JP2007026238A - Method for shading correction and device for shading correction - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for shading correction and device for shading correction with precise performance by repressing smear effect without using an expensive ND filter. <P>SOLUTION: A linear CCD comprises a photosensitive part in an array format to store electric charges by receiving light from a light source, and a transferring part for transferring the signal charges stored in the photosensitive part to an external circuit. The method for shading correction corrects light intensity of the light source and corrects the output signal based on the output signal of the linear CCD when the light source emits light in a pulse fashion, wherein the light source emits pulse light in a predetermined interval around the shift timing for shifting the electric charges stored in the photosensitive part to the transferring part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a linear CCD configured to include an array-like photosensitive portion that receives light from a light source and accumulates charges, and a transfer portion that forwards and outputs signal charges accumulated in the photosensitive portion to an external circuit. On the other hand, the present invention relates to a shading correction method and a shading correction device for correcting the light quantity of the light source or the output signal based on the output signal of the linear CCD when the light source emits pulses.

  An array-shaped photosensitive unit that receives light from a light source that has passed through a photographic film original and stores signal charges, and a transfer unit that transfers and outputs the signal charges stored in the photosensitive unit to an external circuit. In a film scanner in which a linear CCD is installed, an ND filter is mounted as a reference document between the light source and the optical path of the linear CCD in the initial stage of use of the apparatus in order to correct the light quantity of the light source and the sensitivity variation of the photosensitive portion. Setup work such as shading correction is performed based on the input value to the filter. On the other hand, in a scanner that receives reflected light from a document, shading correction is performed based on data read from a standard white document.

However, in order to perform accurate shading correction with an original transmission type film scanner, it is necessary to use a very expensive ND filter having no density unevenness, and a mechanism for setting the ND filter in a film scanner. There is a disadvantage that the manufacturing cost of the entire apparatus increases.
JP-A-8-271966

  Recently, as a light source of a film scanner, a plurality of LED arrays that output light in different wavelength regions, for example, a combination of red (R), green (G), and blue (B) LED arrays has been proposed. However, when such an LED array is used as a light source, the amount of light is reduced by lighting in a pulse form for a time shorter than the normal exposure time T of one line of the linear CCD, for example, 0.1 × T time. The possibility of performing the setup work without using the ND filter is being studied.

  However, simply limiting the light emission time of the light source has a problem that accurate shading correction cannot be performed under the influence of so-called smear that accumulates noise charges due to the influence of the amount of light leaking into the transfer section.

  That is, as shown in FIGS. 6 and 7, the signal charge accumulated in the photosensitive portion is shifted to the transfer portion by the shift pulse signal (SH), and the transfer portion charge effective timing at which the effective signal charge is present in the transfer portion exists. When the light source LED is turned on, a value larger than the value of the signal charge previously transferred and output by the smear generated at that timing is output, and the transfer unit container effective timing in which there is an empty area generated after the transfer output When the light source LED is turned on, the noise charge due to smear is added to the signal charge shifted from the photosensitive portion next time due to the smear generated at that timing, and in any case, it is affected by smear. Output that is not affected by smear and smear is mixed in the output of one line, and accurate shading based on such output From making positive there is a problem that it is difficult.

  An object of the present invention is to provide a shading correction method and a shading correction device that can be performed accurately while suppressing the effect of smear without using an expensive ND filter in view of the above-described conventional problems.

  In order to achieve the above object, the first characteristic configuration of the shading correction method according to the present invention is an array for receiving light from a light source and accumulating electric charges as described in claim 1 of the claims. Output of the linear CCD when the light source is caused to emit light with respect to a linear CCD configured to include a photosensor and a transfer unit that transfers and outputs signal charges accumulated in the photosensor to an external circuit A shading correction method for correcting the light amount of the light source or the output signal based on a signal, wherein the light source is pulsed at a predetermined time before and after a shift timing for shifting the charge accumulated in the photosensitive portion to the transfer portion. It is in the point to make it emit light.

  According to the above-described configuration, the sum of the signal charge accumulated in the photosensitive portion immediately after the previous shift timing and the signal charge accumulated in the photosensitive portion immediately before the current shift timing, that is, a one-cycle light source that is pulsed. The signal charge corresponding to the amount of light is shifted to the transfer unit, but if the pulse is emitted at the timing described above, the transfer unit is affected by smear due to light emission in the period immediately before the current shift timing and immediately after The effect of smear over the period will appear superimposed. When looking at the output charge output to the external circuit at this time, smears that appear to fluctuate gently at the beginning and end of the effective pixel area where the signal charge has been shifted to the transfer section appear. In this part, the smear effect appears with a relatively flat characteristic. That is, when shading correction is performed, the signal output at both ends is set so as not to be included in the effective pixel region, so that the influence of smear can be suppressed.

  In addition to the first feature configuration described above, the second feature configuration includes a plurality of LED arrays that output light in different wavelength regions, in addition to the first feature configuration described above. The linear CCD is configured to include a plurality of arrayed photosensitive portions that individually receive light in a wavelength region corresponding to a light source, and the LED array simultaneously emits pulses.

  When using multiple LED arrays with different output wavelength regions as the light source, it is necessary to correct shading for each LED array with different wavelength regions, but when emitting light individually by pulsing each LED array simultaneously. In comparison, the correction process can be performed in an extremely short time.

  In the third feature configuration, as described in claim 3, in addition to the first or second feature configuration described above, the photosensitive portion receives light from a light source that has passed through the document and accumulates charges. This is applied to a linear CCD installed in a film scanner.

  That is, the shading correction method according to the present invention is suitable for a film scanner.

  The characteristic configuration of the shading correction apparatus according to the present invention is as described in claim 4, wherein an array-like photosensitive portion that receives light from a light source and accumulates charges, and signal charges accumulated in the photosensitive portion are externally transmitted. Shading correction for correcting the light amount of the light source or the output signal based on the output signal of the linear CCD when the light source is pulsed with respect to a linear CCD configured to include a transfer unit that transfers and outputs to the circuit A light emission control unit for causing the light source to emit light at a predetermined time before and after a shift timing for shifting the charge accumulated in the photosensitive portion to the transfer unit, and an output signal at the time of the pulse light emission. A shading correction unit that corrects the light amount of the light source or the output signal is provided.

  As described above, according to the present invention, it is possible to provide a shading correction method and a shading correction apparatus that can perform smearing with high accuracy without using an expensive ND filter.

  An embodiment of a photographic processing apparatus provided with a film scanner incorporating a shading correction apparatus according to the present invention will be described below. As shown in FIGS. 1 and 2, the photographic processing apparatus generates and edits a photographic printer A that performs exposure and development processing on the supplied photographic paper P and outputs it, and print data that is processed by the photographic printer A. In addition, an operation unit B for controlling the photographic printer A is provided.

  The photographic printer A includes two photographic paper magazines 10 that accommodate the photographic paper P wound in a roll shape, and a cutter 11 that cuts the photographic paper P drawn and conveyed from the photographic paper magazine 10 into a predetermined print size. , An exposure unit 12 containing a print head for exposing the cut photographic paper P, a development processing unit 13 having a plurality of development processing tanks for developing the exposed photographic paper P, and dried after the development processing A sorter having a plurality of trays 15a on which the photographic paper P, that is, photographic prints transported in units of orders discharged to the transverse feed conveyor 14, that is, photographic prints, is disposed. 15 and configured so that each tray 15a is sorted in units of orders.

  The exposure unit 12 emits light beams of three colors of red (R), green (G), and blue (B) in synchronization with the conveyance speed for the photographic paper P conveyed in the sub-scanning direction at a predetermined speed. Are arranged in the main scanning direction, and the light flux output from the print head is modulated and controlled based on the print data sent from the operation unit B. The print head can employ various methods such as a laser beam method, a fluorescent beam method, a liquid crystal shutter method, and a DMD method. In this embodiment, the laser beam method is employed.

  The operation unit B includes a film scanner 2 that reads frame images recorded on the photographic film F as digital data, a general-purpose computer 3 in which a predetermined application program is installed, and a monitor 30 connected to the computer 3. An operation input unit 31 including a keyboard and a mouse, a colorimeter 4 and the like are provided.

  The image data of the frame image read by the film scanner 2 is input to the image memory of the computer 3 via the image input board 33 and displayed on the monitor 30. An operator operating the photo processing apparatus operates the operation input unit 31 while visually observing an image displayed on the monitor 30 to perform a predetermined image processing operation or the like, whereby the computer 3 causes the photo printer A to operate. The final print data to be output is generated. The colorimeter 4 is used for daily setup work described later, and measures the density of the color patch of the test print output from the photographic printer A.

  The computer 3 further includes a media reader 3a for acquiring image data from a storage medium such as a smart media or a compact flash (registered trademark) in which images taken by a digital camera are stored, and the film scanner 2 and the media An image data input unit 32 is configured by the reader 3a.

  The film scanner 2 includes a film transport unit 23, an illumination optical system 22 disposed above the film transport unit 23, an imaging optical system 27 disposed below the film transport unit 23, and an imaging optical system. 27 is configured to include a linear CCD 26 arranged at the in-focus position, and the linear CCD 26 irradiates the light beam from the illumination optical system 22 to the film F conveyed at a constant speed through the slit 24, thereby generating a frame image by the linear CCD 26. It is configured to be read.

  The illumination optical system 22 uses red (R), green (G), and blue (B) LED arrays 20R, 20G, and 20B that output light in different wavelength regions from each other, and outputs light from them in common. The light source 20 is composed of mirrors M1 and M2 guided to the optical axis, and a lens 21. The light output from the red (R) LED array 20R is formed into parallel light by the lens 21 via the mirror M1 that transmits the red component and the mirror M2 that reflects the red component, and is applied to the slit 24, and then green (G The light output from the LED array 20G is formed into parallel light by the lens 21 via the mirror M2 that transmits the green component, and is irradiated to the slit 24. The light output from the blue (B) LED array 20B The light is formed into parallel light by the lens 21 via the mirror M1 that reflects the blue component and the mirror M2 that reflects the blue component, and is applied to the slit 24.

  The imaging optical system 27 includes a condensing lens 25 that condenses the light flux in each wavelength range that has passed through the film F from the gap of the slit 24, and a reflection mirror 27 that reflects the light toward the linear CCD 26, and is linear. The image data read by the CCD 26 is taken into the memory of the computer 3 through the image input board 33 described above.

  The photographic printer A is used for characteristic evaluation because there is a possibility that the coloring degree and density of the finished print may fluctuate even with photographic paper having the same characteristics due to variations in the active state of the developing processing liquid and fluctuations in the amount of exposure light. A plurality of test patches with different densities of red, green, and blue are printed out based on the image data, and the reflection density of each test patch is measured by the colorimeter 4, and each measured value is a target value. A set-up operation for calculating and deriving correction data for correcting image data and storing it in a storage unit provided in the apparatus is performed every day.

  Similarly, the film scanner 2 detects the output light amount of the light source 20 and the pixels read by the linear CCD 26 when the power is turned on in order to cope with the fluctuation of the film read image due to the light amount variation of the light source 20 and the pixel sensitivity variation of the linear CCD 26. Shading correction is performed to correct the data.

  Hereinafter, the shading correction will be described. As shown in FIG. 3, the linear CCD 26 receives light from the LED arrays of red (R), green (G), and blue (B) described above and accumulates electric charges, thereby storing red (R) and green (G ), Blue (B) array-like photosensitive portions R1, G1, and B1, and a transfer portion that includes an analog shift register that transfers and outputs signal charges accumulated in the photosensitive portions R1, G1, and B1 to an external circuit. R3, G3, and B3, and transfer electrodes R2, G2, and B2 that apply a shift pulse that shifts signal charges from the photosensitive units R1, G1, and B1 to the transfer units R3, G3, and B3.

  A plurality of photodiodes constituting one pixel are linearly arranged in each of the photosensitive portions R1, G1, and B1, and any one of red (R), green (G), and blue (B) is arranged in the light incident portion. A filter and a microlens that selectively transmit light of the wavelength component are disposed. The red component signal charge is accumulated by the photosensitive portion R1 in which the filter that transmits the red (R) component is disposed, and the green component signal charge is accumulated by the photosensitive portion G1 in which the filter that transmits the green (G) component is disposed. Then, the signal charge of the blue component is accumulated by the photosensitive portion B1 in which the filter that transmits the blue (B) component is disposed, and thereby the signal charge corresponding to the color image formed on the photographic film is accumulated. Each of the photosensitive portions R1, G1, and B1 is shielded from light by a predetermined number of pixels on both ends, and is configured to detect optical black.

  The signal charges accumulated in the photosensitive portions R1, G1, and B1 are transferred to the transfer electrodes R2, G2, and B2 at the timing when the shift pulse SH output from the shift pulse generator 26b is applied to the transfer electrodes R2, G2, and B2. The signal is transferred to B3, and further shifted in order for each pixel in synchronization with the application of the two-phase transfer pulses φ1 and φ2 output from the transfer pulse generator 26a to the transfer units R3, G3, and B3, and converted into voltages. After that, output signals OS (R), OS (G), and OS (B) are output from the output buffers 26R, 26G, and 26B. For example, 1 msec. The shift pulse SH is 1 msec. So that signal charges are taken out at intervals. Accumulated charges input at intervals and shifted from the photosensitive portions R1, G1, B1 to the transfer portions R3, G3, B3 are output by transfer pulses having a frequency corresponding to the number of constituent pixels applied between the preceding and following shift pulses. It is done. The shift pulse generation unit 26b and the transfer pulse generation unit 26a are configured with a known clock generation circuit.

  In the output signals OS (R), OS (G), OS (B), the output corresponding to the color image on the photographic film has a variation in the amount of light in the arrangement direction of each LED array and the photosensitive portions R1, G1, B1. Since it is output in a state where sensitivity variations are superimposed, shading correction processing is performed in order to initially correct these variations and obtain flat output characteristics.

Specifically, first, based on the respective outputs of red (R), green (G), and blue (B) from the linear CCD obtained by causing each LED array to emit light simultaneously with a preset reference light amount, The drive current of each LED array is adjusted so that the pixel data showing the maximum value for each color shows a preset value, and then the linear CCD output _DBK when the light source is off and the linear when the light source is on The CCD output _DWH is obtained a plurality of times.

The thus obtained driving current value, D _WH, D _BK is stored in the memory provided in the memory or the controller 3 provided in the image input board 33, when reading the actual photographic film thereafter, it is currently stored The light source is driven with the drive current value, and the output D _IN read at that time is converted into D _OUT based on [Equation 1]. The sensitivity variation of G1 and B1 is compensated.

  The reference light quantity described above is set to a time shorter than the exposure time T (usually 1.0 msec.) Of one line of the linear CCD at the time of reading a normal photographic film, specifically 0.1 × T time, In this way, the light amount is reduced by turning on in pulses, so that the incident light amount is comparable to the read value for the film base.

  However, by simply limiting the light emission time of the light source, accurate shading correction cannot be performed under the influence of so-called smear that accumulates noise charges due to the influence of the amount of light leaking into the transfer section. That is, as shown in FIGS. 6 and 7, the signal charge accumulated in the photosensitive portion is shifted to the transfer portion by the shift pulse signal (SH), and the transfer portion charge effective timing at which the effective signal charge is present in the transfer portion exists. When the light source LED is turned on, a value larger than the value of the signal charge previously transferred and output by the smear generated at that timing is output, and the transfer unit container effective timing in which there is an empty area generated after the transfer output When the light source LED is turned on, the noise charge due to smear is added to the signal charge shifted from the photosensitive portion next time due to the smear generated at that timing, and in any case, it is affected by smear. Output that is not affected by smear and smear is mixed in the output of one line, and accurate shading based on such output It is difficult to carry out the positive.

  Therefore, as shown in FIG. 4, the LED array 20R, which is a light source, at a predetermined time before and after the shift timing for shifting the charges accumulated in the photosensitive portions R1, G1, and B1 to the transfer portions R3, B3, and G3. 20G and 20B are configured to emit pulses for 0.1 × T time. In other words, the transfer unit container effective timing in which there is an empty region generated after the transfer output immediately before the transfer unit charge effective timing at which the shift pulse SH is output and the effective signal charges are shifted to the transfer units R3, B3, G3. The relatively stable output is obtained in which the smear generated in the transfer units R3, B3, and G3 becomes flat at the center of the transfer units R3, B3, and G3 and decreases at both ends. Be able to.

  More specifically, the sum of the signal charges accumulated in the photosensitive portions R1, G1, B1 immediately after the previous shift timing and the signal charges accumulated in the photosensitive portions R1, G1, B1 immediately before the current shift timing. That is, the signal charge corresponding to the light amount of the light source in one cycle that is pulsed is shifted to the transfer units R3, B3, and G3. However, as shown in FIG. In this case, the effect of smear due to light emission in the period immediately before the current shift timing and the effect of smear in the immediately following period appear superimposed on the transfer units R3, B3, and G3. When looking at the output charge output to the external circuit at this time, smears that appear to fluctuate gently at the beginning and end of the effective pixel area where the signal charge has been shifted to the transfer section appear. In this part, the effect of smear appears with a relatively flat characteristic. Therefore, by setting so that the signal outputs at both ends are not included in the effective pixel region, the influence of smear can be suppressed. In addition, an appropriate film image input can be performed by applying a known smear correction process to a signal output in which the influence of such smear appears uniformly.

  According to such a shading correction method, it is possible to drive and control the linear CCD without changing the same timing as when reading a normal photographic film, that is, the period of the shift pulse and the transfer pulse.

  A processing unit that performs the above-described shading correction processing, that is, a shading correction device, can be provided in the above-described image input board 33 or the controller 3, and charges accumulated in the photosensitive units R1, G1, and B1 are transferred to the transfer unit R3. , B3, G3, a light emission control unit for causing the light source to emit light at a predetermined time before and after the shift timing, and shading correction for correcting the light amount of the light source or the output signal based on the output signal at the time of the pulse light emission. It can comprise by a part.

  In the above-described embodiment, the signal charge is transferred by the two-phase transfer clock pulses of φ1 and φ2 generated by the transfer pulse generation unit. However, the transfer clock depends on the configuration of the analog shift register. In addition to the two-phase drive type, the present invention can also be applied to a four-phase drive type.

  In the above-described embodiment, the linear CCDs correspond to the red (R), green (G), and blue (B) photosensitive portions R1, G1, B1, transfer electrodes R2, B2, G2, and transfer portions R3, B3, G3. However, the configuration of the linear CCD is not limited to this, and red (R), green (G), and blue (B) for each pixel in the arrangement direction of the photosensitive portions. The present invention can be applied to linear CCDs having different configurations, such as a one-line linear CCD provided with a filter that transmits light of each wavelength.

External view of the photo processing device Block diagram of photo processing equipment Illustration of linear CCD Illustration of the light source lighting sequence during shading correction Illustration of accumulated charge during shading correction Explanatory diagram of light source lighting sequence during shading correction according to the prior art Explanatory diagram of accumulated charge during shading correction by conventional technology

Explanation of symbols

26: Linear CCD
26a: transfer pulse generation unit 27b: shift pulse generation unit R1, B1, G1: photosensitive unit R2, G2, B2: transfer electrodes R3, G3, B3: transfer unit

Claims (4)

With respect to a linear CCD configured to include an array-shaped photosensitive unit that receives light from a light source and accumulates charges, and a transfer unit that transfers and outputs signal charges accumulated in the photosensitive unit to an external circuit. A shading correction method for correcting a light amount of the light source or the output signal based on an output signal of the linear CCD when the light source is pulsed,
A shading correction method for causing the light source to emit light at a predetermined time before and after a shift timing for shifting the charge accumulated in the photosensitive portion to the transfer portion.   The light source includes a plurality of LED arrays that output light in different wavelength regions, and the linear CCD includes a plurality of arrayed photosensitive units that individually receive light in the wavelength regions corresponding to the light sources. The shading correction method according to claim 1, wherein the LED array emits pulses simultaneously.   3. The shading correction method according to claim 1, wherein the photosensitive unit is applied to a linear CCD installed in a film scanner that receives light from a light source that has passed through a document and accumulates charges. With respect to a linear CCD configured to include an array-shaped photosensitive unit that receives light from a light source and accumulates charges, and a transfer unit that transfers and outputs signal charges accumulated in the photosensitive unit to an external circuit. A shading correction device that corrects the light amount of the light source or the output signal based on an output signal of the linear CCD when the light source emits pulses,
A light emission control unit that causes the light source to emit light at a predetermined time before and after a shift timing for shifting the charge accumulated in the photosensitive unit to the transfer unit; A shading correction apparatus comprising a shading correction unit for correcting the output signal.