JP2011070151A - Hologram recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a hologram recording device that eliminates the need for precise alignment of a light emitting element when hologram is recorded on a recording layer formed on a substrate on which a plurality of light emitting elements are arranged one-dimensionally or two-dimensionally. <P>SOLUTION: A plurality of holograms are recorded on a hologram recording layer formed on the substrate on which the plurality of light emitting elements are arranged one-dimensionally or two-dimensionally by making a first lightwave and a second lightwave interfere with each other so that the condensing points are arranged in a predetermined arrangement direction at a fixed interval. Prior to recording the holograms, while at least one of the plurality of light emitting elements is turned on, the position of the turned-on light emitting element is measured, and a recording condition required for recording the holograms is acquired based on the measured position. Then, position adjustment of a recording optical system is performed based on the acquired recording condition, the first lightwave and the second lightwave are radiated to the hologram recording layer, and the plurality of holograms are sequentially recorded. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a hologram recording apparatus.

  Patent Document 1 discloses an optical information recording apparatus for recording information on an optical information recording medium having an information recording layer on which information is recorded using holography, and includes information light carrying information. Information light generating means for generating, phase modulation means for spatially modulating the phase of the light, and recording reference light generating means for generating recording reference light whose phase is spatially modulated by the phase modulating means; The information light generated by the information light generating means and the recording reference light generating means are recorded so that information is recorded on the information recording layer by an interference pattern due to interference between the information light and the recording reference light. An optical information recording apparatus comprising a recording optical system for irradiating the information recording layer with the recording reference light from the same surface side is described.

  In addition, in Patent Document 1, as the optical information recording medium, a medium having a positioning area in which information for positioning the reproduction reference light is recorded, and further, information recorded in the positioning area is used. An optical information reproducing apparatus comprising position control means for controlling the position of the reproduction reference light with respect to the optical information recording medium is described.

JP-A-11-311937

  An object of the present invention is to record a hologram on a recording layer formed on a substrate in which a plurality of light emitting elements are arranged one-dimensionally or two-dimensionally, and does not require precise alignment of the light-emitting elements. It is to provide a recording apparatus.

  In order to achieve the above object, the invention described in each claim has the following configuration.

  According to the first aspect of the present invention, a hologram recording layer is formed on a hologram recording layer formed on a substrate in which a plurality of light emitting elements are arranged one-dimensionally or two-dimensionally from a position corresponding to the plurality of light emitting elements. A first light irradiating means for irradiating a first light wave passing through an optical path of the diffused light passing therethrough, and passing through the optical path of the convergent light converging on the hologram recording layer outside the optical path of the first light wave; A second light irradiating means for irradiating a second light wave for recording a hologram by interference with one light wave; and at least one of the plurality of light emitting elements is lit before recording the hologram on the hologram recording layer. Measuring means for measuring the position of the light-emitting element that has been lit, and the light emitted from each of the plurality of light-emitting elements converge so that a plurality of condensing points are arranged at predetermined intervals in a predetermined arrangement direction And the measuring means Based on the position of the light emitting element and the position of the corresponding condensing point, the plurality of light sources emitted from the light emitting element based on the measured position of the light emitting element are converged to the corresponding condensing point. Recording conditions including at least the irradiation angle, diffusion or convergence angle, and irradiation position of the first light wave and the second light wave necessary for recording each of the plurality of holograms corresponding to each of the light emitting elements Based on the acquisition means to be acquired and the recording conditions acquired by the acquisition means, the first light irradiation means, the second light irradiation means and the position of the substrate are adjusted, and the first light wave and the A hologram recording apparatus comprising: a recording unit configured to irradiate the hologram recording layer with a second light wave and sequentially record each of the plurality of holograms corresponding to each of the plurality of light emitting elements on the hologram recording layer. A.

  The invention according to claim 2 is the hologram recording apparatus according to claim 1, further comprising storage means for storing the position of the light emitting element measured by the measurement means.

  According to a third aspect of the present invention, the recording unit adjusts a position of the first light irradiation unit that irradiates the first light wave to the substrate on which the hologram recording layer is formed. Based on the adjustment means, the drive means for driving each of the plurality of light emitting elements to be turned on or off, and the recording condition acquired by the acquisition means, the first light irradiation means, the second light A plurality of holograms corresponding to each of the plurality of light emitting elements on the hologram recording layer by adjusting the positions of the irradiation means and the substrate, irradiating the hologram recording layer with the first light wave and the second light wave The hologram recording apparatus according to claim 1, further comprising: a first control unit that controls the first position adjusting unit and the driving unit so as to sequentially record each of the first and second position adjusting units.

  According to a fourth aspect of the present invention, the recording means transmits the position of the substrate on which the hologram recording layer is formed and the second light wave to the first light irradiation means that irradiates the first light wave. Second position adjusting means for adjusting the position of the second light irradiating means for irradiating, driving means for driving each of the plurality of light emitting elements to be turned on or off, and the recording acquired by the acquiring means Based on conditions, adjust the position of the first light irradiation means, the second light irradiation means and the substrate, irradiate the hologram recording layer with the first light wave and the second light wave, And a second control means for controlling the second position adjusting means and the driving means so as to sequentially record each of the plurality of holograms corresponding to each of the plurality of light emitting elements on the hologram recording layer. The holo according to claim 1 or 2 A lamb recording device.

  According to the invention described in each claim of the present invention, the following effects are obtained.

  According to the first aspect of the present invention, when a hologram is recorded on a recording layer formed on a substrate in which a plurality of light emitting elements are arranged one-dimensionally or two-dimensionally, precise alignment of the light-emitting elements is performed. Is no longer necessary.

  According to the second aspect of the present invention, since the hologram is recorded based on the stored position of the light emitting element, the production time is shortened as compared with the case where the storage means is not provided.

  According to the third aspect of the present invention, the position of the first light irradiating means for irradiating the first light wave (reference light) is adjusted, and the condensing point is determined in advance regardless of the arrangement of the plurality of light emitting elements. Holograms can be recorded so that they are arranged in the arrangement direction.

  According to the fourth aspect of the present invention, the position of the second light irradiating means for irradiating the second light wave (signal light) together with the substrate is adjusted regardless of the arrangement of the plurality of light emitting elements, and the plurality of light emitting elements Regardless of the arrangement, the hologram can be recorded so that the focal points are arranged in a predetermined arrangement direction.

1 is a schematic diagram illustrating an example of a configuration of an image forming apparatus according to an embodiment of the present invention. It is a schematic perspective view which shows an example of a structure of the LED print head which concerns on embodiment of this invention. (A) is a perspective view showing a schematic shape of a hologram element, (B) is a sectional view in the sub-scanning direction of the LED print head, and (C) is a sectional view in the main scanning direction of the LED print head. (A) And (B) is a figure which shows a mode that a hologram element is formed. (A) is a top view which shows the arrangement | sequence of a SLED chip partially, (B) is a top view explaining the malfunction of the arrangement | sequence of a SLED chip. It is the schematic which shows the shift | offset | difference of the imaging position at the time of fixedly arrange | positioning the recording optical system which records a hologram. (A) And (B) is explanatory drawing for demonstrating the method of obtaining a spot row | line | column corresponding to LED spaced apart in the subscanning direction. (A)-(E) is process drawing which shows the manufacturing process of an LED print head. It is the schematic which shows an example of a structure of the hologram recording apparatus which concerns on embodiment of this invention. It is a block diagram which shows the structure of the drive control system of a hologram recording device. It is a flowchart which shows the processing routine of a hologram recording program. (A) And (B) is a figure which shows the procedure which performs measurement and recording one by one for every SLED chip | tip arranged in zigzag form. (A) And (B) is a figure which shows the example which moves the optical system which irradiates a reference light according to the position of LED. It is the schematic which shows the partial structure of the modification of the hologram recording apparatus shown in FIG. (A) And (B) is a figure which shows the example which moves the LED print head and the optical system which irradiates signal light according to the position of LED.

  Hereinafter, an example of an embodiment of the present invention will be described in detail with reference to the drawings.

<Image forming apparatus>
FIG. 1 is a schematic diagram showing an example of the configuration of an image forming apparatus according to an embodiment of the present invention. This apparatus is an image forming apparatus that forms an image by an electrophotographic method, and is equipped with an LED type exposure device (LED print head, abbreviated as “LPH”) using a light emitting diode (LED) as a light source. LED printheads have the advantage that no mechanical drive is required. The image forming apparatus is a so-called tandem digital color printer. The image forming process unit 10 as an image forming unit that forms an image corresponding to image data of each color, and a control for controlling the operation of the image forming apparatus. And an image processing unit 40 that is connected to the image reading device 3 and an external device such as a personal computer (PC) 2 and performs predetermined image processing on image data received from these devices. Yes.

  The image forming process unit 10 includes four image forming units 11Y, 11M, 11C, and 11K that are arranged in parallel at regular intervals. Each of the image forming units 11Y, 11M, 11C, and 11K forms yellow (Y), magenta (M), cyan (C), and black (K) toner images. The image forming units 11Y, 11M, 11C, and 11K are collectively referred to as “image forming unit 11” as appropriate.

  Each image forming unit 11 includes a photosensitive drum 12 as an image carrier that forms an electrostatic latent image and carries a toner image, a charger 13 that uniformly charges the surface of the photosensitive drum 12 at a predetermined potential, An LED print head (LPH) 14 as an exposure device for exposing the photosensitive drum 12 charged by the developing device 13, a developing device 15 for developing the electrostatic latent image obtained by the LPH 14, and the surface of the photosensitive drum 12 after transfer. A cleaner 16 for cleaning is provided.

  Conventional LPH is composed of an LED array and a rod lens array. A refractive index distribution type rod lens such as SELFOC (registered trademark) has been used for the rod lens array. The light emitted from each LED is collected by a rod lens, and an erecting equal-magnification image is formed on the photosensitive drum. The image forming apparatus according to the present embodiment includes an LPH including a “hologram element array” instead of the “rod lens array”.

  The LPH 14 is a long print head having substantially the same length as the length of the photosensitive drum 12 in the axial direction. In the LPH 14, a plurality of LEDs are arranged in an array (row shape) along the length direction. The LPH 14 is disposed around the photosensitive drum 12 so that the length direction thereof faces the axial direction of the photosensitive drum 12. In LPH using a rod lens, the optical path length (working distance) from the lens array end face to the image formation point is as short as several millimeters, and the occupation ratio of the exposure device around the photosensitive drum is increased. On the other hand, the LPH 14 of the present embodiment has a long working distance of about several centimeters and is arranged several centimeters away from the surface of the photosensitive drum 12. For this reason, the occupation width in the circumferential direction of the photosensitive drum 12 is small, and congestion around the photosensitive drum 12 is reduced.

  The image forming process unit 10 also intermediate-transfers each color toner image of each image forming unit 11 and the intermediate transfer belt 21 onto which the toner images of each color formed on the photosensitive drum 12 of each image forming unit 11 are transferred in a multiple manner. A primary transfer roll 22 that sequentially transfers (primary transfer) to the belt 21; a secondary transfer roll 23 that collectively transfers (secondary transfer) the superimposed toner image transferred onto the intermediate transfer belt 21 to a sheet P that is a recording medium; and A fixing device 25 for fixing the secondary transferred image on the paper P is provided.

Next, the operation of the image forming apparatus will be described.
First, the image forming process unit 10 performs an image forming operation based on a control signal such as a synchronization signal supplied from the control unit 30. At that time, the image data input from the image reading device 3 or the PC 2 is subjected to image processing by the image processing unit 40 and supplied to each image forming unit 11 via the interface.

  For example, in the yellow image forming unit 11Y, the surface of the photosensitive drum 12 uniformly charged at a predetermined potential by the charger 13 is exposed by the LPH 14 that emits light based on the image data obtained from the image processing unit 40. Thus, an electrostatic latent image is formed on the photosensitive drum 12. That is, each LED of the LPH 14 emits light based on the image data, so that the surface of the photoconductive drum 12 is main-scanned, and the photoconductive drum 12 is rotated and sub-scanned, so An electrostatic latent image is formed. The formed electrostatic latent image is developed by the developing device 15, and a yellow toner image is formed on the photosensitive drum 12. Similarly, magenta, cyan, and black toner images are formed in the image forming units 11M, 11C, and 11K.

  Each color toner image formed by each image forming unit 11 is sequentially electrostatically attracted and transferred by the primary transfer roll 22 onto the intermediate transfer belt 21 rotating in the direction of arrow A in FIG. 1 (primary transfer). A superimposed toner image is formed on the intermediate transfer belt 21. The superimposed toner image is conveyed to a region (secondary transfer portion) where the secondary transfer roll 23 is disposed as the intermediate transfer belt 21 moves. When the superimposed toner image is conveyed to the secondary transfer unit, the paper P is supplied to the secondary transfer unit in accordance with the timing at which the toner image is conveyed to the secondary transfer unit.

  The superimposed toner images are collectively electrostatically transferred onto the conveyed paper P (secondary transfer) by the transfer electric field formed by the secondary transfer roll 23 in the secondary transfer portion. The sheet P on which the superimposed toner image has been electrostatically transferred is peeled off from the intermediate transfer belt 21 and conveyed to the fixing device 25 by the conveyance belt 24. The unfixed toner image on the paper P conveyed to the fixing device 25 is fixed on the paper P by being subjected to a fixing process by heat and pressure by the fixing device 25. The paper P on which the fixed image is formed is discharged to a paper discharge tray (not shown) provided in the discharge unit of the image forming apparatus.

<LED print head (LPH)>
FIG. 2 is a schematic perspective view showing an example of the configuration of an LED print head as an exposure apparatus according to the present embodiment. As shown in FIG. 2, the LED print head (LPH 14) includes an LED array 52 having a plurality of LEDs 50 and a hologram element array 56 having a plurality of hologram elements 54 provided corresponding to each of the plurality of LEDs 50. And. In the example illustrated in FIG. 2, the LED array 52 includes six LEDs 50 ₁ to 50 ₆ , and the hologram element array 56 includes six hologram elements 54 _{1 to} 54 ₆ . In addition, when it is not necessary to distinguish each from each other, the LEDs 50 ₁ to 50 ₆ are collectively referred to as “LED 50”, and the hologram elements 54 _{1 to} 54 ₆ are collectively referred to as “hologram element 54”.

  Each of the plurality of LEDs 50 is arranged on the LED chip 53. The LED chip 53 in which a plurality of LEDs 50 are arranged is mounted on a long LED substrate 58 together with a drive circuit (not shown) that drives each of the LEDs 50. The LED chip 53 is positioned on the LED substrate 58 so that the plurality of LEDs 50 are aligned in the main scanning direction. Accordingly, the LEDs 50 are arranged along a direction parallel to the axial direction of the photosensitive drum 12.

  The arrangement direction of the LEDs 50 is the “main scanning direction”. Further, each of the LEDs 50 is arranged so that the interval (light emission point pitch) in the main scanning direction between two adjacent LEDs 50 (light emission points) is a constant interval. Although the sub-scan is performed by the rotation of the photosensitive drum 12, the direction orthogonal to the “main scanning direction” is illustrated as the “sub-scanning direction”.

  As the LED array 52, various types of LED arrays such as an LED array in which a plurality of LEDs are mounted on a substrate in units of chips may be used. When arranging a plurality of LED chips on which a plurality of LEDs are arranged, the plurality of LED chips may be arranged in series or in a staggered manner. Two or more may be arranged in the sub-scanning direction. In FIG. 2, the LED array 52 in which a plurality of LEDs 50 are arranged in a one-dimensional manner on one LED chip 53 is only schematically shown.

  As will be described later, in the present embodiment, a plurality of LED chips 53 are arranged in a staggered pattern in the LED array 52 (see FIG. 5 and the like). That is, the plurality of LED chips 53 are arranged in a line so as to be arranged in the main scanning direction, and are arranged in two lines with a certain interval shifted in the sub-scanning direction. Even if divided into the plurality of LED chips 53, each of the plurality of LEDs 50 is arranged at a constant interval.

A hologram recording layer 60 is formed on the LED substrate 58 so as to cover the LED chip 53. The hologram element array 56 is formed in a hologram recording layer 60 formed on the LED substrate 58. That is, on the hologram recording layer 60, a plurality of hologram elements LEDs 54 _{1 to} 54 ₆ are formed along the main scanning direction corresponding to each of the plurality of LEDs 50 ₁ to 50 ₆ . Each of the hologram elements 54 has an interval in the main scanning direction of the LED 50 described above so that an interval in the main scanning direction of a spot 62 to be described later is constant. Are arranged so as to have substantially the same interval.

  In FIG. 2, for simplification, a plurality of hologram elements 54 are illustrated so as not to overlap each other, but as described later, in the present embodiment, two adjacent hologram elements 54 overlap each other. A hologram element 54 having a large diameter is formed. Further, in FIG. 2, the plurality of hologram elements 54 are illustrated in a simplified manner so as to have the same shape. However, as will be described later, two adjacent hologram elements 54 may have different shapes.

  The hologram recording layer 60 is made of a polymer material capable of permanently recording and holding a hologram. As such a polymer material, a so-called photopolymer may be used. The photopolymer records a hologram by utilizing a refractive index change caused by polymerization of a photopolymerizable monomer. As will be described later, the LED substrate 58 and the hologram recording layer 60 do not need to be in close contact with each other, and may be separated by a predetermined distance via an air layer, a transparent resin layer, or the like. For example, the hologram recording layer 60 may be held by a holding member (not shown) at a position separated from the LED substrate 58 by a predetermined height.

When the LED 50 emits light, the light emitted from the LED 50 (incoherent light) passes through an optical path of diffused light that spreads from the light emitting point to the hologram diameter. Due to the light emission of the LED 50, the situation is almost the same as when the hologram element 54 is irradiated with the reference light. As shown in FIG. 2, in the LPH 14 including the LED array 52 and the hologram element array 56, each light emitted from each of the _six LEDs 50 ₁ to 50 ₆ is transmitted from the corresponding hologram elements 54 _{1 to} 54 ₆ . Incident on either. The hologram elements 54 _{1 to} 54 ₆ diffract the incident light to generate diffracted light. Each diffracted light generated by each of the hologram elements 54 _{1 to} 54 ₆ is emitted in a direction in which the optical axis forms an angle θ with the emission optical axis, avoiding the optical path of the diffused light, and in the direction of the photosensitive drum 12. Focused.

Each of the emitted diffracted lights converges in the direction of the photosensitive drum 12 and forms an image on the surface of the photosensitive drum 12 disposed on the focal plane several cm ahead. That is, each of the plurality of hologram elements 54 functions as an optical member that diffracts and collects light emitted from the corresponding LED 50 and forms an image on the surface of the photosensitive drum 12. On the surface of the photosensitive drum 12, minute spots 62 _{1 to} 62 ₆ due to the diffracted lights are formed so as to be arranged in a line in the main scanning direction. In other words, the photosensitive drum 12 is main-scanned by the LPH 14. In addition, when it is not necessary to distinguish each, the spots 62 _{1 to} 62 ₆ are collectively referred to as “spots 62”.

  In general, in LPH using an LED that emits incoherent light (incoherent light), coherence decreases and spot blurring (so-called chromatic aberration) occurs, and it is not easy to form a minute spot. On the other hand, the LPH 14 of the present embodiment has high incident angle selectivity and wavelength selectivity of the hologram element, and high diffraction efficiency can be obtained. For this reason, background noise (background noise) is reduced, signal light is accurately reproduced, and a fine spot 62 (condensing point) with a clear outline is formed.

<Shape of hologram element>
3A is a perspective view showing a schematic shape of the hologram element, FIG. 3B is a sectional view of the LED print head in the sub-scanning direction, and FIG. 3C is a main scanning direction of the LED print head. FIG.

As shown in FIG. 3A, each of the hologram elements 54 is a volume hologram generally called a thick hologram element. Further, as shown in FIGS. 3A and 3B, each of the hologram elements 54 is formed in a truncated cone shape having the surface side of the hologram recording layer 60 as a bottom surface and converging toward the LED 50 side. Yes. In this example, a truncated cone-shaped hologram element will be described, but the shape of the hologram element is not limited to this. For example, it is good also as shapes, such as a cone, an elliptical cone, and an elliptical truncated cone. The diameter of the truncated cone-shaped hologram element 54 is largest at the bottom surface. The diameter of this circular bottom is defined as “hologram diameter r _H ”.

Each of the hologram elements 54 has a “hologram diameter r _H ” that is larger than the interval of the LEDs 50 in the main scanning direction. For example, the interval in the main scanning direction of the LED 50 is 30 μm, the hologram diameter r _H is 2 mm, and the hologram thickness h _H is 250 μm. Therefore, as shown in FIGS. 2 and 3C, the two hologram elements 54 adjacent to each other are formed so as to greatly overlap each other. The plurality of hologram elements 54 are multiplexed and recorded by, for example, spherical wave shift multiplexing.

  Each of the plurality of LEDs 50 is arranged on the LED substrate 58 with the light emitting surface facing the surface side of the hologram recording layer 60 so as to emit light toward the corresponding hologram element 54 side. The “light emitting optical axis” of the LED 50 passes through the vicinity of the center of the corresponding hologram element 54 (for example, the axis of symmetry of the truncated cone) and faces the direction orthogonal to the LED substrate 58. As shown in the figure, the light emission optical axis is orthogonal to each of the main scanning direction and the sub-scanning direction.

  Although not shown, the LPH 14 is held by a holding member such as a housing or a holder so that the diffracted light generated by the hologram element 54 is emitted in the direction of the photosensitive drum 12, and the image forming unit 11. It is attached at a predetermined position. The LPH 14 may be configured to move in the optical axis direction of the diffracted light by an adjusting means such as an adjusting screw (not shown). The adjustment means adjusts the image formation position (focal plane) by the hologram element 54 so as to be positioned on the surface of the photosensitive drum 12. Further, a protective layer may be formed on the hologram recording layer 60 with a cover glass or a transparent resin. The protective layer prevents dust from adhering.

<Recording method of hologram element>
Next, a recording method of the hologram element 54 will be described. 4A and 4B are views showing a state in which a hologram element is formed in the hologram recording layer. The illustration of the photosensitive drum 12 is omitted, and only the surface 12A, which is an imaging surface, is illustrated. The hologram recording layer 60A is a recording layer before the hologram element 54 is formed. The hologram recording layer 60A is given a reference symbol A to distinguish it from the hologram recording layer 60 on which the hologram element 54 is formed.

As shown in FIGS. 4A and 4B, coherent light passing through the optical path of diffracted light imaged on the surface 12A is irradiated to the hologram recording layer 60A as signal light. At the same time, when passing through the holographic recording layer 60A, coherent light through the optical path of the diffused light that spreads from the light emitting point to the desired hologram diameter r _H is applied to the hologram recording layer 60A as reference light. For the irradiation of coherent light, a laser light source such as a semiconductor laser is used.

  The signal light and the reference light are irradiated from the same side to the hologram recording layer 60A. In FIG. 4 (A), it irradiates from the LED substrate 58 side, and in FIG. 4 (B), it irradiates from the surface side of the hologram recording layer 60A. Interference fringes (intensity distribution) obtained by interference between the signal light and the reference light are recorded over the thickness direction of the hologram recording layer 60A. Thereby, the hologram recording layer 60 in which the transmission type hologram element 54 is formed is obtained. The hologram element 54 is a volume hologram in which the interference fringe intensity distribution is recorded in the surface direction and the thickness direction. By attaching this hologram recording layer 60 onto the LED substrate 58 on which the LED array 52 is mounted, the LPH 14 is produced.

In FIG. 4 (A) and 4 (B), although the surface 12A is depicted schematically, the hologram diameter _{r H} number mm, the working distance L is from a few cm, the surface 12A is a considerable distance position It is in. For this reason, the hologram element 54 is not formed in a conical shape as illustrated, but is formed in a truncated cone shape as shown in FIG.

  As described above, in the formation method of FIG. 4B, the signal light and the reference light are irradiated from the surface side of the hologram recording layer 60A. That is, the hologram is recorded by the phase conjugate wave. In the present embodiment, it is assumed that a hologram is recorded on the hologram recording layer 60 formed on the LED substrate 58 by a phase conjugate wave. Therefore, the formation method illustrated in FIG. 4B will be described in detail later.

<LED chip array and hologram recording>
In FIG. 2, an example in which six LEDs 50 ₁ to 50 ₆ are arranged in a row in a simplified manner is illustrated. However, in an actual image forming apparatus, the LED array 52 of the LPH 14 has a size corresponding to the resolution in the main scanning direction. Thousands of LEDs 50 are arranged. As described above, the plurality of LED chips 53 in which the plurality of LEDs 50 are arranged are mounted on the LED substrate 58 so that the plurality of LEDs 50 are arranged in the main scanning direction. The hologram element 54 is recorded corresponding to each of these thousands of LEDs 50.

  As the LED array 52, SLED chips (not shown) in which a plurality of self-scanning LEDs (SLEDs) are arranged are arranged in a plurality so that the LEDs are arranged in the main scanning direction. A configured SLED array may be used. In the SLED array, the switch is turned on / off by two signal lines, each SLED is selectively made to emit light, and the data line is shared. By using this SLED array, the number of wires on the LED substrate 58 can be reduced.

  In the present embodiment, it is assumed that the SLED chip is used as the LED chip 53. For example, if the SLED array is converted assuming that 29 SLED chips in which 256 SLEDs are arranged at intervals of 1200 spi (spots per inch) are arranged in a line in the main scanning direction, 1200 dpi is converted. In an image forming apparatus having a resolution of 7424, 7424 SLEDs are arranged at intervals of 21 μm. In the case where “SLED” is used instead of “LED”, the same reference numeral as that of LED 50 is given and referred to as “SLED50”. Further, the SLED chip is also denoted by the same reference numeral and is referred to as “SLED chip 53”.

  Next, defects in chip arrangement and alignment will be described. FIG. 5A is a plan view partially showing the arrangement of SLED chips, and FIG. 5B is a plan view for explaining a defect in the arrangement of SLED chips. In this embodiment, as shown in part of FIGS. 5A and 5B, a plurality of SLED chips 53 in which a plurality of SLEDs 50 are arranged in a one-dimensional manner are staggered over two rows. An arranged SLED array is used.

Figure 5 (A) in a first straight line (A row) and SLED chip 53A ₁ and SLED chip 53A ₂ arranged on a second straight line (B rows along the main scanning direction along the main scanning direction ) and SLED chip 53B ₁ and SLED chip 53B ₂ are arranged on, in the LED array 52 is configured. The first straight line and the second straight line are spaced apart at a constant interval in the sub-scanning direction. The interval between the first straight line and the second straight line is substantially the same as the interval of the LED 50 in the main scanning direction or an interval of several times (1 to 9 times).

When there is no need to distinguish each of the SLED chip _53A 1, SLED chip _53A 2, SLED chips 53B ₁ and SLED chip 53B ₂ are collectively referred to as "SLED chip 53". In the example shown in FIG. 5A, each of the SLED chips 53 has nine SLEDs arranged in a line at a predetermined interval. For example, nine SLEDs 50 ₁ to 50 ₉ are arranged on the SLED chip 53A _1, and nine SLEDs 50 ₁₀ to 50 ₁₈ are arranged on the SLED chip 53B ₁ . In addition, nine SLEDs 50 ₁₉ to 50 ₂₇ are arranged on the SLED chip 53A _2, and nine SLEDs 50 ₂₈ to 50 ₃₆ are arranged on the SLED chip 53B ₂ . As a result, 36 SLEDs 50 ₁ to 50 ₃₆ are arranged at a predetermined interval (for example, 21 μm) along the main scanning direction.

  FIG. 6 is a schematic diagram showing a deviation of the imaging position when a recording optical system for recording a hologram is fixedly arranged. 6 schematically illustrates how the recording optical system moves relative to the LPH 14. However, the recording optical system only needs to move relative to the LPH 14, and the LPH 14 moves relative to the recording optical system. That is, the case where the recording optical system is fixedly arranged is also intended. In the present embodiment, a hologram is recorded by a phase conjugate wave on the hologram recording layer 60 formed on the LED substrate 58 (see FIG. 4B). As shown in FIG. 6, when recording a hologram, an optical system for irradiating signal light and an optical system for irradiating reference light are used as a recording optical system for recording a hologram.

  These recording optical systems are fixedly arranged to record a hologram element 54A corresponding to the SLED 50A arranged on the A row as shown by the solid line, and to correspond to the SLED 50B arranged on the B row as shown by the dotted line. The hologram element 54B to be recorded is recorded. According to this recording method, the imaging spot 62B by the diffracted light of the hologram element 54B is formed in front of the imaging spot 62A by the diffracted light of the hologram element 54A. That is, when the SLED chips 53 are arranged in a zigzag pattern, the hologram element 54A and the hologram element 54B are recorded by the fixedly arranged recording optical system. The spots 62A by the SLED 50A in the A row and the spots 62A by the SLED 50B in the B row 62B is not arranged in a line in the main scanning direction.

  As shown in FIG. 5B, when the SLED chip 53 is inclined with respect to the main scanning direction due to misalignment (alignment misalignment), the SLED 50 arranged in the SLED chip 53 As the interval in the main scanning direction becomes narrow, the positions in the sub scanning direction of the SLEDs 50 arranged on the SLED chip 53 vary. As a result, when the hologram element 54 is recorded so that the spot 62 is formed at a position corresponding to the position of the SLED 50 in the main scanning direction, the spots 62 are not arranged in a line in the main scanning direction. Will be different for each chip. Further, as shown in FIG. 5B, it is difficult to specify the position where the hologram element 54 corresponding to each SLED 50 is recorded with the inclined SLED chip 53. In order to deal with the above-mentioned alignment defect, alignment means such as providing a servo pit for alignment on the LPH 14 side is usually required.

<Formation of spot rows>
FIGS. 7A and 7B are explanatory diagrams for explaining a method of obtaining a spot row corresponding to LEDs spaced apart in the sub-scanning direction. The optical axis of the diffracted light imaged on the surface 12A of the photosensitive drum 12 is made to coincide with the optical axis of the signal light so that the optical axis of the signal light and the optical axis of the reference light intersect at a predetermined angle θ. When the hologram element 54 is recorded by causing the signal light and the reference light to interfere with each other, diffracted light is emitted in a direction that forms an angle θ with the light emitting optical axis.

  In the present embodiment, as shown in FIGS. 7A and 7B, in order to obtain diffracted light imaged on the surface 12A of the photosensitive drum 12, it corresponds to the LEDs 50A arranged on the A row. When recording the hologram element 54A and the hologram element 54B corresponding to the LED 50B arranged on the B row, the hologram is recorded using the same signal light. Here, “same signal light” means signal light having the same irradiation angle, convergence angle, and convergence position. The light emission optical axis of the LED 50A and the light emission optical axis of the LED 50B are parallel, and the optical axis of the diffracted light (ie, signal light) and the light emission optical axis of the LED 50 intersect at an angle θ.

  For this reason, as shown in FIG. 7A, the light emitted from the LEDs 50A of the LED chips 53A arranged on the A row is diffracted by the hologram element 54A in a direction that forms an angle θ with the light emission optical axis, An image is formed on the surface 12A of the body drum 12 to form a spot 62A. Similarly, as shown in FIG. 7B, the light emitted from the LEDs 50B of the LED chips 53B arranged on the B row is diffracted by the hologram element 54B in a direction that forms an angle θ with the emission optical axis, An image is formed on the surface 12A of the body drum 12 to form a spot 62B aligned with the spot 62A in the main scanning direction.

  In FIGS. 7A and 7B, the hologram elements used for diffraction are given a lattice pattern, and the hologram elements not used for diffraction are hatched to distinguish them. For example, as shown in FIG. 7A, when the LED 50A on the A column is caused to emit light, it is diffracted by the hologram element 54A with a lattice pattern, and as shown in FIG. 7B, the B column When the upper LED 50B is caused to emit light, it is diffracted by the hologram element 54B provided with a lattice pattern.

  For example, in an example in which 29 SLED chips in which 256 SLEDs are arranged at intervals of 1200 spi are arranged in a staggered manner to form an SLED array, 7424 SLEDs having different positions in the sub-scanning direction are used. Correspondingly, 7424 spots 62 are formed on the photosensitive drum 12. Even in this case, as shown in FIGS. 7A and 7B, diffracted light that is diffracted at a diffraction angle corresponding to the position in the sub-scanning direction and imaged on the surface of the photosensitive drum 12 can be obtained. In addition, if a hologram is recorded using the same signal light, 7424 spots 62 are formed in a line in the main scanning direction.

  Further, for example, as shown in FIG. 5B, even when the SLED chip 53 is inclined with respect to the main scanning direction and the position in the sub-scanning direction varies due to the alignment failure, the same as above. If a hologram is recorded using the same signal light so that diffracted light imaged on the surface of the photosensitive drum 12 is obtained, the spot 62 corresponding to each LED 50 of the inclined SLED chip 53 is subjected to main scanning. It is formed to line up in a direction. A plurality of spots 62 are formed in a predetermined arrangement direction at regular intervals.

  5A and 5B show an example in which a plurality of LED chips 53 are arranged in two rows in a simplified manner, but in this embodiment, a plurality of LED chips 53 are described as described later. The positions of the plurality of LEDs 50 are respectively measured, and the plurality of LEDs 50 are recognized as “light emitting points” based on the measured values. Based on the measurement positions of the plurality of LEDs 50, corresponding hologram elements 54 are formed.

  That is, a plurality of hologram elements corresponding to each of the plurality of LEDs 50 using the same signal light so that the diffracted light by the hologram element 54 is imaged on the surface of the photosensitive drum 12 to form the aligned spots 62. 54 is formed. As described above, since the hologram is recorded in accordance with the position of the light emitting point, the LED array 52 may be either one-dimensional or two-dimensional, and the displacement of the LED 50 or the LED chip 53 is also compensated.

  As can be seen from FIGS. 7A and 7B, the hologram element 54A and the hologram element 54B have different shapes. When the diffraction efficiency is different due to the different hologram shapes, the diffracted light intensity on the surface 12A of the photosensitive drum 12 is also different. In order to eliminate this inconvenience, the light emission intensity of the LED 50 may be adjusted so that the same diffracted light intensity can be obtained on the surface 12A.

In this embodiment, the photosensitive drum 12 is to be positioned outside of the optical path of the diffused light that spreads from LED50 to the hologram diameter r _H, the angle θ is set to form the light emitting optical axis and the diffracted light optical axis ing. Therefore, even if there is diffused light that is transmitted without being diffracted by the hologram, the transmitted diffused light is not irradiated to the photosensitive drum 12 as background light. Further, a light-shielding film such as a light absorption film may be disposed on the diffusion light transmission side of the hologram recording layer 60 in order to prevent the generation of stray light. The light shielding film is disposed on the optical path of the diffused light that has passed through the hologram recording layer 60.

<Size of hologram element>
In the above example, in an image forming apparatus having a resolution of 1200 dpi, 7424 SLEDs are arranged at an interval of 21 μm. When a spot is formed by condensing light from a condenser lens, the limit of spot miniaturization is determined based on the light diffraction phenomenon. The spot formed by the condenser lens is called an Airy disk from the following relational expression. The diameter (spot size) φ of the Airy disk is expressed as φ = 1.22λ / NA (= 2.44λF) using the wavelength λ and the numerical aperture NA of the condenser lens. Accordingly, when the working distance (≈focal length) is f, f = r _H φ / 2.44λ.

NA = sin θ = r _H / 2f
F (F number) = f / r _H
f: Focal length f = r _H φ / 2.44λ

  In the LPH using the conventional hologram element array, each of the plurality of hologram elements is arranged so as not to overlap each other, as in the case where a plurality of lenses are arranged corresponding to each LED. (Pitch) It is made with the following diameter. The light emitting element pitch is approximately the same length as the interval (pixel pitch) of the minute spots formed on the photosensitive drum, and is several tens of μm. With a hologram element having a diameter of several tens of μm, a working distance of the order of several mm can be obtained due to the spread of the beam by diffraction (diffraction limit), similar to a rod lens. On the other hand, in this embodiment, the working distance of the order of cm is realized by making the diameter of the hologram element larger than the light emitting element pitch.

For example, conventionally, when the diameter of the hologram element than the light emitting element pitch, the 1200dpi resolution must be less than about 20μm hologram size r _H. At this time, assuming that the wavelength is 780 nm, the working distance is limited to 420 μm at most even if the spot size φ is allowed to about 40 μm. Thus, in the prior art, the working distance cannot be increased to the cm order.

On the other hand, when the diameter of the hologram element is made larger than the light emitting element pitch as in the present embodiment, the working distance becomes longer to the order of cm. For example, if the diameter of the hologram element 54 functioning as a condensing lens (hologram diameter r _H ) is 1 mm or more, the working distance is 1 cm or more. For example, when the hologram diameter r _H = 2 mm and the hologram thickness h _H = 250 μm, the spot size φ is about 40 μm (half-value width is about 30 μm) at a working distance of 4 cm.

  Further, when the diameter of the hologram element exceeds 10 mm, the multiplicity of the hologram element becomes extremely high, so that the diffraction efficiency limited by the dynamic range of the material is lowered. Therefore, for example, the diameter of the hologram element may be 10 mm or less depending on the dynamic range of the material.

<Outline of LPH production method>
Next, an example of the manufacturing method of LPH14 is demonstrated. The alignment inspection process and the recording process for recording the hologram will be described in more detail later as a procedure of the “hologram recording program” together with the configuration of the hologram recording apparatus. 8A to 8E are process diagrams showing the manufacturing process of the LED print head. The outline is as described in “Hologram recording method”. Here, since the sectional view in the sub-scanning direction is illustrated, only one LED 50 and one hologram element 54 are illustrated, but the manufacturing process of the LPH 14 including the LED array 52 and the hologram element array 56 will be described.

  First, as shown in FIG. 8A, an LED array 52 in which a plurality of LED chips 53 in which a plurality of LEDs 50 are arranged is mounted on an LED substrate 58 is prepared. A bank portion 64 for damming the photopolymer is formed in a frame shape around the surface of the LED substrate 58. The bank portion 64 is formed, for example, by applying a curable polymer with substantially the same thickness as the hologram recording layer 60 and then curing it by heating or light irradiation. When recording a thin volume hologram, the thickness of the hologram recording layer 60 is about several hundred μm, and similarly, a bank portion 64 having a thickness of several hundred μm is formed. In the case of recording a thick volume hologram, the hologram recording layer 60 has a thickness in the range of 1 mm to 10 mm, and similarly, a bank portion 64 having a thickness of 1 mm to 10 mm is formed.

  Next, as shown in FIG. 8 (B), a photopolymer is poured from a dispenser onto the LED substrate 58 having a frame-shaped bank portion 64 formed in the peripheral portion so as not to overflow from the bank portion 64, and hologram recording is performed. Layer 60A is formed. Next, a protective layer 66 is formed on the hologram recording layer 60A by attaching a thin plate-like cover glass transparent to the recording light and reproducing light on the surface of the hologram recording layer 60A. Thereafter, a chip alignment inspection is performed, and the positions of the plurality of LEDs 50 are measured.

Next, as shown in FIG. 8C, the hologram recording layer 60A made of a photopolymer is simultaneously irradiated with signal light and reference light from the protective layer 66 side, so that the hologram recording layer 60A has a plurality of hologram elements 54. Form. Laser light that passes through the optical path of desired diffracted light in the opposite direction is irradiated as signal light. Further, when passing through the holographic recording layer 60A, the laser light passing through the optical path of the convergent light converging to the light emitting point from the desired hologram diameter r _H, irradiated as the reference light. That is, as shown in FIG. 4B, a hologram is recorded with a phase conjugate wave. As the laser light for signal light and reference light, for example, laser light having a wavelength of 780 nm oscillated from a semiconductor laser is used.

  First, from the measurement data obtained by the above chip alignment inspection, recording signal light and reference light such as a laser light irradiation position, irradiation angle, spread angle, and convergence angle are designed for each LED 50. Here, the diffracted light (reproduced signal light) generated by the hologram element 54 causes the signal light and the reference for each LED 50 so that the spots 62 are formed in a line at predetermined intervals on the photosensitive drum 12. Light is designed. For example, as shown in FIGS. 7A and 7B, signal lights having the same irradiation angle, convergence angle, and convergence position are used for the LEDs 50 having different positions in the sub-scanning direction. A writing optical system for irradiating the designed signal light and reference light is arranged for each LED 50.

  The LED substrate 58 on which the hologram recording layer 60A is formed is moved relative to the recording optical system. At each recording position, a recording optical system for irradiating the signal light and the reference light is arranged so that the diffracted light (reproduced signal light) forms a spot 62 at a desired position on the surface of the photosensitive drum 12. By irradiating signal light and reference light according to the LED 50 at each recording position, a plurality of hologram elements 54 are multiplexed and recorded on the hologram recording layer 60A by spherical wave shift multiplexing.

  Next, as shown in FIG. 8D, the entire surface of the hologram recording layer 60A is exposed to ultraviolet rays to polymerize the photopolymerizable monomer. By this fixing process, the refractive index distribution is fixed to the hologram recording layer 60A. For example, the photopolymer is provided as a mixture of a photopolymerizable monomer and another non-polymerizable compound. In this case, when the photopolymer is irradiated with interference fringes, the photopolymerizable monomer is polymerized in the bright portion, and a concentration gradient is generated in the photopolymerizable monomer. As a result, the photopolymerizable monomer diffuses into the bright part, and a refractive index distribution is generated between the bright part and the dark part.

  Further, the entire surface is exposed to polymerize the photopolymerizable monomer remaining in the dark part to complete the polymerization reaction, so that additional writing or erasing cannot be performed. As hologram recording materials, methods based on various recording mechanisms have been proposed. For example, a material capable of recording a refractive index modulation according to the light intensity distribution is used.

  Finally, as shown in FIG. 8 (E), the plurality of LEDs 50 are caused to emit light sequentially, and it is inspected whether or not desired diffracted light can be obtained by the hologram element 54 formed corresponding to each LED 50. The entire manufacturing process is completed by this inspection process.

  In the above manufacturing process, an example in which the LED 50 and the hologram recording layer 60 are in contact with each other has been described. However, as shown in FIGS. 3B and 3C, an air layer, a transparent resin layer, or the like is used. Thus, the hologram recording layer 60 may be separated from the LED 50. For example, a sheet made of the unrecorded hologram recording layer 60A sandwiched between protective layers may be separately prepared, and the prepared sheet may be attached to the LED substrate 58 on which the LED array 52 is mounted using a support member or the like. . Moreover, you may affix the produced sheet | seat on the LED board | substrate 58 with which the LED array 52 was mounted.

<Hologram recording device>
FIG. 9 is a schematic view showing an example of the configuration of the hologram recording apparatus according to the embodiment of the present invention. As shown in FIG. 9, the hologram recording apparatus is provided with a laser light source 100 that oscillates a laser beam that is coherent light.

  On the light emitting side of the laser light source 100, a shutter 102 that can be opened and closed, a half-wave plate 104 that gives a phase difference of 1/2 wavelength to linearly polarized light components orthogonal to each other, and transmits only polarized light in a predetermined direction. In addition, a polarizing beam splitter 106 that reflects the other polarized light is arranged on the optical path of the laser light in this order. The shutter 102 is connected to a shutter driving unit described later. The shutter 102 is driven in the direction of arrow B by the shutter drive unit, and is in a state where it is inserted into the optical path of the laser light (closed state) or in a state where it is retracted from the optical path (open state).

  A light absorber (not shown) that absorbs the reflected laser light is disposed on the light reflection side of the polarization beam splitter 106. On the other hand, on the light transmission side of the polarizing beam splitter 106, a pair of lenses 108 and 110 are arranged on the optical path of the laser light in this order. The pair of lenses 108 and 110 is a combination of two lenses so that the focal positions coincide with each other, and functions as a beam expander that expands the beam diameter of the laser light. On the focal planes of the lenses 108 and 110, a spatial filter 112 having a pinhole (a minute aperture) 112a is disposed.

  On the light emitting side of the lens 110, a mirror 114 that reflects the transmitted laser light and bends the optical path by a predetermined angle is disposed. In this example, the optical path of incident light is bent by 90 ° by the mirror 114. On the light reflection side of the mirror 114, a half-wave plate 116 and a polarizing beam splitter 118 for branching the laser light into two light waves are arranged in this order on the optical path of the laser light. The optical path of the laser light is branched by the polarization beam splitter 118 into a signal light optical path and a reference light optical path.

  On the light transmission side of the polarization beam splitter 118 (that is, the signal light optical path side), there is a half-wave plate 120, a mirror 122, and an aperture 124, which is a light shielding plate having an opening with a predetermined diameter through which laser light passes. They are arranged in order on the optical path of the laser beam. In this example, the optical path of the laser light transmitted through the half-wave plate 120 is bent by 90 ° by the mirror 122 and is incident on the aperture 124.

  On the light transmission side of the aperture 124, a pair of lenses 126 and 128, a mirror 130 that reflects laser light and bends the optical path by a predetermined angle, and signal light is irradiated to the LPH 14 (unrecorded hologram recording layer 60A) during recording. A stage 136 that holds the lens 134 and the LPH 14 at a predetermined position is arranged on the optical path of the laser light in this order.

  On the light reflection side of the polarizing beam splitter 118, a pair of lenses 140 and 142 are arranged in this order on the optical path of the laser light. The pair of lenses 140 and 142 is a combination of two lenses so that their focal positions coincide. A spatial filter 144 having a pinhole (a minute aperture) 144a is disposed on the focal plane of the lenses 140 and 142. A lens 146 for irradiating the LPH 14 with reference light is disposed on the light exit side of the lens 142. The lens 146 is driven by a lens driving unit, which will be described later, and moves in the direction of arrow C so that the reference light is condensed at a predetermined LED 50 arrangement position.

  A light detector 148 such as an optical power meter is disposed between the lens 140 and the spatial filter 144. The photodetector 148 receives the light emitted from the LED 50 of the LPH 14 during alignment inspection, and measures the light emission intensity of the LED 50. The luminescence intensity measured here is a radiant intensity representing the amount of radiation, and its unit is watts. The light detector 148 is connected to a light detector driving unit described later. The photodetector 148 is driven in the direction of arrow D by the photodetector driving unit, and is inserted into the optical path of the laser beam or retracted from the optical path.

  The stage 136 is connected to a stage driving unit described later. The stage 136 is driven by a stage drive unit and moves in the direction of arrow E, arrow F, and arrow G. An arrow G direction is a direction orthogonal to the paper surface (that is, a depth direction in the drawing), and the stage 136 moves in a three-dimensional space. In the vicinity of the stage 136, stage position detection means 132 such as a position sensor is disposed in order to detect the position of the stage 136.

  At the time of alignment inspection, the stage 136 moves the LPH 14 to a position where the light emission intensity becomes maximum while measuring the light emission intensity of the LED 50 with the photodetector 148. The stage position detector 132 detects the position of the stage 136 after movement, thereby measuring the position of the LED 50 (light emitting point). On the other hand, when recording a hologram, the stage 136 holds the LPH 14 at a predetermined recording position.

  Next, the electrical configuration of the apparatus will be described. FIG. 10 is a block diagram showing the configuration of the drive control system of the hologram recording apparatus. As shown in FIG. 10, the hologram recording apparatus includes a control unit 200 that controls the entire apparatus. A laser drive unit (drive circuit) 202 that drives the laser light source 100 is connected to the control unit 200 in accordance with a control signal. A shutter drive unit 204 that opens and closes the shutter 102 according to a control signal is connected to the control unit 200.

  A stage driving unit 206 that drives the stage 136 is connected to the control unit 200 in accordance with a control signal. In addition, a drive circuit (not shown) is mounted on the LED substrate 58 of the LPH 14 held on the stage 136. The stage drive unit 206 is also connected to this drive circuit and drives each LED 50 formed on the LED substrate 58.

  A lens driving unit 208 that moves the lens 146 in accordance with a control signal is connected to the control unit 200. The control unit 200 is connected to a photodetector driving unit 210 that drives the photodetector 148 in accordance with a control signal. The photodetector driver 210 inserts or retracts the photodetector 148 into the optical path and turns the photodetector 148 on (detected state) or off (non-detected state). In addition, the control unit 200 acquires a detection signal from the photodetector 148. Furthermore, a stage position detection unit 132 is connected to the control unit 200, and a detection signal is acquired from the stage position detection unit 132.

  The control unit 200 includes a CPU (central processing unit) that controls each part of the apparatus and various calculations, a ROM that stores various programs such as an OS, and a RAM that is used as a work area when the programs are executed. The control unit 200 may include an external storage device such as a hard disk that stores various information, an input / output port, a communication interface, and various drives. Each part which comprises the control part 200 is mutually connected by the bus | bath. The CPU reads the program from a storage device such as a ROM or an external storage device, and loads it into the RAM. Then, the loaded program is executed using the RAM as a work area.

  A “hologram recording program” to be described later is stored in a ROM or an external storage device. The position coordinates of the spot 62 are also stored in advance as design values in a storage device such as a ROM or an external storage device.

  In the above hologram recording apparatus, the photodetector 148 is disposed between the lens 140 and the spatial filter 144 to detect the light emission intensity of the LED 50. However, an observation optical system having another configuration may be provided. it can. For example, as shown in FIG. 14, a beam splitter 150 is disposed between the lens 142 and the lens 146, and a lens 152 and a photodetector 154 such as a CMOS sensor are disposed on the light reflecting side of the beam splitter 150. Also good. In this observation optical system, the light emitted from the LED 50 and passing through the lens 146 is reflected by the beam splitter 150. The reflected light is imaged on the surface of the light detector 154 by the lens 152, and the formed light image is detected by the light detector 154.

<Outline of hologram recording operation>
Next, the recording operation of the hologram recording apparatus will be described with reference to FIGS. Operations performed before hologram recording, such as alignment inspection, will be described in detail below. At the time of recording a hologram, the shutter 102 is driven by the shutter driving unit 204 to be in an “open state”. Driven by the laser driving unit 202, laser light having a predetermined wavelength is oscillated from the laser light source 100. The laser light oscillated from the laser light source 100 passes through the half-wave plate 104 and is given a half-wave phase difference to linearly polarized light components orthogonal to each other, and enters the polarization beam splitter 106. For example, the polarization beam splitter 106 transmits one of P-polarized light and S-polarized light, and reflects the other.

  The polarized light in a predetermined direction that has passed through the polarization beam splitter 106 has its beam diameter expanded by a pair of lenses 108 and 110 that function as a beam expander. The spatial filter 112 disposed in the focal plane of the lenses 108 and 110 blocks part of the laser light that cannot pass through the pinhole 112a. The laser light that has passed through the pinhole 112a is collimated by the lens 110, reflected by the mirror 114, and the optical path of the laser light is bent by 90 °.

  The laser light reflected by the mirror 114 passes through the half-wave plate 116 and enters the polarization beam splitter 118. The laser beam that has passed through the polarization beam splitter 118 passes through the half-wave plate 120, is reflected by the mirror 122, and has a predetermined beam diameter corresponding to the aperture diameter by the aperture 124. The stage 136 is driven by the stage driving unit 206, and the LPH 14 is held at a predetermined recording position by the stage 136. The laser light that has passed through the aperture 124 is relayed by the pair of lenses 126 and 128 and reflected by the mirror 130 in a predetermined direction. The laser light reflected by the mirror 130 is collected by the lens 134 and irradiated to the LPH 14 as signal light.

  On the other hand, the laser beam reflected by the polarization beam splitter 118 is relayed by the pair of lenses 140 and 142. The spatial filter 144 arranged on the focal plane of the lenses 140 and 142 blocks part of the laser light that cannot pass through the pinhole 144a. The laser light that has passed through the pinhole 144a is collimated by the lens 142, condensed by the lens 146, and irradiated to the LPH 14 as reference light.

  As described above, the signal light and the reference light are generated by branching the laser light oscillated from the same laser light source 100. These signal light and reference light are irradiated to the same position of the LPH 14 simultaneously and from the same side. As a result, the signal light and the reference light interfere with each other in the hologram recording layer 60A of the LPH 14, and the interference pattern is recorded as a hologram. The same position of the LPH 14 means the same position within a range necessary for recording one hologram (interference fringe).

<Hologram recording program>
In the present embodiment, the light emission intensity is detected for each of the plurality of LEDs 50, and the position of the LED 50 (light emission point) is specified based on the detected value. The position where the light emission intensity is maximum is specified as the position of the LED 50. Then, a plurality of hologram elements 54 are formed so that the spots 62 are formed in a line in the main scanning direction corresponding to each of the plurality of LEDs 50 whose positions are specified. Next, the processing procedure of the “hologram recording program” executed by the control unit 200 will be described. FIG. 11 is a flowchart showing the processing routine of the hologram recording program. By executing this processing routine, a plurality of holograms are sequentially recorded.

  First, in step 100, a control signal for moving the LPH 14 to the initial measurement position for alignment inspection is input to the stage drive unit 206. In response to this control signal, the stage drive unit 206 drives the stage 136, and the LPH 14 is held at the initial measurement position.

  Next, in step 102, a control signal for lighting the measurement target LED 50 is input to the stage driving unit 206. In response to this control signal, the LED 50 mounted on the LED board 58 of the LPH 14 driven by a drive circuit (not shown) of the LED board 58 connected to the stage drive unit 206 is lit for measurement. .

For example, as shown in FIGS. 12A and 12B, an example in which a plurality of SLED chips 53 in which nine SLEDs are arranged in a line at a predetermined interval is arranged in a staggered manner will be described (FIG. 5 ( A) and (B)). Here, measurement and recording are sequentially performed for each SLED chip 53. Therefore, first, the first SLED chip 53A _1, first turns on the SLEDs 50 ₁ chip left, then turns on the SLEDs 50 ₉ chips right end.

  Next, in step 104, a control signal for measuring the position of the LED 50 to be measured is input to the photodetector driving unit 210 and the stage driving unit 206. In response to this control signal, the photodetector 148 is inserted into the optical path of the laser beam and is set in a detectable ON state. Detection signals from the photodetector 148 are taken into the control unit 200 at regular intervals. The stage drive unit 206 moves the stage 136 according to the detection signal of the photodetector 148. The stage position detection unit 132 detects the position of the stage 136. Detection signals from the stage position detection unit 132 are taken into the control unit 200 at regular intervals.

  At the time of alignment inspection, the stage 136 moves the LPH 14 to a position where the light emission intensity becomes maximum while measuring the light emission intensity of the LED 50 with the photodetector 148. The position of the LED 50 (light emitting point) is measured by detecting the position of the stage 136 after the movement by the stage position detecting unit 132. Thereby, the position of the light emitting point is accurately determined.

  As described above, the position of the SLED 50 (light emitting point) to be measured is measured based on the detection signal of the stage position detection unit 132. The position of the kth SLED 50 is specified as coordinates (Xk, Yk, 0) in an XYZ three-dimensional (space) coordinate system. Here, the X-axis direction coincides with the main scanning direction, the Y-axis direction coincides with the sub-scanning direction, and the Z-axis direction coincides with the optical axis direction of the LED 50. Therefore, this coordinate corresponds to the recording position of the hologram element 54 on the LPH 14 (more precisely, the convergence position of the reference light).

  One corner of the LED board 58 of the LPH 14 coincides with the origin (0, 0, 0). The state in which the LPH 14 is held at the measurement position (Z = 0 state) is a state in which the LPH 14 is arranged on the stage 136 at the time of hologram recording (see FIG. 9) or the LPH 14 in the Z-axis direction of the spatial coordinate system. Corresponds to a state in which the exposure device is arranged around the photosensitive drum 12 (see FIG. 1).

The specified position information is input to the control unit 200 and stored in a predetermined storage device. The stored measurement values are appropriately read out and used in the steps described later. In this embodiment, as shown in FIG. 12 (A), it starts measuring the first SLED chip 53A ₁ of column A in this order. First, the position (X ₁ , Y ₁ , 0) of the SLED 50 _{1 at} the left end of the chip is specified, and then the position (X ₉ , Y ₉ , 0) of the SLED 50 _{9 at} the right end of the chip is specified. In the SLED chip 53, since a plurality of SLEDs 50 are arranged in a line at a predetermined interval, if the positions of the SLEDs 50 at both ends are determined, the positions of the other SLEDs are also automatically determined by calculation. The measured position of the SLED 50 is stored in a predetermined storage device in a table as shown in Table 1 below, for example.

Next, in step 106, the plurality of light emitting points (SLED 50) are associated with each of the plurality of condensing points (spots 62). For example, SLEDs 50 ₁ relative to that spot ₆₂ 1, SLEDs 50 ₂ to spot 62 _2, 9 spots 62 ₁ to the spot 62 ₉ is associated with respect to nine SLEDs 50 ₁ ～SLED50 ₉ each. The correspondence relationship between the SLED 50 (light emitting point) and the spot 62 (condensing point) is stored in a predetermined storage device in a table as shown in Table 2 below, for example.

Alternatively, as shown in Table 3, with respect to the position coordinates (X _S1 , Y _S2 , 0) of the spot 62 with respect to the position coordinates (X _k , Y _k , 0) of the SLED 50, The correspondence relationship between the position coordinates and the position coordinates of the spot 62 (condensing point) may be stored in a table. The position coordinates of the spot 62 are stored in advance as design values in a predetermined storage device.

  Next, in step 108, for each of the plurality of hologram elements 54 corresponding to the SLED 50, a recording condition for recording the hologram is acquired. As shown in Table 3, when the correspondence between the position coordinates of the spot 62 and the position coordinates of the SLED 50 is determined, the position where the hologram element 54 is formed is specified according to the position coordinates of the SLED 50 corresponding to the spot 62. . Further, from the position coordinates of the spot 62 and the SLED 50, the signal light and the reference light such as the laser light irradiation position, irradiation angle, spread angle, and convergence angle are designed for each SLED 50. That is, the hologram recording conditions are acquired.

  Next, in step 110, a control signal for moving the LPH 14 to a position for recording the first hologram is input to the stage driving unit 206. In response to this control signal, the stage 136 is driven by the stage drive unit 206, and the LPH 14 is held at the illustrated recording position. The recording position here is a position where the designed reference light is focused on the SLED 50 corresponding to the first hologram. Before the hologram recording operation, a control signal for ending the measurement operation is input to the photodetector driving unit 210. In response to this control signal, the photodetector 148 is retracted from the optical path of the laser beam and turned off.

  Next, in step 114, a control signal for recording the first hologram is input to the lens driving unit 208, the laser driving unit 202, and the shutter driving unit 204. In response to this control signal, the lens 146 is moved, and the optical system is arranged so as to irradiate the signal light and the reference light designed for the LPH 14. For example, as shown in FIGS. 13A and 13B, when recording the hologram element 54A corresponding to the LED 50A arranged on the A row, the lens 146 is set so that the reference light converges on the LED 50A ( When moving down (in the figure) and recording the hologram element 54B corresponding to the LED 50B arranged on the B row, the lens 146 is moved (upward in the figure) so that the reference light is focused on the LED 50B. Moving. The optical system for irradiating the signal light is fixedly arranged.

  Then, the shutter 102 is driven by the shutter driving unit 204 to be in the “open state”, and is driven by the laser driving unit 202, so that the laser light source 100 is turned on and the laser light oscillates. When laser light is oscillated from the laser light source 100, the hologram recording operation is performed as described above, and the first hologram is recorded with the designed signal light and reference light. After the hologram recording is completed, the shutter 102 is driven by the shutter driving unit 204 to be in a “closed state”, and is driven by the laser driving unit 202 to turn off the laser light source 100.

  Next, in step 114, a control signal for moving the LPH 14 to a position for recording the next hologram is input to the stage driving unit 206. In response to this control signal, the stage 136 is driven by the stage drive unit 206, and the LPH 14 is held at the illustrated recording position. The recording position here is a position where the designed reference light is focused on the SLED 50 corresponding to the next hologram.

  Next, in step 116, a control signal for recording the next hologram is input to the lens driving unit 208, the laser driving unit 202, and the shutter driving unit 204. Each unit is driven in accordance with this control signal, and a hologram recording operation is performed. The next hologram is recorded with the designed signal light and reference light. Note that after the hologram recording is completed, the shutter 102 is in the “closed state” and the laser light source 100 is turned off.

Next, in step 118, it is determined whether there is a hologram to be recorded next. If the determination is affirmative, the process returns to step 114 to record the next hologram. Thus, the corresponding hologram elements 54 _{1 to} 54 ₉ are formed in order for each of the SLEDs 50 ₁ to 50 ₉ arranged in a line on the SLED chip 53A ₁ . On the other hand, where in the case of negative determination, for SLED50 all of SLED chip 53A _1, assuming that a hologram is recorded, the process proceeds to step 120.

Next, in step 120, it is determined whether there is an SLED chip 53 to be measured / recorded next. If the determination is affirmative, the process returns to step 100 to perform measurement corresponding to the next SLED chip 53 and record a hologram. For example, in the present embodiment, similarly to the SLED chip 53A ₁ , as shown in FIG. 12B, measurement is performed on the SLED chip 53B ₁ in the B row, and the SLED 50 is handled based on the specified position. The hologram element 54 is recorded. On the other hand, if a negative determination is made here, the routine is terminated assuming that holograms have been recorded for all the SLED chips 53. In the above description, the measurement / recording operation is performed in units of the SLED chip 53. However, the measurement / recording operation may be performed in units of individual SLEDs 50, or the measurement / recording operation may be performed in units of LPH14. Good.

(Other embodiments)
In the above embodiment, at the time of hologram recording for recording one hologram, the LPH on the stage is fixedly arranged, the optical system for irradiating the signal light is fixedly arranged, and the optical system for irradiating the reference light is used. Although the example of moving according to the position of the LED has been described, the LPH and the optical system that irradiates the signal light need only have a certain positional relationship, and the optical system that irradiates the reference light is fixedly arranged to transmit the signal light. You may move LPH with the optical system to irradiate.

  For example, as shown in FIGS. 15A and 15B, an aperture 156 that is a light shielding plate having an opening with a predetermined diameter through which laser light passes is disposed between the lens 128 and the mirror 130. Then, the aperture unit 156, the mirror 130, the lens 134, and the LPH 14 (stage 136) are set on the same substrate 158 as surrounded by a one-dot chain line. The optical system unit 160 is configured to move in the arrow H direction. The LPH 14 is held by a stage 136 installed on the substrate 158.

  When recording the hologram element 54A corresponding to the LED 50A arranged on the A row, the optical system unit 160 is moved (downward in the figure) so that the reference light converges on the LED 50A, and arranged on the B row. When recording the hologram element 54B corresponding to the LED 50B, the optical system unit 160 is moved (upward in the drawing) so that the reference light is focused on the LED 50B. Thereby, LPH14 and the optical system which irradiates signal light move, maintaining a fixed positional relationship. The optical system for irradiating the reference light is fixedly arranged.

  The “hologram recording condition” is acquired by associating a plurality of light emitting points (LEDs 50) with each of a plurality of condensing points (spots 62). If the plurality of spots 62 are designed to be arranged in a line at equal intervals in the main scanning direction on the photoconductor 12, the spots 62 are formed as designed regardless of the arrangement interval of the LEDs 50 in the main scanning direction. Thus, the corresponding hologram element 54 is formed. For example, in the SLED array in which SLED chips in which 256 SLEDs are arranged at intervals of 21 μm are arranged in two rows in a staggered manner, even when the interval in the sub-scanning direction of the SLEDs arranged in two rows is 81 μm, The method has experimentally obtained a spot array with an interval of 21 μm.

  Therefore, the recording optical system used for hologram recording may be any recording optical system capable of recording a hologram in accordance with the acquired “hologram recording condition”. The recording optical systems shown in FIGS. 13A and 13B and FIGS. 15A and 15B are examples. In addition, since the light emitted from the LED 50 is diffracted by the hologram element 54 and collected on the spot 62, the optical axis of the signal light may not be parallel to the sub-scanning direction.

  In the above embodiment, an LED print head including a plurality of LEDs (including SLEDs) has been described. However, other light emitting elements such as an electroluminescent element (EL) and a laser diode (LD) are used instead of the LEDs. May be used. An exposure apparatus including an LD that is a coherent light source has higher energy utilization efficiency than an exposure apparatus that uses an incoherent light source. In addition, the hologram element is designed according to the characteristics of the light emitting element, and unnecessary exposure by incoherent light is prevented, so that even when an LED or EL that emits incoherent light is used as the light emitting element, the coherent light is emitted. As in the case of using the LD to be used as a light emitting element, a fine spot with a clear outline is formed.

  In the above embodiment, an LED array in which a plurality of LEDs are arranged along the length direction has been described. However, a light emitting element array (array light source) such as an LED array is configured as a one-dimensional array. Alternatively, it may be composed of a two-dimensional array. As described in the above embodiment, the positions of the light emitting elements are measured, the positions of the light emitting points are specified based on the measured values, and the spot rows arranged in a row in the main scanning direction are arranged. Since the corresponding hologram is formed so as to be obtained, even if the array light source has a defect such as a misalignment (alignment deviation), these defects are compensated.

  In the above-described embodiment, an example in which a plurality of hologram elements are multiplexed and recorded by spherical wave shift multiplexing has been described. However, as long as a multiplexing system capable of obtaining desired diffracted light is used, a plurality of hologram elements can be obtained by other multiplexing systems. May be recorded multiple times. A plurality of types of multiplexing methods may be used in combination. Other multiplexing methods include angle multiplex recording for recording while changing the incident angle of the reference light, wavelength multiplex recording for recording while changing the wavelength of the reference light, and phase multiplex recording for recording while changing the phase of the reference light. . If multiple recording is possible, separate diffracted light is reproduced without crosstalk from a plurality of holograms recorded in multiple recording.

  In the above embodiment, the image forming apparatus is a tandem type digital color printer, and the LED print head as an exposure apparatus that exposes the photosensitive drum of each image forming unit has been described. Any image forming apparatus capable of forming an image by exposing a photosensitive image recording medium is not limited to the above embodiment. For example, the image forming apparatus is not limited to an electrophotographic digital color printer. The exposure apparatus of the present invention may be mounted on a writing apparatus such as a silver salt type image forming apparatus or optical writing type electronic paper. The photosensitive image recording medium is not limited to the photosensitive drum. The exposure apparatus of the present invention may also be applied to exposure of sheet-like photoreceptors, photographic photosensitive materials, photoresists, photopolymers and the like.

2 PC
3 Image Reading Device 10 Image Forming Process Unit 11 Image Forming Unit 12 Photosensitive Drum 12A Surface 13 Charger 14 LED Print Head 15 Developer 16 Cleaner 21 Intermediate Transfer Belt 22 Primary Transfer Roll 23 Secondary Transfer Roll 24 Conveying Belt 25 Fixing Device 30 Control unit 40 Image processing unit 50 LED
52 LED array 53 LED chip 54 Hologram element 56 Hologram element array 58 LED substrate 60 Hologram recording layer 62 Spot 64 Bank 66 Protection layer 100 Laser light source 102 Shutter 104 1/2 wavelength plate 106 Polarizing beam splitter 108 Lens 110 Lens 112a Pinhole 112 Spatial filter 114 Mirror 116 Half wave plate 118 Polarizing beam splitter 120 Half wave plate 122 Mirror 124 Aperture 126 Lens 130 Mirror 132 Stage position detection means 134 Lens 136 Stage 140 Lens 142 Lens 144a Pinhole 144 Spatial filter 146 Lens 148 Photodetector 150 Beam splitter 152 Lens 154 Photodetector

Claims (4)

A hologram recording layer formed on a substrate on which a plurality of light emitting elements are arranged one-dimensionally or two-dimensionally passes through an optical path of diffused light passing through the hologram recording layer from a position corresponding to the plurality of light emitting elements. First light irradiation means for irradiating one light wave;
Second light irradiation for irradiating the hologram recording layer with a second light wave that passes through the optical path of convergent light that converges outside the optical path of the first light wave and that records the hologram by interference with the first light wave Means,
Measuring means for measuring the position of the light-emitting element that is turned on in a state where at least one of the plurality of light-emitting elements is turned on before recording the hologram on the hologram recording layer;
The light emitted from each of the plurality of light emitting elements converges and a plurality of condensing points are arranged at predetermined intervals in a predetermined arrangement direction, and the light emission is performed based on the position of the light emitting element measured by the measuring unit. Based on the position of the light emitting element and the position of the corresponding condensing point, the plurality of holograms corresponding to each of the plurality of light emitting elements are converged so that the light emitted from the element converges to the corresponding condensing point. An acquisition means for acquiring a recording condition including at least an irradiation angle, a diffusion or convergence angle, and an irradiation position of the first light wave and the second light wave necessary for recording each;
Based on the recording conditions acquired by the acquisition means, the first light irradiation means, the second light irradiation means and the position of the substrate are adjusted, and the first light wave and the second light wave are A recording means for irradiating the hologram recording layer and sequentially recording each of a plurality of holograms corresponding to each of the plurality of light emitting elements on the hologram recording layer;
A hologram recording apparatus comprising: Storage means for storing the position of the light emitting element measured by the measurement means,
The hologram recording apparatus according to claim 1, further comprising: The recording means includes
First position adjusting means for adjusting the position of the first light irradiating means for irradiating the first light wave with respect to the substrate on which the hologram recording layer is formed;
Driving means for driving each of the plurality of light emitting elements to be turned on or off;
Based on the recording conditions acquired by the acquisition means, the first light irradiation means, the second light irradiation means and the position of the substrate are adjusted, and the first light wave and the second light wave are A first control unit that controls the first position adjusting unit and the driving unit to irradiate the hologram recording layer and sequentially record each of a plurality of holograms corresponding to each of the plurality of light emitting elements on the hologram recording layer. 1 control means;
The hologram recording apparatus according to claim 1, further comprising: The recording means includes
The position of the substrate on which the hologram recording layer is formed and the position of the second light irradiating means for irradiating the second light wave are adjusted with respect to the first light irradiating means for irradiating the first light wave. Second position adjusting means;
Driving means for driving each of the plurality of light emitting elements to be turned on or off;
Based on the recording conditions acquired by the acquisition means, the first light irradiation means, the second light irradiation means and the position of the substrate are adjusted, and the first light wave and the second light wave are A first control unit that controls the second position adjusting unit and the driving unit to irradiate the hologram recording layer and sequentially record each of the plurality of holograms corresponding to each of the plurality of light emitting elements on the hologram recording layer. Two control means;
The hologram recording apparatus according to claim 1, further comprising:

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