JP2944674B2 - Image reading device - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image reading apparatus that reads a document image such as a film by photoelectric conversion, and more particularly to an image reading apparatus that performs automatic focus control.

[Prior Art] When reading a light-transmissive original such as a film using a color sensor, a color image reading apparatus that performs automatic focus control, as shown in FIG. Autofocus data reflecting the sharpness is sampled, and automatic focus control is performed based on the data.

[Problems to be Solved by the Invention] However, calculating the data for autofocus for all the projection lens angles requires a large amount of calculation time, and a faster autofocus for reading a light-transmitting original is required. A control method is needed.

[Means for Solving the Problems] The present invention provides a sensor for reading an image obtained through a taking lens and outputting an image signal, a moving means for moving the taking lens, and a moving means for moving the taking lens by the moving means. First calculating means for calculating a parameter reflecting the sharpness of an image using an image signal output from the sensor while moving; and calculating the first calculating means for the photographing lens by the moving means. A second calculating means for calculating a parameter reflecting the sharpness of an image using an image signal output from the sensor while moving more finely than in a case, and according to calculation results of the first and second calculating means. Control to adjust the focus of the photographing lens, and to the second calculating means according to the parameters calculated by the first calculating means. Control means for setting the number of pixels of the sensor used for calculating the parameter.

[Operation] According to the present invention, a parameter that reflects the sharpness of an image is calculated by the first calculation unit using the image signal from the sensor obtained while moving the shooting lens, and the first calculation unit calculates the shooting lens. A parameter reflecting the sharpness of an image is calculated by a second calculating means using an image signal from a sensor obtained while moving finer than in the case of performing a calculation by a means, and a calculation by the first and second calculating means is performed. In accordance with the result, control is performed to adjust the focus of the photographing lens, and the number of pixels of the sensor used for calculating the parameters by the second calculating means is determined in accordance with the parameters calculated by the first calculating means.

EXAMPLES Hereinafter, the present invention will be described with reference to examples.

FIGS. 1 to 12 show a first embodiment of the present invention, and FIGS. 1 and 2 show the best features of the present invention.

FIG. 1 is a block diagram of the image reading apparatus. 1001
Is a CCD for reading B (blue) of the three primary colors from the input optical image, 1002 is a CCD for reading G (green), 10
03 is a CCD for reading R (red), 1004 to 1006 are amplifiers for input color CCD signals from the three CCDs, 1007
1009 is an analog / digital (A / D) converter for analog signals from the three amplifiers, and 1010 to 1012 are the three A / D converters.
A buffer memory for transferring the A / D converted color digital signal from the / D converter to the microprocessor 1015. Reference numeral 1013 denotes a color signal processing circuit that converts input color signals from the three A / D converters 1007 to 1009 into signals for output to a printer (1017) by masking operation, gamma conversion, and the like. Reference numeral 1014 denotes a stepping motor, which rotationally drives the projection lens 1018 to perform focus control. Reference numeral 1015 denotes a microprocessor, which performs calculation of a sampling parameter S for automatic focus control, control of a lamp light power supply 1016, driving of a stepping motor 1014, and the like. 1016 is lamp 10
Power supply for controlling the light amount of 16A, 1017 is a color printer, 101
Reference numeral 8 denotes a projection lens for controlling the focal length, and reference numeral 1019 denotes a limit switch, which gives a reference point when the projection lens rotates.

FIG. 2 is a processing flow chart relating to the microprocessor 1015 for automatic control.

First, at 201, the scanner motor 810 (FIG. 8) is driven to set a reading position at the center of the Fresnel lens 708.

Next, at 202, the amount of lamp light for irradiating the film is controlled (by the procedure shown in FIG. 12 described later).

Next, at 203, the projection lens 1016 is rotated to the position of the limit switch 1019.

Next, at 204, sampling data (AF data = S value) for automatic focus control is calculated. The AF data is a parameter that reflects the sharpness of the target image.
The sum of squares S of the difference between adjacent pixels shown in the figure is calculated for the G (green) signal. In this embodiment, the input color sensor 809 uses a three-line parallel sensor as shown in FIG. The lens 808 shown in FIG. 8 focuses light on the CCD 809, and the lens 808 is the middle sensor (G signal in this embodiment) among the three sensors arranged in parallel.
It is controlled by focusing on. Therefore, the G signal has the highest spatial resolution. The number of pixels in the main scanning direction on the sensor corresponding to the projection plane of the Fresnel lens 708 is about 3000 pixels, and the central 500 pixels in the main scanning direction of the Fresnel projection plane are to be calculated.

Next, at step 205, the stepping motor 1014 is driven by N pulses to rotate the projection lens 1014. In this embodiment, N =
10 and the 3 ° projection lens 1014 rotates per pulse.

Next, at 206, sampling data (AF data) for automatic focus control is calculated.

Next, in 207, the magnitude of the previously calculated AF data and the currently calculated AF data are compared, and L times (in this embodiment, L times
= 3) If the AF data value decreases continuously (point P ₃ shown in FIG. ₃ ), the process of 209 is performed; otherwise, the process of 205 is performed until the above is executed M times ((208)). Return to processing.

Accordingly, when the rotation angle of the projection lens 1014 is larger than the focus position, the calculation for the automatic focus control can be omitted.

The sample point (P ₁ shown in FIG. 3) next to the point (P ₁ shown in FIG. 3) indicating the maximum value of the AF data calculated in 209
The rotation position of the projection lens 1014 is controlled to a position corresponding to ( ₂ points).

Assuming that the AF data value measured at the ith (i = 0,1 ,,, M) th at 210 is S (i), ΔS _MAX = MAX [| S (i + 1) −
It is determined whether or not S (i) |] is greater than a predetermined constant value α. If ΔS _MAX > α, the process of 211 is performed. If the condition is not satisfied, the process of 212 is performed.

At 211, the number of AF data calculation target pixels is set to 500 pixels.

In step 212, the number of AF data calculation target pixels is set to 3000 pixels.

ΔS _MAX is ΔS _MAX ≒ 0 when the target image is quite flat
, And takes a large value when a sharp edge exists in the target image. Therefore, when ΔS _MAX <α, it can be considered that there is no sharp edge in the AF data calculation target pixel. In that case, by increasing the number of AF data calculation target pixels, more accurate automatic focus control can be performed. .

In step 213, the AF data S value is calculated according to the number of AF data calculation target pixels set in step 211 or 212.

In step 214, the stepping motor 1014 is driven to rotate the projection lens 1014 by one pulse.

In 215, the processes of 213 to 215 are repeated T times (T = 20 in this embodiment).

At 216, the projection lens position (J _{1 in} FIG. 3) which is the maximum value of the AF data S values obtained in the processes 213 to 215 described above.
Rotate the projection lens to point).

FIG. 3 is a line graph displaying a value of the AF data S value (sum of squares of the difference between adjacent pixels) corresponding to the rotation angle of the projection lens. The line graph at the top of FIG. 3 is shown in FIGS.
Calculated while roughly rotating the projection lens 1018
In the graph display of the AF data S value, the line graph at the bottom of FIG. 3 is a graph display of the AF data S value calculated by finely rotating the projection lens 1018 in the processes 213 to 215.

FIG. 4 is an external view of the three-line parallel color sensor 809. The imaging lens 80 is installed so as to be parallel to the surface of the document to be read, and focuses on the G signal in the middle.
8 has been adjusted.

FIG. 5 shows the size of the aperture of each pixel of the three-line parallel color sensor 809. 501 is a B (blue) line sensor, 502 is a G (green) line sensor, 5
03 is an R (red) line sensor. The B line sensor has low sensitivity and low aperture resolution in the sub-scanning direction because the aperture size in the sub-scanning direction is larger than that of the other R and G line sensors in order to compensate for each other.

FIG. 7 is an external view of the film reading device.
701 is a reading unit (scanner unit), 702 is a lamp
Projector unit with built-in condenser lens, etc.
703 is a film holder for setting a film, 705 is a belt for transmitting the rotation of the stepping motor to the projection lens 1018, 704 is a pulley directly connected to the stepping motor 1014, 706 is a platen glass, 707 is a reflection mirror, and 708 is a film image. Is a Fresnel lens for forming an image on a reading device inside the scanner.

FIG. 8 is a sectional view of the film projection system of the embodiment. The film image projected from the projector unit 702 is reflected by the reflection mirror 707, and the mirror 80 is reflected by the Fresnel lens 708.
Focused on 5. The images reflected by the mirrors 805 to 807 are formed on the CCD sensor 809 by the imaging lens 808. The CCD 809 is a three-line parallel color sensor shown in FIG. The scanner motor 810 drives the mirrors 805 to 807 to move the document reading position in the sub-scanning direction.

FIG. 10 is a graph display example of the AF data S value when the original image shown in FIG. 9 is read.

FIG. 11 is a timing chart for calculating the driving pulse of the stepping motor 1014 and the AF data S value.

FIG. 12 is a processing flowchart of the microprocessor 1015 regarding the lamp light amount control of the halogen lamp 803. In step 1201, a lamp power supply 1016 is controlled to set a lamp voltage for irradiating a film to a predetermined value. The average value of the sensor signal values read at 1202 is determined, and given value β
(Β = 200 in this embodiment) is determined, and the lamp light amount of the halogen lamp 803 is reduced until the above condition is satisfied (1203, 1204).

[Other Embodiments] Figs. 14 to 15 are drawings relating to a second embodiment of the present invention.

In the first embodiment, one of a plurality of color sensor signals is used as a signal for extracting a parameter for performing automatic focus control.

In the second embodiment, automatic focus control is performed using parameters extracted from three RGB signals.

In the case of the first embodiment, when a specific color signal of a film image has a biased edge component (for example, an edge signal is present only in blue with high saturation), parameters for automatic focus control have good values. May not be. In the second embodiment, the automatic focus control is performed by using the parameters extracted from the three signals of the RGB signals, so that even when the edge component is unevenly present in a specific color signal of the film image, a good automatic focus is achieved. The purpose is to enable control.

 FIG. 14 is a processing flow chart of the second embodiment.

At 1401 and 1402, the sum of squares S _R , S _G , and S _B of the difference between adjacent pixels is obtained for each of the R signal, the G signal, and the B signal.
(14A, 14B, 14C, and 14D are similar to FIGS. 201, 202, 203, and 205).

In 1403, if the value of S _sum = (S _R + S _G + S _B decreases continuously L times, the process of 1404 is performed (otherwise, 14D, 1402, 1
Execute 403 M times (14E) and proceed to 1404).

At 1404, as shown in FIG. 15, the maximum value V ₂ of the AF data
To control the rotation angle of the next sample value V ₃ position to the projection lens 1018.

Assuming that the AF data value measured at the i (i = 0, 1,, M) th in 1405 is S _R (i), S _G (i), S _B (i), ΔS _RMAX = MAX [| S _R (I + 1) −S _R (i) |] ΔS _GMAX = MAX [| S _G (i + 1) −S _G (i) |] ΔS _BMAX = MAX [| S _B (i + 1) −S _B (i) |] The signal giving the maximum value among the defined ΔS _RMAX , ΔS _GMAX , and ΔS _BMAX is determined. In 1406, the AF data S value of the single signal determined in 1405 is calculated. The rotation of the projection lens 1018 is finely controlled using the AF data (14F, 14G, 14H) calculated from the signal values (14I to 14K; these are the same as FIGS. 214 to 216 in FIG. 2).

According to the above-described processing, the first embodiment requires more execution time, but also enables good automatic focus control when a specific color signal of a film image has an uneven edge component.

FIG. 16 relates to a third embodiment of the present invention.
In the second embodiment, when the rotation of the projection lens 1018 is finely controlled using the AF data, the automatic focus control is performed using one of a plurality of color sensor signals. In the embodiment shown in FIG. 1601 (FIGS. 16A to 16I are the same as in FIGS. 14A to 1404), MAX (ΔS _RMAX , ΔS _GMAX , ΔS _BMAX )> Z (1) It is determined whether or not the following condition is satisfied. If the condition of Expression 1 is not satisfied, the rotation of the projection lens 1018 is finely controlled using three color signals of RGB signals. That is, AF data is sampled from each of the R, G, and B signals in 1602, the stepping motor is driven N pulses in 1603, and these are executed M times (1604).
The projection lens is rotated to the maximum value of the AF data obtained in 1604.

On the other hand, when 1601 satisfies the condition of Expression 1, 1606 to
At 1610, the same processing as in FIGS. Thereby, even when the edge component of the target original film is weak, the automatic focus control can be performed more stably.

[Effects of the Invention] As described above, according to the present invention, it is possible to provide an image reading apparatus capable of performing automatic focus control quickly and accurately. Also, when performing detailed focus adjustment, it is possible to set an appropriate number of pixels, and to efficiently and reliably perform focus adjustment using the pixels of the set number of pixels.

[Brief description of the drawings]

FIG. 1 is a block diagram of a first embodiment of the present invention, FIG. 2 is a processing flow chart relating to a microprocessor 1015, and FIG. 3 is a line graph showing a value corresponding to a projection lens rotation angle of an AF data S value. 4 is an external view of the three-line parallel color sensor 809, FIG. 5 is a diagram showing the size of the aperture of each pixel of the three-line parallel color sensor 809, and FIG. FIG. 7 is an external view of a film reading apparatus, FIG. 8 is a cross-sectional view of a film projection system, FIG. 9 is a film original image, FIG. 10 is a graph display of AF data S value, FIG. FIG. 12 is a diagram showing a drive pulse of the stepping motor 1014 and a timing chart for calculating the AF data S value. FIG. 12 is a process flow diagram relating to lamp light quantity control. FIG. 13 is a process flow diagram of a conventional example. FIG. Example processing flowchart, FIG. FIG. 16 is a line graph showing a value corresponding to a projection lens rotation angle of the AF data S value of the second embodiment. FIG. 16 is a flowchart showing the process of the embodiment of FIG.

──────────────────────────────────────────────────続 き Continuation of front page (51) Int.Cl. ⁶ identification code FI H04N 5/253 G03B 3/00 A (58) Field surveyed (Int.Cl. ⁶ , DB name) H04N 1/04 H04N 5 / 232 H04N 5/253 G03B 27/34 G02B 7/11 G03B 3/00

Claims (6)

(57) [Claims] A sensor for reading an image obtained through a photographing lens and outputting an image signal; a moving unit for moving the photographing lens; and an output from the sensor while moving the photographing lens by the moving unit. First calculating means for calculating a parameter reflecting the sharpness of the image using the image signal to be obtained, and moving the photographing lens by the moving means more finely than when performing the calculation by the first calculating means. Second calculating means for calculating a parameter reflecting the sharpness of an image using an image signal output from the sensor; and adjusting the focus of the photographing lens according to the calculation results of the first and second calculating means. And the calculation of the parameter by the second calculation means is performed in accordance with the parameter calculated by the first calculation means. Control means for setting the number of pixels of the sensor to be used. 2. The image reading apparatus according to claim 1, wherein said control means determines that the value of a parameter reflecting the sharpness of the image calculated by said first calculation means decreases continuously for a predetermined number of times. And controlling the second arithmetic means to perform an arithmetic operation. 3. The image reading apparatus according to claim 1, wherein said first and second calculation means convert the image signal from the image signal output from the sensor as a parameter reflecting the sharpness of the image. An image reading apparatus for calculating a sum of squares of a difference between adjacent pixels. 4. The image reading apparatus according to claim 1, wherein said sensor is a color sensor. 5. The image reading apparatus according to claim 4, wherein said color sensors are a plurality of line sensors arranged in parallel to read different color information. 6. The image reading apparatus according to claim 4, wherein said first calculating means calculates a square of a difference between adjacent pixels of the color sensor from a plurality of color image signals output from the color sensor. The second computing means computes the sum for each color, and the second computing means calculates the sum of the sharpest color image signal among the signal components of each color computed by the first computing means, and calculates the sum of the adjacent pixels of the color sensor. An image reading apparatus for calculating a sum of squares of a difference.