JP3311386B2 - Image processing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image processing apparatus for reading image information of an original image as a digital image obtained by dividing an image by an image sensor and performing information processing on the original image using the digital image. The present invention relates to an image processing apparatus suitable for use in a printing exposure apparatus that reads an original image on a negative color film and determines a printing exposure amount of the original image based on the image information.

[0002]

2. Description of the Related Art In general photography, the subject blue,
It is known that the average reflectance of the three primary colors of green and red (hereinafter, referred to as B, G, and R) is substantially constant. Therefore, the conventional photographic printing apparatus measures the average transmission density (LATD) of the entire area of the photographic original image, determines the exposure amount of photographic printing based on the average transmission density, and determines the B, G, and R colors of the photographic paper. The exposure amount given to the photosensitive layer is controlled to a constant value so as to produce a print with good color balance (called a LATD control method).

[0003] However, the above method has a drawback that an appropriate print cannot be obtained if the subject has a luminance distribution or a color distribution. For this reason, in recent high-performance photographic printing apparatuses, a negative image to be exposed is read by an image pickup device that performs color separation scanning on fine pixels, and an image characteristic value (for example, a negative transmission density or the like) of each pixel is measured. , The exposure amount is determined based on the measurement result, or LA
A method of correcting the exposure amount determined by the TD control is adopted.

[0004] Such an apparatus is generally called a scanner (automatic exposure amount control apparatus). The scanner forms an image of the original image on a part of the light receiving surface of the imaging unit, reads the image two-dimensionally, and measures the image characteristic value (for example, density) of each pixel. By appropriately combining them, an image characteristic value of the area divided on the screen can be obtained.

In a conventional apparatus, a one-dimensional or two-dimensional image sensor (for example, a CCD image sensor) having a plurality of light receiving elements is used as an image pickup means, and this image sensor is driven by a drive circuit, and the information output is performed. sampling,
And smoothing and converting it to image information. Then, this image information is A / D-converted using a clock of a constant frequency synchronized with the clock of the drive circuit, and written into an image memory to obtain digital image information.

[0006]

However, when an image is sampled by the image processing apparatus having the above configuration, the following problems occur. The size of the negative film to be imaged is plural types (for example, brownie size (6 × 9) to D).
ISC size), and there are also two types of vertical / horizontal directions for setting a negative in the reading unit.

In this case, in order to obtain a fixed number of pixels for an original image under all size conditions, it is necessary to perform sampling with reference to a negative screen having the smallest size.
For a large size negative screen, the number of pixels becomes excessive. Therefore, in order to convert the pixels in a large negative screen into a required number of pixels, a “rounding process” for averaging data between the pixels is required.

Since the rounding process requires a longer time as the number of pixels increases, once an image is read and the rounding process is performed by software or the like, the image processing speed is determined according to the number of pixels to be rounded. Has the disadvantage of becoming slow. Further, if this processing is to be performed by hardware, a complicated and high-speed circuit must be used. For this reason, conventionally, pixel data is thinned out from pixel data of an image sampled at a fixed interval to an appropriate number of pixels for the rounding process, thereby shortening the processing time. When sampled, the capacity of image memory is
It is always necessary for the number of pixels of the maximum size.If this thinning process is performed on an image sampled while maintaining a fixed relationship between the image sampling period and the image frequency characteristics, the frequency characteristics of the image information and the image sample There is a disadvantage that the relationship with the period differs. When the characteristic value is calculated from an image sampled with the sample period and the frequency characteristic fixed as described above, even if the density distribution of the original image is the same image,
There is a possibility that an image characteristic value obtained depending on the size of the original image may vary depending on the size of the original image. In particular, in the case of processing using data converted to density, subtle fluctuations (noise) of high-frequency components in high-density parts are emphasized by density conversion, which may greatly affect characteristic values.

As a method for dealing with such a problem, it is conceivable to enlarge or reduce the magnification of the optical system of the image pickup apparatus in accordance with the negative size and to always obtain a projection image of a fixed size. However, there is a problem in that it is difficult to reduce the size of the device to incorporate it into a photo printing device.

The present invention has been made to solve the above-mentioned problems, and an original negative film having a different format is provided.
It is an object of the present invention to provide an image processing apparatus that can always perform sampling under almost constant conditions, and that can perform inexpensive and high-speed processing.

[0011]

In order to achieve the above object, an image processing apparatus according to the present invention comprises: an image pickup section having an image sensor comprising a plurality of light receiving elements; and a read clock for sequentially extracting photoelectric conversion outputs for each element. The frequency band of the analog image signal is limited by a drive control unit that generates a signal, an image signal processing unit that amplifies the photoelectric conversion output and converts the signal into an analog image signal, and a filter that has a frequency band that can be switched by an external signal. A filtering unit, an image information conversion unit that samples an analog image signal that has passed through the filtering unit at a predetermined sample clock frequency and converts it into a digital image, and an image information storage unit that stores the digital image information. With this configuration, the image resolution can be adjusted according to the size of the original image.

An external signal designating the frequency band of the filter is selected according to the size of the original image to be imaged, so that digital image information having a constant resolution can be obtained regardless of the size of the original image. It was done. Further, an image pickup unit having an image sensor composed of a plurality of light receiving elements, a drive control unit for generating a read clock for sequentially taking out photoelectric conversion outputs for each element, and amplifying the photoelectric conversion outputs to convert them into analog image signals An image signal processing unit, a filter unit for limiting a frequency band of the analog image signal, and image information conversion for converting the analog image signal passed through the filter unit into a digital image by a sample clock whose frequency can be switched by an external signal. And an image information storage unit for storing the digital image information, so that the number of pixels to be sampled can be adjusted according to the size of the original image.

An external signal designating the frequency of the sample clock is selected according to the size of the original image to be imaged, so that digital image information having a fixed number of pixels can be obtained regardless of the size of the original image. It is intended to be.

[0014]

With the original image information output from the image sensor, the frequency of the sample clock is appropriately adjusted according to the negative size of the original image to sample the image data. Thus, the effective area of each original image can always be divided by a fixed number of pixels regardless of the negative size.

If the negative size of the original picture is greatly different, an unnecessary high frequency band is cut by applying a frequency filter according to the negative size of the original picture. This makes it possible to make the resolution of each negative size image approximately constant and sample the image characteristics at a predetermined sample frequency,
Image information of the same resolution can be obtained regardless of the size of the negative.

As described above, data having a constant image characteristic can be obtained from the minimum necessary data irrespective of the negative size, and the time required for pre-processing such as rounding is minimized.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to an embodiment shown in the accompanying drawings. In FIG. 1, the imaging unit 100 includes a two-dimensional image sensor 1 including a plurality of light receiving elements, an aperture S, and a lens L. The image sensor 1 includes:
The image of the negative film N illuminated by the light source P
It is configured to be able to input through a lens L.
On the light receiving surface of the image sensor 1, B, G, and R color filters are arranged, and for each photoelectric conversion element under each color filter, a charge proportional to the amount of received light can be output as photoelectric conversion information. I have. Here, as the two-dimensional image sensor 1, a CCD image sensor is usually used, but a MOS image sensor or the like may be used.

The image information processing section 200 includes a signal processing section 2,
An analog switch 4 and an image information filter unit 5 are provided. The signal processing unit 2 includes the image sensor (CCD)
The photoelectric conversion information of the three colors of B, G, and R output from 1 is separated for each color, the separated image information is sampled and held, amplified, and further, image information outputs 2a, 2
b and 2c are configured to be output to the analog switch 4. The analog switch 4 outputs the image information outputs 2a, 2b, and 2c for the primary colors through an image information filter unit (low-pass filter) 5 at the subsequent stage according to a command output of a scanning position decoder 10 described later.
The A / D converter 6 of FIG.

Here, the low-pass filter 5 includes, for example,
As shown in FIG. 2, the filters B ₁ , B ₂ , B ₃ having different cutoff frequencies f ₁ , f ₂ , f _3.
3 ... and a plurality prepared by the selection information from the CPU (not shown), and configured to switch the analog switch 5a. As a result, as described later, it becomes possible to select a frequency band according to the size of the original image.

Reference numeral 3 denotes a drive control unit for the image sensor 1. The drive control unit 3 supplies a charge transfer timing signal, a charge readout clock signal, and the like to the two-dimensional image sensor 1 to drive and control the CCD. In addition, a timing signal is sent to the signal processing unit 2 to appropriately control the output separation of the image information outputs 2a, 2b, and 2c. Further, the drive control unit 3 includes the image sensor 1
When reading image data from the CPU, a vertical synchronization signal 3a serving as a screen switching timing signal, a horizontal synchronization signal 3b serving as a scanning line switching timing signal, an image reading clock signal 3c, and the like can be respectively generated.

That is, as shown in FIG. 3, for example, as shown in FIG. 3, the drive control unit 3 is provided with a frequency dividing counter 31 for an image sensor and a frequency dividing counter for an image reading clock at a stage subsequent to an oscillator 30 for generating an original clock f _0. 32, the image sensor frequency dividing counter 31 divides the original clock into 1 / X and outputs it to the CCD drive timing signal generating section 33. The image reading clock frequency dividing counter 32 responds to the designation from the CPU. Accordingly, the frequency of the original clock can be divided at an arbitrary ratio (1 / Y).

The image information converter 300 includes an A / D converter 6 and a data converter 7. The A / D converter 6
Is converted into a digital value by the data conversion unit 7.
Is converted into a predetermined data format (for example, a LOG value corresponding to the density) and can be converted as an image characteristic value. In this case, the data conversion unit 7 is configured by, for example, a ROM table or the like. The output of the data converter 7 is recorded in the image memory 12 at the subsequent stage.

The image information storage section 400 includes a scanning line counter 8, a pixel counter 9, a scanning position decoder 10, and an image memory 12. A vertical synchronizing signal 3a and a horizontal synchronizing signal 3b are input from the drive control unit 3 to the scanning line counter 8, respectively. That is, for example, a 9-bit counter is used as the scanning line counter 8, and the clock (CLK) terminal receives and counts the horizontal synchronization signal 3b. Similarly, a vertical synchronizing signal 3a is similarly input to the clear (CLR) terminal of the scanning line counter 8, and the 9-bit counter is reset by the vertical synchronizing signal 3a so that switching of a screen can be detected. ing. The count output of the scanning line counter 8 is
At the same time as being output to the scanning position decoder 10, the addressing output of the image memory 12 (designating the number of scanning lines)
Has also become.

Reference numeral 9 denotes a pixel counter to which an image reading clock signal 3c and a horizontal synchronizing signal 3b output from the drive control unit 3 are input. That is,
For example, a 9-bit counter is used as the pixel counter 9, and similarly to the scanning line counter 8, the read clock signal 3c is received at its clock (CLK) terminal and can be counted. The horizontal synchronization signal 3b is input to a clear (CLR) terminal, and the 9-bit counter is reset by the horizontal synchronization signal 3b. The count output of the pixel counter 9 is also connected as an address line of the image memory 12 (designating the number of pixels on a scanning line).

The outputs of the scanning line counter 8 and the pixel counter 9 are supplied to the image memory 12 by separate address lines.
It is connected to the. Thus, any pixel data of the two-dimensional image sensor 1 can be stored in the image memory 12 without overlapping with other pixel data at a storage position determined by the scanning line count number and the pixel count number corresponding to the pixel. Can be memorized.

The output of the scanning line counter 8 (hereinafter referred to as a scanning line number) is input to the scanning position decoder 10. The scanning position decoder 10 classifies and selects the output of the scanning line counter 8 according to a predetermined algorithm. Further, the negative carrier identification information and the negative mask direction identification information are input to the CPU.

Next, a method of setting a low-pass filter and an image reading clock in the image information processing section 200 will be described. FIG. 4 shows various negative sizes (135F to DIS).
It is a principle figure showing signs that negative of C) is actually projected on an image sensor. In image sampling, it is necessary to obtain an image having the same number of pixels for each size. However, as a reference sampling condition, a low-pass filter having the widest band (= filter B ₁ ) cut-off frequency = f ₁ (Hz) ・ The sample clock for image reading is the one that has the largest number of pixels. Sampling frequency is set to S ₁ (Hz). Under this condition, a standard negative of each size is imaged, and a negative of each size is projected. It is assumed that the position to be performed is determined and the area is stored for each size. (This type of operation is called a setup operation.
-260135 "is known). With this operation, the projection position and size of the negative of each size are determined.

Here, first, the band of the low-pass filter 5 is selected. In this case, (in FIG. 4, DISC vertical size) lateral region that flies narrow size relative bandwidth is allocated a number large filter B ₁ (cutoff frequency = f
₁ Hz). Then, based on the B ₁ filter, whereas the other of each size, determines the filter according to the size of the horizontal width of the setup.

[0029] For example, in the case of 135F vertical cut-off frequency f ₂ which gives a suitable _{bandwidth, f 2 = f 1 × (} x 12 -x 11) / (x 22 -x 21) , and the closest to this value A filter having a band is selected. As a result, high-frequency components of image information that cannot be resolved in a narrow screen are cut, and the horizontal frequency characteristics (resolution) can be made substantially uniform for each size.

Next, a method of setting the image reading clock will be described. If the low-pass filter is selected as described above, the resolution of each size becomes substantially constant. Here, when sampling, the number of pixels (x
_In order to obtain a sample image with the same number of pixels on the basis of ₁₂ −x ₁₁ ), the sample frequency may be changed for each size. That is, in the case of 135F vertical frequency of the sample clock of the data conversion section 7 is set so as to be _{S 2 = S 1 × (x} 12 -x 11) / (x 22 -x 21).

Similarly, on the 135F side, S ₃ = S ₁ × (x ₁₂ −x ₁₁ ) / (x ₃₂ −x ₃₁ ). In other words, on small screens, the sample interval should be tight,
By reducing the size of a large screen, image information of the same number of pixels is obtained while performing appropriate thinning processing according to the size of the screen.

As described above, the reading of analog image information from the CCD and the sampling of digital image information are performed under the same conditions regardless of the size of the original image (even if the individual bands and clock frequencies are different, Are the same). In the above description, the sample clock frequency and the frequency band of the filter are always set for each negative size. However, the frequency S of the sample clock is always S> 2 × f with respect to the cutoff frequency f of the filter B. In a region where the following relationship is maintained, a method of adjusting only the sample clock without changing the frequency filter may be used in principle.

Next, a photographic printing apparatus to which the image processing apparatus of the present invention is applied will be described with reference to a perspective view of FIG. In FIG. 5, light emitted from a light source lamp 20 is configured to illuminate a negative film N placed on a negative carrier 24 after being diffused by a mirror tunnel 23. The light transmitted through the negative film N passes through an imaging lens 25 and a shutter 26 for controlling exposure to a printing paper 28,
After being reflected by the reflection mirror 27, an image is formed on the photographic paper 28. A filter 21 for preventing heat from the light source is provided between the light source 20 and the mirror tunnel 23.
A cut filter 22 for selectively cutting each light of B, G, and R is provided.

A LATD photometric sensor (photodiode) 29 for measuring the density of the negative film N is disposed directly above the negative carrier 24. Similarly, the image processing apparatus 30 of the present application, which incorporates the two-dimensional image sensor 1 for reading a negative image, is disposed near the negative carrier 24 at an appropriate position. The image reading device 30 is provided with a light control means (aperture S) and an image forming lens L so that an image of the negative film N is formed on the sensor 1 with a predetermined light amount. It is on the street.

In the above embodiment, first, the photographic negative film N is set on the negative carrier 24. LATD composed of B, G, R photodiodes on the image on the negative N
Photometry is performed by the photometric sensor 29, and the average amount of transmitted light of the film is measured to determine the basic exposure. Next, the two-dimensional image sensor 1 of the imaging unit 100 of the apparatus 30 of the present application divides and measures the original image of the negative film N for each small pixel and obtains the divided metering data. The divided photometric data is extracted from the imaging unit 100 by the read clock signal of the drive control unit 300, and is shaped into analog image information by the signal processing circuit 2 of the image information processing unit 200. Then, the high frequency component of the analog image information is appropriately cut by the image information filter unit 5 according to the size of the original image. That is, a small-size original image passes a wide-band signal containing high-frequency components, and a large-size original image passes a narrow-band signal containing many low-frequency components only, thereby keeping the horizontal resolution of each size constant. .

The image information thus obtained is digitized by the A / D converter 6 in the image information converter 300, and then sampled by the data converter 7 using a sample clock. At this time, the frequency of the sample clock is variable according to the screen size, and the sampling interval is adjusted to be small on small screens and sparse on large screens. , Image information of the same number of pixels can be obtained.

As described above, digital image information of the same number of pixels obtained from the original image of each size is stored in the image memory 12 of the image information storage unit 400. Then, based on the standardized digital image information, image processing for searching for characteristics of the original image is performed, and an exposure correction amount for the previous basic exposure amount is obtained based on the result. The final exposure time is determined by adding this correction amount to the basic exposure time. After the exposure time is determined, the shutter 26 is opened and the printing paper 2
Exposure to 8 starts. After the exposure time for each color has elapsed, the cut filter 22 is inserted into the optical path, and when the predetermined exposure time has elapsed for all three colors, the shutter 26 is closed to end the exposure.

[0038]

As described above, the image processing apparatus according to the present invention comprises an image pickup section having an image sensor composed of a plurality of light receiving elements, and a drive control section for generating a read clock for sequentially taking out the photoelectric conversion output of each element. An image signal processing unit that amplifies the photoelectric conversion output and converts it into an analog image signal; a filter unit that limits the frequency band of the analog image signal by a filter having a frequency band switchable by an external signal; Since the analog image signal having passed through the digital image information is sampled at a predetermined sample clock frequency and converted into a digital image, and an image information storage unit that stores the digital image information, The image resolution can be adjusted according to the size.

Further, since the external signal designating the frequency band of the filter is selected according to the size of the original image to be imaged, its image resolution can be kept constant irrespective of the size of the original image. Further, an image pickup unit having an image sensor composed of a plurality of light receiving elements, a drive control unit for generating a read clock for sequentially taking out photoelectric conversion outputs for each element, and amplifying the photoelectric conversion outputs to convert them into analog image signals An image signal processing unit, a filter unit for limiting a frequency band of the analog image signal, and an analog signal that has passed through the filter unit is sampled by a sample clock whose frequency can be switched by an external signal, and is converted into a digital image. With the configuration including the image information conversion unit and the image information storage for storing the digital image information, the number of pixels to be sampled can be adjusted according to the size of the original image.

Further, since the external signal designating the frequency of the sample clock is selected according to the size of the original image to be imaged, the external signal is not affected by the size of the original image as long as the frequency band of the image is lower than the frequency of the sample clock. Digital image information of a fixed number of pixels can be obtained. Further, by combining the control of the filter unit and the control of the sample clock to select the frequency band and the sample clock frequency of the filter unit according to the size of the original image to be imaged, regardless of the size of the original image ,
Digital image information with a fixed resolution and a fixed number of pixels can be obtained.

As a result, there is an excellent effect that it is possible to provide an image pickup apparatus which can always sample original negative films having different formats under a constant condition, and which can perform inexpensive and high-speed processing.

[Brief description of the drawings]

FIG. 1 is a block diagram of a device of the present application.

FIG. 2 is a principle diagram of selection of a low-pass filter.

FIG. 3 is a principle diagram showing frequency setting means for a read clock and a sample clock.

FIG. 4 is an explanatory diagram showing an effective imaging area for a CCD.

FIG. 5 is a perspective view of the entire configuration of a photographic printing apparatus to which the present invention is applied.

[Explanation of symbols]

 Reference Signs List 1 imaging unit (two-dimensional image sensor, CCD) 2 signal processing unit 3 image sensor drive control unit 4 analog switch 5 image information filter unit (low-pass filter) 6 data conversion unit 7 image memory 8 scanning line counter 9 pixel counter 20 image memory Reference Signs List 30 oscillator 31 frequency division counter (for CCD drive control) 32 frequency division counter (for image reading sample clock) 100 imaging unit 200 image information processing unit 300 image information conversion unit 400 image information storage unit

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G03B 27/72-27/80

Claims (4)

(57) [Claims] 1. An imaging unit having an image sensor comprising a plurality of light receiving elements, a drive control unit for generating a read clock for sequentially extracting photoelectric conversion outputs for each element, and an analog image signal obtained by amplifying the photoelectric conversion outputs An image signal processing unit for converting the analog image signal into a signal having a frequency band switchable by an external signal; a filter unit for limiting the frequency band of the analog image signal; An image processing apparatus comprising: an image information conversion unit that samples at a frequency and converts it into a digital image; and an image information storage unit that stores the digital image information. 2. The image processing apparatus according to claim 1, wherein the external signal designating a frequency band of the filter is selected according to an original image size of an imaging target. 3. An image pickup unit having an image sensor comprising a plurality of light receiving elements, a drive control unit for generating a read clock for sequentially taking out photoelectric conversion outputs for each element, and an analog image signal by amplifying the photoelectric conversion outputs An image signal processing unit for converting the analog image signal into a digital image, and a filter unit for limiting the frequency band of the analog image signal. An image processing apparatus, comprising: an image information conversion unit that converts the digital image information; and an image information storage unit that stores the digital image information. 4. The image processing apparatus according to claim 3, wherein the external signal specifying the frequency of the sample clock is selected according to the size of the original image to be imaged.