Optics: measuring and testing – By configuration comparison – With photosensitive film or plate
Reexamination Certificate
1999-12-16
2001-04-10
Pham, Hoa Q. (Department: 2877)
Optics: measuring and testing
By configuration comparison
With photosensitive film or plate
C250S559020, C250S559260, C396S569000, C396S570000
Reexamination Certificate
active
06215553
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to the measurement of the width of a sheet bearing an image. In particular, the invention relates to width measurement of a sheet of photographic material that (i) has an image-bearing portion, and (ii) has a non-image-bearing portion that is of substantially uniform optical density across substantially its entire width.
Although the invention finds particular application in respect of a sheet of material having black and white, high contrast images, for example of the kind used in graphic arts, it is generally applicable to sheet material bearing any kind of image including colour images, including but not limited to those formed on silver halide film and paper, and to images formed using polymers, dyes, inks, or toners.
The term “sheet” is to be understood as encompassing a substantially two-dimensional shape not only of discrete square or other low aspect ratio, but also of elongate, generally rectilinear, shape, thus including, for example, a web or a roll, of photographic material for example.
BACKGROUND OF THE INVENTION
For convenience, the invention will be described with reference to a sheet of photographic material, but it is to be understood that the method and apparatus is also applicable to the measurement of the width of other material as described above.
For the accurate control of a photographic processing machine, it is necessary to replenish the processing baths to compensate for consumption of the chemicals therein as the photographic material is processed, and thus to maintain the chemical activity of the processing solutions. Improvements in the formulations of the processing solutions, and a desire to reduce the volume of liquid effluent which is produced, have lead in recent years to a gradual reduction in the rate and amount of replenishment required. This, in turn, has lead to a requirement for increasingly accurate control of the replenishment process. For black and white materials, the volume of replenishment solution required, for the developer and the fixer stages of the processing is a function of the area of the material processed and of the amount of developed image on the material. In many graphic arts, that is to say high-contrast black-and-white, processing machines, where a variety of material widths may be used, the area is usually approximately determined by measuring the sheet width and the length, for example by means of microswitches extending across the width of the entrance to the processor that are activated by the passing material. The length is determined by the time for which the switches are activated multiplied by the transport speed of the processor. The width is determined by the number of microswitches that are activated. For example, if there are four microswitches equi-spaced across the entrance to the processor and three are activated, then the width of the material relative to the maximum possible width must be between 40% and 80%, and the width is stated as 60%±20%.
Another method of obtaining the width and length, and thus the image area, is to have the image exposing apparatus, for example, an image-setter, transmit this information to the processor, as is the case, for example with the Linotype Hell Herkules PRO/Advantage™ imagesetting system. The processor is then able to use the information from the image-setter to enable accurate replenishment and thus to maintain good process control. In the case of the Advantage™ processor, errors in the delivery of replenishment per unit area of film processed were reduced to about 5% of the volume delivered in order to maintain stability at the very low replenishment rates used.
U.S. Pat. No. 4,506,969 (Pako Corporation) discloses a film width and transmittance scanner system of a graphic arts film processor in which the transmittance of light through the film is measured along a line or set of parallel lines positioned at a skew angle with respect to the direction of film travel. Switches are employed to note passage of the leading and trailing edge of the film through the scanner. The scanner may employ a single light source and a single detector, each of which extends across the width of the film, but there is also disclosed use of a larger number of detectors extending sequentially across the width of the film in order to reduce the path length which the scanner adds to the processor. The scanner produces signals that are used in the control of a replenishment system of the processor.
U.S. Pat. No. 3,554,109 (Logetronics Inc) discloses an image monitoring and control system for determining the optical densities developed in sheets of image-bearing photosensitive material, for controlling the feeding of replenishment chemicals to a film processor. The system includes a scanner having twelve light communicating stations for sequentially receiving light from a corresponding plurality of sources that has passed through successive portions across the width of a developed film.
PROBLEM TO BE SOLVED BY THE INVENTION
To improve the accuracy of the microswitch measuring method to 5% of the full width of the processor, it would be necessary to use nineteen microswitches across the processor entrance. This would not only be very expensive, but would also reduce reliability due to the many moving parts.
The method of forwarding information from the exposing apparatus to the processing apparatus is only effective when the processor is linked in some way to the exposing device, for example by being on-line therewith, and where: the exposing device actually measures the width and exposed image area; the processor is equipped with the correct data link to receive the information from the exposing device; and the processor has the algorithms necessary to use the information to convert it into a control signal for the processing bath replenishment systems. For off-line systems where the processor is not linked to an associated exposing device, material to be processed may have come from one of a number of different exposing devices, may come in various widths and lengths, and may be of one of several different film types. Furthermore, the sheet material may be introduced into the processor anywhere across its entrance, that is to say, it could be put down the left- or right-hand side or down the centre of the processor.
It is one object of the present invention to provide for inexpensive yet accurate measurement of the width of sheet material.
It is another object of the present invention to provide for determination of the exposed area of photographic material during processing.
SUMMARY OF THE INVENTION
In accordance with one aspect of the present invention, there is provided a method of measuring the width of a sheet of material that (i) has an image-bearing portion, and (ii) has a non-image-bearing portion that is of substantially uniform optical density across substantially the entire width of the sheet, wherein:
the sheet is guided longitudinally through a channel;
light from an elongate source is directed into the channel substantially perpendicularly to the direction of movement of the sheet;
said light is received (i) by an elongate main sensor arrangement whose length is greater than the width of the sheet, and whose response to the light is substantially uniform across the width of the sheet; and (ii) by an elongate subsidiary sensor arrangement whose length is less than 90% of the width of the sheet;
wherein the transmittance, or reflectance, of the non-image-bearing portion of the sheet is determined from the difference of an output signal of the subsidiary sensor arrangement when (i) the sheet is in the channel and the light received is from the non-image-bearing portion, and (ii) the light received thereby is in the absence of the sheet in the channel; and
wherein the width of the sheet is determined from the measured transmittance, or reflectance, and from the difference of the output signal of the main sensor arrangement when (i) the sheet is in the channel and the light received is from the non-image-bearing portion, and (
Gowans Bruce S.
Rider Christopher B.
Skye David A.
Eastman Kodak Company
Pham Hoa Q.
Pincelli Frank
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