JP3947032B2 - Image reading device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an image reading apparatus that includes a photoelectric conversion element that irradiates a document image with light emitted from a light source, detects the amount of light reflected or transmitted, and converts it into an electrical signal, and obtains image data of the document image. It is.
[0002]
[Prior art and problems to be solved by the invention]
It is used as a light source in a film scanner that obtains image data by irradiating a light image of three primary colors onto an original image, for example, a transmitted image of a film such as a negative film or a positive film, and reading the transmitted light with an image sensor (for example, CCD). Typical examples include a halogen lamp, a cold cathode tube, and an LED.
[0003]
In general, the dynamic range (density range) of an image recorded on film is wider than the dynamic range of an image sensor. An imaging technique (hereinafter referred to as Prior Art 1) has been proposed (see, for example, Japanese Patent Application Laid-Open No. 62-108678 and Japanese Patent No. 2919715).
[0004]
However, in the above prior art 1, adjustment of the aperture amount, change of illumination intensity (current and voltage control), optical filter in / out, and the like can be considered. There is a problem that the accuracy of the amount of light cannot be maintained.
[0005]
In order to solve the above problem, a technique for obtaining a wide dynamic range (hereinafter referred to as “prior art 2”) by changing the accumulation time of the image sensor and performing reading a plurality of times has been proposed (as an example). In the enlargement of the dynamic range by changing the imaging time, the nonlinear component (dark current amount, linearity degradation due to knee effect, etc.) depending on the storage time of the imaging device is not accurate. May worsen.
[0006]
In view of the above-described facts, an object of the present invention is to obtain an image reading apparatus that can widen the dynamic range of an image sensor by changing the exposure amount and can change the exposure amount quickly and accurately.
[0007]
[Means for Solving the Problems]
The invention according to claim 1 is provided with a photoelectric conversion element that irradiates the original image with light emitted from a light source, detects the amount of light reflected or transmitted, and converts it into an electric signal, and obtains image data of the original image. In the image reading apparatus, the light amount adjusting unit that adjusts the light emission amount of the light source by pulse width modulation and the light amount adjustment unit are controlled to irradiate the original image with at least two different light emission amounts. Based on a plurality of imaging data captured by the imaging control means, an imaging control means for performing imaging by the photoelectric conversion element under the respective light emission amounts by the irradiation control means, and the original document Image data generating means for generating image data of the entire image.
[0008]
The invention described in claim 2 is characterized in that, in the invention described in claim 1, the light source is an LED or an organic or inorganic EL.
[0009]
According to the first aspect of the present invention, when irradiating light on the document image, the irradiation control unit controls the light amount adjusting unit to irradiate stepwise with at least two different light emission amounts. In this imaging control means, imaging by the photoelectric conversion element is executed under each light emission quantity by the irradiation control means. Since the change in the amount of emitted light is performed by pulse width modulation, the responsiveness is good and can be performed with high accuracy, so that the imaging time in the imaging control means is not significantly delayed.
[0010]
The imaging data generation unit generates imaging data of the entire document image based on the plurality of imaging data.
[0011]
Thereby, it is possible to obtain the density information of the document image in a dynamic range wider than the dynamic range of the image sensor. For example, optimal image data (data with a fine resolution) can be obtained in all areas even in a bright room and a manuscript image or the like taken at the same angle of view of a night view or the like seen from the room.
[0012]
As the light source, an LED or an organic or inorganic EL can be applied as described in claim 2.
[0013]
According to a third aspect of the present invention, in the first or second aspect of the present invention, the image data generation means is lower than a saturation level in the image sensor for each predetermined region of a plurality of image data. In addition, the image data of the entire original image is obtained by selecting the data with the highest output.
[0014]
According to the third aspect of the present invention, after obtaining a plurality of imaging data, for each predetermined area, data lower than the saturation level in the imaging device and having the highest output is selected and the entire document image is selected. Obtain image data. As a result, data that exceeds the saturation level can be eliminated, and a higher output value can improve the S / N ratio.
[0015]
According to a fourth aspect of the present invention, in the invention according to the first or second aspect, the image data generating means performs data weighting for each predetermined region of the plurality of imaging data, It is characterized in that imaging data of the entire original image is obtained.
[0016]
According to the fourth aspect of the present invention, when there is data that has not reached the saturation level in the same region, the boundary that is likely to be generated due to the synthesis is obtained by weighting each data and synthesizing the data. It is possible to prevent the occurrence of unevenness in density.
[0017]
The invention according to claim 5 is the invention according to claim 3 or 4, wherein the predetermined area is a minimum unit of reading resolution of the image sensor.
[0018]
According to the fifth aspect of the present invention, image data having a wide dynamic range and a fine density difference is generated by setting a predetermined area as a minimum unit for reading with an image sensor, for example, one pixel unit. can do. In the case where a color filter is provided in the image sensor and one data is obtained in units of three pixels for each color, image data may be selected based on one color separation data of the three pixels. Alternatively, the entire document image may be roughly divided and selected uniquely within the divided area.
[0019]
Note that in the invention according to any one of claims 1 to 5, whether or not to perform imaging under a plurality of light emission amounts by the imaging control unit is set as a parameter of processing capability and image quality. You may further have an imaging function setting means to do.
[0020]
In other words, performing a plurality of times of imaging cannot deny a delay in physical imaging time. Therefore, when priority is given to the processing capability, the imaging function is set to one time as before, and when priority is given to the image quality, the imaging function is set according to the respective conditions so that the imaging is performed a plurality of times. It is possible to obtain an objective effect that meets the overall needs regarding the imaging processing, not the objective effect that is biased toward either capability or image quality.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
1 and 2 show an image reading apparatus (film scanner) 10 according to the present embodiment.
[0022]
The original image applied in the present embodiment is a silver salt photographic film 12. The positive film 12 is loaded into a camera (not shown), and a latent image is recorded by being photographed. Then, the positive film 12 is developed by a developing device (not shown). Here, a positive film (reversal film) 12 having a wider dynamic range of recorded images will be described as an example. However, the film is not limited to the positive film 12 but may be a negative film or other transparent original.
[0023]
As shown in FIG. 2, the positive film 12 is held substantially horizontally by being sandwiched between two pairs of transport rollers 14 and 16. The transport rollers 14 and 16 are rotated at the same speed with each other 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. In addition, in a state where the positive film 12 is tensioned by providing a slight speed difference between the transport rollers 14 and 16 (making the transport direction leading side slightly faster) or by interposing a one-way clutch mechanism on the rear side in the transport direction. You may make it convey.
[0024]
A space between the transport rollers 14 and 16 is a reading stage. A lower portion of the reading stage is a light emitting side, an upper portion is a reading side, and an LED light source 20 and a light diffusion plate 22 are provided on the light emitting side. It is arranged. That is, the light emitted from the LED light source 20 passes through the light diffusion plate 22 and is applied to the positive film 12, and the transmitted light passes through the positive film 12 and reaches the reading side. The light diffusing plate 22 also serves as protection of the light emitting surface of the LED light source 20.
[0025]
In the LED light source 20 of the present embodiment, LED light emitting elements that emit light of each color of RGB are dispersedly arranged in a predetermined area, and a color image can be read by emitting light for each color. The emission color is switched according to the signal from the image reading control unit 50.
[0026]
As shown in FIGS. 1 and 2, a condensing lens 42 is disposed on the reading side, and condenses the light transmitted through the positive film 12. A CCD area sensor 44 is disposed at the image forming point of the condenser lens 42, and the density of transmitted light is detected by the reading unit 44 </ b> A of the CCD area sensor 44.
[0027]
The CCD area sensor 44 is connected to the A / D converter 52 of the image reading controller 50, and the photoelectrically converted electrical signal (density data) is converted from analog to digital.
[0028]
The A / D conversion unit 52 is connected to the input data management unit 54. In the input data management unit 54, a drive signal for turning on the LED light source 44 is sent to the LED drive control unit 55, and LED light quantity information for setting the light quantity of the LED light source 44 is sent to the duty instruction unit 56; And a function of selectively storing data input from the CCD area sensor 44 via the A / D converter 52 in the first memory 58 or the second memory 60.
[0029]
The LED drive control unit 55 turns on the LED light source 44 based on the instruction signal from the input data management unit 54 and the instruction signal from the film transport system control unit 18. Further, the LED drive control unit 55 performs control so that each color (RGB) is turned on in order, and the reading value by the CCD area sensor 44 with the irradiation light of each color becomes one set. It is sent to the / D converter 52.
[0030]
Here, in the present embodiment, the LED drive control unit 55 is instructed from the duty instruction unit 56 for two types of duty of a drive signal (pulse signal) during LED driving. One is a duty for relatively increasing the amount of emitted light (see FIG. 3A), and the other is a duty for relatively decreasing the amount of emitted light (see FIG. 3B).
[0031]
This duty switching is executed by a signal from the input data management unit 54. That is, the one set of reading is executed in a state in which the amount of emitted light is controlled at one duty, and then the amount of emitted light is controlled in the state in which the amount of emitted light is controlled at the other duty for the same image. Reading is to be performed.
[0032]
In the input data management unit 54, since the two sets of imaging data are continuously input for one image, the respective sets of imaging data are distributed to the first memory 58 and the second memory 60. It comes to memorize.
[0033]
The first memory 58 and the second memory 60 are connected to a data generation unit 62, and image data for one image (for two sets) are stored in the respective memories (the first memory 58 and the second memory). 60), the imaged data is read out and image data to be output by the data output unit 64 is generated.
[0034]
That is, the imaging data is decomposed into reading pixel units which are the minimum unit of reading resolution of the CCD area sensor 44, and the data read by the same pixels are compared. This comparison is based on whether or not the saturation level of the CCD area sensor 44 is exceeded, and if both are not exceeded, whichever has the higher output value (basically, the light emission quantity is higher). It has come to be judged.
[0035]
FIG. 4 shows an output characteristic diagram of the CCD area sensor 44 at two different types of light emission amounts.
[0036]
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, the larger the amount of light, the faster the saturation level is exceeded. Therefore, an image can be read with a wider dynamic range when the amount of light is smaller. However, the smaller the light quantity, the lower the output resolution because the characteristics are distorted (the inclination is small).
[0037]
Therefore, in the present embodiment, a lower limit threshold value (the same level as the noise allowable level) and an upper limit threshold value (a level slightly lower than the saturation level) are provided, and the lower limit threshold value and the upper limit threshold value are If it is within the range and is read redundantly, the higher output is selected.
[0038]
For example, as shown in FIG. 5A, when a bright region L such as a room and a dark region D such as a night view seen from the window W are mixed in the same image, the positive film 12 is used in the bright region L. In this case, since the image has high transmittance, the image captured on the side where the amount of emitted light is small is applied (see FIG. 5B). Conversely, in the dark region, the transmittance is low in the case of the positive film 12, and thus the amount of emitted light. The image picked up on the side where there is a lot is applied (see FIG. 5C).
[0039]
The regions L and D are roughly divided for the sake of explanation, and any one of the image data is selected for each pixel in each region.
[0040]
As described above, one piece of imaging data is selected for each pixel, and all of them are set as image data and sent out from the data output unit 64 to the outside.
[0041]
The output image data is sent to an image recording apparatus (not shown), for example, and after various corrections are performed, it is digitally exposed on photographic paper or the like to form an image.
[0042]
The operation of this embodiment will be described below.
[0043]
The positive film 12 on which an image is recorded is sandwiched between two pairs of transport rollers 14 and 16 and positioned on the reading stage for each frame.
[0044]
When positioning is completed, reading of an image is started. At this time, in order to obtain full-color image data for the image frame and read by the CCD area sensor 44 in time series for each color of RGB, first, the LED light source 20 is set to R color light.
[0045]
The light diffusing plate 22 diffuses the R-color light emitted from a part of the light emitting region so that the amount of light is uniform throughout the light emitting region.
[0046]
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.
[0047]
At this time, a duty instruction signal for reducing the amount of emitted light is sent from the duty instruction unit 56 to the LED drive unit 55, and irradiation is performed in a state where the amount of emitted light is small.
[0048]
The R color light transmitted through the image on the positive film 12 is collected by the condenser lens 42 and input to the reading unit 44 </ b> A of the CCD area sensor 44. Thereby, 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 sent to the A / D conversion unit 52. The A / D conversion unit 52 converts the input electrical signal into a digital signal and sends the digital signal to the input data management unit 54 as digital imaging data.
[0049]
The input data management unit 54 stores the imaging data with the R color light in the R color light area of the first data memory 58.
[0050]
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.
[0051]
These G color light and B color light are also obtained in a state where the amount of emitted light is small and stored in the G color light and B color light areas of the first data memory 58.
[0052]
Next, the input data management unit 54 sends a light emission amount switching signal to the duty instruction unit 56 when image reading in a state where the light emission amount is small is completed. In response to the light emission amount switching signal, the duty instruction unit 56 sends a duty instruction signal that increases the light emission amount. As a result, the LED drive control unit 55 performs control so that the LED light source 20 is irradiated with a large amount of emitted light.
[0053]
The LED light source 20 irradiates each of the R color light, the G color light, and the B color light in a state in which the amount of emitted light is large, obtains respective image data, and sends it to the input data management unit 54 via the A / D conversion unit 52. Send it out.
[0054]
In the input data management unit 54, image data with a large amount of emitted light is stored in each color area of the second data memory 60.
[0055]
By the above reading operation, two types of image data exist for one image.
[0056]
In the data generation unit 62, when these two types of imaging data are prepared, the imaging data is read out for each color from the first data memory 58 and the second data memory 60, and is combined to generate one image data. .
[0057]
The combination of the imaging data is executed based on the received light amount-output characteristic in the CCD area sensor 44, as shown in FIG.
[0058]
When the output value is low, there is a lot of noise and the S / N is bad. For this reason, the allowable noise level is set as the lower threshold, and a value exceeding this lower 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 the output (absolute output) is larger. In an area where the amount of received light is small, the imaging data stored in the first memory 58 is applied.
[0059]
However, the imaging data imaged with the large amount of emitted light reaches the light emission saturation level faster than the imaging data imaged with the small amount of emitted light. This means that the dynamic range is narrow, and since the dynamic range of the image is narrower, the high density side may be crushed (resolution is lost).
[0060]
Therefore, in the present embodiment, imaging data read with a predetermined amount of received light and a small amount of emitted light is applied. As the switching timing of the imaging data, a value slightly lower than the saturation level is set as the upper threshold, and the received light amount corresponding to the upper threshold is set.
[0061]
By switching the imaging data to be applied at a predetermined received light amount by changing the amount of emitted light in this way, the generated image data has the characteristics shown by the chain line in FIG. 4 and is apparently almost in a state exceeding the saturation level. Imaging can be performed over a wide dynamic range with a constant resolution.
[0062]
Thereby, the dynamic range of the CCD area sensor 44 can be expanded. By expanding the dynamic range of the CCD area sensor 44, a predetermined resolution can be secured even on the high density side, and the dynamic range of the image can be brought close to.
[0063]
In the present embodiment, the change in the amount of emitted light is performed by the pulse width modulation control (duty control) of the LED drive signal (voltage or current), and thus, for example, mechanical drive (adjustment of the diaphragm, appearance of the optical filter, etc.) There is no decrease in the responsiveness caused by this, and it is possible to prevent unstable fluctuations in the output value by controlling the emission intensity with the amplitude (the amplitude of the voltage value or the amplitude of the current value). Imaging in a wide range (wide dynamic range) can be performed quickly.
[0064]
As described above, in the present embodiment, the LED light source 20 that can adjust the amount of light emitted by the pulse width modulation control (duty control) accurately and easily is applied, and at least two types of images are targeted. An image is taken under the amount of emitted light, and the two or more types of image data 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 view, image 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 transmittance is high in the bright portion. Therefore, if the amount of emitted light is large, the saturation level of the CCD area sensor 44 is quickly exceeded. Therefore, image data with a small amount of emitted light is applied to bright portions. By combining these, image data corresponding to a wide dynamic range in the image can be obtained (see FIG. 5).
[0065]
In the present embodiment, the imaging data to be applied with a predetermined amount of received light is switched and applied. However, when there are two types of imaging data within the range of the upper threshold and the lower threshold, You may make it apply the data which gave weighting processing to both suitably and was combined as final image data.
[0066]
The weighting depends on, for example, the amount of received light. The smaller the amount of received light, the larger the ratio of image data when the amount of emitted light is larger, and the higher the amount of received light, the larger the ratio of image data when the amount of emitted light is small. What should I do?
[0067]
In the present embodiment, the CCD area sensor 44 is applied as the image sensor, but the same effect can be obtained even when another image sensor such as a CCD line sensor is applied.
[0068]
Furthermore, in the present embodiment, an example of reading an image on the positive film 12 as an original image has been described. However, this is because the image on the positive film 12 has a wide dynamic range, and can be applied to an image on a negative film. Furthermore, it may be a black and white image. However, in the case of a negative film, there are many cases where simultaneous printing is requested, and when it is necessary to give priority to the processing capability, the above-described imaging twice for one image causes a reduction in processing capability. Therefore, a processing selection unit 66 (see the imaginary line in FIG. 2) is provided in the input data management unit 54 to determine whether to prioritize processing power or image quality manually or automatically according to the type of film or order status. It is also possible to select and select an imaging pattern that performs a combination process of two types of imaging data and an imaging pattern that performs processing using only one imaging data.
[0069]
Further, in the present embodiment, imaging is performed under two types of light emission amounts, but imaging may be performed under three or more types of light emission amounts.
[0070]
Furthermore, although the selection of the imaging data is performed for each pixel, the imaging data may be selected for each group by taking a group of a plurality of pixels as a group. For example, in the areas L and D shown in FIG. 5, any one of the image data may be selected uniquely in each area. Further, in the case of a configuration in which an RGB color filter is attached to the CCD area sensor 44 as one unit and data for each color is obtained by one reading, one of the three pixels constituting one unit is obtained. The pixel may be a selection determination target pixel.
[0071]
【The invention's effect】
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 the drawings]
FIG. 1 is a perspective view of a film scanner according to an embodiment.
FIG. 2 is a schematic configuration diagram of a film scanner according to the present embodiment.
FIGS. 3A and 3B are drive signals for causing an LED light source to emit light. FIG. 3A shows a duty when the amount of emitted light is large, and FIG. 3B shows a duty when the amount of emitted light is small.
FIG. 4 is a light reception amount-output characteristic diagram of a CCD area sensor.
FIG. 5 is a front view of an image when a bright region and a dark region coexist.
[Explanation of symbols]
10 Film scanner (image reading device)
12 Positive film (original image)
14, 16 Transport roller 18 Film transport system controller 20 Light source 22 Light diffusing plate 42 Condensing lens 44 CCD area sensor (imaging device)
44A Reading unit 50 Image reading control unit 52 A / D conversion unit 54 Input data management unit (imaging control means)
55 LED drive control unit (irradiation control means)
56 Duty indication part (light quantity adjustment means)
58 First data memory 60 Second data memory 62 Data generation unit (image data generation means)
64 Data output unit 66 Process selection unit (imaging function setting means)

Claims (5)

An image reading apparatus that includes a photoelectric conversion element that irradiates a document image with light emitted from a light source, detects a reflected or transmitted light amount, and converts the light into an electrical signal, and obtains image data of the document image,
A light amount adjusting means for adjusting a light emission amount of the light source by pulse width modulation;
An irradiation control unit that controls the light amount adjusting unit to irradiate the original image with at least two different light emission amounts;
Imaging control means for performing imaging by the photoelectric conversion element under each light emission amount in the irradiation control means;
Image data generating means for generating image data of the entire document image based on a plurality of imaging data imaged by the imaging control means;
An image reading apparatus. The image reading apparatus according to claim 1, wherein the light source is an LED or an organic or inorganic EL. The image data generating means selects image data of a whole document image by selecting data having a highest output and lower than a saturation level in the image sensor for each predetermined region of a plurality of image data. The image reading apparatus according to claim 1 or 2. 3. The image according to claim 1, wherein the image data generation means obtains image data of the entire original image by combining the weighted data for each predetermined area of the plurality of image data. Reader. The image reading apparatus according to claim 3, wherein the predetermined area is a minimum unit of reading resolution of the image sensor.

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