JP2001209127A - Film position detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the position of film in a longitudinal direction in a wide range. SOLUTION: The first electrode 8 (partial electrodes 12 and 14) of first and second sensors 4 and 6 is arranged by having an interval at the perforation part of the film 102, and a second electrode 10 is arranged on the opposite side of the film 102. The electrostatic capacity of each sensor between the first and second electrodes 8 and 10 is changed by a positional relation between the first electrode 8 and the perforation 104, so that the position of the film 102 is detected based on the change of the electrostatic capacity. Then, two first electrodes 8 are arranged by a pitch 1/4 longer than the array pitch of the perforation 104, so that the electrostatic capacity of each sensor is changed so as to shift a phase by the 1/4 pitch with respect to the positional change of the film 102. Thus, only an area in which the electrostatic capacity of each sensor is changed with excellent linearity is switched and used, so that excellent detection accuracy is secured in the wide range.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for detecting a position in a running direction of a video film when the video film is run to project an image recorded on the video film on a screen or the like.

[0002]

2. Description of the Related Art FIG. 11 is a front view showing an example of a conventional video film. As shown in FIG. 11, the video film 102 (also simply referred to as the film 102) has a strip shape, and the perforations 104 (perforation 10
4) are formed at a predetermined pitch, and rectangular video recording areas 106 are arranged in the center in the longitudinal direction of the film. A band-shaped audio recording area 107 is formed between one of the perforation rows and the video recording area row.

A film position detecting device is incorporated in a projector for projecting an image on a screen by using such a film 102, a film information digitizing device for digitizing information recorded on the film 102 (also referred to as a telecine device), and the like. It is. FIG. 12 is a configuration diagram showing an example of a conventional telecine device. In the telecine device 108 shown in FIG.
0, 112, intermittently fed by the running system 114,
When the film position detecting device detects that the recording area of the film 102 has stopped at a predetermined position of the gate unit 116, the shutter 120 of the light projecting unit 118 is opened, and light is emitted from the light source 122. As a result, the image recorded on the film 102 is corrected by the optical axis correction / projection lens unit 1.
A photographing unit 126 constituted by a TV camera or the like through 24
Projected toward.

In such a telecine device 108, the position in the longitudinal direction of the film 102 stopped after the intermittent feeding slightly changes for each frame, so that a projection image shakes and causes deterioration in image quality. Therefore, conventionally, the position of the film 102 is detected by a film position detecting device, and based on the detection result, the light entering the photographing unit 126 in the optical axis correction / projection lens unit 124 is slightly shifted in the longitudinal direction of the film, and I was trying to eliminate the swing.

Accordingly, it is important to improve the film position detection accuracy in order to improve the image quality.
No. 127611 discloses a technique for accurately detecting a film position based on a change in capacitance. FIG.
FIG. 1 is a film front view showing a periphery of a sensor used in the conventional film position detecting technique. In the figure, the same elements as those in FIG. 11 are denoted by the same reference numerals. Position sensor 128
Includes a ground electrode 130 and a detection electrode 132, and the ground electrode 130 and the detection electrode 132 are arranged at positions where the perforations 104 are arranged with the film 102 interposed therebetween. In this example, the detection electrode 132 is 2
The partial electrodes 134 and 136 are arranged at intervals in the longitudinal direction of the film 102.

Since the detection electrode 132 and the ground electrode 130 are arranged with the film 102 interposed therebetween, a capacitance is formed between these electrodes. And film 1
02 is higher than the permittivity of air, the detection electrode 132 and the ground electrode 130 are located when the perforation 104 is directly below the detection electrode 132 (the state shown in FIG. 13).
And between the two adjacent perforations 104 is the detection electrode 132
, The capacitance is highest.

FIG. 14 shows the detection electrode 132 and the ground electrode 1.
It is a graph which shows the change of the electrostatic capacitance between 30. In the figure, the horizontal axis represents the position in the longitudinal direction of the film 102, and the vertical axis represents the capacitance. In FIG. 14, when the film position is the position P1 where the capacitance is the largest,
An intermediate point between two adjacent perforations 104 is directly below the detection electrode 132, while the perforation 104 is directly below the detection electrode 132 at the position P <b> 2 where the capacitance is the smallest. At other film positions, the capacitance has an intermediate value and changes in a sine wave shape. Therefore, the position in the longitudinal direction of the film 102 can be detected by detecting the capacitance between the detection electrode 132 and the ground electrode 130.

In FIG. 13, four detection electrodes 132 are provided, each of which forms a pair with the ground electrode 130 to form a capacitance, and the film position can be individually detected. By using all of the detection results from the detection electrodes 132, it is possible to suppress the influence of variations in the detection results from the individual detection electrodes 132.

[0009]

By the way, in order to detect the film position with high accuracy, it is necessary that the capacitance changes as greatly as possible with respect to the change in the film position and changes linearly. However, referring to FIG. 14, the film position P at which the capacitance becomes the maximum and the minimum is obtained.
1, near P2, the change in capacitance is small and the linearity is poor. Therefore, the film position can be accurately detected by such a conventional film position detection device is limited to the vicinity of the region R where the change is large and the linearity is good, and the film position is accurately detected in other regions. It is impossible to detect. The present invention has been made to solve such a problem, and an object of the present invention is to provide a film position detecting device capable of accurately detecting a position in a longitudinal direction of a film over a wide range.

[0010]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides a method of feeding a film having a belt shape and having perforations formed at a constant pitch in the longitudinal direction when the film is fed in the longitudinal direction. An apparatus for detecting, comprising first and second sensors and sensor switching means, wherein each of the first and second sensors has a predetermined detecting portion near a running path of the film in a longitudinal direction of the film. Arranged at a pitch, the first and second sensors each output a signal of a magnitude corresponding to a distance in a film longitudinal direction between the detection unit and the perforation closest to the detection unit, The arrangement pitch of the detection units of the first and second sensors is an integer of 0 or more in the arrangement pitch of the perforations in the film longitudinal direction. The first length multiplied by a second length greater than 0 and equal to or less than 1/4 of the arrangement pitch of the perforations is added or the second length is subtracted from the first length. The sensor switching means selects an output signal of one of the first and second sensors in accordance with the magnitude of the output signal of one or both of the first and second sensors, and selects a length of the film. It is characterized in that it is output as a detection result of the position in the direction.

In the film position detecting device of the present invention, the first
And the second sensor each output a signal of a magnitude corresponding to the distance in the longitudinal direction of the film between the detecting unit and the perforation closest to the detecting unit, so that when the position in the longitudinal direction of the film changes. , The magnitude of the output signals of the first and second sensors changes at a period corresponding to the arrangement pitch of the perforations. And the first
And the arrangement pitch of the detection units of the second sensor is 0 in the arrangement pitch of the perforations in the longitudinal direction of the film.
The first length multiplied by the above integer is added to a second length greater than 0 and equal to or less than 1/4 of the perforation arrangement pitch, or the second length is subtracted from the first length. Since the length is almost equal to the above, when the film position changes as described above, the output signals of the first and the second sensors become the second signal.
Phase shifts by the length of.

Therefore, even if the magnitude of the output signal of one sensor is close to the maximum value or the minimum value and the change in film position is small and the linearity is poor, the other sensor Is always deviated from the maximum value or the minimum value, changes sufficiently with changes in film position, and changes with good linearity.
As a result, the signal of the film position detection result output by the sensor switching means changes linearly and sufficiently over a wider range with respect to the change of the film position. By performing the optical axis correction of the projection light using the detection result of the above, it is possible to more reliably suppress the positional deviation of the projected image due to the positional change in the longitudinal direction of the film and obtain a high-quality image.

[0013]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a front view showing a sensor unit constituting an example of a film position detecting device according to the present invention. FIG. 2 is a block diagram showing a detection circuit for detecting a film position by a signal from the sensor unit shown in FIG. 3
1 is a configuration diagram illustrating a telecine device incorporating a film position detection device according to an embodiment. In the drawings, the same elements as those in FIGS. 11 to 13 are denoted by the same reference numerals, and a detailed description thereof will be omitted here.

A film position detecting device 2 according to the present embodiment.
(FIG. 2) is an apparatus for detecting the position of the film 102 in the longitudinal direction when the film 102 having a belt-like shape and having perforations 104 formed at a constant pitch in the longitudinal direction as shown in FIG. The first and second sensors 4 and 6 shown in FIGS. 1 and 2 and the detection circuit 7 are included.

In the present embodiment, the first and second sensors 4 and 6 are connected to a gate section 116 forming a film traveling path.
In FIG. 3, the first and second electrodes 8 and 10 disposed at positions where the perforations 104 pass with the film 102 interposed therebetween, and constitute a detection unit of the present invention.
The first electrode 8 and the perforation closest to the first electrode 8 are based on the fact that the capacitance between the first and second electrodes 8 and 10 changes according to the positional relationship between the first electrode 8 and the perforation 104. A signal having a magnitude corresponding to the distance in the longitudinal direction of the film from the signal 104 is output.

In this embodiment, the first electrode 8 is composed of two partial electrodes 12 and 14,
Reference numerals 14 are arranged at intervals in the longitudinal direction of the film 102. The length of the partial electrodes 12 and 14 in the longitudinal direction of the film is set shorter than the length of the perforations 104 in the longitudinal direction of the film. Further, in the present embodiment, the second electrode 10 is provided commonly to the first and second sensors 4 and 6. However, the second
It is of course possible to provide the electrodes 10 individually for each first electrode 8. In this embodiment, the arrangement pitch of the first electrodes 8 of the first and second sensors 4 and 6 is, for example, an arrangement pitch L of the perforations 104 in the film longitudinal direction (the first length according to the present invention). ) Plus a length of １ ／ of the arrangement pitch of the perforations 104 (a second length according to the present invention).

As shown in FIG. 2, the detection circuit 7 amplifies signals from the oscillator 18, which applies an AC voltage to the respective partial electrodes 12, 14 through the resistor 16, and the signals from the first and second sensors 4, 6. Differential amplifier circuits 20 and 22, detection circuit (DE
T) 24, 26, and a sensor switching circuit 28 (sensor switching means according to the present invention).

In this embodiment, the first sensor 4
The first electrode 8 (on the right side in FIG. 2), the second electrode 10, the corresponding resistor 16, the oscillator 18, the differential amplifier circuit 20, and the detection circuit 24, and the second sensor 6 It comprises an electrode 8 (left side in FIG. 2), a second electrode 10, a corresponding resistor 16, an oscillator 18, a differential amplifier circuit 22, and a detection circuit 26.

The sensor switching circuit 28 controls the output voltage of one of the sensors in accordance with the magnitude of the output voltage 30, 32 of the first and second sensors 4, 6 (ie, the output voltage of the detection circuits 24, 26). Is output as a detection result of the position of the film 102 in the longitudinal direction. Also,
In the present embodiment, the sensor switching circuit 28 includes the first and second sensors 4 and 6 as described in detail below.
Of the selected signal is performed based on the magnitude of the output voltage.

Next, the operation of the film position detecting device 2 configured as described above will be described. A partial electrode 12 of the first electrode 8 constituting the first and second sensors 4 and 6;
Since an AC voltage is applied to each of the electrodes 14 from the oscillator 18 through the resistor 16, an AC voltage corresponding to each capacitance is generated between the second electrode 10 and each of the partial electrodes 12 and 14. I do. Partial electrode 1 of first sensor 4
2 and 14 are input to a differential amplifier circuit 20. The differential amplifier circuit 20 amplifies and outputs these voltage differences, while the voltages of the partial electrodes 12 and 14 of the second sensor 6 are different. The differential amplifier circuit 22 amplifies these voltage differences and outputs the amplified voltage difference.

Therefore, for example, when the first and second sensors 4 and 6 and the film 102 are in a positional relationship as shown in FIGS. 1 and 2, the first sensor 4 Since the capacitance difference between the second electrode 10 and the second electrode 10 is small, the voltage difference between the partial electrodes 12 and 14 is small, and the differential amplifier circuit 20 outputs an AC voltage having a small amplitude. On the other hand, in the second sensor 6, the voltage difference is large because the capacitance difference between the partial electrodes 12 and 14 is large.
Outputs an AC voltage having a large amplitude. Detection circuit 24, 2
Reference numeral 6 detects the AC voltages output from the differential amplifier circuits 20 and 22, respectively, and outputs the detection results as sensor output voltages 30 and 32.

FIG. 4 is a graph showing how the output voltage of each sensor changes depending on the film position. In the figure, the horizontal axis represents the film position in the longitudinal direction of the film, and the vertical axis represents the output voltage of the sensor. As shown in FIG. 4, the output voltage 30, 32 of each sensor is the arrangement pitch L of the perforations 104 in the longitudinal direction of the film.
And changes in a sine wave shape with the cycle of. Output voltage of each sensor 3
0 and 32 are maximum when, for example, the partial electrode 12 of the first electrode 8 is in the region of the perforation 104 and the partial electrode 14 is in the region between two adjacent perforations 104. Conversely, the output voltage 30, 32 of each sensor is minimized, for example, because the partial electrode 14 of the first electrode 8 is in the region of the perforation 104 and the partial electrode 12 is located between the two adjacent perforations 104. This is the case in the area. The output voltage of each sensor becomes 0 when the partial electrodes 12 and 14 are equally applied to the edge of the perforation 104 as in the case of the first sensor 4 shown in FIG. . Then, the first and second sensors 4 and 6
As described above, the arrangement pitch of the perforations 104 is L, and the arrangement pitch of the electrodes 8 is L × (1 + 1 /
4), when the film position changes, the output voltages of the first and second sensors 4 and 6 change in phase with each other by L / 4 as shown in FIG.

The sensor switching circuit 28 selects one of the output voltages 30 and 32 of one of the sensors according to the magnitude of the output voltage 30 or 32 of the first and second sensors 4 and 6 and It is output as the result of detecting the position in the direction. Specifically, as shown in FIG. 4, in a region 36 where the output voltage 32 of the second sensor 6 is smaller than the switching voltage 34, the sensor switching circuit 28 selects the output voltage 30 of the first sensor 4 and Output. Meanwhile, the first
In a region 40 where the output voltage 30 of the sensor 4 is larger than the switching voltage 38, the sensor switching circuit 28 selects and outputs the output voltage 32 of the second sensor 6.

Further, in a region 42 in which the output voltage 32 of the first sensor 4 is larger than the switching voltage 38, the sensor switching circuit 28 selects the output voltage 30 of the first sensor 4 and outputs the output voltage 30 with its polarity inverted. . On the other hand, in an area 44 where the output voltage 30 of the first sensor 4 is smaller than the switching voltage 34, the sensor switching circuit 28
Is selected, and the polarity is inverted for output.

FIG. 5 is a graph showing a change in the output voltage of the sensor switching circuit 28. In the figure, the horizontal axis represents the position of the film 102 in the longitudinal direction of the film, and the vertical axis represents the voltage. As a result of the sensor switching circuit 28 operating as described above, the output voltage 46 thereof changes with respect to the change in the film position in the longitudinal direction with respect to the regions 36, 4 and 4 described above.
Each of 0, 42, and 44 is linear and changes at a sufficient change rate. Thus, the output voltage 46 of the sensor switching circuit 28 changes linearly and sufficiently over the entire range of the arrangement pitch L of the perforations 104. Therefore, by controlling the optical axis correction / projection lens unit 124 using the output voltage 46 of the sensor switching circuit 28, the film 102
In this case, it is possible to obtain a high-quality image by further reliably suppressing the fluctuation of the projection image due to the positional change in the longitudinal direction.

In this embodiment, as described above, the sensor switching circuit 28 also inverts the sensor output voltage based on the magnitude of the sensor output voltage, but does not perform such an inversion operation. As well as the areas 36 and 40
Alternatively, sufficient linearity and change rate can be secured in the regions 42 and 44, and the region where such good characteristics can be obtained is doubled as compared with the related art.

In this case, the sensor switching circuit 28 selects one of the output voltages 30 and 32 using one of the output voltages 30 and 32 of the first and second sensors 4 and 6. A configuration is also possible. For example, when the film position is detected in the regions 36 and 40, the output voltage 32 is selected when the output voltage 30 exceeds the switching voltage 38, and otherwise the output voltage 30 is selected.
May be selected.

In the present embodiment, the first and second sensors 4 and 6 are provided only for the perforations 104 arranged on one side of the film 102. However, the first and second sensors 4 and 6 are also provided for the perforations 104 on the opposite side. And the second sensors 4 and 6 are likewise provided, and both perforations 1
By adding and averaging the detection results of the film position (for example, the output voltage of the sensor switching circuit 28) by the noise reduction unit 04, the noise component can be reduced, and the accuracy of the position detection can be further improved. Further, it is also possible to further provide the first and second sensors 4 and 6 for one or both of the perforations 104 and add and average the position detection results obtained by each sensor pair to further increase the SN ratio.

In this embodiment, the arrangement pitch of the first electrodes 8 constituting the first and second sensors 4 and 6 is L ×
(1 + 1/4), but this pitch is expanded to L
× (2 + ／), L × (3 + ／), etc.
Alternatively, it is also possible to make the width L / 4 by narrowing the width. As described above, since the output voltage of each sensor changes with the pitch L of the perforations 104 as a cycle, the output voltage of each sensor changes with a shift of L / 4 even when the pitch is arranged at such a pitch. The effect of can be obtained. The first and second sensors 4, 6
In the case where the pitch of the first electrodes 8 is L / 4, it is possible to avoid overlapping of the first electrodes 8 by arranging each sensor in both perforation rows.

In the present embodiment, the film position is detected by utilizing the change in capacitance. However, the film position can be detected optically. FIG. 6 is a cross-sectional side view showing the periphery of a film position detecting device using a photosensor. In this example, the first and second sensors 4 and 6 are configured by photosensors 48 and 50, respectively, and each photosensor 48 and 50 is configured by a light source 52 and a light receiving element 54. Light source 52 and light receiving element 5
4, the light emitted from the light source 52 reaches the light receiving elements 54 depending on the positional relationship with the perforations 104, and as a result, the output voltage of each light receiving element 54 becomes And the output voltages 30 and 32 of the first and second sensors 4 and 6 shown in FIG.
Therefore, also in this case, the two photo sensors 48, 5
The same effect can be obtained by switching and using the output voltage of 0.

Next, a second embodiment of the present invention will be described. FIG. 7 is a front view showing a sensor unit constituting the second embodiment, FIG. 8 is a block diagram showing a detection circuit for detecting the position of the film by a signal from the sensor unit shown in FIG. 7, and FIG. FIG. 10 is a graph showing a change in output voltage of the first to fourth sensors, and FIG. 10 is a graph showing an output voltage of a sensor switching circuit forming a detection circuit. In the drawings, the same elements as those in FIGS. 1, 2, 4, and 5 are denoted by the same reference numerals, and a detailed description thereof will be omitted here.

In the film position detecting device 56 of the second embodiment, four sensors are used, and a differential amplifying circuit and a detecting circuit are additionally provided in the detecting circuit 58 accordingly. The film position detector 56 differs from the film position detector 2 in these points.

That is, the film position detecting device 56
It further includes third and fourth sensors 60, 62 (FIG. 7), these sensors being said first and second sensors 4,
6 and the first and second electrodes 8, 1
0. However, in the third sensor 60, the first electrode 8 is constituted by the partial electrodes 14 and 64, and the partial electrode 14 is shared with the first sensor 4.
Also in the fourth sensor 62, the first electrode 8 is constituted by the partial electrodes 14 and 64, and the partial electrode 14 is shared by the third and fourth sensors 60 and 6 shared with the second sensor 6.
The partial electrodes 14 and 64 constituting the two first electrodes 8 are spaced apart from each other in the longitudinal direction of the film 102,
The length of the partial electrode 64 in the longitudinal direction of the film is set shorter than the length of the perforations 104 in the longitudinal direction of the film.

Then, the second and fourth sensors 6, 62
The arrangement pitch between each of the first electrodes 8 of the first sensor 8 and the first electrode 8 of the sensor of the immediately preceding order is almost equal to the first length.
It is set to the length which added the length of. Here, the first length is a length obtained by multiplying an arrangement pitch of the perforations 104 in the film longitudinal direction by an integer of 0 or more, and is set to 0 in the second embodiment. Also, the second
Is greater than 0 and equal to or less than 1/4 of the arrangement pitch L of the perforations 104, and is approximately L / 4 in this embodiment. That is, in the second embodiment, the first to fourth sensors 4, 6, 6
The arrangement pitch of the 0, 62 first electrodes 8 in the longitudinal direction of the film is set to approximately L / 4.

In the second embodiment, since the arrangement pitch of each first electrode 8 is L / 4,
The second sensor 6 is arranged for the perforation row opposite to the first sensor 4. The detection circuit 58
As shown in FIG. 8, the third and fourth sensors 60, 6
A resistor 16 is also provided for 2, and differential amplifier circuits 66 and 68 and detection circuits (DET) 70 and 72 are additionally provided corresponding to these sensors, respectively. Then, the sensor switching circuit 74 outputs the output voltages 30 and 32 of the first and second sensors 4 and 6 and the third and fourth
Of the output voltages 76 and 78 of the sensors 60 and 62 are selected. In FIG. 8, the locations of the resistor 16 and the oscillator 18 are simplified in order to prevent the drawing from being unnecessarily complicated.

Next, the operation of the film position detecting device 56 thus configured will be described. First and second
Similarly to the sensors 4 and 6, the third and fourth sensors 6
0, 62, partial electrodes 14, 64 of the first electrode 8
, An AC voltage is applied from an oscillator 18 through a resistor 16, so that an AC voltage corresponding to the capacitance is generated between the second electrode 10 and each of the partial electrodes 14 and 64. . The partial electrode 14 of the third sensor 60,
The voltage of 64 is input to the differential amplifier circuit 66, and the differential amplifier circuit 66 amplifies and outputs these voltage differences, while the voltages of the partial electrodes 14, 64 of the fourth sensor 62 are differentially amplified. Input to the circuit 68, the differential amplifier circuit 68 amplifies and outputs these voltage differences.

The detection circuits 70 and 72 detect and output the AC voltages output from the differential amplifier circuits 66 and 68, respectively.
As shown in FIG. 9, the third and fourth sensors 60, 6
2, the output voltages 76, 78 of the perforations 104 in the longitudinal direction of the film, similarly to the output voltages 30, 32 of the first and second sensors 4, 6.
And changes in a sine wave shape with the cycle of.

Since the arrangement pitch of the first electrodes 8 of each sensor is L / 4 as described above, when the film position changes, the first to fourth sensors 4, 6, 60,.
As shown in FIG. 9, the output voltage of 62 changes sequentially with a phase shift of L / 4. The sensor switching circuit 74
Selecting the output voltage 30, 32, 76, 78 of any one sensor according to the magnitude of the output voltage 30, 32, 76, 78 of the first to fourth sensors 4, 6, 60, 62;
It is output as a result of detecting the position of the film 102 in the longitudinal direction.

Specifically, as shown in FIG. 9, in an area 37 in which the output voltage 78 of the fourth sensor 62 is larger than the switching voltage 38, the sensor switching circuit 74 reduces the output voltage 30 of the first sensor 4 Select and output. In a region 41 where the output voltage 30 of the first sensor 4 is larger than the switching voltage 38, the sensor switching circuit 74 selects and outputs the output voltage 32 of the second sensor 6.

Further, in an area 43 where the output voltage 32 of the second sensor 6 is larger than the switching voltage 38, the sensor switching circuit 74 selects the output voltage 76 of the third sensor 60, and selects the output voltage 76 of the third sensor 60. 76 is the switching voltage 3
In the region 45 larger than 8, the sensor switching circuit 74 selects and outputs the output voltage 78 of the fourth sensor 62.

As a result, as shown in FIG. 10, the output voltage 46 of the sensor switching circuit 74 changes with respect to the change in the film position in the longitudinal direction.
Each of 1, 43 and 45 is linear and changes at a sufficient change rate. Therefore, the output voltage of the sensor switching circuit 74 is
In the entire range of the arrangement pitch L, the film 102 changes linearly and sufficiently, and by using the film position detecting device 56, the fluctuation of the projected image due to the position change in the longitudinal direction of the film 102 can be more reliably suppressed. It is possible to obtain high-quality images.

In the first embodiment, the number of sensors is small, but the center of the first electrode 8 of the first sensor 4 is located in the perforation 104 in the region 36 shown in FIG. If so, in the region 42, the center of the first electrode 8 of the first sensor 4 will now be located between two adjacent perforations 104. When the detection points are different, the voltages are inverted as described above to match the polarities. However, in an actual device, the output voltage 46 of the sensor switching circuit 28 is slightly different between the region 36 and the region 42. And may cause an error. On the other hand, in the second embodiment, although the number of sensors is increased, only the voltage output from each sensor is always used in the same detection area, so that the detection result of the film position becomes more accurate. .

In the second embodiment, the arrangement pitch of the first electrodes 8 of each sensor is substantially L / 4. However, the arrangement pitch may be further reduced. The detection accuracy can be further improved by using a region having higher linearity of the output voltage of each sensor. However, in that case, if the number of sensors used is the same, the area where the film position can be detected becomes narrow. Further, when the detectable area is set to the same range, it is necessary to increase the number of sensors.

In FIG. 9, when the position of the film 102 is, for example, near the boundary between the region 41 and the region 43, if the noise included in the sensor output voltage is large, the sensor switching circuit 74 is affected by the noise. Output voltage 46 may cause chattering. This problem can be solved by providing a hysteresis characteristic when switching the sensor output voltage in the sensor switching circuit 74. That is, for example, when monitoring the output voltage 30 of the first sensor 4, when the output voltage 30 increases, it is determined that the output voltage 30 exceeds the reference when the output voltage 30 exceeds a voltage slightly higher than the switching voltage 38. Conversely, when the output voltage 30 decreases, it is determined that the output voltage 30 has fallen below the reference when the output voltage 30 falls slightly below the switching voltage 38. In this manner, the sensor switching circuit 7
4 can prevent chattering at the output voltage 46.
Incidentally, such a method of giving the hysteresis characteristic is also effective in the case of the first embodiment.

In the second embodiment, the sensor switching circuit 74 includes the first to fourth sensors 4, 6, 6
Although the output voltage of the sensor is selected by using all of the output voltages 30, 32, 76, and 78 of 0 and 62, the same function can be realized by using only a part of the sensor output voltages. For example, when the output voltage 76 exceeds the switching voltage 38, the output voltage 30 falls below the switching voltage 34. Therefore, the output voltage 30 is used instead of the output voltage 76, and it is determined whether the output voltage 30 has fallen below the switching voltage 34. You may. Similarly, the output voltage 78 can be substituted by the output voltage 32.

In the second embodiment, the first and third sensors 4 and 60 and the second and fourth sensors 6 and 62 share the partial electrode 14, respectively. By arranging these sensors at a distance equal to or greater than the arrangement pitch of the perforations 104, it is possible to adopt a configuration in which the partial electrodes 14 are not shared.

[0047]

As described above, in the film position detecting device of the present invention, the first and second sensors are respectively
Since a signal having a magnitude corresponding to the distance in the longitudinal direction of the film between the detecting unit and the perforation closest to the detecting unit is output, the first and second sensors are used when the longitudinal position of the film changes. Of the output signal changes in a cycle corresponding to the arrangement pitch of the perforations. The arrangement pitch of the detection units of the first and second sensors is larger than 0 by a first length obtained by multiplying the arrangement pitch of the perforations in the longitudinal direction of the film by an integer of 0 or more, and is equal to 1 of the perforation arrangement pitch.
When the film position changes as described above, the first and second lengths are equal to or equal to the second length less than or equal to / 4, or approximately equal to the first length minus the second length. The output signals of the second and third sensors change in phase by a second length.

Therefore, even if the magnitude of the output signal of one sensor is close to the maximum value or the minimum value, and the change is small with respect to the change in the film position and the linearity is poor, the other sensor Is always deviated from the maximum value or the minimum value, changes sufficiently with changes in film position, and changes with good linearity.
As a result, the signal of the film position detection result output by the sensor switching means changes linearly and sufficiently over a wider range with respect to the change of the film position. By performing the optical axis correction of the projection light using the detection result of the above, it is possible to more reliably suppress the positional deviation of the projected image due to the positional change in the longitudinal direction of the film and obtain a high-quality image.

[Brief description of the drawings]

FIG. 1 is a front view showing a sensor unit constituting an example of a film position detecting device according to the present invention.

FIG. 2 is a block diagram illustrating a detection circuit that detects a position of a film based on a signal from a sensor unit illustrated in FIG.

FIG. 3 is a configuration diagram showing a telecine device incorporating the film position detecting device of the embodiment.

FIG. 4 is a graph showing how the output voltage of each sensor changes depending on the film position.

FIG. 5 is a graph showing a change in output voltage of a sensor switching circuit.

FIG. 6 is a cross-sectional side view showing a sensor periphery of a film position detection device using a photo sensor.

FIG. 7 is a front view of a film showing a sensor unit constituting the second embodiment.

8 is a block diagram illustrating a detection circuit that detects a position of a film based on a signal from a sensor unit illustrated in FIG. 7;

FIG. 9 is a graph showing changes in output voltages of first to fourth sensors.

FIG. 10 is a graph showing an output voltage of a sensor switching circuit constituting a detection circuit.

FIG. 11 is a front view showing an example of a conventional video film.

FIG. 12 is a configuration diagram illustrating an example of a conventional telecine device.

FIG. 13 is a film front view showing a periphery of a sensor used in a conventional film position detection technique.

FIG. 14 is a graph showing a change in capacitance between a detection electrode and a ground electrode.

[Explanation of symbols]

2 ... film position detecting device, 4 ... first sensor, 6
... Second sensor, 8 first electrode, 10 second electrode, 12 partial electrode, 14 partial electrode, 16
Resistor, 18 oscillator, 20 differential amplifier circuit, 22
... Differential amplifier circuit, 24 ... Detector circuit, 26 ... Detector circuit, 28 ... Sensor switching circuit, 30 ... Output voltage,
32 output voltage, 34 switching voltage, 36 area, 38 switching voltage, 40 area, 42 area, 44 area, 46 output voltage, 48 photosensor, 50 photo sensor, 52 light source, 54
... Light receiving element, 56 ... Film position detecting device, 58 ...
Detection circuit, 60: third sensor, 62: fourth sensor, 64: partial electrode, 66: differential amplifier circuit, 68:
... Differential amplifier circuit, 70 ... Detector circuit, 72 ... Detector circuit, 74 ... Sensor switching circuit, 76 ... Output voltage,
78 output voltage, 102 video film (film), 104 perforation (perforation), 10
6 ... video recording area, 108 ... telecine device, 110
... running sprocket, 112 ... running sprocket, 114 ... running system, 116 ... gate section, 118 ...
... Floodlight unit, 120... Shutter, 122.
4 ... optical axis correction / projection lens unit, 126 ... photographing unit, 1
28 position sensor 130 ground electrode 132
... detection electrodes, 134 ... partial electrodes, 136 ... partial electrodes.

Claims (6)

[Claims] An apparatus for detecting a longitudinal position of a film having a belt shape and having perforations formed at a constant pitch in the longitudinal direction when the film is fed in the longitudinal direction, comprising: a first sensor and a second sensor; And a sensor switching means, wherein the first and second sensors have their respective detection units arranged at a predetermined pitch in the longitudinal direction of the film in the vicinity of the running path of the film, and the first and second sensors are respectively And outputting a signal of a magnitude corresponding to a distance in the longitudinal direction of the film between the detection unit and the perforation closest to the detection unit, and an arrangement pitch of the detection units of the first and second sensors. Is the first length obtained by multiplying the arrangement pitch of the perforations in the longitudinal direction of the film by an integer of 0 or more;
Adding a second length greater than or equal to 1/4 of the arrangement pitch of the perforations or substantially equal to a length obtained by subtracting the second length from the first length; Selecting an output signal of one or both of the first and second sensors in accordance with a magnitude of an output signal of the sensor and outputting the result as a detection result of a position in a longitudinal direction of the film. A film position detecting device characterized by the above-mentioned. 2. The apparatus according to claim 1, further comprising a third sensor and a fourth sensor, wherein the third and fourth sensors, together with the detection units of the first and second sensors, each have a vicinity of a film traveling path. Are arranged at a predetermined pitch in the longitudinal direction of the film, and each of the third and fourth sensors has a size according to a distance in the longitudinal direction of the film between the detecting unit and the perforation closest to the detecting unit. The pitch between each of the detection units of the second to fourth sensors and the detection unit of the sensor of the immediately preceding rank is equal to the first length and the second length is equal to the second length. The sensor switching means is substantially equal to a length obtained by subtracting the second length from the first length. Output signal of the sensor, In response to the magnitude of the output signal of said third and fourth sensor or the first to fourth,
2. A film position according to claim 1, wherein an output signal of any one of said sensors is selected according to a magnitude of an output signal of said sensor, and is output as a detection result of a position in a longitudinal direction of said film. Detection device. 3. The film position detecting device according to claim 1, wherein the second length is about １ ／ of the arrangement pitch of the perforations. 4. The sensor according to claim 1, wherein the first electrode is disposed at a position where the perforation passes, and the first electrode is a detection unit. The second electrode is disposed together with the first electrode with a film interposed therebetween. The first electrode and the first electrode based on a change in the capacitance between the first and second electrodes depending on the positional relationship between the first electrode and the perforation 2. The film position detecting device according to claim 1, wherein a signal having a magnitude corresponding to a distance in a longitudinal direction of the film from the closest perforation is output. 5. A light source for emitting light toward a portion on the film where the perforations are arranged, a light receiving unit for receiving light from the light source through the film and outputting an electric signal. Including, based on the change in the amount of light received by the light receiving unit due to the positional relationship between the position where the light from the light source passes through the film and the perforation, the light source and the light receiving unit, the light source and the light receiving unit most 2. The film position detecting device according to claim 1, wherein a signal having a magnitude corresponding to a distance in a longitudinal direction of the film from the near perforation is output. 6. The film position detecting device according to claim 1, wherein the perforations are formed on both sides of the film, and each sensor is arranged separately on both sides of the film.