GB2143635A - Chart reader - Google Patents

Abstract

A chart reader comprises a reading station having sensing means (20,23,24) for sensing features of the chart (11) to be read, movement means (13,19) for moving the chart (11) past the reading station so as to enable it to be read by the sensing means (20,23,24), signal producing means (23) for producing a signal from the sensed information, converting means (25,26) for connecting the signal produced into digital form and processing means for processing the digital signal to provide an analysis of the information sensed from the chart (11). The reader may include a slit through which the chart (11) is illuminated by a light source (20), and through which it is viewed by a lens system (24) imaging the slit on a photosensor (23) e.g. a CCD array. <IMAGE>

Description

SPECIFICATION Chart reader This invention relates to a chart reader and is particularly applicable to the reading of charts to process information therefrom automatically.

One such chart which requires to be read is that which is produced by a tachograph. As from the Ist of January 1982, the use of approved recording equipment for recording details of vehicles used for the carriage of passengers or goods became law, the main exception to this being private vehicles such as cars.

The data which has to be recorded is imprinted on a tachograph chart. This tachograph chart is usually a circular chart with provision for the recording of a twenty-four hour period. For this purpose,the chart is rotated by means of a quartz crystal clock. On this chart are recorded vehicle speed, distance travelled, driving time, and other periods of work. Legally, the vehicle operator whose vehicles are fitted with tachographs is required to produce a log for each driver containing certain information from the tachograph charts.

At the present time there have been a number of analysing aids which can be used by the operator or other person reading the charts. These range from use of a magnifying glass to the provision of motor driven turntables with push button counters operated by the operator so as to store information being read by him from the chart.

One problem with the present systems is that considerable skill is required on the part of the operator in order to make sense of the often elaborate traces which appear on the tachograph chart and therefore the results produced are highly susceptible to human error. Also the time required to extract even the minimum required data from the chart takes a minimum of 3.1/2 minutes and, on some occasions, can take as long as 12 minutes.

Clearly the present arrangements are uneconomical large waste in man power and cannot be heavily relied upon as accurate and free from error.

The present invention seeks to provide a chart reader which will read a chart and will provide automatically, data in a form which enables analysis of the chart read to be achieved in a relatively short time.

According to the invention, a chart reader comprises a reading station having sensing means for sensing features of a chart to be read, means for moving the chart past the reading station so as to be road by the sensing means, means for transmitting the sensed information to signal producing means means for converting this signal into digital form and means for processing the digital signal to provide analysis of the read chart.

Preferably the sensing station operates optically and is provided with an illuminated slit for alluminating a section of the chart to be read, reflections from the chart being received in the slit and being transmitted from there to a signal generator.

Preferably the means for illuminating the slot comprise optical fibres. The illumination may be carried out at a slight angle so that the returning light falls directly on a receiving lens. The optical information from the receiving lens may be passed to a chart charge coupled device (CCD) for the production of an electrical signal corresponding to the optical information. Suitably the chart is circular and is rotated over the slit about its axis such that the slit lies on a radius of the disc.

The invention will now be described in greater detail, by way of example, with reference to the drawings in which: Figure 1 is a diagrammatic sectional view of a reading part of a tachograph chart reader in accordance with the invention; Figure 2 is a diagrammatic plan view of the face of the chart reader receiving the disc; Figure 3 is a detail of the light source; Figure 4 is a block diagram of the processing stages applied to signal received from the apparatus shown in Figure 1 and 2, and Figure 5 is a diagrammatic perspective view of the complete apparatus for processing a tachograph chart.

Referring first to Figures 1,2 and 3 there is shown the reading part of the device. This comprises a generally trapezoidal casing 10 in which the operating parts are housed, the one short face 11 of the casing 10 having an aperture 37 through which protrude a drive element 13 for a tachograph chart 14 and adjacent to this is an horizontal slit 12 (Fig. 3) by which the chart 14 (shown in broken lines) is to be illuminated and through which it is to be read. A pair of rollers 29 are provided which can be swung by means of a handle 30 from the position shown in figure 1 up against the chart so as to press it firmly against the face 10 at the position of the slit 12. This will enable charts which are not entirely flat to be properly read. In this way, the chart 14 is pressed firmly against the illuminating and sensing slit 12.The driving element 13 comprises an off centre coupling arrangement 36 by which the chart is coupled to the drive, this off centre arrangement 36 being connected by a shaft 37 to the drive shaft 38 of a stepping motor 19 controlled by a microprocessor (not shown in this figure). Situated directly beneath the slit 12 is an optical illumination device 20 which is constructed of optical fibres so that illumination may be provided by a lamp housing 31 to one side of the device 20, the light travelling from this lamp housing to illuminate the slit through a cylindrical lens (e.g. an optical rod) used to diffuse the light over the slit 12 (see Fig. 3). The arrangement is such that the illumination takes place at a small angle allowing the reflected light to by pass the device and transmit it directly to a receiving lens 24.In this way, light diffusion exterior to the slit is cut down and a good recovery of the light reflected from the chart 14 is achieved.

The reflected light coming from the chart 14 is focused on a charge coupled device (CCD) 23 situated therebeneath by means of the lens 24 positioned over the CCD 23. This lens 24 is of high quality, eg. a CCTV lens, to provide accurate focusing of the light onto the cells, for example 256 cells, which make up the sensing field of the CCD 23. Various adjustments are provided for focusing the lens 24 and adjusting the image produced in relation to the CCD 23. The CCD 23 is provided in addition to the 256 cells, with two charge transfer gates, and 2-phase analogue transport shift registers, an output charge detector/amplifier and a compensation amplifier. Light energy which falls on the various 256 sensing cells generate charge packets which are proportional to the light intensity falling upon them.These charge packets are transferred in parallel to two analogue transport registers which are clocked by a 2-phase clock.

From these transport registers, the charge packets are passed to an output amplifier also situated in the main chip where the charge packets are converted into proportional voltage levels. Thus a series of pulses which are amplitudes modulated with the optical information appear at the output.

The whole of this circuitry and chips is located on two circuit-boards, 25 and 26, are located adjacent the CCD 23 and the other on the side of the casing adjacent thereto. The necessary operations can be carried out with the aid of standard development boards. For example, one such development board is the I-scan produced by Fairchilds and including a CCD 11 with associated clocking logic.

With this system, suitable illumination is a tungsten-halogen lamp which provides light with wave lengths in the range of 600 nm as required by the CCD.

Additionally to the main sensing operation, since the tachograph chart is a 24 hour chart, it is necessary to sense the appropriate times and this can be achieved by the use of identification mark (not shown) on the stepping motor shaft 37. It is proposed that the 24 hour chart should be scanned in 1000 radial slices by the means of the slit 12 and this will result in a scan of information over a period which corresponds, on the chart, to 1.4 minutes. Thus the stepping motor has to steps. The above operate in 1!1000 revolution described reading device provides a series of pulses, amplitude modulated with the optical information from the chart as its output. These pulses are fed frpm the initial processing board 25 to an interface board shown in the block diagram in Figure 3.

The signal from the initial processing board e.g.

I-scan board, passes to sample hold circuit 100 and produces from the pulses an analogue wave form in the nature of a smooth curve. The signal from the sample and hold circuit 100 which is an analogue signal is passed to an automatic gain control and equalisation circuit 101 which determines the change in amplitude in the wave form and superimposes these onto a constant DC level. Basically this circuit compensates for variations in the illumination of the CCD due to mechanical alignment defects in the lens, warped charts etc. It also amplifies the signal by a factor of two. This amplified signal passes to a voltage comparator 103 in which the voltage of the signal is compared with the reference voltage 104 which forms a threshold.

Parts of the signal which have a voltage lying above the reference voltage are indicated as a logic "1" while the remaining parts of the signal represent a logic "0". The voltage comparator 103 provides an output representative of the input wave form, but in the form of a binary signal. Thus acts as an analogue binary converter.

From this converter 103 the signal is fed to a serial to parallel converter 105. It comprises a shift register into which the incoming serial form signal is clocked so as to convert the serially arriving signal into parallel transmissions of eight bits. To this end, after eight clock pulses are received from a clocking and timing logic 106, the output of the serial to parallel converter 105 is latched into a buffer 109 and the microprocessor which is connected to the other end of the interface board is interrupted.

The buffer 109 holds the eight bits of data until the microprocessor is ready to read it. For every scan of the chart, 32 bytes of information will be available to the microprocessor.

The buffer 109 passes signals into the PIA micro interface 110 which is a standard peripheral interface adaptor provided for interface between the interface board and the microprocessor and enables control of the various output facilities such as control of the stepping motor 19 and the iighting for illumination of the chart 14. The PIA is protected by buffer logic and level changing circuits 111 which prevent damage to the PIA and also provide for changing the levels of the signal received so that they are of the required level for operating the peripheral equipment.

The information provided by the PIA to the microprocessor (not shown in this figure) along a line 112 enables the microprocessor to process the binary information provided into the required information, in this case information as to details of the operation of a vehicle. For this purpose a relatively standard microprocessor can be used, the necessary programmes for providing the appropriate information being pre-programmed into "read only" memories of the microprocessor.

In the microprocessor, the digital signals are processed to convert the information which has been provided by the linear on the chart into intelligible information. For example, most tachograph charts indicate the mileage travelled by a line which reverses direction after a particular mileage has been travelled. Thus the microprocessor can count the number of times the liner passes a certain radial point or count its arrival at one or both ends of its travel and produce mileage figures based on this count.

Similarly calculations produced by the microprocessor from the digital information provided can give information about the vehicle speed, stopping times average speeds etc.

Figure 4 shows schematically suitable form of the apparatus device for practical use. The apparatus is in the form of three units, the reader 50, the microprocessor 51 and the keyboard unit 52. Built into the microprocessor unit 51 is a printer 53 on which can be printed the details which have been produced from the microprocessor. The keyboard 52, which is connected to the microprocessor 51 by a lead 54, is suitably provided with contact keys 55 to prevent the ingress of dirt into the interior. It is also provided with a display 56 which can show both what is being typed in and the microprocessor output. The display may take the form of LED's or LCD's. The keyboard is used to control the operation of the chart reader and also to input additional information which may be required on a printout, such as the registration number of the vehicle or the name of the driver.

In operation of the device the operator takes the tachograph disc 14 and places it on the drive 13 after lifting the rollers 29 on the reading device.

The rollers 29 are then lowered and the operation of reading the disc may be started by pressing a suitable key on the keyboard 52. Prior to this operation, the details of the driver and or vehicle may be inserted on the keyboard and, depend ing on the programming of the microprocessor, one can also key in a request for additional information one requires such as the maximum speed of the vehicle. The operation of the device is then totally automatic and, in accordance with the instructions which have been keyed in, it will produce the information on the display on the front of the casing and/or will provide a printout by means of the printer. Furthermore, the device may be provided with a further interface (not shown) which allows it to be connected up to a micro computer or even a mini or main frame computer for the calculation of data such as the drivers wages etc.

It will be appreciated that while the above described embodiment is related to the reading of a tachograph chart, similar apparatus could readily be used for reading other circular-charts as required.

It will be understood that various modifications may be made to the above described embodiment without departing from the scope of the invention.

For example, the invention may be used for reading linear charts so that a drive for driving a linear chart may be provided instead of the rotating drive necessary for circular charts. Where a universal apparatus is required, two sets of drives may be provided. It is to be noted that no change in the electronics is necessary to read a linear card since the dimensions of the slit involved may be chosen to ensure that a similar signal is produced whichever kind of chart is being used.

Other modifications that may be provided consist of the provision of a light source on the opposite side of the chart to the sensing device where the chart to be read is either transparent or translucent in nature.

Claims (12)

Claims

1. A chart reader comprising a reading station having sensing means for sensing features of a chart to be read, movement means for moving the chart past the reading station so as to enable it to be read by the sensing means, signal producing means for producing a signal from the sensed information, converting means for converting the signal produced into digital form and processing means for processing the digital signal to provide an analysis of the information sensed from the chart.

2. A reader as claimed in claim 1, wherein the reading station comprises a slit through which features of the chart are to be read, illuminating means for illuminating the chart through the slit and means for transmitting light received by the slot by reflection from the chart to the signal producing means.

3. A reader as claimed in claim 2, wherein the illuminating means comprises optical fibres.

4. A reader as claimed in claim 2 or 3, wherein the illumination of the slot is carried out at a small angle to the vertical to the plane of the slit whereby the reflected light can by pass the said illuminating means.

5. A reader as claimed in claim 2, 3 or 4, wherein the light transmitting means comprises a receiving lens and the signal producing means comprises a charge coupled device on to which light from the receiving lens falls.

6. A reader as claimed in any one of claims 2 to 4, wherein the movement means comprises a stepping motor and means for coupling the stepping motor to the chart for driving the chart.

7. A reader as claimed in claim 6, wherein the chart reader is constructed to read linear charts and the stepping motor is coupled to a mechanism for moving the chart linearly.

8. A reader as claimed in claim 6, wherein the chart reader is constructed to read circular charts and the stepping motor has a drive shaft carrying an off centre coupling by means of which it is coupled to the chart for rotation thereof.

9. A reader as claimed in any one of claims 2 to 8, wherein stabilising means are provided for pressing the chart against a base member through which the slit passes adjacent to the slit so as to ensure correct positioning of the chart relative to the slit.

10. A reader as claimed in claim 9, wherein the stabilising means comprise two rollers one on either side of the slit.

11. A reader as claimed in claim 10, wherein the rollers are movable towards and away from the base member to enable insertion and removal of the chart.

12. A chart reader substantially as described herein with reference to the drawings.