JP2755885B2 - 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 the detection of 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.

[0002]

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.

[0003]

However, in the above-described conventional method of detecting the position of the light beam incident on the CCD, the configuration is complicated when the differentiation processing is realized by hardware.
In addition, there are disadvantages that it is expensive and that if it is realized by software, it takes a long processing time and does not fall within the allowable time of the system.

An object of the present invention is to reduce noise or noise when the beam spot of a light beam incident on a CCD image sensor extends over a plurality of pixels and it is necessary to determine the intensity center position with at least unit pixel pixel precision. 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 accurately obtained regardless of the existence of other error factors.

[0005]

According to a first aspect of the present invention, there is provided a method for detecting the position of a light beam incident on a CCD according to the present invention. A unit of product of an intensity data group and an intensity distribution coefficient group obtained by making the parallel light beam or the convergent light beam incident on the CCD image sensor by generating an intensity distribution coefficient group in which data is normalized is defined as a unit. A maximum value obtained by calculating and deriving while shifting only the pixel is obtained, and a position indicating the maximum intensity of the incident light beam onto the CCD image sensor is located in a region configured by the pixel group having the maximum value. The point is that it is determined as a position corresponding to the maximum intensity position of the intensity distribution coefficient group. The second characteristic configuration is CC
A plurality of sets of intensity distribution coefficients obtained by normalizing the intensity data obtained by causing the reference light beam to enter the D image sensor in correspondence with 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 and the intensity distribution coefficient group obtained by irradiating the parallel ray bundle or the convergent ray bundle to the sensor while shifting the unit pixel by the unit pixel, Obtained for each intensity distribution coefficient, the position indicating the maximum intensity of the light beam incident on the CCD image sensor is set to the maximum value among the maximum values among the plurality of regions including the pixel group having the maximum value. Is obtained as a position corresponding to the maximum intensity position of the intensity distribution coefficient group having the value of.

[0006]

According to the first feature configuration, first, intensity data obtained by causing a reference light beam not containing an error component such as noise to be incident on a CCD image sensor is normalized to generate an intensity distribution coefficient group. The number of data constituting the intensity distribution coefficient group corresponds to the number of pixels covered by the reference light beam to the CCD.
Next, the product sum of the intensity data obtained when the light beam to be measured is made incident and the intensity distribution coefficient group is calculated and derived while shifting by the unit pixel. In other words, the process of deriving the product sum by associating the intensity data and the intensity distribution coefficient group sequentially output from the CCD by the number of data constituting the intensity distribution coefficient group is performed while shifting the output by unit pixels. Perform on data. As a result, it is determined that the maximum intensity position of the incident light beam is present in a region composed of a pixel group in which the sum of products has a maximum value, that is, in a region having the strongest correlation with the intensity distribution coefficient group. The position corresponding to the maximum intensity position in the intensity distribution coefficient group is specified as a position indicating the maximum intensity of the light beam incident on the CCD image sensor.

According to the second characteristic configuration, the same processing as described above is performed on a plurality of sets of intensity distribution coefficient groups generated corresponding to different positions in the unit pixel pitch of the CCD image sensor. Then, comparing the local maximum value of each intensity distribution coefficient group, it is determined that the maximum intensity position of the incident light flux is present in a region formed by a pixel group in which the sum of products is maximum, and the intensity distribution coefficient group A position corresponding to the maximum intensity position is specified as a position indicating the maximum intensity of the light beam incident on the CCD image sensor. That is,
When generating two types of intensity distribution coefficient groups, the CC
When the position indicating the maximum intensity of the incident light beam onto the D image sensor is determined with an accuracy of の of the unit pixel interval, and n types of intensity distribution coefficient groups are generated, the position before the CCD image sensor is detected. The position indicating the maximum intensity of the incident light beam is determined with an accuracy of 1 / n of the unit pixel interval.

[0008]

According to the present invention, when the beam spot of the light beam incident on the CCD image sensor covers a plurality of pixels, the intensity center position is obtained by using all of the information, and at least the unit is determined. It is possible to provide a method of detecting the position of a light beam incident on a CCD that can accurately determine the center position of the intensity with the accuracy of the pixel interval regardless of the presence of noise or other error factors.

[0009]

Embodiments will be described below. As shown in FIGS. 5 and 6, 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 normalized 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 summing a product sum 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.

Similarly, a process of calculating and summing 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 maximum values of the respective intensity distribution coefficient groups are input to the data processor DSP, and it is determined that the maximum intensity position of the incident light beam exists in a region constituted by the pixel group in which the sum of products is maximized, and the intensity is determined. A position corresponding to the maximum intensity position of the distribution coefficient group is specified as a position indicating the maximum intensity of the light beam incident on the CCD image sensor based on the data of the pixel position detection circuits C6, C7, C6 ', and C7'. At the same time, the luminance corresponding to the pixel position is
4, C5, C4 ', and C5'. As described above, the position indicating the maximum intensity of the light beam incident on the CCD image sensor 8 is obtained with an accuracy of １ ／ of the unit pixel interval.

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 previous embodiment, the case where the intensity distribution coefficient group is constituted by m coefficient data has been described, but the value of m is not particularly limited. In the previous embodiment, the case where two types of intensity distribution coefficient groups were used was described. However, the present invention is not limited to this, and n types of intensity distribution coefficient groups obtained by changing the intensity center position between unit pixels are used. Is used, the position indicating the maximum intensity of the light beam incident on the CCD image sensor 8 can be obtained with an accuracy of 1 / n of the unit pixel interval. The arithmetic processing circuit used in the previous embodiment is not limited to this,
It can be appropriately configured using a known technique. In the above embodiment, each coefficient of the intensity distribution coefficient group is set to have a Gaussian distribution according to the light source (laser) used. However, each coefficient of the intensity distribution coefficient group is appropriately determined according to the type of the light source used and the like. Just set it. 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 a principle diagram of a three-dimensional digitizer.

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

[Explanation of symbols]

 8 CCD image sensor

Continuation of front page (56) References JP-A-3-27477 (JP, A) JP-A-62-22004 (JP, A) JP-A-63-293427 (JP, A) JP-A-61-196104 (JP) , A) JP-A-6-221811 (JP, A) JP-A-2-74811 (JP, A) (58) Fields investigated (Int. Cl. ⁶ , DB name) G01C 3/06 G01B 11/00

Claims (2)

(57) [Claims] 1. A parallel light beam or a convergent light beam is transferred to a CCD.
What is claimed is: 1. A method for detecting the position of a light beam incident on a CCD, the method comprising: detecting a position of a light beam having a maximum intensity when the light beam is incident on an image sensor; And generating an intensity distribution coefficient group obtained by normalizing the intensity data obtained by performing the above operation, and an intensity data group obtained by causing the parallel light beam or the convergent light beam to enter the CCD image sensor (8) and the intensity distribution coefficient. The maximum value obtained by calculating and deriving the sum of products with the group by the unit pixel is obtained, and the position indicating the maximum intensity of the light beam incident on the CCD image sensor (8) is taken as the maximum value. A method for detecting the position of a light beam incident on a CCD, which is determined as a position corresponding to the maximum intensity position of the intensity distribution coefficient group in a region constituted by pixel groups. 2. A parallel light beam or a convergent light beam is transferred to a CCD.
What is claimed is: 1. A method for detecting the position of a light beam incident on a CCD, the method comprising: detecting a position of a light beam having a maximum intensity when the light beam is incident on an image sensor; A plurality of sets of intensity distribution coefficients obtained by normalizing the intensity data obtained by the above are generated in correspondence with different positions within a unit pixel pitch of the CCD image sensor (8), and the CCD image sensor (8) A maximum value obtained by calculating and deriving a product sum of an intensity data group obtained by injecting a parallel light beam or a convergent light beam and the intensity distribution coefficient group by shifting by a unit pixel, the plurality of intensity distribution coefficients The position indicating the maximum intensity of the light beam incident on the CCD image sensor (8) is determined for each of the plurality of regions including the pixel group having the maximum value. Maximum value position detecting method of the incident light beam to the CCD for obtaining a position corresponding to the maximum intensity position of the intensity distribution coefficient group to take in or.