JP2851227B2 - Method for detecting the position of a light beam incident on a CCD - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the position of a light beam incident on a CCD, which detects a position where a parallel light beam or a convergent light beam is incident on a CCD image sensor, and detects the position of the maximum intensity of the incident light beam. For example, a tertiary method for measuring the distance of the object from the reference surface by irradiating the object placed on the reference surface with a laser beam and detecting the reflected light beam with a CCD image sensor. The present invention relates to a method for detecting the position of a light beam incident on a CCD used in an original digitizer or the like.

2. Description of the Related Art Generally, the intensity center position of a parallel light beam or a convergent light beam incident on a CCD image sensor is represented by C
When it is necessary to obtain at least the unit pixel interval accuracy based on the output data of the CD image sensor, the CCD
If the intensity distribution of the incident light beam on a plurality of pixels, a problem arises as to which pixel position should be specified as the intensity center position. For example, in the case of the above-described three-dimensional digitizer, the beam spot of the incident light beam on the CCD image sensor usually covers a plurality of pixels, and the influence of each inclination of the surface of the measurement object with respect to the reference plane, the surface color, and noise. In consideration of the above, it is extremely dangerous to simply set the maximum output position of the CCD as the intensity center position of the beam spot. Therefore, conventionally, there has been proposed a method of differentiating output data obtained by removing noise from a CCD output by filtering, and specifying a position having a maximum value as an intensity center position.

[0002]

The conventional CCD described above.
In the method of detecting the position of the light beam incident on the light source, when the differentiation processing is realized by hardware, the configuration is complicated, and
There are disadvantages that it is expensive, and that if it is realized by software, it takes a long processing time and does not fit within the permissible time of the system. Therefore, the applicant of the present application first generates an intensity distribution coefficient group in which intensity data obtained by irradiating a reference light beam to a CCD image sensor is normalized, and outputs the parallel light beam or the convergent light beam to the CCD image sensor. The maximum value obtained by calculating and deriving the product sum of the intensity data group obtained by injecting the bundle and the intensity distribution coefficient group while shifting the unit pixel is obtained, and calculating the maximum value of the incident light beam onto the CCD image sensor. The position showing the maximum intensity, of the region composed of the pixel group having the maximum value,
A method of finding the position corresponding to the maximum intensity position of the intensity distribution coefficient group has been proposed (Japanese Patent Application No. 4-316974).
issue).

In the above-described method, when it is necessary to determine the maximum intensity position of the incident light beam with a finer precision than the unit pixel pitch of the CCD image sensor, the intensity distribution coefficient group differs within the unit pixel pitch. A plurality of sets are generated corresponding to the positions, and the product sum of the intensity data group obtained by irradiating the measurement light beam onto the CCD image sensor and the intensity distribution coefficient group is calculated and derived while shifting by the unit pixel. The local maximum value is determined for each of the plurality of intensity distribution coefficients, and the position indicating the maximum intensity of the incident light beam on the CCD image sensor is determined, among a plurality of regions including the pixel group having the local maximum value, It is determined as a position corresponding to the maximum intensity position of the intensity distribution coefficient group having the maximum value among the maximum values. In this case, the unit pixel pitch of 1
In order to specify the position indicating the maximum intensity of the incident light beam with an accuracy of / n, it is necessary to generate n intensity distribution coefficient groups and perform the above-described arithmetic processing. However, the number of circuits increases, the size of the substrate is increased, a large accommodation space for the device is required, and there is a drawback that economy is low. The arithmetic processing circuit for at least one intensity distribution coefficient group If the software is used to repeatedly use the arithmetic processing circuit for a plurality of intensity distribution coefficient groups with a time lag, the processing speed becomes slow and cannot be put to practical use.

An object of the present invention is to reduce the burden on hardware and software when the beam spot of a light beam incident on a CCD image sensor covers a plurality of pixels, and to set the intensity center position at a unit pixel interval or more. An object of the present invention is to provide a method for detecting the position of a light beam incident on a CCD which can be obtained with high accuracy.

[0005]

In order to achieve this object, a feature of the method for detecting the position of a light beam incident on a CCD according to the present invention is that the intensity data obtained by making a reference light beam incident on a CCD image sensor is normalized. Generated 2n sets (n is a positive integer) corresponding to different positions within the unit pixel pitch of the CCD image sensor,
The maximum value obtained by calculating and deriving the product sum of the intensity data group obtained by irradiating the measuring light beam onto the CCD image sensor and the intensity distribution coefficient group by shifting the unit pixel by the unit pixel is calculated as the intensity of the 2n sets. Obtained for each distribution coefficient,
A position indicating the maximum intensity of the incident light beam onto the CD image sensor is defined as the maximum value, and a pixel position corresponding to the maximum intensity position of each intensity distribution coefficient group in a region formed of the pixel group having the maximum value. Is specified with an accuracy of 1 / (4n) of the unit pixel pitch.

[0006]

In this embodiment, 2n intensity distribution coefficient groups are generated, and a product sum of the intensity distribution coefficient groups and a maximum intensity position of each intensity distribution coefficient group in a region constituted by a pixel group that takes a maximum sum of products. If the hardware or software for obtaining the pixel position corresponding to is provided, the CCD image is located between the intensity distribution coefficient group that takes the maximum sum of products or the adjacent intensity distribution coefficient group among the maximum sum of products obtained by the hardware or software. The position at which the maximum intensity of the light beam incident on the sensor is indicated can be specified.

[0007]

According to the present invention, when the beam spot of a light beam incident on a CCD image sensor extends over a plurality of pixels, the intensity center position is reduced by a unit pixel interval while reducing the load on hardware and software. With the above accuracy,
It has become possible to provide a method for detecting the position of a light beam incident on a CCD, which can be obtained at high speed and economically.

[0008]

Embodiments will be described below. As shown in FIGS. 6 and 7, the three-dimensional digitizer converts the measurement light beam from the light source 1 composed of a laser oscillator into a rotating mirror 4 and a fixed mirror 5.
Object 3 placed on XY reference plane 2 via
, And the scattered light beam from the surface of the measuring object 3 is input to the one-dimensional CCD image sensor 8 via the fixed mirror 6, the rotating mirror 4, and the light collecting optical system 7.
Measure the distance Z ₀ from the Y reference plane 2 to the surface of the measuring object 3. That is, the distance between the detection position X ₀ of the light beam scattered from the XY reference plane 2 and the detection position X ₁ of the scattered light beam from the surface of the measurement target 3 is the X of the measurement light beam. The distance is calculated by using a relationship that is proportional to the distance ΔX ₀ between the incident position on the Y reference plane 2 and the position of the incident position on the surface of the measurement target 3 on the XY reference plane 2. it is determine the Z _0.

A method for detecting the position of the light beam incident on the one-dimensional CCD image sensor 8 will be described below. As shown in FIGS. 2 and 3, the light beam incident on the one-dimensional CCD image sensor 8 is distributed in a substantially circular shape on the sensor 8, but since the light source 1 uses a laser oscillator, its intensity distribution is Gaussian. Distribution. Now, when the reference light beam from which error factors such as noise have been removed is made incident on the sensor 8, the output distribution of the sensor 8 has a value equal to the discrete data of the Gaussian distribution. As shown in FIG. 2, discrete data obtained when the maximum intensity position of the reference light beam is adjusted to the center position of an arbitrary pixel of the CCD image sensor 8 and the incident light is normalized by the maximum intensity of the reference light beam. M obtained
Is generated as a first intensity distribution coefficient group.
As shown in FIG. 3, the maximum intensity position of the reference light beam is
The m pieces of coefficient data obtained by normalizing the discrete data obtained when the light is incident on the boundary position of an arbitrary pixel of the CD image sensor 8 with the maximum intensity of the reference light beam are also used as a second intensity distribution coefficient group. Generate as

On the other hand, when a scattered light beam from the surface of the measuring object 3 is made incident on the one-dimensional CCD image sensor 8 via the fixed mirror 6, the rotating mirror 4, and the light collecting optical system 7, FIG. As shown in FIG. 4, the intensity data output from the sensor 8 is represented so as to have a peak value in an area composed of a plurality of pixels among the 512 constituent pixels.

A process for calculating and deriving a sum of products by associating the intensity data sequentially output from the sensor 8 with the first intensity distribution coefficient group by the number of data constituting the first intensity distribution coefficient group, The process is executed for all output data while shifting by the unit pixel. As a result, it is determined that the maximum intensity position of the incident light flux exists in the first region including the pixel group in which the sum of products has the maximum value. That is, as shown in FIG. 1, the intensity data (d
, D2,...) To the first intensity distribution coefficient group (s
1, s2,..., Sm) are stored.
1 and the sum of products is calculated as follows. d1 · s1 + d2 · s2 + ... + dm · sm d2 · s1 + d3 · s2 + ... + d (m + 1) · sm ... ............ The current product sum is compared with the previous product sum stored in the latch circuit C3 by the comparator circuit C2, and only when the current product sum is large, The calculation of storing the sum of the products in the latch circuit C3 is performed for all the pixels of the sensor 8. The operation data having the maximum value in the sum of the products remains in the latch circuit C3 as data having the strongest correlation with the first intensity distribution coefficient group. At this time, data indicating a pixel position corresponding to the sum of products stored in the latch circuit C3 and corresponding to the maximum coefficient value of the first intensity distribution coefficient group is latched via the counter circuit C6. C7 and the luminance data at that time are stored in the latch circuit C5 via the shift register C4.

A process for calculating and deriving a product sum by associating the intensity data sequentially output from the sensor 8 with the second intensity distribution coefficient group by the number of data constituting the second intensity distribution coefficient group. Is performed for all output data while shifting by unit pixels. As a result, it is determined that the maximum intensity position of the incident light beam exists in the second region including the pixel group in which the sum of products has the maximum value. The calculation method is the same as described above.

The data of the latch circuits C3 and C3 ', that is,
The local maximum value of each intensity distribution coefficient group, and latch circuits C7 and C7 '
, I.e., the pixel position corresponding to the maximum intensity position of each intensity distribution coefficient group is input to the data processor DSP, and the maximum intensity position of the incident light beam is specified as follows. That is, the maximum value of the product sum of the first intensity distribution coefficient group is V1, and the pixel position corresponding to the maximum intensity position is P1.
Assuming that the maximum value of the product sum of the second intensity distribution coefficient group is V2 and the pixel position corresponding to the maximum intensity position is P2, and the unit pixel pitch of the sensor 8 is divided into four, as shown in FIG. , The maximum intensity position P of the incident light beam is V1> V
2, if P1 = P2, the range is 0.00 ≦ P <0.25; if V1 <V2, P1 = P2, 0.25 ≦ P
<0.50, V1> V2, P1 = P2 + 1
Then, the range is -0.25 ≦ P <0.00, and V1 <
If V2, P1 = P2 + 1, -0.5≤P <-0.2
5 can be determined. That is, the position indicating the maximum intensity of the light beam incident on the CCD image sensor 8 is defined as 2
It is possible to specify from the set of intensity distribution coefficient groups with an accuracy of 1/4 of the unit pixel pitch.

Another embodiment will be described below. In the above embodiment, the CCD image sensor having 512 pixels has been described, but the present invention is not limited to this.

In the above embodiment, the case where the intensity distribution coefficient group is constituted by m pieces of coefficient data has been described, but the value of m is not particularly limited.

In the above embodiment, the case where two types of intensity distribution coefficient groups are used has been described. However, the present invention is not limited to this case.
When n (n is a positive integer) kinds of intensity distribution coefficient groups are used, the position indicating the maximum intensity of the light beam incident on the CCD image sensor 8 is obtained with an accuracy of 1 / (4n) of the unit pixel interval. . Details will be described below. Now, as shown in FIG. 8, 2n number of intensity distribution coefficient groups S1, S2,... Obtained by injecting a reference light beam with a unit pixel length d at a pitch of 1 / (2n).
, S2n are generated. Assuming that the maximum pixel position of the intensity distribution coefficient group Si that takes the maximum value among the maximum values of the sum of products of the respective intensity distribution coefficient groups is Pi, the position P indicating the true maximum intensity of the incident light beam is Pi − (l / 2) ≦ P <Pi + (l / 2). However, 1 = d / (2n). Next, the pixel position specified by the intensity distribution coefficient group Si having the maximum value among the maximum values of the product sum of the intensity distribution coefficient group is represented by Q
i, the pixel position specified by the intensity distribution coefficient group Sj corresponding to the position shifted from the intensity distribution coefficient group Si by d / 2 is Q
j, when i <j, if Qi = Qj, Pi
.Ltoreq.P <Pi + l / 2, if Qi = Qj-1, Pi-l / 2.ltoreq.P <Pi, i> j, if Qi = Qj, Pi-l / 2 ≦ P <Pi, and if Qi = Qj + 1, then Pi ≦ P <Pi + 1
/ 2 range. That is, the position indicating the maximum intensity of the light beam incident on the CCD image sensor 8 is defined as 2
From the n sets of intensity distribution coefficient groups, 1 / (4
It can be specified with the accuracy of n).

The arithmetic processing circuit used in the above embodiment is not limited to this, and can be appropriately configured using a known technique.

In the above embodiment, each coefficient of the group of intensity distribution coefficients is set so as to have a Gaussian distribution according to the light source (laser) used. Etc. may be set as appropriate. The light beam incident on the sensor 8 can be applied to either a parallel light beam or a convergent light beam.

In the claims, reference numerals are provided for convenience of comparison with the drawings, but the present invention is not limited to the configuration shown in the attached drawings.

[Brief description of the drawings]

FIG. 1 is a block diagram of an arithmetic processing unit.

FIG. 2 is an explanatory diagram showing a first intensity distribution coefficient group.

FIG. 3 is an explanatory diagram showing a second intensity distribution coefficient group.

FIG. 4 is an output diagram of a CCD image sensor with respect to an incident light beam.

FIG. 5 is an explanatory view of a main part.

FIG. 6 is a block diagram of a three-dimensional digitizer.

FIG. 7 is a principle diagram of a three-dimensional digitizer.

FIG. 8 is an explanatory view of a main part showing another embodiment.

[Explanation of symbols]

 8 CCD image sensor

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification symbol FI G01J 1/42 G01J 1/42 E 1/44 1/44 P G06T 7/00 G06F 15/70 460D (56) References JP JP-A-6-160084 (JP, A) JP-A-2-179405 (JP, A) JP-A-63-317703 (JP, A) JP-A-63-293427 (JP, A) (58) Fields investigated (Int) .Cl. ⁶ , DB name) G01B 11/00 11/30 G01C 3/00-3/32 G01J 1/00-1/60 G06T 7/00

Claims (1)

(57) [Claims] An intensity distribution coefficient group obtained by normalizing intensity data obtained by making a reference light beam incident on a CCD image sensor corresponds to different positions within a unit pixel pitch of the CCD image sensor. Then, 2n sets (n is a positive integer) are generated, and the product sum of the intensity data group and the intensity distribution coefficient group obtained by irradiating the measuring light beam to the CCD image sensor (8) is expressed by a unit pixel. A maximum value obtained by calculating and deriving while shifting is obtained for each of the 2n sets of intensity distribution coefficients, and a position indicating the maximum intensity of the light beam incident on the CCD image sensor (8) is defined as the maximum value, Based on a combination with a pixel position corresponding to the maximum intensity position of each intensity distribution coefficient group in a region composed of the pixel group having the maximum value, the pixel is specified with an accuracy of 1 / (4n) of the unit pixel pitch. C Position detecting method of the incident light beam to the D.