Apparatus for timing sporting events

The apparatus is a motion picture camera including a charge coupled photosensitive device provided with a multiplicity of unit sensors. The sensors are arranged in a matrix of M rows and N columns. The apparatus is equipped with a pulse generator for controlling the transfer of charges from sensor to sensor along the columns, the frequency of the pulses being adjusted to effect substantial correspondence between the speed of charge transfer and the speed of the image moving over the device. A shift register is arranged at the end of the columns so as to receive in parallel information from said columns and to transmit it in series to an output circuit for reconstitution of the image. The apparatus is used for timing sporting events. This invention concerns an apparatus for timing sporting events including a motion picture camera installed at a fixed position and having a lens the axis of which is directed onto a line to be crossed by competitors so as to record the events occurring on said line.

BACKGROUND OF THE INVENTION 
Several devices corresponding to the above general definition have already 
been proposed. They permit the obtaining of an image of the course at the 
moment when the competitors cross a determined line, in particular the 
finish line. The image takes account moreover of the photographic identity 
of each of the runners and of the rank which they occupy relative to one 
another thanks to a time scale which is recorded on the same image. 
One of the oldest of such arrangements generally called photofinish, is 
known from the Swiss Pat. No. 399.028 (=GB No. 1.045.434). It includes an 
apparatus comprising a photographic camera the film of which advances with 
uniform motion, means arranged to photograph only a narrow space or one 
line at a time, and means enabling the projection of time indications to 
be recorded on the film. 
This apparatus is illustrated on FIG. 1 of this description. The moving 
body is displaced at a speed Vm in front of the lens 1 of the camera. 
Behind the lens is to be found a screen 4 provided with a slot 2. Behind 
the slot runs a photographic film 3. The image of the moving body moves at 
the speed Vi in front of the screen while the film runs at the speed V. An 
adjustment is made so that the speed V is as close as possible to the 
speed Vi. The effect of the slot is that the film receives only a part of 
the entire image seen by the lens, this part being one line of the image. 
The running of the film behind the slot has as effect to expose the film 
successively in time with the same line of the image. The photofinish thus 
records a bidimensional image which represents according to an axis 
(perpendicular to FIG. 1), the profile of the intensity of a line of the 
image and in accordance with the other axis (in the plane of FIG. 1), the 
time evolution of this profile. The visual analysis of the image enables 
reconstituting the order in time of the appearance of different moving 
bodies in the field of the line. Finally, by the addition onto the film of 
reference points giving information on the exact time of recording, the 
appearance of the different moving bodies may be measured in time. This 
arrangement is employed for instance to measure the order and the time of 
passage of competitors over a finish line. 
In the system which has just been described, the exposure time Te of film 3 
is the time of transit of this film behind slot 2, i.e. Te=.delta./V, if 
.delta. is the width of the slot. In practice, there is desired an 
exposure time of the film which is as great as possible, so as to enable 
taking views of subjects poorly illuminated or passing at high speed. This 
exposure time is at the same time limited by the blurring of the image 
materialized for instance by trails appearing at the edge of the moving 
body and which are provoked by a difference of speed between the speed V 
of the film and the speed Vi of the image of the moving body. This 
blurring determines the time resolution of measurement. 
The phenomenon of blurring may be explained by means of FIG. 2 which 
reproduces at an enlarged scale a part of FIG. 1 including screen 4 and 
slot 2. In this figure there has been represented the same point P of the 
image of the moving body which is displaced from A to B at speed Vi. 
During the same time lapse, the film is driven at a speed V slightly less 
than Vi in a manner such that when the image has advanced from A to B the 
film advances only from A to C. There results therefrom a trail from the 
point P which will leave an impression on the film over a length .DELTA.x 
which is a representation of the spatial blurring. To this spatial 
blurring there naturally corresponds a temporal blurring Tf which may be 
put into relationship with the exposure time Te of the film and which 
takes into account the spread between the speeds V and Vi. This 
relationship may be given as follows: 
##EQU1## 
In case speeds V and Vi are substantially equal, the factor .mu. approaches 
zero and it follows that Tf&lt;&lt;Te, which signifies that the exposure time is 
much greater than the temporal blurring. 
Here there may be cited a practical example drawn from an athletic course. 
The film of the camera is adjusted to a speed V of 35 mm/sec. The image of 
the course moves past in reality at the speed Vi of 28 mm/sec, giving a 
factor .mu. of 0.2. If one specifies a temporal blurring Tf of 1 ms, there 
will result therefrom an exposure time Te of 5 ms according to the 
relationship (1) given hereinabove. 
There results from what has just been said that the photofinish as known 
today is advantageous in view of the comfortable time of exposure which it 
provides. At the same time, it exhibits certain disadvantages. It requires 
in effect a chemical development of the film which delays access to the 
results of the course. It requires good accessibility to the camera which 
limits its utilization to certain positions. There may also be mentioned 
its relatively great space requirement and mediocre reliability in view of 
the mechanical parts making up its construction. 
To overcome these difficulties, the assignee of the present invention has 
disclosed in Swiss Pat. No. 590.518 another system for determining the 
time separating the passages of moving bodies across a reference line 
substantially perpendicular to their trajectory. This system consists of 
employing a television camera which is directed onto the reference line, 
recording the signals provided by said camera and simultaneously signals 
furnished by time keeping means, and reproducing these signals by the aid 
of a monitor. In order to realize this, there is employed a camera by 
means of which a linear unidirectional scan is effected coinciding with 
the reference line, and a pickup effecting a linear bidirectional scan in 
a manner such that the successive scans of the reference line by the 
camera are spread out over the screen of the pick-up in a direction 
perpendicular to that in which is effected the unidirectional scans, that 
is to say in the direction of the trajectory of the moving bodies. This 
patent mentions that such camera may be of a conventional type, but 
wherein however the two scans have been permuted in a manner such that the 
more rapid scan is effected according to the vertical direction, the 
slower scan having been suppressed. As a variant it is mentioned that 
preferably a camera will be employed using diodes of the solid state type. 
This system is shown on FIGS. 3 and 4 of the present description. Here the 
moving body is displaced at the speed Vm in front of the lens 1 of the 
camera. Behind the lens there is placed a unidimensional photosensitive 
device 5 using solid state sensors. The image of the moving body runs at 
speed Vi in front of the device 5. FIG. 4 shows how the device is built 
such including a row of photosensitive unit sensors 6 disposed side by 
side. The incident light coming from the reference line to be sensed 
produces charges on each of these sensors which charges represent the 
intensity profile of the line of the image at a given instant. These 
charges are periodically transferred in the sense of arrows 9 into a shift 
register 7 bearing as many elements 8 as the sensor 6. A clock signal 12 
operating at high frequency transfers the contents of the line towards 
amplifier 10 in the form of a video signal 11. These video signals are 
then memorized, and subsequently visualized in a manner to represent in 
the form of an image the temporal evolution of the line under observation 
(finish line for instance). 
Several uni-dimensional devices are presently available on the market. They 
are all equipped with a substantial number of sensors (&gt;1000) to assure 
high resolution. For further details on this subject, reference may be had 
to the technical notes of the manufacturers, for instance to the note 
concerning the device TH 7803 of Thomson-CSF. One may even obtain complete 
cameras from the Fairchild company under the reference CCD 1100C to 1500C. 
In the system which has just been described, it has been seen that the 
incident light produces charges on the row of sensors 6 which charges are 
periodically transferred towards the output 10 via the shift register 7. 
The selection of the duration of this period which will be referred to as 
To, determines at the same time that of the exposure time Te and of the 
temporal blurring Tf which, since here the sensor is stationary, is equal 
to: 
EQU Tf=Te=To (2) 
Thus, to repeat the same example suggested with reference to the 
photofinish, and if here one determines the temporal blurring Tf to be 1 
ms, the exposure time Te is equal to 1 ms. It is understood that the 
unidimensional system is less favourable than the photofinish since it 
presents a relationship Tf/Te equal to 1, while the relationship was equal 
to .mu. in the system employing the photofinish. 
There results from what has just been said that the unidimensional system 
as discussed above exhibits low luminous sensitivity which limits its 
range of application to scenes which have a substantial illumination. 
SUMMARY OF THE INVENTION 
To overcome the difficulties presented by both of the two systems described 
hereinabove, the apparatus provided in accordance with the present 
invention, is characterized by the fact that the camera comprises a 
bidimensional photo-sensitive charge coupled device including a 
multiplicity of sensors arranged in rows and columns, the rows being in a 
direction parallel to the image of the line of passage of the course, and 
the columns being in the direction of the running of the course and a 
pulse generator is provided for controlling the transfer of charges from 
sensor to sensor along the columns, the frequency of the pulses being 
adjusted to effect substantial correspondence between the speed of charge 
transfer and the speed of the image moving over the device, a shift 
register being arranged at the end of the columns so as to receive in 
parallel information from said columns, and to transmit it in response to 
a clock signal in series to an output circuit so as to reconstitute row by 
row the image received by the device.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 5 shows schematically a motion picture camera arranged in accordance 
with the invention for timing sporting events. This camera is installed at 
a fixed position, the axis of its lens 1 being directed onto a line 20 
over which competitors must pass (departure line, intermediate line or 
finish line). Behind lens 1 there is placed a charge coupled 
photo-sensitive device 21 which will be subsequently described. A moving 
object 22 is displaced over a track of the course at speed Vm. The image 
of this moving body is displaced over the photosensitive device at the 
speed Vi. If the distances a and b represent respectively the distance 
from the lens to the moving body and the distance from the lens to the 
device, the speed Vi will be: 
##EQU2## 
The photosensitive charge coupled device is shown in a facing view on FIG. 
6. It includes a multiplicity of unit sensors arranged in rows and in 
columns, i.e. M rows and N columns. In the arrangement provided here, such 
rows are directed parallel to the image of the passage line of the course 
and the columns are arranged in the sense of the running of said course. 
Thus, as will be best seen on the perspective view of FIG. 7, the course 
image runs over the device 21 in the sense of the M elements comprising 
the columns. 
The photosensitive bidimensional device 21 is known in itself. A detailed 
description of an example thereof is given in a technical note of "Itek 
Optical Systems" 10 Maguire Road, Lexington, Mass. 02173, such note being 
entitled "VL-96 A, High-Performance Linear Solid State Imaging Device". It 
is defined by the note under the designation "Linear Solid-State Imaging 
Device Using Time--Delay-And-Integrate TDI Operation". Herein this element 
will be referred to as a bidimensional photosensitve charge coupled 
device. It contains 2048 columns and 96 rows. Each unit sensor extends 
over a surface of approximately 13.times.13 .mu.m.sup.2. The device is 
conceived in a manner such that the charges accumulated on each of the 
unit sensors may be transferred to neighboring sensors in the sense of the 
columns. Thus, returning to FIG. 6, the charge accumulated on sensor 25 of 
column 26 may be transferred onto sensor 27 of the same column, then onto 
sensor 28 and so on according to the direction of arrows 29. It is the 
same and in a synchronous manner for the N columns of the device. The last 
charge 30 of column 26 is transferred at the same rhythm as the transfers 
of the other columns to a shift register 31. Thus the shift register 31 
arranged at the end of the columns receives information in parallel coming 
from said columns according to the direction of arrows 32. As soon as the 
information has been stored in the shift register 31, such may be 
transferred in series responsive to a clock signal 33 to an output circuit 
34 generally formed by a transistor JFET. The output signal of this 
transistor is in analog form 35 and represents the profiles of intensity 
of the line of passage at successive instants. The transfer of charges 
from one sensor to the other in the sense of the columns is obtained by a 
pulse generator 36 the frequency of which may be varied. 
A basic characteristic of this invention resides in the adaptation of the 
speed of charge transfer represented by V and controlled by the pulse 
generator 36 to the speed of displacement Vi of the image over the 
photosensitive device. If speeds V and Vi are adapted to one another or if 
preferred, are equal, it will be understood that each elementary charge 
always follows the same point of the object in motion. This is 
particularly apparent on FIG. 7. There will be noted as example the eye 40 
of runner 41 being displaced along the course track at speed Vm. The image 
of this eye 42 is displaced at the speed Vi after having passed through 
lens 1. If the speed V of charge transfer from one sensor to another in 
the direction of the columns N is adapted to the speed Vi and if each 
column contains for instance 96 sensors, the charge accumulated by the 
luminous intensity produced by such eye onto the first sensor will be 
transferred onto the second sensor which will receive at this instant 
likewise the image of the same eye and thus following until the 96th 
sensor. There may be seen from this teaching that the exposure time is 
multiplied by a factor equal to the number of sensors M to be found in one 
column. This increase of the exposure time enables improving the 
performance of the image capture and measurement in one or several of the 
following characteristics: scenes with poor illumination, greater 
resolution of the image, capture of images having very rapid movements. 
If the transfer of elementary charges as well as the reading from a row of 
the image are effected at regular intervals of period To, it will be 
understood that with a bidimensional photosensitvie device comprising M 
sensors in the sense of one column, the exposure time Te will be: 
EQU Te=M.multidot.To 
If one takes into account the spread of speed between V and Vi as defined 
hereinabove (photofinish) by 
##EQU3## 
there may be specified the amount of temporal blur Tf which is: 
EQU Tf=To+Te.multidot..mu. 
In replacing To by its value, there is found: 
##EQU4## 
It is seen that the temporal blur comprises the addition of the factors 
which characterized on the one hand the photofinish (equation 1) and on 
the other hand the unidirectional device (equation 2) which have been 
described in the introduction to the present description. In the case of 
this invention, the relationship Tf/Te is valued at 1/M=.mu., this 
enabling one to say that the bidimensional photosensitive device gives 
results comparable to those of the photofinish, but without having the 
disadvantages thereof. Effectively, in choosing a number of sensors 
relatively high, the temporal blur is reduced as in the photofinish to the 
portion .mu..multidot.Te. Conversely, if the speed match is perfect 
(.mu.=0) the temporal blur is limited to Te/M. 
Thus, repeating the same example suggested with reference to the systems 
known to the prior art and setting a temporal blur Tf of 1 ms, the 
exposure time Te for factor .mu. of 0.2 and the number of sensors M at 96 
will amount to 4.76 ms, this having been respectively 5 ms and 1 ms for 
the photofinish and the unidimensional device. 
There has been seen with reference to FIG. 6 that the pulse generator 36 
controls the charge transfer from one sensor to the next. These short 
duration pulses Ti are shown on the diagram of FIG. 8. They are repeated 
at the rhythm To which defines the transfer rate. Between the short 
duration pulses Ti the luminous charges are accumulated on each of the 
unit sensors. 
In order to read the row of the photosensitive device which has just been 
transferred into the shift register 31, there is required a clock signal, 
the frequency f of which is N times greater than the frequency Fo 
corresponding to the period To, N being equal to the number of columns of 
the device. Thus, the frequency of the clock signal will be adjusted to be 
equal to 
EQU f=N.multidot.fo 
The pulse generator 36 providing the frequency fo may be controlled by a 
clock signal, for example by means of a divide by N circuit. 
An example drawn from an athletic course will facilitate appreciation of 
the order of magnitude of the signals. It has already been seen that the 
image of such a course runs over the photosensitive device at a speed of 
35 mm/s. If the unit sensor has a square surface the side of which is 
equal to 13.multidot.10.sup.-3 mm, the time To during which a point of the 
image rests in contact with the same sensor is 13.multidot.10.sup.-3 
/35=0.371.multidot.10.sup.-3 S, this giving a transfer frequency fo=2695 
Hz. If the device is provided with 2048 columns, the clock frequency will 
be f=2048.multidot.2695.congruent.5.5 MHz. For an automobile race, the 
speed of the image may attain 200 mm/s. At this value a similar 
calculation will give fo=15.4 kHz and f=31.5 MHz. This is probably to be 
considered the highest speed which one will encounter within the range of 
application of the apparatus according to the invention. Conversely, it 
will be noted that the slowest speed likely to be encountered will be that 
during boat races and which is on the order of 4 mm/s and for which fo=307 
Hz and f=0.628 MHz. 
From the examples which have just been given two remarks may be made: 
Initially, the apparatus in accordance with the invention in order to be 
adapted to every competition which may arise, must be able to adapt its 
reading speed V to the speed Vi of the image of the course. This 
adaptation may be automatically accomplished by measuring the speed Vi and 
an appropriate slaving of V to Vi. It could likewise be obtained manually 
by means of a regulating knob as is presently practised with the 
photofinish. Whether one chooses one or the other of these methods, the 
regulation will be applied finally to the pulse generator 36 in order to 
vary its frequency fo for instance between 300 and 16,000 Hz in order to 
provide a margin of security in view of the figures indicated hereinabove. 
This regulation could also be applied to the frequency f of the clock 
signal since f=N.multidot.fo and N is a fixed number depending from the 
number of columns in the photosensitive device. It should be specified 
here that the transfer frequency fo between 300 and 16,000 Hz is 
understood to be for a specific lens and for a well defined dimension of 
the sensors. If the focal distances a and b defined hereinabove are 
altered and if the sensor provides other dimensions than that of 
13.times.13 mentioned hereinabove, the transfer frequency may extend 
between other limits. 
In other respects, each row of the image is well defined in time because of 
the transfer frequency fo. To each row there thus corresponds a defined 
time of day which enables the utilization of this frequency as a time base 
for marking the image in time. Thanks to this arrangement, it is possible 
to blend the image of the output with a time scale. It will be understood 
thence that the shortest time that one will be able to appreciate will be 
that given by the transfer frequency fo since to each transfer there 
corresponds a row of the image and a time which may be attributed to this 
row. Thus for the speeds given as an example hereinabove, the time 
separating one row from the neighbouring row is respectively of 3.25 ms, 
0.37 ms and 0.065 ms for boating courses, athletic courses and automobile 
courses. 
The analog signal of the row represented at 35 on FIG. 6 is employed for 
reconstituting the image of the moving body on the screen according to the 
known techniques associated with television. The row frequency will 
naturally be synchronized with the frequency of charge transfer fo. The 
reconstructed image may appear on a CRT screen, be magnetically recorded 
by a video recorder or appear on a paper support. 
The reconstructed image may appear in black and white or in colour. In the 
latter case, three photosensitive charge coupled devices will be employed, 
each receiving for instance by interposed filters a different basic 
colour.