US3750539A - Projection stencil assembly - Google Patents

Projection stencil assembly Download PDF

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US3750539A
US3750539A US00100988A US3750539DA US3750539A US 3750539 A US3750539 A US 3750539A US 00100988 A US00100988 A US 00100988A US 3750539D A US3750539D A US 3750539DA US 3750539 A US3750539 A US 3750539A
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character
disc
characters
gate
recording
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L Mason
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Xerox Corp
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Xerox Corp
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    • G—PHYSICS
    • G06—COMPUTING; CALCULATING OR COUNTING
    • G06K—GRAPHICAL DATA READING; PRESENTATION OF DATA; RECORD CARRIERS; HANDLING RECORD CARRIERS
    • G06K15/00—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers
    • G06K15/02—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers
    • G06K15/12—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers by photographic printing, e.g. by laser printers
    • G06K15/1238—Arrangements for producing a permanent visual presentation of the output data, e.g. computer output printers using printers by photographic printing, e.g. by laser printers simultaneously exposing more than one point

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  • ABSTRACT A recording system wherein a character disc or the like having transparent light modulating patterns thereon is rotated through an exposure zone so that selected patterns may be projected by the energization of a flash lamp.
  • the projected pattern is collimated and directed to a recording zone through which move lens-mirror units at a constant speed that intercept the projected pattern and focus it onto a photoreceptive recording medium.
  • the patterns are arranged on the character disc in spiralled configurations such that as the disc is rotated the first and last patterns of a spiral move through a fixed exposure zone at difierent positions relative thereto.
  • the present invention permits ,a constantly driven optical system with the assurance thatfthe inter-character spacing will be uniform throughout while making recording rates of at least 300 characters per second possible with typewriterquality.
  • FIG. 1 is a side view of an apparatus in which the present invention may be utilized
  • FIG. 2 is a front view of the apparatus of FIG. -1 with some parts broken away;
  • FIG. 3 is a top. cross-sectional view of FIG. 2 taken along section lines'33; I
  • FIGS. 4 and 5 illustrate sequential relationships between the character disc and the optical field stop disc for projecting properly spaced characters and projecting only one character at a time
  • FIG. 6 is a schematic representation of the logic circuitry which controls the apparatus employing the present invention.
  • FIG. 7 is a plan view of a modified character disc and stationary aperture mask embodying the present inventive concepts.
  • FIGS. 1, 2 and 3 which'depict in detail the significant portions of a character recorder in accordance with the principles of the present invention.
  • FIG. 1 shows in somewhat more detail than FIGS. 2 and 3 exemplary xerographic process stations which are conventional in nature and actually form no part of the present invention. However, they are illustrated to provide a point of reference for the present invention in a practical environment. Not all of the details of the xerographic process have been illustrated but sufficient details of those stations illustrated and other desirable stations not illustrated may be obtained from US. Pat. No. 3,187,651, which issued to Eichorn et al. on June 8, 1965, assigned to the same assignee as the present application.
  • a conventional xerographic drum 2 is shown to rotate in the'direction indicated by the arrow to pass successive portions under the influence of a pre-exposure corotron 4 and to an exposure station which is represented by the slit mask 6 where the previously charged xerographic drum is selectively discharged in accordance with the intensity of the image at the exposure station.
  • the latent electrostatic image thereby'produced may then be conventionally developed with electroscopic marking particles using a suitable developing apparatus such as a cascade developer represented by the housing 8.
  • the developed latent image is then moved to a transfer stationwhere a transfer corotron 10 transfers the electroscopic marking particles onto a, copy sheet which is held on a copy sheet conveyor l2 by means of a suitable gripper mechanism 14 shown in more detail in the aforementioned patent.
  • the copy sheet can originate from an appropriate copy sheet tray 16 under the influence of a feed-out roller 18 and paper guides 20.
  • a conventional radiant fuser 22 may be employed to permanently affix the transferred image onto the copy sheet.
  • FIG. 2 which best depicts this structure which is partially shown in FIGS. 1 and 3, the xerographic drum 2 which is rotated by motive power applied to its shaft 24 provides the final receptor of optical information projected onto it via slit mask6.
  • the xerographic aspects of the present disclosure do not constitute a portion ofthe inventive concept herein disclosed.
  • any photoresponsive medium may be used to receive and record the optical projections. Therefore, the" xerographic drum may be'replaced by a suitable photographic rnedium or any other light responsive medium. It goes without saying that in certain situations depending upon the type of recording medium utilized a drum configuration is'not necessarily desirable and a flatplate adapted for movement could also be employed.
  • the source of the optical projections which are received by the xerographic drum 2 originate, in one embodiment, from a pattern disc 26 which is driven rotatively so as to pass an annular pattern area'28 successively through an exposure zone. As will be described hereinafter, this area 28 is composed of sets of transparent light modulating patterns.
  • the exposure zone is aligned with the center line of the image path designated in FIG. 2 by reference numeral 30. Otherelements further define this exposure zone such as the optical field stop disc 32 which is driven about its axis represented bya drive shaft 34 as shown in FIG. 2.
  • optical field stop disc 32 is generally opaque to a particular illumination utilized in the recording apparatus and has transparent portions 36 thereon which correspond to segments of a spiral.
  • Each segment 36 has a radius from the center of the disc 32 which corresponds to the following equation:
  • disc 32 has three such segments 36, each of which corresponds to a set of light modulating patterns on disc 26 which are used in the recording operation.
  • each set includes alphanumeric characters comprising two alphabets, upper case and lower case.
  • each slit 38 is spaced 120 apart from adjacent slits and consequently the angle subtended by any one of the segments 36 on the optical field stop disc 32 is equal to 120. Therefore, as shown in FIG. 3 where the character area 28 of disc 26 and any portion of a segment 36 of disc 32 intersect proximate to the center line 30 of the image path, the exposure zone will be defined.
  • the exposure zone previously defined will vary about the center line 30 of the image path as a function of the aforementioned equation since the spiral segments 36 will vary in their distance from the center of disc 32. This will be seen in greater detail hereinafter in connection with discussion of FIGS. 4 and 5. It is sufficient at this time to describe the exposure zone as being the intersection of any of the segments 36 and the character area 28 of disc 26 at or near the center line 30 of the image path.
  • Both disc 32 and 26 may be formed by etching photographic emulsion which is adhered to one side of a lightweight normally transparent disc-shaped material such as plexiglass.
  • the emulsion side of the discs 26 and 32 face each other and are very closely spaced so as to permit the segments 36 and the character area 28 to be as proximate to the object plane of the projection optical system as is possible.
  • This projection optical system is represented by a collimating optical assembly generally designated by reference numeral 42 which acts to collect the light passing through the selected portion of the character disc 26 and collimate it for reflection by a main mirror 44. The light from main mirror 44 is then acted uponby two identical lenses 46. These may be achromatic doublets of conventional design and as seen in FIGS. 1 and 3 are substantially rectangular in area. They serve to focus via mirrors 48 the light reflected by mirror 44 onto the image plane represented by the surface of xerographic drum 2 exposed through slit mask 6. As is shown in FIG. 2, a support member 49 holds the lens 46 and the mirror 48 in a fixed relationship relative to each other to insure proper optical alignment throughout the operation of the apparatus.
  • the source of the light which has been described as passing through the optical system is generated by a suitable flash lamp 50 which may suitably be a xenon lamp housed in a conventional light box 52 so as to permit light to exit through an optical assembly 54 and into the exposure zone previously referred to.
  • a suitable flash lamp 50 which may suitably be a xenon lamp housed in a conventional light box 52 so as to permit light to exit through an optical assembly 54 and into the exposure zone previously referred to.
  • the description of the optical arrangement can be summarized by saying'that a character in the pattern area of disc 26 is illuminated and this object character in the character plane-is imaged at infinity by the collimating action of assembly 42.
  • the main mirror 44 reflects this collimated light to lens 46 which images that character via mirror 48 onto the image plane at the surface of the drum 2 or other photoreceptor.
  • lens 46 and mirror 48 are formed into an integral unit by an appropriate support member 49.
  • This support member is, in addition, attached to a carriage 56 which is fixed to a flexible, endless drive member 58, which may be a chain as illustrated in the drawings.
  • the chain engages two sprocket wheels 60, one of which may be driven by a suitable source of motive power not shown to move the chain 58 through its particular path as shown best in FIG. 2.
  • a plurality of carriages 56 are shown attached to the chain 58 and, as will be seen hereinafter, this number of such carriages and associated .optical units can not be less than two and may be larger.
  • FIG. 2 depicts two of these units in the optical path formed by the reflected light from mirror 44 which in part is directed by either one of the units onto the surface of drum 2 at the beginning or end of the slit in the mask 6.
  • the movement of the chain viewing FIG. 2 is in a clockwise direction as indicated by the arrows. Therefore, the lens-mirror assembly on carriage 56 on the left can be considered as having completed the projection of a line of alphanumeric information and the identical assembly on the right can be considered as initiating the next line of recorded information.
  • a stabilizing plate 64 is employed upon the edge of which in effect rides carriages 56 by way of wheels 66 which are best shown in FIGS. 1 and 2. These wheels are rotatively mounted on the same pins which attach carriage 56 to the chain 58. Because of the tension in the chain 58, the wheels 66 of the carriages 56 maintain continuous contact with the edge of the stabilizing plate 64.
  • stabilizing flanges 68 are employed to provide positive restraint on both the upper and lower portions of the periphery of wheels 66. As seen better in FIG. 1 flanges 68 are attached appropriately to respective ones of the stabilizing plates 64. This insures the very minimum of vibration in the recording zone by chain 58 and carriages 56 thereby providing little, if any, blur in the image projected onto the surface of drum 2. It is recognized that the stabilizing provisions are not necessary to the operation of the system but only enhance the quality of the resultant recording.
  • input signals representative of alphanumeric information are received by the recording apparatus and decoded so as to indicate what particular alphanumeric character is to be projected and recorded onto the surface of xerographic drum 2 at any instant of time.
  • This indication is compared with the ever changing status of the character disc in the exposure zone so that when the selected character is properly positioned at this zone, the flash lamp 50 is energized.
  • the image of the selected character is then projected through the optical system via optical assembly 42, mirror 44, lines 46, and mirror 48 to selectively discharge the xerographic drum in accordance with the optical information.
  • one of the lens-mirror assemblies on carriage 56' is moving from right to left as seen in FIGS. 2 and 3 so that a series or sequency of alphanumeric characters may be recorded in a line substantially parallel with the axis of drum 2.
  • the apparatus of the present invention is designed to project one alphanumeric character per set of alphanumeric characters. Therefore, the spacing problem is involved each time it is desired to sequentially record any two characters.
  • each slit is on a radian of disc 26 and extends from the periphery of disc 26 a short distance toward the center of the disc.
  • Each alphanumeric character in the area 28 is centered in a character space which is uniform in size for all characters. Therefore, the center of adjacent characters are uniformly spaced from each other.
  • the character slits vary in their alignment with a particular character space. As will be noted the spacing of adjacent character slits is uniform. However, the spacing or the slignment between a particular character slit and its respective character space varies depending upon the position of the respective character in its respective set. This can be seen upon close examination of FIGS. 4 and 5.
  • Character slit 69 associated with the space occupied by the upper case character A is located 0.5/52 of a character space to the right of the left-most portion of that character space. Examining the character slit 70 associated with the space occupied by the upper case character M it can be seen that this slit is removed from the left-most portion of that space by slightly less than one-fourth of the width of that character space. In FIG. 5 the character slit 72 associated with the lower case character M is shown to be removed approximately three-fourths the width of a character space from the left-most side of the character space occupied by this character.
  • character slit 74 associated with that character is located 0.5/52 .of a character space to the left of the right-most side of that space.
  • the character slits for those alphanumeric characters intermediate the characters previously referred to have associated with them similar slits which are positioned uniformly from the preceding slit.
  • each alphanumeric character both upper and lower case is centered in a uniform sized character space.
  • the character slitsas noted previously are uniformly spaced from adjacent slits but the spacing of these slits is somewhat greater than the spacing between the centers of adjacent character spaces. Therefore, in the example used in this description wherein each alphanumeric character set contains 52 symbols or characters plus one blank space and the center of adjacent characters are spaced apart by a unit designated by the constant Q, the character slit spacing between adjacent slits can be represented by Q/52 plus Q. Therefore, referring to FIGS.
  • character slit 69 associated with upper 1 case character A is aligned with an initial or zero position then character slit 70 associated with the character upper case M is then spaced along the periphery of disc 26 from character slit 69 by an amount equal to 12 (Q/52 Q).
  • character slit 72 associated with lower case character M is spaced-from character slit 68 by an equal amount to 38(Q/52 Q) and character slit 74 is similarly spaced from character slit 69 by an amount equal to 51(Q/52 Q).
  • the various slits referred to, both the character slits and slits 38 on the character disc 26 are transparent areas in the normally opaque surface of the emulsion side of the character disc 26. Therefore, these slits transmit light from an appropriate source of constant illumination which is not shown in the figures but may be a conventional low voltage lamp.
  • the light which is transmitted by these particular slits is detected by a conventional pair of photocells or photodiodes which are located inside the photocell assembly designated by reference numeral 78.
  • One photocell (referred to hereinafter as the clear photocell) exclusively monitors light passing through slit 38 while the other photocell (referred to hereinafter as the character photocell) monitors exclusively light passing through the character slits.
  • slit 38 is utilized to generate a signal to reset or clear a character counter which generates a full count when the selected character is in the exposure zone.
  • the photocells are located 120 degrees from the center of the exposure zone or from the center line 30 of the image path. This is done so as to remove the photocells from the exposure zone so that they will not obstruct the light passing therethrough.
  • the control logic through the use of a counter, which at this point registers a full count, knows that the upper case character M is in the exposure zone.
  • the exposure zone is actually defined by the intersection of the character area 28 of character disc 26 and a portion of one of the spiral segments 36 of the optical field stop disc 32. As shown in FIG. 4 this exposure zone may extend anywhere from the point represented by reference numeral 80 to the point represented by reference numeral 82. This space between these two points along a radian of disc 26 passing through center line 30 of the image path defines the upper and lower limits of the exposure zone.
  • the count of the character slits determines precisely when the flash lamp 50 will be triggered. Since the position of character photocell in assembly 78 is fixed relative to the center line 30 of the image path, the character slit associated with the particular character in the exposure zone which is porjected by the light from the flash lamp 50 will always be in the same position relative to center line 30 and coincident therewith. However, because of the unique relationship between a particular character and its respective character slit, the position of the projected character in the exposure zone will vary. For example, when the flash lamp is triggered to project the image of the upper case character A, the character itself will be to the right side as FIGS. 4 and 5 are viewed of its respective character slit and of the exposure zone.
  • the projected character will be closer to point 80 as shown in FIG. 4 than point 82.
  • it will be to the left, as FIGS. 4 and 5 are viewed, of its respective character slit and closer to side 82 of the exposure zone than side 80 thereof.
  • character slits The particular function of the character slits is best explained in relation to actual operating parameters within which the apparatus illustrated is capable of operating.
  • An initial factor which is fixed in value is the bit rate possible for transmission over standard voice grade telephone lines, viz., 2,400 bits/second.
  • Typical alphanumeric codes use 8 bits/character which dictates a maximum transmission and recording rate of 300 characters/second. Since character disc 26 carries three character sets and one character per set is projected the disc must rotate at a rate of I00 revolutions/- second in order to achieve the 300 character/second recording rate (3 characters/revolution is the maximum recording rate). For typical typewriter spacing, l0 character/linear inch of drum surface is required. If 84 characters are desired per line then the recording zone limited by slit mask 6 is 7 inches.
  • Disc 32 rotates in a direction as indicated by the arrow and has its rotation synchronized with that of the character disc so that one of the spiral segments 36 passesthrough the exposure zone coincidently with the passage therethrough of one of the character sets on disc 26. This is evident from the positions of the discs as depicted in FIG. 4 or 5. While FIGS. 4 and 5 do not show two characters in the exposure zone, it can be pictured when the character disc is advanced so that, for example, upper case characters A and B are in the exposure zone together. In that situation, the optical field stop disc 32 would block character As projection and permit the projection of character B via transparent segment 36.
  • FIGS. 4 and 5 From a consideration of FIGS. 4 and 5, it can be seen that the same movement of the characters within the exposure zone as delimited by sides 80 and 82 thereof can be accomplished by a single disc 200, illustrated in FIG. 7, which disc combines the features of both the disc 26 and 32.
  • the A of FIG. 4 when in its correct position i.e., between the center line 84 and the side could betransferred from the character disc 26 to the aperture disc 32 in exactly the orientation shown.
  • Each successive character, therefore, B, C, etc. could be also placed on the aperture disc when in its correct position as it moves through the exposure zone.
  • the resulting character set formed on the aperture disc will follow the spiral segment 36 thereby resulting in a spiral segment 202 containing a complete set of characters as shown in FIG. 7.
  • the other spiral segments would be formed in the same manner.
  • the resulting spiral segments each have a radius from the center of the disc 200 which corresponds to the equation:
  • R is the radius of a segment measured from the center of the disc 200
  • R is the shortest radius of the segment as measured from the center
  • K is a constant
  • 0 is the angle subtended by R and R
  • a set of character slits 204 for each character set is positioned on the disc 200. Unlike the slits of the disc 26, the slits 202 are positioned in exactly the same position relative to their associated character spaces.
  • a fixed aperture structure 208 having an aperture 210 disposed in the exposure zone will prevent adjacent characters from being partially projected.
  • the recording zone in a typical recorder may be approximately 7 inches long and is defined by the opening in the slit mask 6 in the direction of the drums axis.
  • the spacing of the lens-mirror units is such that the dis-;
  • each lens 46 focuses the same character being projected at that instant of time. This is made possible by utilizing Huygens theory that the wave front of light emission can at any future time be determined by assuming that every point on a given wave front acts as the center of a new disturbance emanating from that point. In other words, a new wave front can be found by treating each point of the old wave front as a new source oflight from which a secondary wavelet emanates in all directions.
  • FIG. 6 schematically depicts the logic circuitry employed to control the recording process.
  • the apparatus of this invention can be used on the receiving end of a standard voice grade telephone link over which is transmitted coded groups of binary bits representative of information or data as well as various control words.
  • bit groups are received by the circuit of FIG. 6 at an input terminal 3 which serially supplies these bits to the input of a conventional shift register 5 and to a conventional clock bit recovery circuit 7.
  • the latter provides suitable recovered clock pulses to a counter 9 of conventional design which has a full count capacity equal to the number of bits employed to represent a particular alphanumeric character.
  • Circuit 7 also supplies these recovered clock pulses to the shift input of the shift register 5 which shift the bits of the bit group thereinto.
  • the recovered clock pulses are also provided as an input to gate 11 and detector 13.
  • these pulses actually serve to enable an input gate in the detector 13 so that the detector can decode certain code words temporarily stored in the shift register 5.
  • Code words such as SYNC and START are decoded by this conventional detector circuit 13 which may be comprised of various gate combinations as is well known in the art.
  • the two outputs of the detector 13 are labeled Start and Sync. Each of these outputs will be energized when the proper word is detected as being stored in the shift register 5.
  • shift register 5 In addition to the parallel output to the detector 13, shift register 5 also has a parallel output to a conventional eight stage digital register 15 which, in turn, has parallel outputs to another identical register 17 and so on until an eighth such digital register 19 is reached. These registers serve as a very short buffer for the code groups before and during the recording process.
  • photocell housing 78 houses two photodetectors referred to as a clear photodetector and a character photodetector which detect the presence of slits 38 and the character slits, respectively, of the character disc 26. These two photocells or photodetectors are coupled to suitable amplifiers 21 and 23, respectively, via input terminals 25 and 27 associated therewith.
  • the character photocell and amplifier 23 provide a signal each time one of the character slits passes the photocell. This signal consitutes what will be referred to as simply a clock pulse, in distinction to the recovered clock pulse. Such a clock pulse is supplied to many sub-systems of the circuit of FIG. 6.
  • the character counter 29 receives them to index its count.
  • the flash lamp trigger gate 31 and the register load circuits 33 receive these clock pulses to respond in a particular manner to be described hereinafter.
  • the clear photocell and amplifier 21 provide a clear signal indicative of each time one of the slits 38 on the character disc passes housing 78. These signals serve many roles, one of which is to clear or reset the character counter 29 to its initial condition, for example, zero.
  • the eight logic gates represented by block 35 are enabled by a delayed clear signal, which permits the complement of the contents of the eighth register 19 to be loaded into the character counter 29.
  • these clear pulses or signals serve as one input to gate 37 and to set flip-flop 39 for purposes to be described hereinafter.
  • output terminal 41 which, via an inverter 43, couples the output trigger signal generated by trigger gate 31 to the flash lamp previously referred to in connection with the description of FIGS. I and 2.
  • output terminal 45 which is coupled to suitable control relays initiating particular sub-systems in the xerographic process area such as the pre-exposure corotron and xerographic drum drive thereby preparingthe photoreceptor for the recording step as well as other drives for the chain 58 and discs 26 and 32.
  • the circuit of FIG. 6 receives sync bit groups first which are shifted into shift register 5, detected by detector 13, and indicated as a pulse to an in sync circuit 76 which may be of any suitable design to monitor a sequence of received sync pulses.
  • An in sync condition is indicated by a signal at terminal 51 which can be coupled to other circuits responding to such a condition.
  • This in sync signal is provided to reset all the flip-flops included in the register load circuits 33 as well as flip-flops 55 and 57.
  • inverter 59 coupled to terminal 51, an inverse signal of opposite polarity to that of the in sync signal is supplied to reset flipflop 61. Practically, this means that once the recording apparatus reaches an in sync condition, the flip-flops mentioned above as being coupled to terminal 51 are placed in an initial reset condition.
  • a START word is transmitted to the recorder which, like the SYNC words, is shifted into shift register and detected by detector 13. It should be noted that because of the design of the logic controlling the loading of the eight digital or buffer registers, none of the SYNC words are initially'translated to these registers from the shift register 5. The same is true for this first START word. However, this first START word does act to enable gate 11 and, upon the trailing edge of the output signal therefrom, places flip-flop 55 in a set condition. This occurs on the trailing edge of one of the recovered clock pulses. However, due to the propagation time inherent in the flip-flop 55 gate 63 remains disabled.
  • this first START word is required when a xerographic recording medium is utilized to permit preparation of the xerographic process stations.
  • the level at output terminal 45 is also used to begin the chain drive which moves the lens-mirror units through the recording zone.
  • the other inputs to this gate 65 originate from the counter 9, character photocell amplifier 23, and latch 67 consisting of gates 69 and 71.
  • the first twoof these inputs can be considered at a high level.
  • the latch its gate 69 monitors two inputs: one from counter 9 and the other from gate 71.
  • This second gate 71 monitors the output of gate 69 and the reset output of flipflop 53 in the register load circuit33 which controls the loading of the second buffer register 17. Sinceflip-flop 53 is initially in a reset condition by action of the in sync signal, it supplies a high level signal to gate 71.
  • latch 67 The results of these inputs on latch 67 is to provide a high level signal to gate 65 to be translated into a trailing edge by gate 65 and inverter 73 thereby setting flipflop 61. A high level condition is then created at the output side of inverter 75, the input of which is coupled to the output of gate 77. This high signal is sufficient to enable the loading of the first buffer register with the contents of shift register 5. This would be-the first character after the second START word.
  • Gate 83 monitors the clock pulses, the set output of flip-flop S3, andvan output from the next circuit 33 downstream. This output comes from the reset output of the flip-flop included in that particular load register circuit 33. Since that flip-flop would be initially in a reset condition, this is a high level'signal. Therefore, with flip-flop 53 in an initially set condition, the output level of gate 83 goes high-low-high and, accordingly, the output level of inverter 85 goes low-high-low providing an enabling pulse to the second buffer register 17 to permit the word to continue its slide toward the last of the buffer registers. This same operaton continues to let the word go' from one buffer register to the next succeeding one until it ends up in the eighth register 19.
  • Thetechnique of loading the last or eighth register 19 differs somewhat from that which has been described in connection with the other buffer registers.
  • the loading of this register 19 is controlled in the first instance by gate 87 which has two -inputs;.from two other'gates 89 and 91.
  • gate 89 monitors an output from the preceding register load circuit 33 which comes from inverter 85's counterpart therein. In addition to this, it monitors the reset output of flip-flop 93.
  • this flip-flop is in a reset condition at this time and hence a high level signal is at one of the inputs to gate 89. Since the output of the inverter in the circuit 33 just upstream from the last register goes through the same level changes as was described in connection with inverter 85, that input to gate 89 will experience a lowhigh-low level transition. During the high level, the output of gate 89 will be low thus providing a high level the next successive downstream cirload pulse at the output of gate 87 effecting the loading of the last register 19.
  • gate 37 The role of gate 37 is to indicate to flip-flop 93 when the last two buffer registers are loaded so that the recording process can begin.
  • This signal from gate 37 is not translated to flip-flop 93 until a character set begins its pass through the exposure zone previously described, i. e., a clear signal is supplied to gate 37 from the clear photocell. At this point flip-flop 93 will be set and a signal will emanate from the set output of this flip-flop and be translated to one input of gate 97. Before following through the explanation of this gate and its other input, reference should be first made to what other events take place at the initiation of the signal.
  • the clear signal clears the character counter 29 after a predetermined time from which, dictated by delay circuit 99, the complement of register 19 is transferred or loaded into counter 29 via gates 35 enabled by the delayed clear pulse.
  • the complement of the register 19, when once loaded into the character counter 29, is augmented by one as each character in the particular character set passes through the exposure zone.
  • the code for the characters is so chosen that when the counter reaches its full count, the character represented by the code word in register 19 will be at the exposure zone. For example, if the desired character to be recorded was an upper case character M, then its code or bit group could be 00001 101 which would have slid into register 19.
  • the complement of this number, 111 10010 would be loaded via gates 35 into the character counter 29.
  • each character in the set passed the character photocell its respective character slit would be detected and a clock pulse generated which would be supplied to counter 29 to increase its contents by one.
  • One input is from flip-flop 103 which is set upon the coincident occurrence of two events: a signal from flipflop 93 and a high level signal from input terminal 105.
  • This latter signal can be generated in several ways and is used to insure that the moving optical systems will be in the right position relative to the recording zone when projection begins. Therefore, a microswitch or photocell system can be used to insure that when this signal is generated the chain 58 is in a predetermined position.
  • Another input to the trigger gate 31 is from the clock pulse source, character photocell amplifier 23.
  • the final input to this gate comes from the output of gate 107 which monitors the reset output of flip-flop 39 and the output of trigger gate 31 itself.
  • the output of trigger gate 31 is normally high and flip-flop 39 is set by the clear pulse from amplifier 21.
  • a low level pulse disables gate 107 and triggers monostable multivibrator 109 which, in turn, disables gate 91. Since the'automatic set and reset inputs of the flip-flops used in FIG. 6 are level sensitive, during the disabled condition of gate 91, flipfiop 39 is reset. In addition, flip-flop is reset. Since the reset output of the flip-flop feeds back to the next preceding register load circuit 33, specifically as one input to gate 83 and the input gate associated with the input of flip-flop 53 therein, the output of this gate 83 goes low permitting the output of its respective gate 79 to go high providing the penultimate buffer register with a loading pulse.
  • the low level pulse from gate 91 also is supplied as one input of gate 87 thereby permitting this gate to supply the last register 19 with a load pulse also so that it can accept the contents of the penultimate register.
  • affirmative loading is used in the stream of buffer registers so that zeros can be loaded from one register to another without first clearing the latter.
  • the first word . was located in the last register. Therefore, suitable detecting gates can be incorporated into detector 110 which monitors the contents of register 19. The detector also detects other control words such as SPACE, STOP, and SYNC. When it detects one of thesewords, it translates an inhibit signal to output terminal 41 which effectively inhibits the energization of the flash lamp even though all conditions at the input to gate 31 are satisfied.
  • suitable detecting gates can be incorporated into detector 110 which monitors the contents of register 19.
  • the detector also detects other control words such as SPACE, STOP, and SYNC. When it detects one of thesewords, it translates an inhibit signal to output terminal 41 which effectively inhibits the energization of the flash lamp even though all conditions at the input to gate 31 are satisfied.
  • a character disc having a set of characters arranged in a spiral configuration relative to the center of said character disc, each character being spaced apart less than one character space;
  • acter disc has a plurality of sets of characters uniformly spaced on said disc.
  • R is the shortest radius of said configuration
  • K is a constant, and 0 is the angle subtended by the radius of said spiral configuration and R 5. Structure as specified in claim 4 wherein said characters are transparent.

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  • Physics & Mathematics (AREA)
  • Engineering & Computer Science (AREA)
  • Optics & Photonics (AREA)
  • General Engineering & Computer Science (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Light Sources And Details Of Projection-Printing Devices (AREA)
US00100988A 1970-12-23 1970-12-23 Projection stencil assembly Expired - Lifetime US3750539A (en)

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US10098870A 1970-12-23 1970-12-23

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US (1) US3750539A (it)
CA (1) CA955446A (it)
DE (1) DE2162516A1 (it)
GB (1) GB1380703A (it)
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NL (1) NL7117694A (it)

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4226514A (en) * 1979-09-04 1980-10-07 Anfilov Igor V Electrographic photocomposing machine
US4291971A (en) * 1979-09-04 1981-09-29 Anfilov Igor V Electrographic photocomposing machine
WO1990014642A1 (en) * 1989-05-19 1990-11-29 Coherent Hull Limited An optical stencil
US5434600A (en) * 1990-06-25 1995-07-18 Schoonscan, Inc. Illumination module for bandwise imaging device

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2244497A (en) * 1939-09-27 1941-06-03 Joseph T Mcnaney Recording device
US2670665A (en) * 1949-03-17 1954-03-02 Graphic Arts Res Foundation In Optical system for photographic composing apparatus
US3124034A (en) * 1964-03-10 edhouse
US3249028A (en) * 1963-04-01 1966-05-03 Photon Inc High speed photorecorder

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US3124034A (en) * 1964-03-10 edhouse
US2244497A (en) * 1939-09-27 1941-06-03 Joseph T Mcnaney Recording device
US2670665A (en) * 1949-03-17 1954-03-02 Graphic Arts Res Foundation In Optical system for photographic composing apparatus
US3249028A (en) * 1963-04-01 1966-05-03 Photon Inc High speed photorecorder

Cited By (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4226514A (en) * 1979-09-04 1980-10-07 Anfilov Igor V Electrographic photocomposing machine
US4291971A (en) * 1979-09-04 1981-09-29 Anfilov Igor V Electrographic photocomposing machine
WO1990014642A1 (en) * 1989-05-19 1990-11-29 Coherent Hull Limited An optical stencil
US5434600A (en) * 1990-06-25 1995-07-18 Schoonscan, Inc. Illumination module for bandwise imaging device

Also Published As

Publication number Publication date
DE2162516A1 (de) 1972-07-13
CA955446A (en) 1974-10-01
NL7117694A (it) 1972-06-27
IT944213B (it) 1973-04-20
GB1380703A (en) 1975-01-15

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