JPH11201817A - Method and device for driving optical filter wheel - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an optical filter wheel driving device in which fitting of an encoder wheel is easy, no displacement takes place from extrinsic factor, and an initial position is easily assured even after displacement. SOLUTION: Related to a disc-like optical filter wheel 2, a plurality of narrow band filter 4 are provided around a wheel 3. Provided with a step motor 5 as a driving part, the optical filter wheel 2 is so provided that its center is freely rotated by a drive shaft 6 of the step motor 5. Further, an encoder wheel 9 comprising a slit part 8 is provided at a drive shaft 7 of the step motor 5. At a circumferential side part of an encoder wheel 8, a detection part 10 provided with a photo-sensor for detecting the slit part 8 is provided. Driving/ controlling of the optical filter wheel 2 is performed by a control device 17, and the control device 17 comprises a control part is and a drive control part 19, further, comprises a storage part 20 where the signal pattern or the drive signal which the drive control part 19 outputs for driving/controlling the step motor 5 is stored.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spectrometer for measuring a component of an object by irradiating the object with light of a specific wavelength and detecting the transmitted or reflected light. The present invention relates to a driving method of an optical filter wheel for switching a plurality of narrow band filters provided between a light source and a device under test in order to irradiate light of a specific wavelength, and a driving apparatus therefor.

[0002]

2. Description of the Related Art The prior art of an optical filter wheel driving device 50 will be described with reference to FIGS. As shown in FIG. 4, an optical filter wheel 51 generally has a plurality of narrow band filters 53 provided around a wheel 52, and is provided on a drive shaft 55 of a step motor 54. I have. Further, an encoder wheel 57 is provided on a drive shaft 56 of the step motor 54, and the optical filter wheel 51 and the encoder wheel 57 are simultaneously driven to rotate in the same direction. A light source 58 is arranged on one side of the narrow-band filter 53a, and a measurement cell 59 filled with an object to be measured is arranged on the other side, and a light receiving element 60 is arranged at a position where the measurement cell 59 is transmitted.

A control device 61 for controlling the rotation of the optical filter wheel 51 includes a drive control section 62 of the control device 61.
Outputs a drive signal to the step motor 54. Further, the photo sensor detecting section 63 detects a slit section 64 (FIG. 4) provided on the circumference of the encoder wheel 57 and sets the slit section 64 (FIG. 4) as the origin position of the control for driving the optical filter wheel 51 to rotate.

In the above-described configuration, first, the control device 61 causes the drive control unit 62 to output a drive signal to the step motor 54 until the photo sensor detection unit 63 detects the slit unit 64. By detecting the slit portion 64, drive control is performed such that the position from the origin position is controlled by setting the position of the slit portion 64 as the origin and setting the position of each of the plurality of narrow band filters 53 at a predetermined angle. By outputting a drive signal from the section 62 to the step motor 54, the target narrow band filter 53 a among the plurality of narrow band filters 53 becomes the light source 58 and the measuring cell 59.
It is arranged at the position connecting.

As described above, in the method of detecting the slit portion 64 and setting it as the origin position, a change in shape due to thermal expansion of the encoder wheel 57 is easily predicted. Further, when the driving unit is constituted by the step motor 54, the angle of one step is often less than 1 degree. In addition, the mounting of the encoder wheel 57 having the slit portion 64 is often performed manually, and the mounting position of each device is slightly different. The failures caused by these will be described below.

As shown in FIG. 6 (A) or (B), the position of the slit portion 64 with respect to the photo sensor detecting portion 63 is slightly shifted due to a slight shift of the mounting. FIG.
As shown in FIG. 3A, the drive signal P1 sequentially moves from the drive signal P1 to P2. That is, the position moved by the drive signal of P2 is set as the origin position.

As shown in FIG. 6B, the slit portion 64 is similarly detected at the step position of the signal P2. In this case, the following inconvenience may occur. That is, when a change in shape due to thermal expansion of the encoder wheel 57 occurs, it is considered that the change occurs as a shift in the rotational direction, as shown in FIG. 6C or 6D. In the case of displacement as shown in FIG. 6 (D), there is no hindrance because the slit portion 64 is detected in step P2 and P2 in the same manner, but in the case of displacement as shown in FIG. 6 (C). , P0 has already been detected when stepping from the position P0 to the position P1, and the position moved by outputting the drive signal P1 becomes the origin position.

The change in the origin position due to an external factor such as thermal expansion involves a subtle change in the position of the narrow band filter, and is a cause of a detection error for a detection device that must constantly perform stable light irradiation. It will be. The narrow band filter has a wavelength that slightly shifts depending on the light passing position of the filter. If these shifts occur during the measurement, that is, if the origin position slightly shifts due to thermal expansion, 1 There is a possibility that a step shift may occur, and even if the filter is not switched to the adjacent narrow band filter, the wavelength of the light applied to the device under test is stable because the light passing position is significantly different even in the same narrow band filter. It cannot be said that it was done. This also affects the measurement accuracy of the device itself, and causes variations in the product as a whole.

In order to prevent these problems from occurring, FIG.
By assembling to all the devices so that the position is as shown in (A), it is possible to cope with a slight change due to external factors, but fine adjustments are made by hand against parts whose one step angle is less than 1 degree. It is impossible to do it by work. Although it is possible to manufacture with high accuracy by an expensive manufacturing process, it is not preferable.

[0010]

As described above, the encoder wheel can be easily mounted without increasing the manufacturing cost, and the origin position is not shifted by an external factor. It is another object of the present invention to provide a method and an apparatus for driving an optical filter wheel in which an origin position can be easily secured.

[0011]

According to the present invention, there is provided an optical filter wheel provided with a plurality of narrow band filters for passing light of a specific wavelength out of light emitted from a light source. The above problem is solved by a method of driving an optical filter wheel in which a wavelength of light to irradiate an object to be measured is switched by switching a plurality of narrow band filters with respect to a light source by rotating the wheel by driving means. For this purpose, a slit provided in an encoder wheel that rotates in the same manner as the optical filter wheel at the initial stage, and a drive signal instructed by a drive unit when the slit is detected are stored and used. In the switching setting of the optical filter wheel, the position of the optical filter wheel is determined by the slit and the drive signal pattern corresponding to the slit. Irutahoi - was driving method Le.

Since the driving signal patterns corresponding to the slits are stored at the initial stage, the position can be determined by using both the slits and the driving signal patterns at the time of use. First, as one method, an optical filter wheel using only a slit is used.
It is possible to control the driving of the disk, but it is possible to check by confirming the signal pattern of the driving signal corresponding to the slit each time. As still another method, if the rough position is determined by the slit and a drive signal based on the drive signal pattern stored corresponding to the slit is issued, the correct position of the optical filter wheel is always determined. Becomes possible.

According to the second aspect, the driving signal when the detecting section detects the slit during use and the stored driving signal are compared, and if different, the stored driving signal is issued to set the optical system at a fixed position. The driving method of the filter wheel was adopted.
As a result, if the driving signal patterns for the slits are different, a correct driving signal corresponding to the slits can be generated, so that a change due to an external factor of the slits can be easily corrected.

Also, an optical filter wheel having a plurality of narrow band filters provided around a disk, a drive unit for rotating the optical filter wheel, and the optical filter wheel being driven by the drive unit. An encoder wheel that is simultaneously driven to rotate and has a slit around it, a detection unit that detects the slit, and a drive signal that rotates the optical filter wheel to stop the plurality of narrow band filters at the same position. In order to solve the above problem, the control unit according to claim 3, wherein the control unit is configured to rotate the control unit at an initial stage. Encoder Dahoy
A storage unit that stores a drive signal to the drive unit when a slit signal that has detected the slit of the nozzle is output from the detection unit as a drive signal corresponding to the slit, and the slit and the drive corresponding to the slit when used. An optical filter wheel driving device that determines the position of the optical filter wheel by a signal.

Therefore, the problem can be easily solved by storing the signal pattern of the drive signal corresponding to the slit in the storage section with the conventional manufacturing method, so that the cost is greatly increased. In addition, there is no need for large capital investment that involves the improvement of technology in the manufacturing process. The drive signal pattern of the storage unit can be read and confirmed each time the slit is detected. Alternatively, a rough position is determined by detecting the slit, and finally the slit is read from the storage unit. In some cases, control is performed such that a drive signal pattern corresponding to the above is read out and the drive signal is output.

According to the present invention, the control section compares the drive signal when the detecting section detects the slit during use with the stored drive signal, and issues a stored drive signal if different from each other to determine the fixed position. Of the optical filter wheel. With this configuration, it is possible to immediately determine whether the drive signal corresponding to the slit is correct by a simple means of comparing signals in the control unit, and to issue a correct drive signal and correct the drive signal to a correct position. This is completely independent of the manufacturing technology in the manufacturing process.

According to the fifth aspect, the drive unit is a step mode.
With this configuration, the signal pattern of the drive signal can be easily recognized, and the storage of the signal pattern in the storage unit becomes extremely easy.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An optical filter wheel according to the present invention.
The drive device 1 of the wheel will be described with reference to FIG. As shown in FIG. 1, a disc-shaped optical filter wheel 2 is provided with a plurality of narrow band filters 4 having different passing wavelengths around a wheel 3. Step motor 5 as drive unit
The center of the optical filter wheel 2 is rotatably provided by a drive shaft 6 of a step motor 5.

Further, an encoder wheel having a slit portion 8 (origin portion) is provided on the drive shaft 7 of the step motor 5.
The optical filter wheel 2 and the encoder wheel 9 are simultaneously driven to rotate in the same direction. On the circumferential side of the encoder wheel 9, a detection unit 10 such as a photosensor for detecting the slit 8 is disposed.

The narrow band filter 4a located on the optical axis 11
Light from a light source 12 such as a halogen lamp or the like, and is converted into light of a specific wavelength by a narrow band filter 4a. Light enters 14. In the measurement cell 13, the amount of transmitted light increases or decreases depending on the number of component molecules resonating at the specific wavelength. The light transmitted through the transmission side window 15 of the measurement cell 13 in this manner is measured by the photodetector 16. Absorbance is calculated from the measured light quantity, and a specific component of the measured object is calculated by using the plurality of absorbances obtained in this way and a calculation formula created in advance.

In the present invention, the optical filter wheel 2
Is controlled by the control device 17. The control device 17 includes a control unit 18 and a drive control unit 19, and controls the step mode.
The drive of the rotation of the motor 5 is controlled. Further, a storage unit 20 is provided for storing a signal pattern of a drive signal output by the drive control unit 19 to drive and control the step motor 5. The storage unit 20 stores the detection unit 10 at the beginning of the operation of the apparatus.
This stores the signal pattern of the drive signal output from the drive control section 19 when the slit section 8 of the encoder wheel 9 is detected.

Therefore, in the present invention, the detecting section 10 detects the slit section 8 of the encoder wheel 9, and corresponds to the signal pattern of the driving signal at that time and the slit section 8 stored in the storage section 20. The control unit 18 transmits the signal pattern
Are used to determine the drive position by comparison. At this time,
If the drive signal pattern of the drive control section 19 when the slit section 8 is detected matches the signal pattern of the storage section 20, the control section 18 determines that the position determined by the slit section 8 is accurate. Judge, and if they do not match, judge that there is deviation. If the position determined here is the origin position, only one slit may be used, and if this origin is not changed, the positions of the plurality of narrow band filters do not change. The drive control section 19 may send a drive signal to the step motor 5 at a predetermined step centering on the origin position.

In addition to the above, the slit detection is merely used as a guide, and the stored signal pattern is read out each time, and the drive signal based on the signal pattern is supplied to the drive control unit 19.
It is also possible to emit from. In this case, it is preferable to provide a slit for each of the narrow band filters as shown in FIG. 3, instead of providing the slit only as the origin.

[0024]

FIG. 2 and FIG. The step motor 5 switches the current flowing through a plurality of motor windings in order, thereby changing the angle per one step and the motor.
Although the characteristics of the data change, the following description is based on the assumption that the following specifications are satisfied. ｛Specifications｝ Step: 400 steps (0.9 degrees per step) Excitation method: 1-2-phase excitation method When the photosensor 10 detects the slit section 8 at the position P2 in FIG. The excitation state of the step motor 5 is set to four positions in FIG. The excitation pattern (two-phase excitation) at this time is stored in the storage unit 20.

After the second use or during use,
If the control unit 18 matches the excitation pattern of the step motor 5 at the position P2 in FIG. 6B with the excitation pattern of the storage unit 20 stored corresponding to that position, it is determined at the initial stage. It can be determined that there is no threading at the position.

If the positional relationship between the encoder wheel 9 and another position is shifted as shown in FIG.
At one position, the photo sensor 10 detects the slit portion 8, and the excitation pattern of the step motor 5 here is the signal pattern immediately before the excitation pattern stored in the storage unit 20, The control unit 18 can judge that the position is different from the position determined by the signal pattern at the initial stage. Further, according to the present invention, the control unit 18 advances one control excitation step in accordance with a command from the control unit 18, that is, the storage unit 20 By using the stored excitation pattern, the original origin position can be corrected.

Since such a deviation is about one step, even if the excitation method changes and the angle of one step changes, if the change of the encoder wheel is, for example, within a range of several steps, this driving method can always be used. It is possible to regain the fixed position.

[0028]

According to the present invention, even if the initial fixed position of the optical filter wheel shifts due to a change in the environmental temperature or the aging of the equipment, it is possible not only to reliably detect the shift but also to surely recover the initial position. it can.

In addition, these can be implemented not only by a very simple means of providing a storage unit for storing the excitation pattern but also comparing the excitation patterns, and also by adjusting the position of the slit portion even when manufacturing the apparatus. For this reason, it is possible to manufacture the device at low cost without using an expensive adjustment tool or manufacturing method, so that the stability of the product is improved and the product does not vary.

When the driving section is constituted by a step motor, the rotational position and the excitation pattern of the step motor coincide with each other, so that the driving according to the present invention can be performed very easily.

[Brief description of the drawings]

FIG. 1 is a perspective view showing a driving device of an optical filter wheel according to the present invention.

FIG. 2 is a diagram showing an excitation pattern of a step motor.

FIG. 3 is another example of an encoder wheel.

FIG. 4 is a perspective view showing a driving device of a conventional optical filter wheel.

FIG. 5 is a view showing an encoder wheel of a conventional optical filter wheel driving device.

FIG. 6 is a diagram showing a positional relationship between a photosensor and an encoder foil.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 drive device for optical filter wheel 2 optical filter wheel 3 wheel 4 narrow band filter 5 step motor 6 drive shaft 7 drive shaft 8 slit section 9 encoder wheel 10 detection section 11 optical axis 12 light source Reference Signs List 13 measurement cell 14 measurement window 15 transmission side window 16 photodetector 17 control device 18 control unit 19 drive control unit 20 storage unit 50 optical filter wheel drive device 51 optical filter wheel 52 wheel 53 narrow band filter 54 Step motor 55 Drive shaft 56 Drive shaft 57 Encoder wheel 58 Light source 59 Measurement cell 60 Light receiving element 61 Controller 62 Drive controller 63 Photosensor detector 64 Slit 64

Claims (5)

[Claims] An optical filter wheel provided with a plurality of narrow band filters for passing light of a specific wavelength out of light emitted from a light source, wherein the optical filter wheel is rotated by driving means. A method for driving an optical filter wheel that switches a wavelength of light to be irradiated on an object to be measured by switching a plurality of narrow band filters with respect to a light source. A slit provided in a rotating encoder wheel and a drive signal pattern instructed by a drive unit when the slit is detected are stored, and when the optical filter wheel is set for use during use, A position of the optical filter wheel is determined by a slit and a driving signal pattern corresponding to the slit. 2. A driving signal pattern when a detecting section detects a slit during use is compared with the stored driving signal pattern. If the driving signal pattern is different, the stored driving signal pattern is issued. A method of driving an optical filter wheel, wherein the driving method is a fixed position. 3. An optical filter wheel provided with a plurality of narrow band filters around a disk, and said optical filter wheel.
A driving unit for rotating the wheel, an encoder wheel which is driven to rotate simultaneously with the optical filter wheel by the driving unit and has a slit around the driving unit, a detecting unit for detecting the slit, and the optical filter wheel. A driving signal for rotating the wheels to stop the plurality of narrow band filters at the same position to a driving unit, and a control unit to which the detection unit is connected, the driving device for an optical filter wheel. The control unit stores a drive signal pattern to the drive unit when a slit signal that detects the slit of the rotating encoder wheel is output from the detection unit as a drive signal corresponding to the slit at an initial stage. The position of the optical filter wheel is determined by the slit detected at the time of use and the drive signal pattern corresponding to the slit. For driving an optical filter wheel. 4. The control section compares a drive signal pattern when the detecting section detects a slit during use with the stored drive signal pattern. If the drive signal pattern is different, the control section stores the stored drive signal pattern. A driving device for an optical filter wheel, wherein the driving device emits a laser beam to a fixed position. 5. The driving device for an optical filter wheel according to claim 4, wherein the driving unit is a step motor.