensor, 22: Numerical pattern area, 23 varnish drive-like pattern area. Nakimu 弗→ Koto stop- Ichimi Y\tH:l rJ='s, 1st child/procedural amendment, Kae. September 7, 1988 Patent Application No. 125385 2, Name of the invention Absolute position detection device 3, Relationship to the case of the person making the amendment Patent applicant address 6-7-35, Kitashinyo, Tokyo Parts Co., Ltd. Issue name (21
8) Sony Corporation Representative Director Norio Ohga 4, Agent 170 Address 1-48-10 Higashiikebukuro, Toshima-ku, Tokyo 1986
August 30, 2015, 6, Column 7 of the brief explanation of the drawing in the specification subject to amendment, page 19, line 11 of the specification of the contents of the amendment, ``This is a route map for.''
is corrected as below. ``Route map for ``, Figure 8 is a route map for explaining the readout operation of the image sensor.''

Claims (2)

[Claims] (1) A discrimination circuit is provided at the exit of the transfer register connected to the horizontal shift register of the two-dimensional image sensor to determine whether the signal charge is necessary or not.The output of the discrimination circuit determines when the signal charge is necessary. ,
After confirming that the horizontal shift register is in the accepting state, a vertical shift operation is executed to transfer the leading charge to the horizontal shift register, hold the address of the horizontal line, and use the output of the discrimination circuit to determine the signal. An absolute position detection device characterized in that the vertical shift operation is executed to sweep out the leading charge when the charge is not needed. (2) A control circuit that forcibly requires or eliminates the need for a signal charge from the outside is provided on the output side of the discrimination circuit, and a forced read function or read prohibition function is added. Absolute position detection device according to scope 1.