An illuminator having a sheet emitter and defining a cavity, for illuminating an image bearing surface.
In a printing system (also referred to herein as a “printer”) or a copier system (also referred to herein as a “copier”), an image input module is used to measure reflection from an image bearing surface and from test patches on the image bearing surface. Often, these image input modules are referred to as densitometers, as they are imaging the image bearing surface to detect the toner deposition or lack thereof on the image bearing surface. These measured reflections are used for calibration of the printer.
In prior systems, the image input module used a fluorescent lamp or a rare gas lamp for illuminating the image bearing surface and the test patches. In such systems, the fluorescent lamp or the rare gas lamp used for illumination is a continuous source of light in the cross-process (or fast scan) direction. However, fluorescent lamps and rare gas lamps are relatively expensive. More recently, systems have employed discrete light emitting diodes (LEDs) which are located on a conventional printed circuit board. However, the light output from such systems is limited by the layout and emitting efficiency and uniformity of the LEDs.
An aspect of the disclosure is directed to an illuminator useful in illuminating an image bearing surface. The illuminator comprises a flexible sheet emitter including an emitting layer, the emitting layer adapted to emit light, the sheet emitter having a first face and a second face opposite the first face, the emitting layer being substantially transparent to the light. The illuminator also comprises a reflecting surface shaped to form an optical cavity for the light, the reflecting surface adapted to diffusely reflect the light, the emitter being disposed in the cavity with the first face facing the reflecting surface, the cavity extending along a longitudinal axis, in cross section transverse to the longitudinal axis, the reflecting surface having a non-closed shape along at least a portion of the longitudinal axis thereby defining an aperture through which the light exits the cavity; and the illuminator comprises at least one rigid element extending in the direction of the longitudinal axis, the emitter being mechanically coupled to the at least one rigid element to facilitate directing of light from the emitting layer into the cavity and out of the aperture.
In some embodiments, the emitter is connected to the at least one rigid element. The emitter may be connected to the at least one rigid element along an entire width of the sheet emitter, the connection occurring along at least a portion of the longitudinal axis. The connection may be a direct connection.
In some embodiments, the emitter extends less than 360 degrees around the longitudinal axis.
The emitter may be connected to one of the at least one rigid elements at a plurality of discrete locations along a width of the sheet emitter.
In some embodiments, the emitter is an OLED emitter.
In some embodiments, the rigid element has an element surface having a substantially cylindrical cross section transverse to the longitudinal axis, the mechanical coupling of the emitter being to the element surface. The element surface may be cylindrical.
In some embodiments, the reflecting surface has a substantially cylindrical cross section transverse to the longitudinal axis. The reflecting surface may have a cylindrical cross section transverse to the longitudinal axis.
In some embodiments, the rigid element has an element surface to which the mechanically coupling of the emitter occurs, the element surface being an exterior surface of the rigid element, the second face facing the element surface. The element surface and the second face may be directly connected together. The reflecting surface and the first face may be directly connected together. The rigid element may have a substantially cylindrical cross section and the reflecting surface has a substantially cylindrical cross section.
In some embodiment, the rigid element has an element surface to which the mechanically coupling of the emitter occurs, the element surface being an interior surface of the rigid element, the first face facing the element surface. The element surface and the first face may be directly connected together. The reflecting surface and the first face may be directly connected together.
The at least one rigid element may have a substantially cylindrical cross section and the reflecting surface has a substantially cylindrical cross section.
Another aspect of the disclosure is directed to a printer or electronic copier, comprising a print engine configured to apply a marking medium to an image bearing surface and a system for illuminating the image bearing surface in the printer or electronic copier. The system comprises (i) an illuminator, comprising (a.) a flexible sheet emitter including an emitting layer, the emitting layer adapted to emit light, the emitter having a first face and a second face opposite the first face, the emitting layer being transparent to the light, (b.) a reflecting surface shaped to form an optical cavity for the light, the reflecting surface adapted to diffusely reflect the light, the emitter being disposed in the cavity with the first face facing the reflecting surface, the cavity extending along a longitudinal axis, in cross section transverse to the longitudinal axis, the reflecting surface having a non-closed shape along at least a portion of the longitudinal axis thereby defining an aperture through which the light exits the cavity, and (c.) at least one rigid element extending in the direction of the longitudinal axis, the emitter being mechanically coupled to the at least one rigid element to facilitate directing of light from the emitting layer into the cavity and out of the aperture, and (ii) a light sensor positioned relative to the image bearing surface such that at least one of a specular portion and a diffuse portion of the light reflecting from the image bearing surface is received by the light sensor.
The term “mechanically coupling” as used herein means fastening of two objects indirectly or directly such that a first of the objects (e.g., a surface of a rigid object) is able to facilitate maintenance of or to maintain a shape of a second of the objects (e.g., a flexible object). Mechanical coupling may allow for some independent movement of the second object relative to first object at a location where the first object and the second object are mechanically coupled together if a force is applied to the second object at the location.
The term “connected” as used herein means fastening of two objects indirectly or directly such that a first of the objects (e.g., a rigid object) is able to maintain a shape of a second of the objects (e.g., a flexible object) but independent movement of the second object relative to first object is not possible at least at locations of the connection.
The term “directly connected” as used herein means that two objects are “connected” such that the first object and the second object contact one another, with only adhesive possibly intervening.
The term “substantially transparent” as used herein means a characteristic of a medium indicating that at least some light rays travel straight through the medium. A transparent medium may be only partially transparent and allows for the possibility that the medium is partially translucent (i.e., at least partially diffusely transmissive).
The term “substantially cylindrical” as used herein means having a surface extending along a longitudinal axis and curved to have a cross section transverse to the longitudinal axis that is round or oval or polygonal in shape, or a continuous or discrete approximation of said shapes.
The nature and mode of operation of the present disclosure will now be more fully described in the following detailed description of the disclosure taken with the accompanying drawing figures, in which:
At the outset, it should be appreciated that like drawing numbers on different drawing views identify identical, or functionally similar, structural elements of the embodiments set forth herein. Furthermore, it is understood that these embodiments are not limited to the particular methodology, materials and modifications described and as such may, of course, vary. It is also understood that the terminology used herein is for the purpose of describing particular aspects only, and is not intended to limit the scope of the disclosed embodiments, which are limited only by the appended claims.
Aspects of the present disclosure are directed to techniques for increasing irradiance from a sheet illuminator. As described in greater detail below, sheet emitters, such as OLEDs, are known. According to aspects of the present disclosure, a diffusely reflecting surface is shaped to form an optical cavity with an aperture, and the sheet illuminator is located within the cavity. The light from the sheet illuminator is reflected from the wall(s) of the cavity and out through the aperture. As discussed below, the light from the cavity projected onto a surface from a given distance can have a greater irradiance at the surface than the light projected from the given distance onto the surface by the sheet illuminator when it is flat state.
H
0
≈π*N
0*(1+ρ)*sin(Θ1/2) Eqn. 1
According to aspects of the disclosure, it has been discovered that by providing a sheet emitter (e.g., a flexible sheet emitter) with a reflecting surface configured to form a cavity, the irradiance at a surface (e.g., an image bearing surface of a copier or a printer) can be increased over what can be provided by a corresponding flat sheet emitter having a reflecting surface. It will be appreciated that, for certain aperture angles α and distance d, the cylindrical source provides a substantial increase in irradiance at surface S over the equivalent flat sheet emitter.
According to aspects of the present disclosure, a sheet emitter is incorporated into an illuminator having a cavity C as set forth below.
Illuminator 300 comprises a flexible sheet emitter 200, a reflecting surface 310 and at least one rigid element 320.
Referring to
Referring again to
The at least one rigid element 320 extends in the direction of longitudinal axis LA, with the sheet emitter being mechanically coupled to the at least one rigid element. In the illustrated embodiment, the rigid element has an element surface 322 to which the sheet emitter is mechanically coupled. In the illustrated embodiment, the element surface is an exterior surface of the rigid element, and second face 204 is facing element surface 322. By coupling the sheet emitter to the rigid element, directing of light from the emitting layer into the cavity C and out of aperture A is facilitated by suitably shaping the sheet emitter. Although the at least one rigid element is shown as a single piece, it may comprise two or more pieces that combine to facilitate directing of light.
Sheet emitter 200 may be connected to the at least one rigid element along an entire width W of the sheet emitter. The connection may occur along at least a portion of longitudinal axis LA or may occur along the entire longitudinal axis LA such that an entire surface of the sheet emitter is connected to the at least one rigid element. The sheet emitter may be connected to the at least one rigid elements continuously along the width W or at a plurality of discrete locations along width W.
The connection may be a direct connection (i.e., with no more than an adhesive between the sheet emitter and the rigid element) or with additional material between the sheet emitter and the rigid element.
In some embodiments, the shape of the element surface in cross section transverse to the longitudinal axis and, as a result of the mechanical coupling, and the shape of the sheet emitter in the cross section are substantially cylindrical, and in some embodiments, the cross sections of the element surface and the emitter surface are cylindrical; however, element surface and, as a result of the mechanical coupling, sheet emitter may have any suitable shape in cross section. It is to be appreciated that reflecting surface 310 forms the cavity and thereby may provide for an increase in radiance of the illuminator. The sheet emitter may extend 360 degrees around the longitudinal axis or may extend less than 360 degrees around the longitudinal axis. It will be appreciated that light from either face of the sheet emitter 202, 204 may reflect from the reflecting surface one or more times. Some light from the faces may exit aperture A without reflecting even once.
In some embodiments, the reflecting surface 310 in cross section transverse to the longitudinal axis LA is substantially cylindrical; however, reflecting surface 310 may have any suitable shape in cross section providing for reflecting of light from the emitting layer 210 and exiting of the light from aperture A. In some embodiments, reflecting surface 310 has a cylindrical cross section transverse to longitudinal axis LA.
Further embodiments of illuminators according to aspects of the present disclosure for use in copiers and printers in a manner similar to illuminator 300 are discussed below. In the embodiment illustrated in
In the embodiment of
As in embodiments where the sheet emitter is connected to an exterior element surface of the rigid element, in embodiments where sheet emitter is connected to an interior element surface 612 of the rigid element, the element surface and the first face may be connected together. Sheet emitter 200 may be connected to the at least one rigid element along an entire width W of the sheet emitter. The connection may occur along at least a portion of longitudinal axis LA or may occur along the entire longitudinal axis LA such that an entire surface of the sheet emitter is connected to the at least one rigid element. The sheet emitter may be connected to the at least one rigid element continuously or at a plurality of discrete locations along width W of the emitting layer. The connection may be a direct connection (i.e., with no more than an adhesive between the sheet emitter and the rigid element) or with additional material between the sheet emitter and the rigid element 610.
In some embodiments, the shape of element surface 612 in cross section transverse to the longitudinal axis LA and, as a result of the mechanical coupling, the shape of the sheet emitter are substantially cylindrical. In some embodiments, the shape of the element surface 612 in cross section transverse to longitudinal axis LA and the shape of the sheet emitter surface are cylindrical. However, the shape of element surface in cross section transverse to longitudinal axis LA and, as a result of the mechanical coupling, sheet emitter may have any suitable shape in cross section. It is to be appreciated that reflecting surface 310 forms the cavity C and thereby may provide for an increase in radiance of the illuminator. The sheet emitter and emitting layer may extend 360 degrees around the longitudinal axis or may extend less than 360 degrees around the longitudinal axis LA. The sheet emitter and emitter layer may be angularly coextensive with the reflecting surface relative to longitudinal axis LA or may be of smaller angular extent than the reflecting surface.
In some embodiments, the reflecting surface 310 in cross section transverse to the longitudinal axis LA is substantially cylindrical, however, reflecting surface may have any suitable shape in cross section providing for reflecting of light from the emitting layer and exiting of the light from aperture A. In some embodiments, the reflecting surface has a cylindrical cross section transverse to longitudinal axis LA.
In the embodiment of
In an embodiment, an image bearing surface 10 used in the system is on a photoreceptor comprising a belt or a drum configuration. However, it may also be the printed document, or any other surface bearing an image.
Lens array 3 is interposed between the image bearing surface 10 and the sensor array 2. The lens array may comprise, for example, a Selfoc® lens or other micro lens arrangement with a predetermined acceptance angle β. A Selfoc® lens is a gradient index lens which consists of fiber rods with parabolic index profile. In one embodiment, the Selfoc® lens has an acceptance angle β of about ±9 degrees.
In some embodiments, the linear array sensor is, for example, a full width array (FWA) sensor. A full width array sensor is defined as a sensor that extends substantially an entire width (perpendicular to a direction of motion) of the moving image bearing surface. The full width array sensor is configured to detect any desired part of the printed image, while printing real images. The full width array sensor may include a plurality of sensors equally spaced at intervals (e.g., every 1/600th inch (600 spots per inch)) in the cross-process (or fast scan) direction (see for example, U.S. Pat. No. 6,975,949, which is hereby incorporated by reference herein). It is understood that other linear array sensors may also be used, such as contact image sensors, CMOS array sensors or CCD array sensors.
In some embodiments, sensor array 2 includes a specular reflectance sensor array and a diffuse reflectance sensor array as discussed in detail in U.S. Pat. No. 7,763,876 to Banton, et al. which is hereby incorporated by reference herein.
Specifically, the
Also shown in the
Typically, a printer using control systems which rely on monitors such as 56, 52, and 58 require the deliberate creation of what shall be here generally called “test patches” which are made and subsequently measured in various ways by one or another monitor. These test marks may be in the form of test patches of a desired darkness value, a desired color blend, or a particular shape, such as a line pattern; or they may be of a shape particularly useful for determining registration of superimposed images (“fiducial” or “registration” marks). Various image-quality systems, at various times, will require test marks of specific types to be placed on photoreceptor 210 at specific locations. These test marks will be made on photoreceptor 210 by one or more lasers such as 14C, 14M, 14Y, and 14K. Printing process may be controlled, for example, by a print controller 200.
A calibration procedure could be determined so that the signals from the linear sensor array 2 can be used to work out the true specular reflectance and the difference between the specular and diffuse reflectances of the image being measured. For example, the amount of diffuse light being reflected at the specular angle is determined and the subsequent specular sensor readings are corrected by subtracting a fraction of the diffuse sensor signal from the specular sensor signal as discussed in U.S. Pat. No. 8,010,001, herein incorporated by reference.
As is familiar in the art of “laser printing,” by coordinating the modulation of the various lasers with the motion of photoreceptor 210 and other hardware (such as rotating mirrors, etc., not shown), the lasers discharge areas on photoreceptor 210 to create the desired test marks, particularly after these areas are developed by their respective development units 16C, 16M, 16Y, 16K. The test marks must be placed on the photoreceptor 210 in locations where they can be subsequently measured by a (typically fixed) monitor elsewhere in the printer, for whatever purpose.
In an embodiment, the image input module 100, as described above, can be placed just before or just after the transfer station 20 where the toner is transferred to the sheet, for example, on monitors such as 58, 56. In another embodiment, the image input module 100, may be placed directly on a printed sheet as the printed sheet comes out of the machine, for example, on a monitor such as monitor 52.
It will be appreciated that various of the above-disclosed and other features and functions, or alternatives thereof, may be desirably combined into many other different systems or applications. Various presently unforeseen or unanticipated alternatives, modifications, variations or improvements therein may be subsequently made by those skilled in the art which are also intended to be encompassed by the following claims.