RU2029329C1 - Data indication liquid-crystal device - Google Patents

Abstract

FIELD: data indication devices. SUBSTANCE: device has liquid-crystal light modulator, light source, optical system, photosensitive electrophotographic cylinder, print control unit which has buffer memory, controller, three shift serial-parallel registers, two memory registers, data signal amplifier two linear arrays, two linear arrays of logic elements, scanning signal amplifier linear array. Liquid-crystal light modulator is made in form of two glass plates with air-tight cavity filled with liquid-crystal material. Plates have N data electrodes and M scanning electrodes onto their internal surfaces. Each data electrode is connected with group of transparent windows disposed at the point of intersection of data electrodes and scanning electrodes. There are rows of transparent windows onto scanning electrodes. Distance between the rows is 1=kh+h/M, where k is integral positive number, h is size of windows. Crossed polarizers are disposed onto external surfaces of the plates' orienting coverings are applied onto internal surfaces. Multiplex control is realized in the device, as a result, number of control circuits is reduced and density of printing may be improved. EFFECT: improved efficiency of operation. 2 tbl, 12 dwg

Description

 The invention relates to techniques for recording information, namely to electrophotographic printing devices, and can find application as a high-speed shock-free printer for computers.

 Currently, laser printers with electrographic modules having high image quality are widely known [1].

 The disadvantage of laser printers is the use of an optical-mechanical beam scanning system, which reduces reliability and increases the dimensions of the device.

 A Casio LCS-240 liquid-crystal page printer [2] is known, comprising a liquid crystal light modulator (LCMS) with a nematic liquid crystal (LCD) layer, in which 2464 optical shutters are controlled by a two-frequency method with a multiplex factor of 1/2. The printer has a resolution of 300 dpi, print speeds of up to nine pages per minute.

 The disadvantages of the printer are the low multiplexing coefficient and a large number of control integrated circuits, low contrast 4: 1, which reduces the print quality of the image.

 Closest to the invention, the technical solution is an imaging device [3], containing LCMS with a ferroelectric LCD layer, made in the form of two glass plates with a sealed cavity having mutually perpendicular data electrodes and scanning electrodes on the inner surfaces forming a matrix of transparent cells with an LCD -layer, and crossed polarizers on the outer surfaces of the plates, a light source, an optical system, a photosensitive electrographic cylinder. The print control unit includes a buffer frame memory, the information input of which is the device data input, a first shift register, a parallel-parallel memory register, a line of data amplifiers, the outputs of which are connected to the contacts of the LCMS data electrodes. The second shift register and amplifiers form the scanning signals supplied to the scanning buses of the LCD. The use of a ferroelectric LCD layer with optical bistability in the device allows increasing the multiplexing coefficient.

 The disadvantage of this device is the limitation of resolution, due to the use of only one line of data amplifiers, which affects the image quality. Another disadvantage is the low reliability of the LCD, due to the destructive effect of the uncompensated DC component in the control signal.

 The essence of the invention is that in an LCD device for recording information containing LCMS, made in the form of two glass plates with a sealed cavity having on the inner surfaces of N data electrodes and M scanning electrodes forming transparent cells with an LCD layer at the intersections and crossed polarizers on the outer surfaces of the plates, a light source, an optical system, a photosensitive electrophotographic cylinder and a print control unit including a buffer frame memory, information input which is the data input of the device, the first shift register, the data input of which is connected to the data output of the buffer memory, the first memory register, the inputs of which are connected to the outputs of the shift register, the first line of data amplifiers whose outputs are connected to the LCMS data electrodes, the second shift register, outputs which is connected to the inputs of the amplifiers of the scanning signals, the controller, the input of which is the control input of the device, the address output is connected to the address input of the buffer memory, the first output is connected is accessible to the clock input of the first shift register, the second output is to the control input of the memory register, the third output is to the data input of the second shift register, the fourth output is to the clock input of the second shift register, the outputs of the first line of amplifiers are connected to odd data electrodes, and also that a second line of data amplifiers is introduced into the device, the outputs of which are connected to the even electrodes of the LCMS data, the third shift register, the data input of which is connected to the output of the buffer memory, the second memory register, the input whose data is connected to the outputs of the third shift register, and the control input is connected to the second output of the controller, the first line of logic elements, the data inputs of which are connected to the outputs of the first memory register, and the outputs - to the inputs of the first line of data amplifiers, the second line of logic elements, data inputs which is connected to the outputs of the second memory register, and the outputs to the inputs of the second line of data amplifiers, the controller further comprises a fifth output connected to the first control inputs of the first and watts a swarm of logic gates, a sixth output connected to the second control inputs of the first and second gates of logic gates, a seventh output connected to the clock input of the third shift register, the scanning signal amplifiers have inverting and non-inverting inputs, alternately connected to the outputs of the second shift register, electrodes data are placed on both sides along the length of the LCD, each data electrode is connected to a group of M windows located at an angle to the scanning electrodes, scanning electrodes are N rows of transparent windows with a size of length h row spacing between rows of kh + h / M, where k - is an integer.

 The introduction of a second line of data amplifiers, a second memory register, a third shift register into the device allows you to double the number of contacts of the data electrodes by placing them on both sides of the LCD, and increase the resolution of the device with the same multiplexing factor. The introduction of two additional lines of logic elements, as well as the alternate connection of the scanning signal amplifiers to the outputs of the second shift register with inverting and non-inverting inputs, allows generating control signals of a more complex shape, compensating for the DC component of the voltage, and providing LCMS control with a high multiplexing coefficient. This increases the reliability of the device. All elements of the device are interconnected functionally, work in time synchronization. The proposed distance between the rows of windows on the scanning electrodes allows you to print images with the same resolution in two coordinates. A feature of the invention is that for the operation of the device requires a special algorithm for entering data into the LCD.

 A functional diagram of the device is shown in FIG. 1; in FIG. 2 shows a LCMS, side view; in FIG. 3 shows a plate with data electrodes; in FIG. 4 - plate with scanning electrodes; in FIG. 5 shows the relative position of the data electrodes and the scanning electrodes; in FIG. 6 shows the organization of pixels in an image; in FIG. 7 shows timing diagrams of voltages and optical response of an LCMS; in FIG. 8 shows a possible circuit implementation of logic elements; in FIG. 9-11 show the structure of the LCD cell and its switching under the action of an external field; in FIG. 12 shows a control characteristic of an LCD cell.

 The LCD information recording device (Fig. 1) contains an LCMS 1, a light source 2, an optical system 3, a photosensitive electrophotographic cylinder 4, a print control unit 5, which includes a buffer frame memory 6, the information input 7 of which is the device data input, the first the shift register 8, the data input of which is connected to the data output of the buffer memory 6, the first memory register 9, the inputs of which are connected to the outputs of the shift register, the first line of 10 data amplifiers, the outputs of which are connected to an odd electronic I will give the LCMS data, the second shift register 11, the outputs of which are connected to the inputs of the amplifiers 12 of the scan signals, the controller 13, the input 14 of which is the control input of the device, the address output is connected to the address input of the buffer memory 6, the first output is to the clock input of the first shift register 8 , the second output is to the control input of the memory register 9, the third output is to the data input of the second shift register 11, the fourth output is to the clock input of the second shift register 11, the second line of 15 data amplifiers, the outputs of which connected to the even electrodes of the LCMS data, the third shift register 16, the data input of which is connected to the output of the buffer memory 6, the second memory register 17, the data inputs of which are connected to the outputs of the third shift register 16, and the control input is connected to the second output of the controller 13, the first line 18 logic elements, the data inputs of which are connected to the outputs of the first memory register 9, and the outputs - to the inputs of the first line of 10 data amplifiers, the second line of 19 logic elements, the data inputs of which are connected to the outputs of the second reg tra memory 17, and outputs - with the input of the second data line 15 amps. The controller 13 further comprises a fifth output connected to the first control inputs of the first 18 and second 19 lines of logic elements, a sixth output connected to the second control inputs of the first 18 and second 19 lines of logic elements, a seventh output connected to the clock input of the third shift register 16. The amplifiers 12 of the scanning signals have inverting and non-inverting inputs, alternately connected to the outputs of the second shift register 11.

 ZhKMS 1 (Fig. 2) is made in the form of two glass plates 20 and 21 with a sealed cavity 22 filled with an LCD material 23. The plate 20 has N data electrodes 24 placed on both sides along the length of the ZhKMS. Plate 21 has M scan electrodes 25. Each data electrode 24 is connected to a group M of transparent windows 26 located at the intersection of the data electrodes and the scanning electrodes at an angle to the scanning electrodes. Scanning electrodes 25 have rows of transparent windows 27 of size h along the length of the scanning electrode. The distance between the rows of windows 27 l = kh + h / M, where k is a positive integer. Crossed polarizers 28 and 29 are placed on the outer surfaces of the plates 20 and 21. Orienting coatings 30 and 31 are applied on the inner surfaces of the plates 20 and 21.

 LCD information recording device operates as follows.

In RAM 6 write a rasterized image of the registered page. The source of information data can be an external computer when the device is used as a printer, a scanner with digital processing when working in a copy machine, a fax-modem card when working in a fax machine, etc. According to the signals from the electrographic module, arriving at the control input 14 of the controller 13, the registration process begins. LCD has M scanning electrodes 25 S ₁ , S ₂ , ... S _m . The data electrodes 24 are designated D ₁ , D ₂ , ..., D _N. Each data electrode is connected to a group of transparent M windows. The LCD cells of the optical shutters at the intersections of the data electrodes and the scanning electrodes form a matrix. As a result of the movement of the surface of the electrographic cylinder 4 and the synchronous control of the inclusion of gate cells, an image consisting of an ordered set of pixels is recorded (Fig. 4). On the electrodes 25 of the scan cyclically with a period of T _c from the amplifiers 12 of the scan signals are supplied scan voltage. At each scanning electrode, the scanning voltage acts for a time t _ck = T _c / M. The interval t _ck consists of four clock cycles: t ₁ = t ₂ = t ₃ = t ₄ , during which a negative erase pulse with an amplitude -V _o in the interval t ₁ and a positive write pulse with an amplitude V _o in the interval t _{3 are formed} . At adjacent scan electrodes, the scan voltages are shifted in time by t _ck (Fig. 7a-d). From the output X4 of the controller 13, the pulses with a period t ₀ - t ₁ are received at the clock input of the second register 11. At the beginning of each scan cycle from the output X3 of the controller 13 to the data input of the second register 11 for a time shorter than t _o , a logical "1" (hereinafter referred to as "1") is received. The inverting and non-inverting inputs of the amplifiers 12 of the scanning signals are alternately connected to the odd outputs of the second shift register 11 having a 4M resolution. On the interval t _SK while recording new information in the LCD cells of one row, the following operations are performed.

On the interval t ₁ , the LCD cells of the row are turned off by the erase pulse -V ₀ , the load of the shift registers 8 and 16 is finished by data from RAM, the signals P ₁ = "1" and P ₀ = "1" are formed at the outputs X5 and X6 of the controller 13 .

On the interval t ₂ parallel data is transferred from the shift registers 8, 16 to the memory registers 9, 17. At the outputs X5 and X6 of the controller 13, signals P ₁ = "0" and P ₀ = = "0" are simultaneously generated.

On the interval t ₃ , the write pulse + V ₀ is turned on at the scanning electrode, and the units of the write enable signal are output to lines 18 and 19: P ₁ = "1", P ₀ = "0". On the interval t ₃ , the filling of the shift registers 8 and 16 begins with new data for recording the next row of cells, the duration of filling the shift registers 8 and 16 can be t _ck - t ₀ .

On the interval t ₄ from the output X6 of the controller 13, a signal for recording zeros is issued: P ₁ = "0" and P ₀ = "1". The shift register is being filled with new information.

 As a result, data signals are generated at the outputs of data amplifiers 10 and 15 in accordance with Table. 1. truth.

Timing diagrams of voltages U _d for cases of switching on a cell ON and not turning on a cell OFF are shown in FIG. 7d A possible circuit implementation of the logic elements for one LCMS data electrode is shown in FIG. 8.

In the gap of the ith LCD cell on the interval t _c the difference voltage U _si -U _di acts (Fig. 7e). For all LCD cells, the negative erase pulse is -3V _o / 2. For positive pulse LCD included cells record is + 3V _0/2. For non-switchable LCD cells, the positive write pulse does not exceed + V _o / 2; Moreover, the form of stresses U _s - U _d for all cases has a zero constant component. This increases the life of the LCD.

In the proposed device, the ferroelectric chiral smectic С ^* with a bistable threshold characteristic can be used as an LCD material. The manufacture of the LCD composition, orienting coatings of the inner surfaces of the cells, and the filling of the LCD material in the LCMS are performed so that in the LCMS the directors of the LCD molecules form an ordered structure stabilized by the surfaces of the orientation coatings and consisting of many layers perpendicular to the surfaces of the glass plates 20 and 21. B the absence of an external electric field, the long axes of the molecules (directors N) are located at a certain polar angle θ to the layer surface (Fig. 9), and the azimuthal angle φ takes the values +90 or - 90 ^° . The dipole moments of the molecules P _{s are} perpendicular to the director N and lie in the plane of the smectic layer. Under the action of an external electric field E ₁ , perpendicular to the plane of the glass plates of the LCMS, a torque arises, which orientes all the LCD molecules either to position N1 (Fig. 10) or to position N2 with the opposite direction of the electric field E ₂ (Fig. 11) . The LCD cell is equivalent to a plate of a uniaxial electro-optical crystal and, in one of the director's positions, rotates the plane of polarization of the transmitted light by 90 ^° . Moreover, in crossed polarizers, the LCD cell transmits light, i.e. "turn on". In another direction of the electric field, the LCD cell is “off” and does not transmit light.

To work in the proposed device with multiplex control, the LCD cell must have a hysteretic control characteristic (Fig. 12), which is achieved by the choice of the LCD material and manufacturing technology. Possible values of the LCMS parameters: the gap value is 2-5 μm, the electric field strength is 3-8 V / μm, the rise-fall time of the optical response is 30-50 μs, and the optical contact is 8-10. Transparent conductive coatings in the LMC can be made of In ₂ O ₃ , SnO ₂ , IT0. The optical response of the on and off cells is shown in FIG. 7g

To print the image in the form of an ordered set of pixels (Fig. 6), the device uses a special algorithm for entering data into the LCD. Consider this algorithm for the multiplexing coefficient M = 4. Let us take the size of the LCD cell to hxh, the distance between the rows of windows on the scanning electrodes is l, with l> h. The optimal value is l = kh + h / M, where k is a positive integer. For design reasons, taking into account the topology of the scanning electrodes and data electrodes, we take k = 2, i.e., l = 2.25 h. The print cycle T _c = = h / V _x , where V _x is the linear velocity of the electrophotographic cylinder (we believe that the optical projection system has an increase of +1). Suppose that the image contains four N x R piksedov and printed for R x T _n cycles. Each cycle contains M = 4 scan intervals of duration t _ck . Then inside the cycle i there are M = 4 subcycles i ₁ , i ₂ , i ₃ , i ₄ . For printing an image with pixel organization shown in FIG. 6, in each sub-cycle, information about the pixels with addresses (table 2) should be received on the data electrodes D ₁ , D ₂ , ..., D _n .

 Here p takes integer values 0 - (N-1).

According to the created algorithm, taking into account the real organization of RAM addresses, the controller 13 addresses and sends data to the shift registers 8 and 16. At the same time, data is sent to register 8, starting from the last pixel of the row, and to register 16, starting from the first pixel of the row. This allows the use of the same control board designs for even and odd electrodes of LCMS data. As a result of applying such an algorithm, for example, the pixels of the row i, (2 + 4p) are printed in the cycle i + 2, i.e. their printing is delayed in time by 2T _c + T _c / 4 relative to the printing of row i, (1 + 4 _p ). Since the spatial displacement of the rows of windows on the scanning electrodes is 2 h + h / 4, a combination of all the pixels of row i in one line is achieved. At the same time, the print density is the same in two coordinates and amounts to 1 / h dots per millimeter (h is measured in millimeters).

The proposed device allows to obtain a print density of 12 dots / mm, print speed of 6-12 pages per minute. At a speed of 12 pages per minute, the print cycle T _c = 1.2 ms, the scan interval 300 μs, the interval t ₀ = 75 μs. During this time, the LCD cell is turned on or off. Addressing RAM and filling shift registers 8, 16 are performed for the time t _hell = 3t _{0 =} = 225 μs. A total of 512 cells are addressed. The addressing time of one cell is 0.5 μs, which is quite achievable for controllers with a clock frequency of 10-12 MHz. As a light source in the device, a fluorescent slit lamp, a linear metal halide lamp or a spot lamp with a light guide shaper can be used. The proposed LCD information recording device is compact, high quality printing and can be widely used in shock-free printers, digital copiers, facsimile electrographic devices.

Claims (1)

 A liquid crystal information recording device containing sequentially optically coupled light source, a liquid crystal light modulator, made in the form of two glass parallel plates with a sealed cavity between them, filled with a liquid crystal, on the inner surface of one of which N parallel strip data electrodes are placed, and on the inner surface the other - M parallel strip scanning electrodes, forming transparent cells at the intersections, and on the outer surfaces x plates — crossed polarizers, an optical system and a photosensitive electrophotographic cylinder, as well as a print control unit including a buffer frame memory, the information input of which is the device data input, the first shift register, the data input of which is connected to the buffer memory data output, the first register memory, the inputs of which are connected to the outputs of the shift register, the first line of data amplifiers, the outputs of which are connected to the data electrodes of the liquid crystal light modulator , scanning signal amplifiers, a second shift register, the outputs of which are connected to the inputs of scanning signal amplifiers connected to the scanning electrodes, a controller whose input is a control input of the device, the address output is connected to the address input of the buffer memory, the first output is to the clock input of the first shift register , the second output is to the control input of the first memory register, the third output is to the data input of the second shift register, the fourth output is to the clock input of the second shift register characterized in that the outputs of the first line of data amplifiers are connected to odd data electrodes, a second line of data amplifiers is added to the device, the outputs of which are connected to even data electrodes of a liquid crystal light modulator, the third shift register, the data input of which is connected to the output of the buffer memory, the second a memory register, the data inputs of which are connected to the outputs of the third shift register, and the control input - with the second output of the controller, the first line of logic elements, inputs the data of which are connected to the outputs of the first memory register, and the outputs - to the inputs of the first line of data amplifiers, the second line of logic elements, the data inputs of which are connected to the outputs of the second memory register, and the outputs - with the inputs of the second line of data amplifiers, the controller additionally contains a fifth output, connected to the first control inputs of the first and second line of logic elements, the sixth output connected to the second control inputs of the first and second line of logic elements, the seventh output connected to the input activating the third shift register, and the scanning signal amplifiers are made with inverting and non-inverting inputs, are alternately connected to the outputs of the second shift register, each scanning electrode is made with N transparent sections along its length, forming a row, the distance between the rows of windows of adjacent electrodes is equal to kh + h / M, where k is a positive integer, h is the size of the side of the square, and the transparent areas are displaced in each subsequent row relative to the previous one by the value of h, the contact pads are even Odd and odd data electrodes are placed on two opposite sides of the inner surface of the plate, each electrode is made with M transparent sections in the form of squares, with side h optically aligned with the corresponding translucent sections of the scanning electrodes, the last even data electrode being informationally connected with the first output of the third shift register .

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