CA2350877C

CA2350877C - Timing ruler or timing disk

Info

Publication number: CA2350877C
Application number: CA002350877A
Authority: CA
Inventors: Paul-Wilhelm Braun
Original assignee: PWB Ruhlatec Industrieprodukte GmbH
Current assignee: PWB Ruhlatec Industrieprodukte GmbH
Priority date: 2000-06-20
Filing date: 2001-06-19
Publication date: 2004-02-24
Anticipated expiration: 2021-06-19
Also published as: US6822219B1; TWI250267B; CA2350877A1; KR20010114164A; DE10029380A1; EP1167928A3; KR100393477B1; JP2002039797A; EP1167928A2; HK1044984A1

Abstract

A timing device, such a s a timing disk or a timing ruler is provided with a carrier having at least one code track of a group and overlapping therewith and at least one code marking, which is scanned by a sensor unit to produce signals. The code track or tracks have a different optical density in comparison to the first group, and the code markings within a code track overlap. Also disclosed is a positioning device which includes a timing disk or a timing ruler with a carrier having a first group of code markings in at least one code track.
Here the code markings are scanned by at least one sensor unit for producing a signal and the signal processing device for converting the sensor signal into a control signal is connected after the sensor unit.

Description

Timing Ruler or 't'iming Disk The present invention relates to a timing disk or a timing ruler that consists of a carrier having a first group of code markings disposed in at least one code track, this group of code markings being scanned by at least one sensor unit in order to generate a digital signal.
A timing disk or a timing ruler of the type described in the introduction hereto is described, for example, in US-PS 5,5013,08 (PWB basic patent). According to one embodiment of the device described therein, three concentric code tracks with different markings are arranged on a timing disk. Three sensor units are required for scanning the three tracks, with the sensor units arranged in a manner similar to the known device as shown in Figures 1 a, Ib, or 2a, 2b. This means that in order to scan several tracks disposed on a timing disk, several sensor units are arranged side-by-side in the radial direction, whiclu greatly increases the overall size of the scanning unit. In addition, several sensor units require more complex electrical circuits, which increases circuitry costs and makes the device more prone to malfunction as a result of mechanical shock. The increased parts count and the more complex software introduce additional sources for error. This is a significant disadvantage for the further improvement of printers, scanners, and copiers. In practice, tlxe carrier also ages, which tends to make the carrier material opaque, or else it becomes contaminated, which is a particular problem with open systems such as inkjet printers. Both these situations can introduce errors if the sensor interprets the degraded areas as code markings.

It is the object of the present invention to develop timing disks or timing ruler,:3 such that they are of robust construction and are l~::s:~ ~>rorue to error as a result of their design, and so that they can simultaneously capture several separate optical signals by using one sensor unit, as a result of simple, material-specific, and circuit:-related measures. In addition, it:. is another obje:cti.ve to provide continuous signal amp:l.ificati.can as used, for example, with potentiometer systems, and to produce a simple position-measuring device, for example, in the form of a steering angle sensor, in a manner that is both technically simple and economical.
According to the present inverztic~rx, there i.s provided a timing device, compr:isa.ng a carrier having a first group of code markings disposed :in ate least one code track and, overlapping this, one car a plurality of code markings that are scanned by at least one sensor unit in order to generate signals, there being a d:i.fferent optical density in a following code track or track: as compared to the first group, the code markings overlapping within a code track, characterized in that mufti-channel evaluation of optical signals takes place with the signals taken from the sensor unit, the code markings of the first group being spaced apart at a constant interval, whereas subsequent groups with modified code markings are ciist.ributed over the code tracks of the first. group, tile code, rnarkings for controlling different functions being fcarmed on the timing device.
It has been observed that two or more groups of code markings can be detected independently of each other by using a single sensor unit if the code markings of said a groups are of different optical densities. In this context, optical density refer:) tc a gzwadation of tine grey levels between approximately 100% (dar°k grey) to approximately 0%
(fully transparent, fully reflect:ive). Tt is preferred that absolute positioning eye achieved riot by us ~rng bars, but rather by exploiting the increasing or decreasing grey levels. In this case, the optical density changes, so that the sensor generates Signals of greater intensity for lighter grey tones and of weaker intensity in the case of darker grey tones, or vice-versa.
The different groups of code markings in a track can be scanned simultaneously using a two-channel or a mufti-channel sensor a.znit . The groups caf code markings can also overlap one another. Tt is suffic::~ent:: if the sensor unit senses a notic:ea~ale change ire ~:he c:~pt:~.cal density, so that a correspondingl.~~r modified voltage is detected by t:he sensor unit. Differences of, for example, 100~v have been found to be adequate, although other vc~:~.tage differences can be used, depending on the sensitivity of the measurement devices that are emplayed.
Suitable sensors consist c.~f aru LED or another light source, and photo transistcars or ether light-sensitive scanning devices. For controlling start and/or end positions, or for purposes of calibration, the sensor units can detect signals with either a constant separation or an arbitrary separation aver the ~~a~t:~ re :segment ranges o - t:he timing disk or of the timing ru~lez~.
The present invention will be described in greater detail below on the basis of several examples shown in the :3 drawings appended hereto. These drawings show the following:
Figure 1a: a timing disk wit.rA different groups of code markings;
Figure 1b; :segment of a timing disk with different groups of code markings;
Figure 2: a scanning sir.~nal from a sensor unit during scanning of a first group of code markings;
Figure 3: a scanning signal from a sensor unit during scanning of the second group of ~~ode markings;
Figure 4: a combination of the scanning signals shown in Figure 2 and Figure .'~;
Figure 5.1, 5.2, 5.3 and 5.4: symbolic representations of various ways code ma:rki:rzgs can be superimposed; and Figure 6: special mufti.-charnel evaluation.
Figure la shows the segment of a timing disk having dark grey and light grey code bars. The steps in the different grey levels have to be selected so that ageing andJor contamination c~f the timing disk does not produce erroneous scanning signals. 'I"he scanning :zignals in the regions a-b, b-c from the segrraent of the timing disk shown in Figure 1b are recorded in the valtagejfzequency diagrams shown in Figure 2 and Figure 3. ~1s can be seen, a large amplitude that corresponds to a large signal voltage (due to the black tint of the bars) is produced in the region a-b, whereas only the ampl:~tude that corresponds to a reduced :3a signal voltage was detected in t::he area b-~c (because o~ the less intense coloration of the c~C~de bans). Comparable arguments can be app7.ied tc~ reflective: tinning disks.
3b following description is intended to explain the principle of positioning measurement in more detail, on the basis of a specific example. Positioning measurement is intended to permit contact-less photo electric scanning of an incremental scale, when it is essential to maintain a high level of measurement accuracy. Given appropriate circuitry, it is possible [to use] phase-multiplying circuits or potentiometer circuits, for example, if the pitch of the cade markings is changed. If the pitch consists of consecutive light and dark fields of identical size, then a photo transistor scanning across this pitch will generate a sinus voltage of a wavelength corresponding to the sum of the two lengths of a tight and a dark field. It is also possible to subdivide the existing pitch even further, thereby producing a potentiometer circuit.
This signal intensity of the standard timing disk remains constant. With an analog sensor, for example, a Hewlett-Packard (Agilent Technologies) Q9846+OOa'7, additional pulses for calibration are generated without the need for any additional code tracks. An analog signal derived therefrom can be used for advancing paper, for stitching lines, and/or for absolute positioning in printers, scanners, or copiers.
According to the present invention, in addition to the existing signals from the first group of code markings, a second variable is introduced, for example, a change of the grey level of the code markings. The grey level determines light transparency ar optical density, and thus the amplitude of the signal. It is also possible to identify each angular position as an absolute position, and to identify intermediate steps in the same way as with an optical potentiometer.
9;

Arbitrary intermediate steps Can be encoded by suitable gradation of the grey levels. In this way, certain segments of a timing disk or a timing ruler that are associated with additional fune.t::ians can also be defined.
Examples of a multi-drannel evaluation of the timing disk according to the present invention are shown below; a multi-channel timing ruler is structured analogously.
Figure 5.1, 5.2, 5.:3, arid 5.4 are symbolic representations of the way in whi~:.h code markings cart be superimposed. This involves three different code tracks that are transferred t:o a timing disk by subtraction or addition. When this a.s done, tape particular code structures are superimposed.
What is shown in detail is as fo;:llows:
Figure 5.1 shows a bar structure with black: bars spaced at equal intervals a:rour~d the c:i;~cumference of the timing disk;
Figure 5.2 shows a code track that is divided into four segments by four individual bars that differ from each other but which are i:~~ each ircst~anoe of an identical grey tone within a segment;
Figure 5.3 shows a code track with a coloration that varies continuously around the ci.r_cumference. The coloration can be generated by means of a filter. In Figure 5.4, the individual code tracks shown lri Figures 5.1, 5.2, and 5.3 have been superimpcased to produce a total st:rucaure.
This combines all the signals fr.~c;.~~n th~:~ three individual.
tracks and. thus ~a provides an overall and unified information unit for the sensor unit. Four segments with four different grey bars can be differentiated by subtraction of tlae grey tone from the black bars.
Given appropriate adjustment of the sensor unit, it is possible to generate a third track that can be evaluated. This is done by addition of a colour that changes continuously around the circumference of the timing disk and which is superimposed on the basic structure..
Special mufti-channel evaluation is required for the mufti-track arrangement of code markings described above. This is described below, using Figure C.
The number of sensor surfaces that the sensor unit 1.0 contains corresponds to the number of code tracks that are to be evaluated. The sensor surfaces are connected with a corresponding number of channels, in the present example, two channels for the analog signals A and B.
The signals A and B that are phase shifted through 90° are routed to a comparator circuit 11 by way of the two channels. This comparator circuit forms digital signals 12, 13 from the analog signals, and these are similarly phase-shifleri. From these, the evaluator unit can determine the incremental pulses of the signals 12, 13 and/or the frequency of the bar structure--and, by means of a known integrated circuit, e.g., a Type LS 7084, the direction of rotation.
One of the channels, e.g., the channel for signal A leads to an amplitude measurement circuit (measurement unit 15). This identifies the lower boundary value of the amplitude (low amplitude) and the upper boundary area (high amplitude) and delivers these values, separated, to a definition unit 16 and 17.

The definition unit 16 identifies the grey tone of the bars from the low amplitude. 'The darker the code track, the lower will be its voltage in the voltage-amplitude display. This makes it possible to determine the absolute position when the timing disk rotates. When there are four different segment areas, as in the preceding example, the defnition precision lies within these four segments.
The change in colour is evaluated in the evaluation unit 17. The absolute position of the timing disk is determined from the upper limiting value of the high amplitude, according to the particular voltage-amplitude curve. When this is done, definition precision lies within a bar region. Thus, this definition is quasi-analog.
Arbitrary intermediate steps can be encoded by suitable gradation of the grey levels. In this way, certain segments of a timing disk or a timing ruler that are associated with additional functions can also be defined.
Advantageously, although this is not absolutely necessary, the signals of the first group of code marks can have a constant period length that is independent of the grey level. Because of their different degrees of light transparency, control devices of this kind can also be used for timing disks or timing rulers having slit markers for photo interrupters or for other devices that generate an analog signal.

Claims

1. A timing device, comprising a carrier having a first group of code markings disposed in at least one code track and, overlapping this, one or a plurality of code markings that are scanned by at least one sensor unit in order to generate signals, there being a different optical density in a following code track or tracks as compared to the first group, the code markings overlapping within a code track, characterized in that multi-channel evaluation of optical signals takes place with the signals taken from the sensor unit, the code markings of the first group being spaced apart at a constant interval, whereas subsequent groups with modified code markings are distributed over the code tracks of the first group the code markings for controlling different functions being formed on the timing device.

2. The timing device as defined in claim 1, characterized in that code markings of the subsequent groups are used for controlling a starting position.

3. The timing device of claim 1 or 2, characterized in that the code markings of the subsequent groups are used for controlling an ending position.

4. The timing device of any one of claims 1 to 3, characterized in that the code markings of the subsequent groups are used for purposes of calibration.

5. The timing device of any one of claims 1 to 4, characterized in that the code markings of the subsequent groups are used for purposes of absolute positioning.

6. The timing device as defined in any one of claims 1 to 5, characterized in that the carrier of the timing device is of a reflective material; and in that the code markings differ in their degree of reflectivity.

7. The timing device as defined in any one of claims 1 to 6, characterized in that there is a sensor surface for each signal group in the sensor unit, with which the signals are picked up and passed by way of a suitable line to a comparator and an amplitude measurement device; and in that a direction of movement of the timing device is determined from digital signals and their phase shift.

8. The timing device of any one of claims 1 to 6, characterized in that a direction of rotation of the timing device is determined from digital signals and their phase shift.

9. The timing device as defined in any one of claims 1 to 8, characterized in that low-amplitude signals and high-amplitude signals that are used for absolute positioning are derived from an amplitude-measurement device.

10. The timing device as defined in any one of claims 1 to 8, characterized in that a high-amplitude signal is used for determining a position within a bar structure.

11. The timing device as defined in any one of claims 1 to 8, characterized in that a low-amplitude signal is used for determining position within a segment structure.

12. The timing device of any one of claims 1 to 11, characterized in that the timing device is a timing disk.

13. The timing device of any one of claims 1 to 11, characterized in that the timing device is a timing ruler.