JPS62105571A - Film reader - Google Patents

Abstract

PURPOSE:To read excellently a recording picture such as a microfilm by adjusting a focus by a film transmission light after the exposure is adjusted at application of power supply and deciding the threshold value of quantized picture information. CONSTITUTION:In turning on a power switch 140, a CPU 301 initializes each circuit, drives carrier equipments 123, 129 to rewind a film F, a lamp 32 is lighted at the end of rewinding, the luminous quantity is detected by an image sensor 36 and its exposure signal drives a light quantity control circuit 302. When the light quantity of the lamp 32 reaches a prescribed value, the film retrieval is applied, an automatic focus circuit 303 is operated to focus the picture frame set to the read position based on a picture read signal. While a sensor 36 is moved by a CCD sub scanner 12, the picture frame is read and a processing circuit 304 judges the picture density based on the picture signal to decide the threshold value in response to the density.

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a film reading device that reads an image recorded on a film by photoelectrically converting the amount of transmitted light or reflected light of the film exposed by a light source. It is.

[Prior art]

2. Description of the Related Art Conventionally, documents have been recorded on microfilm for purposes such as reducing storage space for large amounts of documents and facilitating data retrieval.

In addition, with recent advances in electrical image processing technology, images recorded on microfilm are read by an image sensor with a photoelectric conversion function such as a COD image sensor, and the image is displayed based on the read signal. It has been proposed to perform recording, storage, transmission, etc. of image signals.

Generally, reading images recorded on microfilm is done by
A desired frame of microfilm is exposed to light from a light source, and the transmitted light is passed through a lens.

This is done by focusing an image on an image sensor via an optical system such as a mirror, and photoelectrically converting the optical image. Therefore,
The density of the read image is blurred from side to side depending on the light intensity of the light source used to expose the microfilm.Is it possible to get a good read? -i, it is necessary to set the light intensity of the light source to an optimal value.

Furthermore, if the optical image is not formed on the light receiving surface of the image sensor, a blank image will be output, so it is necessary to perform this focusing accurately.

Furthermore, conditions for recording images on film,
The contrast of recorded images differs depending on the material of the film, etc., and if the image signals output from the image sensor are always subjected to the same processing, it is not possible to obtain a good read output.

Therefore, a technique has been proposed in which the light intensity of a light source for film exposure is detected and the light intensity is adjusted to a predetermined value. Further, an AE technique that automatically performs focusing according to a transmitted light image of a film, and an autofocus technique that varies the processing of an output image signal from an image sensor by measuring the image density of the film have also been proposed.

However, these three technologies are related to each other,
If the exposure amount is not good, the autofocus operation will not be accurate, and if the focus is not accurately set, the image density cannot be accurately grasped, causing problems such as poor AE operation.

〔the purpose〕

The present invention has been made in view of the above points, and an object of the present invention is to provide a film reading device that can satisfactorily read images recorded on a film such as a microfilm. In a film reading device that reads the image recorded on the film by photoelectrically converting the amount of light transmitted through the film, the exposure amount is adjusted when the device light source is turned on, and then the film is transported to the reading position. The purpose of the present invention is to provide a film reading device that adjusts the focal point using the transmitted light of the film conveyed to the film, and then determines a threshold value for quantizing the photoelectrically converted image information based on the image density of the film.

〔Example〕

FIG. 1 is a schematic diagram of a brochure film reading device to which the present invention is applied.

In the figure, 48 and 49 are film cassettes that store the film F, and the film F frames 31a and 31
b is emitted from the halogen lamp 32 and is emitted from the condensing lens 3.
It is illuminated by light focused by 3. Each image of the frames 31a and 31b of the film F illuminated in this way is
A COD in which a plurality of light receiving elements are arranged in the main scanning direction through an optical system consisting of an imaging lens 34 and a fixed mirror 35.
An image is formed on the scanning plane of a one-dimensional line sensor 36 composed of a charge coupled device (charge coupled device) or the like. This one-dimensional line sensor 36 is fixed to a carriage 39 that can reciprocate while being guided by a pair of parallel guides 37 and 38. Furthermore, since the carriage 39 is fixed to a wire 40 that makes the rotation from the motor 41 a linear motion,
By driving the motor 41, the one-dimensional line sensor 36 moves in a sub-scanning direction perpendicular to its main-scanning direction, thereby reading image information line by line. The image signal obtained by reading the image in this manner is converted into a z-value and output.

A photointerrupter 43 that detects the start of reading scanning is arranged on the main body side of the apparatus, and when a light shielding plate 44 fixed to the carriage 39 blocks the light of the photointerrupter 43 as the carriage 39 moves, the photointerrupter 43 detects the start of reading scanning. 43 generates a read scan start timing signal.

On the other hand, a switching mirror 45 is arranged between the imaging lens 34 and the fixed mirror 35, and a switching mirror 45 is arranged between the imaging lens 34 and the fixed mirror 35.
and 4b, the switching mirror 45 and the projection lens 4
The image is also enlarged and formed on a screen 47 as a display means via a display device 6 or the like. On this screen 47, a reading frame 1 for a half-size image and a reading frame 2 for a full-size image are printed.

If the recording paper set in a laser beam printer (not shown) that forms an image on the recording paper using the read image signal is vertically long, the laser beam printer reads the half-size area surrounded by the reading frame 1 and prints the image. On the other hand, if the recording paper is horizontally long, the laser beam printer reads the full size area surrounded by the reading frame 2 and prints it out.

FIG. 2 is a block diagram showing an example of the configuration of a control and signal processing circuit of the microfilm reading device shown in FIG.

F is a microfilter t1 on which an image is imprinted, and is exposed to light from a lamp 32 as a light source.

The transmitted light of the microfilm F is projected onto the line sensor 36 by the lens 34. The focal position of the lens 34 can be changed by a step motor built into the focusing lens drive device FD.

The CPU 301 is composed of a microcomputer and is responsible for overall control of the device, and includes an image processing circuit 304 that binarizes the output of the line sensor 36, and a l/'/z 34↓
1>ㅅ COD sub-scanning device 1 that performs sub-scanning operation
0 and film F from the cassettes 48 and 49. Further, the CPU 301 is initialized by a reset (pulse) signal R3 that controls the reset signal generation circuits 11 to 9 in response to the operation of the power switch 140 when the power is turned on.

The image processing circuit 304 uses an internal comparator to binarize the analog image signal converted into an electric signal by the line sensor 3rd.
When reading the image of F'5, the darkness value which is the standard for binarizing the image signal is determined based on the output of the image sensor 36, and the 6 operations (pre-reading and reading operations) are performed. Do this Q,, A E operation +
sf and reading position (transfer fr-f, I'near)
i.mu.(c)) Automatically determines the darkness value for binarization according to the density of the image.

The autofocus (AF) circuit 303 focuses the microfilm image on the image sensor 36 based on the output of the image sensor 36, determines the position of the lens 34 where the image can be incident, and moves the focusing lens 34. The lens 34 is positioned at the just focus point (focus point).

The power supply to the lamp (halogen lamp) 32 is controlled in order to change the light amount of the lamp (halogen lamp) 32 based on the output of the lamp light amount controller 36.

The COD sub-scanning device 12 has a line-shaped image sensor 36.
It is composed of mechanical parts such as the above-mentioned motor 41 that moves the image in a direction substantially perpendicular to the main scanning (sub-scanning).

The film transport device 123, 139 uses motors to rewind the film in the cassette 48, 49 and feed the film, thereby searching for a desired image frame. It has a mechanism.

FIG. 3 is a flowchart showing the control procedure of the CPU 301 shown in FIG.
Execute the operation of this flowchart i in accordance with the program written in advance in M. 6 The reset signal RS is input from the reset signal generation circuit 1l to the CPU 301 by the operation of the power switch 140 provided in the device. , Hee.

The CPU 301 initializes various registers, memory, ports, etc. After the initialization operation is completed.

The film transport devices 123 and 139 are driven to rewind the film. This makes it possible to create a state in which there is no film at the reading position. If rewinding is completed, the film is loaded from the beginning to the reading position, and if it is not, turn on the lamp 32 and detect the first rewind with the image sensor 36. The light intensity is set to a predetermined value by the Sl light amount signal.
A light amount control signal is output to the +211 circuit 302.

When the amount of light from the lamp 32 reaches a predetermined value, it is then determined whether a film image frame retrieval command has been input by the operator through an operation unit (not shown). If a film search command has been input, the film transport device 123.1
39 to perform a film search operation to locate the designated frame at the reading position.

When the search for the specified frame of film F is completed,
The autofocus circuit 303 is operated to focus the image frame set at the reading position based on the image reading signal from the image sensor 36. Since the exposure amount of the light source is optimal, the focusing operation is performed well. And, due to autofocus operation,
Once the lens 34 has been moved to the in-focus position, it is determined whether or not there is a reading command from the operator from the aforementioned operation section.

If there is a reading command, the image processing circuit 304 is caused to perform an AE operation for determining a threshold value for binarizing the analog image signal from the image sensor 36. That is, the image frame set at the reading position is sent to the image sensor 3.
6 is moved by the COD sub-scanning device 12 while the image sensor 36 performs an image reading operation.

The image processing circuit 304 determines the image density based on the analog image signal obtained thereby, and determines a threshold value according to the density. Note that since the amount of light and focusing are appropriate, the AE operation is performed well.

Once the threshold is determined in this way.

The image sensor 36 is sub-scanned by the COD sub-scanning device 12 to perform an image reading operation for outputting a binary signal representing a read image to the recording device 305. Once the reading operation is completed, it is determined whether further reading is required, and if so, the reading operation is repeated. On the other hand, if there is no reading request, it is determined whether there is a search request for a different frame, and if there is a request, a film search operation is executed and the searched image is read. Also, if there is no search request, the reading operation is terminated,
Waits for input of a command for a new read request or a new search request.

Then, different microfilms are set in the device,
If reading of that film is requested, after performing a search operation, an autofocus operation and an AE operation are executed, and a new image reading is executed.6In addition, in this case, the light amount control operation of the lamp 32 is not executed. . Therefore, the reading operation can be executed quickly.

In addition, since the light amount setting operation is always performed when the power is turned on, good reading operation is always possible even with changes over time.

FIG. 4 shows a configuration example of the light amount control circuit 302 shown in FIG. 2, and FIG. 5 shows a control procedure related to light amount control. It has been programmed. Further, an example of the characteristics of the output voltage with respect to the input light amount of the image sensor 36 is shown in FIG.

In order to bring out the performance of the image sensor 36 most effectively, it is preferable to set the light amount so that the brightest part in one image has a light amount of EA, which is slightly lower than the saturation exposure amount SE. On the other hand, if it is too bright, the output voltage will saturate,
If it is too dark, the sensitivity/SN ratio will deteriorate.

To achieve this, the light intensity is gradually increased until a voltage vA that is a predetermined amount lower than the saturation output voltage VSAT in the image sensor characteristic specification table is output when the film is not at the reading position of the image sensor 36. All you have to do is stop it near vA.

In FIG. 4, 32 is a lamp which is a light source with a variable amount of light, 34 is a lens, and 36 is an image sensor having a photoelectric conversion function for reading an image.

The automatic light amount setting operation will be explained using FIGS. 4 and 5.

When the light 1 control characteristic code, which is a command to start the light amount setting operation of the lamp, is input from the CPU 301 shown in FIG.
41 starts a light amount setting operation.

That is, in a state where the microfilm is removed from the reading position of the image sensor 36, the first control unit 141
generates a light amount setting start pulse LP (Sl). When the light intensity setting start pulse LP is input, the UP counter 136
and flip-flop 134 is reset.

Then, the clock generator 135 starts and generates a clock of a predetermined period. The UP counter 136 counts the clock of the clock generator 135, and its count value increases. By D/A converting the count value of the UP counter 136 by the digital fist analog light intensity (D/A) converter 137, the power supplied to the lamp 32 from the lamp power supply 138 increases, and as a result, the light intensity gradually decreases. . This amount of light is detected by the image sensor 36, amplified by the amplifier 131, and then converted into an analog-digital (A/D)
The converter 132 performs AD conversion into a digital value of predetermined bits. This AD conversion value gradually decreases, and eventually an overflow occurs. When an overflow occurs, the flip-flop 134 is reset and clock generation from the clock generator 135 is stopped.

Therefore, the count value of the UP counter 136 at this point is held, and the output of the D/A converter 137 is also held, so that the amount of light is fixed.

In addition, the control unit 141 determines that the light amount setting is completed based on the overflow signal, and ends the light amount setting operation 32).
The CPU 301 shown in the second figure is notified of this (S3).

Here, if the amplification factor of the amplifier 131 is set in advance so that the maximum full scale value of the A/D converter 132 is at a level slightly lower than the saturation output voltage of the image sensor 36, the image sensor 36 will automatically The optimal light intensity is set with J to bring out the best performance.

In this way, the lamp light amount control circuit 302 executes the light amount setting operation in synchronization with turning on the power switch and according to the commands from the CPU 301.

In this embodiment, an example was shown in which the light intensity of the lamp was gradually increased, but the light intensity was gradually decreased from a predetermined value, and the A/D
It is also possible to determine whether the overflow signal of the converter 132 disappears and set the light amount at this point to an appropriate value. Further, instead of increasing or decreasing the amount, the appropriate light weight may be determined while performing both.

Further, in consideration of the delay in the response time of the amount of light emitted to a change in the supply voltage of the lamp, data obtained before the output of the image sensor reaches a predetermined value may be used as the set value of the optimum amount of light.

Next, FIG. 7 shows an example of the configuration of the image processing circuit 304 shown in the second diagram.

In this embodiment, the image set at the reading position of the reading device is read twice. Then, an AE operation is performed to determine a threshold value for binarizing the image signal based on the data obtained from the image sensor 36 by the first reading. Then, the image information output from the image sensor 36 in the subsequent second reading is binarized using the threshold determined based on the first reading data.

In FIG. 7, 32 is a lamp, which exposes the object (microfilm) F. 36 is an image sensor made of COD or the like, which reads an image of the subject using light transmitted through the microfilm F. The amount of light emitted from the lamp 32 is controlled by controlling its energization by the above-mentioned lamp first-come-first-served control circuit 302, and this amount of light is used to cause the image sensor 2 to read a subject image in an appropriate state. Further, when the value is 1 or -, the autofocus operation by the autofocus circuit 303 has also been executed.

63 is an analog-to-digital converter which converts the analog image signal of the image sensor 36 into Nb representing the density of each pixel.
Convert to 1t digital signal.

64 is a peak value detection circuit that detects the peak value of the bright level of the image signal. This peak detection circuit 64 divides the image signal obtained by one scan into a plurality of blocks, and detects the peak value of the image signal of each block.

The image signal obtained by one scan is sent to the block setting circuit 6.
5 into blocks of a predetermined number of pixels.

The block setting circuit 65 is a circuit that divides one scanning line into several blocks, and uses horizontal synchronization signals H and 5YNC synchronized with each reading scan of the line sensor 36 as a synchronization signal to start counting. It is a circuit.

Then, by setting the unit block to be N bits, (1) the scanning line is divided into an arbitrary number of blocks each having N bits.

The block setting circuit 65 is cleared by HSYNC,
The clock CLKI from the clock control circuit 11 is counted, and a reset signal R3I is output to the peak value detection circuit 64 every N counts. Therefore, two adjacent HS
The YNC period, that is, the lifetime scanning period is divided into m blocks. The number of divisions m is appropriately set in consideration of the size of characters, symbols, etc. of the recorded image on the microfilm.

As described above, by using the output of the block setting circuit 65 as the reset signal RSI of the peak value detection circuit 64, the peak value detection circuit 64 always detects the peak value of each block.

66 is a line address setting circuit, which is a circuit for setting an address area in the sub-scanning direction.

Further, 67 is a block address setting circuit, which is a circuit for setting the block area being scanned. To binarize the image signal by presetting n-bit data (Do-Dn) and m-bit data (Do-Dm) from the control unit 70 to the line address setting circuit 66 and block address setting circuit 67. An image area (threshold value determination area) as shown in FIG. 8 necessary for determining the threshold value is set. In FIG. 8, 51 indicates the entire reading range of the line sensor, and 52 indicates the threshold value determination area.In order to determine the threshold value, a smaller area is defined instead of the entire reading range, and from this area. Only the obtained peak value is used as an effective peak value for threshold determination. As a result, even when the image size or image position on the film is non-uniform, the peak value obtained from the film portion other than the image is invalidated. It goes without saying that this area should always be set to a size and position where the image will be present.

The line address setting circuit 66 counts the H, 5YNC signal using the V, 5YNC signal indicating the reading period of one screen of the image as a synchronization signal to start counting, and uses this count output as the sub-scanning direction output from the control unit 70. Generates a line gate signal (L, GT) that is one signal from the start point to the end point of the area by comparing the address (1) oxDm') representing the area start point with the address (Dm''+1~Dm) representing the area end point. .

As described above, the area in the sub-scanning direction can be defined by the line gate signal.

Further, the block address setting circuit 67 uses the H1SYNC signal as a synchronization signal to start counting, counts the R3I signal that is the output of the block setting circuit 65, and uses this count output as the first block area in the main scanning direction that is output from the control unit 70. By comparing the address (Do to Dn') with the last address of the block area (Dn' + 1 to Dn), a block area signal (B, GT) that becomes one signal from the start point to the end point of the area is set.

As described above, the area in the main scanning direction can be defined by the block area signal.

In FIG. 7, 58 is a gate circuit, and the block area determined by the block address setting circuit 67,
A two-dimensional area 52 as shown in FIG. 8 is obtained using the line area obtained by the line address setting circuit 66, and only the signal peak value within that area 52 is selected from among the peak values detected by the peak value detection circuit 64. It is a circuit that passes through.

Reference numeral 69 is a latch circuit for setting the timing at which peak value data is taken into the control unit 70 using CLK2. Reference numeral 70 denotes a control section consisting of a microcomputer for controlling the operation of the image processing circuit. The control unit 70 inputs the latch data of the latches 69 and 75 to a clock signal C.
Synchronize and capture the inputs of LK2 and CLK3.

Reference numeral 71 denotes a clock control circuit, which is a circuit for creating various timing clocks that control the operation of the device.

72 is a comparator for obtaining a z-value image signal by comparing the image signal with a threshold value formed in a predetermined procedure.

Reference numeral 73 indicates the output of the base density detection circuit 74 and the control section 7, which will be described later.
This is an adder that adds the threshold information TLI (Do to Dp) starting from 0 and supplies the threshold value to the comparator 72.

The base density detection circuit 74 is a circuit that detects the approximate base density based on the digital image signal from the A/D converter 63, and CLK3 is a sampling clock that provides timing for taking in the approximate base density to the control unit 70. It can be set arbitrarily. Reference numeral 75 denotes a latch for loading the approximate base density signal into the control unit 70 using the sampling clock CLK3.

The operation of the above image processing circuit will be explained. FIG. 9 is a flowchart showing the operating procedure of the control section 70, and the program shown in this flowchart is stored in advance in the built-in memory ROM of the control section 70.

The image frame to be read on the microfilm is set at the predetermined reading position, the reading operation is in the "T" state, and the second
When an AE operation start command is input from the illustrated CPU 301, the control unit 70 lights up the lamp 32 in order to start the first image reading for determining the threshold value for binarizing the image data. i) Instruct the COD sub-scanning surface to start moving the line sensor 36 forward through the CPU 301 (312).

Part 1. Then, the peak value data of the digital image signal (S i g) and the approximate base density data are captured in the threshold value determination area set in advance as described in Box 1 (S 13 ,
S l 5).

In this way, the first image reading is 42”r
If so (S l 7), turn off the lamp 32 (2,
Make the line sensor 36 double-act (S18, S L
9). Then, using each of the captured data, the control unit 70 determines the density level on the X axis as shown in (I) and (II) of FIG. Create a histogram with frequency on the Y axis (S
14.

In FIG. 10, the histograms obtained from two types of films are shown by solid lines and dotted lines, respectively.

FIG. 10(I) is a histogram of the approximate base conductivity component, and is a graph obtained by sampling the vicinity of the lowest level of the image signal by the base density detection circuit 74 as described above.

Further, (II) is a graph obtained by sampling peak value data within the above-mentioned threshold value determination area of the image signal, that is, in the case of a negative film, data of a portion where the most light is transmitted.

In addition, the graph (IT) has a bimodal characteristic, and the peak on the lower side of the density level shows the base density part, and the peak on the higher side shows the beeb value part of the image signal. This is the location where the signal peak value level is greatest in the sample image area in a film with a base density of .

In the graph (I), Xl is a density level showing a value close to the base density in the sample image area (referred to as Vi-like base intensity), and is the sample data obtained by the base density detection circuit 74. This is the most common concentration level. x1
' is the base density of the film with the second base density, which is lighter in base density than the film with the first base density for which Xl was determined, and is the density level with the most sample data. Generally, the base density of a film is not the same depending on the finished state of the film, and the density level differs from film to film.

In the graph (II), the second base density shown by the dotted line is lighter than the first base density shown by the solid line.

In the solid line histogram obtained in this way, the approximate base density representative value x1 and the peak value density representative value x2 of the image signal are detected (5201), and the difference between these two values, that is, the value of x2-Xl , the contrast value XCT
(S21). And this contrast value xCT
The value of 1/2 is outputted to the adder 73 as threshold information TLI (S22). Then, the CPU 301 is notified that the threshold information has been determined (S23), and the operation ends.

As described above, the adder 73 adds the base density value from the base density detection circuit 74 to this threshold value information TL to form a threshold value, and applies the threshold value to the comparator 72. In this way, a threshold value is formed that takes into account the image recorded on the film and the base density of the film, and using this threshold value, the digital image signal output from the AD converter 3 in the second image reading is transferred to the comparator 12. It can be binarized and output as a binary signal.

FIG. 10 shows an example of the configuration of the autofocus circuit shown in the second diagram.

In FIG. 2, F is a microfilm with an image recorded on its front or back surface, and is illuminated by light from a light source 32. Reference numeral 34 denotes a main lens for focus adjustment, which is provided with a mechanism for moving it up and down using a drive mechanism that converts the rotational motion of a pulse motor into linear motion using an eccentric cam or the like.

The image converged by the main lens 34 is formed on an image sensor 36 in which a plurality of light receiving elements are arranged in a line. The direction in which the light receiving elements of the image sensor 36 are arranged, that is, the direction in which the image sensor 36 self-scans, is defined as the main scanning direction.

Next, scanning in a direction substantially perpendicular to the main scanning direction (sub-scanning direction) is performed by moving the image sensor 36 in a direction perpendicular to the main scanning direction using the sub-scanning motor 41 and the wire 40. This is done by This makes it possible to sequentially read one screen of the image on the film line by line.

The analog image signal read by the image sensor is binarized in the image processing circuit 304 described above, and then output to the image forming apparatus 1, such as a laser beam printer or an optical desk device.

The control unit 21 outputs a control signal FS for controlling the movement of the lens 34.

The rising edge of the binary signal output from the image processing circuit 304 (
The number of edges (or falling edges) is called focus information, and the counter 22 is configured to count the number of edges.

Then, by controlling the above-mentioned focusing lens 34 to move in the direction where the number of edges is large,
Autofocus works.

In other words, focusing on the fact that the more edges there are, the more the edges are in focus, the controller 21 judges the value counted by the counter 22, and adjusts the focus so that the counted value becomes maximum (peak point). The lens 34 is controlled to move.

Next, the operation will be explained. Figure 11(a) shows part of the image information recorded on film F (microfilm is usually a negative film, and the black parts in the figure allow light to pass through, while the white parts do not pass light). .

FIG. 11(b) is an enlarged view of FIG. 11(a), showing striped patterns Fl, F2. F3 becomes thinner as it goes from the center. When this image information is read between intersection 1 and text 2 (main scanning direction) using an image sensor, it is shown in Figure 12 (
The output waveform will be as shown in a). The stepwise shape in the waveform is an amount corresponding to each cell (light receiving element) of the image sensor.

When this output waveform is binarized by the image processing circuit 304, the output signal C5 shown in FIG. 12(b) is obtained.
8 is input to the counter 22. The counter 22 receives a reset signal R5 every time the image sensor scans, and is reset. The counter 22 has a built-in latch and always stores the previous value in synchronization with the old reset.

In this way, the output of the counter 22 counts the number of edges within one scanning period each time the image sensor scans in the main scanning direction.

FIG. 13(a) shows the state of just focus, and FIG. 13(b) shows the
Indicates an out-of-focus state.

When main scanning is performed between 1f and 42 in (I) of FIG. 13(a) by the image sensor 36.

The waveform becomes as shown in (n) of FIG. 13(a).

(The actual output signal has a step-like shape, but is omitted for ease of explanation). Here, when this output signal is converted into a threshold value TL-c binary value, an output signal C5 like (III) in FIG. 13(a) is obtained.
(when in focus).

Next, the out-of-focus state shown in FIG. 13(b) will be explained.

CI) in FIG. 13(b) is image formation on the image sensor surface, but in reality, main scanning is performed between 1t and 42. Here, the output signal from the image sensor 36 (
II), the number of crossings of the threshold TL is reduced, and the output signal C
5 also has a rising edge of 6'lle'4 as shown in (m) of FIG. 13(b). It can be seen that the number of edges e'4 is 3, which is clearly smaller than the number of edges when in just focus.

Therefore, by counting the above rising edges e, the state of the focus can be known.

The control unit 21 controls the movement of the focus adjustment lens 34 so that the above-mentioned focus information (count value) reaches the maximum point (peak point), and sets it to the just focus point JP.

FIG. 14 shows a sequence flowchart of the autofocus operation of the control section 21.

In FIG. 14, when an autofocus operation start command is input from the CPU 301 shown in the second diagram, step 53
1, the pulse motor for moving the lens 34 is driven and the lens 34 is set at the starting point SP. Then, step S32
Main scanning of the image sensor 36 is performed via the CPU 301. At this time, the image sensor 36 is not moved in the sub-scanning direction. Each time the image sensor 36 scans one line of main scanning, the count value (number of focus information) of the counter 22 is captured and stored in the built-in memory. At this time, the number of steps of the pulse motor is also stored. And step S3
4, it is determined whether the lens 34 is at the end point EP. If the end point EP has not been reached, the process proceeds to step S33, where the pulse motor for moving the lens 34 is operated one more step,
The lens 34 is moved one step from the starting point to the ending point.

Then, in step S32 again, the image sensor is caused to perform main scanning, and focus information is counted and stored in the memory. When this is repeated until the lens 34 reaches the end point EP, the count value of the counter 22 for each of the plurality of main scans in each step in which the lens 34 moves from the start point to the end point is stored in the memory.

When the lens 34 has reached the end point, the process proceeds to step S35, where the maximum value of the count values stored in the memory for each main scan is searched, and the number of steps of the pulse motor corresponding to the maximum value is recognized. Then, the pulse motor of the driving device 10 is driven to move the lens 34 to the position corresponding to the recognized number of steps (336), thereby setting the lens 34 at the just-focus position.

When the setting of the lens 340 to the in-focus position is completed in this way, the CPU 301 is notified of this (S37);
.

In the above embodiments, all of the light amount control operation, AE operation, and autofocus operation are executed based on the output of the image sensor for image reading.
Each operation may be executed using a dedicated sensor in addition to the output of the image sensor.

Besides reading microfilm.

It goes without saying that the present invention can also be applied to reading 35 mm films and X-ray films, and that each of the light amount control operation, AE operation, and autofocus operation can be achieved by using other configurations.

[Effects] As explained above, according to the present invention, when reading an image recorded on a film, the amount of light for exposing the film is adjusted when the device is powered on, and then focusing is performed. Furthermore, since it is configured to determine the threshold value for quantizing the image signal, it is possible to fully utilize the functions of each operation, and it is possible to read good film images without any manual intervention. It is something.

[Brief explanation of drawings]

1 is a schematic configuration diagram of a microfilm reading device, FIG. 2 is a diagram showing an example of the configuration of a control and processing circuit of the reading device shown in FIG. 1, FIG. 3 is a flow chart diagram showing a control procedure of the CPU 301, FIG. 4 is a diagram showing a configuration example of a light amount control circuit, FIG. 5 is a flowchart showing a control procedure of the control section 141, and FIG. 6 is a diagram showing an example of output characteristics of the image sensor with respect to input light amount. FIG. 7 is a diagram showing a configuration example of an image processing circuit, FIG. 8 is a diagram showing an effective area, FIG. 9 is a flowchart diagram showing a control procedure of the control unit 70, and FIG. 10 is a configuration example of an autofocus circuit. Figures 11(a) and 11(b) are diagrams showing the image state recorded on the film, Figure L2 is a diagram showing the output of the image sensor, and Figure 13 (
a) and (b) are diagrams showing the principle of focusing operation, and FIG. 14 is a flowchart diagram showing the control procedure of the control unit 21, 32 is a light source, 34 is a lens, 36 is an image sensor, 301 is a CPU, 302 is a lamp light amount control circuit, 303 is an autofocus circuit, 304 is an image processing circuit, and 305 is a recording device. Output voltage rV) One sub-nine direction B, G-T

Claims (1)

[Claims] In a film reading device that reads the image recorded on the film by photoelectrically converting the amount of light transmitted through the film exposed by a light source, the film is transported to the reading position after adjusting the exposure amount when the device is powered on. A film reading device that adjusts the focus using transmitted light of the film conveyed to a reading position, and then determines a threshold value for quantizing photoelectrically converted image information based on the image density of the film. .