60/151, 471, filed August 30,1999, the entire disclosure of which is incorporated herein by reference.

BACKGROUND The present invention relates to a color measurement device; and more particularly to an automated scanning color measurement device for printer calibration, profiling and process control.

Communicating and reproducing exact color has always been difficult. But it has been important enough for the graphic arts, photo, pre-press and print industries to traditionally go through enormous length to make the colors come out right. However, todays technologies and workflows often make the traditional methods difficult to apply. Direct-to- plate printing and direct digital pre-press make traditional film-based proofing methods impossible. The growing use of digital cameras call CMYK-based workflows into question.

And while traditional methods of color management worked backwards from the final output, in todays fast-paced world, color is often needed to be worked with long before the final output process has been decided.

Color management systems seek to replace the old add-hock practices with an open, cross-platform standard method of communicating color information as accurately as possible, within the limitations of the devices used, throughout the reproduction process. If properly implemented, a color management system eliminates multiple iterations of proofing and re-scanning, allows easy re-purposing of color files for different types of output, and attaches an unambiguous color meaning to each piece of color information in a respective document. It can save time and money, and open up new workflows that would have previously been impossible.

Color management systems are necessary because the way colors are usually defined is ambiguous. Most applications represent color using either RGB (red, green, blue) or CMYK (cyan, magenta, yellow, black) model. Both RGB and CMYK are referred to as device-specific or device-dependent color models, because the actual color produced depends on the behavior of the device producing it.

Device-specific color spaces represent color using numerical values that indicate the amount of each color a device uses to produce the color. RGB colors may indicate the signal strength generated by a scanner as a sensor when it records light through the red, green, and blue filters, or may represent the voltage sent to the guns that excite the monitors red, green, and blue phosphers. CMYK colors specify the amount of each ink laid down to produce a particular color. The problem is that the same RGB or CMYK values will produce a different color on different devices. To keep the color consistent across different devices that use different color spaces, a color management system transforms the device-specific RGB or CMYK values to produce the correct color on each device.

There are three parts to color management: calibration, profiling and process control.

Calibration reduces the production of non-sellable product by maintaining color consistency from job to job, from one day to the next. Recently, RIP (raster image processors) manufacturers recognize that printers could produce excellent color output, but tend to drift over time, causing consistency problems for users. Most software and hardware RIPs now come with some type of calibration-linearization program. The purpose of these calibration routines is to allow user to compensate for changes for in print quality related to temperature, humidity, toner-ink, paper and use over time.

A calibration routine contains a test target, which usually consists of about twenty color patches that range from 0% up to 100% ink coverage for each ink color that the printer uses (i. e. a 4-color printer would consist of 80 patches). After printing the calibration target, the customer must utilize a sensor device, such as the device described in U. S. Patent No.

6,020,583 to Wallowit, et al., to generate the density values for each of the color patches printed on the test target. These values are then directly entered into the RIP calibration routine. The calibration software allows the user to compare the data from previous calibrations to the calibration data that was just entered. The customer then determines, by viewing a chart, if the printer has drifted or needs to be calibrated.

A similar process will be utilized when building a device profile for a printer. To profile a printer, the printer is used to print a target containing known device-specific values (usually CMYK or CMY, though former quoters are RGB devices and some inkjet printers act as RGB devices). Then, CIE values of the printer results are measured using a spectrophotometer or colorometer, such as the sensor disclosed in U. S. Patent No. 6,020,583.

Printers and presses are significantly challenging to profile. Conventionally, hundreds or thousands of target patches must be analyzed in building the profile. If done by hand utilizing the sensor disclosed in U. S. Patent No. 6,020,583, for example, such a profiling operation would take an extraordinary long time since each patch must be tested individually.

Accordingly, there is a need for a automated device for performing color measurements on a multitude of patches applied to a target and for transmitting such color readings to a computer device programmed to calibrate or profile the device that created the patches applied to the target.

SUMMARY The present invention provides an automated scanning color measurement device utilizing the sensor technologies disclosed in U. S. Patent No. 6,020,583. The device includes a tray for receiving a target sheet having a plurality of color patches printed thereon and sheet feeding mechanisms for carrying the sheet into the apparatus where the patches are automatically scanned by a color sensor cartridge, reciprocatable along the width of the sheet, to take colorometric, densitometric, and/or spectrophotometric readings of the color patches.

The device transmits such readings to a host computer or some other associated device for performing calibrations and/or building profiles on the device (such as a printer) that created the patches applied to the target sheet.

One aspect of the present invention provides an apparatus for automatically collecting a plurality of color readings from a corresponding plurality of color patches applied to a sheet, and for transmitting the plurality of color readings to a host computer. The apparatus includes: a color sensor mounted on a carriage motorized for reciprocation along a predefined carriage path; a feed for feeding the sheet along a predefined feed path, where an exposed portion of the feed path runs in a direction substantially perpendicular to at least a sensing portion of the carriage path, and where the exposed portion of the feed path is substantially adjacent to the sensing portion of the carriage path to allow the color sensor to sense colors applied to the sheet fed to the exposed portion of the feed path, along the entire sensing portion of the carriage path; a carriage control for controlling the position of the color sensor along the sensing portion of the carriage path; a feed control for controlling the position of the sheet along the feed path; an interface for providing a data link to a host computer; and a microcontroller operatively coupled to the carriage control, the feed control, the color sensor and the interface, and including circuitry and/or programming adapted to operate the carriage control and feed control so that the color sensor is separately exposed to each of the color patches applied to the sheet, and for each separate exposure of the color sensor to one of the color patches, is further adapted to activate the color sensor, obtain a color reading from the color sensor, and transmit data corresponding to the color reading over the data link via the interface.

Preferably, the color sensor includes: a color sensor housing; a plurality of LEDs mounted within the color sensor housing, each emitting light of a substantially different wavelength band spaced in a visible spectrum; a reference photodetector mounted within the color sensor housing; a sample photodetector mounted within the color sensor housing; a reflector positioned in a first optical path between the reference photodetector and the plurality of LEDs and adapted to direct a first portion of light emitted by each of the LEDs to the reference photodetector; an aperture in the color sensor housing positioned in a second optical path between the sample photodetector and the plurality of LEDs, where the second optical path is closed upon the aperture being positioned adjacent to the sheet; and a controller, operatively coupled to the reference photodetector, the sample photodetector and the plurality of LEDs, adapted, upon activation, to successively activate the LEDs, either alone or in combination, and to provide a color sensor output based upon a ratio of readings taken from the sample photodetector and reference photodetector.

It is also preferred that the reflector is an optical coating applied to either the color sensor housing an object (such as a circuit board) mounted in the color sensor housing, wherer the optical coating provides a substantially non-absorbing, integrating surface on color sensor housing or object. This the optical coating is preferably a white coating such as a white silk-screen.

It is also preferred that the color sensor includes: an interface panel including a plurality of leads operatively coupled to the controller; a first circuit board coupled to the interface panel and including the reference photodetector mounted on a top surface thereof, the sample photodetector mounted on a bottom surface thereof, and a plurality of holes extending through the circuit board and distributed around the sample and reference photodetectors; and a second circuit board coupled to the interface panel and positioned over the first circuit board, where the second circuit board includes the plurality of light-emitting diodes mounted to a bottom surface thereof, and where each of the LEDs extending at least partially through respective ones of the plurality of holes in the first circuit board, and where the second circuit board further includes the optical coating applied to the bottom surface thereof. The interface panel is preferably adapted to be retrofit on a printer carriage of a conventional ink-jet printer.

In one embodiment, the interface is a universal serial bus (USB) interface and the apparatus further comprises a USB controller operatively coupled between the microcontroller and the USB interface. In another embodiment, the interface is a network interface and the apparatus further comprises a network controller operatively coupled between the microcontroller and the network interface. The network interface may be a TC/PIP network interface, the network controller may be a TC/PIP controller, and the network controller may include its own IP address, so that the apparatus is capable of interface with a host computer over the Internet.

In another embodiment the apparatus includes a calibration plate mounted adjacent to a calibration portion of the carriage path, and the microcrontoller circuitry and/or programming is adapted to operate the carriage control so that the color sensor is exposed to the calibration plate during a calibration procedure for the color sensor.

It is another aspect of the present invention to provide a method for automatically collecting a plurality of color readings from a corresponding plurality of color patches applied to a sheet. The method includes the steps of : (1) providing a device including a color sensor mounted on a carriage motorized for reciprocation along a predefined carriage path, and a feed for feeding the sheet along a predefined feed path, where an exposed portion of the feed path runs in a direction substantially perpendicular to at least a sensing portion of the carriage path, and where the exposed portion of the feed path is substantially adjacent to the sensing portion of the carriage path to allow the color sensor to be directed to the sheet fed to the exposed portion of the feed path, along the entire sensor portion of the carriage path; (2) controlling the carriage and feed so that the color sensor is separately exposed to at least a set of the color patches applied to the sheet; (3) for each separate exposure during the controlling step, activating the color sensor to obtain a color reading for the particular color patch; and (4) transmitting data corresponding to the color reading to a host computer operatively coupled to the device.

Preferably, responsive to the step of activating the color sensor, the color sensor will perform the following steps: (a) activating at least one light source, the light source emitting light of a wavelength band; (b) directing a first portion of the light emitted by the light source to a reference photodetector; (c) directing a second portion of the light emitted by the light source to an aperture adjacent to the color patch; (d) directing light reflected from the color patch to a sample photodetector; (e) calculating a ratio of readings taken from the reference photodetector and the sample photodetector; and (f) deriving the color reading from the ratio.

Preferably, steps (a) through (e) are repeated for at least three light sources, each emitting light of a substantially different wavelength, where the color reading derived in step (f) is derived from the ratios calculated in step (e) for the at least three light sources.

In one embodiment the method includes the steps of providing at least one calibration plate in a position adjacent to a calibration portion of the carriage path, controlling the carriage and feed so that the color sensor is exposed to the calibration path, activating the color sensor to obtain a color reading for the calibration plate, and calibrating the color sensor using, at least in part, the color reading taken for the calibration plate.

In another embodiment the method includes the steps of controlling the carriage and the feed so that the color sensor is positioned adjacent to an encoded patch applied to the sheet; activating the color sensor on the encoded patch applied to the sheet; extracting information from the color sensor readings obtained from the encoded patch by the color sensor, where the information pertains, at least in part, to locations of color patches on the sheet; and performing the step of controlling the carriage and feed so that the color sensor is separately exposed to at least a set of the color patches applied to the sheet, in accordance with, at least in part, the information extracted from the encoded patch.

In yet another embodiment, the method further includes the steps of receiving from the host computer information pertaining to locations of color patches on the sheet, and performing the step of controlling the carriage and feed so that the color sensor is separately exposed to at least a set of the color patches applied to the sheet, in accordance with, at least in part, the information received from the host computer.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of an automated scanning color measurement apparatus according to a preferred embodiment of the present invention; Fig. 2 is a schematic diagram of the sensor carriage and paper feed mechanisms of the embodiment of Fig. 1 ; Fig. 3 is a block diagram of the various mechanical and electrical components of the preferred embodiment of the present invention ; Fig. 4a is an exploded perspective view of the color sensor utilized by the automated scanning color measurement apparatus according to a preferred embodiment of the present invention ; and Fig. 4b is another exploded perspective view of the color sensor utilized by the automated scanning color measurement apparatus according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION The present invention is an automated scanning color measurement apparatus utilizing the sensor technologies disclosed in U. S. Patent No. 6,020,583 ("the'583 Patent"), the disclosure of which is incorporated herein by reference. As shown in Figs. 1 and 2, the apparatus 10 includes a tray 12 for receiving a target sheet 14 having a plurality of color patches 16 printed, or otherwise applied thereon, and sheet feeding mechanisms 17 for carrying the sheet 14 upwards into the apparatus where the patches 16 are automatically scanned by a color sensor cartridge 20 to take colorimetic, densitometric and/or spectrophotometric readings of the color patches. The device 10 will transmit such readings to a host computer or some other associated device operatively coupled to the apparatus.

The present embodiment is a conventional ink-jet printer, such as a Hewlett Packard DeskJet 420C printer, in which the ink j et cartridge and control circuitry have been removed and replaced with a color sensor cartridge 20 (described below) and associated control circuitry for controlling the color sensing operation (also described below). The paper feed mechanics 17, printer carriage 21 and associated mechanics remain but are now controlled by the new control circuitry. The interface to the device is preferably no longer the parallel (IEEE-1284) interface but both serial RS-232 and USB configured in an either/or fashion. To operate, the user simply places the sheet 14 with the color patches 16 into the input tray 12 of the apparatus 10 and presses one of the buttons 18 to begin the scanning operation. The new control circuitry controls the feed mechanics 17 to position the target sheet 14 at a vertical orientation with respect to the sensor cartridge 20 and controls the carriage 21 to position the sensor cartridge at a horizontal orientation with respect to the width of the sheet. The new control circuitry controls the feed mechanics and the carriage such that the sensor cartridge 20 is positioned one of the patches on the target sheet 14. When the sensor cartridge 20 is positioned before the patch, the new control circuitry activates the color sensor housed in the sensor cartridge to obtain a color reading for the patch. Thereafter, the new control circuitry controls the feed mechanics and the carriage such that the sensor cartridge 20 is positioned a next one of the patches on the target sheet 14; after which, the new control circuitry activates the color sensor housed in the sensor cartridge to obtain a color reading for the next patch.

This process is repeated until the desired number of patches on the target sheet have been sensed. Once all the desired color readings are taken, the device-independent data corresponding to the color patches 16 present on the printed color target 14 are transmitted via the RS-232 and/or USB interfaces to a host computer or the like.

As shown in Fig. 3, the new control circuitry (including software) 56 is operatively coupled to the color sensor cartridge 20 via data link 57, the motor control circuitry 58 controlling the paper feed (stepper) mechanisms 17 and the carriage (servo) mechanisms 21 via data link 59, the universal serial bus (USB) interface 60 via data link 61, the serial interface 62 via data link 63, and the front-panel human-interface buttons and LEDs 18,19 via data link 64. The motor control circuitry 58 utilizes feed back from the linear encoder 65 in controlling the horizontal position of the color sensor cartridge 20. The new control circuitry 56 includes a microcrontroller 66, associated program/data memory 68 and a USB controller 70.

As shown in Figs. 4a and 4b, the color sensor cartridge 20 includes a cartridge housing 22 having an interface panel 24 for interfacing the electronic circuits and devices of the color sensor cartridge with data link 57, operatively coupled to the new control circuitry 56. The panel 24 includes a plurality of leads 26 operatively coupled by connectors 28 to associated leads on three circuit boards 30,32 and 34. The arrangement of leads is preferably configured so that the color sensor cartridge 20 may be retrofit directly on a carriage 21 of an existing ink jet printer.

The color sensing cartridge further includes a plurality of light-emitting diodes (LED's) 36 (not all shown), where each of the LED's emit light of a substantially different wavelength band spaced in the visible spectrum ; a reference photo detector 38; a sample photo detector 40 an optical coating applied to the lower side 42 of the circuit board 32 (acting as an optical cap) for directing a first portion of light emitted by each of the LED's to the reference photo detector 38 ; a reflector cone 44 for directing a second portion of the light emitted by the LED's to the paper 14; and a receptor piece 46 for directing the diffuse portion of the light reflected from the paper 14 to the sample photo detector 40.

The silk-screened, white coating on the lower-most side 42 of the circuit board 32 provides a non-absorbing integrating surface directly over the LED's such that a portion of the light generated by the LED's reflects off this integrating surface to the reference photo detector 38. The LED's are each mounted to the circuit board 32 and extend downward partially through annular holes 48 bored though the circuit board 34. The portions of the LED's 36 extending through the circuit board 34 extend into cylindrical channels 50 bored axially through the receptor piece 46.

The reflector cone 44 includes an inner, conical reflecting surface, positioned in alignment with the cylindrical channels 50 and angled at 22.5° with respect to the cylindrical channels such that the sample portion of the light directed downwards through the cylindrical channels will reflect off the conical reflecting surface and be directed towards the focal aperture 52 and paper 14 at an angle of 45 °. Light reflected from the paper 14 will reflect back through the focal aperture 52 in the optical cap 44 through the cylindrical channel 54 extending axially through the receptor piece 46 to the sample photo detector 40.

When the sensor cartridge 20 is activated, the on-board LED controls 70 (see Fig. 3) will cause each of the LED's (either alone or in combination) to be successively activated and a reflectance measurement for the particular color patch 16 will be provided based upon a ratio of the output from the sample photo detector 40 and reference photo detector 38. An A/D converter 72 (see Fig. 3) converts the analog signals from the sample and reference photo detectors 40,38 into digital data acceptable by the new control circuitry 56. The above reflectance method is described in detail in The'583 Patent.

Because the color sensor cartridge is self contained and removable, other sensor cartridges may be provided so that the apparatus 10 may be easily integrated with other equipment installed on the carriage 21.

The three buttons 18 provided on the chassis include a Calibrate/Cartridge Change button, a Measure/Move Paper button and a Power button. To create a profile of a peripheral device, such as a printer, the user may follow the following simple steps. First, the user will define a profile name for the peripheral device using the support software resident on the host computer operatively coupled to the apparatus 10. Next, the user will print a test sheet 14 using the peripheral device where the test sheet preferably includes a plurality of patches 16 of different and varying colors, as will be apparent to those of ordinary skill in the art. Next, the user inserts the test sheet in the paper tray 12 of the device and presses the"Measure" button. From there, the sheet 14 is taken into the device 10 and the patches 16 are automatically scanned by the sensor cartridge 20 contained therein. The device then transmits the sensor readings for each of the color patches 16 to the host computer where the resident software extracts the data from the messages sent by the device and creates a profile, which is then saved under the profile name created above. Conventional profiling software capable for use with the present invention includes the Fiery@ Print Calibrator (Fiery is a registered trademark of Electronics for Imaging, Inc.).

Referring to Figs. 2 and 3, it is preferred that a set of calibration plates 72 (one shown) are positioned within the chassis of the apparatus 10 in a position along the carriage path so that the sensor cartridge 20 is capable of being placed before the calibration plate 72 during a calibration operation. Preferably, a non-reflecting"black"calibration plate and a reflecting diffuse"white"calibration plate are provided in the apparatus 10 along the carriage 21 path.

When the Calibrate button is pressed by the user, the carriage 21 will transport the sensor cartridge to before the calibration plate (s) 72 mounted within the chassis of the apparatus 10.

At this point, the calibration will take place in accordance with the steps described in The '583 Patent.

In certain embodiments the new control circuitry 56 is adapted to perform a complete profiling operation of a peripheral device. In other words, the new control circuitry 56 is configured to produce an ICC profile directly after measuring an"n"number of patches 16.

Preferably, the software in the new control circuitry 56 includes conventional edge detection algorithms, where opposing LED's 36 of the sensor cartridge 20 are used to detect edges of patches 16 or edges of the paper 14. Alternatively, a less accurate detection algorithm can be used with a single LED 36.

It is also within the scope of the present invention that a bar-coded type patch 74 (see Fig. 2) be provided where information in the bar-coded type patch 74 specifies the arrangement and orientation of the patches 16 on the particular sheet 14. This can be used for auto-queuing sheets from different jobs. A conventional bar-code may be used, which would require a conventional bar-code reader in the apparatus 10. However, it is preferred that by patch 74 will be a color patch similar to color patches 16, where the color readings and dimensions (width & height) detected by the color sensor cartridge 20 will be translated into information by the new control circuitry 56 to specify the arrangement and orientation of the patches 16 on the particular sheet.

Such"Page definition"instructions may also be downloaded to the new control circuitry 56 from the host computer, where a plurality of sets of instructions may correspond with a plurality of different types of bar codes that may be present on the sheets.

Accordingly, the"bar code"will tell the unit 10 how the patches 16 are arranged so that automatic profiling may occur.

The present apparatus 10 may also be used to quickly check the calibration of a peripheral device such as a printer. This method would report to the user that a sheet being measured is within limits and tolerance is stored within the apparatus 10. Such a method would keep the user from having to recalibrate a printer more than is necessary.

The new control circuitry 56 may also be modified to include a rapid calibration algorithm which would be used to interpolate a complete set of measurements for tone reproduction based upon measuring all of the patches once (or occasionally being updated) and then in normal use, measure only a few key patches. After measuring the few key patches, the calculating and reporting of the rest of the patches may be performed based upon the algorithmic interpolation method.

Preferably, the new control circuitry 56 performs data logging of measurements from the last"n"number of sheets 14. This data may be extracted by service personnel to help in trouble shooting peripheral device problems. The extracting of the data may be performed via the communication ports 60,62 over a network.

In one embodiment, the apparatus 10 is"web savvy."In other words, the new control circuitry 56 includes a TC/PIP network interface and associated controller, where the network controller provides the apparatus 10 with its own IP address. Thus, the apparatus 10 may be positioned on the Internet and can be polled and controlled from remote locations.

It is also within the scope of the present invention that the sensor cartridge 20 can be removed from the apparatus 10 and placed into a hand-held device (such as that disclosed in The'583 Patent). Alternatively, the apparatus 10 may include a connector for allowing the hand held mouse device disclosed in the The'583 Patent to be connected thereto so as to facilitate manual readings of various color patches 16.

It is also within the scope of the invention that the apparatus 10 can be used as a quality assurance device for printing devices for the proofing market. This will involve printing a"target"sheet 14 with the color image, measuring the target, comparing the target against a standard, and if okay, printing a label by the host computer with the test results that is then attached to the printed image sample. Because the unit is"web enabled", remote proofing applications may also be performed and results may be obtained from quality assurance sites around the world.

In an alternate embodiment, the apparatus 10 may include a"transmission" measurement capability where the paper may be fed over a multi-LED diffusion panel and the sensor cartridge may be used to sense transmission characteristics of the sample.

The USB interface 60 allows the apparatus 10 to be networkable and independently addressable. The USB interface 60 also allows the apparatus to act as a hub for other devices (displays, data storage & keyboards). The sensor cartridge 20, itself, may also be a USB device that is visible and addressable by the host computer or by other devices over a network. Thus, the USB sensor cartridge 20 may be"hot-swappable"between the apparatus 10 and a hand-held USB cradle.

Having described the invention by reference to its preferred embodiments, it will be apparent to those of ordinary skill that changes can be made to the present invention without departing from the scope of the invention as defined by the following claims: What is claimed is: