-----BEGIN PRIVACY-ENHANCED MESSAGE-----
Proc-Type: 2001,MIC-CLEAR
Originator-Name: webmaster@www.sec.gov
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MIC-Info: RSA-MD5,RSA,
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 DZpjJYOPfoR3iMVCljyJ2A==

<SEC-DOCUMENT>0001241491-03-000001.txt : 20030904
<SEC-HEADER>0001241491-03-000001.hdr.sgml : 20030904
<ACCEPTANCE-DATETIME>20030904154648
ACCESSION NUMBER:		0001241491-03-000001
CONFORMED SUBMISSION TYPE:	4
PUBLIC DOCUMENT COUNT:		1
CONFORMED PERIOD OF REPORT:	20030902
FILED AS OF DATE:		20030904

REPORTING-OWNER:	

	OWNER DATA:	
		COMPANY CONFORMED NAME:			RITTENOUR HARRY T
		CENTRAL INDEX KEY:			0001241491

	FILING VALUES:
		FORM TYPE:		4
		SEC ACT:		1934 Act
		SEC FILE NUMBER:	000-20206
		FILM NUMBER:		03881591

	BUSINESS ADDRESS:	
		STREET 1:		47827 HALYARD DR
		CITY:			PLYMOUTH
		STATE:			MI
		ZIP:			48170
		BUSINESS PHONE:		7344144810

ISSUER:		

	COMPANY DATA:	
		COMPANY CONFORMED NAME:			PERCEPTRON INC/MI
		CENTRAL INDEX KEY:			0000887226
		STANDARD INDUSTRIAL CLASSIFICATION:	OPTICAL INSTRUMENTS & LENSES [3827]
		IRS NUMBER:				382381442
		STATE OF INCORPORATION:			MI
		FISCAL YEAR END:			0630

	BUSINESS ADDRESS:	
		STREET 1:		47827 HALYARD DRIVE
		CITY:			PLYMOUTH
		STATE:			MI
		ZIP:			48170-2461
		BUSINESS PHONE:		3134144816

	MAIL ADDRESS:	
		STREET 1:		47827 HALYARD DRIVE
		CITY:			PLYMOUTH
		STATE:			MI
		ZIP:			48170-2461
</SEC-HEADER>
<DOCUMENT>
<TYPE>4
<SEQUENCE>1
<FILENAME>primary_doc.xml
<DESCRIPTION>PRIMARY DOCUMENT
<TEXT>
<XML>
<?xml version="1.0"?>

<ownershipDocument>

    <schemaVersion>X0201</schemaVersion>

    <documentType>4</documentType>

    <periodOfReport>2003-09-02</periodOfReport>


    <notSubjectToSection16>0</notSubjectToSection16>

    <issuer>
        <issuerCik>0000887226</issuerCik>
        <issuerName>PERCEPTRON INC/MI</issuerName>
        <issuerTradingSymbol>prcp</issuerTradingSymbol>
    </issuer>

    <reportingOwner>
        <reportingOwnerId>
            <rptOwnerCik>0001241491</rptOwnerCik>
            <rptOwnerName>RITTENOUR HARRY T</rptOwnerName>
        </reportingOwnerId>
        <reportingOwnerAddress>
            <rptOwnerStreet1>47827 HALYARD DRIVE</rptOwnerStreet1>
            <rptOwnerStreet2></rptOwnerStreet2>
            <rptOwnerCity>PLYMOUTH</rptOwnerCity>
            <rptOwnerState>MI</rptOwnerState>
            <rptOwnerZipCode>48170</rptOwnerZipCode>
            <rptOwnerStateDescription></rptOwnerStateDescription>
        </reportingOwnerAddress>
        <reportingOwnerRelationship>
            <isDirector>0</isDirector>
            <isOfficer>1</isOfficer>
            <isTenPercentOwner>0</isTenPercentOwner>
            <isOther>0</isOther>
            <officerTitle>Senior Vice President</officerTitle>
        </reportingOwnerRelationship>
    </reportingOwner>

    <derivativeTable>

        <derivativeTransaction>
            <securityTitle>
                <value>Employee Stock Option (Right to Buy)</value>
            </securityTitle>
            <conversionOrExercisePrice>
                <value>6.5</value>
            </conversionOrExercisePrice>
            <transactionDate>
                <value>2003-09-02</value>
            </transactionDate>
            <transactionCoding>
                <transactionFormType>4</transactionFormType>
                <transactionCode>A</transactionCode>
                <equitySwapInvolved>0</equitySwapInvolved>
            </transactionCoding>
            <transactionTimeliness>
                <value></value>
            </transactionTimeliness>
            <transactionAmounts>
                <transactionShares>
                    <value>30000</value>
                </transactionShares>
                <transactionPricePerShare>
                    <value>0</value>
                </transactionPricePerShare>
                <transactionAcquiredDisposedCode>
                    <value>A</value>
                </transactionAcquiredDisposedCode>
            </transactionAmounts>
            <exerciseDate>
                <footnoteId id="F1"/>
            </exerciseDate>
            <expirationDate>
                <value>2013-09-01</value>
            </expirationDate>
            <underlyingSecurity>
                <underlyingSecurityTitle>
                    <value>Common Stock</value>
                </underlyingSecurityTitle>
                <underlyingSecurityShares>
                    <value>30000</value>
                </underlyingSecurityShares>
            </underlyingSecurity>
            <postTransactionAmounts>
                <sharesOwnedFollowingTransaction>
                    <value>30000</value>
                </sharesOwnedFollowingTransaction>
            </postTransactionAmounts>
            <ownershipNature>
                <directOrIndirectOwnership>
                    <value>D</value>
                </directOrIndirectOwnership>
            </ownershipNature>
        </derivativeTransaction>

    </derivativeTable>

    <footnotes>
        <footnote id="F1">On September 2, 2003, the reporting person was granted an option to purchase 30,000 shares of Common Stock (ISO) under the 1992 Stock Option Plan, an exempt plan under the rule 16b-3.  The shares are exercisable as follows:  7,500 shares exercisable on 9/2/2004, 7,500 shares exercisable on 9/2/2005, 7,500 shares exercisable on 9/2/2006 and 7,500 shares exercisable on 9/2/2007.</footnote>
    </footnotes>


    <ownerSignature>
        <signatureName>Harry T. Rittenour</signatureName>
        <signatureDate>2003-09-04</signatureDate>
    </ownerSignature>

</ownershipDocument>

</XML>
</TEXT>
</DOCUMENT>
</SEC-DOCUMENT>
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