Image reading apparatus

The present invention provides an image reading apparatus capable of reading images with a sufficiently wide dynamic range. An image reading apparatus of this invention has a light source, a reading section which generates image data based on light obtained from an original illuminated with light from the light source, a first level changing section which changes a light receiving level in the reading section in a first manner, a second level changing section which changes the light receiving level in a second manner different from the first manner, a control section in which plural light receiving levels are generated by synergistically changing a light receiving level, and a combining section which combines plural image data obtained by reading an image of an original at plural light receiving levels.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an image reading apparatus which reads original images and generates image data representing the original images.

2. Description of the Related Art

Image reading apparatuses which read an original image by illuminating it with light and collecting the light reflected from or transmitted through it have conventionally been in wide use. A photographic digital printer to print out images recorded on a photographic film, for example, has a film scanner which reads images recorded on a photographic film by receiving light applied to and transmitted through the photographic film using image pickup devices such as CCDs. The resultant images read by the film scanner are sent to a printer incorporated in the photographic digital printer and then printed out.

Generally, the range of density (hereafter referred to as a dynamic range) that can be read by an image pickup device is narrower than the dynamic range that can be recorded on a photographic film. Therefore, the problem is that when image data generated by scanning an original. image using a film scanner is printed as it is, the printed image shows a low density contrast as compared with an image printed by directly exposing a photographic image recorded on a photographic film. In terms of an image pickup device, the smaller the device is, the narrower its dynamic range is. However, since the price of an image pickup device increases with its size, there is a demand for using smaller ones to reduce the cost of digital photographic printer.

As a way to solve the above problems, a method of image input designed to make an image with a wide dynamic range available is disclosed in Japanese Patent Laid-Open No. 2003-5545. In the disclosed method, electric charge accumulation times are changed in the image pickup device, image data are generated for an image under the plural charge accumulation conditions, and image data to be used is selected from the plural image data for every pixel. In this way, it is possible to obtain an image with a wide dynamic range using small image pickup devices.

When the method disclosed in Japanese Patent Laid-Open No. 2003-5545 is applied, the dynamic range of the image to be finally obtained can be widened by increasing the difference between electric charge accumulation times in the plural charge accumulation conditions. The ratio between the electric charge accumulation times should preferably be at least on the order of 1:4, and more preferably 1:16 to generate image data for each charge accumulation condition.

However, to achieve the preferable ratio as mentioned above, one of the electric charge accumulation times must be set very long. Setting a very long electric charge accumulation time results in more time required to read an image and, eventually, lower productivity. Also, generating an image by using image data selected from plural image data may cause shifting in color gradation, making the generated image look unnatural in its color-gradated parts.

Besides the method disclosed in Japanese Patent Laid-Open No. 2003-5545, there is also a method in which the amount of light emitted from a light source is changed by controlling pulse-width modulation to enable plural image data to be generated using different amounts of light. Similarly as described above, image data to be used is selected from the plural image data for every pixel. Since the adjustability of pulse-width modulation is limited, however, it will be difficult by this method to achieve an ideal ratio (about 1:16) of light.

The present invention has been made in view of the above circumstances and provides an image reading apparatus capable of reading images with a sufficiently wide dynamic range.

SUMMARY OF THE INVENTION

The image reading apparatus according to the invention includes:

a light source which emits light to illuminate an original,

a reading section which reads an image of the original by receiving light coming from the original illuminated with light emitted from the light source and generates image data representing the image,

a first level changing section which changes a light receiving level in the reading section in a first manner used in an imaging system from the light source to the reading section,

a second level changing section which changes the light receiving level in a second manner different from the first manner and used in the imaging system from the light source to the reading section,

a control section in which plural light receiving levels are generated by having the light receiving level changed synergistically by the first and the second level changing sections and which causes the reading section to read the image at each of the plural light receiving levels, and

a combining section which combines plural image data obtained by reading the image at each of the plural light receiving levels.

The first and the second manners each refer to a method of changing a light receiving level. Such a method may be, for example, adjusting an electric current or voltage, or pulse-width modulation for the light source, adjusting a lens diaphragm, or inserting an ND filter or other devices for controlling light transmission factor.

To obtain an image with a sufficient dynamic range, it is preferable to combine plural image data obtained at plural light receiving levels with the ratio between the plural light receiving levels being about 1:16. Achieving such a ratio between plural light receiving levels by a single method, for example, by reading an image using different electric charge accumulation times is difficult. Even if it can be done, such a method increases the time required for image reading and leads to lower productivity.

In the image reading apparatus according to the invention, plural light receiving levels are generated by having a light receiving level synergistically changed by the first and the second level changing sections and plural image data obtained by reading an image at each of the plural light receiving levels are combined into one set of data. An ideal ratio between light receiving levels of 1:16 can be achieved with ease, for example, by combined use of a first manner in which a ratio of 1:4 between light receiving levels can be achieved by adjusting a lens diaphragm and a second manner in which a ratio of 1:4 between light receiving levels can be achieved by adjusting electric charge accumulation times. As compared with generating plural light receiving levels only by controlling electric charge accumulation times, generating plural light receiving levels by the combined use of the first and the second manners allows image reading to be completed faster leading to productivity improvement.

It is preferable that the combining section included in the image reading apparatus according to the invention be capable of giving a predetermined weight to each of plural predefined parts of an image in the same way for plural image data and combining plural weighted image data to generate a new set of image data.

An image with a wide dynamic range free of tone jumps can be obtained by combining plural image data with a predetermined weight given to each of plural predefined parts of each set of image data.

In the image reading apparatus according to the invention, it is also preferable that the “each” of plural predefined parts of an image represent a minimum unit of the reading resolution of the reading section.

When combining plural image data with a predetermined weight given to each pixel which is a minimum unit of the reading resolution of the reading section, finer dynamic range and gradation adjustments are enabled so that higher-quality images can be obtained.

In the image reading apparatus according to the invention, the value of each predetermined weight is preferred to be dependent on an image data value.

When each predetermined weight is controlled according to the image data value, it is possible to reliably prevent color gradation from shifting so that smoothly graded images free of tone jumps can be obtained.

The image reading apparatus according to the invention is preferred to include an original feeding section which sequentially feeds plural originals to a reading position in the reading section where an image is read and which keeps still each original while an image thereof is being read in the reading position. Furthermore, while an original is kept still in the reading position by the original feeding section, the control section included in the image reading apparatus is preferred to generate plural light receiving levels.

If an image is transported each time when it is to be read in the first manner and when it is to be read in the second manner, a delicate image positioning error may occur to result in shifted image data reflecting the image positioning error. In the above preferred embodiment of the image reading apparatus according to the invention, each image is read in the first and the second manners while being kept still so that plural image data can be generated with high positional accuracy. As a result, high-quality images without blurring due to positional errors can be obtained.

Furthermore, it is preferable:

that the image reading apparatus according to the invention includes an optical path splitting section which splits an optical path formed by the light coming from the original image into plural paths,

that the reading section includes plural reading elements which read an image of the same original respectively via the plural paths generated by splitting the optical path by the optical path splitting section,

that the first level changing section unequalizes the plural light receiving levels at the plural reading elements,

that the second level changing section also unequalizes the plural light receiving levels at the plural reading elements, and

that the control section causes the plural light receiving levels to be generated simultaneously for the plural reading elements by the first and the second level changing sections and causes the plural reading elements to read the image of the same original simultaneously at each of the plural light receiving levels.

By reading an image with plural reading elements at plural light receiving levels simultaneously rather than reading it at each of the plural light receiving levels sequentially, the reading operation can be made faster to eventually improve productivity.

The invention can provide an image reading apparatus capable of reading images with a sufficiently wide dynamic range.

DETAILED DESCRIPTION OF THE INVENTION

In the following, preferred embodiments of the invention will be described in detail.

FIG. 1is a perspective view showing an external appearance of a digital photographic printer which prints photographic images based on digital image data according to an embodiment of the image reading apparatus of the invention.

A digital photographic printer10obtains photographic image data by optically reading photographic images recorded on a photographic film. It can also read out photographic image data taken and recorded on a small recording medium, for example, by a digital camera, correct the photographic image data as required, and make photographic prints of the corrected image data.

The digital photographic printer10includes image input equipment100and image output equipment200according to an embodiment of the invention.

The image input equipment100has a scanner section110which photoelectrically reads plural photographic images recorded on a developed film sequentially frame by frame and an image correction section120which corrects the photographic image data obtained by the scanner section110. The image correction section120includes a CRT display section130, a keyboard140, a mouse150, and a circuit section160. The circuit section160has a small storage medium insertion slot (not shown) and a floppy disk insertion slot (not shown). Sections included in the image input equipment100will be described in detail later.

The image output equipment200includes a laser printer section210which exposes images on a photographic paper by scanning a laser light beam modulated based on image data obtained by the image input equipment100and a processor section220which makes photographic prints by developing the photographic paper exposed in the laser printer section210. The internal structure of the image output equipment200will also be described later.

In the following, the structure of the scanner section110included in the image input equipment100and a procedure for reading photographic images recorded on a photographic film will be described.

FIG. 2is a view showing the structure of the scanner section included in the image input equipment.

In the scanner section, a developed photographic film20is set on a film carrier119and fed in the direction of arrow A causing photographic images recorded on the photographic film20to be rapidly and coarsely read frame by frame (this reading operation will hereafter be referred to as prescanning). The film carrier119constitutes an example of an original feeding section included in the image reading apparatus according to the invention.

The scanner section110has a light source unit111which includes an LED light source112A, a diffusion box112B and a heat regulator112C. The light source unit111constitutes an example of a light source included in the image reading apparatus according to the invention. The light source unit111sequentially emits red, green, blue, and infrared light beams to illuminate via the diffusion box112B the photographic film20from below as shown inFIG. 2. Each of the light beams transmitted through the photographic film20reaches a CCD115and a CCD board116via an image pickup lens113and an ND filter114which adjusts the light amount of each light beam. The CCD115and the CCD board116combined constitute an example of a scanning section included in the image reading apparatus according to the invention. The image pickup lens113is driven by an image pickup lens driving section (not shown) so that its focal length is adjusted and each image according to a ratio dependent on the adjusted focal length of the image pickup lens113is formed on the sensor surface of the CCD115. When an image recorded on the photographic film20is formed on the CCD115, a photographic image signal representing the image is generated. The photographic image signal is converted into digital photographic image data by an A/D converter118and sent to the image correction section120.

The CCD115is an area sensor which reads the photographic film20frame by frame. In the present embodiment, when the light source111emits a red light beam, a frame of image is read with the red light beam. When the light source111next emits a green light beam, the same frame of image is read with the green light beam. In a similar fashion, when a blue light beam is emitted, the same frame of image is read with the blue light beam and when an infrared light beam is emitted, the same frame of image is read with the infrared light beam. The image data obtained by reading the frame of image with the infrared light beam does not represent the photographic image data recorded on the frame of the photographic film20. What is obtained with the infrared light beam is scratch data representing scratches on the frame of the photographic film20. The photographic image data and the scratch data obtained are sent to the image correction section120shown inFIG. 1. In the image correction section120, various corrections are applied to the photographic image data to correct flaws due to scratches on the photographic film20and generate photographic image data representing a beautiful-looking image. When the frame of image has been read with each of the four light beams, the photographic film20is fed in the direction of arrow A to have the next frame of image read.

When an image is prescanned, only every other light-sensitive element included in the CCD115is used so that a coarse image is obtained. The photographic image generated by prescanning and a prepared condition setting screen are displayed in the CRT display section130shown inFIG. 1. By checking the photographic image and the condition setting screen displayed in the CRT display section130, the operator can specify conditions for image acquisition such as a print size and a resolution. When the required conditions for image acquisition are specified, the focal length of the image pickup lens113is adjusted, as required, depending on the specified print size. The photographic film20is next fed in the direction of arrow B and the photographic image is read by the CCD115using as many light-sensitive elements as required according to the specified print size (or at a specified resolution) (image reading in this manner will hereafter be referred to as fine scanning). A piezoelectric device for position shifting117can shift the image reading position, for example, precisely by ½ pixel. Combining an image generated by reading a photographic image at the initial reading position and another image generated by reading the same photographic image at a shifted reading position makes it possible to obtain an image with a higher resolution than the resolution of the CCD115. The piezoelectric device117determines the amount of shifting the reading position according to the specified resolution. The photographic image signal generated at the CCD115is, as stated previously, converted into digital photographic image data by the A/D converter118and then sent to the image correction section120.

In the following, the structure of the circuit section160included in the image correction section120of the image input equipment100will be described.

FIG. 3is a block diagram of the circuit section included in the image correction section of the image input equipment.

The circuit section160includes a CPU171which executes various programs and performs various types of control, a RAM172which is used as a work area when various programs are executed, a ROM173which stores fixed constants, a control interface174which inputs and outputs control signals required to control different sections included in the image input equipment100, an image interface175through which images are input from the scanner section110shown inFIG. 2, the CRT display section130, the keyboard140and the mouse150shown inFIG. 1, a small recording medium drive162which accesses a small recording medium163, a floppy disk drive164which accesses a floppy disk165, a hark disk176, and an external interface177which undertakes data transmission and reception to and from the image output equipment200shown inFIG. 1, all of which are interconnected via a bus178. The CPU171constitutes an example of a control section and also an example of a combining section both included in the image reading apparatus according to the invention.

In the present embodiment, the control interface174sends control signals to the elements shown inFIG. 2. The elements shown inFIG. 2feed the photographic film20, adjust the LED light source112A and adjust the focal length of the image pickup lens113(adjust the enlargement ratio for image formation) in accordance with the control signals received from the control interface174.

Control signals required to control the CCD115and different sections of the image input equipment100are also output from the control interface174.

Furthermore, various data and conditions for image acquisition specified by the operator are also sent from the control interface174to the CPU171.

The image input equipment100is basically configured as described above.

When reading a photographic image recorded on a photographic film in the image input equipment100shown inFIG. 1, the photographic image is prescanned in the scanner section110, and the photographic image generated by prescanning is input to the circuit section160(seeFIG. 3) via the image interface175to be displayed in the CRT display section130. When the operator specifies conditions for image acquisition such as an enlargement ratio for printing, the relevant information incorporating the specified conditions for image acquisition is sent to the CPU171(seeFIG. 3). The photographic image recorded on the photographic film is also fine-scanned in the scanner section110and the photographic image generated by fine-scanning is then input to the CPU171for various kinds of correction processing. The corrected image output from the CPU171is sent to the image output equipment200to be used as a laser light modulation signal in a laser light exposure process.

When, instead of reading a photographic image recorded on a photographic film in the scanner section110, inputting a photographic image from the small recording medium163, shown inFIG. 3, on which the photographic image, for example, taken by a digital camera is recorded, the photographic image data is input to the circuit section160via the small recording medium drive162and the photographic image is displayed in the CRT display section130shown inFIG. 1. The photographic image data is also sent to the CPU171via the image interface175. When the operator subsequently specifies conditions for image acquisition, the relevant information incorporating the specified conditions for image acquisition is sent to the CPU171for various kinds of correction processing as in the case of reading a photographic image from a photographic film. The corrected image output from the CPU171is sent to the image output equipment200.

Next, the structure of the image output equipment200and a procedure for making photographic prints of photographic images input to the image output equipment200will be described in the following.

FIG. 4is a view showing the internal structure of the image output equipment.

A lengthy unexposed sheet of photographic paper30is wound around inside the image output equipment200passing through various parts of the image output equipment. The photographic paper30being led by its leading edge is guided to pass the laser printer section210and the processor section220. A cutter230then cuts the photographic paper into individual frames to be stacked in a sorter240.

When an image is output from the CPU171included in the image input equipment100and sent to the image output equipment200, it is once stored in an image buffer211included in the laser printer section210.

The laser printer section210includes three laser light sources212R,212G and212B which emit red, green and blue laser light beams, respectively. The laser light sources212R,212G and212B are driven based on the red, green and blue color-separated images stored in the image buffer211and emit laser light beams that are modulated as the laser light sources are driven. These laser light beams are repeatedly polarized by being reflected by a rotary polygonal mirror213and are then reflected by a mirror214to pass through an fθ lens215which adjusts the light spot diameter on the photographic paper30. In an exposure section Ep, the laser light beams repeatedly scan the photographic paper30in the direction of the width of the photographic paper30while the photographic paper30is transported in the direction of arrow C causing the photographic image to be exposed on the photographic paper30.

The photographic paper30having been exposed is transported to the processor section220. In the processor section220, the photographic paper30is transported through a reserver section221in which the photographic paper transport speed is adjusted, a developing bath222in which chromogenic development is performed, a fixing bath223in which bleach fixing is performed, a rinsing bath224in which rinsing is performed, and a drying section225in which drying is performed. The photographic paper30is then cut into individual frames by the cutter230to be stacked in the sorter240as previously described.

The image data generated in the image input equipment100is photographically printed in the image output equipment200as described above.

Through the series of processing as described above, the photographic image recorded on the photographic film20or on the small recording medium163is printed out.

There is a problem, however. Since the dynamic ranges of image pickup devices such as CCDs are narrower than those of photographic films, photographic images printed by conventional digital photographic printers lack in contrast density as compared with photographic images obtained by directly exposing the photographic film20.

FIG. 5is a flowchart showing a series of image reading processing performed to obtain a photographic image having a wide dynamic range. In the following, a series of processing performed in the image input equipment100will be described in detail with reference toFIGS. 2,3and5.

As described above, in the series of processing, each photographic image is prescanned and then fine-scanned.

First, the light source unit111emits a red light beam causing the ND filter114to be inserted in position by an order from the CPU171. In this state, the ND filter114attenuates the red light beam to illuminate the CCD115thereby adjusting the red light receiving level at the CCD115to the LR1level. The ND filter114constitutes an example of a first level adjusting section included in the image reading apparatus according to the invention. In the way stated above, each of the photographic images recorded on the photographic film20is finely read (step S1inFIG. 5).

When a photographic image signal is generated by reading a photographic image recorded on the photographic film20, it is converted into digital photographic image data by the A/D converter118(step S2inFIG. 5). The digital photographic image data is then sent to the CPU171shown inFIG. 3.

The photographic image data sent to the CPU171is subjected to various kinds of correction processing such as pixel-by-pixel sensitivity adjustment correction and shading correction (step S3inFIG. 5). These kinds of corrections have been widely conducted so that they are not further described herein.

The photographic image data coming through the correction processing advances to step S4via a branch point P1to be temporarily stored in the hard disk176shown inFIG. 3.

Next, the light source unit111emits a red light beam again. This time, unlike at the previous time, the ND filter114is moved out of position by an order from the CPU171so as not to block the optical path. Also, by an order from the CPU171, the amount of light emitted from the light source unit111is adjusted by adjusting pulse-width modulation and the red light receiving level at the CCD115is adjusted to the LR2level. The light source unit111constitutes an example of a second level adjusting section included in the image reading apparatus according to the invention. In the present embodiment, the ratio of the light receiving level LR1attained at the previous time to the light receiving level LR2attained this time is adjusted to be 1:16. In this state, the photographic image recorded on the photographic film20is read for the second time (step S1inFIG. 5, for the second time).

The photographic image signal generated by reading the photographic image recorded on the photographic film20is, as at the previous time, converted into digital photographic image data by the A/D converter118(step S2inFIG. 5, for the second time). The digital photographic image data is then sent to the CPU171shown inFIG. 3and is subjected to various kinds of correction processing (step S3inFIG. 5, for the second time).

This time, the photographic image data coming through correction processing advances to step S5via branch point P1without being temporarily stored.

The photographic image data recorded on the hard disk176at the previous time (hereafter referred to as the LR1data being the photographic image data obtained with a light receiving level of LR1) and the photographic image data obtained at this time (hereafter referred to as the LR2data being the photographic image data obtained with a light receiving level of LR2) are subjected to level corrections (step S5inFIG. 5) for level alignment between the two photographic image data. The level corrections have been widely conducted so that they are not further described herein.

The LR1data and the LR2data having been subjected to level corrections next undergo weighting (step S6inFIG. 5).

There are cases in which the signal-to-noise ratio (S/N ratio) of a photographic image signal generated by reading a dark photographic image is too small and the image printed from the image signal is blurry. There are also cases in which reading a bright photographic image results in an excessively large image data value to saturate the image consequently obtained. Therefore, of the LR1data and the LR2data, the LR2data with a large image data value and a large S/N ratio is more reliable when reading a dark photographic image. On the other hand, when reading a bright photographic image, the LR1data with a small image data value that does not saturate the image to be obtained is more reliable.

FIG. 6is a diagram showing the relationship between the value of the LR1data and the weighting factor for the LR1data. When the weighting factor for the LR1data is represented by α, the weighting factor β for the LR2data can be calculated from the following equation:
β=(1−α)

The level—1 represents a threshold value of image data, an image data value smaller than which results in a blurry image. The level—2 represents a threshold value of image data, an image data value larger than which results in a saturated image. Therefore, for a pixel based on the LR1data whose value is smaller than the level—1 value, the weighting factor α with a value close to 0 is applied to the LR1data so that the pixel based on the more reliable LR2data is used. When a pixel is based on the LR1data whose value is greater than the level-2 value, the weighting factor α with a value close to 1 is applied to the LR1data so that the pixel based on the LR1data is used. This is because the pixel based on the LR2data whose value is greater than the LR1data value will result in a completely saturated image to be obtained. Such weighting factors α and β are computed for every pixel.

When the weighting factors α and β to be applied to the LR1and LR2data respectively are determined for a pixel, the LR1and LR2data are added in the CPU171(step S7inFIG. 5). In the CPU171, the following computation is made to generate combined image data:
(α×LR1 data value)+{(1−α)×LR2data value}
The combined image data generated as described above has a dynamic range equal to the combined dynamic range of the LR1and LR2data. Furthermore, the weighting factors α and β determined based on the values of the LR1and LR2data are applied to correct color gradation in the process of combining the image data so that the combined image data represents a high quality image with smooth gradation.

When the same photographic image is to be read with a red light beam three times and over, the combined image data reaching the branch point P2returns to step S4to be temporarily stored in the hard disk176(step S4, for the second time). The data to be referred to as the LR3data is then acquired by reading the same photographic image with a red light beam for the third time at a light receiving level different from the light receiving levels LR1and LR2(steps S1, S2and S3, for the third time). The LR3data and the combined image data are combined after being subjected to level corrections (step S5) and weighting (step S6) to generate a new combined image (step S7). The present embodiment will be further described based on the premise that the same photographic image is read with a red light beam only twice.

When the image reading process using a red light beam is completed, the light source unit111emits a green light beam to read the same photographic image as done with a red light beam.

FIG. 7is a chart showing the timing of image reading.

As shown in the row T1of the chart, the light source unit111emits a red light beam for the first time at time period t1and for the second time at time t2. Next, the light source unit111emits a green light beam for the first time at time t3and then proceeds to emit a green light beam for the second time to be followed by emission of a blue light beam in the same manner. As shown in the row T2of the chart, the CCD115accumulates electric charge each time the light source unit111emits a light beam. That is, the CCD115accumulates electric charge for the first time when a red light beam is emitted for the first time at time t1, for the second time when a red light beam is emitted for the second time at time t2, and so on. As shown in the row T3of the chart, the accumulated electric charge is sequentially read out one cycle after an electric charge accumulation in the CCD, beginning at time period t2. The electric charge read out from the CCD115is converted into photographic image data by the A/D converter118. As shown in the row T4of the chart, the photographic image data that is generated from the electric charge accumulated when each of the red, green, and blue light beams is emitted for the first time is stored in the hard disk176shown inFIG. 3. When the electric charge accumulated when each of the red, green and blue light beams is emitted for the second time is read out, as shown in the row T5of the chart, the photographic image data generated based on each first-time light beam and stored in the hard disk176is also read out, and the two sets of photographic image data generated based on the first-time electric charge accumulation and the second-time electric charge accumulation, respectively, are added as shown in the row T6of the chart.

When reading the photographic image with each of the red, green and blue light beams for the first time and for the second time, it is preferable to adjust the first-time light receiving level and the second-time light receiving level to be in a ratio of 1:16. In the present embodiment, when the photographic image is read for the first time, the ND filter114is inserted to reduce the light receiving level. When the photographic image is read for the second time, the ND filter114is removed and pulse-width modulation is adjusted for the light source unit111to enhance the light receiving level. In this way, as compared with adjusting only the electric charge accumulation time, an ideal ratio (1:16) of the first-time reception level to the second-time reception level can be achieved much faster.

When reading of the photographic image with each of the red, green and blue light beams is completed as described above, the film carrier119shown inFIG. 2transports the photographic film20to allow reading of the next frame to be started.

Only one frame of image is read at a time while the photographic film20is kept still, and, only after reading of the current frame of image is completed, the process to read the next frame of image is started. In this way, the chance of error such as image data displacement due to, for example, a positional error in the operation of the film carrier119can be reduced. As a result, it becomes easier to obtain an unblurred quality image.

The description of the first embodiment of the image reading apparatus according to the invention is now completed. Hereafter, a second embodiment of the image reading apparatus according to the invention will be described. In the following description of the second embodiment, attention will be paid to the aspects of the second embodiment differing from the first embodiment. The aspects common between the first and the second embodiments will not be described in the following.

FIG. 8is a diagram showing a scanner section of the second embodiment.

A scanner section300of the present embodiment includes an LED light source310, a diffusion box320, an image pickup lens330, a half mirror340, an ND filter350, a CCD361and a CCD362. The CCD361and the CCD362constitute an example of plural reading elements according to the invention. The light beam emitted from the LED light source310illuminates the half mirror340via the image pickup lens330. The half mirror340splits the path L0of the light beam emitted from the LED light source310into the path L1leading to the CCD361and the path L2leading to the CCD362. The half mirror340constitutes an example of an optical path splitting section included in the image reading apparatus according to the invention.

The CPU171shown inFIG. 3makes the electric charge accumulation time longer at the CCD362than at the CCD361and controls the ND filter350to attenuate the light beam that illuminates the CCD361via the optical path L1. Through these means, the ratio of the light receiving level LR1at the CCD361to the light receiving level LR2at the CCD362is adjusted to 1:16. The CCD361and the CCD362perform image reading at the same time. The photographic image data generated by them are sent to the CPU171.

Reading an image using more than one CCD simultaneously at plural light receiving levels allows the total time required for image reading to be reduced, thereby contributing toward productivity improvement.

The description of the second embodiment of the invention is now completed.

Next, other embodiments associated with a scanner section will be described.

The CCD115of the first embodiment shown inFIG. 2is a monochrome CCD which merely detects the switching on and off of light. In the following, a scanner section of a third embodiment incorporating a color CCD capable of reading each of the red, green and blue components of light will be described.

The light source111included in the scanner section of the third embodiment does not emit red, green and blue light beams separately. It emits white light. In this case, because white light is emitted rather than separate R, G, and B lights from the light source111, and the color CCD (replacing the CCD115shown inFIG. 2) can collect the red, green and blue components included in the transmitted white light simultaneously, the processing time can be reduced. There is a drawback to the color CCD, however. That is, the image obtained using such a color CCD is inferior in quality to the image obtained using a monochrome CCD115.

FIG. 9is a diagram showing an example of a scanner section of a fourth embodiment.

The scanner section400of the fourth embodiment includes an LED light source410, a diffusion box420, an aperture430, an image pickup lens440, dichroic mirrors450IR (“IR” representing “infrared”),450R,450G and450B, line CCDs460IR,460R,460G,460B, and a film carrier470. The LED light source410emits a white light beam and an infrared light beam. The light beams illuminate the dichroic mirrors450IR,450R,450G and450B after being appropriately reduced in amount by the aperture430. The light beams reflected by the dichroic mirrors450IR,450R,450G and450B are received by the line CCDs460IR,460R,460G and460B to generate photographic image data from the respective light beams. The line CCDs460IR,460R,460G and460B are line sensors which can read an image line by line in the main scanning direction. Every time a line is scanned, the film carrier470moves the photographic film20in the sub-scanning direction. In the present embodiment, when reading an image, the scanner section400can collect red, green, blue image data and also infrared image data simultaneously on each line so that the overall processing time can be reduced. In this arrangement, however, the film carrier470moves the photographic film20in the sub-scanning direction every time scanning of a line ends so that positional errors may occur in the operation of the film carrier470to cause image data displacement.

FIG. 10is a diagram showing an example of a scanner section of a fifth embodiment.

The scanner section500of the fifth embodiment includes an LED light source510, a diffusion box520, an image pickup lens530, a 3-line CCD540, a CCD board550, an ND filter560and a film carrier570. The LED light source510emits white light. The 3-line CCD540can collect the red, green and blue components simultaneously for each line of the CCD from the light transmitted from the LED light source510.

FIG. 11is a diagram showing an example of a scanner section of a sixth embodiment.

The scanner section600of the sixth embodiment has a structure almost the same as that of the scanner section300of the second embodiment. The scanner section600includes an LED light source610, a diffusion box620, an image pickup lens630, a half prism640and two monochrome area CCDs650. The LED light source610sequentially emits red, green, blue, and infrared light beams. When each of these light beams is transmitted to the half prism640, it is divided into two to be received by the two monochrome area CCDs650simultaneously. Even though the scanner section600includes no ND filter, it is possible to achieve an ideal light receiving level ratio (1:16), for example, by unequalizing the electric charge accumulation times for the two monochrome area CCDs650and also adjusting the amounts of light to be received by the two monochrome area CCDs650. Like the scanner section300of the second embodiment, the scanner section600of the sixth embodiment can also generate high quality images at high speed.

FIG. 12is a diagram showing a scanner section of a seventh embodiment.

The scanner section700of the seventh embodiment includes an LED light source710, a diffusion box720, a reflecting mirror730, an image pickup lens740, an ND filter750, a 3-line CCD760, a CCD board770and a film carrier780. The LED light source710emits white light. The 3-line CCD760can collect the red, green and blue components simultaneously for each line of the CCD from the light transmitted from the LED light source710. In the scanner section700, line shifting for image reading is effected by moving the reflecting mirror730. Every time reading of a frame of image is completed, the film carrier780transports the photographic film20to allow the next frame of image to be read. While the scanner section700of this embodiment can reduce the overall processing time, it also serves to reduce the degree of line positioning errors as compared with the fourth and the fifth embodiments in which the film carrier is moved to advance image reading from one line to the next.

Embodiments of the image reading apparatus according to the invention in which plural light receiving levels are generated by adjusting an ND filter or pulse width modulation have been described in the foregoing. To generate plural light receiving levels, the first and the second level changing sections according to the invention may use such means as adjusting the light source current or voltage, the electric charge accumulating time at each CCD, or the light transmission factor.

In the embodiments described above, CCDs are used as reading elements, but other reading elements such as MOS devices may also be used in any embodiment of the invention.

The above embodiments of the image reading apparatus according to the invention are for application to a digital image printer. The image reading apparatus according to the invention may also be applied to a general-purpose scanner or copier in which an image is read based on the reflected light obtained by illuminating light from a light source onto the original.