Abstract: An integrated circuit includes a light emitting device and a light emitting device driver coupled to the light emitting device. The light emitting device driver is for generating a drive signal to drive the light emitting device to emit light. A light emitting device driver includes a transistor having a first terminal coupled to a light emitting device; a resistor having a first terminal coupled to a second terminal of the transistor, and a second terminal coupled to a supply node; and a comparator having a first input terminal coupled to a reference voltage, a second input terminal coupled to the second terminal of the transistor, and an output terminal coupled to a control terminal of the transistor. The light emitting device driver controls an electrical current flowing through the transistor for driving the light emitting device to emit light.

Abstract: From a latch circuit (12) composed of five stages of latch circuits each storing data signals corresponding to one line, data signals to be fed to a drive circuit (16) to light the corresponding light-emitting sections are selected by a select circuit (15) selects according to correction data, consisting of 9 bits for each light-emitting section, stored in a Y position correction data storage circuit (13). This permits adjustment of the timing with which the individual light-emitting sections are lit and thereby helps achieve printing with satisfactory linearity.

Abstract: An image-forming apparatus is disclosed that includes at least one imaging optical system forming an electrostatic latent image on the scanning surface of a medium moving in a sub scanning direction by scanning the scanning surface in a main scanning direction by periodically deflecting a laser beam with a rotary deflector, a pixel clock generation part generating a pixel clock signal for controlling the emission timing of the laser beam and changing the phase of the pixel clock signal, a region setting part setting the length of each of multiple regions based on image writing magnifications in a line in the main scanning direction, the regions being formed by dividing part of the scanning surface corresponding to the line in the main scanning direction, and a phase control part controlling the changing of the phase of the pixel clock signal region by region based on the image writing magnifications.

Abstract: A data signal which is output from a latch circuit (12) having five stages of latch circuits each storing one-line data signal to a drive circuit (16) for lighting each light emission unit is selected by a selection circuit (15) according to a 9-bit correction data signal for each of the light emission units stored in a Y-position correction data storage circuit (13). Thus, lighting timing of each light emission unit is adjusted, thereby performing printing having a preferable linearity.

Abstract: When correction data is set, a CPU 3 reads out the correction data from an EEPROM 8 through strobe signal lines STB1-N to STB4-N and supplies it as print data signals DATA3 to DATA0 to an LED driver IC 6. When the driving of an LED array 7 according to print data is instructed, the CPU 3 supplies a group selection signal to the LED array 7 through the strobe signal lines STB1-N to STB4-N. An electrophotographic printer which can realize a high speed of the operation and contribute to the improvement of the reliability is provided.

Abstract: A print head comprises a plurality of light emitting devices which are arranged such that the adjacent light emitting devices are stepped from each other in the rotation direction of a photosensitive member, or a plurality of light emitting devices which are disposed linearly such that the light emitting devices emit light at different timings each other by employing a delay mechanism. Consequently, it is possible to provide the output pattern capable of directing the human eyes in two dimensions so as to reduce the visible difference in the image density.

Abstract: The invention relates to a method for operating an electrophotographic printing device (10). A multilevel character generator (22) is used in said printing device (10). Correction parameters (K1, K2, K3) are determined for light coding values (1, 2 and 3) such that a high-quality printed image can he obtained also in the instance of modified printing conditions.

Abstract: An electrophotographic device with a laser power correction device (and method therefor) includes a laser power detection sensor retractably disposed relative to a laser beam optical path of a laser beam, a laser power adjusting device for controlling laser power of the laser beam based on an output from the laser power detection sensor, and a controller for inserting the laser power detection sensor into the optical path and applying laser power correction when a total laser beam activation time has reached a predetermined time and printing is stopped.

Abstract: An 8-bit (256 gradient) image is represented using a driver IC of 6-bit (64 gradient) construction to drive a plurality of arrayed optical shutter elements. The image data are divided into 64 gradient sections, synchronized by shift clock signals, and transmitted in four cycles to the shift register. The optical shutter element is not turned OFF at the 64th pulse, but is continuously driven without transmitting to the comparator the standard clock signal of the 64th pulse, which controls the ON time of the optical shutter element. In this way, an image of a higher number of gradient levels can be represented using a driver IC of a low number of bits, thereby providing a solid state scanning type optical recording device which suppresses noise generation by reducing the load on the driver IC when driving at multi-level gradient.

Abstract: In a color reproducing system an image to be reproduced is analyzed to identify which color toner cartridges are required to print the image. Based on the identification, the color reproducing system selectively enables only those toner cartridges which are required to reproduce the image. In a host-based system the identification can be performed by a computer which provides the identification to a reproducing apparatus. In a controller-based system the identification is performed by a controller in the reproducing apparatus.

Abstract: An image forming device includes a plurality of holding units that holds data of pixels around a target pixel, a weight generating unit that generates a weight for each holding unit, a plurality of weight applying units that applies a corresponding weight to the data held by each holding unit, and a control unit that determines an exposing energy for the target pixel in accordance with an output of each weight applying unit.

Abstract: An image forming apparatus including a photoreceptor which includes an electroconductive substrate, a photosensitive layer including a charge generation material and a charge transport material and located overlying the electroconductive substrate, and a protective layer including an inorganic filler having an average particle diameter (d) and a binder resin; and an imagewise light irradiator configured to irradiate the photoreceptor with a laser light beam having a wavelength of (&lgr;) to form a light spot having a diameter (L) in the minor axis direction thereof on a surface of the photoreceptor, wherein the relationship 0.1<3.75×10−3L/&lgr;<d/&lgr;<0.5 is satisfied. An image forming method is also provided which includes irradiating a surface of the photoreceptor with a laser beam such that the above-mentioned relationship is satisfied.

Abstract: Provided is an image forming apparatus for forming a toner image including: a first light source emitting a beam corresponding to image information; a first photosensitive member; a first developing means for developing a latent image with a first toner; a second light source; a second photosensitive member; and a second developing means for developing a latent image with a second toner, in which the coloring agent contained in the first toner and the coloring agent contained in the second toner are substantially of the same hue, with the content of the coloring agent contained in the second toner being smaller than the content of the coloring agent contained in the first toner, and in which an oscillation wavelength of at least the first light source ranges from 370 to 500 nm. With the image forming apparatus structured as described above, an improvement in terms of granularity is achieved.

Abstract: The invention concerns a clock-generating circuit, which generates dot clock pulses for driving a light-emitting element employed in an optical-writing section of an image-forming apparatus and has a function of canceling f&thgr; property errors caused by a f&thgr; lens employed in the image-forming apparatus. The clock-generating circuit includes a digital-delay dot clock adjusting section to adjust timings of rising-edges or falling-edges of the dot clock pulses generated by changing a selection for a plurality of delayed-clock pulses, which are generated by delaying clock-pulses, outputted from a reference oscillator, in slightly different delay times; and a controlling section to control a selecting operation for the plurality of delayed clock pulses, performed in the digital-delay dot clock adjusting section, so as to compensate for f&thgr; property errors caused by the f&thgr; lens employed in the optical-writing section.

Abstract: A clock generating part generates a high-frequency clock signal having a frequency higher than that of a pixel clock frequency; a serial modulation signal generating part generates a serial modulation signal having a serial pulse sequence based on the high-frequency clock signal, and, light emission is modulated according to the serial modulation signal, and, thus, each pixel of an image is formed according at the pixel clock frequency.

Abstract: In a multibeam scanner, a control unit includes a velocity detecting circuit detecting a conveying velocity V of a photosensitive body; a comparison circuit comparing the detected conveying velocity V to a reference conveying velocity V0; a light intensity control circuit 93, a modulation circuit 94, an LD1 control circuit 95, and an LD2 control circuit 96. The LD1 control circuit 95 and LD2 control circuit 96 issue drive signals to laser diodes LD1 and LD2. The laser diodes LD1 and LD2 emit laser beams LB1 and LB2 that are modulated according to image signals outputted from the modulation circuit 94. The laser beams LB1 and LB2 are deflected by a polygon mirror onto the photosensitive body and perform a main scan over neighboring scanning lines SL1 and SL2, while the photosensitive drum is rotated. The light intensity from the laser diode LD1 is adjusted when the velocity of the photosensitive drum differs from a prescribed velocity in order to achieve a balanced image density.

Abstract: From a latch circuit (12) composed of five stages of latch circuits each storing data signals corresponding to one line, data signals to be fed to a drive circuit (16) to light the corresponding light-emitting sections are selected by a select circuit (15) selects according to correction data, consisting of 9 bits for each light-emitting section, stored in a Y position correction data storage circuit (13). This permits adjustment of the timing with which the individual light-emitting sections are lit and thereby helps achieve printing with satisfactory linearity.

Abstract: An optical scanning apparatus provides improved image quality by changing the amount of writing scale compensation for a pixel clock during a scanning cycle. A pixel clock generation unit of the optical scanning apparatus divides the scanning cycle into multiple division periods. A phase change of the pixel clock is carried out for each of the division periods. The phase change can also be different from scanning cycle to scanning cycle.

Abstract: A laser control device includes a light amount varying section for varying the light exposure amount at plural levels is provided with a correction section for correcting the difference between the times to the peaks of laser outputs of print signals input to a laser control circuit. The turning on time of each print signal is corrected, whereby the difference between the times to the peaks of laser outputs of the print signals different in light exposure amount can be eliminated for correcting the difference between image print positions.

Abstract: An image forming apparatus including a photoreceptor which includes an electroconductive substrate, a photosensitive layer including a charge generation material and a charge transport material and located overlying the electroconductive substrate, and a protective layer including an inorganic filler having an average particle diameter (d) and a binder resin; and an imagewise light irradiator configured to irradiate the photoreceptor with a laser light beam having a wavelength of (&lgr;) to form a light spot having a diameter (L) in the minor axis direction thereof on a surface of the photoreceptor, wherein the relationship 0.1<3.75×10−3L/&lgr;<d/&lgr;<0.5 is satisfied. An image forming method is also provided which includes irradiating a surface of the photoreceptor with a laser beam such that the above-mentioned relationship is satisfied.

Abstract: An image forming and apparatus is provided in which a halftone density of an image is stabilized irrespective of a timing at which writing on scanning lines is started, even when using multiple laser beams. First, it is determined whether or not a portion exposed by adjacent laser beams (i.e., exposed by both of two beams simultaneously) is present. If the result of the determination is affirmative, it is then determined whether or not a portion adjacent to the exposed portion and not exposed by a laser beam is present. If the result of this determination is affirmative, exposure by fine dots is added to the portion not exposed by a laser beam.

Abstract: An image forming apparatus having a photosensitive member, an exposure device having a laser emitting element that irradiates a laser beam, the laser beam being scanned on the photosensitive member line by line to form an electrostatic latent image on the photosensitive member, a developing device that supplies a developing agent to the electrostatic latent image to form a visible image, and a controller that controls the laser emitting element to irradiate the laser beam in a predetermined light amount. The controller further controls the laser emitting element to irradiate the laser beam in a reduced light amount every at least one line.

Abstract: A dot-matrix image-forming device such as an electrophotographic printer alters the size of a dot according to the surrounding dot pattern, thereby compensating for the tendency of isolated dots or small groups of dots to be undersized due to characteristics of the image formation process. Alternatively, the device may add dots to or delete dots from a contiguous group of dots to achieve substantially the same effect. Preferably, the device both adds or deletes dots and alters the dot size. This compensation scheme enables the total area occupied by dots in a given image region to be proportional to the number of dots in the region, regardless of the dot density and arrangement in the region.

Abstract: An electrophotographic device with a laser power correction device (and method therefor) includes a laser power detection sensor retractably disposed relative to a laser beam optical path of a laser beam, a laser power adjusting device for controlling laser power of the laser beam based on an output from the laser power detection sensor, and a controller for inserting the laser power detection sensor into the optical path and applying laser power correction when a total laser beam activation time has reached a predetermined time and printing is stopped.

Abstract: When a halftone image region that is below a predetermined density is to be reproduced, a processing unit controlling an exposure unit selects an exposure pattern that can represent a record dot diameter within a range based on a predetermined rule from exposure patterns prepared in advance. Accordingly, graininess is suppressed. When there are a plurality of exposure patterns that can be applied, the exposure pattern with the lowest number of dots present per 1 inch is employed. Accordingly, a halftone image is formed with the image reproducibility improved.

Abstract: An image forming apparatus which includes an image bearing body and a light beam scanner for exposing the image bearing body, which is charged, based on an image signal and forming an electrostatic latent image on the image bearing body. A rise time or a fall time of a light beam emitted from the light beam scanner is controlled when a pixel density of the electrostatic latent image is switched.

Abstract: An image forming apparatus includes an image bearing member for bearing a latent image and a charger for charging the image bearing member. The charged image bearing member is exposed to form the latent image and a developing unit develops the latent image. One of an exposure amount reduction mode for executing image formation by reducing an exposure amount and a normal mode for executing image formation with a normal exposure amount is selected. A correction amount of a look-up table for gradational correction is changed when the exposure amount reduction mode is selected.

Abstract: A driving means 6 is placed below a photoconductor drum 2. The driving means 6 includes first to fourth developing rollers 13A-13D and toner storage chambers 11A-11D. The developing means 6 can be shifted by a developing-device moving motor 9 to bring one of the developing rollers 13A-13D which corresponds to one of liquid toners 12A-12D to be developed in close to the photoconductor drum 2, followed by developing a latent image formed by an exposure. At this time, the distance between one of the developing rollers 13A-13D and the photoconductor drum 2 can be appropriately adjusted. In addition, before the development, meniscus of the liquid toner is quickly formed between the developing rollers 13A-13D and the photoconductor drum 2 by rotating the development rollers 13A-13 at the rotation speed higher than the rotation speed thereof at the development.

Abstract: In an electrophotographic apparatus, regions having at least three different potential levels Vc, Vw, and Vr are formed on a photosensitive member by using an exposing device, and developing processes respectively using colored particles of different kinds are performed by normal development and reversal development on two potential levels Vc and Vr excluding the intermediate potential level Vw. The apparatus has an auxiliary exposing unit for forming a fringe development preventing potential in an edge of an image forming region in order to prevent fringe development from occurring. The auxiliary exposing unit sets an auxiliary exposure amount by performing pulse-width modulation on a laser driver.

Abstract: An electrophotographic apparatus is provided having an electrophotographic photosensitive member and an exposure device for forming a static latent image on the electrophotographic photosensitive member surface by scanning with an exposure beam based on an image information. The spot diameter of the exposure beam is 2.5 times or more the size of one pixel of an image picture formed by the electrophotographic apparatus. The electrophotographic photosensitive member has the Fischer hardness of 240 Ns/mm2 or more in its surface, and the NESA sensitivity of 2000 V·cm2/&mgr;J or more, and is provided with an electric charge generating layer and an electric charge transportation layer 30 &mgr;m or less thick.

Abstract: An object of the present invention is to provide an electrophotographic apparatus that has a photosensitive body, a charging member, provided to be capable of contacting with the photosensitive body, for charging the photosensitive body, an oscillating voltage being applied to the charging member, and exposing device for exposing the photosensitive body charged by the charging member, by an exposure beam based on image information to form an electrostatic image, wherein when a spot ratio which is a ratio of a spot diameter of the exposure beam to a size of one pixel of the electrostatic image is represented by &agr;, a pixel density of the electrostatic image is represented by R (dot/mm), a process speed of the photosensitive body is represented by V (mm/sec), a frequency of the oscillating voltage is represented by f (Hz) and a NESA sensitivity of the photosensitive body is represented by &ggr;(V·cm2/&mgr;m), 2.5≦&agr;, 4.2≦R×V/f≦7.0, and 2,000≦&ggr; are satisfied.

Abstract: A laser control device includes a light amount varying section for varying the light exposure amount at plural levels is provided with a correction section for correcting the difference between the times to the peaks of laser outputs of print signals input to a laser control circuit. The turning on time of each print signal is corrected, whereby the difference between the times to the peaks of laser outputs of the print signals different in light exposure amount can be eliminated for correcting the difference between image print positions.

Abstract: An image forming apparatus compensating for printing density of a toner image by adjusting a quantity of image light to form the toner image in accordance with a variation of a resistance of a roller includes an electrical charge roller electrically charging a photosensitive drum, a laser scan unit projecting the image light on the photosensitive drum to form an electrostatic latent image corresponding to an input image, a development roller developing the electrostatic latent image formed on the photosensitive drum with toner to form the toner image, a transfer roller rotating in contact with the photosensitive drum and transferring the toner image to a sheet of printing paper when a predetermined voltage is supplied to the transfer roller, and a controller controlling the laser scan unit and varying the quantity of the image light projected from the laser scan unit in accordance with the variation of a resistance value of the transfer roller.

Abstract: An image forming apparatus which includes a light source for emitting a light beam modulated according to an image signal and an optical deflector for repeatedly deflecting the light beam. A focussing optical system focuses the light beam deflected by the optical deflector on a surface to be scanned to form a light spot there, the surface being scanned repeatedly in a main-scanning direction. A photosensitive member is arranged at the surface and exposed selectively to the light spot, the photosensitive member having an image forming region and blank regions arranged at opposite ends of the image forming region. A developing unit causes toner to adhere to unexposed areas of the selectively exposed photosensitive member and develops an image. A photodetector receives part of the light beam emitted from the light source and an automatic power control circuit controls an output power of the light source on the basis of an output of the photodetector.

Abstract: An image-forming apparatus for forming an image by electrically charging a photosensitive material, forming an electrostatic image through the exposure to light and developing the electrostatic image, wherein the main charged potential, Vo, of the photosensitive material, the potential, Vr, of the exposed portion of the photosensitive material and the developing bias potential DB are so set as to satisfy the following formulas, V1≦|DB−Vr|≦V2  (1) V3≦|Vo−DB|≦300  (2). V1, V2 and V3 are parameters calculated from a developing characteristics curve obtained by plotting the image densities to a potential difference between the developing bias potential and the surface potential, 0 V, of the photosensitive material when the image is formed by changing the developing bias potential with the exposure amount being zero in a state where the potential on the surface of the photosensitive material is maintained at zero.

Abstract: An image forming apparatus includes a photosensitive member, an exposure device for exposing the photosensitive member which has been charged, a storing device storing therein a characteristic table two-dimensionally representing the potential decay characteristic of the surface of the photosensitive member, and a control device for controlling the exposure device on the basis of the characteristic table stored in the storing device.

Abstract: The invention concerns a clock-generating circuit, which generates dot clock pulses for driving a light-emitting element employed in an optical-writing section of an image-forming apparatus and has a function of canceling f&thgr; property errors caused by a f&thgr; lens employed in the image-forming apparatus. The clock-generating circuit includes a digital-delay dot clock adjusting section to adjust timings of rising-edges or falling-edges of the dot clock pulses generated by changing a selection for a plurality of delayed-clock pulses, which are generated by delaying clock-pulses, outputted from a reference oscillator, in slightly different delay times; and a controlling section to control a selecting operation for the plurality of delayed clock pulses, performed in the digital-delay dot clock adjusting section, so as to compensate for f&thgr; property errors caused by the f&thgr; lens employed in the optical-writing section.

Abstract: A clock generating part generates a high-frequency clock signal having a frequency higher than that of a pixel clock frequency; a serial modulation signal generating part generates a serial modulation signal having a serial pulse sequence based on the high-frequency clock signal, and, light emission is modulated according to the serial modulation signal, and, thus, each pixel of an image is formed according at the pixel clock frequency.

Abstract: A method in which a multilevel character generator (22) is adjusted using a single correction factor (KF) during an automatic compensation operation such that high-quality printed images can be obtained also in the instance of modified printing conditions.

Abstract: An exposure apparatus for image formation uses power control means provided to a laser driver for controlling exposure energy and accordingly forming an image. Specifically, exposure energy is varied depending on an isolated-dot pattern and an isolated-line pattern by changing the pulse height (drive power) of a drive pulse for each dot. Both of the isolated-line and isolated-dot patterns of a high resolution can thus be reproduced with a high image quality without increase of cost due to requirements for accuracy in processing and positioning of a lens and without decrease of life of a photoreceptor due to a decreased thickness of its photosensitive layer.

Abstract: In an electrophotographic device, a method is provided in which laser power is regulated at predetermined two points of gradation. More specifically, a first laser power regulating means which regulates the magnitude of laser power output and a second laser power regulating means which regulates the slope of laser power gradation characteristic are introduced. Thereby, stabilization of the laser power output value is realized at any stages of the gradation and an electrophotographic device can be provided which reduces variability in image quality between electrophotographic devices.

Abstract: A control unit of an image forming apparatus for controlling exposure energy includes a reference image storage unit storing a plurality of reference images, an image recognition unit comparing image information consisting of a plurality of pieces of pixel information with data stored in the reference image storage unit, an exposure energy density storage unit storing an exposure energy density for each reference image stored in the reference image storage unit, an exposure energy density determination unit based on data from the image recognition unit and data in the exposure energy density storage unit an exposure energy density to be applied to a dot position corresponding to each piece of the pixel information, and a laser drive driving a laser of an exposure unit based on data from the exposure energy density determination uni. Accordingly, the image forming apparatus can be provided which exhibits an excellent image reproducibility for images with various dot densities.

Abstract: The formation of a high-quality image at a resolution at which a dot size is smaller than the diameter of a laser beam is attained at a low cost. When an exposure operation is carried out by increasing an optical intensity of a laser beam to a level higher than that of a steady-state optical intensity thereof by utilizing a difference, which is ascribed to an exposure rate of a photosensitive body, in the condition of a latent image formed, the depth and width of a latent image, which were small in all related art cases, can be increased to high levels. Therefore, overshoot is generated at the LD lighting starting time to increase the optical intensity at a rising edge of the laser beam to a level higher than that of a steady-state optical intensity thereof, whereby a height to width ratio and the reproducibility of one dot and a halftone in a case where the resolution is smaller than the diameter of the laser beam can be improved.

Abstract: The invention provides an image forming apparatus which, in case of switching to an exposure amount reduction mode for executing the image formation with an exposure amount reduced from that in the normal image formation in order to prevent ghost image generation resulting from the exposure memory effect of the photosensitive member, corrects a look-up table for gradational correction for the intermediate density or is provided with a look-up table for the exposure amount reduction mode.

Abstract: An object of the present invention is to provide an image forming apparatus that has an image bearing body, exposing device for exposing the image bearing body, which is charged, based on an image signal and forming an electrostatic latent image on the image bearing body, wherein a pixel density of the electrostatic latent image can be switched, and control device for controlling a responsibility to the image signal of the exposing device when the pixel density is switched.

Abstract: An object of the present invention is to provide an electrophotographic apparatus that has a photosensitive body, a charging member, provided to be capable of contacting with the photosensitive body, for charging the photosensitive body, an oscillating voltage being applied to the charging member, and exposing device for exposing the photosensitive body charged by the charging member, by an exposure beam based on image information to form an electrostatic image, wherein when a spot ratio which is a ratio of a spot diameter of the exposure beam to a size of one pixel of the electrostatic image is represented by &agr;, a pixel density of the electrostatic image is represented by R (dot/mm), a process speed of the photosensitive body is represented by V (mm/sec), a frequency of the oscillating voltage is represented by f (Hz) and a NESA sensitivity of the photosensitive body is represented by &ggr; (V·cm2/&mgr;m), 2.5≦&agr;, 4.2≦R×V/f≦7.0, and 2,000≦&ggr; are satisfied.

Abstract: An image forming apparatus includes a photosensitive member, an exposure device for exposing the photosensitive member which has been charged, a storing device storing therein a characteristic table two-dimensionally representing the potential decay characteristic of the surface of the photosensitive member, and a control device for controlling the exposure device on the basis of the characteristic table stored in the storing device.

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 image processing apparatus capable of color image formation with a plurality of color components, which solves a problem of increment of processing time in monochrome image formation due to correction on image formation conditions with predetermined patch formation. For this purpose, in case of monochrome image formation, even if a tonality control request flag is set, an image formation sequence is started without performing tonality control. Thus processing time can be reduced in monochrome image formation.

Abstract: An exposure apparatus for image formation uses power control means provided to a laser driver for controlling exposure energy and accordingly forming an image. Specifically, exposure energy is varied depending on an isolated-dot pattern and an isolated-line pattern by changing the pulse height (drive power) of a drive pulse for each dot. Both of the isolated-line and isolated-dot patterns of a high resolution can thus be reproduced with a high image quality without increase of cost due to requirements for accuracy in processing and positioning of a lens and without decrease of life of a photoreceptor due to a decreased thickness of its photosensitive layer.