JP2003309766A - Image reader - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To expand the dynamic range of an imaging device by the change of exposure and to speedily and precisely change the exposure. <P>SOLUTION: By applying an LED light source the light-emitting quantity of which under pulse width modulation control can precisely and easily be adjusted, imaging is performed under two kinds of light-emitting quantities with one image as an object to generate image data to be composed and outputted. In the case of a positive film 12, since transmissivity is low at a dark view such as a night view, imaging data in a state where the light-emitting quantity is large is applied. When there is a bright part within the same image, this bright part has high transmissivity. Thus, when the light-emitting quantity is large like this, the light-emitting quantity exceeds the saturation level of a CCD area sensor 44 soon. Then, the imaging data in a state where the light- emitting quantity is small is applied to the bright part. By compositing these, image data corresponding to a wide dynamic range within the image is obtained. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention comprises a photoelectric conversion element for irradiating a document image with light emitted from a light source, detecting the amount of reflected or transmitted light thereof, and converting it into an electric signal. The present invention relates to an image reading apparatus that obtains

[0002]

2. Description of the Related Art An original image, for example, a transmission image of a film such as a negative film or a positive film is irradiated with light sources of three primary colors, and the transmitted light is read by an image sensor (for example, CCD). , As a typical light source used in a film scanner for obtaining image data, a halogen lamp, a cold cathode tube, an L
ED etc. are mentioned.

Generally, the dynamic range (density range) of an image recorded on a film is wider than the dynamic range of an image pickup device, and therefore, conventionally, images are taken at different exposure amounts and are wider than the dynamic range of the image pickup device. Has been proposed (hereinafter, referred to as Prior Art 1) (for example, Japanese Patent Laid-Open No. 62-1086).
78, Japanese Patent No. 2919715).

However, in the above-mentioned prior art 1, adjustment of the diaphragm amount, change of the illumination intensity (current, voltage control), emergence of an optical filter, etc. are conceivable. However, when used in the film scanner as described above, it is highly accurate. Since it is necessary to change the light amount at high speed, there is a problem that the accuracy of the light amount cannot be maintained.

In order to solve the above problem, there has been proposed a technique for obtaining a wide dynamic range by changing the accumulation time of the image pickup device and reading a plurality of times (hereinafter referred to as prior art 2). (As an example, Patent No. 31123
No. 25), in the expansion of the dynamic range by changing the image pickup time, a non-linear component (dark current amount, linearity deterioration due to the knee effect, etc.) depending on the accumulation time of the image pickup element deteriorates the accuracy of the combination. There is a possibility to let.

In consideration of the above facts, it is an object of the present invention to provide an image reading apparatus capable of widening the dynamic range of an image pickup device by changing the exposure amount and changing the exposure amount quickly and accurately. .

[0007]

According to a first aspect of the present invention, there is provided a photoelectric conversion element which irradiates a document image with light emitted from a light source, detects the amount of reflected or transmitted light, and converts the detected light amount into an electric signal. An image reading apparatus for obtaining image data of the original image, wherein the light amount adjusting means for adjusting the emitted light amount of the light source by pulse width modulation, and the original image,
Irradiation control means for controlling the light quantity adjusting means to irradiate at least two different kinds of emitted light quantity, and imaging control means for executing imaging by the photoelectric conversion element under the respective emitted light quantities in the irradiation control means. And image data generating means for generating image data of the entire original image based on a plurality of image data captured by the image capturing control means.

A second aspect of the invention is characterized in that, in the first aspect of the invention, the light source is an LED or an organic or inorganic EL.

According to the first aspect of the invention, when irradiating the original image with light, the irradiation control means controls the light amount adjusting means to irradiate at least two different kinds of emitted light amounts stepwise. The image pickup control unit executes the image pickup by the photoelectric conversion element under each light emission amount of the irradiation control unit. Since the amount of emitted light is changed by pulse width modulation, it has good responsiveness and can be made with high precision, so that the image pickup time of the image pickup control means is not significantly delayed.

The imaged data generating means generates imaged data of the entire original image based on the plurality of imaged data.

Thus, the density information of the original image can be obtained in a dynamic range wider than the dynamic range of the image pickup device. For example, optimal image data (data with fine resolution) can be obtained in all areas even in a document image in which a bright room and a night view or the like seen from the room are photographed at the same angle of view.

As the light source, an LED or an organic or inorganic EL can be applied as described in claim 2.

According to a third aspect of the present invention, in the invention according to the first or second aspect, the image data generating means sets the saturation level in the image sensor for each predetermined area of a plurality of image data. It is characterized in that the image data of the entire original image is obtained by selecting the data having a lower output and the highest output.

According to the third aspect of the present invention, after obtaining a plurality of image pickup data, the data which is lower than the saturation level in the image pickup element and has the highest output is selected for each predetermined area. Get the image data for the entire image. This eliminates data that exceeds the saturation level, and
A higher output value can improve the S / N ratio.

According to a fourth aspect of the present invention, in the invention according to the first or second aspect, the image data generating means weights the data for each predetermined area of the plurality of image pickup data. It is characterized in that image data of the entire original image is obtained by combining them.

According to the fourth aspect of the present invention, when there is data that does not reach the saturation level in the same area, each data is weighted and combined, and It is possible to prevent the occurrence of density unevenness at boundaries that are likely to occur.

According to a fifth aspect of the invention, in the invention of the third or fourth aspect, the predetermined area is
It is characterized by being the minimum unit of the reading resolution of the image pickup device.

According to the fifth aspect of the present invention, an image having a wide dynamic range and a fine density difference is obtained by setting a predetermined area as a minimum unit when reading with an image pickup device, for example, a pixel unit. Data can be generated. In the case where a color filter is provided in the image pickup device and one data is set in units of three pixels for each color, the image data may be selected based on the color separation data of one of the three pixels. Alternatively, the entire original image may be roughly divided, and the original image may be uniquely selected in the divided area.

In the invention according to any one of claims 1 to 5, whether or not the imaging control means executes imaging under a plurality of emitted light amounts is determined by processing capability and image quality. You may further have the imaging function setting means set as a parameter.

That is, there is an undeniable delay in the physical imaging time when the imaging is performed a plurality of times. Therefore, if the processing capability is prioritized, the imaging is performed once as before, and if the image quality is prioritized, the imaging function is set according to each condition so that the imaging is performed a plurality of times. It is possible to obtain an objective effect that comprehensively meets the needs regarding the imaging process, rather than an objective effect that is biased to one of the ability and the image quality.

[0021]

1 and 2 show an image reading apparatus (film scanner) 10 according to this embodiment.

The original image applied in this embodiment is the silver halide photographic film 12. The positive film 12 is loaded into a camera (not shown), a latent image is recorded by being photographed, and then developed by a developing device (not shown).
Although a positive film (reversal film) 12 having a wider dynamic range of a recorded image will be described here as an example, the invention is not limited to the positive film 12 and may be a negative film or another transparent original.

As shown in FIG. 2, the positive film 12 is held substantially horizontally by being sandwiched between two pairs of conveying rollers 14 and 16. Conveyor rollers 14, 16
Are rotated at the same speed by a drive signal from the film transport system control unit 18 and transport the positive film 12 in the direction of arrow A in FIGS. 1 and 2.
It should be noted that by providing a slight speed difference between the transport rollers 14 and 16 (making the leading side in the transport direction slightly faster), or interposing a one-way clutch mechanism on the rear side in the transport direction, the positive film 12 is tensioned. You may make it convey.

A reading stage is provided between the transport rollers 14 and 16, and a lower portion of the reading stage is a light emitting side and an upper portion thereof is a reading side. The light emitting side has an LED light source 20 and a light diffusing plate. And 22 are provided. That is, the light emitted from the LED light source 20 passes through the light diffusion plate 22 and is emitted to the positive film 12,
The transmitted light passes through the positive film 12 and reaches the reading side. The light diffusion plate 22 is an LED.
It also has a role of protecting the light emitting surface of the light source 20.

In the LED light source 20 of this embodiment, the RG
The LED light emitting elements that emit light of each color B are dispersed and arranged in a predetermined area, and by emitting light for each color,
It has a structure that can read color images,
The emission color is switched according to a signal from the image reading control unit 50.

As shown in FIGS. 1 and 2, a condenser lens 42 is arranged on the reading side, and the positive film 1
The light transmitted through 2 is collected. A CCD area sensor 44 is provided at the image forming point of the condenser lens 42.
The reading unit 44A of the CD area sensor 44 detects the density of transmitted light.

The CCD area sensor 44 is connected to the A / D conversion section 52 of the image reading control section 50, and the photoelectrically converted electric signal (density data) is analog-digital converted.

The A / D conversion section 52 is an input data management section 54.
It is connected to the. In the input data management unit 54, the LED
The role of sending a drive signal for turning on the light source 44 to the LED drive control section 55 and sending the LED light quantity information for setting the light quantity of the LED light source 44 to the duty instruction section 56, and the CCD area sensor 44 to A / D. Converter 52
Data input via the first memory 58 or the second memory
And the role of selectively storing it in the memory 60.

In the LED drive control section 55, the instruction signal from the input data management section 54 and the film transport system control section 1
The LED light source 44 is turned on based on the instruction signal from 8. In addition, in the LED drive control unit 55, each color (R
It is controlled so that the lights are sequentially turned on for each GB), and the reading value by the CCD area sensor 44 by the irradiation light of each color becomes one set and is sent to the A / D conversion unit 52. ing.

Here, in the present embodiment, the LED drive control unit 55 is instructed to the LED by the duty instruction unit 56.
Two kinds of duty of the drive signal (pulse signal) at the time of driving are instructed. One is a duty for relatively increasing the emitted light amount (see FIG.
(See (A)), and the other is a duty for relatively reducing the amount of emitted light (see FIG. 3B).

The switching of the duty is executed by a signal from the input data management section 54. That is, the one set of reading is executed in a state where the emitted light amount is controlled by one duty, and then the one set of the one set is read while the emitted light amount is controlled by the other duty for the same image. Read is to be performed.

In the input data management section 54, since the above-mentioned two sets of image pickup data are continuously input for one image, the image pickup data of each set is stored in the first memory 5.
8 and the second memory 60 are stored separately.

The above-mentioned first memory 58 and second memory 6
0 is connected to the data generation unit 62, and when the image pickup data for one image (two sets) is stored in the respective memories (first memory 58 and second memory 60), the image pickup data Is read out, and image data to be output by the data output unit 64 is generated.

That is, the imaged data is decomposed into read pixel units, which are the minimum units of the reading resolution of the CCD area sensor 44, and the data read by the same pixel is compared. In this comparison, it is determined whether or not the saturation level of the CCD area sensor 44 is exceeded, and if both are not exceeded, which one has a higher output value (basically whether or not the emitted light amount is higher). It has come to be judged.

FIG. 4 shows C at two different kinds of emitted light amounts.
An output characteristic diagram of the CD area sensor 44 is shown.

As can be seen from FIG. 4, the saturation level of the CCD area sensor 44 is constant, but in the two types of output characteristics, it is faster that the saturation level is exceeded when the amount of light is large. Therefore, an image with a smaller light amount can be read in a wider dynamic range. However, the smaller the amount of light, the lower the output resolution because the characteristic is repulsive (the inclination is small).

Therefore, in this embodiment, a lower limit threshold (same level as the noise allowable level) and an upper limit threshold (a level slightly lower than the saturation level) are provided, and the lower limit threshold and the upper limit threshold are set. If it is within the range of the value and is read in duplicate, the one with the higher output is selected.

For example, as shown in FIG. 5A, when a bright area L such as a room and a dark area D such as a night view seen through a window W are mixed in the same image, the bright area L is In the case of the positive film 12, since the image has a high transmittance, the image captured on the side with a small amount of emitted light is applied (see FIG. 5B), and conversely, in the dark region, the transmittance is low in the case of the positive film 12. The image picked up on the side with a large amount of emitted light is applied (see FIG. 5C).

The regions L and D are roughly divided for the sake of explanation, and any image data is selected for each pixel in each region.

As described above, one image pickup data is selected for each pixel, and all the image pickup data are set as the image data, which is sent out from the data output unit 64 to the outside.

The output image data is sent to, for example, an image recording device (not shown) to be subjected to various corrections, and then digitally exposed on photographic paper or the like to form an image.

The operation of this embodiment will be described below.

The positive film 12 on which an image is recorded is sandwiched between two pairs of conveying rollers 14 and 16 and positioned on the reading stage for each frame.

When the positioning is completed, image reading is started. At this time, in order to obtain image data in full color for the image frame, C for each color of RGB is set in time series.
First, LE is read by the CD area sensor 44.
The D light source 20 is R color light.

The light diffusing plate 22 diffuses the R color light emitted in a part of the light emitting region so that the light amount becomes uniform throughout the light emitting region.

Since the diffused light is applied to the positive film 12, a uniform amount of R color light is applied over the entire area of the image to be read.

At this time, from the duty instruction section 56,
A duty instruction signal for reducing the amount of emitted light is sent to the LED drive unit 55, and irradiation is performed in a state where the amount of emitted light is small.

The R color light transmitted through the image on the positive film 12 is condensed by the condenser lens 42 and input to the reading section 44A of the CCD area sensor 44. As a result, the light incident on the reading unit 44A is photoelectrically converted, and an electric signal (voltage) corresponding to the image density of the component corresponding to the R color light is converted into A / D.
It is sent to the conversion unit 52. The A / D converter 52 converts the input electric signal into a digital signal and sends it to the input data manager 54 as digital image data.

The input data management unit 54 stores the image pickup data of the R color light in the R color light area of the first data memory 58.

When the image reading with the R color light is completed, the same reading is subsequently performed with the G color light and the B color light.

The image pickup data can be obtained in the state where the emitted light amounts of these G color light and B color light are also small, and the G data of the first data memory 58 can be obtained.
It is stored in the colored light and B colored light areas.

Next, in the input data management section 54, when the image reading in the state where the emitted light quantity is small is completed, the input data management section 54 sends the emitted light quantity switching signal to the duty instruction section 56. The duty instruction unit 56 that has received the emitted light amount switching signal sends out a duty instruction signal that makes the emitted light amount large. As a result, the LED drive control unit 55 controls the LED light source 20 so that the LED light source 20 emits light with a large amount of emitted light.

The LED light source 20 irradiates the R-color light, the G-color light, and the B-color light with a large amount of the emitted light, obtains respective image pickup data, and manages the input data via the A / D converter 52. It is sent to the unit 54.

The input data management section 54 stores the image pickup data with a large amount of emitted light in each color area of the second data memory 60.

By the above reading operation, two kinds of image data exist for one image.

In the data generation section 62, when these two types of image pickup data are prepared, the image pickup data for each color is read out from the first data memory 58 and the second data memory 60, and they are combined into one image data. To generate.

As shown in FIG. 4, the combination of the image pickup data is executed based on the received light amount-output characteristic of the CCD area sensor 44.

The output value is noisy when the value is low,
S / N is bad. Therefore, the allowable noise level is set as the lower limit threshold, and a value exceeding this lower limit threshold is applied. In this case, the image data captured with a large amount of emitted light is faster than the image data captured with a small amount of emitted light, and exceeds the lower threshold and is output (absolute output).
Is large, the image pickup data stored in the first memory 58 is applied to the region where the amount of received light is small.

However, the image pickup data picked up with a large amount of emitted light reaches the light emission saturation level faster than the image pickup data taken with a small amount of emitted light. this is,
This means that the dynamic range is narrow, and since it is narrower than the dynamic range of the image, the high-density side may be crushed (the resolution is lost).

Therefore, in the present embodiment, image pickup data read in a state where the amount of emitted light is small and the amount of emitted light is predetermined is applied. The switching timing of the imaged data was set to a value slightly lower than the saturation level as an upper limit threshold, and the amount of received light corresponding to this upper limit threshold was set.

By thus changing the amount of emitted light and switching the image pickup data applied at a predetermined amount of received light, the generated image data has the characteristics shown by the chain line in FIG. 4, and apparently exceeds the saturation level. With almost constant resolution in the state,
Images can be taken over a wide dynamic range.

As a result, the dynamic range of the CCD area sensor 44 can be expanded. This CCD
By expanding the dynamic range of the area sensor 44, a predetermined resolution can be ensured even on the high density side, and the dynamic range of the image can be approximated.

In this embodiment, the change of the emitted light amount is changed to LE.
Since it is executed by the pulse width modulation control (duty control) of the D drive signal (voltage or current), there is no decrease in responsiveness due to mechanical drive (adjustment of the diaphragm, appearance of the optical filter, etc.), and Imaging of a wide range (wide dynamic range) can be performed accurately and quickly by preventing unstable output value fluctuations by controlling the emission intensity by amplitude (voltage value amplitude or current value amplitude). Is possible.

As described above, in the present embodiment, the LED light source 20 is used in which the amount of emitted light in the pulse width modulation control (duty control) can be adjusted accurately and easily.
One image is taken as an object under at least two types of emitted light amounts, and the image data of two or more types are combined to generate image data to be output. In the case of the positive film 12, since the transmittance is low in a dark scene such as a night scene, image pickup data in a state where the amount of emitted light is large is applied. On the other hand, when there is a bright portion in the same image, the light transmittance is high in this bright portion.
The saturation level of 4 will be exceeded. Therefore, for the bright portion, image pickup data in a state where the emitted light amount is small is applied. Image data corresponding to a wide dynamic range in an image can be obtained by combining these (see FIG. 5).

In the present embodiment, the image pickup data to be applied with a predetermined amount of received light is switched and applied, but there are two types of image pickup data within the range of the upper limit threshold and the lower limit threshold. In this case, the data obtained by subjecting both to appropriate weighting processing may be applied as final image data.

The weighting depends on, for example, the amount of received light. The smaller the amount of received light is, the larger the ratio of the imaged data is when the amount of emitted light is larger. Should be increased.

Further, although the CCD area sensor 44 is applied as the image pickup device in the present embodiment, the same effect can be obtained even when another image pickup device such as a CCD line sensor is applied.

Further, in the present embodiment, the case where the image on the positive film 12 is read as an original image has been described as an example, but this is because the image on the positive film 12 has a wide dynamic range, so that the image on the negative film is Is also applicable, and may be a monochrome image. However, in the case of a negative film, simultaneous printing is often requested, and when it is necessary to give priority to the processing capability, the above-mentioned two imagings for one image causes a reduction in the processing capability.
Therefore, the process selector 66 (see FIG. 2) is added to the input data manager 54.
(See the imaginary line in Fig. 2), and it is determined whether to prioritize the processing capacity or the image quality manually or automatically according to the type of film or the order status, and the image pickup pattern that combines the two types of image data Alternatively, an image pickup pattern to be processed with only one image pickup data may be selected.

Further, in the present embodiment, the image pickup is executed under two kinds of emitted light amounts, but the image pickup may be executed under three kinds or more of emitted light amounts.

Further, although the image pickup data is selected for each pixel, a group of a plurality of pixels may be set as a group and the image pickup data may be selected for each group. For example, in the areas L and D shown in FIG. 5, any image data may be uniquely selected in each area. Also, CC
In the case where the RGB color filter is mounted on the D area sensor 44 with 3 pixels as one unit and data for each color is obtained by one reading, one pixel among the 3 pixels forming one unit is selected. It may be a selection determination target pixel.

[0071]

As described above, the present invention has an excellent effect that the dynamic range of the image pickup device can be widened by changing the exposure amount and the exposure amount can be changed quickly and accurately.

[Brief description of drawings]

FIG. 1 is a perspective view of a film scanner according to the present embodiment.

FIG. 2 is a schematic configuration diagram of a film scanner according to the present embodiment.

FIG. 3 is a drive signal for causing the LED light source to emit light, (A) is a duty when the amount of emitted light is large, and (B) is a drive signal.
Indicates the duty when the amount of emitted light is small.

FIG. 4 is a light receiving amount-output characteristic diagram of a CCD area sensor.

FIG. 5 is a front view of an image when a bright area and a dark area are mixed.

[Explanation of symbols]

10 Film scanner (image reading device) 12 Positive film (original image) 14, 16 Conveyor rollers 18 Film transport system controller 20 light sources 22 Light diffuser 42 Condensing lens 44 CCD area sensor (imaging device) 44A reading unit 50 Image reading controller 52 A / D converter 54 Input data management unit (imaging control means) 55 LED drive control unit (irradiation control means) 56 Duty indicator (light quantity adjusting means) 58 First Data Memory 60 Second data memory 62 data generation unit (image data generation means) 64 data output section 66 Process selection unit (imaging function setting means)

Claims (5)

[Claims] 1. An image reading apparatus for obtaining image data of an original image, comprising a photoelectric conversion element for irradiating an original image with light emitted from a light source, detecting the amount of reflected or transmitted light, and converting the detected amount of light into an electric signal. There is a light amount adjusting means for adjusting the emitted light amount of the light source by pulse width modulation, and controlling the light amount adjusting means for the original image,
Irradiation control means for irradiating at least two kinds of different emitted light amounts, and under each emitted light amount by the irradiation control means,
Image reading including image pickup control means for performing image pickup by the photoelectric conversion element, and image data generation means for generating image data of the entire document image based on a plurality of image pickup data picked up by the image pickup control means apparatus. 2. The image reading apparatus according to claim 1, wherein the light source is an LED or an organic or inorganic EL. 3. The image data generation means selects, for each predetermined area of a plurality of image pickup data, data having a highest output and lower than a saturation level in the image pickup element, and selects image data of the entire original image. The image reading device according to claim 1 or 2, wherein the image reading device is obtained. 4. The image data generating means obtains image data of an entire original image by weighting and combining data for each predetermined area of a plurality of image pickup data. Item 2. The image reading device according to item 2. 5. The image reading apparatus according to claim 3, wherein the predetermined area is a minimum unit of reading resolution of the image sensor.