VOICE COIL MOTOR, AND MOVABLE MIRROR UNIT AND INTERFERENCE SPECTROPHOTOMETER EQUIPPED WITH SAME

Abstract

In the voice coil motor and the interference spectrophotometer according to the invention, the angular deviation between the movable and fixed mirrors can always be suppressed to one second or less. The voice coil motor is provided with: a static unit 71 including a yoke 73 having a cylindrical part 73a fixed to the static unit 71 and a magnet 74 disposed in the cylindrical part 73a fixed to the static unit 71; a movable unit 72 including a circular coil 72b fixed thereto, the circular coil 72b disposed between the cylindrical part 73a of the yoke 73 and the magnet 74; and a power supply line 72c for connecting the coil 72b to a power supply. The cylindrical part 73a of the yoke 73 has a slit 73c through which the power supply line 72c is to pass is created, the movable unit 72 is configured to reciprocally move relative to the static unit 71 in response to an electromagnetic force generated by the magnet 74 in conjunction with the activated coil 72b, and another slit 73d is created in the cylindrical part 73a of the yoke 73 in such a manner that the slits 73c,73d are symmetrical with respect to a central axis of the cylindrical part 73a.

Claims

1. A voice coil motor, comprising: a static unit including a yoke having a cylindrical part fixed to the static unit and a magnet disposed in the cylindrical part fixed to the static unit; a movable unit including a circular coil fixed thereto, the circular coil disposed between the cylindrical part of the yoke and the magnet; and a power supply line for connecting the coil to a power supply, wherein the cylindrical part of the yoke has a slit through which the power supply line is to pass is created, the movable unit is configured to reciprocally move relative to the static unit in response to an electromagnetic force generated by the magnet in conjunction with the activated coil, and another slit is created in the cylindrical part of the yoke in such a manner that the slits are symmetrical with respect to a central axis of the cylindrical part.

2. The voice coil motor according to claim 1, wherein the slits extend in parallel with the central axis.

3. A movable mirror unit, comprising: the voice coil motor according to claim 1; a hollow pipe having a cylindrical shape; and a piston disposed in the hollow pipe, the piston being reciprocally movable in the hollow pipe, wherein the piston includes a movable mirror fixed thereto and the movable unit are fixed to the piston.

4. An interference spectrophotometer, comprising: the movable mirror unit according to claim 3; a light source for emitting light; a fixed mirror; a beam splitter configured for the processes of splitting light received from the light source into two beams, directing one beam towards the fixed mirror and the other beam towards the movable mirror, receiving first returning light reflected from the fixed mirror and second returning light reflected from the movable mirror, combining the first and second reflecting beams of light into interference light; a light detection unit on which a sample is arranged, the detector configured to detect the interference light that has transmitted through or has been reflected from the sample; and a control unit for controlling the speed of the movable unit or the moving distance of the movable unit with the coil activated via the power supply line.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0026] FIG. 1 is a diagram showing the configuration of the essential part of the FTIR according to the present invention;

[0027] FIG. 2 is a horizontal cross-sectional diagram showing the movable mirror unit in FIG. 1;

[0028] FIGS. 3(a) and 3(b) are cross-sectional diagrams showing the VCM in FIG. 2;

[0029] FIG. 4 is a graph showing the simulation results of the difference in the magnetic flux density depending on the existence of a slit;

[0030] FIGS. 5(a) and 5(b) are graphs showing the evaluation results of the angular deviation;

[0031] FIG. 6 is a diagram showing the configuration of the essential part of a conventional FTIR; and

[0032] FIG. 7 is a horizontal cross-sectional diagram showing the movable mirror unit in FIG. 6.

DETAILED DESCRIPTION OF EMBODIMENTS

[0033] In the following, the embodiments of the present invention are described in reference to the drawings. Here, the present invention is not limited to the below-described embodiments, and various types of modifications are included as long as the gist of the present invention is not deviated from.

[0034] An FTIR is cited as an example of the interference spectrophotometer according to the present invention, and FIG. 1 shows the configuration of the essential part thereof. FIG. 2 is a horizontal cross-sectional diagram showing the movable mirror unit 50 in FIG. 1. In addition, FIGS. 3(a) and 3(b) are cross-sectional diagrams showing the VCM 70 in FIG. 2, where FIG. 3(a) is a longitudinal cross-sectional diagram and FIG. 3(b) is a horizontal cross-sectional diagram. Here, the same symbols are attached to the same components as in the above-described FTIR 101, and thus, the descriptions thereof are not repeated.

[0035] An FTIR 1 is provided with a main interferometer essential part 40, a light source 10 for emitting infrared rays, a light detection unit 20 for detecting an interferogram, and a computer (control unit) 30.

[0036] The main interferometer essential part 40 is provided with a housing 41, a beam splitter 42, a movable mirror unit 50 having a movable mirror 53, and a fixed mirror unit 60 having a fixed mirror 61 and an alignment mechanism 62.

[0037] The movable mirror unit 50 is provided with a hollow pipe in cylindrical shape having the center in the forward and backward direction (X direction), a piston 52 in columnar form that is disposed within the hollow pipe 51 so that reciprocal movement is possible in the forward and backward direction, a movable mirror 53 fixed to the front portion of the piston 52, and a VCM 70.

[0038] The VCM 70 is provided with a static unit 71 and a movable unit 72.

[0039] The static unit 71 is provided with: a yoke 73 made of iron (magnetic material) having a cylindrical part 73a with the central axis being in the forward and backward direction and a rear sidewall in disc form; two magnets 74 (74a, 74b) in columnar form having a central axis in the forward and backward direction; and a pole piece 75 in columnar form having a central axis in the forward and backward direction. The first magnet 74a, the pole piece 75 and the second magnet 74b are fixed to the center portion on the front surface of the rear sidewall 73b of the yoke 73 in this order, and thus are disposed within the cylindrical part 73a of the yoke 73. In addition, the front portion of the cylindrical part 73a is attached to the rear portion of the housing 41 (hollow pipe 51).

[0040] A first slit 73c is created in the right sidewall of the cylindrical part 73a of the yoke 73 so as to extend in the forward and backward direction, and at the same time, a second slit 73d is created in the left sidewall of the cylindrical part 73a of the yoke 73 so as to extend in the forward and backward direction. That is to say, the first slit 73c and the second slit 73d are created in such locations that the slits are point symmetrical relative to the central axis (X direction) of the cylindrical part 73a of the yoke 73.

[0041] The movable unit 72 is provided with a bobbin 72a in cylindrical shape having a central axis in the forward and backward direction, and a circular coil 72b wound around the outer peripheral surface of the rear portion of the bobbin 72a. In addition, the front portion of the bobbin 72a is attached to the rear portion of the piston 52. Furthermore, the coil 72b is disposed between the cylindrical part 73a of the yoke 73 and the pole piece 75, and is electrically connected to the power supply (not shown) via a power supply terminal (power supply line) 72c that is disposed so as to pass through the first slit 73c in the upward and downward directions (Y direction). Moreover, a dummy power supply terminal 72d having the same shape as the power supply terminal 72c that is disposed so as to pass through the second slit 73d in the Y direction is formed in the movable unit 72. That is to say, the power supply terminal 72c and the dummy power supply terminal 72d are formed in such locations that the terminals are point symmetrical relative to the central axis (X direction) of the cylindrical part 73a of the yoke 73.

[0042] As a result, the coil 72b receives an electromagnetic force (Lorentz force) due to the magnetic field generated between the yoke 73 and the pole piece 75 so as to move in the forward and backward direction when a current is made to flow through the coil 72b via the power supply terminal 72c, and thus, the moving mirror 53 that is fixed to the piston 52 also moves in the forward and backward direction. At this time, a magnetic flux density as on the there is a slit side in FIG. 4 is generated on both sides, left and right sidewall sides, of the cylindrical part 73a of the yoke 73.

[0043] The computer 30 is provided with a CPU 31 and an input device 32. The CPU 31 can be divided into the following parts using the functions processed by them. The CPU 31 has: a light intensity information acquisition part 31a for acquiring an interferogram from the light detection unit 20; a sample measurement part 31b for calculating the absorbance spectrum and the like of the sample S; a movable mirror control part 31c for controlling the speed or the moved distance of the movable mirror in the movable mirror unit 50 on the basis of the input information that has been inputted through the input device 32; and a fixed mirror control part 31b for controlling the alignment mechanism 62 in the fixed mirror unit 60.

[0044] As described above, in the FTIR 1 according to the present invention, the first slit 73c and the second slit 73d are provided in such locations that the slits are symmetrical relative to the central axis of the yoke 73, and therefore, the difference in the impellent is cancelled so as to prevent a momentum that might cause a rotary motion from being generated. Thus, the angular deviation between the movable mirror 53 and the fixed mirror 61 when driven at a high speed can be suppressed to one second or less (see FIG. 5(a)).

Other Embodiments

[0045] (1) Though the above-described FTIR 1 has a configuration that is provided with a dummy power supply terminal 72d, such a configuration is also possible where a coil is electrically connected to the power supply via the power supply terminal, and at the same time is electrically connected to the power supply via a dummy power supply terminal.

[0046] (2) Though the above-described FTIR 1 has a configuration that is provided with a dummy power supply terminal 72d, such a configuration is also possible where no dummy power supply terminal is provided.

INDUSTRIAL APPLICABILITY

[0047] The present invention can be preferably applied to interference spectrophotometers such as a Fourier transform infrared spectrophotometer.

REFERENCE SIGNS LIST

[0048] 1 FTIR (interference spectrophotometer)

[0049] 70 VCM (voice coil motor)

[0050] 71 static unit

[0051] 72 movable unit

[0052] 72b coil

[0053] 72c power supply terminal (power supply line)

[0054] 73 yoke

[0055] 73a cylindrical part

[0056] 73c, 73d slit

[0057] 74 magnet