JPS63172113A - Control method for optical device - Google Patents

Abstract

PURPOSE:To considerably shorten the time required for control of the exposure by storing a rough driving frequency corresponding to the correct exposure of an image sensor for each interchangeable lens and driving the image sensor with the driving frequency corresponding to a selected lens at the time of replacing a lens. CONSTITUTION:A correction curve for the illuminance variance of each lens is preliminarily stored in a memory 86, and a CPU 52 corrects a contrast C and an output signal d' or slice levels Sn and Sp for a turning position theta of a line sensor 40. The driving frequency of the line sensor 40 corresponding to an approximately correct exposure for lens power is preliminarily stored in a memory 88 for each interchangeable lens; and since this frequency determines the rough exposure of the line sensor 40 for each interchangeable lens and a comparator 68 has a blooming preventing function, such driving frequency is stored in the memory that the exposure is rather on the blooming side. Thus, the exposure of the image sensor is certainly entered in the correct range and the operation time when the driving frequency in this range is obtained is very shortened at the time of lens replacement.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a control method applied to an optical device having a plurality of interchangeable lenses, such as a league printer, a microscope, and a magnifying projector.

(Technical Background of the Invention) There is a reader printer that forms a projected image of an original microphotograph on a screen or a photoreceptor so that the enlarged projected image can be viewed on the screen or a hard copy can be obtained by forming the image on the photoreceptor. be. In this type of device, a part of the projected image is guided to a CCD image sensor such as a line sensor, and it is determined whether or not it is in focus based on the contrast of the image obtained from the output of this line sensor, and the state is brought into focus. It has been considered to control the optical system of the projected image in this way.

However, if the projection lens were made interchangeable, the illuminance of the projected image would change significantly each time the lens was replaced.
The exposure amount of the line sensor will change drastically. Conventionally, the driving frequency of the line sensor has been controlled so that the output signal of the line sensor falls within a certain range, but when the exposure amount fluctuates extremely like this, it is difficult to keep the output signal within the appropriate range. There is a problem in that it is difficult to quickly detect the incoming drive frequency, and the time required for detection is long.

(Objective of the Invention) The present invention was made in view of the above circumstances, and it is an object of the present invention to quickly adjust the driving frequency so that the exposure amount of the image sensor falls within an appropriate range when the exposure amount of the projected image changes significantly due to lens exchange. It is an object of the present invention to provide a control method for an optical device that can significantly shorten the time required to determine the exposure amount and control the exposure amount.

(Structure of the Invention) According to the present invention, this object is provided in an optical device that guides a projected image to a CCD image sensor through one of the interchangeable lenses and performs an autofocus operation based on an output signal of the image sensor. A rough driving frequency corresponding to the appropriate exposure amount of the image sensor is stored in advance for each interchangeable lens, and when replacing lenses, the driving frequency corresponding to the selected lens is read out and the image sensor is driven at this frequency. This is achieved by a method for controlling an optical device characterized by the following.

(Embodiment) Fig. 1 is an overall schematic diagram of a league printer which is an embodiment of the present invention, Fig. 2 is a front view of the screen showing the movement range of the line sensor, Fig. 3 is a block diagram of the control system, Fourth
The figure and FIG. 5 show the original image and the output waveform of a specific pixel when the line sensor is moved. FIG. 4 is for a negative original image, and FIG. 5 is for a positive original image. Further, FIG. 6 is a diagram of output waveforms of various parts in the process of determining contrast, and FIG. 7 is a flowchart of the image detection operation.

In FIG. 1, reference numeral 10 is an original image of a microphotograph such as microfiche or microroll film. 1
2 is a light source, and the light from the light source 12 is passed through a condenser lens 14.
, a heat shielding filter 16, and a reflecting mirror 18, and are guided to the lower surface of the original image 10. In the reader mode, transmitted light (projection image) of the original image 10 is transmitted through the projection lens 20 and the reflecting mirror 22.2.
4.26 to a transmissive screen 28, on which an enlarged projected image of the original image 10 is formed. In the printer mode, the reflecting mirror 24 is rotated to the imaginary line position in FIG. 1, and the projected light is guided to the PPC type slit exposure type printer 34 by the reflecting mirrors 22, 30, 32.

The reflecting mirrors 22 and 30 move in synchronization with the rotation of the photosensitive drum 36 of the printer 34, and a latent image is formed on the photosensitive drum 36. This latent image is made visible by toner charged to a predetermined polarity, and this toner image is transferred onto the transfer paper 38. Note that a plurality of projection lenses 2o are prepared and can be replaced. The magnification and type of the lens 20 used are detected by a lens sensor 84, which will be described later.

40 is a CCD line sensor, and this line sensor 4
0 is attached to the rotating end of a rotating arm 42 that rotates around the outside of the upper left corner of the screen 28 as a fulcrum. This rotating arm 42 is rotated by a motor 44 within a shaded area in FIG. This motor 44, that is, the rotating arm 42
The rotation angle θ is detected by the rotary encoder 46.

50 is a control means, which changes the slice level for image detection based on the output of a specific pixel of the line sensor 40 while moving the line sensor 40, and in parallel determines the presence or absence of an appropriate image. perform image detection operations. The control means 50 also performs focus determination based on the output signal of the line sensor 48, and controls the projection lens 20 by the motor 5.
1 (Fig. 1), autofocus operation to move to the focus position, control of the printer 34, and reflection mirror 22.24.
．． 30 movements, etc.

A control system including this control means 50 is constructed as shown in FIG. That is, the CPU 52 sends a signal a commanding an appropriate frequency to the clock generator 54, and the clock generator 54 sends a drive pulse b of the commanded frequency to the line sensor 40. The line sensor 40 sequentially sends out the output signal C of each pixel to the amplifier 56 by this driving pulse b. In this way, the main scanning of the line sensor 40 is performed. This output signal C is amplified by an amplifier 56 and becomes an output signal d (see FIG. 6(I)).

This output signal d is converted into a signal e shown in FIG. 6(II) by a bandpass filter 58, and then input to a peak hold circuit 60 to be converted into a contrast signal C shown in FIG. 6(m). The maximum value of this signal C becomes the contrast in this one seven scan. Note that in FIG. 6, the horizontal axis indicates the pixel order of the line sensor 40.

The output signal d is also input to a sample-and-hold circuit 62, which is connected to a clock generator 54.
synchronization signal b that is output in synchronization with the output signal of a specific pixel
', only the output signal d' of this specific pixel is temporarily stored. 64 is a changeover switch, and this switch 64
In response to a command from the CPU 52, the output signal d' stored in the sample hold circuit 62 during main scanning is read into the CPU 52 via the A/D converter 66, while at the end of the main scanning, the output signal d' stored in the peak hold circuit 60 is read into the CPU 52. contrast C
is read into the CPU 52 via the A/D converter 66. C.P.
U52 determines and temporarily stores the peak value D (max) and minimum value D (mim) of the output signal d', and also temporarily stores the contrast C.

The output signal d is also input to the non-inverting input of a comparator 68 for blooming detection. The output level at which blooming occurs, set by the setter 70, is input to the inverting input terminal of the comparator 68.

Therefore, comparator 68 is logic +1 when blooming occurs.
A blooming signal f of 111 is input to the CPU 52. At this time, the CPU 52 changes the signal a so as to increase the driving frequency of the line sensor 40 and shorten the accumulation time of the line sensor 40 in order to reduce the exposure amount of the line sensor 40.

The output signal d is further input to the non-inverting input of a comparator 72,74. A comparator 72 determines the slice level S for the negative original image. The minimum value D (min) of the output signal d' stored in the CPU 52 is added to the predetermined value α (D (min
) + α) is input via the D/A converter 76.

This (D(min)+α) indicates the slice level Sn for the negative original image. The comparator 74 is used to determine the slice level sp for the positive original image, and its inverting input terminal has a predetermined value β subtracted from the peak value D (max) of the output signal d' stored in the CPU 52 (D ( m
ax)-β) is manually input via the D/A converter 78. This (D(max)-β) indicates the slice level Sp for the positive original image.

The output signals d of the comparators 72 and 74 are each at the slice level S. , S3 or higher, a signal of logic "1'' is sent to the counter 80.82, and the counter 80.82 counts the number of times the output of the comparator 72.74 becomes the logic P11, and sends it to the CPU 52. That is, line sensor 4
If the above operation is repeated while moving 0 in the sub-scanning direction perpendicular to the main-scanning direction (longitudinal direction), the output signal d will reach the slice level S. , Sp exceeds the counter 80.
1 is added to 82. If this count value exceeds a certain number, it is assumed that an image exists.

Considering that this constant count value may be counted incorrectly due to dust attached to the original film, it is not desirable to set rlJ to "2", and for example, set it to "4" or more. It is better.

In FIG. 1.3, 84 is a lens sensor that detects the magnification and type of the projection lens 20, and the CPU 52 detects the magnification of the projection lens 20 based on the output of this sensor 84. In general, the illuminance on the screen 28 decreases as the distance from the optical axis increases, and this illuminance unevenness is almost uniquely determined by the magnification of the projection lens 20. A correction curve for uneven illuminance for each lens is stored in advance in the memory 86 in FIG.
U52 is the contrast C and the output signal d' or the slice level S with respect to the rotational position θ of the line sensor 40.
Correct n and Sp.

Reference numeral 88 denotes a memory according to the present invention, and the drive frequency of the line sensor 40 at which the exposure amount is approximately appropriate for the magnification of the lens 20 is stored in advance for each interchangeable lens. It is sufficient to determine this frequency by determining the rough exposure amount of the line sensor 40 for each interchangeable lens, and especially in this embodiment, the comparator 68 described above has a blooming prevention function that detects blooming and reduces the exposure needle.
It is desirable to store a drive frequency in this memory 88 so that the exposure amount is slightly blooming.

The memory 90 stores the past focus position of each lens 20 detected by the sensor 84.

Each time the lens 20 is replaced, the CPU 52 reads the past lens focusing position of the lens determined based on the output of the sensor 84 from this memory 90, and prior to the image detection operation and the autofocus operation, the CPU 52 reads out the past lens focusing position of the lens determined based on the output of the sensor 84. the focus position.

This prevents the occurrence of an inoperable state due to the lens 20 being significantly moved away from the in-focus position and the projected image being significantly blurred.

Next, the operation of this embodiment will be explained. The user first selects and attaches the projection lens 20 of desired magnification. Next, the user selects the reader mode in which the reflecting mirror 24 is placed at the solid line position in FIG. 1, and the target original image is projected onto the screen 28. C.P.
U52 determines the magnification and type of projection lens 20 based on the output signal of lens sensor 84 (step 100,
Figure 7). Further, the CPU 52 reads out the past focus position of the projection lens 20 from the memory 90 based on the output signal of the lens sensor 84, and controls the motor 51 to move the lens 20 to this focus position.

The CPU 52 further reads out the driving frequency of the line sensor 40 corresponding to the magnification or type of the lens 20 used from the memory 88, and outputs a signal a instructing this frequency to the clock generator 54 (step 102). CPU5
2 also reads the correction curve for illuminance unevenness from the memory 86 into the memory in the CPU 52 according to the magnification of the lens 20, and preparations for autofocus operation are completed.

When the user selects the autofocus mode using a switch (not shown) (step 104), the CPU 52 displays the line sensor 40 on the screen 28 shown by a solid line in FIG.
The motor 44 is started to move the line sensor 40 from the upper outer position into the screen 28 (step 106).The rotation angle θ of the line sensor 40 is detected by the encoder 46, and when the rotation angle θ is within the range e shown in FIG. First, the image detection operation begins (step 108).

This range θ also overlaps with the rectangular range X at the center of the screen 28. For example, this rectangular range X corresponds to the range that overlaps when A4 size enlarged images are projected vertically and horizontally onto the center of the screen 28, and there is a possibility that the image will always exist regardless of whether the original image is vertically or horizontally oriented. is also in a very high range.

When the line sensor 40 enters the range of θ, a predetermined operation is performed using the output signal d, other signals, the contents of the memory, etc.

This output signal d is compared with a set value of the output level at which blooming occurs in the comparator 68 (step 110).
), if blooming occurs, the output signal f is
1'', the CPU 52 sends a signal a that instructs the line sensor 40 to increase its driving frequency and decrease its exposure amount.
is sent to the clock generator 54 (step 112).

If no blooming occurs, the line sensor 40
The output signal d' of one or more specific pixels is temporarily stored in the sample-hold circuit 62 by the output signal b' of the clock generator 54, while the contrast C obtained by - times of main scanning is stored in the peak-hold circuit 60. Ru. By switching the switch 64, the output signal d' and the contrast C are read into the CPU 52 for each main scan.

While the line sensor 40 is moving, the CPU 52
or monitor changes in the output signal d' of a plurality of specific pixels,
The peak value D (max) and minimum value D (min) are continuously determined (step 114).

FIG. 4(A) shows the locus of movement of this particular pixel with respect to the negative original image, and FIG. 4(B) shows the change in the output signal d' at that time with respect to the moving pressure fl1M. Also, Fig. 5 (A),
(B) is also for a positive original image. Naofumi =
The range of no or more corresponds to the range X in FIG. 2,
The CPU 52 uses the subsequent output signal d' to determine the peak value and minimum value.

The CPU 52 calculates a predetermined value α from these minimum values and peak values.
, β are respectively added and subtracted, and Sn = D (min) + a S, = D (max) - β are set as slice levels for the negative and positive original images, respectively (step 116).

Further, the predetermined values α and β are 0.1 to 0.6 of the minimum value and peak value when expressed as an optical density expressed by the logarithm of the ratio F/FO of the transmitted light flux Fo and the incident light flux F.
, preferably set to about 0.2 to 0.4.

The CPU 52 converts these slice levels Sn and Sp into D/A
Transducer 76.78. The comparators 72 and 74 output 111 signals each time the output signal d exceeds the slice level Sn, Sp.
11, and counters 80 and 82 count this number. That is, as shown in FIG. 4.5 (B), as the line sensor 40 moves, the minimum value (min
), peak value D (max) and slice level Sn
, Sp keep changing, and if there is an image, the output signal d from the main scanning at that time changes greatly, so if the original is a negative one, the count value of the counter 80 will increase, and if the original is a positive one, the count value of the counter 82 will increase. . If these count values exceed a predetermined value (for example, 4), the CPU 52 determines that the slice levels Sn and Sp at that time are appropriate and that there is an image (step 118), and stops the line sensor 40 (step 120). Repeating the operations of steps 108 to 118 above (step 122), if it is not determined that there is an image (step 118.122),
It is determined that there is an abnormality and a command is given to move the lens or the autofocus operation is stopped (step 124).

The accuracy of the slice levels Sn and Sp is determined by the line sensor 40.
The accuracy increases as the number of times the line sensor 40 moves and the number of main scans increases, but in general, if the line sensor 40 moves and main scans about 10 to 20 times, sufficient accuracy is obtained.

Next, the control means 50 outputs the output signal d of this line sensor 40.
Performs autofocus control based on

Various algorithms are possible for this control.

For example, the line sensor 40 is located at the position where the projection lens 20 is located.
The maximum and minimum brightness I obtained from the output voltage of each pixel in
(M), I (m), and detect the position of the projection lens 20 where the visibility V defined by the following formula %()) is maximized while sequentially moving the projection lens 20. Alternatively, the projection lens 20 may be moved once across the focused point, and the focused point may be determined from the half-width of the luminance change characteristic curve at that time (half-width method), or the projection lens 20 may be moved once across the entire range. 20 may be moved to find the position where the brightness I is maximum (full scan method). When autofocus control is completed in this way, the control means 5
0 drives the motor 44 in the opposite direction to move the line sensor 40 out of the screen 28.

After viewing the enlarged projected image appearing on the screen 28, if the printer mode is selected, the reflecting mirror 24 is rotated to the position shown by the imaginary line in FIG. 1, and the image is transferred onto the transfer paper 38 to obtain a hard copy.

Although the above embodiments apply the present invention to a reader printer, the present invention can also be applied to optical devices such as microscopes and magnifying projectors 4, and especially to other optical devices with constant light source illuminance and interchangeable lenses. This includes these things.

Further, in the above embodiments, the line sensor 40 is moved along an arcuate trajectory, but the present invention is not limited to this, and also includes one in which the line sensor 40 is moved linearly in a direction orthogonal to the line sensor.

(Effects of the Invention) As described above, the present invention stores in advance a driving frequency that is generally suitable for driving an image sensor for each interchangeable lens, reads out this driving frequency corresponding to the selected lens, and drives the image sensor. It is first driven at this frequency. Therefore, the exposure amount of the image sensor is always within the appropriate range, and the operation time required to find a driving frequency that falls within this appropriate range when exchanging lenses becomes extremely short.

Therefore, even if more precise exposure control is subsequently performed to obtain the optimum exposure amount, the overall operating time is significantly shortened.

[Brief explanation of the drawing]

Fig. 1 is an overall schematic diagram of a reader printer that is an embodiment of the present invention, Fig. 2 is a front view of the screen showing the moving range of the line sensor, Fig. 3 is a block diagram of the control system, and Fig. 4 is a block diagram of the control system.
The figure and FIG. 5 show the original image and the output waveform of a specific pixel after moving the line sensor, and FIG. 4 shows the waveform for the negative original image, and FIG. 5 shows the waveform for the positive original image. Further, FIG. 6 is a diagram of output waveforms of various parts in the process of obtaining a contrast signal, and FIG. 7 is a flowchart of the image detection operation. DESCRIPTION OF SYMBOLS 10... Original picture, 20... Projection lens, 28... Screen, 40... CCD line sensor 9 as an image sensor 52... CPU, 88... Memory, d... Output signal.

Claims (1)

[Scope of Claims] An optical device that guides a projected image to a CCD image sensor through one of the interchangeable lenses and performs an autofocus operation based on an output signal of the image sensor, comprising: An optical device characterized in that a corresponding rough driving frequency is stored in advance for each interchangeable lens, and when exchanging lenses, the driving frequency corresponding to the selected lens is read out and the image sensor is driven at this frequency. Control method.