Abstract: An optical writing head in which the number of bus lines to be derived may be decreased by using a self-scanning light-emitting element array is provided. A &PHgr;1 bonding pad of each SLED chip is connected to &PHgr;1 bus line via a resistor R1, and a &PHgr;2 bonding pad of each SLED chip is connected to &PHgr;2 bus line via a resistor R2. &PHgr;S bonding pad is connected to a &PHgr;S bus line via resistor RS, and VGA bonding pad is connected to VGA bus line. &PHgr;I bonding pad of each SLED chip is connected to a corresponding one of terminal &PHgr;I(1)-&PHgr;I(56) of a connector.

Abstract: A drive circuit drives a plurality of light emitting diodes (LED) in an LED array chip. The drive circuit includes a row of drive transistors that supply drive currents to corresponding LEDs, a control circuit that produces a control voltage for driving the drive devices, and a supply voltage electrode that extends along the row. The control circuit has a reference current transistor through which a predetermined reference current flows in accordance with a control voltage applied to the reference current transistor. The control voltage is also supplied to the individual drive devices to cause the drive currents to flow through the corresponding LEDs in reference to the reference current. The supply voltage electrode supplies a supply voltage to each of the drive transistors such that each drive transistor receives its supply voltage from a nearest location on the supply voltage electrode. The reference transistor receives its supply voltage from a substantially mid point of the supply voltage electrode.

Abstract: An image forming apparatus with a plurality of driven elements has a memory for storing driving data on each of the driven elements for driving the driven elements, and a computing unit that reads, from the memory, driving data on a driven element corresponding to a dot of interest and driving data on at least one driven element corresponding to at least one dot included in an area of predetermined dimensions in which the dot of interest is included, and produces corrected printing data based on the driving data read from the memory and on printing data on the dot of interest input from a higher control unit. The image forming apparatus performs printing by driving the driven element corresponding to the dot of interest by use of the corrected printing data.

Abstract: A self-scanning light-emitting device is provided in which the amounts of light of light-emitting elements may be corrected to make the distribution of amounts of light in a luminescent chip or among luminescent chips uniform. The correction for amounts of light of light-emitting elements may be carried out by regulating the time duration of on-state of a light-emitting element or the voltage of a write signal applied to a light-emitting element. According to the present invention, the distribution of amounts of light becomes uniform, so that the printing quality of a printer using such self-scanning light-emitting device is improved.

Abstract: A print head includes a driving circuit having a cascaded series of driver integrated circuits mounted on a printed wiring board. Differential clock signals are supplied to the driver integrated circuits to synchronize the transfer of print data through the cascaded series. Even-numbered driver integrated circuits and odd-numbered driver integrated circuits are connected differently to the clock signal lines, but the even-numbered (or odd-numbered) driver integrated circuits generate an inverted internal clock signal, thereby compensating for the difference. This enables the clock signal lines to be mutually adjacent and to have a weaving layout that yields improved noise immunity.

Abstract: In an optical printing apparatus, an image having a high image quality is desirably produced under stable condition, even when variations occur and exposure conditions are different from each other, which are caused by differences in response speeds of a light source and a liquid crystal shutter element, and also by differences in element driving conditions. The optical printing apparatus is arranged by including: image data input for inputting image data; reference level generator producing a reference level; comparator for comparing multi-value data outputted from the image data input with the reference level so as to convert the multi-value data into binary data; data transferring element for transferring the binary data outputted from the comparator as head data to the print head; latch controller for latching data of the print data; and strobe controller capable of causing the print head to expose the light therefrom.

Abstract: A light-emitting device is disclosed which includes a light-emitting element array formed by arranging a plurality of light-emitting elements, a driving unit for driving the light-emitting element array to emit light from each of the light-emitting elements, a memory unit for storing the number of light emissions for each light-emitting element of the light-emitting element array, and a control unit for controlling the driving unit based on the information stored in the memory unit so that the amount of light emitted from each light-emitting element is held constant. An exposure device employing the light-emitting device, and an image forming apparatus employing the exposure device are also disclosed.

Abstract: Adjustment of correction data for the respective LEDs at the end of manufacture of a print head is performed by transferring provisional correction data from a manufacturing device to an LED driver, directly, i.e., without once being stored in a storage circuit 10c in the print head, and measuring the amounts of light from the LEDs and varying the correction data, and repeating such an operation until the correction data is optimized. The optimized correction data as well as the strobe time data determined from the measured average power are written in the storage circuit 10c. During use of the printer, the data stored in the storage circuit 10c is used for correction of the data and determination of the strobe time.

Abstract: A method and apparatus for increasing the linearity of elements within a printhead by applying a coarse electronic adjustment to rearrange the electronic printing of data into the proper pixel line and then applying a fine electronic adjustment to reduce the bow error to fraction of a pixel line. Delays of exposure control signals are used by the fine electronic adjustment to correct linearity by a fraction of a pixel line. The delays can be repeated to multiply the number of delays available and increase the linearity resolution. The delays can also be averaged between odd and even rows of elements to increase apparent resolution. The first embodiment employs digital circuitry to provide the fine adjustment of pixel data that is partially located on the interface board and partially located on the printhead substrate. This reduces the amount of circuitry placed within the ASICs on the printhead substrate.

Abstract: A fluorescent print head driving method is provided wherein an operational lifetime is improved by reducing the evaporation amount of Ba contained in an electron emitter material of a filament cathode and suppressing the deterioration of the luminous efficiency. In the pre-luminous period T1 during which luminous dots glow before forming an image on a recording medium, a grid voltage is controlled to be a predetermined voltage of a rated value or less and a filament voltage is controlled to a predetermined voltage of a rated value or less. In the print luminous period T2 during which luminous dots glow before forming an image on a recording medium, a grid voltage blank period is created corresponding to a luminous blank period between glow states during which an anode voltage is written for one line on the recording medium. The anode voltage and the grid voltage are controlled to be a rated voltage with a duty ratio corresponding to a blank period.

Abstract: A semiconductor laser driving apparatus has a laser diode that emits a laser beam, a laser driving circuit that drives the laser diode by feeding a driving current in pulses to the laser diode, a conductor that conducts the driving current from the laser driving circuit to the laser diode, and an inductance adjuster that has a conductor-pattern for conducting the driving current and adjusting the magnitude of inductance in the conductor. A part of the conductor-pattern that makes the magnitude of the inductance a proper magnitude for emitting the laser beam in generally rectangular pulses, is selectively defined and conducts the driving current as a part of the conductor.

Abstract: A laser marking system includes a high power fiber laser with a double clad fiber having a doped core surrounded by an inner pump cladding and providing an optical output for marking; a high power laser diode source for pumping the double clad fiber laser via an input into the inner pump cladding; an optical scanner coupled to receive the marking output from the double clad fiber laser to scan the output over a surface of an article to be marked by sweeping the marking output in one, two or three dimensions to form strokes, the completion of which comprises indicia to be marked on the article surface; and a controller to control the operation of the scanner synchronized with the modulation of the laser diode pump source to initiate the marking output and sweep and modulate the marking optical output in one, two or three dimensions to form strokes comprising the indicia.

Abstract: A method of controlling light emitting elements in an electrophotographic print head includes providing a predetermined number of pulse width modulators having different width output pulses, the predetermined number being less than the number of light emitting elements; selecting multiple light emitting elements for coupling to respective ones of the pulse width modulators; and coupling the multiple selected light emitting elements to the respective pulse width modulators. An electrophotographic printer includes a print head having a predetermined number of light emitting elements; a predetermined number of pulse width modulators having different width output pulses, the predetermined number being less than the number of light emitting elements; and logic circuitry configured to couple multiple light emitting elements to respective ones of the pulse width modulators.

Abstract: A method of driving a laser device in an electrophotographic machine includes providing a binary image data signal having a first switching rate. A plurality of binary encoded data signals are transmitted over a transmission medium. Each of the encoded data signals is dependent upon the image data signal and has a respective second switching rate lower than the first switching rate. The image data signal is recreated by using the encoded data signals. The laser device is driven with the recreated image data signal.

Abstract: In a digital imaging system including an array of imaging devices that apply an image to a recording medium such as a lithographic printing plate, elimination or reduction of longitudinal imaging artifacts is accomplished by blending the zones imaged by each the devices. In the course of a complete scan of the recording medium, the imaging devices each traverse a series of longitudinal columns of dot locations, and the devices are fired only at appropriate dot locations as determined by the digital image data. By operating adjacent imaging devices such that the zones they would ordinarily cover are blended in a random pattern, artifacts at the boundary between zones (such as seams) are hidden. While sufficient visual disruption to eliminate artifacts is ensured, noticeable visual artifacts are not created as a consequence of the disruption.

Abstract: A self-scanning light-emitting device is provided in which the number of bonding pads can be decreased, i.e. 2 or 3. The device comprises an array of a plurality of three-terminal light-emitting elements; electrical means having unidirectional characteristic to voltage or current for connecting the control electrodes of neighboring light-emitting elements to each other; two clock pulse lines for applying two-phase clock pulses alternately to one of two terminals except the control electrode of each light-emitting element; and a power supply line connected to each of the control electrodes of the light-emitting elements via a load resistor, respectively. The resistance of the load resistor connected to the light-emitting element to be turned on at first is selected to be smaller than that of other resistors. As a result, the bonding pad for the start pulse may be omitted.

Abstract: An optical recording method in which an effective recording sensitivity in the recording of image information on a photosensitive material is raised, whereby a productivity is enhanced owing to lowered energy (laser power) required for the recording or a heightened recording speed. An image is recorded by projecting a light beam onto the photosensitive material formed on a base material backing. The optical recording method includes the steps of: (a) successively outputting pulse light whose duty factor is at most 50%, from a light source; (b) modulating the pulse light output from the light source, in accordance with an image signal, and then projecting the modulated pulse light onto the photosensitive material; and (c) recording the image by causing the pulse light to scan the photosensitive material.

Abstract: Methods of providing lower resolution format data into higher resolution format are described. A laser printing system is provided having first and second lasers configured to receive and be driven by raster data. Image data, which is to be rendered onto a print medium is received in a first resolution format. The first resolution format is converted into a second resolution format which is greater than the first resolution format by mapping the image data to provide mapped image raster data in the second resolution format. The first laser is driven with a portion of the mapped image raster data, and the second laser is driven with another portion of the mapped image raster data.

Abstract: A print head has driver circuitry that dynamically drives a row of driven elements, such as light-emitting elements, by driving different combinations of first and second terminals. The print head includes memory circuits storing compensation data for the driven elements, and multiplexing circuits that select the compensation data according to the combination of terminals being driven, thereby enabling the compensation data to be stored in the print head despite the use of dynamic driving. The compensation data are used in adjusting the amount of energy supplied to the driven elements. The amount of compensation data to be stored may be reduced by sharing the upper bits of the compensation data among a group of driven elements.

Abstract: A laser diode in a recorder is thermally stabilized. The laser diode is used to produce a light beam, which is modulated by superimposing a basic current and a modulation current derived from an image signal, and exposes a recording material point by point and line by line. Between the exposure periods, wherein in each case one line is exposed, there are return periods, wherein the light beam is guided to the start of the next line, and wherein the laser diode is modulated for the purpose of thermal stabilization. In the return period, the laser diode is modulated with the basic current during a stabilization period, the sum of the modulation times during the exposure period and during the stabilization period being constant. In addition, during the return period, the laser diode can be modulated with a modulation current, which is derived from the inverted image signal from the preceding or the following line.

Abstract: An image recording apparatus includes an image forming device, a fixing device, a cooling device and a controller. The image forming device forms an image on a recording medium on the basis of an image signal generated by an image signal generating unit. The fixing device uses heat to fix the image formed on the recording medium, and the cooling device cools the inside of the apparatus. The controller selectively executes either a first economy mode in which the cooling device is activated and the fixing device is inactivated on the basis of a command from the image signal generating unit, or a second economy mode in which both the cooling device and the fixing device are inactivated.

Abstract: In an image forming apparatus, an image forming section forms an entire object image using at least two dot-sequence forming units. At that time, at least two image quality control sections corresponding to the respective dot-sequence forming units control an actual-image forming state of each of dots of the object image. A buffer section has a predetermined number of line-data buffers each for storing the line data of an individual line of image data received from the image-forming request source for temporary retention and is shared by the plural image quality control sections. In the meantime a data-store-and-read control section controls a data store operation and a data readout operation so as to execute the two operations in parallel.

Abstract: A method of controlling light emitting elements in an electrophotographic print head, comprises providing a predetermined number of pulse width modulators having different width output pulses, the predetermined number being less than the number of light emitting elements; selecting multiple light emitting elements for coupling to respective ones of the pulse width modulators; and coupling the multiple selected light emitting elements to the respective pulse width modulators. An electrophotographic printer comprises a print head having a predetermined number of light emitting elements; a predetermined number of pulse width modulators having different width output pulses, the predetermined number being less than the number of light emitting elements; and logic circuitry configured to couple multiple light emitting elements to respective ones of the pulse width modulators.

Abstract: An optical printer head capable of increasing a level of a light amount for exposure emitted from luminous dot trains in view of an end cool phenomenon of filamentary cathodes and reducing loss of exposure energy. A light source includes luminous dot trains each constituted by a plurality of luminous dots each including an anode arranged on an anode substrate and a phosphor layer deposited on the anode, as well as filamentary cathodes arranged above the luminous dot trains so as to extend along the trains. A memory device is arranged so as to store therein correction information for ensuring uniform luminescence of the luminous dots. Light-amount correction is carried out on the luminous dots other than those positioned in proximity to each of both ends of the luminous dot trains excluded from light-amount correction, to thereby obtain correction information on the former luminous dots, which is then stored in the memory device.

Abstract: A drive IC chip (A) has a primary surface (10) which includes a corner (11a) at which a first and a second pads (3a, 3b) are provided so that their respective centers (Oa, Ob) are deviate positionally from each other in both directions x, y. With this structure, even if two wires for electric connection are extended from the first and the second pads (3a, 3b) either in the x direction or in the y direction, it is possible to advantageously prevent the wires from becoming too close to each other into shorting contact.

Abstract: A driving circuit generates an internal control voltage that controls the driving current supplied to a group of driven elements in a printer or other device. Generation of the control voltage involves the flow of current on one or more static current paths. The driving circuit includes switching elements that open these static current paths in response to a standby command, to reduce standby power consumption of the printer or other device, and to enable quiescent-current testing of the driving circuit. The standby command may be given by a combination of signals that are also used for other purposes.

Abstract: According to the present invention, a plurality of p-type semiconductor layers 13 are formed in a single row and a first layer insulating film 12 having first opening portions 16a and an n-side opening portion 17 is formed on the layers in an n-type semiconductor block 11. On the first layer insulating film 12, p-side electrodes 14 to connect to the p-type semiconductor layers 13 at the first opening portions 16a and an n-side electrode 55 (an n-side contact electrode 55a and an n-side pad electrode 55b) to connect with the n-type semiconductor block 11 at the n-side opening portion 17 are formed. Furthermore, p-side common wirings 4 to connect with specific p-side electrodes 14 are formed via a second layer insulating film 18. The p-side electrodes 14 and the n-side electrode 55 are formed using the same conductive film material through a single film formation and patterning process.

Abstract: An optical printing device for exposing a photosensitive recording medium to form a grayscale image includes a print head having n rows of recording elements capable of exposure of different colors and aligned in a direction of advancement of the photosensitive recording medium, where n is an integer more than 1, the n rows of recording elements being spaced substantially a multiple of L×(m+k/n) apart in the direction of advancement of the photosensitive recording medium, where L denotes a distance between the centers of recording pixels according to the desired resolution of a recorded image, m is an integer of 1 or more, and k is an integer of 1 or more and less than n. The optical printing device also includes a head driver for driving the print head. Light from the print head is selectively exposed on the photosensitive recording medium to form the grayscale image.

Abstract: A variable resolution transition placement circuit in an electrophotographic imaging device allows transitions to be placed within a stream of video data so that the pixel resolution achieved over a scan line is adjustable on a pixel by pixel basis using a system clock. Pixel data defines transition positions relative to a synthesized video clock defining pixel time periods. A converter converts positions of the transitions relative to the synthesized video clock to positions relative to the system clock using a value provided by a synthesized video clock to system clock transform generator. The value can change between synthesized video clock cycles to change the pixel resolution. A synthesized video generator generates values of a synthesized video clock relative to the system clock.

Abstract: In a method for multi-beam exposure of a printing form, preferably with laser beams, a computer transmits printing form data to a distributor via a data line as a sequence of recording lines and the distributor cyclically distributes the recording lines onto the input stages of an optics head where N parallel laser beams are generated and modulated with the printing form data of the recording lines. The laser beams are subdivided into active and inactive laser beams, recording lines of the printing form are transmitted via the data line for the active laser beams, and empty lines are inserted into the transmitted sequence of the recording lines for the inactive laser beams. The empty lines contain data values with which the inactive laser beams are driven dark.

Abstract: A current control circuit including at least one bit corrector for performing full-scale activation or deactivation of a voltage to gate terminals of output units according n-bit correction data, and at least one digital to analog converter for adjusting a voltage to be applied between drain and source terminals of transistors of the output units. This circuit is used for the bit correction and gradation control.

Abstract: An optical shutter is provided in the middle of a triopical path of the recording laser. Before a recording operation of data such as the images and the characters, the optical shutter is closed and also a recording laser light is outputted from the LD at a predetermined output rate. Then, immediately before the recording start of the data, the output of the recording laser is interrupted and also the optical shutter is opened, and then the recording of the data is started. Accordingly, there can be provided the image recording apparatus which is able to set the recording laser into its stabilized output state to record immediately after the recording start and to prevent generation of the irregularity of the images, the unevenness of the line width, etc.

Abstract: An image forming device for registration of images built up of pixels (pixel patterns), provided with: one or more image registration units each including a number of image forming elements and electronic drivers in order to energize each image forming element separately to form the pixels, a control unit for controlling the various image forming functions of the image forming device, wherein the electronic drivers are provided with a circuit for measuring the output characteristic of each driver and in that the control unit determines, by reference to the measured output characteristic, any malfunctioning of the image forming element driven by the associated driver and correction means for eliminating the malfunction or eliminating the visible effect thereof on the prints produced by the image forming device.

Abstract: An optical writing apparatus including a semiconductor laser having plural light emitting elements and a single light-receiving element and plural semiconductor laser drive controlling devices. The plural light emitting elements in the semiconductor laser array are driven such that an optical writing operation at a same time per each of plural lines is performed. A commonly used LD drive controlling circuit drives the LD array. An output timing-determining device outputs a switch changing-over signal to either one of respective changing-over switches in a changing-over switch circuit. After an operational delay time of the changing-over switch elapses, an APC signal is output to an APC control section of the LD drive controlling circuit connected to a negative feedback loop formed by a changing-over operation of the changing-over switch circuit. After the completion of the APC operation, the outputting of the switch changing-over signal to the changing-over switch is stopped.

Abstract: A sharp image having excellent color balance is formed by preventing differences in the amount of light among recording heads. When forming an image using at least two recording heads, each having transfer thyristors and light-emitting thyristors arranged in the form of an array, by causing the transfer thyristors of M, C and Y recording heads having light-emitting thyristors not to be lit to perform transfer operations as the transfer thyristors of a K recording head having light-emitting thrystors to be lit, the difference in the amount of light among the recording heads is corrected.

Abstract: An optical print head and an image formation apparatus which can form a satisfactory image without shortening an exposure time in an image processing at high speed. A satisfactory image is formed at high speed by alternately radiating a first light emitting element array and a second light emitting element array under a predetermined driving condition depending on a relation between a distance d in a Y direction between elements perpendicular to an array direction X of light emitting elements and an image resolution pitch P by using the optical print head composed of two light emitting element arrays.

Abstract: Disclosed is an optical writing device comprising a plurality of writing light shutter elements and at least one of monitoring light shutter element. Both the writing and monitoring light shutter elements are driven by being alternatively impressed a forward electric field and a reverse electric field with a predetermined impression ratio of the forward and reverse electric fields during optical writing operation. After the optical writing operation, the monitoring light shutter element is driven by being impressed the forward electric field with varying the amount of the electric field, whereby a half-wavelength voltage of the monitoring light shutter element is determined. For the next optical writing operation, the impression ratio is updated based on the determined half-wavelength voltage.

Abstract: A recording head includes a recording element array including a plurality of linearly arranged recording elements, and a flexible wiring substrate for inputting a recording signal into the recording element array. A matrix-wiring for matrix-driving the plurality of recording elements is formed in the flexible wiring substrate.

Abstract: A light-emitting array and its driving circuitry are integrated into a single device. The driving circuitry is formed in a semiconductor substrate and has an array of output terminals on a surface of the substrate. Organic electroluminescent elements are formed directly over the output terminals, in electrical contact with the output terminals. The electroluminescent elements are driven by direct current. An optical head assembly has one or more of these light-emitting arrays mounted on a printed circuit board.

Abstract: An image forming apparatus wherein data which enters in parallel a plurality of pixels at a time is converted to a serial image data string. This serial image data string is shifted by a predetermined number of pixels, the shifted serial image data string is output in parallel a plurality of pixels at a time, and an image is formed based upon the image data output in parallel a plurality of pixels at a time.

Abstract: Bit data of a received video signal is partially converted into a first signal representing a data sequence corresponding to the resolution of an LED head. The first signal is transmitted to the LED head in the form of a real printing data signal that is to be printed on a basic raster line in synchronism with a line timing signal. The remaining bit data of the received video signal, which are not converted into the first signal, are converted into a second signal representing another data sequence, and then stored in a line buffer. The second signal stored in the line buffer is transmitted to the LED head in the form of a real printing data signal that is to be printed on an additional raster line in synchronism with an additional line timing signal. The LED head drive energy with which the basic raster lines are printed and another LED head drive energy with which the additional raster lines are printed are set independently of each other. The LED head may be provided with such a resolution function.

Abstract: A driving current is supplied via a current limiting resistor to a laser diode for emitting a red laser beam. This driving current is controlled so as to make the optical output of the laser diode have a predetermined reference value. Further, a current of a constant level is intermittently subtracted from the driving current flowing into the laser diode, on the basis of an image to be formed.

Abstract: Double clad fiber gain medium systems particularly adapted for marking indicia on surfaces of articles are disclosed. These systems provide a modulated output from a pump or seed semiconductor laser source to a double clad fiber gain medium which provides an amplified marking output scanned over the article surface with an optical scanner forming a plurality of strokes, the completion of which results in the indicia.

Abstract: A head controller 2 reads out adjustment data from a ROM 3 immediately after a power-on operation. The adjustment data is prepared for adjusting unevenness of light emission from LEDs in a LED head 5. A buffer memory 4 stores the read adjustment data. The head controller 2 reads the adjustment data from the buffer memory 4 with high data transfer rate, and obtains bitmap data from a frame memory or the like (not shown). The head controller 2 sends the read bitmap data and the adjustment data to an anode driver 51. The head controller 2 sends a strobe signal to the anode driver 51 and a cathode driver 53. The anode driver 51 adjusts ampere of supplied currents (i.e. drive signals corresponding to the bitmap data) from the head controller 2, in accordance with the received adjustment data in response to the reception of the strobe signal. The adjusted drive signals are sent to LED array chips 52.

Abstract: A print head includes a driving circuit having a cascaded series of driver integrated circuits mounted on a printed wiring board. Differential clock signals are supplied to the driver integrated circuits to synchronize the transfer of print data through the cascaded series. Even-numbered driver integrated circuits and odd-numbered driver integrated circuits are connected differently to the clock signal lines, but the even-numbered (or odd-numbered) driver integrated circuits generate an inverted internal clock signal, thereby compensating for the difference. This enables the clock signal lines to be mutually adjacent and to have a weaving layout that yields improved noise immunity.

Abstract: Compensation data for use in driving an array of printing elements in a printing head are obtained by measuring the uncompensated output value of each printing element, calculating a target value for each printing element, and determining a compensation value from the difference between the measured output value and the target value. The target values vary continuously across the array. The compensation data are stored in a non-volatile memory in the printing head. During printing, each printing element is driven with an energy corresponding to the compensation data, so that the output profile of the array follows the profile of target values.

Abstract: An image formation apparatus which records an image on a recording medium is provided. The apparatus has a recording element array head on which plural recording chips are arranged, plural recording elements being arrayed on the recording chip, a reference clock generation unit for generating a reference clock, a main scan sync signal generation unit for generating a main scan sync signal by dividing the reference clock into 2n1 (n1: positive number) parts, an input unit for raster inputting image data for one line in synchronism with the main scan sync signal, a drive clock generation unit for generating a drive clock by dividing the reference clock into 2n2 (n2: positive number) parts and a drive unit for driving the recording chips in synchronism with the drive clock.

Abstract: An image formation apparatus stably controls a drive current of a laser diode irrespective of change in density. In the apparatus, a current restriction circuit restricts a current ILD according to the output light quantity. If the current ILD increases and thus approaches to the value of a reference current IPO, the circuit outputs the current restricted to be the certain value substantially equal to the current IPO. Then, current buffers and, a current subtraction circuit, a switching circuit and a current addition circuit cooperatively supply the function current obtained from the input and output currents of the circuit to the cathode of the laser diode.

Abstract: A method and apparatus for a fault tolerant recording system using a pair of laser diode arrays is disclosed. Two monolithic laser diode arrays made of individually addressable diodes are used to record parallel tracks on a recording surface. A pair diodes, (one diode from each array) are assigned to each track, but only one diode (the primary diode) is activated. In the case where the primary diode fails, the secondary diode is activated. Digital delays are employed to synchronize the data from the two diode arrays in order to align the written marks on the recording surface.

Abstract: The timing control of optical beams (i.e., the control of the beam positions in the main scanning direction) and the beam amount control of the optical beams for position control (i.e., the control of the beam positions in the sub-scanning direction) are performed independently of the control of the amount of optical beam actually used for printing. Accordingly, the timing control of optical beams and the beam amount control of the optical beams for position control can be performed without reference to the characteristic change which the photosensitive drum may undergo with time. Even when the powers (second powers) of the optical beams incident on the photosensitive drum increase due to the characteristics change of the photosensitive drum or for some other reason, this power increase does not adversely affect the timing control of optical beams, nor does it vary the powers (first powers) of the optical beams which are incident on the optical beam sensor at the time of position control.