JPH11281888A - Optical device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain high-contrast and high-resolution image quality by making the refractive index arrangement of a 1st positive lens and a 2nd negative lens and that of a 3rd negative lens and a 4th positive lens almost symmetric and making the refractive indexes of the 1st lens and the 4th lens and those of the 2nd lens and the 3rd lens almost equal. SOLUTION: The refractive index arrangement of the 1st and the 2nd lenses L1 and L2 and that of the 3rd and the 4th lenses L3 and L4 are made almost symmetric and the refractive indexes of the 1st and the 4th lenses L1 and L4 and those of the 2nd and the 3rd lenses L2 and L3 are made almost equal so as to satisfy expressions I to III. In the expression I to III, (f12 ) is the synthetic focal distance of the lenses L1 and L2, (f34 ) is the synthetic focal distance of the lenses L3 and L4, Nd14 is the refractive index of the lenses L1 and L4 in the case of the wavelength light of 587.6 nm and Nd23 is the refractive index of the lenses L2 and L3 in the case of the wavelength light of 587.6 nm.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[Table of Contents] The present invention will be described in the following order.

BACKGROUND OF THE INVENTION Problems to be Solved by the Invention Means for Solving the Problems Embodiments of the Invention (FIGS. 1 to 11) Effects of the Invention

[0003]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an optical device, and is suitably applied to, for example, an optical device for reading digital data recorded on a movie film.

[0004]

2. Description of the Related Art Conventionally, as a projector used in a movie theater, there is a projector which uses a movie film in which an image and a sound are recorded on the same film and reproduces the image and the sound corresponding to the image at the same time. In this movie film, each frame image obtained by frame-taking a series of moving images is sequentially recorded in the longitudinal direction, and a digital audio track is formed in the longitudinal direction of the movie film.

In this digital audio track, digital audio information is recorded in a binary pattern of black and white. Therefore, when playing back video and audio recorded on the movie film using a projector, each frame image is irradiated with a predetermined light source to project the projected image of each frame image onto a screen. The digital audio track is irradiated with light for audio reproduction, and an image of the digital audio track is formed on an image pickup device (CCD) via a predetermined lens system. Thus, by converting the digital audio track pattern into an electric signal in the image pickup device, this is reproduced as audio data.

[0006]

A lens system for imaging a pattern formed on such a digital audio track on an image sensor generally uses a lens for a camera as a prototype. This camera lens is
Since the image quality (contrast, resolution, etc.) when focusing on an object at infinity needs to be sufficiently high for practical use, the image quality when focusing on an object at a close distance is practical. Not enough on.

As one method for solving such a problem, complicated movements such as increasing the number of lens elements and changing the distance between lens groups in accordance with the object distance to be focused. It has been considered that by performing the control, a sufficient image quality can be obtained in both the case where the focus is adjusted to a subject at a close distance and the case where the focus is adjusted to an object at infinity.

However, in such a lens system, the number of lenses is large, and it is necessary to provide a complicated control system for controlling the movement of the lens, so that there is a problem that the configuration is inevitably complicated.

The present invention has been made in view of the above points, and has as its object to propose an optical device which can obtain high image quality with a simple configuration.

[0010]

According to the present invention, there is provided a liquid crystal display having a first positive refractive index in order from the object side.
A second lens having a negative refractive index, a third lens having a negative refractive index made of the same material as the second lens, and a first lens having a negative refractive index.
And a fourth lens having a positive refractive index made of the same material as the first lens. The refractive index arrangement of the first lens and the second lens and the refractive index arrangement of the third lens and the fourth lens are different from each other. Obtaining high-contrast and high-resolution image quality by making them substantially symmetric and making the refractive indices of the first and fourth lenses substantially equal to the refractive indices of the second and third lenses. Can be.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

In FIG. 1, a projection system 50 winds a movie film 1 wound around a supply reel 11 on a take-up reel 14 via a digital audio reproducing unit 51 and a projector 13. in this case,
The running of the movie film 1 is controlled at a predetermined speed in accordance with the rotation of a sprocket 13A for film feeding provided in the projector 13 by a predetermined motor.

At this time, the projector 13 is formed on the movie film 1 by intermittently feeding the movie film 1 in the film intermittent feeding section 13B and irradiating the light source light from the light source section 13C to the frame image of the movie film 1. Each frame image is projected onto the screen 31 sequentially and continuously.

As shown in FIG. 2, the digital sound reproducing device 51 receives the movie film 1 by a stabilizer (guide roller) 82 via a guide roller 81. The guide roller 81 is provided on a front surface of a base cabinet 150 (hereinafter, referred to as a base surface portion) constituting a main body of the digital audio reproducing device 51 so that a winding angle of the movie film 1 around the stabilizer 82 falls within a predetermined range. ) 1
It is arranged at a predetermined position of 50A.

The stabilizer 82 is pivotally connected to the base surface 150A of the base cabinet 150 by a pivot shaft 82C.
The roller 82A is pivotally supported at the tip of a rotating arm 82B rotatably supported, and the rotating arm 82B has a biasing force at a predetermined rotating position by a spring (not shown). By applying a predetermined tension to the movie film 1, the running of the movie film 1 can be stabilized.

The cinema film 1 supplied through the stabilizer 82 is engaged with the sprocket 60. The sprocket 60 is rotatably supported on a fixed shaft 55 fixed to the base surface portion 150A so as to be rotatable about a center of rotation. A frequency generating cylinder 75A that is a part of the device unit 75 is provided,
It rotates integrally with the sprocket 60 about the fixed shaft 55 as the center of rotation.

At a predetermined position of the base surface portion 150A,
Rollers 83 and 84 are provided at a position close to the sprocket 60 so that the movie film 1 can be securely engaged with the sprocket 60.

A brake device is built in the sprocket 60, and a predetermined tension is applied to the moving movie film 1 by a sprocket 13A (FIG. 1) for feeding the film of the projector 13.

Further, the movie film 1 supplied via the sprocket 60 is moved by the position regulating guide portion 200 provided following the sprocket 60 to form the base film portion 1.
The height from 50A is adjusted.

Movie film 1 whose distance from base surface portion 150A is regulated by position regulating guide portion 200.
Is wound around the flywheel 65 of the optical reading unit 70 at a predetermined winding angle. The winding angle is set by the position where the position regulating guide portion 200 and the guide roller 86 are disposed.

The flywheel 65 has a base surface 150.
A is rotatably supported by a predetermined rotation shaft (not shown) on A, and rotates with the running of the movie film 1 wound around the flywheel 65. In the vicinity of the flywheel 65, a light emitting section 71 and a light receiving section 72 constituting the optical reading section 70 are provided so as to maintain a predetermined positional relationship sandwiching the movie film 1.

In the optical reading section 70, when a frequency signal is output from the frequency generating section as the frequency generating section integrated with the sprocket 60 rotates, the light emitting section 71 is turned on at a timing based on the frequency signal. Light emission operation is performed.

That is, as shown in FIG. 3, a rotation detection signal SFG output from the frequency generator 75 in accordance with the rotation of the sprocket 60 (FIG. 2) is output from the light emitting section 71 of the optical reading section 70 to the timing generator 90. Supplied to

The timing generator 90 binarizes the supplied rotation detection signal SFG into a logic "H" level and a logic "L" level based on a predetermined threshold value. In this way, the pulse signal SPL in which the logic “H” level and the logic “L” level alternately appear in accordance with the frequency of the rotation detection signal SFG is supplied from the timing generator 90 to the light emission control unit 91.

The light emission control section 91 controls the lighting of the LEDs 35A and 35B based on the supplied pulse signal SPL, thereby controlling the timing at which the LEDs 35A and 35B are turned on by the rotation of the frequency generating section 75 (that is, the rotation of the sprocket 60). Rotation).

As a result, light LA and LB composed of far infrared rays are emitted from the LEDs 35A and 35B in synchronism with the running speed of the movie film 1, respectively, and are leveled through the corresponding light diffusion plates 36A and 36B. After that, the digital audio tracks 6A and 6B recorded along both side edges of the movie film 1 are irradiated.

That is, as shown in FIG. 4, the movie film 1 has a frame image 4 obtained by frame-taking a series of moving images.
Are sequentially recorded in the longitudinal direction, and film feed holes (hereinafter, referred to as perforations) 2 are sequentially formed along both side edges of the movie film 1 so as to sandwich each frame image 4. I have.

Here, digital audio tracks 6A and 6B are formed on the movie film 1 along both side edges of the movie film 1 outside each of the perforation rows 3A and 3B, and the digital audio tracks are formed. 6A and 6B respectively have digital audio information in black as shown in FIG. 5 (portion where the film is exposed).
And a binary pattern of white (a part where the film is not exposed) is sequentially recorded in a reading scanning direction a substantially perpendicular to the running direction of the movie film 1. In each of the digital audio tracks 6A and 6B, four channels of digital audio information are recorded in units of predetermined data blocks.

Accordingly, in FIG. 3, the transmitted light LA1 and LB1 transmitted through the movie film 1 are transmitted to corresponding lines of a CCD (Charge Coupled Device) configuration via lens units 37A and 37B, which are optical devices of the light receiving unit 72, respectively. Digital audio track 6 on sensors 38A and 38B
A and 6B are formed as digital pattern images.

The line sensors 38A and 38B scan the sequentially irradiated digital pattern images (LA1 and LB1) line by line in the width direction of the movie film 1, and obtain the digital pattern images based on the line-by-line digital pattern images. The detected signal voltages are respectively used as detection signals S1A and S1B.
To the following decoder 39.

At this time, since the digital pattern images are sequentially incident on the line sensors 38A and 38B in synchronization with the running speed of the movie film 1, the line sensors 38A and 38B
And 38B can accurately scan the digital pattern image line by line at a timing synchronized with the running speed of the movie film 1. Thus, for example, even when the running speed of the movie film 1 is reduced, the operation of scanning the once-scanned line repeatedly can be avoided.

The decoder 39 supplies the detection signal S1
The digital audio information recorded on each of the digital audio tracks 6A and 6B of the movie film 1 is sequentially reproduced based on A and S1B, respectively, and the digital audio information is corresponded via the amplifier 28 as a digital audio reproduction signal S2 for a plurality of channels. To a plurality of speakers 29 to be used. Thus, the plurality of loudspeakers 29 can each transmit sound based on the digital reproduction signal S2 corresponding to each channel.

As described above, the projection apparatus 50 reproduces the audio information of the digital audio tracks 6A and 6B of the movie film 1 in the digital audio reproduction unit 51 and the movie film 1 in the projector 13 (FIG. 1).
Are successively projected onto the screen 31 via the projection lens 30 to reproduce a series of moving images composed of the frame images 4 as the movie film 1 travels.

Here, the lens portions 37A and 37B provided as the optical device have the same configuration, and the first lens portion 37A has a biconvex positive refractive index as shown in FIG. A first lens L1, a second lens L2 having a negative meniscus refractive index, a third lens L3 having a negative meniscus refractive index, and a fourth lens having a biconvex positive refractive index L4, each lens is fixed to the lens barrel at a predetermined interval.

The first lens L1 and the fourth lens L4 are made of the same material (optical glass) and have the same refractive index. The second lens L2 and the third lens L3 are made of the same material (optical glass) and have the same refractive index.

The four lenses L1, L2, L3 and L
The lens unit 37A made of 4 is represented by the following equation:

[0037]

(Equation 4)

And the following equation:

[0039]

(Equation 5)

And the following equation:

[0041]

(Equation 6)

Satisfies the condition expressed by
However, representative of f ₁₂ is the composite focal length of the first lens represents L1 and the composite focal length of the second lens L2, f ₃₄ the third lens L3 and fourth lens L4 in (1).
In equation (2), N _d14 is 587.6 for each of the first lens L1 and the fourth lens L4 made of the same material.
_Nd23 represents a second lens L2 and a third lens L3 made of the same material.
Represents the refractive index for light having a wavelength of 587.6 [nm].

Here, the condition expressed by the equation (1) is that the combined focal length f of the first and second lenses L1 and L2 arranged in the first half of the four lenses L1 to L4.
₁₂ and the third and fourth lenses L3 arranged in the latter half
And a composite focal length greater than the ratio of 0.7 between f ₃₄ 1 of L4.
A range smaller than 2 indicates that the refractive index arrangement can be set so as to obtain a practically sufficient image quality for the entire lens unit 37A, and that mainly spherical aberration can be favorably corrected.

By satisfying the conditions represented by the equations (2) and (3), the Petzval sum (Petzval sum) is satisfied.
sum) to reduce the field curvature,
By increasing the refractive index of L4, spherical aberration can be favorably corrected.

Here, as shown in FIG. 7 in which parts corresponding to those in FIG. 6 are denoted by the same reference numerals, four lenses L1, L2,
In the lens section 37A constituted by L3 and L4, the film-side entrance surface of the first lens L1 is I1, the CCD-side exit surface of the first lens L1 is I2, and the film side of the second lens L1 is I2. The incident surface of I3, the second lens L2
The light exit surface of the third lens L3 on the film side is I5, the light exit surface of the third lens L3 on the CCD side is I6, and the light incident surface of the fourth lens L4 on the film side is I7. The exit surface on the CCD side of the fourth lens L4 is I8, the radii of curvature of the entrance surface and the exit surfaces (I1 to I8) are r1 to r8, the thickness of the center of the first lens L1 is d1, and The surface distance at the center between the first lens L1 and the second lens L2 is d2, the thickness at the center of the second lens L2 is d3, and the distance between the center of the second lens L2 and the third lens L3 is d3. The surface distance is d4, and the thickness of the central portion of the third lens L3 is d.
5, the distance between the centers of the third lens L3 and the fourth lens L4 is d6, and the thickness of the center of the fourth lens L4 is d7.
And the d-line (wavelength: 58) of the first to fourth lenses L1 to L4
The refractive index at 7.6 [nm]) is n1 to n4, and the Abbe numbers at the d-line (wavelength: 587.6 [nnm]) of the first to fourth lenses L1 to L4 are ν1 to ν4.

FIG. 8 shows specific numerical examples of the lens portion 37A satisfying the expressions (1) to (3). In FIG. 8, the units of the curvature radii r1 to r8 and the thickness (or interval) d1 to d7 of each lens are [mm], and the film direction is positive. The distance from the film surface to the entrance surface I1 of the first lens L1 is 20.69 [mm], and the lens portion 37A
Has an open F-number (F number) of 2.5, and the lens portion 37A
Has a lateral magnification of 1.354.

FIG. 9 shows aberration curves on the light receiving surface of the line sensor (CCD) 38A of the light beam passing through the lens section 37A. That is, FIG. 9A shows a line sensor (C
The spherical aberration at each height position of the image formed on the CD) 38A is calculated using three wavelength lights (λ1 = 643 [nm], λ2 = 633 [nm],
λ3 = 653 [nm]). FIG. 9B shows the astigmatism of the sagittal S and the meridional T measured at each height position of the image formed on the line sensor (CCD) 38A. FIG. 9 (C)
Is a measurement of distortion at each height position of the image formed on the line sensor (CCD) 38A. This figure 9
As shown in (1), in the lens system 37A, various aberrations are favorably corrected. Incidentally, in FIG. 9, 2ω represents the angle of view.

The second lens portion 37B (FIG. 3)
It has a configuration similar to that of the first lens unit 37A, whereby various aberrations are also favorably corrected in the second lens unit 37B.

In the above configuration, the lens unit 37A (and 37B) has a magnification of 1.354 times, and has a magnification close to 1: 1. As described above, in the close-up lens unit 37A (and 37B) that is close to (or equal to) the same magnification, of the four lenses L1 to L4 constituting the lens unit 37A (and 37B), the incident side (film) a composite focal length f ₁₂ of the two lenses side) L1 and L2, the ratio of the composite focal length f ₃₄ of the two lenses L3 and L4 on the output side (line sensor side) (1) as shown in equation 0.7 The lens L1 and L2 in the first half (incident side) of the lenses L1 to L4 constituting the lens unit 37A
And the refractive index arrangement of the lenses L3 and L4 in the latter half (outgoing side) is substantially symmetric. Thereby, the lens unit 37A (and 3)
7B) is suppressed.

Further, of the four lenses L1 to L4 constituting the lens portion 37A (and 37B), the first lens L
The first and fourth lenses L4 are formed of lenses of the same material, the second lens L2 and the third lens L3 are formed of lenses of the same material, and the first lens L1 and the fourth lens L4 are refracted. Rate N _d14 , the second lens L2 and the third
By reducing the difference from the refractive index N _d23 of the lens L3 to the Petzval sum as shown in the equation (2), the field curvature can be suppressed.

Incidentally, the range (0.7 to 1.2) of the ratio of the combined focal length in the equation (1) and the limit value (3.0) in the equation (2).
And the minimum value (1.8) of the refractive index N _{d23 in} the equation (3) is
As shown in FIGS. 9A and 9B, these are values that can favorably suppress various aberrations in the experimental results.

Thus, when the lens portion 37A (and 37B) is used in the close-up area where the imaging magnification is about 1/4 to 2 times, the image quality can be made high in contrast and high in resolution.

According to the above configuration, the first to fourth lenses L1 to L4 constituting the lens section 37A (and 37B).
The lens L1 and the fourth lens L4 are made of lenses of the same material so that they have the same refractive index N _d14, and the second lens L2 and the third lens L3 are made of lenses of the same material. By setting the respective refractive indices to the same refractive index N _d23 and further satisfying the above-mentioned expressions (1) to (3), various aberrations of the lens portions 37A (and 37B) can be suppressed with a small number of lenses. it can.

Thus, by using the lens portions 37A and 37B, the pits recorded on the film 1 can be coupled to the line sensor (CCD) 38A (and 38B) with high quality. The reading accuracy of digital audio data can be improved.

In the above embodiment, the case where the lenses 37A and 37B having the characteristics shown in FIGS. 8 and 9 are used has been described. However, the present invention is not limited to this, and the expressions (1) to (3) are used. And the first lens L1 and the fourth lens L1
If the material of the lens L4 is the same and the materials of the second lens L2 and the third lens L3 are the same, a lens having other characteristics may be used.

FIG. 10, for example, in which parts corresponding to those in FIG. 8 are denoted by the same reference numerals, shows another embodiment of the lens portion 37A (and 37B), and the incident surface I1 of the first lens L1 from the film surface. The distance to the lens unit is 20.69 [mm].
The open F value (F number) of 7A is 2.5,
The lateral magnification of 7A is 1.145.

FIG. 11 is a graph showing aberration curves on the light receiving surface of the line sensor (CCD) 38A of the light beam passing through the lens section 37A. That is, FIG. 11A shows that the spherical aberration with respect to each height position of the image formed on the line sensor (CCD) 38A is converted into three wavelength lights (λ1 = 643 [nm] and λ2 = 633 [n].
m], λ3 = 653 [nm]).
FIG. 11B shows the astigmatism of the sagittal S and the meridional T measured at each height position of the image formed on the line sensor (CCD) 38A. FIG. 11 (C) shows the measurement of the distortion at each height position of the image formed on the line sensor (CCD) 38A. As shown in FIG. 11, various aberrations are favorably corrected also in the lens system 37A according to another embodiment.

In the above embodiment, the case where the lenses L1 to L4 made of optical glass are used has been described. However, the present invention is not limited to this, and lenses of other materials such as optical plastics may be used. In this case,
A material for forming the first and fourth lenses L1 and L4,
A material different from the material forming the second and third lenses L2 and L3 may be used.

Further, in the above-described embodiment, the case where a lens magnification of 1.354 times or 1.145 times is used has been described. However, the present invention is not limited to this. Can be.

Further, in the above-described embodiment, the case where the present invention is applied to the optical device for reading the digital audio data recorded on the film 1 has been described, but the present invention is not limited to this. The present invention can also be applied to an optical device that writes digital audio data.

In the above-described embodiment, the lens units 37A and 37B constituted by the four lenses L1 to L4 have been described. However, the present invention is not limited to this. May be applied. In this case, for a plurality of lenses, the ratio between the combined focal length of the lens group on the incident side and the combined focal length of the lens group on the exit side is (1).
The same effect as in the above case can be obtained by configuring so as to satisfy the expression and by setting the refractive index arrangement so as to reduce the Petzval sum as described in the expression (2). In this case, for example, in an eight-lens configuration, the first and second lenses and the seventh and eighth lenses are formed of the same material, respectively, counted from the incident side (film side), and the third and fourth lenses are formed. , The fifth lens and the sixth lens may be formed of the same material.

In the above embodiment, the case where the present invention is applied to the optical device of the device for reproducing digital audio data has been described, but the present invention is not limited to this.
For example, the present invention is suitably applied to an optical device that performs close-up photography of various other devices such as a barcode reader.

[0063]

As described above, according to the present invention, the first lens having a positive refractive index and the second lens having a negative refractive index are arranged in order from the object side.
, A third lens having a negative refractive index made of the same material as the second lens, and a fourth lens having a positive refractive index made of the same material as the first lens. Lens and second
The refractive index arrangement of the third lens and the refractive index arrangement of the third lens and the fourth lens are made substantially symmetric, and the refractive index arrangement of the first lens and the fourth lens and the second lens and the third lens By making the refractive indices substantially equal to each other, it is possible to realize an optical device capable of obtaining high contrast and high resolution image quality.

[Brief description of the drawings]

FIG. 1 is a schematic side view showing a projection system having an optical device according to the present invention.

FIG. 2 is a perspective view showing a configuration of a sound reproducing device using the optical device according to the present invention.

FIG. 3 is a schematic diagram illustrating a configuration of an optical reading unit of the audio reproducing device.

FIG. 4 is a plan view showing the configuration of the movie film.

FIG. 5 is a schematic diagram showing a digital audio track formed on a movie film.

FIG. 6 is a schematic side view showing a lens configuration of the optical device according to the present invention.

FIG. 7 is a schematic side view showing a lens configuration of the optical device according to the present invention.

FIG. 8 is a schematic diagram illustrating the configuration and characteristics of each lens.

FIG. 9 is a characteristic curve diagram showing characteristics of the lens system.

FIG. 10 is a schematic diagram illustrating a configuration and characteristics of each lens according to another embodiment.

FIG. 11 is a characteristic curve diagram showing characteristics of a lens system according to another embodiment.

[Explanation of symbols]

1 ... Film film, 6A, 6B ... Digital audio track, 11 ... Supply reel, 14 ... Take-up reel, 2
8 ... Amplifier, 29 ... Speaker, 35A, 35B ...
LED, 36A, 36B ... light diffusion plate, 37A, 37B
…… Optical device, 38A, 38B …… Line sensor (CC
D), 39: decoder, 50: projection system, 51
…… Digidak audio playback device, 60 …… Sprocket,
70 optical reading unit, 71 issuing unit, 72 light receiving unit, L1, L2, L3, L4 lens.

Claims (3)

[Claims] 1. A first lens having a positive refractive index, a second lens having a negative refractive index, and a third lens having a negative refractive index and made of the same material as the second lens from the object side. And a fourth lens having the same material as the first lens and having a positive refractive index. The refractive index arrangement of the first lens and the second lens, and the third lens and the fourth lens. The refractive index arrangement of the lenses is made substantially symmetric, and the refractive indexes of the first lens and the fourth lens are substantially equal to the refractive indexes of the second lens and the third lens. An optical device, characterized in that: 2. The optical device according to claim 1, wherein: (Equation 2) (Equation 3) The optical device according to claim 1, wherein the optical device is formed so as to satisfy the following. However, f ₁₂ is ,, f ₃₄ represents a composite focal length of the first lens and the second lens represents a composite focal length of the third lens and the fourth lens, N _d14 is the first N _d23 represents the refractive index of the first lens and the fourth lens in the light having a wavelength of 587.6 [nm].
Is 587.6 [nm] of the second lens and the third lens.
Represents the refractive index at the wavelength of light. 3. The optical device according to claim 1, wherein said optical device forms an image of digital audio data recorded on a movie film on an imaging surface of a predetermined image sensor.