JPH0253015A - Picture reader - Google Patents

Abstract

PURPOSE:To achieve a speedy, accurate focusing by detecting the sharpness of a picture imprinted into a transparent original (film), searching an area including many high frequency components raising sharpness when focusing is performed and performing focusing in the area. CONSTITUTION:While an area moving means E moving the position of an AF picture reference area, the area detecting means F searches the AF reference picture area where sharpness detected by a sharpness detecting means D exceeds a fixed level. In the AF reference picture area, which is detected by the area detecting means F and where sharpness exceeds the fixed level, a focal point detecting means G detects the position of an image pickup lens A where the sharpness detected by the sharpness detecting means D becomes maximum, by changing the focused position of an image pickup lens A through a focusing means C. A control means H moves the image pickup lens A to the position of the image pickup lens, which is detected by the focal point detecting means G, through the focusing means C. Thus, a focal point is adjusted automatically, speedily and accurately.

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.

[Conventional technology]

Conventionally, this type of device for reading transparent originals such as 35 mm photographic film includes, for example, a drum scanner that scans by wrapping the film around a rotating drum, rotating the drum, and moving a photoelectric conversion unit along the drum. However, in this case, autofocus was not particularly necessary.

[Problem to be solved by the invention]

However, when reading a transparent original such as a 35 mm photographic film with a high resolution using a conventional apparatus, the following problems arose.

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 nanometers, focus adjustment is required in order to read an image without blur.

Also, both mounted and unmounted films tend to bend under normal conditions, so 1. It is difficult 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, it is difficult and time-consuming for humans to perform focus adjustment for each mount, and it is difficult to achieve accurate focusing.

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

Furthermore, the image on the subject is originally sharp, that is, well focused at the time of shooting, and the image itself has parts that contain a lot of high frequency components and parts that do not, so when reading the image, the film is not in focus. Even if the subject 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 accurately.

On the other hand, when the maximum value of the sharpness detected while changing the focus position using the focus adjustment means for a certain AF image reference area exceeds a certain level, based on the sharpness information of that AF image reference area, If a control method is adopted in which the focus is adjusted by moving the position of the AF image reference area when the maximum sharpness value of the AF image reference area does not reach a certain level. , its AF
If the movement of the image reference area is inappropriate, there is a possibility that the movement will be repeated many times, and there is a high possibility that it will take a lot of time.

SUMMARY OF THE INVENTION In view of the above-mentioned problems, an object of the present invention is to provide an image reading apparatus that can automatically perform focus adjustment for reading an image of a transparent original at high speed and with high precision.

[Means to solve the problem]

In order to achieve such an object, the present invention provides an imaging lens that forms an image of a transparent original illuminated by an illumination means, an imaging element that converts the original image formed by the imaging lens into an electrical image signal, a focus adjustment means for adjusting the focus of the imaging lens; a sharpness detection means for detecting the sharpness of an image in the AF image reference area based on an image signal of the AF image reference area obtained from the image sensor; and an AF image reference area. area moving means for moving the position of the image reference area for AF, and area detection for searching for an image reference area for AF whose sharpness obtained from the sharpness detection means exceeds a certain level while moving the position of the image reference area for AF by the area moving means. and imaging in which the sharpness obtained from the sharpness detection means is maximized while changing the focal position of the imaging lens via the focus adjustment means in the AF image reference area exceeding a certain level detected by the area detection means. The present invention is characterized by comprising a focus detection means for detecting the lens position, and a control means for moving the imaging lens to the imaging lens position detected by the focus detection means via a focus adjustment means.

[For production]

With the above configuration, the present invention detects the sharpness of an image in an image reference area for AF based on an image signal of a certain image area (image reference area for AF) obtained by photoelectric conversion with an image sensor, and In parallel with the movement of the AF image reference area, the focus adjustment means detects the sharpness while changing the focal position, searches for an AF image reference area whose sharpness exceeds a certain level, and then detects the AF image reference area whose sharpness is constant. The sharpness is detected while changing the focus position using the focus adjustment means for the AF image reference area that exceeds the level, and the in-focus point is detected based on the detected information, so automatic focus adjustment is performed with high precision and high speed. Can be done.

〔Example〕

Embodiments of the present invention will be described in detail below 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 the transparent original J illuminated by the illumination means (2). Reference numeral B denotes an image pickup element that converts the original image formed by the image pickup lens A into an electrical image signal. C is a focus adjusting means for adjusting the focus of the imaging lens B. D
is a sharpness detection means that detects the sharpness of an image in the AF image reference area based on the image signal of the AF image reference area obtained from the image sensor B. E is an area moving means for moving the position of the AF image reference area. F is A by the area detection means
While moving the position of the image reference area for F, the sharpness obtained from the sharpness detection means exceeds a certain level A.
This is an area detection means for finding an image reference area for F.

In addition, G is an image reference area for AF exceeding a certain level detected by the area detection means F, and the focus adjustment means C
This is a focus detection means that detects the position of the imaging lens where the sharpness obtained from the sharpness detection means is maximum while changing the focal position of the imaging lens A via the sharpness detection means. H is a control means for moving the imaging lens A to the imaging lens position detected by the focus detection means G via the focus adjustment means C.

Further, the area detection means F may detect the sharpness while changing the focal position of the imaging lens A using the focus adjustment means C in parallel with the movement of the AF image reference area. or,
The area detection means F is configured to start searching for an image reference area for AF while changing the focal position of the imaging lens A at the initial position by the focus adjustment means C, if the detected maximum value of sharpness does not exceed a certain level. It's okay. Furthermore,
The AF double image reference area search focal position may be determined based on a plurality of pieces of sharpness information detected at the initial position.

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 30.
This is an illumination optical system that converts the illumination light that passes through 02 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; 3006
3007 is a film holder that stores transparent originals, and 3
It is a transparent original such as 5mm photographic film. 3008
3009 is a movable mirror that switches the optical path of the light beam (original image) transmitted through the transparent original 3007; 3009 is a mirror that deflects the optical path of the original image; and 301O is an imaging lens that forms the original image that has passed through the mirror 3009.

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
This is a touch panel for inputting the trimming area integrated with 014.

3017 is a lamp holding member that supports the light source 3001. 3018, 3019.3020 are CCD positioning mechanisms, 3021 are three-color separation prisms that separate the transparent original image formed by the imaging lens 301O into three colors of R, G, and B, and 3022, 3023, and 3024 are prisms, respectively. CCD using a CCD (charge-coupled device) array that photoelectrically converts the original image of each color separated by 3021.
It is a CD line sensor, and this CCD line sensor has a corresponding CCD alignment mechanism 3018.3019.3020.
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 A/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 that generates a standard signal for adjustment to 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 (LOT) 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; 3033 is an under color removal (IJcR) according to the detected value of the minimum value detection circuit 3032;
A lookup table (LtlT
), 3034 is a masking circuit that performs masking processing on the output signal of the lookup table 3031;
035 is a tlcR 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 IIcR 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 (1/F) for transmitting signals between a printer or input/output terminal (not shown) and this device;
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, a ROM (Read Only Memory) in which processing procedures are stored in program form, and a data storage. RAM used as a work area
(random access memory), etc.

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 focus adjustment unit that adjusts the focus of the imaging lens 301O, and 3045 is a mirror drive unit that drives the movable mirror 3008. 3046
3047 is a trimming frame control unit that controls the trimming frame display 5:+o1s, and 3047 is a touch panel control unit that controls the touch panel 3016. 3048 is rotating table 3005
3049 is a sub-scanning control unit 3050 that controls scanning of the sub-scanning drive table 3004;
3051 is a lamp position drive 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 with the controller 3039; 3054 is a data line for output equipment; 3055 is an output Synchronization signal line for equipment,
and 3056 are communication lines.

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 35III11 photographic film placed on a film holder 3006 is illuminated. By switching the optical path by a movable mirror 3008, the image of the transparent original 3007 is transmitted onto the screen 3014 through the projection lens 3011 and mirrors 3012 and 3013, or through the mirror 3009, the imaging lens 301O1, and the three-color separation prism 3021. 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 CCO positioning 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 A/D converter in synchronization with the timing clock for A/D conversion output from the timing generator 3052. Convert to/D.

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 R, G, and B signals into Y, M, and C color signals depending on the output device.

It is converted into I and Q color signals. The next lookup table 3031 converts the luminance linear signal into LOG or performs arbitrary γ conversion by referring to the table.

Reference numerals 3032 to 3037 constitute image processing circuits for outputting images in four colors of Y, M, C, and B (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 the R circuit 3035 performs printer masking and U (:Rf 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.
Interface circuit 3038 that connects 'signals to M', C', and B.
The data is sent to the output device's printer via the . The interface circuit 3038 is connected to a data line 3054 and a synchronization signal line 3055 for the output device, such as a control command communication line such as RS 232 CRT, and also to a communication line 30
It is also possible to communicate with a general computer (for example, a personal computer) via 56.

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 image displayed on the screen 3014. 3015, and a touch panel control unit 3047 controls a touch panel 3016 for inputting a trimming area.

In addition, the lens focus adjustment section 3084 allows the imaging lens 3
The focus of the image projected on the CCD line sensors 3022 to 3024 and the screen 30z4 is adjusted by controlling the position of 01O in the optical axis direction. Adjustment signal generation source 302
6 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 RIIM.

Preparation operation: When a power switch (not shown) is turned on, the controller 3039 initializes each part (step S1) and enters a state of waiting for a command input from an external device or from the operation unit 3041 via the interface circuit 3038. In this state, when the film holder 3005 with the transparent original 3007 mounted thereon is set on the rotating table 3005, the light source 3001 illuminates the heat ray absorption filter 300.
02 and an illumination optical system 3003 including a condenser lens, etc.
The image of the transparent original illuminated through the movable mirror 300
8 and projection lens 3011 and mirror 3012.3013
The image is projected onto the screen 3014 through the image.

Transparent originals 3007 have image orientations of portrait and landscape orientation, but if you want to rotate the image and project it, you can rotate the image from an external device via the interface circuit 3038 or from the operation unit 3041 to the controller 3039. When the rotation 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 removably attached to the rotary table 3005, it rotates together with the rotary table 3005. In this way, when the transparent original 3007 rotates, the screen 3007
The image projected onto 14 is also rotated.

Next, if you want to trim the image, use the operation section 3041.
When trimming is instructed to the controller 3039 from an external device via the interface circuit 3038 (step S4), the controller 3039 sends a manual command for trimming information to the touch panel control unit 3047 via the bus 3053, and the touch panel The trimming information input manually from the touch panel 3016 to the control unit 3034 is sent to the controller 30 via the bus 3053.
The controller 3039 sends trimming frame control information created based on the imported trimming information to the trimming frame display control unit 304 via the bus 3053.
6 and display the trimming area (step S
5).

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.
The following procedure is followed (step 56).

Optical path cutting@: First, the controller 3039 moves the movable mirror 3008 by outputting a drive control signal to the mirror drive unit 3045, and the image of the transparent original 3007 is cut through the three-color prism 3021 by the mirror 3009 and the imaging lens 301O. CCO line sensor 3022-3
024 (Step 5)
7).

Dark correction signal set: Next, 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 3027 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).

^E (Self!! III exposure adjustment): Next, the controller 3039 controls the lamp light amount control circuit 3050 to turn on the lamp 3001, and the dark correction circuit 3027, shading correction circuit 3028, and pixel shift correction circuit 30
29, color conversion circuit 3030, lookup table 30
31, Masking circuit 3034, IJCR circuit 3035
, the density conversion circuit 3036 and the magnification processing circuit 3037 are controlled so that they are all in the through mode (manual data is output as is) (step S9), and input to the controller 3039 via the interface circuit 3038 while performing sub-scanning at high speed. The peak detection circuit 3040 is used to detect peaks on the incoming raw data (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 5l1), or
Alternatively, by controlling the lens aperture control section 3043 and changing the aperture of the imaging lens 3010, the amount of wide light directed to the CCD line sensors 3022 to 3024 is adjusted (step 512).

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 in through mode, and the lens focus adjustment unit 308 uses the information of the input signal.
4 as described in detail later, and the imaging lens 30
10 in focus (step 513).

Shading correction data set: Subsequently, each CCD line sensor 3022-3024 is 100
Step 514) of moving the sub-scanning drive stand 3004 to the exposure position where % exposure is to be performed, the lamp light amount control circuit 3050 adjusts the lamp light amount to an appropriate brightness, and the dark correction circuit 30
While inputting the dark-corrected signal in step 27, shading correction data is set in the shading correction circuit 3028 (step 515).

Selection: Next, a pixel shift correction amount is set in the pixel shift correction circuit 3029 (step 516). 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 3034, and select tlcR for OCR circuit 3035.
, the type of density conversion is selected for the density conversion circuit 3036, and the type of scaling and sharpness is selected for the scaling processing circuit 3037 (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 an operation based on a read start command from the operation unit 3041 (step 519), a start command is issued to an output device (not shown) via the interface circuit 3038 (step 520), based on a 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, 3062 is a CCD line sensor with a G color separation filter, and 3063 is a CCD with a B color separation filter. It is a line sensor. Also, 3064 is C
CCD alignment mechanism that aligns CD line sensors 3061 to 3063, 3065 to 3067 are CCDs
This is a drive signal output from the timing generator 3052 to drive each of the line sensors 3061 to 3063. Further, 3080 is a holding table, and 3081 is a peak detection circuit.

The image sensor 3060 is a 3-line line sensor 3061~
3063, each line sensor 3061 to 3o
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.
This is a delay memory for correcting positional deviation in the sub-scanning direction in 063, and is configured using, for example, several FIFO memory. The amount of delay for each color is controller 3
039 in advance according to the sub-scanning speed.

Further, the function of the sub-scanning control unit 3049 is similar to that in FIG. 2, but the difference is that it moves the sensor side of the image sensor 3060. Furthermore, the peak detection circuit 3081 is a circuit that detects the maximum value of each color signal output from the shading correction circuit 3028, and the peak detection area signal P)IAE generated by the timing generator 3052 under the control of the controller 3039 is The maximum value of input data during the H (enable) period is detected. The peak value detected by the peak detection circuit 3081 is read by the controller 3039.

The rest of the structure is the same as that of the embodiment shown in FIG. 2, so a detailed explanation thereof will be omitted.

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 deceleration mechanism that meshes with the distance ll1lt ring, and 3071 is a motor that rotates the distance ring 3069 via the deceleration 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, the controller 3039 drives the motor 3071 via the distance ring control section 3044 that constitutes the lens focus adjustment section 3084, and moves the distance ring 3069 via the deceleration mechanism 3070, thereby controlling the imaging lens 3069.
It shows the imaging position of point P° when the focal position of 010 is changed. Note that, except for the image sensor 3060, the configuration of automatic focus adjustment in the embodiment shown in FIG. 2 is also the same as that in FIG. 5.

FIG. 6 shows a specific example of the initial position of the image reference area for automatic focus adjustment in the embodiment of the present invention. In this figure:) 100 is the image area of the transparent original 3007, 310
1 is an image reference area for 8F (automatic focus adjustment) that is referred to when performing automatic focus adjustment. 3100' is transparent original 3
This is the image area after rotating the orientation of 007 by 90 degrees.

As shown in this figure, in this embodiment, the area near the center of the screen is used as the image reference area for AF, just as the 8F 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 75 surrounded by points P1 and P2 in this figure.
312 shows the initial position of both image reference areas 3121 for AF when trimming and scanning. The effective image when cropping and capturing an image using the touch panel 3016 is within the trimming area 3120 displayed on the trimming frame display 3015, so as shown in this figure,
It is most desirable to perform AF within this trimming area 3120. In this embodiment, for example, by setting the AF image reference area of 3121 near the center point of Pl and 22, for example, the transmission thickness of photographic film, etc. is 143007
Even if the camera is tilted or warped with respect to the optical axis, it is possible to focus on the desired image area.

When trimming like this, trimming area 3]
If 20 is regarded as the image area 3100, the same control will be performed, so a description of the case of trimming will be omitted below.

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, detect one focused U and then set the sub-focus so that the R and G AF image reference areas match on the film surface of the transparent original. It is better to move in the scanning direction.

The autofocus (automatic focus adjustment, 8F) method in the embodiment of the present invention will be described with reference to FIG.

Generally, in autofocus, the degree of focus is evaluated (detected) by some means, and based on this evaluation, the position of the lens aperture ring or the position of the lens in the optical axis direction is controlled to adjust the 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. Generally, the amount of high-frequency components of such an image signal is used as the evaluation amount (sharpness), and the 8F is calculated by detecting from the image signal how much the image is in focus (or conversely, whether it is out of focus). This method is called the blur amount detection method in the camera field. 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 blur amount detection method which has a simple mechanical configuration.

In other words, CCD is used to evaluate the degree of focus (sharpness).
The G (green) image signal read from the line sensor 3023 (or 3062) is used, and the sharpness is determined for each image signal of the image reference area 3101 shown in FIG. It is known that the evaluation of the sharpness P at this time can be obtained, for example, by the following arithmetic expression (1).

(However, X is the output level of the j-th pixel in the main scanning direction,
a and b are the numbers of the second pixel from the beginning and the last pixel in the main scanning direction of the AF image reference area 3101. ) Figure 8 shows the value of sharpness P when the distance ring 3069 of the imaging lens 301O is moved by the lens distance M ring control unit 3044, thereby changing X to the lens extension amount of the lens 3010 and changing the focal position. This is an example of a change. Here, the sharpness P is calculated using the above equation (1).

Now, when trying to focus the image based on the amount of blur, unfortunately there is no high frequency component within the revised image reference area 3101 on the subject thickness f113007, and the broken line curve 3103 in Figure 8 The peak value S1 of the sharpness P is so small that the amount of lens extension at the in-focus point cannot be accurately detected.

Therefore, in the embodiment of the present invention, the constant bell S shown in FIG.
. An image reference area for AF in which the peak of sharpness P is not lower is searched, and focusing is performed in an image reference area for AF in which the peak of sharpness P is constant and is equal to or higher than bell ST.

FIG. 9 and FIG. 1O each show a specific example of the movement position of the reference area when searching for the image reference area for AF in the embodiment of the present invention. Here, 3100 is an image area, 3
101-3109.3102'-3107' are reference areas. 3101 is especially the initial position of the reference area,
In this embodiment, the range in the main scanning direction is fixed, and the reference area is moved only in the sub-scanning direction. The reference area in FIG. 9 moves from 3101 to 3102 as indicated by the arrow in this figure.
3103, 3104, 3105, 3106, 3107,
Perform in the order of 3108° and 3109.

On the other hand, in Fig. 10, the reference areas are 3101.3102', :1103', 3 as indicated by the arrows in this figure.
104'3105', 310B', 3107
'Move to 1 and 1 in this order. In this example, the length of the reference area in the main scanning direction does not change, but the movement range is also changed in the main scanning direction.

In particular, in an image reading device using a line sensor as an image sensor as shown in FIG. 2 and FIG.
63), the reference area can be moved quickly in the main scanning direction, but in the sub-scanning direction it is necessary to move something with large inertia, such as a stepping motor or servo motor, with high precision. It is difficult to move areas quickly. Therefore, in this embodiment, sub-scanning is performed continuously during the search for the AF image reference area to reduce loss time due to starting/stopping of the motor.

FIG. 11 shows an example of sub-scanning control when searching for an AF image reference area in the embodiment of the present invention. In this figure, the curves 3301 and 3302 each indicate the change in the sub-scanning position y with respect to the search time 1s after the start of the search for the image reference area for revision. For example, as shown by the curve 1301, the initial position y0 It moves at a certain speed in a predetermined direction, and when it reaches a certain position yl, it returns to the initial position y at high speed. I return it to a position close to , and then move it in the opposite direction at a certain speed. In the case of curve 3302, the object is moved to one end of the search range at high speed, and then moved at a constant speed in the opposite direction. Then, when the search time reaches the limit time (ts 11m1t), the search for the reference area is terminated.

If an area where the sharpness P exceeds the constant value S7 is found during the search, the search is terminated there.

The flowchart in FIG. 12 shows the AF in the embodiment of the present invention.
The operation procedure for searching an image reference area for use is shown below.

First, the reference area and lens extension amount are set to default positions (steps 531, 532), the sharpness P at that time is determined, and if po exceeds the fixed value ST (steps 533, 534), the AF Focusing is performed in the image reference area (step 541), and if not, a built-in timer (not shown) in the controller 3039 is set so that the time from the start of the search can be known (step 535), and then sub-scanning control is performed. Part 3049
The sub-scanning for the image reference area for AF is started (step 536), and the sharpness P is increased again until the above-mentioned sharpness P exceeds the constant value SA (step S37.538).
is repeatedly calculated and compared with the constant value S7 (steps S39→537→538). During this loop, the reference area moves. After that, the sharpness P is a constant value S
When the value exceeds 7, sub-scanning is stopped and the sharpness P is set to a constant value ST.
Step 5 To move to the AF image reference area when exceeding
40), focus on that area (step 5)
41).

When the search time exceeds a certain time (tg 11m1t) (step 539), the area search is stopped (step 542), and error processing such as a warning is performed.

FIG. 13 shows an operation procedure for searching both image reference areas for AF in another embodiment of the present invention. In this example and in FIG. 12, step 5331. S:141,5351,5401.54
11 processing is different. That is, in step 5331, while changing the lens extension amount at the initial position, the sharpness PD at each focus position and the maximum value po□8 of the sharpness P0 are determined.
is being detected.

In step S341, the maximum sharpness value PDmax is compared with a constant value S7.

In step 5401, sharpness is determined while changing the lens extension amount. In step 5411, focusing is performed based on sharpness information. Step 5351
Here is the sharpness P at the default position. Since the lens extension amount ΔX is changed based on this, it is advantageous in that information on the sharpness P can be obtained at a position relatively close to the in-focus position.

Figures 14 and 15 show yet another embodiment of the invention. In FIGS. 12 and 15, steps 5371 and 5
372 processing is different. Curves 3201 and 3202 in FIG. 14(A) indicate the position y in the sub-scanning direction with respect to the search time 1s, and are a specific example of movement control of the reference area. The curve 3203 in FIG. 14(B) shows an example of controlling the lens extension amount ΔX with respect to the search time t, and the lens extension amount ΔX is continuously changed.
As shown in step 5371 of the flowchart in FIG. 15, the lens extension amount ΔX may be changed in synchronization with the sharpness detection (step 5372), or in step S3
At point 6, the lens extension amount ΔX is shown in Fig. 14 (B).
A means for controlling the curve 32o3 (not shown)
For example, a microprogram) is commanded to start,
Asynchronous control may be performed in which the process in step 5371 is omitted.

As in these embodiments, by changing the lens movement scene in parallel with the movement of the AF image reference area,
It becomes possible to search for an image reference area for AF at high speed in a wide focus range.

〔Effect of the invention〕

As explained above, according to the present invention, when the sharpness of an image imprinted on a transparent original (film) is detected and focused, an area containing many high frequency components that increases the sharpness is detected. By searching and focusing in that area, it is possible to achieve high-speed and high-aperture focusing.

[Brief explanation of the drawing]

Fig. 1 is a plot diagram showing the basic configuration of an embodiment of the present invention, Fig. 2 is a block diagram showing a circuit structure of an embodiment of the invention, and Fig. 3 is an operating procedure of the embodiment of the invention shown in Fig. 2. 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; The figure is an explanatory diagram showing an example of the initial position of the AF image reference area in the embodiment of the present invention. Figure 7 is an explanatory diagram showing the initial position of the AF image reference area when trimming and scanning in the embodiment of the present invention. , FIG. 8 is a graph showing the relationship between the lens extension amount and sharpness, and FIGS. 9 and 10 are explanations showing an example of an area moving method when searching for an image reference area for AF in the embodiment of the present invention, respectively. 11 is a graph showing a specific example of the sub-scanning operation for searching the image reference area for AF in the embodiment of the present invention, and FIG. 12 is a graph showing the procedure for searching the image reference area for AF in the embodiment of the present invention. Flowchart of one embodiment, FIG. 13 is AF
Flowchart of the second embodiment of the present invention showing another search operation procedure for the image reference area for
) is a graph showing the operation of sub-scanning and lens extension amount control for searching the image reference area for AF in the embodiment of the present invention, and FIG. 15 is a graph showing another search operation procedure for the image reference area for AF according to the present invention FIG. 3 is a flowchart of a third embodiment of FIG. 3001... Light source, 3002... Heat ray absorption filter, 3003... Illumination optical system, 3004... Sub-scanning drive stand, 3005... Turntable, 3005... Film holder, 3007... Transmission Original, 3008... Movable mirror 3009... Mirror 3010... Imaging lens, 3014... Screen, 3015... Trimming frame display, 3016... Touch panel, 3018.3019.3020... CCD Alignment mechanism, 302I...Three color separation prism, 3022.3023.3024...CCD line sensor, 3025...Analog circuit, 3038...Interface circuit, 3039...Controller, 3040...Peak Detection circuit, 3043... Lens aperture control unit, 3044... Lens distance ring control unit, 3049... Sub-scanning control unit, 3052... Timing generator, 3060...
・Image sensor, 3061.3082.3083... CCD line sensor, 3064... CCD positioning mechanism, 3069... Track ring, 3071... Motor, 3073... Image processing unit, 3084...・Lens focus adjustment section, 3100.3100'...Image area, 3101...
Image reference area for AF. Figure 11

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 converts the original image formed by the imaging lens into an electrical image signal; and the imaging lens. a focus adjustment means for adjusting the focus of the AF image reference area; a sharpness detection means for detecting the sharpness of an image of the AF image reference area based on an image signal of the AF image reference area obtained from the image sensor; an area moving means for moving the position of the AF image reference area; and an AF image reference area for which the sharpness obtained from the sharpness detection means exceeds a certain level while moving the position of the AF image reference area by the area moving means. An area detecting means for searching, and A exceeding a certain level detected by the area detecting means.
a focus detection means for detecting an imaging lens position where the sharpness obtained from the sharpness detection means is maximum while changing the focal position of the imaging lens in the F image reference area via the focus adjustment means; An image reading device comprising: control means for moving the imaging lens to the position of the imaging lens detected by the focus detection means via the focus adjustment means.