JPS62105572A - Film reader - Google Patents

Abstract

PURPOSE:To read excellently a recording picture such as a microfilm by adjusting the exposure before film loading, using transmission light of a film at the read position to adjust the focus and deciding a threshold value of quantization of picture information. CONSTITUTION:After initialization by a CPU 301, when a film F is not loaded at a read position, a lamp 32 is lighted and its light 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 and an automatic focus circuit 303 is operated attended with the end of retrieval of designation frame and the picture frame is focused based on a picture read signal of the sensor 36. Then in response to the read command, while the sensor 36 is moved by a CCD sub scanner 12, the picture frame is read. 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. [Prior Art] Conventionally, type 1.9 documents have been recorded on microfilm for the purpose of reducing storage space for large amounts of documents and facilitating data retrieval.

In addition, with the recent advances in electrical image processing technology, the surface image recorded on the microfilm is read by an image sensor with a photoelectric conversion function such as a COD image sensor, and this reading +f%'-; It has been proposed to display, record, store, and transmit images based on the image quality.

The interpretation of images recorded on microfilm is generally
A desired frame of microfilm is exposed to light from a light source, and the transmitted light is 1.

Image is formed on an image sensor via an optical system such as a mirror,
This is done by photoelectrically converting the optical image. Therefore, the density of the read image is influenced by the amount of light from the light source used to double-light the microfilm, and in order to perform good reading, it is necessary to set the light 1' value of the light source to a full value.

Furthermore, if the light image is not formed on the light receiving surface of the image sensor, a blurred 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. Also proposed are 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.

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 density of one image 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 reader that reads images recorded on film by photoelectrically converting the amount of light transmitted through the film, the exposure amount is adjusted before loading the film into the reading position, and then the film is transported to the reading position and the film is read. The purpose of the present invention is to provide a film reading device that adjusts the focus using transmitted light of the image and then determines a threshold value for quantizing photoelectrically converted image information based on the image density.

〔Example〕

FIG. 1 is a schematic diagram of a microfilm 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 CCD in which a plurality of light receiving elements are arranged in the main scanning direction via 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 4o 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 binarized and output.

A photo interrupter 43 that detects the start of reading scanning is arranged on the main body side of the apparatus. Interrupter 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 images.

An enlarged image is also formed on a screen 47 as a display means via a switching mirror 45, a projection lens 46, etc. On this screen 47, there is a half-size image reading frame 1.
and reading frame 2 of the 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 l. 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 microfilm on which an image has been 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 controls the entire apparatus, and includes an image processing circuit 304 that binarizes the output of the line sensor 36, and an auto-focus circuit 303 that sets the lens 34 to the in-focus position.
, a lamp light amount control circuit 302 for setting the light amount of the lamp 32 to a predetermined value. CCD sub-scanning device (δ10, length film F is cassetted) is transported from 48, 49 to t', It is in charge of controlling and supervising. Further, the CPU 301 generates a reset signal from the reset signal generating circuit 1 in response to the operation of the power switch +140 when the power is turned on.
The reset (valve) signal R3+ generated from 1 is set to 1 for the first time.

The image processing circuit 304 binarizes the analog image signal converted into an electric signal by the sensor 36 using an internal comparator, and
- When reading the image, the threshold value is the standard for binarizing the analog image signal in the comparator. The operation determined based on the output of the image sensor 36
'e-taking operation). This is called an AE cutoff operation, and a threshold value for binarization is automatically determined according to the density of the image on the film sheet transported to the reading position.

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 lamp light amount control circuit 302 changes the light amount of the lamp (halogen lamp) 32 based on the output of the image sensor 36, and controls the energization of the lamp 32.

The CCD sub-scanning device 2 has a line-shaped image sensor 3.
6 in a direction substantially perpendicular to the main scanning (sub-scanning).

The film transport devices 123 and 139 use motors to rewind the film in the cassettes 48 and 49 and load (feed) the film, and have a mechanism for searching for a desired image frame. ing.

FIG. 3 is a flowchart showing the control order of the CPU 301 shown in FIG.
The operation shown in this flowchart 1 is executed.

When the reset signal RS is manually supplied from the reset signal generation circuit 11 to the CPU 301 by the operation of the power switch 140 provided in the device, the CPU 301 inputs various registers,
Initializes memory, bore 1, etc. At the beginning of the initialization operation, I=lz, there is no film at the reading position, that is, whether or not the film is rewound to the cassette is set to 1j.
cut off If the rewind film is not rewound, the film transport devices 123 and 139 are driven to rewind the film rewind.From this, it is possible to assume that there is no film at the reading position.

If rewinding is completed or if the film is not loaded in the reading position from the beginning, then the lamp 32 is turned on,
The amount of light is detected by the image sensor 36, and the exposure nl is
(By tR, a light amount control signal is output to the lamp light amount control circuit 302 in order to set the light amount to a predetermined value.

When the light intensity of the lamp 32 reaches a predetermined value, it is then determined whether an image frame search command for four frames has been input by the operator from an operation unit (not shown). If a film search command has been input, the film transport device 123,1
39 to position the designated frame at the reading position and perform a film search operation.

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 causes the image processing circuit 304 to execute an AE cutoff operation for determining a threshold value for binarizing the analog image signal of 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 CCD sub-scanning device W12 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. Incidentally, since the light beam and focusing are appropriate, the AE switching operation can be performed satisfactorily.

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 two symbols indicating the 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, the film search operation is executed and the search image is read. , determines whether the request is for the film currently set at the reading position or a search request for a different film, and if it is for a film that has already been set, performs the above search operation. Execute directly without setting the light intensity. Moreover, if it is for a different film, before the different film is rolled, that is, after performing the light amount adjustment operation again with no film at the reading position, the film loading and retrieval operations are performed.

Further, if there is no new read request or new search request, the read operation is ended and the input of a command for a new read request or a new search request is waited for.

In this way, since the light intensity of one light source is controlled before setting a new film to the reading position Ft, it is possible to always perform the reading operation with the optimum light intensity, and it is possible to read the same film with little change in light intensity over time. Since the setting of the light amount is omitted, the reading operation can be performed quickly.

FIG. 4 shows a configuration example of the light amount control circuit 302 shown in S2. Further, FIG. 5 shows a control procedure related to light amount control. This is preprogrammed in the memory of a microcomputer that constitutes the control section 141, which will be described later. 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 of the 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 amount of light is gradually reduced until a voltage vA that is 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 raise it up and stop it near VA.

In FIG. 4, 32 is a lamp which is a light source with variable light intensity rjT, 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 a light amount control reset signal, which is a command to start the light amount setting operation of the lamp, is input from the CPU 301 of the second M, the control unit 1
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 control unit 141
generates a light amount setting start pulse LP (Sl). Light intensity setting starts When Puffless LP is input, UP counter 13
6 and flip-flop 134 are reset.

Then, the clock generator 135 starts, and the 6UP counter 136, which generates a clock of a predetermined period, starts clocking 1.
The clock of the clock generator 135 is counted, and the count value increases by -. The count value of the UP counter 136 is converted to D/A by a digital-to-analog light intensity (D/A) converter 137.
Lamp 3 from lamp power supply 138 by converting
2, the power supplied increases, and the amount of light gradually increases. 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) A/D conversion is performed by the u converter 132 into digital 4B of predetermined bits. This AD conversion value gradually decreases, and eventually an overflow occurs. When the O/H flow occurs, the 7-lip flow knob 134 is reset and the 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.

Also, based on the second overflow signal, the control unit 141 determines that the light amount setting is completed, and terminates the light amount setting operation (S2).
The CPU 301 shown in the second figure is notified of this (S3).

Here, if the increase rate 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 saturated output voltage of the image sensor 36, the image sensor 36 will automatically The optimum light intensity will be set to bring out the performance of the 36.

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.

Although this embodiment shows an example in which the light intensity of the lamp is gradually increased, the light intensity is 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 by 1, the appropriate light may be determined while performing both.

Further, in consideration of the delay in the response time of the light emitting sand 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 for the optimum light amount.

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

In this embodiment, the image set at reading position n of the reading device is read twice. Then, by the first reading, an AE cutting operation is executed to determine a threshold value for converting the image signal into 21'll'i based on the data obtained from the image sensor 36. 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 (1=1 IJ). U〉・Bu3
21. The amount of light emitted is controlled by controlling the amount of electricity supplied by the lamp light amount control circuit 302 described above,
This light Jt is used to cause the image sensor 2 to read the subject image in an optimal state. Furthermore, at this time, the autofocus operation by the autofocus circuit 303 has also been executed.

63 is an analog-digital converter.

The analog image signal of the image sensor 36 is converted into a digital signal of Nb1t representing the density of each pixel.

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 scanning into a plurality of blocks and detects the peak value of the image signal of each block.

■The image signal obtained by scanning 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, one scanning line is divided into an arbitrary number of blocks every N bits.

Block setting circuit 65 is cleared by H5YNC,
The clock CLKI from the clock control circuit 11 is counted, and a reset signal R5I is output to the peak value detection circuit 64 every N counts. Therefore, two adjacent H5
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, the output of the block setting circuit 65.

By using the reset signal RSI for the peak value detection circuit 64, the peak value detection circuit 64 always detects the peak value for 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, 151 indicates the entire reading range of the line sensor, and 52 indicates the threshold determination area. Like this,
In order to determine the threshold value, a smaller area is defined instead of the entire reading range, and only the peak values obtained from this area are used as valid peak values for determining the threshold value. 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 be set to a size and position where the image will always exist.

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 (Do-Dm') representing the area start point with the address (Dm' + 1 to Dm) representing the area end point. do.

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 H2SYNC signal as a synchronization signal to start counting, counts the R31 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 an l 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, 68 is a gate circuit, and the block area determined by the block address setting circuit 67,
A two-dimensional area 52t, as shown in FIG. 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 that creates various timing clocks that serve as operating standards for the device.

72 is a comparator for obtaining a binary 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. Can be set arbitrarily. Reference numeral 75 denotes a latch circuit for taking in the approximate base density signal into the control section 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.

When the image frame to be read on the microfilm is set at a predetermined reading position and ready for reading operation, and an AE operation start command is input from the CPU 301 shown in the second figure, the control unit 70 starts the process for binarizing the image data. In order to start the first image reading to determine the threshold value of The density data is taken in the threshold value determination area set in advance as described above (S L 3 , S
l5).

In this way, when the first image reading is completed (517), the lamp 32 is turned off, and the line sensor 36 is turned off.
(518°S L 9). Then, using each of the captured data, the control unit 70 determines the threshold value for binarizing the image signal (I) and (I) in FIG.
A histogram as shown in I) is created with the density level on the X axis and the frequency on the Y axis (S14°516). In FIG. 10, 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 density component, which 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. This is a graph obtained by sampling peak value data within the above-mentioned threshold value determination region, that is, in the case of NECA film, data of a portion where the amount of light transmitted is the largest.

In addition, the graph (II) has bimodal characteristics; the peak on the lower side of the density level indicates the base density part, the peak on the higher side indicates the peak value part of the image signal, and the density level x2 is the first base density part. This is the location where the signal peak value level is the highest in the sample image area of the density film.

In the graph (I), Xl is a density level that indicates a value close to the base density in the sample image area (referred to as approximate base density), and is the density level that is the most common density in the sample data obtained by the base density detection circuit 74. level. Xl'
is the tenobase 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 density representative value x2 of the image signal are detected (S201), and the difference between these two values, that is, the value 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 by and output as two individual numbers.

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. 34tk fi This is the main lens for adjusting point i, and is equipped with a mechanism that moves 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 allows one screen of the image on the film to be read line by line sequentially.

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

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

The rise of the two individual numbers 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 the number of etches increases, the more the focus moves, 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 you move away 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.

This output waveform is binarized by the image processing circuit 304 to obtain the output signal CS shown in FIG. 12(b). Next, this signal C
5 is input to the counter 22. The counter 22 receives a reset signal R3 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 above reset.

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

Figure i13 (a) shows the state of just focus, (b) shows
Indicates an out-of-focus condition.

When main scanning is performed between fix and fi2 in (I) of FIG. 13(a) by the image sensor 36, FIG. 13(a)
The waveform will be as shown in (II).

(The actual output signal has a step-like shape, but is omitted for ease of explanation). Here, if this output J signal is converted to a threshold TLTZ value, an output signal CS like (III) in Fig. 13(a) is obtained.
get. (Just Bin/Time) Next, the out-of-focus situation 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 the vertical position 1 and the vertical position 2. Here, the output signal from the image sensor 36 (
II), the number of times it crosses the threshold TL decreases, and the output signal C8 rises as shown in (III) in FIG. 13(b). e'4. It ended up being 3 digits of e'4,
It can be seen that the number of edges 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 S3
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. The count value (number of focus information) of the counter 22 is captured every time the image sensor 36 main scans one line and is stored in the built-in memory.At this time, the number of steps of the pulse motor is also stored.Then, 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 1/1/2 step 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 220 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 reaches the end point, the process proceeds to step S35, where the maximum count value (+rj) 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 driving device 10 moves the lens 34 to the position corresponding to the recognized number of steps.
The pulse motor is driven (S36), thereby setting the lens 34 to the just-focus position. When the setting of the lens 34 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.

In addition to reading microfilm, it can also be applied to reading 35mm film and X-ray film, and the light amount control operation, AE operation, and autofocus operation can also be achieved with other configurations. Needless to say.

〔effect〕

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 before the film is transported to the reading position, 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 demonstrate the functions of each operation, and it is possible to read good film images without the need for human intervention. be.

[Brief explanation of the drawings] Figure 1 is a schematic diagram of the microfilm reading device, 8
FIG. 2 is a diagram showing an example of the configuration of a control and processing circuit of the reading device shown in FIG. FIG. 5 is a flowchart showing the control procedure of the control unit 141, FIG. 6 is a diagram showing an example of the output characteristics of the image sensor with respect to the amount of input light, FIG. 7 is a diagram showing an example of the configuration of the image processing circuit, and FIG. 9 is a flowchart showing a control procedure of the control unit 70, FIG. 10 is a diagram showing an example of the configuration of an autofocus circuit, and FIG. 11(a). (b) is a diagram showing the image state recorded on the film, FIG. 12 is a diagram showing the output of the image sensor, and FIG. 13 (a
), (b) are diagrams showing the principle of focusing operation, and FIG. 14 is a flow chart diagram showing the control procedure of the control unit 21.
32 is a light source, 34 is a lens, and 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, 30
5 is a recording device.

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 that is illuminated by a light source, the exposure amount is adjusted before loading the film to the reading position, and then the film is moved to the reading position. The focus is adjusted using the transmitted light of the film.
A film reading device characterized in that a threshold value for quantizing the photoelectrically converted image information is then determined based on the image density.