United States Patent
`Hylin et al.
`
`[w]
`
`[54] DIGITAL INFORMATION SYSTEM
`
`[75]
`
`Inventors: Mats Hylin, Danderyd; Mats
`Dahlgren, Helsingborg; Joakim
`Jonasson, Lidingo, all of Sweden
`
`[73] Assignee: Dahlgren, Hylin & Jonason Media
`AB, Danderyd, Sweden
`
`[21] Appl. No.: 08/676,517
`Jul. 2, 1996
`[22] Filed:
`
`Related U.S. Application Data
`[60] Provisional application No. 60/017,403, May 14, 1996.
`Foreign Application Priority Data
`[30]
`
`Apr. 26, 1996
`
`[SE]
`
`Sweden
`
`9601603
`
`G06F 17/60
`[51]
`Int. C I.
`345/2; 705/5
`[52] U.S. CI
`[58] Field of Search
`345/1, 2, 3, 173,
`345/7; 395/214, 329, 200.3; 379/142; 349/5-7;
`705/14, 5
`
`[56]
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`9/1995 Martin
`5,448,263
`5,508,713
`4/1996 Okouchi
`5,565,911 10/1996 Ishikawa et al
`
`345/173
`345/2
`348/15
`
`US006005534A
`[ii] Patent Number:
`[45] Date of Patent:
`
`6,005,534
`Dec. 21, 1999
`
`5,568,279 10/1996 Hinman et al
`5/1997 Tanikoshi et al
`5,634,018
`6/1997 Harrison, III et al
`5,642,484
`5,675,637 10/1997 Szlam et al
`5,745,688
`4/1998 Oka
`Primary Examiner—Bipin H. Shalwala
`Assistant Examiner—David L Lewis
`Attorney, Agent, or Firm—Pillsbury Madison & Sutro LLP
`[57]
`ABSTRACT
`
`345/2
`395/329
`395/214
`379/142
`345/2
`
`The invention relates to a digital information system (10) for
`displaying information on at least one display means with
`the aid of at least one projector (22). The exposures are
`presented at places accessible to and frequented by a general
`public. The information system (10) includes external infor¬
`mation mediators (24) and informationis controlled dynami¬
`cally through the medium of a communication interface (26)
`and through the medium of an exposure handler in a central
`computer (28). The inventive system also includes a com¬
`munication interface (14) against an elective number of
`station computers (34) having connected projector comput¬
`ers (38) which control projectors (22) for displaying pictures
`or exposures. The station computers (34) and peripheral
`equipment are situated at mutually distanced places. Accord¬
`ing to one particular field of use, the places mentioned are
`subway stations (16, 18, 20) and projectors (22) project
`exposures or pictures onto display means positioned at
`selected places in the stations (16, 18, 20).
`
`24 Claims, 1Drawing Sheet
`
`30. DATABASE
`
`30, DATABASE
`
`24, INFORMATION
`' MEDIATORS
`
`26. MODEM
`
`D
`
`14, RADIO LINK
`
`36
`
`18
`
`36
`
`20
`
`STATION 2
`
`STATION 3
`
`WORKING
`STATIONS
`
`28, CENTRAL
`COMPUTER
`CONTROL CENTRAL
`
`STATION 1 34.STATION
`S IAl ION
`COMPUTER
`
`38, PROJECTOR
`COMPUTERS
`
`22, PROJECTOR
`
` IPR2016-01869 Ex. 1003
`Broadsign International, LLC Petitioner
` 1
`
`

`
`U.S. Patent
`
`Dec. 21, 1999
`
`6,005,534
`
`32
`
`30, DATABASE
`
`30, DATABASE
`
`WORKING
`STATIONS
`
`26, MODEM
`
`24, INFORMATION
`) MEDIATORS
`
`14, RADIO LINK
`
`O
`
`20
`
`STATION 2
`
`STATION 3
`
`-ÿ-*
`28, CENTRALS-
`COMPUTER
`CONTROL CENTRAL
`
`SUBWAY
`STATION 1 34, STATION
`COMPUTER
`
`38, PROJECTOR
`COMPUTERS
`
`22, PROJECTOR
`
`
` 2
`
`

`
`6,005.
`,534
`
`1
`DIGITAL INFORMATION SYSTEM
`
`RELATED APPLICATION
`
`This application claims priority to the provisional U.S.
`patent application No. 60/017,403 entitled "Communication
`System", filed May. 14, 1996.
`
`TECHNICAL FIELD
`
`The present invention relates to a method and to apparatus jo
`for controlling and coordinating projectors in a digital
`information system for displaying information on at least
`one display device through the medium of at
`least one
`projector for each said device, said information being dis¬
`played in places that are accessible to and frequented by a 15
`general public. In one particular aspect, the invention is
`applied to control projectors for displaying information
`directed towards people in such places as main railway
`stations, subway stations, airport waiting lounges, etc.
`
`DESCRIPTION OF THE BACKGROUND ART
`
`2°
`
`Systems that are used to show information in the form of
`advertisements, timetable messages or arrival and departure
`times in present-day public service infrastructures with
`regard to buses, trains, subway traffic, etc., is of a static 25
`nature. Such information is given on notice boards, posters,
`charts, tables, verbally through loudspeakers, and on digital
`displays, etc. A characteristic feature of such information
`media is that the information media is not coordinated, but
`is in the form of individual items which are controlled and 30
`updated separately, often manually.
`Modem digital displays used, e.g., in conjunction with
`subway railway traffic gives some of the aforesaid informa¬
`tion but is not controlled to display advertisements, warning
`messages, etc. Furthermore, the information is often supple- 35
`mentedwith verbal messages transmitted from traffic control
`centres. The information channel cannot be subscribed to
`directly for the display of external information suppliers,
`such as advertising bureaux, the authorities, newspapers,
`etc., but is processed administratively and fed manually into 40
`the information display systems.
`Although the administration of information is often pro¬
`cessed manually with the aid of modern computer
`technology,
`the available display time will nevertheless
`contain "dead time", among other
`things due to back-
`logging caused by the manual infeed process.
`Thus, present-day systems do not enable information to
`be updated dynamically for display in real time. Neither do
`present-day systems enable external mediators to update 50
`information for display in a central control system, nor yet
`the administrator who makes the display of information
`available, but that it is the administrator who determines
`when, where and how the information shall be displayed.
`The present-day static information display systems are 55
`therefore beset with a number of problems.
`Also known to the art are systems for displaying or
`showing picture series in local public places, such as assem¬
`bly halls, lecture halls, and conference rooms in industry.
`The systems comprise diapositive projectors which are 60
`controlled to display pictures, images and sound in an
`attractive manner, often with rapid picture changes and
`overlaps, so as to avoid the risk of boring viewers, as with
`conventional display with diapositive projectors. The com¬
`puter control of such systems may well be both complicated 65
`and advanced. Unfortunately, these systems are nevertheless
`static insofar as they are used in one and the same locality
`
`2
`and controlled and managed on the display site. The display
`must be planned carefully beforehand, this planning often
`being carried out by experts within the technical field in
`question, so as to obtain a finished display product. For
`instance, when a company wishes to change its display and
`introduce a new picture series combined with sound, the
`process again becomes static by virtue of the need to employ
`experts to program and arrange the new display.
`The same problem as that mentioned above is also met
`when showing pictures through diapositive projectors in one
`and the same locality, because the display subscriber has
`very little chance of influencing the display, especially in
`real time. The picture display is directed towards a limited
`public and towards scheduled display of one and the same
`information material to the public concerned. The picture
`display is not directed to a large number of people, as in the
`case of a railway station platform, a subway platform or in
`airports. In places of this nature, it should be possible to
`spread the information and to display different information
`in different places within said stations and it should be
`possible to update and change the information quickly.
`When the information displayed on said stations is not
`effectively coordinated, the displays on which informationis
`presented will often become static, for instance show the
`time of the next display or show a pause picture, i.e. dead
`time. This becomes nerve-wracking to travellers, who often
`wait for long periods inwaiting halls or stand on platforms.
`Neither is the failure to utilize expensive informationdisplay
`equipment to the highest possible degree compatible with
`good economy.
`
`SUMMARY OF THE INVENTION
`An object of the present invention is to provide a flexible
`system in which external information mediators are able to
`dynamically control in real time the transmission of display
`instructions to a larger public in different places situated at
`any chosen distance apart through projectors which project
`information onto displays intended herefor.
`Another object of the invention is to enable pictures,
`images, messages and announcements to be configured in
`accordance with modern digital technology, therewith pro¬
`viding rapid communication.
`A further object of the invention is to enable a picture,
`image or other information to be changed inpractice as often
`as is desired, in real time, therewith providing direct and
`immediate communication, and to enable similar or specific
`information to be displayed in places that are mutually far
`apart and to enable message information to be alternated
`with advertising spots, for instance.
`According to one aspect, the present invention relates to
`a method of coordinating and controlling projectors in a
`digital information system for displaying information on at
`least one display device through the medium of at least one
`projector for each such display device, said information
`being displayed in places that are generally available to and
`frequented by a general public.
`Information display subscribers are connected to a com¬
`puterized control centre via computer and telecommunica¬
`tion interfaces for all-day-round transmission of
`information, wherein the control centre has a communica¬
`tion interface against computerized devices situated in con¬
`nection with said places for projector coordination and
`control.
`The control centre is able to create and update a display
`list in real time with control instruction fields via booking
`information for display dynamically in time from mediators
`
`
` 3
`
`

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`15,534
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`3
`having drive routine means which are connected to the
`subscription and which are transparent for the transmission
`of information to the drive routine means of the control
`centre for transmission of information in the system.
`The display list, which includes control
`instructions,
`coordinates and controls the projectors concerned with
`regard to what shall be displayed, when it shall be displayed,
`where it shall be displayed and for how long it shall be
`displayed, and causes each projector, independently of other
`projectors, to receive the same or different information for
`display through respective projectors and through the com¬
`puterized devices, in accordance with the display list.
`The administrator of the digital information system is able
`to update the display list with desired information at any
`time whatsoever, wherein the dynamic booking can be
`changed or delayed.
`The projector may also interrupt display of information
`when the allocated display devices, or the projector, is/are
`visually obstructed in said public place. The projector lens
`can then be covered with a protective device when a dirty
`atmosphere is detected or anticipated and which is imma-
`nently likely to dirty the lens.
`In one embodiment, the projectors provided with a pro¬
`jector computer which controls and delivers exposures to the
`projectors controlled by a server included in the computer¬
`ized device, wherein the projector computer has a buffer
`memory which is filled with subsequent exposures as the
`exposure to be displayed at that moment via the projector is
`emptied from the buffer memory.
`Alternatively, a server included in said computerized
`device is providedwith a projector computer which controls
`and feeds exposures to the projectors, wherein the projector
`computer is connected to a buffer memory which is filled
`with subsequent exposures as the exposure current at that
`particular moment is displayed through the projector and
`emptied from the buffer memory.
`A server situated in a specific place and included in a
`computerized device further includes databases, and infor¬
`mation in the databases concerning exposures in the expo¬
`sure list is copied in databases of servers in a selected
`number of computerized devices situated in other places.
`In one embodiment,
`the exposure list may include
`reserved instruction fields for updating with control instruc¬
`tions via the mediator interface, wherein the control instruc¬
`tions can be placed in a waiting line, or queue, when the
`exposure list lacks instructionupdating fields at that moment
`in time.
`In another embodiment of the invention, a switch detects
`when a station computer is not functioning, wherein those
`projectors controlled by the station computer are controlled
`by another station computer situated at some other place.
`A further embodiment can also be used as "feedback" and
`monitoring in statistical analysis by a system administrator
`with respect to whether or not vehicles keep to the timetable,
`when the display of information is interrupted either because
`the display device is obstructed or because the projector is
`obstructed. In one embodiment, the computerized devices
`comprise an electronic display with control computer,
`wherein projectors are comprised of electronic displays.
`The present invention also relates to an arrangement of
`apparatus for carrying out the aforesaid method, said appa¬
`ratus including the aforesaid devices and an exposure han¬
`dler which creates the exposure list.
`BRIEF DESCRIPTION OF THE DRAWINGS
`The following description makes reference to the text in
`the accompanying drawings to provide a better understand-
`
`4
`invention, said
`ing of
`the embodiments of the present
`drawings illustrating schematically a system for coordinat¬
`ing and controlling projectors in a digital information system
`for displaying information in accordance with the invention.
`
`5
`
`25
`
`DETAILED DESCRIPTION OF PREFERRED
`EMBODIMENTS OF THE INVENTION
`The present invention relates to a method for the dynamic
`coordination and control of projectors in a digital informa-
`10 tion system for displaying information on at
`least one
`display device via at least one projector for each display
`device, wherein the information is displayed in places that
`are accessible to and frequented by a general public. The
`invention also relates to an arrangement of apparatus for
`15 carrying out the method.
`Although implementation of embodiments are limited in
`the following to subway railway stations, it will be under¬
`stood that the invention is not restricted to these embodi¬
`ments. As before mentioned, the inventive system can be
`20 used in places where large sections of the public are known
`to visit, such as railway stations, airports, outdoor locations,
`etc., in addition to subway stations.
`Preferred embodiments of the invention will now be
`described in detail with reference to the accompanying
`drawings, which illustrate schematically a system 10 for
`coordinating and controlling projectors in a digital informa¬
`tion system for displaying information on display devices,
`such as free-standing picture screens, wall-mounted screens,
`3Q walls, and overhead screens or other means suitable for
`reproducing or exposing picture information in the form of
`text, stills, movable pictures, images, etc. (displays not
`shown in the drawing).
`In the main, the system is comprised of a control centre
`35 12 having a communication interface 14 which connects an
`unlimited number of computerized devices 16, 18,20 which
`are placed at desired distances from one another for the
`control of projectors 22 whose projector images or pictures
`are displayed in the aforesaid public places.
`The illustrated system also includes an advertising agency
`which is connected to the control centre 12 through the
`medium of a computer 24 and a modem 26. Although only
`one modem is shown connected to the central computer 28
`of the control centre, it will be understood that modem poles,
`45 telephone switching centres and other similar devices may
`be used to this end in accordance with present-day tech¬
`niques.
`The central computer 28 in the control centre 12 also
`includes databases 30, in the illustrated case two databases.
`50 The databases 30 may be externally connected to the central
`computer. The control centre also includes working stations
`32, which are preferably connected to the central computer
`28 via a Local Area Network (LAN) in accordance with
`known techniques. The working stations 32 are used by the
`55 personnel serving the control centre 12, in monitoring,
`checking, maintaining and updating functions in the central
`computer with its databases. The control centre administra¬
`tor is able to insert projector control instructions via the
`working stations, for instance when information is directed
`60 specifically to travellers and passengers travelling by ship,
`train, subway, aircraft or some other vehicular traffic who
`require specific information. The information may concern
`the arrival times and departure times of passenger-carrying
`vehicles. The administrator controls internally how, what,
`65 when or where the information shall be displayed by the
`projectors 22. An important feature in this context, however,
`is that external information mediators 24 are able to give
`
`40
`
`
` 4
`
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`6,0(
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`15,534
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`5
`control instructions to the projectors 22 with regard to the
`information that the external mediators 24 desire the system
`10 to display via the projectors 22, each on its own initiative
`and communication-wise transparent via modems 26. This
`can be achieved in accordance with one embodiment of the
`invention without involving the working stations 32 in the
`procedure of transmitting the control
`instructions to the
`central computer 28.
`The term information mediator (24) used in the following
`shall be interpreted in its widest meaning, i.e. as not only
`referring to advertising agencies but to all companies and
`private persons who wish to utilize the system 10 for
`commercial reasons or for the display of information that
`concerns a general public. At present a mediator which
`wishes to display information in public places is normally
`forced to wait about two weeks, perhaps longer, before his
`order can be implemented and the information publicly
`displayed. With the inventive digital information system 10,
`the information can be displayed principly in real time, i.e.
`at the time of making the order, possibly with a short delay
`due to processing, fully-booked exposure lists and other
`quickly passing causes. Furthermore, an external informa¬
`tion mediator 24 is able to put through information to the
`system 12 twenty-four hours a day, whereupon the infor¬
`mation can be included instantaneously in an exposure list,
`as illustrated in more detail below.
`Those external information mediators which connect to
`the control centre 12 via modems are, in one embodiment of
`the invention, connected to the control centre via specially
`designed interfaces (drive routine means) for data and
`telecommunication. In this way, only external mediators 24
`having the correct interface are able to connect transparently
`to the control centre 12 for delivering control instructions to
`the projectors 22, which avoids unauthorized access to the
`display of such information and misuse of the system. Inthis
`regard, the special interface, which may be included in the
`computers of external mediators, also includes commer¬
`cially available code keys or other codes sent between the
`control centre 12 and the computer 24 of the external
`mediator to verify the right to enter control instructions into
`the central computer 28, without the administrator needing
`to supply through the working stations 32 further informa¬
`tion or authority permitting access of the external informa¬
`tion mediators 24 to the central computer for transmitting
`system transparent control instructions to the projectors 22.
`Inaccordance with the invention, the control centre 12 has
`the computerized
`a communication interface 14 against
`devices 16, 18,20 situated on shifting positions or places for
`projector coordination and control.
`The drawing shows specifically a radio link which forms
`an interface between the control centre 12 and the comput¬
`erized devices 16, 18, 20, this interface being a preferred
`interface, although not necessarily the sole possible inter¬
`face. Other interfaces for transmitting information between
`the control centre 12 and the computerized devices 16, 18,
`20 may consist of a cable-carried ISDN solution (Integrated
`Services Digital Network) or other fixed lines that have the
`same capacity.
`In one embodiment of the invention relating to subway
`station 1, the computerized device 16 is comprised of a
`station computer (server) which either includes or is con¬
`nected externally to a hard disk 36, wherein the station
`computer 34 is connected to a plurality of projector com¬
`puters 38, three such projector computers in the illustrated
`case, which transmit control information to connected pro¬
`jectors 22, only one of which is shown. The projector
`
`6
`computers 38 have the form of PC units with picture screens
`in the illustrated case. The information sent to projectors 22
`can be monitored on the picture screens of the PC units 38
`and edited by personnel stationed at different
`locations
`5 within the subway station 16, or from a central location. In
`the illustrated embodiment, station 2, referenced 18, and
`station 3, referenced 20, comprise other subway stations that
`are equipped with devices similar to the devices of the
`subway station 16, although without showing the projector
`computers 38 and the projector 22. It is assumed, however,
`that these stations also include projector computers 38 and
`at least one projector 22.
`In an alternative embodiment of the device or devices 38,
`i.e. the projector computers 38, included in the station
`computer 34, the projector or projectors 22 is/are controlled
`directly from the station computer 34.
`In yet another embodiment of the devices included in the
`computerized devices 16, 18,20, the projector 22 is replaced
`with an electronic display (not shown), such as a large
`2Q picture screen in LCD technology,
`light-emitting diode
`technology (LED technology) or the like. The station com¬
`puter 34 is then included in the large picture screen or is
`connected externally thereto. Preferably, the projector com¬
`puters 38 in the station computer 34 and the database 36 are
`25 also included. Information is transmitted from the control
`centre 12 generally in the same manner as that before
`described. However, each separate large picture screen may
`be addressed directly through a radio network 14, wherein
`the screens are controlled from the control centre 12 which
`3Q includes redundancy. Thus, in the illustrated case, the com¬
`puterized devices 16, 18,20 form an electronic display with
`control computer 34, said projector 22 effecting the display.
`According to one embodiment, the computerized devices
`16, 18,20 may include redundancy by virtue of all databases
`35 36 or hard disks on the stations 16,18,20 including the same
`projector control information or instructions for monitoring
`the system in a subway station 16, 18, 20. Thus, all infor¬
`mation is copied between the station computers 34 and their
`databases 36 via the communications interface 14 from the
`40 central computer 28. This means that a computerized device
`for displaying information in a subway station via projectors
`22 will not be disabled should one or two of the stations
`shown in the drawing suffer a computer or hard disk power
`down in a station computer 34. Inthe event of a power down
`45 in a station computer 34, the communications interface 14
`can be coupled to a switch which automatically bypasses the
`station computer and connect projectors 22 connected to the
`power down computer 34 to one of the station computers 34
`is still in function (the switch is not shown in the
`that
`50 drawing).
`The digital information system 10 has been described in
`the aforegoing with regard to respective hardware and
`Implementation of
`invention in
`the present
`interfaces.
`achieving the objects and purposes thereof will now be
`55 described more specifically.
`The illustrated central computer 28 is divided into three
`powerful servers 1,2, 3, of which server 1receives material
`from external information mediators 24, via modems 26.
`Server 2 sends information material to the station computers
`60 34. The same material can be sent to all station computers
`34, even though the information is to be displayed solely on
`a given display or on given displays. What shall be exposed
`and where it shall be exposed will be explained in more
`detail below.
`Server 3 functions to process information and control
`instructions received from the information mediator 24, as
`described in more detail blow.
`
`65
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`7
`The server 3 of the central computer 28 functions partly
`as an exposure handler. The exposure handler 3 carries out
`the important object of the invention with regard to the
`possibility of an external mediator 24 to organize the infor¬
`mation delivered to the station 16, 18, 20 via an exposure 5
`list,this organizing of informationbeing effected inreal time
`via the modem 26 and the server 1that receives projector
`control information from the external mediator.
`In one invention of the invention, a queue, or line, is
`created from the information material received by the server 20
`1, in accordance with some known line or queuing method,
`such as FIFO (First In First Out), LIFO (Last In First Out)
`or Round Robin, etc., wherein the server 3 or exposure
`handler 3 has set-up or created an exposure list which covers
`a twenty-four hour period for information exposure or 25
`display via projectors 22. The exposure handler 3 collects
`and processes, i.e. allocates, information relating to projec¬
`tor control instructions, wherein mediator information is
`sorted into the exposure list in accordance with the wishes
`of the mediator 24 or its instructions, when available space 20
`is found in the exposure list or in alternative places in the
`exposure list given by the mediator. If the exposure list is
`completely filled with instructions, the mediator instructions
`to the control centre remain in the queue list in the servo 1
`in readiness for later inclusion in the exposure list, in 25
`accordance with a preferred embodiment.
`Inone embodiment of the invention, the exposure handler
`3 creates or allocates a data message (data field) including a
`header, a control character field, an address field, optionally
`least one CRC field (Cyclic Redundancy Code), and 30
`at
`optionally status flags which identify and are connected to
`the information from an information mediator 24 and filed in
`the exposure list in the time interval that the information
`shall be exposed or displayed through a projector 22. This
`constitutes an alternative to the insertion of the entire 35
`information bit from an external mediator 24 in a specific
`time interval in the exposure list, and enables the provision
`of an exposure list that contains much less information and
`which is thus easier to handle, and to accelerate transmission
`of the list between computers and databases included in the 40
`system.
`A data message in the exposure list can be understood
`here as being a control instruction in an instruction field for
`activating projectors 22 to project information.
`A data message of this kind connected to each individual
`information exposure enables known F1ASF1 or switching
`methods to find information included in the exposure time
`intervals in the exposure list both effectively and quickly. A
`First Class® server can be used conveniently for commu- 50
`nications transmission between external information media¬
`tors 24 and the control centre 12. Each external information
`mediator is then able to send an e-mail with included
`information material in any chosen format, which provides
`the advantage of not needing to write in any new software 55
`for the communication transmission function. As before
`mentioned, the system also incorporates a safety aspect,
`whereby each external information mediator that has an
`office or who subscribes to the system must possess a coded
`drive means or a coded drive routine in order to connect to 60
`the control centre 12.
`In order for external information mediators 24 to be able
`to deliver complete pictures/films, the mediator will prefer¬
`ably have its own versions of the software that the exposure
`handler 3 uses for enabling pictures/films to be introduced 65
`transparently into the exposure list without processing via
`the working stations 32 in the control centre 12.
`
`4J
`
`8
`Inone embodiment of the invention, there is thus included
`an alternative to the dynamic updating of the exposure list as
`mentioned in the aforegoing, i.e. the external information
`mediators 24 which do not have access to software in the
`exposure handler are providedwith the possibility of having
`their picture material or exposure material processed by
`personnel serving the working stations 32, wherein said
`personnel enter, via the working stations 32, the information
`that the external mediator 24 wishes to have exposed, or
`displayed, via projector control instructions in the exposure
`handler and via the exposure list created by the handler.
`Personnel at the working stations 32 are thus able to inter¬
`rupt any queue lists in the server 1to update the exposure
`list, via the exposure handler, with information generated
`centrally from the control centre 12 or with information that
`is insufficiently processed when received by the server 1
`from the external information mediator 24.
`In accordance with the aforegoing, external information
`mediators 24 that have access to the exposure program are
`able to deliver complete picture series/films which can be
`processed automatically and inserted into the exposure list,
`or optionally personnel administering the working stations
`32 are able to pick external mediator information from the
`queues, or lines, and process this information so that it can
`be inserted into the exposure list via the exposure handler 3.
`In order to be able to distinguish information that must be
`processed via the working stations, external mediators 24
`can mark or label such transmitted material with an appro¬
`priate code, so that the central computer 28 is able to identify
`this material and send it to working stations 32 for process¬
`ing. Alternatively, e-mail is processed and registered as
`information which must be processed.
`According to the invention, sensors may be placed in the
`close vicinity of projectors 22, such as to detect any obstacle
`that may prevent projectors 22 from displaying information
`on screens (not shown). These sensors are connected to
`projector computers 38, so as to enable said signals to be
`transmitted to the station computer 34. Alternatively, the
`sensors may be connected directly to station computers 34.
`The sensors are of a typical kind which detect the presence
`of obstacles, for instance optical sensors which detect when
`a light beam is broken, microphones, electromagnetic trans¬
`mitters or ultrasonic transmitters having one or more
`receivers, etc.
`When a sensor (not shown) registers the presence of an
`obstacle between a projector 22 and a cloth screen or some
`other display surface, the projector is stopped from project¬
`ing pictures during the time that the obstacle is present.
`The sensor may also function to place a cover in front of
`the projector lens, so that dust, dirt or the like cannot come
`into contact with the lens.
`the display that exposes the
`In the present case,
`information, e.g. a cloth screen, has a size of 4200x3000
`mm, which corresponds to the surface area of a present-day
`large screen. The screen cloth may have a reflex foil affixed
`thereto, or may be coated with some other form of reflective
`material to enhance luminescence. The screen cloths are
`illuminated with an OFl-projector 22 for instance, which is
`preferably mounted on the ceiling of a subway station with
`the aid of a special mounting means, wherein the optic is
`especially ground and/or providedwith a filter for correcting
`optical effects, such as reflections from the surroundings and
`other disturbing light. The projectors 22 project the infor¬
`mation material onto the screen cloth, wherein a cover is
`moved in front of the optic lens to protect the same against
`dust and dirt, for instance when a train enters alongside the
`platform.
`
`