JPH06233073A - Picture input device - Google Patents

Abstract

PURPOSE:To obtain a wide dynamic range by reading the same image plural times and integrating the obtained image signal. CONSTITUTION:A system controller 90 can read an image in the same position plural times without moving a one-dimensional sensor 50. That is, in the read operation of one line, the first read is performed in the same position with a high-sensitivity characteristic, and picture data as the result is temporarily stored in a line memory 80. Next, the second read is performed with a low- sensitivity characteristic, and the read result is sent to an operation circuit 81 together with the read result for the high sensitivity, and two read results are subjected to addition and multiplication processings and are sent to an image memory 82. Thereafter, a one-dimensional sensor moving mechanism 53 is operated to move the sensor 50 to the read position of the next line, and the next line is read. Thus, the image is read in a wider range of taking-in.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an input device for images having continuous gradation, and more particularly to an image input device suitable for handling recorded images having a wide dynamic range such as photographic film.

[0002]

2. Description of the Related Art Conventionally, as an image input device for obtaining an electric image signal from an image such as a photographic film, an input device such as a video camera using a two-dimensional image sensor or a scanner using a one-dimensional image sensor. Is widely used.

Range of densities recorded on photographic film (dynamic range, hereinafter referred to as dynamic range)
Is usually 3 or more in the case of a positive film, that is, 3 or more digits in the dynamic range of luminance. In addition, it is about 4 or more (4 digits or more in brightness) for the X-ray film.

On the other hand, the dynamic range on the reading side of a solid-state image sensor (an element that performs photoelectric conversion by a storage-type photoelectric conversion semiconductor (generally a photodiode or CCD) or the like) is about two digits in luminance.

Therefore, conventionally, the dynamic range on the input side is narrower than the dynamic range of an image such as a photographic film to be input, and only a part of the original image can be read.

As a method of expanding the dynamic range on the reading side, for example, Japanese Laid-Open Patent Publication No. 61-32649.
The method described in Japanese Patent Publication is known. In this method, an image to be read is divided into two optical axes, the two image pickup devices are set to have different sensitivities, and the read signals are arithmetically processed to obtain a wide dynamic range.

In this method, the dynamic range is expanded, but since the image pickup device requires two systems and a means for dividing the optical axis is required, the entire apparatus is complicated and adjustment of the optical axis is required, resulting in reliability. It has not been sufficiently recognized in the past that it is disadvantageous in terms of cost and equipment.

[0008]

In the above-mentioned conventional image input device, it is necessary to widen the dynamic range. In addition, in a certain type of conventional technology, a means for adding electrical calculation processing using a plurality of image pickup elements having different setting sensitivities is used in order to widen the dynamic range, but the apparatus becomes complicated and reliability is a problem. Has become.

The present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide an image reading apparatus having high reliability and a wide dynamic range.

[0010]

In order to achieve the above object, the structure of the first invention relating to the image input apparatus according to the present invention is a means for reading the same image a plurality of times and an image signal read a plurality of times. The same image is read a plurality of times, the obtained image signals are integrated, the signal-to-noise ratio is improved, and the dynamic range is widened.

According to the second aspect of the invention, means for changing the sensitivity characteristic of the same image pickup device is provided, the sensitivity is changed every time the image is read a plurality of times, and the obtained image signal is arithmetically processed to increase the dynamic range. Configured as a means of spreading.

According to a third aspect of the present invention, a plurality of photoelectric conversion elements included in the image pickup element are provided on the respective light ray input portions,
The light amount limiting means is provided, and the individual light amount limiting means is provided with means for controlling by the photoelectric conversion output of each image pickup element below the light amount limiting means.

[0013]

When the same image is read a plurality of times and the obtained image signals are integrated, the signal-to-noise ratio (S / N ratio) is improved and a wide dynamic range is obtained.

Further, if the same image is read a plurality of times with different sensitivity characteristics and the obtained image signal is arithmetically processed, a wide dynamic range of the input can be converted.

Further, the means for feeding back the incident light amount of each of the plurality of photoelectric conversion elements with the obtained light amount reduces the subsequent incident light amount when the incident light amount is large, and increases the subsequent incident light amount when the incident light amount is small. As a result, it has the effect of expanding the dynamic range.

[0016]

Embodiments of the present invention will now be described in detail with reference to the drawings.

FIG. 1 is a block diagram showing the internal structure of an embodiment of the image input apparatus according to the present invention. The image input device 1 includes a light source 10, a lens 20, a color separation filter 30,
CCD one-dimensional sensor 50, CCD sensor reading circuit 51, logarithmic conversion circuit 60, A / D conversion circuit 70, line memory 80, arithmetic circuit 81, image memory 82, system controller 90, external interface 110, reading condition setting circuit 52, etc. It is configured.

In FIG. 1, the image input apparatus 1 takes in an image recorded on the film 2 which has been photographed as an electric signal and sends it out from an external interface to an external device (eg computer).

Hereinafter, the outline of the entire apparatus will be described with reference to FIGS. 2, 3 and 4, and then the detailed description will be given by returning to FIG. 1 again.

FIG. 2 shows an example of color density characteristics of a positive photographic film used for general slide projection and the like. The brightness of the dynamic range of the input light quantity is recorded approximately linearly in a range of about three digits. The logarithmic display of the transmittance is the density, and the dynamic range 3 of the density means
It is 3 digits when converted to brightness.

FIG. 3 shows an example of sensitivity characteristics of a CCD line sensor which is a one-dimensional image pickup device. Although the position of the characteristic moves depending on the accumulation time Tint, the range of the dynamic range obtained under the same driving condition is about two digits in luminance. The other bright parts have a non-linear characteristic, and the dark parts are buried in the noise (dark current) of the device and cannot be extracted.

Here, for example, when the accumulation time is set to 20 ms, a characteristic such as characteristic A187 is obtained, and it is possible to convert from about 20 Lux to about 2000 Lux with the input illuminance into an electric signal. Further, for example, when the accumulation time is set to 50 ms, the characteristic B189 has about 2 Lux.
The range from the vicinity to around 200 Lux can be converted into an electric signal.

FIG. 4 is an explanatory view of the principle of expanding the reading dynamic range of the present invention.

As shown in FIG. 3, by changing the driving condition (accumulation time) of the image pickup device during reading, the conversion range of the image pickup device can be changed to change the sensitivity.
In FIG. 4, the output is displayed as data after A / D conversion, but it is basically the same as the display of the voltage in FIG.

That is, when the signal converted with the characteristic of increasing the sensitivity and the signal converted with the characteristic of decreasing the sensitivity are combined, a signal having the characteristic of a wide conversion range is obtained. Figure 4
As shown in FIG. 7, when the high-sensitivity characteristic B189 and the low-sensitivity characteristic A187 are added, a combined characteristic 190 is obtained. The final conversion characteristic 191 is obtained in accordance with the dynamic range of the output by multiplying the synthetic characteristic 190 by a constant coefficient. This makes it possible to obtain a dynamic range wider than the dynamic range of the image sensor itself.

Now, returning to FIG. 1, the operation of the embodiment according to the present invention will be described.

The light emitted from the light source 10 is sent to the film 2 through the infrared cut filter 12. Film 2
Are held by holding means (not shown), and their positions are fixed during the image capturing operation. The light passing through the film 2 is sent to the color separation filter 30 via the lens 20, and the color component selected by the filter is sent to the one-dimensional CCD sensor 50. Then, the image recorded on the film 2 is passed through an optical system such as the lens 20 to C
An image is formed on the light receiving surface of the CD sensor 50. The color filter 30 is selectively replaced by the separation filter replacement mechanism 31. The types of filters include, for example, a colorless (clear glass, etc.) filter, a plurality of ND filters for dimming, a red R filter for extracting color color components, a green G filter, a blue B filter, etc. ing. From the one-dimensional sensor 50, a CCD sensor reading circuit 51 is used to send out an image of one column captured as an analog signal. One-dimensional CCD sensor 50
The image formed in the movement range is decomposed line by line by the sequential movement of the one-dimensional sensor and finally two-dimensionally decomposed to be taken out as an image signal.

The one-dimensional sensor 50 is attached to a parallel moving table (not shown) which is a moving means, and can be moved by a moving mechanism 53 which moves this. During the image capturing operation, the moving mechanism 5 is moved according to the capturing speed.
3 is operated to move, for example, the parallel displacement table at intervals corresponding to the arrangement of the elements of the one-dimensional sensor in order corresponding to the reading operation of the sensor. When one screen of one color component has been captured, the next color component is captured, and this operation is repeated for a plurality of colors (for example, three colors) to complete the capture of the color image.

The extracted image signal is converted into a logarithmic conversion circuit 6
After passing 0, it is converted into a digital signal by the A / D conversion circuit 70. The image signal converted into the digital signal is temporarily stored in the line memory 80. The storage time, which is the reading condition of the CCD sensor at this time, is determined by the reading condition setting circuit 52.
Is set based on the command from the system controller 90. The system controller 90 also controls the one-dimensional sensor moving mechanism 53 that moves the CCD one-dimensional sensor 50.

That is, the system controller 90
It is possible to read the image at the same position a plurality of times without moving the one-dimensional sensor, and in that case, it is also possible to change the reading storage time and read at different storage times.

In the 1-line reading operation, the first reading is performed at the same position, for example, with the characteristics of high sensitivity (setting the accumulation time relatively long), and the image data of the read result is temporarily stored in the line memory 80. Put. Then, for example, with low sensitivity (set the storage time relatively short),
The second reading is performed, and the result of the high-sensitivity reading is sent to the arithmetic circuit 81, and the results of the second reading are added and multiplied by the coefficient, and then sent to the image memory 82.

After this one-line reading operation is performed, the one-dimensional sensor moving mechanism 53 is operated to move the one-dimensional sensor to the next one-line reading position, and the subsequent one-line reading operation is performed.

By doing so, it becomes possible to perform reading with a wide dynamic range of capture, as described above with reference to FIG.

In the above description, when the reading is divided into a plurality of times, the sensitivity is set to different reading conditions, but even under the same reading conditions, the noise components are averaged by a plurality of readings. Therefore, the signal-to-noise ratio (S / N
The ratio) is improved, and as a result, it is possible to increase the dynamic range of a dark portion, and it is almost effective for expanding the dynamic range.

FIG. 5 is a block diagram showing the internal structure of the second embodiment according to the present invention. The difference from the first embodiment shown in FIG. 1 is that an ND filter 150, which is a neutral density filter, can be inserted in the optical axis.
That is, when the system controller 90 drives the ND filter moving mechanism 151 that moves the ND filter 150 to move and insert the ND filter into the optical axis, the amount of light incident on the one-dimensional sensor 50 decreases, and as a result, the sensitivity decreases. It will fall.

As described in the first embodiment of FIG. 1, at the time of the first reading, the ND filter is not inserted and the reading is performed in a highly sensitive state. At the time of the first reading, the ND filter is inserted. Thus, the reading can be performed in a low sensitivity state, and after the reading, the read data can be processed twice to widen the reading dynamic range.

FIG. 6 is a perspective view showing the structure near the one-dimensional sensor of the third embodiment according to the present invention.

The one-dimensional sensor is composed of a plurality of storage type photoelectric conversion semiconductors 201 which are photoelectric conversion elements arranged in one line. Each of the storage type photoelectric conversion semiconductors has a small size, for example, 16 μm square, and a plurality of, for example, 2048, are arranged in a line to form a one-dimensional line sensor. A liquid crystal shutter 203 is provided on the storage type photoelectric conversion semiconductor via a polarizing film 202. As for the liquid crystal shutters 203, one liquid crystal shutter 203 is arranged on each element of the storage type photoelectric conversion semiconductors.
Further, another polarizing film 2 is formed on the liquid crystal shutter 203.
04 are provided. Light entering from the outside is polarized film 204, liquid crystal shutter 203, and polarized film 20.
The light then enters the storage-type photoelectric conversion semiconductor 201 via 2. Further, the polarizing film 204 and the polarizing film 202 are matched with polarized light in the same direction, and when an electric current is passed through the liquid crystal shutter 203 to change the polarization direction, the light incident from the outside is directed to the second polarizing film. Differently, it does not reach the storage type photoelectric conversion semiconductor 201. Further, by changing the current flowing to the liquid crystal shutter 203, the amount of light reaching the storage photoelectric conversion semiconductor 201 can be continuously changed.

FIG. 7 is a sectional view of the one-dimensional sensor 50 near the storage type photoelectric conversion semiconductor 201.

FIG. 8 is a circuit diagram showing a circuit configuration of one image pickup device portion.

Light incident from the outside is polarized film 20.
4, incident on the storage type photoelectric conversion semiconductor 201 through the liquid crystal shutter 203 and the polarizing film 202. In the storage-type photoelectric conversion semiconductor 201, incident light is converted into charges by the photoelectric conversion effect and accumulated. A high-impedance gate element 210 (field-effect transistor, FET, etc.) is provided on the output side of the storage-type photoelectric conversion semiconductor 201. When the gate element 210 is turned on, the storage element is stored in the storage-type photoelectric conversion semiconductor 201. The generated charges can be transferred to a CCD transfer element or the like and read out to the outside. Further, a high input impedance amplifier circuit 211 is connected to the output side of the storage photoelectric conversion semiconductor 201, and a voltage corresponding to the stored charges is output from the amplifier circuit 211. The output of the amplifier circuit is the liquid crystal shutter 203.
Is connected to. A control signal from the outside is connected to the differential input terminal 212 of the amplifier circuit 211.

When the image pickup device is constructed in this way, the amount of incident light is fed back, and it is possible to obtain a non-linear conversion characteristic. That is, when the amount of incident light is large, the storage-type photoelectric conversion semiconductor 2 per fixed time
The charge stored in 01 increases, so that the output voltage of the amplifier circuit 211 increases and the transmittance of the liquid crystal shutter 203 decreases. This transmittance decreases as the charge increases with time. On the other hand, when the amount of incident light is small, the output voltage of the amplifier circuit 211 does not increase much, the transmittance of the liquid crystal shutter 203 does not change much, and the amount of incident light does not decrease much over time. The transmittance changes continuously and non-linearly depending on the amount of incident light, so even in the case of an image with a wide dynamic range,
It can be accommodated within the range of the storage type photoelectric conversion semiconductor.

FIG. 9 shows an example of photoelectric conversion characteristics obtained when the liquid crystal shutter is fed back and in other cases.

The characteristic 250 that is fed back is obtained because the voltage applied to the liquid crystal shutter continuously changes according to the light amount. Since the voltage corresponding to the electric charge obtained from the storage photoelectric conversion semiconductor is applied to the liquid crystal shutter, the light amount changes continuously during the reading operation, and the light amount is too large to be captured by the storage photoelectric conversion semiconductor. Even in such a case, the amount of light decreases during the reading, so that the stored charges do not overflow. On the other hand, according to the characteristic 251 in the case of performing the conventional reading without feedback, the charge that linearly corresponds to the incident light amount is accumulated in the photoelectric conversion semiconductor, and when the light amount is equal to or more than a certain value, the reading accumulation is performed. It overflows during the time, and an image with more light cannot be read.

Returning to FIG. 8 again, a detailed description will be given.

When photoelectric conversion is performed once, the gate 210 is turned on and the charge of the storage type photoelectric conversion semiconductor 201 is read out. When the charge is read out and the charge is lost, the output of the amplifier circuit 211 is also lost, and therefore the voltage applied to the liquid crystal shutter 203 is also lost.
The transmittance is maximum. In this way, the next reading can be started.

Differential input terminal 21 for external control
When a certain voltage is set to 2, the output characteristic of the amplifier circuit 211 can be changed. That is, the amplification factor and offset of the amplifier circuit are changed to correct the variations in the characteristics of individual photoelectric conversion elements and liquid crystal shutters, and the characteristics of a plurality of elements are made to appear to be the same in the final output. be able to.

As described above, in the embodiment of the present invention, the image input device having the one-dimensional image sensor is used. However, another structure, for example, the two-dimensional sensor is used, or the one-dimensional image sensor is used. Two-dimensional sensor and two-dimensional sensor are used together, two-dimensional sensor and one-dimensional sensor are three in total, 4
Even if the number or role of sensors is changed, such as by using individual sensors, it is possible to change the dynamic range of reading by reading multiple times or limiting the amount of incident light from individual photoelectric conversion elements by feeding back. It is clear that they have the same effect.

Further, regarding the type of sensor, in the present embodiment, the one using the solid-state image pickup element has been described as an example.
It is obvious that the same effect can be obtained by another method such as a photoelectron storage tube (phototube) or the like that converts an equivalent light quantity into an electric quantity.

In the first and second embodiments, the image is read twice and the final output is obtained by the arithmetic processing. However, even if the number of readings is three or more, the same result is obtained. It is clear that the effect can be obtained.

[0051]

As described above, according to the first and second embodiments of the present invention, the dynamic range of a wide light amount of an image to be read has a narrow dynamic range of the reading range. Even with an image sensor, it is possible to widen the finally obtained dynamic range by reading multiple times, and it becomes possible to read all the information recorded in an image having a wide dynamic range. .

According to the third embodiment of the present invention, since the dynamic range of photoelectric conversion characteristics of the entire image pickup device can be changed, information recorded in an image having a wide dynamic range can be obtained. It becomes possible to read without leaving. Furthermore, according to the third embodiment of the present invention, correction of sensitivity nonuniformity (shading) such as variation of conversion characteristics of photoelectric conversion elements and the like is performed by a value preset in the liquid crystal shutter. Therefore, it is possible to realize an image pickup device having a reading characteristic with high accuracy and a wide dynamic range.

According to the present invention, the above effects can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing an internal configuration of a first embodiment according to the present invention.

FIG. 2 is a color density characteristic diagram of a general positive photographic film.

FIG. 3 is a diagram showing a difference in conversion characteristic due to a difference in driving condition of a general image pickup element.

FIG. 4 is an explanatory diagram of a method of expanding a reading dynamic range by performing a reading operation a plurality of times.

FIG. 5 is a block diagram showing an internal configuration of a second embodiment according to the present invention.

FIG. 6 is a perspective view showing the structure of an image sensor according to a third embodiment of the present invention.

7 is a cross-sectional view of the image sensor shown in FIG.

8 is a circuit diagram of one pixel of the image sensor shown in FIG.

9 is an explanatory diagram of photoelectric conversion characteristics of the circuit portion of FIG. 7.

[Explanation of symbols]

1 ... Image input device, 2 ... Image, 10 ... Light source, 20 ... Lens, 30 ... Color separation filter, 50 ... One-dimensional sensor, 9
0 ... System controller, 60 ... Logarithmic amplifier, 70
... A / D conversion circuit, 80 ... Line memory, 81 ... Arithmetic circuit, 82 ... Image memory.

Claims (5)

[Claims] 1. An image input device for converting an image into an electric signal, comprising: a holding unit for a medium having an image; an image pickup unit; and an image forming unit for forming an image from the medium having an image on the image pickup unit. 2. An image input device comprising: means for reading the same image a plurality of times; and means for accumulating image signals read a plurality of times. 2. The image input device according to claim 1, further comprising means for changing the sensitivity of the image pickup device, wherein when inputting a plurality of times, the images having different image storage times are input. Image input device. 3. The image input device according to claim 1, further comprising means for changing an incident light amount of the entire image pickup device, wherein an image with the incident light amount changed is input when the input is performed plural times. Image input device. 4. A plurality of solid-state image pickup devices for performing photoelectric conversion, wherein light quantity limiting means is provided on a light ray input portion of each image pickup element, and each light quantity limiting means is under the light quantity limiting means. An image pickup device characterized by being controlled by a photoelectric conversion output of each image pickup device in. 5. A plurality of solid-state image pickup devices for photoelectric conversion are provided, light quantity limiting means is provided on a light ray input portion of each image pickup element, and each light quantity limiting means is under the light quantity limiting means. An image input device using an image pickup device characterized by being controlled by photoelectric conversion output of each image pickup device in.