JPH0253010A - Picture reader - Google Patents

Abstract

PURPOSE:To automatically adjust a focal point all the time with high accuracy by providing a maximum value extracting means and an automatic focusing control means which controls a focusing means based on information on the sharpness of a point where the sharpness maximum value extracted by the maximum value extracting means exceeds a fixed level and which adjusts a focal point. CONSTITUTION:With the aid of a picture signal in an auto-focusing (AF) picture reference area, which is obtained in such a way that an image pickup element B photoelectrically converts when an image on a transmitting original H is focused, a sharpness detecting means C detects the sharpness of an image in the AF picture reference area. The maximum value extracting means E extracts maximum values of sharpness by changing locations where an image pickup lens A focuses plural AF image reference areas. Based on information on the location where the extracted maximum value of sharpness exceeds a predetermined specific level, the focusing means D is controlled to adjust a focal point. Therefore, a part of high sharpness of an imprinted image is mainly focused. Thus, the entire sharpness of an output picture can be substantially enhanced.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an image reading device that scans a transparent original such as a photographic film to read an image, and particularly relates to an automatic focus adjustment technique for this image reading device.

(Prior Art) Conventionally, this type of device for reading transparent originals such as 35 mm photographic film has been developed by, for example, winding the film around a rotating drum, rotating the drum, and moving a photoelectric conversion unit along the drum. There are drum scanners that perform scanning, but in this case autofocus was not particularly necessary.

[Problems to be Solved by the Invention] However, when reading a transparent original such as a 35+nl11 photographic film with a high resolution using conventional mounting, there are the following problems.

First of all, in most cases, reversal film (positive film) is stored one by one in a mount (mounting board), but the thickness of the mount is not constant, so if you try to handle the film while it is mounted, the film surface will be Since the position in the optical axis direction varies within a range of several millimeters, focus adjustment is required in order to read an image without blur.

Furthermore, since both mounted and unmounted films tend to curve under normal conditions, it is advisable to keep the position of the film surface constant.

Therefore, in order to solve these problems, conventional methods generally involve attaching the film to the glass surface or sandwiching it between two pieces of glass to accurately position the film surface and prevent the film from curving. However, in this case, it is necessary to take out the mounted film from the mount and attach it to the glass, which is a cumbersome and time-consuming process, and Newton rings may occur due to sandwiching the film between the glass. Another disadvantage is that dust tends to adhere to the glass surface or film.

In addition, manually adjusting the focus for each mount is laborious and time-consuming, and it is difficult to focus accurately.

On the other hand, due to various aberrations such as field curvature, astigmatism, and chromatic aberration of the first most image lens, the focal position for each point on the film surface varies, for example, R (red), G (green), etc.
There was a problem in that the focal position of the color-separated image, which was separated into three colors of B (blue), was shifted.

Furthermore, the image of the subject on the film is originally sharp, that is, well focused at the time of shooting, and the image itself contains many high-frequency components and other parts that do not, so when reading the image, Even if the film is in focus, if the focus is on an area that is not sharp, high sharpness cannot be obtained and automatic focus adjustment cannot be performed with high accuracy.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems and provide an image reading device that can always perform automatic focus adjustment with high precision.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an imaging lens that forms an image of a transparent original illuminated by an illumination means, and a photoelectric conversion method for the image formed by the imaging lens. A plurality of predetermined AFs obtained by photoelectric conversion using an image sensor and an image sensor
sharpness detection means for detecting the sharpness of an image in the F image reference area based on an image signal of one area in the two-purpose image reference area; and a focus adjustment means for adjusting the focus by moving the imaging lens. and maximum value extraction means for sequentially extracting the maximum value of sharpness obtained from the sharpness detection means for the plurality of image reference regions for F while changing the focus position by the focus adjustment means, and the maximum value extraction means. The present invention is characterized by comprising automatic focus adjustment control means that controls the focus adjustment means to adjust the focus based on information on the sharpness of a portion where the maximum value of the extracted sharpness exceeds a predetermined certain level. do.

[For production]

With the above configuration, the present invention focuses on an image on a transparent original (
A obtained by photoelectric conversion using the image sensor when focusing
Based on the image signal of the F image reference area, the sharpness of the image in the revised image reference area is detected, and the above-mentioned sharpness is adjusted while changing the focal position of the imaging lens for multiple AF image reference areas. The maximum sharpness value is extracted, and the focus adjustment means is controlled based on the information on the sharpness of the area where the extracted maximum sharpness value exceeds a predetermined level. The sharpness of the crowded image is focused on the sharpest parts of the image, thereby substantially increasing the overall sharpness of the image signal.
The quality of the output image is improved.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows the basic configuration of an embodiment of the present invention. In this figure, A is an imaging lens that forms an image of a transparent original H illuminated by illumination means G. B is an imaging element that photoelectrically converts the image formed by the imaging lens A. C) Most image element B
Based on the image signal of one area among the plurality of predetermined AF image reference areas obtained by photoelectric conversion at
This is a sharpness detection means for detecting the sharpness of the image in the image reference area. D is a focus adjusting means that adjusts the focal position by moving the imaging lens A.

Maximum value extraction means E extracts the maximum value of sharpness obtained from the sharpness detection means C for a plurality of revised image reference areas while changing the focal position of the imaging lens A using a focus adjustment means. F is an automatic focus adjustment control means, and based on the information on the sharpness of the point where the maximum value of sharpness extracted by the maximum value extraction means E exceeds a predetermined certain level,
Focus adjustment is performed by controlling the focus adjustment means.

FIG. 2 shows a specific circuit configuration of an embodiment of the present invention.

In this figure, 3001 is a light source (lamp) for illuminating a transparent original, 3002 is a heat ray absorption filter that removes heat rays from the light rays from the light source 3001, and 3003 is a filter 3.
This is an illumination optical system that converts illumination light passing through 002 into a parallel light beam. 3004 is a sub-scanning drive table that moves the transparent original in the sub-scanning direction; 3005 is a rotating table that rotates the transparent original; 300
6 is a film holder for storing a transparent original, and 3007 is a transparent original such as a 35+nm photographic film. 30
08 is a movable mirror that switches the optical path of the light beam (original image) that has passed through the transparent original 3007, 3009 is a mirror that deflects the optical path of the original image, and 301O is a first imaging lens that forms the original image that has passed through the mirror 3009. be.

3011 is a projection lens for projecting the original image reflected by the movable mirror 3008; 3012 is a mirror that deflects the optical path; 3013 is a mirror that deflects the same optical path; 3014
is a screen serving as a monitor on which the original image that has passed through the mirror 3013 is projected. 3015 is the screen 3014
3016 is the screen 3
014 is a touch panel that manually controls the trimming area.

3017 is a lamp holding member that supports the light source 3001. 3018, 3019, and 3020 are CCO positioning mechanisms, 3021 are three-color separation prisms that separate the transparent original image formed by the imaging lens 3010 into three colors of J, G, and B, and 3022, 3023, and 3024 are prisms 3021, respectively. C
This is a CD line sensor, and this CCD line sensor has a corresponding CCD alignment mechanism: 1018.3019.302
0 allows fine adjustment of the reading position.

3025 is CCD line sensor 3022, 3023.3
Amplify the analog output of 024 and convert it to 8/D (analog/
3026 is an adjustment signal generation source that generates a standard signal for adjustment to the analog circuit 3025; 3027 is an adjustment signal generation source for R, G, and B digital image signals obtained from the analog circuit 3025; 3028 is a shading correction circuit that performs shape ink correction on the output signal of the dark correction circuit 3027; 3029 is a pixel that corrects pixel shift in the main scanning direction with respect to the output signal of the shading correction circuit 3028; A shift correction circuit 3030 converts the R, G, and B signals that have passed through the pixel shift correction circuit 3029 into Y (yellow), M (magenta), and C (cyan) depending on the output device.
This is a color conversion circuit that converts into each color signal. Also,
3031 is a lookup table (LIT) that performs LOG conversion and γ conversion of the signal.

3032 is a minimum value detection circuit that detects the minimum value of the output signal of the lookup table 3031, and 3033 is an under color removal (U(:R)) according to the detected value of the minimum value detection circuit 3032.
Look-up table (LOT) to obtain the control amount for
, 3034 is a masking circuit that performs masking circuit filling on the output signal of the lookup table 3031;
035 is an IIcR circuit (undercolor removal circuit) that performs undercolor removal processing on the output signal of the masking circuit 3034 based on the output value of the lookup table 3033. 303
Reference numeral 6 denotes a density conversion circuit that converts the recording density to a designated density for the output signal of the OCR circuit 3035, and 3037 represents a scaling processing circuit that converts the output signal of the density conversion circuit 3036 to a designated scaling factor.

3038 is an interface circuit (I/F) for transmitting signals between a printer or an input/output terminal (not shown) and the wood panel;
Reference numeral 3039 is a controller that controls the entire device, and inside the controller 3039 there is a CPU (Central Processing Unit) such as a microcomputer, and a ROM in which processing procedures as shown in FIG. 10 are stored in program form.
(read-only memory), RAM (random access memory), etc. used for data storage and work area.

3040 is a peak detection circuit that detects the peak value of the output value manually input from the scaling processing circuit 3037 through the interface circuit 3038 and the controller 3039; 3041 is an operation unit that issues instructions to the controller 3039; 3042
is a display unit that displays the control status of the controller 3039 and the like.

3043 is a lens aperture control unit that controls the aperture of the imaging lens 3010, 3044 is a lens distance ring control unit that adjusts the focus of the imaging lens 3010, and 3045 is a mirror drive unit that drives the movable mirror 3008. 3046 is a trimming frame control unit that controls the trimming frame display 3015, and 3047 is a touch panel control unit that controls the touch panel 3016. 3048 is a rotary table rotation control unit that drives and controls the rotary table 3005; 3049 is a sub-scan control unit that controls the scanning of the sub-scan drive table 3004; 3050 is a lamp light control circuit that controls the light amount of the light source (lamp) 3001; 3051 is a lamp position driving source that adjusts the position of the light source 3001 via the lamp holding member 3017.

3052 is a timing generator that generates a timing signal (clock) under the control of the controller 3039; 3053 is a bus that connects each of the above-mentioned control units and processing circuits to the controller 3039; 3054 is a data line for output equipment; 3055 is a synchronization signal line for the output device, and 3056 is a communication line.

Next, the operation of each part will be explained.

The light source 3001 is a light source such as a halogen lamp, and the light emitted from the light source 3001 is passed through a heat absorption filter 30.
02 and an illumination optical system 3003, a transparent original 3007 such as a 35 mm photographic film placed on a film holder 3006 is illuminated. By switching the optical path by the movable mirror 300B, the image of the transparent original 3007 is projected onto the screen 3014 through the projection lens 3011 and mirrors 3012 and 3013, or through the mirror 3009, the imaging lens 3010, and the three-color separation prism 3021. Through CCD line sensor 30
22 to 3024.

In the case of the above-mentioned mode (■), the CCD line sensors 3022 to 3024 are connected to the timing generator 3052.
The output signals of each CCD line sensor are input to an analog circuit 3025. The CCD alignment mechanisms 3018 to 3020 each
This is for registering the CD line sensors 3022 to 3024 with the three-color separation prism 3021, and needs to be adjusted at least once. The analog circuit 3025 is composed of an amplifier and an A/D converter, and converts the signal amplified by the amplifier into the signal output from the timing generator 3052 using the A/D converter in synchronization with the timing clock for D/D conversion. A/D conversion.

Next, RlG, B output from the analog circuit 3025
A dark processing circuit 3027 applies dark signal level correction to each digital signal, a shading correction circuit 3028 performs shading correction in the main scanning direction, and a pixel deviation correction circuit 3029 corrects pixel deviation in the main scanning direction. , for example, by shifting the write timing of a FIFO (first-in, first-out) buffer.

Next, the color conversion circuit 3030 performs color correction of the color separation optical system 3021, and converts the RlG and B signals into Y, M, and C color signals depending on the output device.

1.0 color signal. In the next lookup table 3031, the luminance linear signal is converted to LOG or arbitrary γ conversion is performed by referring to the table.

Reference numerals 3032 to 3037 constitute image processing circuits for outputting images in four colors, Y, M, C, and BK (black), which are mainly used in printers such as color laser copying machines. Here, a minimum value detection circuit 3032, a masking circuit 3034, a lookup table 3033, and an OC
The combination of R circuit 3035 performs printer masking and LICRC (undercolor removal).

Next, the density conversion circuit 3036 performs table conversion of each density signal, and the scaling processing circuit 3037 roughly performs scaling processing in the main scanning direction, and after the scaling processing, Y'
, M', C', UK' signals to the interface circuit 30
38 to the printer of the output device. The interface circuit 3038 connects the data line 3054 to the output device.
and a synchronization signal line 3055, for example, a control command communication line such as R5232C, and a communication line 305.
It is also possible to communicate with a computer (for example, a personal computer) via 6.

On the other hand, the lamp position driving source 3051 is the lamp 305 as a light source.
This is for adjusting the lamp position when converting 1, and the lamp 3001 is positioned manually or automatically in accordance with the manual key operation on the operation unit 3041. The lamp light amount control section 3050 and the lens aperture control section 3043 are C
The amount of light received by the image projected onto the CD line sensors 3022 to 3024 is adjusted. Further, the mirror drive unit 3045 controls the movable mirror 3008 to guide the image of the transparent original 3007 to the screen 3014 or the CCD line sensor 3008.
22 to 3024 is performed.

In the case of mode (2) in which an image of the transparent original 3007 is projected onto the screen 3014, a trimming frame display controller 3046 displays a trimming area in order to instruct trimming of the screen displayed on the screen 3014. 3015 , and a touch panel control unit 3047 controls a touch panel 3016 that manually controls the trimming area.

Further, the lens distance 111 is controlled by the ring control unit 3044 to control the ring of the imaging lens 301O, so that images projected on the CCD line sensors 3022 to 3024 and the screen 3014 are focused. The adjustment signal generation source 3026 generates a signal manually input as a standard signal when adjusting the analog circuit 3025.

Next, the overall control operation of this apparatus will be explained with reference to the flowchart in FIG.

Note that the control procedure in this flowchart is based on the controller 3.
039 is stored in the internal ROM.

Preparatory operation: When a power switch (not shown) is turned on, the controller 3039 initializes each part (step 51) and enters a state of waiting for a command manually input from an external device or from the operation unit 3041 via the interface circuit 3038. In this state, when the film holder 3006 with the transparent original 3007 mounted thereon is set on the rotary table 3005, the light source 3001 illuminates the heat ray absorption filter 3006.
002, an illumination optical system 300 including a condenser lens, etc.
The image of the transparent original illuminated through the movable mirror 30
08 and projection lens 3011 and mirror 3012.301
:l onto the screen 3014.

Transparent originals 3007 have images in vertical and horizontal orientations, but if you want to rotate the image and project it, you can use it from an external device via the interface circuit 3038 or from the operation unit 3041 to the controller 3039. When the rotation of the image is instructed (step S2), the controller 30
39 is a rotary table rotation control unit 3048 via a bus 3053
A rotation control command is sent to the rotary table 3005 to rotate the rotary table 3005 (step S3). At this time, since the film holder 3006 is fixed to the rotating table 3005, it rotates together with the rotating table 3005. In this way, when the transmission thickness 753007 is rotated, the image projected onto the screen 3014 is also rotated.

Next, if you want to trim the image, use the operation section 3041.
or from an external device via the interface circuit 3038 (step S4), the controller 3039 sends a manual command of trimming information to the touch panel control unit 3047, and the touch panel control unit 3034 displays the trimming information on the touch panel. The trimming information manually generated from 3016 is transferred to bus 3.
053 to the controller 3039, and the controller 3039 sends trimming frame control information created based on the imported trimming information to the trimming frame display control unit 3046 via the bus 3053 to display the trimming area (step S5).

Next, from the operation unit 3041 or the interface circuit 3
When the external device instructs the controller 3039 to start image reading via 038, image reading starts.
This is carried out according to the following procedure (step SS).

Optical path switching: First, the controller 3039 outputs a drive control signal to the mirror drive unit 3045 to move the movable mirror 3008, and the image of the transparent original 3007 is transferred to each CCD via the three-color prism 3021 by the mirror 3009 and the imaging lens 301O. Line sensor 3022-3
024 (step S)
7).

Dark correction signal set secondary, dark correction circuit 3027
In order to set the dark correction information to
039, the lamp light amount control circuit 3050 is controlled to turn off the lamp, or the sub-scanning control unit 304
9 to move the sub-scanning drive stand 3004 to a light-shielding position where each CCD line sensor 3022 to 3024 is shielded from light (before step S8). Next, the dark correction circuit 3o27 is controlled by the controller 3039, and the dark correction circuit 3027 is controlled based on the signal that is converted into a digital signal and outputted via the analog circuit 3025.
A dark correction signal is set up (after step S8).

AE (automatic exposure adjustment): Next, controller 3039
controls the lamp light amount control circuit 3050 to
001 is turned on, and the dark correction circuit 3027, shading correction circuit 3028, pixel shift correction circuit 3029, color conversion circuit 3030, lookup table 3031, masking circuit 3034, OCR circuit 3035, density conversion circuit 3036, and scaling processing circuit 3037 are activated. The peak detection circuit 304 is controlled so as to enter the all-through mode (in which the human input data is output as is) (step S9), and the peak detection circuit 304 performs high-speed sub-scanning on the raw data input manually to the controller 3039 via the interface circuit 3038.
Peak detection is performed using 0 (step 510).

Then, the brightness of the light source 3001 is changed by controlling the lamp light amount control circuit 3050 so that the detected peak value approaches a certain level (step 511), or
Alternatively, the amount of O light to the CCO line sensors 3022 to 3024 is adjusted by controlling the lens aperture control unit 3043 and changing the aperture of the imaging lens 301O (step 5
12).

AF (autofocus): Next, dark correction circuit 30
The signal subjected to dark correction by 27 is input to the controller 3039 via the interface circuit 3038 with the subsequent processing circuit set to through mode, and the lens distance-1 ring control section 30 uses the information of the input signal.
44 to focus the imaging lens 301O (step 513).

Shading correction data set: Subsequently, each CCD
Line sensors 3022 to 3024 are illuminated by illumination light 10
Step 514) of moving the sub-scanning drive base 3004 to an exposure position where 0% exposure is achieved; the lamp light amount control circuit 3050 adjusts the lamp light amount to an appropriate brightness; and the dark correction circuit 3
Shading correction data is manually set in the shading correction circuit 3028 using the dark-corrected signal in step 027 (step 515).

After the selection, a pixel shift correction amount is set in the pixel shift correction circuit 3029 (step 51B). In addition, the color conversion circuit 3
030, select the lookup table type for lookup tables 3031 and 3033, select the masking type for masking circuit 3o34, and select IJc for tlcR circuit 3035.
The presence or absence of R is selected, the type of density conversion is selected for the density conversion circuit 3036, and the scaling,
The type of sharpness is selected (step 517). Furthermore, the lamp light intensity is controlled to be appropriate via the lamp light intensity control circuit 3050, and the sub-scanning speed and trimming information are sent to the sub-scanning control unit 3049 to move the transparent original 3007 to the sub-scanning start position and put it on standby. (Step 518
).

Data output A: In step 519), the operation is not based on the reading start command from the operation unit 3041, but instructs the output device (not shown) to start via the interface circuit 3038. In step 520), the operation is based on the synchronization signal from the output device. Sub-scanning is started (step 522), and the image is captured while being synchronized with the output device, and the processed image data is output via the interface circuit 3038 (step 523).

Data output B: In the reading operation based on the reading start command via the interface circuit 3038 (step 519
), reports the completion of preparation to the output device (not shown) via the interface circuit 3038 (step 521), starts sub-scanning based on the synchronization signal from the output device (step 522), captures images while being synchronized with the output device Then, the processed image data is output via the interface circuit 3038 (step 523).

FIG. 4 shows a circuit configuration of another embodiment of the present invention.

In this figure, 3059 is the pixel shift correction circuit 3 of FIG.
029 is a corresponding buffer memory, 3060 is the entire image sensor, 3061 is a CCD line sensor with an R color separation filter, and 3062 is a CCD line sensor with a G color separation filter.
CD line sensor 3063 is a CCD line sensor having a B color separation filter. Further, 3064 is a CCD alignment mechanism for aligning the t-co lines 3061 to 3063, and 3065 to 3067 are drive signals output from the timing generator 3052 to drive the CCD line sensors 3061 to 3063, respectively. The rest of the structure is the same as that of the previous embodiment shown in FIG.

The image sensor 3060 is a 3-line line sensor 3061~
3063, each line sensor 3061 to 30
63 are independently driven by drive signals 3065 to 3067 output from the timing generator 3052. Furthermore, each of the line sensors 3061 to 3063 is capable of capturing R, G, and B color-separated images using respective on-chip color filters.

The buffer memory 3059 stores each line sensor 3061 to 3.
063 is a delay memory for correcting positional deviation in the sub-scanning direction, and is configured using, for example, several FIFO memories. The amount of delay for each color is controller 3
039, preliminary settings are made according to the sub-scanning speed.

FIG. 5 shows the configuration of a control system for performing automatic focus adjustment in the embodiment of FIG. 4. In this figure, 3069 is a distance ring attached to the outer periphery of the imaging lens 301O, 3070 is a motor that rotates the distance via a speed mechanism 3070. 3073 is an image processing unit, which includes from a shading correction circuit 3028 to a conversion processing circuit 3037.

Further, Xp is the position of the point P° on the film 3007 in the optical axis direction, and XQ is the imaging position (in the optical axis direction) of the image (Qo) of the point P°.

Furthermore, Q'' is determined when the focal position of the imaging lens 3010 is changed by controlling the motor 3071 via the distance ring control unit 3044 by the controller 3039 and moving the distance ring 3069 via the deceleration mechanism 3070. Point P'
This shows the imaging position of . Note that the image sensor 306
The configuration of the automatic focus adjustment of the embodiment shown in FIG. 2 is the same as that shown in FIG. 5 except for the part 0.

FIG. 6 shows a specific example of the image reference area for automatic focus adjustment in the embodiment of the present invention. In this figure, 310
0 is an image area of the transparent original 3007, and 3101 is an image reference area for 8F (automatic focus adjustment) that is referred to when performing automatic focus adjustment. 3100° is an image area when the orientation of the transparent original 3007 is rotated by 90°.

As shown in this figure, in this embodiment, the area near the center of the screen is used as the image reference area for F, just as the AF of a normal camera is based on image information near the center of the screen, and In consideration of high-speed processing, the degree of focus is detected based on signals in the main scanning direction.

FIG. 7 shows an image area 310 of the above-mentioned subject document 3007.
0 is the trimming area 3 surrounded by points P1 and P2 in this figure.
120 shows the position of the AF image reference area 3121 when scanning is performed after trimming at 120. Since the effective image to be trimmed and captured using the touch panel 3016 is within the trimming area 3120 displayed on the trimming frame display 3015, it is best to perform AF within this trimming area 3120, as shown in this figure. desirable. In this embodiment, for example, by setting the AF image reference area of 3121 near the center point of Pl and P2,
For example, even if the transmission thickness fA:+oo7 of photographic film is tilted or warped with respect to the optical axis, it is possible to focus on the required image area.

Note that the 3-line sensor 3 as shown in FIGS. 4 and 5
When finding the R and G focal positions using 061 to 3063, sub-scanning is performed after detecting one focal position so that the R and G revision image reference areas match on the film surface of the transparent original. It is better to move 6 in the direction.

An autofocus (automatic focus adjustment, AF) method in an embodiment of the present invention will be explained with reference to FIGS. 8 and 9.

Generally, in autofocus, the degree of focus (degree of focus) is evaluated (detected) by some means, and based on this degree of focus, the position of the lens distance + mi is controlled to achieve focus. Images that are in focus have sharper edges than images that are out of focus. This corresponds to the fact that the amount of high frequency components in the image signal when reading the image is large. In general, cameras use a method to perform AF by detecting from the image signal how much the image is in focus (or conversely, whether it is out of focus), such as by using the amount of high-frequency components of the image signal as the evaluation quantity. In the field, this method is called the blur amount detection method. Other methods that utilize the principle of triangulation include an active method that projects a spot light or a bang light, and a shift detection method that detects the amount of shift of a slam in images captured by multiple sensors.

The embodiment of the present invention uses the above-mentioned blurred person detection method which has a simple mechanical configuration.

That is, for evaluating the degree of focus (sharpness), for example, a G (green) image signal read out from the CCD line sensor 3023 (or 30623) is used, and each image reference area for AF 3101 shown in FIG. 6 is used. The sharpness is determined for the image signal of .It is known that the evaluation of the sharpness P at this time can be obtained by, for example, the following arithmetic expression (1).

P=Σ (XJ
a and b are the numbers of the second pixel from the beginning and the last pixel in the main scanning direction of the revised image reference area 3101. ) FIG. 8 shows the value of sharpness P when the distance ring 3069 of the imaging lens 3010 is moved by the lens distance at ring control unit 3044 and the focal position is changed by changing the lens extension amount ΔX of the lens 3010. This is an example of a change. Here, it is assumed that the sharpness P is calculated using the above equation (1).

By the way, it is considered that the point where the above-mentioned sharpness P is highest is the most in focus, but 3 in Fig. 8
In the curve 103, the maximum value (peak value) S2 is low, and the image imprinted in the revised image reference area does not contain many high-frequency components such as edges, so it is based on the sharpness of the AF image reference area. If the focus adjustment is performed while the camera is still in use, the focus adjustment cannot be performed accurately.

However, even if you focus accurately on the parts of the film that are not sharp (image parts with low sharpness), even if the focus is a little loose, it will have little effect on the quality of the output image, but the sharp parts (sharp image parts) has a very significant effect on the quality of the output image depending on the focusing condition, so 310 in Figure 8
It can be seen that it is better to perform focusing based on information on the focal position of the AF image reference area such that the maximum value S1 is as high as possible, as in the case of the sharpness curve of No. 4.

FIGS. 9(A) and 9(CB) show an example of detecting the focal position at multiple positions in the image area. In this figure, 31
00, 3100' is the effective image area on the transparent original 3007, and 3101.3131~:1136,31
41 to 3148 are image reference areas for AF, respectively.

The transmission original 3007, such as a 35 mm photographic film, is tilted with respect to the optical axis of the imaging optical system, or the original itself is curled, so that the imaging position of each part is shifted from the plane.

In order to deal with this, in the embodiment of the present invention, as shown in FIG. 9 (△)
, (B) By measuring the sharpness with respect to the amount of lens extension at a plurality of positions and adjusting the focus based on the sharpness information, the entire object is brought into focus. At this time, the controller 3039 in FIG. 2 or 4 determines that there are not many sharp parts in the original document image for areas where the peak value (maximum value) of sharpness does not reach a certain level SA. control is performed so that the focus adjustment position is determined from information on the degree of focus for other AF image reference areas.

The flowchart in FIG. 10 shows an example of the above-described $1] control procedure by the controller 3039 in the embodiment of the present invention.

First, lens distance Il! ! Ring 3069 with lens distance 1lII
After moving to the initial position via the ring control unit 3044 (step 531) and setting the revision image reference area to the first one 3101 (step 532), the sharpness P is measured and the measurement result is used as the It is stored in the internal memory together with the data of the lens extender (step 533).

Next, it is determined whether or not the sharpness has been measured for all AF image reference areas (Step 534), and if the determination is negative, the AF image reference area is moved to the next M one (Step 535). , the process returns to step S33 and the above-described operations are repeated.

If step S34 is affirmative, lens distance 1
It is determined whether the 1JiyA 3069 has reached the terminal end (step 536), and if the determination is negative, the lens distance ring 3069 is moved by a unit pitch via the lens distance i ring control unit 3044 (step 537), and the process returns to step S32. The steps from steps 532 to S36 are repeated.

If the determination in step 53B is affirmative, the data with the maximum value exceeding a certain level (reference level) ST is extracted from the data of sharpness P measured in step S33 stored in the internal memory (step 538). . Next, the lens distance flit is determined based on the information on the focus degree of the maximum value.
Adjust the focus by turning the ring 3069 eight times (step 539).
).

Note that the maximum value of the sharpness of each of the plurality of AF image reference areas may be sequentially measured, but in this case, the lens distance ring needs to be moved back and forth a plurality of times, so this is not very preferable.

[Effects of the Invention] As explained above, according to the present invention, while changing the focus position using the focus adjustment means with respect to a plurality of image reference areas for AF within the effective image area of a transparent original such as a film, Since the sharpness is detected and the focus is adjusted based on the sharpness information of the point where the maximum value of the sharpness exceeds a certain level, it is possible to adjust the focus based on the sharpness information of the point where the maximum value of the sharpness exceeds a certain level. Even when it is impossible to focus on the entire imaging area, it is possible to focus on the sharpest part of the image imprinted on the transparent original, which effectively improves the overall image quality of the output image. The effect of increasing sharpness and improving image quality can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the basic configuration of an embodiment of the present invention, FIG. 2 is a block diagram showing the circuit configuration of an embodiment of the present invention, and FIG. 3 shows the operating procedure of the embodiment of the present invention shown in FIG. FIG. 4 is a block diagram showing the circuit configuration of another embodiment of the present invention; FIG. 5 is a schematic diagram showing the configuration of a control system for automatic focus adjustment in the embodiment of FIG. 4; FIG. is an explanatory diagram showing an example of the reference image reference area for revision in the embodiment of the present invention; FIG. 7 is an explanatory diagram showing the position of the reference image reference area for revision when trimming and scanning in the embodiment of the present invention; FIG. is a characteristic diagram showing the change in sharpness characteristics when changing the AF image reference area in the embodiment of the present invention, and FIGS. 9(A) and CB) show a plurality of AF image reference areas in the embodiment of the present invention. Explanatory diagram: FIG. 1O is a flowchart showing the control procedure of the focus adjustment operation of the embodiment of the present invention shown in FIG. 3001... Light source, 3004... Sub-scanning drive stand, 3005... Turntable, 3007... Transparent original, 3008... Movable mirror 301O... Imaging lens, 3014... Screen, 3015. ...Trimming frame display device, 3016...Touch panel, 3018.3019.3020...CCD positioning mechanism, 3021...Three color separation prism, 3022.3023.3024...CCD line sensor, 3038... - Interface circuit, 3039... Controller, 3040... Peak detection circuit, 3043... Lens aperture control section, 3044... Lens distance ring control section, 3061.3062.3063... CCD line sensor, 3064 ...CCD alignment mechanism, 3069...Distance ring, 3071...Motor, 3073...Image processing unit, 3100.3100°...Image area, 3101, 31
31-3136. 3141 to 3148... - AF image reference area. Figure Figure Figure Figure Figure

Claims (1)

[Scope of Claims] 1) an imaging lens that forms an image of a transparent original illuminated by an illumination means; an imaging element that photoelectrically converts the image formed by the imaging lens; and an imaging element that photoelectrically converts the image formed by the imaging lens; sharpness detection means for detecting the sharpness of an image in the AF image reference area based on an image signal of one area out of a plurality of predetermined AF image reference areas obtained by the imaging lens; a focus adjustment means that adjusts the focus by movement; and a focus adjustment means that sequentially determines the maximum value of the sharpness obtained from the sharpness detection means for the plurality of AF image reference areas while changing the focus position by the focus adjustment means. Controlling the focus adjustment means based on a maximum value extraction means to extract and information on the sharpness at a location where the maximum value of the sharpness extracted by the maximum value extraction means exceeds a predetermined certain level. An image reading device comprising: automatic focus adjustment control means for performing focus adjustment.